Web-accessible critical limits and critical values for urgent clinician notification

OBJECTIVES

To survey the World Wide Web for critical limits/critical values, assess changes in quantitative low/high thresholds since 1990-93, streamline urgent notification practices, and promote global accessibility.

METHODS

We identified Web-posted lists of critical limits/values at university hospitals. We compared 2023 to 1990-93 archived notification thresholds.

RESULTS

We found critical notification lists for 26 university hospitals. Laboratory disciplines ranged widely (1-10). The median number of tests was 62 (range 21-116); several posted policies. The breadth of listings increased. Statistically significant differences in 2023 vs. 1990 critical limits were observed for blood gas (pO2, pCO2), chemistry (glucose, calcium, magnesium), and hematology (hemoglobin, platelets, PTT, WBC) tests, and for newborn glucose, potassium, pO2, and hematocrit. Twenty hospitals listed ionized calcium critical limits, which have not changed. Fourteen listed troponin (6), troponin I (3), hs-TnI (3), or troponin T (2). Qualitative critical values expanded across disciplines, encompassing anatomic/surgical pathology. Bioterrorism agents were listed frequently, as were contagious pathogens, although only three hospitals listed COVID-19. Only one notification list detailed point-of-care tests. Two children's hospital lists were Web-accessible.

CONCLUSIONS

Urgent notifications should focus on life-threatening conditions. We recommend that hospital staff evaluate changes over the past three decades for clinical impact. Notification lists expanded, especially qualitative tests, suggesting that automation might improve efficiency. Sharing notification lists and policies on the Web will improve accessibility. If not dependent on the limited scope of secondary sources, artificial intelligence could enhance knowledge of urgent notification and critical care practices in the 21st Century.

Investigating Potential Correlations between Calcium Metabolism Biomarkers and Periprocedural Clinical Events in Major Cardiovascular Surgeries: An Exploratory Study

Background: There is emerging but conflicting evidence regarding the association between calcium biomarkers, more specifically ionized calcium and the prognosis of intensive care unit (ICU) postoperative cardiac patients. Methods: Our study investigated the relationship between ionized calcium, vitamin D, and periprocedural clinical events such as cardiac, neurologic and renal complications, major bleeding, vasoactive-inotropic score (VIS), and length of ICU and hospitalization. Results: Our study included 83 consecutive subjects undergoing elective major cardiac surgery requiring cardiopulmonary bypass. The mean age of the participants was 64.9 ± 8.5 years. The majority of procedures comprised isolated CABG (N = 26, 31.3%), aortic valve procedures (N = 26, 31.3%), and mitral valve procedures (N = 12, 14.5%). A difference in calcium levels across all time points (p < 0.001) was observed, with preoperative calcium being directly associated with intraoperative VIS (r = 0.26, p = 0.016). On day 1, calcium levels were inversely associated with the duration of mechanical ventilation (r = -0.30, p = 0.007) and the length of hospital stay (r = -0.22, p = 0.049). At discharge, calcium was inversely associated with length of hospital stay (r = -0.22, p = 0.044). All calcium levels tended to be lower in those who died during the 1-year follow-up (p = 0.054). Preoperative vitamin D levels were significantly higher in those who experienced AKI during hospitalization (median 17.5, IQR 14.5-17.7, versus median 15.3, IQR 15.6-20.5, p = 0.048) Conclusion: Fluctuations in calcium levels and vitamin D may be associated with the clinical course of patients undergoing cardiac surgery. In our study, hypocalcemic patients exhibited a greater severity of illness, as evidenced by elevated VIS scores, and experienced prolonged mechanical ventilation time and hospital stays. Additional larger-scale studies are required to gain a deeper understanding of their impact on cardiac performance and the process of weaning from cardiopulmonary bypass, as well as to distinguish between causal and associative relationships.

Characterization of variables related to high stability of raw cow milk

This research paper analyzes the stability of raw cow milk in the alcohol test and seeks to understand to know the factors that influence milk stability and the occurrence of unstable non-acid milk. Milk samples were collected from the cooling tanks of rural farmers in the state of Paraná twice in summer and twice in winter. The farms were classified according to the production system: pasture with supplementation and feedlot. The following variables were analyzed: stability in the alcohol test, titratable acidity, ionized calcium concentration (iCa), chemical composition of milk, somatic cell count and standard plate count. The results showed that milk stability was greater in winter vs. summer, when the milk contained higher iCa, and in the feedlot vs. pasture system. The Pearson Correlation between variables (ethanol stability, milk composition, iCa, cooling tank temperature, milk volume, number of milking, number of cows milked, fat/protein ratio, distance and travel time) were analyzed. Stability was negatively correlated with iCa concentration and positively with lactose content. Logistic regression of the risk of unstable non-acid milk at 72% alcohol (UNAM72) showed that only iCa and lactose were determinants, while evaluation of the same risk at 78% alcohol revealed iCa, titratable acidity, lactose and milk urea nitrogen as risk factors. Under the dairy farming conditions of Paraná state, the frequency of UNAM72 was low (12.16%) and was higher in summer and in pasture systems with supplementation. In conclusion, in dairy herds bred with high technological level, with adequate nutritional and health management, the frequency of UNAM is low and is related to nutritional management abnd, perhaps, heat stress, factors that alter iCa and lactose levels.

Predictors of blood ionized calcium concentration in sick adult cattle

BACKGROUND

Data on the factors affecting blood ionized calcium concentration (ciCa2+ ) and diagnostic performance of serum total calcium concentration (ctCa) measurements to detect abnormal blood iCa2+ status are lacking in sick adult cattle.

OBJECTIVE

Assess the association of ciCa2+ with venous blood pH, plasma concentrations of chloride (cCl), sodium (cNa), and potassium (cK), and ctCa, and total protein, albumin, and globulin concentrations in sick adult cattle.

ANIMALS

Two-hundred and sixty-five adult cattle (≥1-year-old) with different diseases.

METHODS

Prospective study. Whole blood pH, ciCa2+ , cNa, cK, and cCl were measured using a blood gas and electrolyte analyzer, whereas ctCa, and total protein, and albumin concentrations were determined using an autoanalyzer. The relationship between ciCa2+ and venous blood pH, plasma cCl, cNa, cK, and ctCa, and total protein, albumin, and globulin concentrations was investigated. Sensitivity and specificity were calculated for ctCa for diagnosis of abnormal ciCa2+ .

RESULTS

Sensitivity of ctCa measurements to detect abnormal ciCa2+ was 66.0% whereas specificity of ctCa measurements was 72.3%. Serum total calcium concentration measurements accounted for 42% of adjusted blood ionized calcium (iCa2+ 7.40 ) concentration variance. Plasma cCl, and cK had explanatory power of ciCa2+ 7.40 , accounting for an additional 21% and 9% of the variance, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum tCa measurements failed to accurately predict blood iCa2+ status in ill adult cattle. Serum tCa concentrations and plasma cCl were the strongest predictors of ciCa2+ in sick adult cattle.

Normal Levels of Ionized Calcium Despite Persistent Increase in Total Calcium in a Patient With IgA Paraproteinemia

Approximately half of the calcium in the blood circulates in the ionized, free form; which is critical for cellular function. As a result, its levels are tightly regulated by homeostatic mechanisms dependent on hormones such as PTH, vitamin D, and fibroblast growth factor-23. The other half of the total calcium is in a complex with anions, predominantly albumin. Clinically, the levels of albumin are known to influence the relationship of total calcium to free calcium. However, the relevance of changes in other serum proteins on calcium homeostasis is less appreciated. We present the case of a 70-year-old woman who was followed over 5 years with persistently elevated total calcium levels but with normal ionized calcium levels. Her evaluation was notable for IgA paraprotein, which paralleled her history of elevated total serum calcium. Extensive clinical investigations did not reveal hyperparathyroidism or cancer-mediated hypercalcemia. Additional in vitro analyses comparing the plasma containing the IgA paraprotein against a healthy control revealed that a high-molecular-weight IgA paraprotein in the patient has increased capacity to reduce the amount of free calcium in solution, thus providing a direct mechanistic explanation for the clinical findings.

Heparin Concentration in Evacuated Tubes and Its Effect on pH, Ionized Calcium, Lactate, and Potassium in Venous Blood Gas Analysis

Arterial blood specimens collected in evacuated tubes are unacceptable for blood gas analysis. However, evacuated tubes are routinely used for venous blood-gas analysis. The impact of the blood to heparin ratio on venous blood in evacuated tubes is unclear. Venous blood was drawn into lithium and sodium heparin evacuated tubes that were 1/3 full, ½ full, 2/3 full, and fully filled. Specimens were analyzed for pH, ionized calcium (iCa), lactate, and potassium on a blood-gas analyzer. The results for specimens filled only 1/3 full for lithium and sodium heparin tubes revealed a significant increase in pH and a significant decrease in the iCa. Underfilling the lithium and sodium heparin evacuated tubes did not significantly impact the lactate or potassium results. Venous whole-blood specimens should be filled to at least 2/3 full for accurate pH and iCa results.

Prevalence of hypercalcemia in primary hypoadrenocorticism in dogs: Multicenter, retrospective study

BACKGROUND

Hypoadrenocorticism is an important differential for hypercalcemia. The etiology of hypercalcemia in hypoadrenocorticism in dogs is unclear.

OBJECTIVE

To review the prevalence of hypercalcemia and use statistical models to identify clinical, demographic, and biochemical variables associated with hypercalcemia in dogs with primary hypoadrenocorticism.

ANIMALS

One hundred ten dogs with primary hypoadrenocorticism; 107 with recorded total calcium (TCa), 43 recorded ionized calcium (iCa).

METHODS

Multicenter retrospective observational study at 4 UK referral hospitals. Univariable logistic regression analyses were performed to assess the association between independent variables of signalment, hypoadrenocorticism type (glucocorticoid only deficient hypoadrenocorticism [GHoC] vs glucocorticoid and mineralocorticoid deficient hypoadrenocorticism [GMHoC]), clinicopathological variables and hypercalcemia. Hypercalcemia was defined as elevated TCa, an elevated iCa, or both elevated TCa and iCa (Model 1) or as elevated iCa (Model 2).

RESULTS

Overall prevalence of hypercalcemia was 34.5% (38/110). The odds of hypercalcemia (Model 1) were increased (P < .05) in dogs with GMHoC ([vs GHoC], OR [odds ratio] = 3.86, 95% confidence interval [CI] 1.105-13.463), higher serum creatinine (OR = 1.512, 95% CI 1.041-2.197), and higher serum albumin (OR = 4.187, 95% CI 1.744-10.048). The odds of ionized hypercalcemia (Model 2) were increased (P < .05) with reduced serum potassium concentration (OR = 0.401, 95% CI 0.184-0.876) and younger age (OR = 0.737, 95% CI 0.558-0.974).

CONCLUSIONS AND CLINICAL IMPORTANCE

This study identified several key clinical and biochemical variables associated with hypercalcemia in dogs with primary hypoadrenocorticism. These findings aid understanding of the pathophysiology and etiology of hypercalcemia in dogs with primary hypoadrenocorticism.

Prognostic value of initial routine laboratory blood tests in patients with aneurysmal subarachnoid hemorrhage requiring mechanical ventilation: a retrospective cohort study

Background

Aneurysmal subarachnoid hemorrhage (aSAH) necessitating mechanical ventilation (MV) presents a serious challenge for intensivists. Laboratory blood tests reflect individual physiological and biochemical states, and provide a useful tool for identifying patients with critical condition and stratifying risk levels of death. This study aimed to determine the prognostic role of initial routine laboratory blood tests in these patients.

Methods

This retrospective cohort study included 190 aSAH patients requiring MV in the neurosurgical intensive care unit from December 2019 to March 2022. Follow-up evaluation was performed in May 2022 via routine outpatient appointment or telephone interview. The primary outcomes were death occurring within 7 days after discharge (short-term mortality) or reported at time of follow-up (long-term mortality). Clinico-demographic and radiological characteristics, initial routine laboratory blood tests (e.g., metabolic panels and arterial blood gas analysis), and treatment were analyzed and compared in relation to mortality. Multivariable logistic and Cox regression analyses, with adjustment of other clinical predictors, were performed to determine independent laboratory test predictors for short- and long-term mortality, respectively.

Results

The patients had a median age of 62 years, with a median World Federation of Neurosurgical Societies grade (WFNS) score of 5 and a median modified Fisher grade (mFisher) score of 4. The short- and long-term mortality of this cohort were 60.5% and 65.3%, respectively. Compared with survivors, non-survivors had more severe disease upon admission based on neurological status and imaging features and a shorter disease course, and were more likely to receive conservative treatment. Initial ionized calcium was found to be independently associate with both short-term [adjusted odds ratio (OR): 0.92; 95% confidence interval (CI): 0.86 to 0.99; P=0.020] and long-term mortality [adjusted hazard ratio (HR): 0.95; 95% CI: 0.92 to 0.99; P=0.010], after adjusting for potential confounders. Moreover, the admission glucose level was found to be associated only with short-term mortality (adjusted OR: 1.19; 95% CI: 1.06 to 1.34; P=0.004).

Conclusions

Laboratory screening may provide a useful tool for the management of aSAH patients requiring MV in stratifying risk levels for mortality and for better clinical decision-making. Further study is needed to validate the effects of calcium supplementation and glucose-lowering therapy on the outcomes in this disease.

Increased dietary vitamin D was associated with increased circulating vitamin D with no observable adverse effects in adult dogs

Introduction

There is no consensus for the optimum concentration of vitamin D, although a minimum concentration of 100 ng/mL (250 nM) of circulating vitamin D, measured as 25(OH) D, has been suggested in order to support optimal health in dogs. Few studies have examined the relationship between dietary vitamin D3 (cholecalciferol) intake and the resulting concentrations of circulating 25(OH) D in adult dogs. Recommendations for dog foods for adult maintenance report a safe upper limit of 3,200 IU vitamin D/kg on a dry matter basis. However, these recommendations were not based on studies of adult maintenance requirements. Understanding the relationship between dietary vitamin D and circulating vitamin D is necessary to utilize dietary vitamin D to influence health in dogs.

Methods

Five groups of adult dogs (each n = 8) were fed food of approximately 4,000 kcal/kg containing one of the following dry matter concentrations of vitamin D for 6 months: 795.7, 3087.3, 5510.9, 7314.0, and 9992.5 IU/kg. Body weight was recorded at baseline and measured weekly, and daily food intake was recorded. Blood samples were taken at baseline and at the end of the 26-week study period.

Results

There were no clinical signs of vitamin D deficiency or excess. Serum concentrations of creatinine, blood urea nitrogen, albumin, hematocrit, hemoglobin, alkaline phosphatase, phosphorus, total calcium, ionized calcium, and parathyroid hormone were maintained within reference values in all groups. Circulating 25(OH) D increased in all groups except those that consumed food with 795.7 IU/kg vitamin D, and increased in a linear and quadratic fashion in response to dietary vitamin D concentration. All of the dogs fed food with 5510.9 IU/kg vitamin D or above met or exceeded 100 ng/mL (250 nM) circulating 25(OH) D.

Discussion

Dietary vitamin D was positively associated with increased circulating concentrations in concentrations up to 9992.5 IU/kg dry matter, with no observable adverse effects. Consumption of ≥5510.9 IU/kg vitamin D resulted in all dogs with at least the 100 ng/mL (250 nM) circulating concentration.

The Effect of Hyperventilation Syndrome on Ionized and Serum Calcium: A Case Presentation in the Emergency Department

Hyperventilation syndrome is described as a constellation of symptoms that are typically benign but can become a medical emergency in the setting of severe metabolic derangement secondary to shifts in a patient's pH. A 36-year-old male with a history of intravenous (IV) drug abuse presented to the emergency department (ED) in distress, complaining of diffuse muscle cramping with tetany and peripheral vasospasm. This case report discusses his initial ED testing and treatment when ionized calcium was low and serum calcium was high.

Serum Ionized Calcium as a Prognostic Biomarker in Type B Aortic Dissection After Endovascular Treatment

OBJECTIVE

Lower serum ionized calcium (iCa²⁺) was reported to be associated with a higher risk of adverse events in patients with cardiovascular diseases. This study aimed to investigate the associations between preoperative serum iCa²⁺ and outcomes of type B aortic dissection (TBAD) patients receiving thoracic endovascular aortic repair (TEVAR).

METHODS

Between January 2016 and December 2019, 491 TBAD patients received TEVAR in a single center. Patients with acute or subacute TBAD were included. Serum iCa²⁺ (pH 7.4) was obtained from the arterial blood gas analysis before TEVAR. The study population was grouped into the hi-Ca group (1.11 mmol/L ≤ iCa²⁺ < 1.35 mmol/L) and lo-Ca group (iCa²⁺ < 1.11 mmol/L). The primary outcomes were all-cause mortality. The secondary outcomes were any major adverse clinical events (MACEs), which included all-cause mortality and aortic-related severe complications. To eliminate bias, 1:1 propensity score matching (PSM) was conducted.

RESULTS

Overall, 396 TBAD patients were included in this study. In the total population, there were 119 (30.1%) patients in the lo-Ca group. After PSM, 77 matched pairs were obtained for further analysis. In the matched population, the 30-day mortality and 30-day MACEs between the two groups presented significant differences (p=0.023 and 0.029, respectively). At 5 years, cumulative incidences of mortality (log-rank p<0.001) and MACEs (log-rank p=0.016) were significantly higher in the lo-Ca group than that of the hi-Ca group. Multivariate cox regression analysis indicated that lower preoperative iCa²⁺ (hazard ratio for per 0.1 mmol/L decrease, 2.191; 95% confidence interval, 1.487-3.228, p<0.001) was an independent risk factor for 5-year mortality after PSM.

CONCLUSIONS

Lower preoperative serum iCa²⁺ might have an association with 5-year mortality in TBAD patients after TEVAR. Serum iCa²⁺ monitoring in this population may facilitate the identification of critical conditions.

CLINICAL IMPACT

Our present study found that the cutoff value of preoperative serum iCa²⁺ 1.11 mmol/L, which is slightly lower than the lower limit of the normal range of 1.15-1.35 mmol/L, worked relatively well for discerning the high-risk and low-risk TBAD patients at 5 years. Serum iCa²⁺ monitoring in TBAD patients receiving TEVAR may facilitate the identification of critical conditions.

Prevalence of Trauma-Induced Hypocalcemia in the Prehospital Setting

BACKGROUND

Recent data published by the Special Operations community suggest the Lethal Triad of Trauma should be changed to the Lethal Diamond, to include coagulopathy, acidosis, hypothermia, and hypocalcemia. The purpose of this study is to determine the prevalence of trauma-induced hypocalcemia in level I and II trauma patients.

METHODS

This is a retrospective cohort study conducted at a level I trauma center and Special Operations Combat Medic (SOCM) training site. Adult patients were identified via trauma services registry from September 2021 to April 2022. Patients who received blood products prior to emergency department (ED) arrival were excluded from the study. Ionized calcium levels were utilized in this study.

RESULTS

Of the 408 patients screened, 370 were included in the final analysis of this cohort. Hypocalcemia was noted in 189 (51%) patients, with severe hypocalcemia identified in two (<1%) patients. Thirty-two (11.2%) patients had elevated international normalized ratio (INR), 34 (23%) patients had pH <7.36, 21 (8%) patients had elevated lactic acid, and 9 (2.5%) patients had a temperature of <35°C.

CONCLUSION

Hypocalcemia was prevalent in half of the trauma patients in this cohort. The administration of a calcium supplement empirically in trauma patients from the prehospital environment and prior to blood transfusion is not recommended until further data prove it beneficial.

Reconsideration of "Albumin Corrected Total calcium" Determinations: Potential Errors in the Clinical Management of Disorders of Calcium Metabolism

BACKGROUND

The formula, referenced in major textbooks, for albumin corrected calcium [Calcium_(alb)] may not accurately depict ionized calcium [ICa]. We evaluated the accuracy of unadjusted calcium [Calcium_(Unadjusted)] and [Calcium_(alb)], and developed a protocol for local laboratory adjustment of calcium for albumin.

METHODS

Laboratory data were obtained from an electronic health record. Assessments were accuracy, false positive, and false negative rates. Clinical reliability was defined in "error zones" for calcium [Ca]: Zone A =Ca(normal), ICa(low) ; Zone B =Ca(low), ICa(normal) ; and Zone C =Ca(normal), ICa(high), Zone D=Ca(high), ICa(normal).

RESULTS

A linear regression from 468 laboratory tests was used to derive a formula for "revised corrected calcium" [Calcium _(revised)] over a range of albumin concentrations where, [Calcium _(revised)] = plasma calcium _(mg/dl) + [(4- Albumin _(g/d)L)]*(plasma calcium _(mg/dl)*0.052)]. [Calcium_(alb]] vs [Calcium_(Unadjusted)] decreased zone B errors 12%, [95%CI;8-15%], vs 44% [95%CI;37-50%], p <0.001. However, [Calcium_(alb]] vs [Calcium_(Unadjusted)] increased zone A error (60%,[95%CI;42-78%], vs 7% [95%CI;1-13%], p <0.001). [Calcium _(revised)] decreased zone A errors (15%, [95%CI;6-24%]) vs [Calcium_(alb) ] (60% [95%CI;42-78%], p<0.001) and Zone D errors from 9% [95%CI;6-12%] to 2% [95%CI;1:5%, p<0.001].

CONCLUSIONS

[Calcium_(alb)] is unreliable in hypo- or hypercalcemia. We provide a protocol for locally derived correction of calcium for albumin.

Comparison of Creatinine, Urea, Ionized Calcium, and Bicarbonate Methods by 2 POC Systems and a Mainframe Chemistry Analyzer

BACKGROUND

The i-STAT (iST) and GEM Premier ChemSTAT (ChmST) are point-of-care systems that measure electrolytes, metabolites, acid-base parameters, and hematocrit on blood. We compared results for creatinine, urea (blood urea nitrogen [BUN]), total carbon dioxide (tCo2), and ionized calcium (ion Ca) on blood by the ChmST and iST to Beckman DxC600 (DxC600) results for creatinine and urea on plasma and GEM Premier 5000 (GEM5K) results for ion Ca and tCo2 on blood.

METHODS

107 heparinized blood specimens were analyzed on the ChmST and iST systems, with plasma tested by DxC600 for creatinine and BUN and blood tested by GEM5K for ion Ca and tCo2. We evaluated the methods primarily by the mean and SD of the biases at clinically relevant concentrations.

RESULTS

The correlations of ChmST and iST results on blood for creatinine, BUN, ion Ca, and tCo2 correlated to plasma by the DxC600 and to blood by the GEM5K were r ≥ 0.98 for all analytes except for ion Ca on the iST (r = 0.93). The mean and SD of biases were within clinically and analytically acceptable limits for all methods except for tCo2 on the ChmST, which measures bicarbonate with a bicarbonate-sensing electrode. Also, creatinine and BUN by the ChmST were less affected by icterus or hemolysis than were the DxC600 (icterus) and the iST (hemolysis).

CONCLUSIONS

The ChmST and iST results on blood demonstrated strong correlations with each other and with the DxC600 results on plasma. We conclude the ChmST provides reliable results for whole blood creatinine, urea, ion Ca, and tCo2.

Sample stability and heparin interference in ionized calcium and ionized magnesium measurements in horses using the Stat Profile Prime Plus co-oximetry electrolyte analyzer

BACKGROUND

The determination of iCa and iMg is important in veterinary medicine, but their immediate determination in whole blood is not always possible. Their stability in other sample types and the existence of interferences must be evaluated before its use.

OBJECTIVES

We aimed to analyze the effects of storage time on the stability of iCa, iMg, and other analytes in whole blood, plasma, and serum samples in horses and assess the interference of heparin in these measurements.

METHODS

Whole blood, heparin-plasma, and serum samples from 10 horses were stored at 4°C and analyzed 1, 2, 3, 4, 5, 6, 7, 8, 24, 48, and 168 hours after sample collection using the Stat Profile Prime Plus Vet equipment (Nova Biomedical, Waltham, MA, USA). Results were analyzed by ANOVA or mixed-effect models.

RESULTS

The concentration of iCa, iMg, total calcium (tCa), total magnesium (tMg), and the ratios iCa/tCa and iMg/tMg did not differ up to 168 hours when compared to the initial time. Total Ca, iMg, and tMg were not significantly different among sample types, but iCa concentrations were slightly but significantly lower in plasma. Freezing at -20°C did not affect iCa, iMg, tCa, and tMg. The pH increased in serum and plasma after 8 hours, and a mild negative correlation existed between plasma iCa concentration and pH. A negative correlation was observed also between the ratios iCa/tCa or iMg/tMg and pH in plasma and serum. A significant decrease in iCa and iMg was detected when comparing homemade syringes at high heparin concentration (~200-300 U heparin/mL) and commercial lithium-heparin tubes (20-30 U/mL).

CONCLUSIONS

Samples stored at 4°C can be used to determine iCa and iMg concentrations up to 7 days after collection. Other metabolites are stable for up to 8 hours; heparin interference should be taken into account if using homemade heparin syringes.

The association of admission ionized calcium with outcomes of thrombolysed patients with anterior circulation ischemic stroke

BACKGROUND AND PURPOSE

The relationship between ionized calcium and prognosis of ischemic stroke is controversial. We aim to determine the relationship of admission ionized calcium levels with acute ischemic stroke (AIS) after intravenous thrombolysis (IVT).

METHODS

Consecutive anterior circulation AIS patients treated with recombinant tissue plasminogen activator (rt-PA) were retrospectively enrolled. According to ionized calcium quartiles, the patients were divided into four groups and clinical data were analyzed between groups. Ionized calcium was entered into logistic regression analysis in two models, separately: model 1, calcium as a continuous variable (per 1-mmol/L increase), and model 2, calcium as the four-categorized variable (being collapsed into quartiles: Q1-Q4). Early neurologic improvement (ENI) was defined as improvement of four or more points at 24 h after intravenous rt-PA, while long-term good outcome as the modified Rankin Scale (mRS) 0-1 at 90 days.

RESULTS

A total of 546 patients met the study criteria (mean age was 63.51 ± 11.26 years and 365 [66.8%] were men). The median admission National Institute of Health Stroke Scale was 9 (range 4 to 15). When not adjusted, in model 1: ionized calcium was related to good outcome (odds ratio [OR] 69.061, 95%CI: 1.638-2911.111, p=0.027), but not ENI (OR 14.097, 95%CI: 0.133-1492.596, p=0.266); in model 2: compared with Q4, while good outcome was less common in Q1 (OR 0.623, 95%CI: 0.388-0.999, p=0.049). After adjusting for confounding factors, calcium in Q2 (OR 0.502, 95%CI: 0.253-0.997, p=0.049) was independently associated with ENI, but no matter as a continuous variable or categorized variable, ionized calcium displayed no association with a good outcome.

CONCLUSION

The current results found that ionized calcium might be associated with early neurological improvement, but had no association with 3 months' outcome in anterior circulation AIS patients after IVT.

Serum Levels of Interleukin-1β and Disease Progression in Multiple Myeloma Patients: A Case and Control Study

OBJECTIVE

Multiple myeloma  (MM) is known as an incurable heterogeneous plasma cell malignancy that presents with a variety of clinical manifestations. Inflammation plays an important role in this disease. Cytokines and Chemokines cause the progression of the disease. One of them is interleukin-1β (IL-1β), which may be involved in the pathogenesis of MM. Other markers such as calcium, albumin, creatinine, globulins, and total protein are also used to diagnose and prognosis patients. The main purpose of this study was to evaluate the serum level of IL-1β and various forms of calcium (total calcium, ionized calcium, and corrected calcium), albumin, creatinine, globulin, and total protein on stage-I of MM patients and healthy controls.

METHODS

Serum samples from 30 stage-I MM patients and 30 healthy subjects as controls were examined in this study. The protein concentrations of serum IL-1β was assessed by enzyme-linked immunosorbent assay (ELISA), total calcium, albumin, creatinine, total protein, and globulin Measured by auto analyzer BT3000, an electrolyte analyzer was used to measure ionized calcium (Ca++) and a special equation was used to calculate the corrected calcium.

RESULT

The mean level of IL-1β was significantly elevated in stage-I MM. The mean levels of IL-1β were 7.04±1.15 ng/ml in stage-I MM and 3.12± 0.90 ng/ml in controls (p<0.001). The mean levels of total calcium (total Ca) were 9.45±0.56 mg/dl in stage-I MM and 9.09±0.43mg/dl in controls (p=0.008). The mean levels of ionized calcium (Ca++) was 4.65±0.28mg/dl in stage-I MM and 4.75±0.33mg/dl in controls (p=0.2). The mean ratio of serum ionized calcium to total calcium (Ca++/ total Ca) was 0.49±0.054 in stage-I MM and 0.52±0.047 in controls (p=0.02). The mean ratio of serum ionized calcium to corrected calcium (Ca++/corrected Ca) was 0.42±0.033 in stage-I MM and the Mean ratio of serum ionized calcium to calcium total (Ca++/ total Ca) was 0.52±0.047 in controls, Comparison of the mean of the two groups shows a significant difference (p<0.001). The mean level of albumin was 1.72±0.35 g/dl in stage-I MM and4.32±0.41g/dl in controls (p<0.001). The mean level of total protein was 12.65±0.81g/dl in stage-I MM and 7.07±0.4 g/dl in controls (p<0.001). The mean level of globulin was 11.00±0.96 mg/dl in stage-I MM and 2.85±0.77 mg/dl in controls (p<0.001). The mean level of creatinine was 1.15±0.25 mg/dl in stage-I MM and 0.96±0.15 mg/dl in controls (p=0.001).

CONCLUSION

The results of the study indicate the possible involvement of IL-1β at stage-I MM and it can indicate the role of chemokines in the disease process, especially in the early stages. Changes in the chemical profiles mentioned can help in the diagnosis and prognosis of the disease.

Low Plasma Ionized Calcium Is Associated With Increased Mortality: A Population-based Study of 106 768 Individuals

CONTEXT

Low circulating total calcium or albumin-adjusted calcium has been associated with higher mortality, especially in hospital settings; however, these measures tend to misclassify patients with derangements in calcium homeostasis.

OBJECTIVE

As the association of the biologically active ionized calcium with mortality is poorly elucidated, we tested the hypothesis that low plasma ionized calcium is associated with higher risk of all-cause and cause-specific mortality in the general population.

METHODS

We included 106 768 individuals from the Copenhagen General Population Study. Information on all-cause and cause-specific mortality was from registries and risks were calculated using Cox regression and competing-risks regression by the STATA command stcompet.

RESULTS

During a median follow-up period of 9.2 years, 11 269 individuals died. Each 0.1 mmol/L lower plasma ionized calcium below the median of 1.21 mmol/L was associated with a multivariable adjusted hazard ratio of 1.23 (95% CI, 1.10-1.38) for all-cause mortality. Corresponding hazard ratios for cancer and other mortality were 1.29 (1.06-1.57) and 1.24 (1.01-1.53), respectively. In contrast, for cardiovascular mortality, only high plasma ionized calcium was associated with mortality with a hazard ratio of 1.17 (1.02-1.35) per 0.1 mmol/L higher plasma ionized calcium above the median. We found no interactions between plasma ionized calcium and preexisting cardiovascular or renal disease on all-cause mortality.

CONCLUSION

In the general population, low plasma ionized calcium was associated with increased all-cause, cancer, and other mortality, while high levels were associated with increased cardiovascular mortality.

Automated regional citrate anticoagulation based on online monitoring of ionized calcium concentration: Proof of concept

BACKGROUND

Regional citrate anticoagulation (RCA), a complex and effective technique, is recommended as the anticoagulation of choice for continuous renal replacement therapy. One of its key objectives is to keep the ionized calcium in the targeted range. In this study, we aimed to develop an automated RCA based on online monitoring of the ionized calcium concentration and closed-loop feedback.

METHODS

We constructed calcium-selective electrodes with liquid inner contact, which measured a potentiometric signal as the output. We tested the responses, stability, and selectivity of the electrodes in flowing fluid containing calcium chloride. We compared the measurement accuracy between the electrodes and an i-STAT system in vivo. Moreover, we established closed-loop feedback using a proportional-integral-derivative controller model. We performed simulated automated RCA both in vivo and in vitro.

RESULTS

The electrode gave a Nernstian response to the variation of ionized calcium concentration. It showed high stability and a relatively short response time. Changes in the fluid flow rate, solution PH, and addition of metal ions including Mg²⁺ and K⁺ did not interfere with the measurements of ionized calcium. These measurements in whole blood by the electrode were very close to those assessed by the i-STAT system. The feedback control system responded quickly to an abnormal ionized calcium concentration and regulated the infusion rates of calcium or citrate to maintain the concentration of ionized calcium within the targeted range.

CONCLUSIONS

We successfully trialed automated RCA, which may help simplify the complexities of RCA in the future.

Effects of altering prepartum and postpartum dietary cation-anion difference on calcium concentrations and blood metabolites of Holstein dairy cows

We determined effects of pre- and postpartum dietary cation-anion difference (DCAD) on urine pH, serum calcium and hormone concentrations, and milk production with 48 multiparous Holstein cows (average body weight = 706 ± 7.3 kg). Treatments were 3 prepartum DCAD concentrations (0, -100, or -180 mEq/kg dry matter [DM]) and 2 postpartum DCAD concentrations (+250 or +350 mEq/kg DM) starting 29 days before parturition through 90 days in milk. Prepartum urine pH was lower (p < 0.05) for -180 than for -100 or 0 DCAD, and postpartum urine pH was higher (p < 0.05) for +350 than for +250 DCAD. Prepartum serum total and ionized calcium and hydroxyproline were greater (p < 0.05) for -180 than for -100 and 0 DCAD, whereas parathyroid hormone was greater (p < 0.05) for 0 than for -100 and -180 DCAD. After calving, negative prepartum DCAD increased (p < 0.05) serum total and ionized calcium, but effects varied by sampling day. Pre- and postpartum DCAD did not affect milk yield or milk fat, but milk protein percent and total solids were increased (p < 0.05) by negative prepartum DCAD. Feeding an acidogenic diet prepartum improved postpartum calcium status without major effects on milk yield and composition.

Role of arterial blood gas (ABG) as a valuable assessment tool of disease severity in SARS-CoV-2 patients

BACKGROUND

COVID-19 is caused by a novel coronavirus, named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The foremost predominant complication of SARS-CoV-2 is arterial hypoxemia thereby disturbing lung compliance, requiring mechanical ventilation. The aim of the current research study is to analyze role of ABG as a valuable assessment tool of disease severity in SARS-CoV-2 patients.

METHODS

170 arterial blood samples were collected from patients admitted in Intensive Care Unit (ICU) of Sri Guru Ram Das Charitable Hospital, Amritsar. They were analyzed for arterial blood gas using ABG analyzer. Parameters of ABG such as pH, pCO2, HCO3, O2 saturation, ionized calcium (iCa) and calculated ionized calcium (at pH 7.4) was calculated for all the samples.

RESULTS

Continuous variables were described as medians with interquartile ranges (IQRs) and categorical variables as percentages and frequencies. Spearman correlation test was done for calculation of correlation between pH and other ABG parameters. Analysis of arterial blood gas revealed significant negative correlation (p<0.05) between pH and pCO2 and significant positive correlation (p<0.05) between pH and HCO3 and between pH and delta ionized calcium. Low levels (98.2%) of ionized calcium were observed while monitoring the ABG findings though weak negative correlation (p<0.05) was observed between pH and iCa.

CONCLUSIONS

Our study suggests that ABG analysis acts as a momentous indicator for critically ill patients admitted in Intensive Care Unit (ICU). Estimation of iCa in this critical care setting acts as a distinctive biochemical feature of SARS-CoV-2 disease, as an initial assessment tool, for hypocalcemia.

Prediction of diagnosis and prognosis of COVID-19 disease by blood gas parameters using decision trees machine learning model: a retrospective observational study

The coronavirus disease 2019 (COVID-19) epidemic went down in history as a pandemic caused by corona-viruses that emerged in 2019 and spread rapidly around the world. The different symptoms of COVID-19 made it difficult to understand which variables were more influential on the diagnosis, course and mortality of the disease. Machine learning models can accurately assess hidden patterns among risk factors by analyzing large-datasets to quickly predict diagnosis, prognosis and mortality of diseases. Because of this advantage, the use of machine learning models as decision support systems in health services is increasing. The aim of this study is to determine the diagnosis and prognosis of COVID-19 disease with blood-gas data using the Chi-squared Automatic Interaction Detector (CHAID) decision-tree-model, one of the machine learning methods, which is a subfield of artificial intelligence. This study was carried out on a total of 686 patients with COVID-19 (n = 343) and non-COVID-19 (n = 343) treated at Erzincan-Mengücek-Gazi-Training and Research-Hospital between April 1, 2020 and March 1, 2021. Arterial blood gas values of all patients were obtained from the hospital registry system. While the total-accuracyratio of the decision-tree-model was 65.0% in predicting the prognosis of the disease, it was 68.2% in the diagnosis of the disease. According to the results obtained, the low ionized-calcium value (< 1.10 mM) significantly predicted the need for intensive care of COVID-19 patients. At admission, low-carboxyhemoglobin (< 1.00%), high-pH (> 7.43), low-sodium (< 135.0 mM), hematocrit (< 40.0%), and methemoglobin (< 1.30%) values are important biomarkers in the diagnosis of COVID-19 and the results were promising. The findings in the study may aid in the early-diagnosis of the disease and the intensive-care treatment of patients who are severe. The study was approved by the Ministry of Health and Erzincan University Faculty of Medicine Clinical Research Ethics Committee.

Adjusted calcium concentration as a predictor of ionized hypocalcemia in hypoalbuminemic dogs

Background

Ionized calcium (iCa) is the biologically active fraction of total calcium (tCa) with clinical relevance to evaluate calcium homeostasis, but not all primary veterinarians have access to serum iCa. Formulas that adjust tCa to correct for variability in serum protein concentrations were not designed to predict iCa and are considered unreliable surrogates for iCa.

Objectives

To determine whether adjusted calcium concentration (aCa) can predict ionized hypocalcemia in hypoalbuminemic dogs without hyperphosphatemia.

Animals

A total of 262 hypoalbuminemic dogs without hyperphosphatemia.

Methods

Retrospective review of paired tCa and iCa. Patients were included if serum albumin concentration was ≤2.5 g/L and serum phosphorus concentration was ≤5 mg/dL. The aCa was calculated using tCa (mg/dL) − serum albumin concentration (g/dL) + 3.5 (g/dL). Sensitivity, specificity, positive (PPVs) and negative (NPVs) predictive values, and accuracy were determined for tCa and aCa at predicting any (<1.13 mmol/L) and moderate (<1.02 mmol/L) ionized hypocalcemia. Patients also were stratified into mild‐to‐moderate (2.0‐2.5 g/dL) and severe hypoalbuminemia (<2.0 g/dL).

Results

A total of 4296 dogs had paired results of which 262 met the inclusion criteria. Of these, 35 (13.4%) dogs had iCa < 1.13 mmol/L and 13 dogs (5.0%) had concentrations <1.02 mmol/L. The sensitivity, specificity, NPVs and PPVs of a decreased tCa and aCa for detecting moderate ionized hypocalcemia were 100% and 92.3%, 57.8% and 94.8%, 100% and 99.6%, and 11.0% and 48.2%, respectively, and accuracy was 60.0% and 94.7%, respectively.

Conclusions

A low aCa was useful to detect ionized hypocalcemia in hypoalbuminemic nonhyperphosphatemic dogs. A normal aCa indicated that moderate ionized hypocalcemia was unlikely.

新生儿血钙水平与围生期因素的关系及与智能尿检系统检测的尿钙水平的关系

OBJECTIVE

To study the association of neonatal blood calcium levels with perinatal factors and neonatal urinary calcium levels measured by an intelligent urine test system.

METHODS

The medical data of 96 full-term singleton neonates with mild diseases were collected by a cross-sectional survey, who were hospitalized in the Department of Neonatology, The First Affiliated Hospital of Xi'an Jiaotong University, from June to August 2018. Urinary calcium levels measured by an intelligent urine test system, total blood calcium levels, ionized calcium levels, and the mother's calcium and vitamin D supplementation during pregnancy were recorded.

RESULTS

Compared with the group without vitamin D supplementation for the mother (17 neonates), the group with vitamin D supplementation for the mother (79 neonates) had significantly higher levels of total blood calcium and ionized calcium (P < 0.05).The group with both vitamin D and calcium supplementation for the mother (68 neonates) had significantly higher levels of ionized calcium than controls (28 neonate) (P=0.05). There was no significant difference in the levels of total blood calcium and ionized calcium between the group with calcium supplementation for the mother (74 neonates) and the group without calcium supplementation for the mother (22 neonates) (P > 0.05). The hypothermia group (5 neonates) had a significantly lower level of total blood calcium than the normal body temperature group (91 neonates) (P < 0.05). There was a significantly positive correlation between the maternal blood total calcium level and the neonatal blood total calcium and ionized calcium levels (r=0.881 and 0.703 respectively; P < 0.05). The neonatal urinary calcium level measured by the intelligent urine test system was significantly correlated with the blood ionized calcium level (r=0.526, P=0.025).

CONCLUSIONS

Vitamin D supplementation during pregnancy can increase the blood levels of total calcium and ionized calcium in neonates, and calcium supplementation alone cannot increase the blood levels of total calcium or ionized calcium in neonates. Hypothermia in neonates might cause the reduction in blood calcium levels. The urinary calcium level measured by the intelligent urine test system is positively correlated with the blood level of ionized calcium.

[Association of neonatal blood calcium levels with perinatal factors and neonatal urinary calcium levels measured by an intelligent urine test system]

OBJECTIVE

To study the association of neonatal blood calcium levels with perinatal factors and neonatal urinary calcium levels measured by an intelligent urine test system.

METHODS

The medical data of 96 full-term singleton neonates with mild diseases were collected by a cross-sectional survey, who were hospitalized in the Department of Neonatology, The First Affiliated Hospital of Xi'an Jiaotong University, from June to August 2018. Urinary calcium levels measured by an intelligent urine test system, total blood calcium levels, ionized calcium levels, and the mother's calcium and vitamin D supplementation during pregnancy were recorded.

RESULTS

Compared with the group without vitamin D supplementation for the mother (17 neonates), the group with vitamin D supplementation for the mother (79 neonates) had significantly higher levels of total blood calcium and ionized calcium (P < 0.05).The group with both vitamin D and calcium supplementation for the mother (68 neonates) had significantly higher levels of ionized calcium than controls (28 neonate) (P=0.05). There was no significant difference in the levels of total blood calcium and ionized calcium between the group with calcium supplementation for the mother (74 neonates) and the group without calcium supplementation for the mother (22 neonates) (P > 0.05). The hypothermia group (5 neonates) had a significantly lower level of total blood calcium than the normal body temperature group (91 neonates) (P < 0.05). There was a significantly positive correlation between the maternal blood total calcium level and the neonatal blood total calcium and ionized calcium levels (r=0.881 and 0.703 respectively; P < 0.05). The neonatal urinary calcium level measured by the intelligent urine test system was significantly correlated with the blood ionized calcium level (r=0.526, P=0.025).

CONCLUSIONS

Vitamin D supplementation during pregnancy can increase the blood levels of total calcium and ionized calcium in neonates, and calcium supplementation alone cannot increase the blood levels of total calcium or ionized calcium in neonates. Hypothermia in neonates might cause the reduction in blood calcium levels. The urinary calcium level measured by the intelligent urine test system is positively correlated with the blood level of ionized calcium.

Changes in the Relationship between Ionized and Total Calcium in Clinically Healthy Dairy Cows in the Period around Calving

Simple Summary

Hypocalcemia is a widespread problem in dairy cows in the first days after calving, which increases the risk for secondary diseases. In practice, the measurement of total blood serum or plasma calcium is widely used to diagnose hypocalcemia. The present study demonstrates a high discrepancy between total and ionized calcium specifically around calving, suggesting that only ionized calcium provides an accurate indication of the animal’s calcium status during that period. We developed an optimized model for prediction of ionized calcium from total calcium, non-esterified fatty acids, beta-hydroxybutyric acid, cholesterol, and phosphorous. However, the precision of that model is still unsatisfactory.

Abstract

We aimed to establish a model for prediction of iCa from tCa, using multivariable regressions with diverse blood constituents. Blood was taken from 14 cows at days −2, 0, 2, 4, 7, and 14 relative to parturition. Cows were clinically healthy, and no hypocalcaemia prophylaxis and treatment were applied. Total calcium and further parameters were determined from frozen serum. Ionized calcium, blood gases, and electrolytes were determined from heparin-stabilized blood samples. Linear regression between iCa and tCa was estimated. Precision improved only slightly using a multivariable model. Best precision was achieved when estimating the iCa:tCa ratio from other blood constituents. To identify the reason behind the poorly predictive value of tCa for iCa, the relative changes of iCa and tCa around calving were calibrated to the respective values of day −2 (=100%) for each cow. An increase in the iCa:tCa ratio was observed from 0.43 at day −2 to 0.48 at day 0, followed by a gradual decrease towards 0.43 at day 7. We conclude that routine measurement of iCa should be implemented in the diagnosis of hypocalcaemia. An optimized estimate of iCa from tCa with non-esterified fatty acids (NEFA), beta-hydroxybutyric acid, cholesterol, and phosphorous as co-predictors is still poorly satisfying.

Validation of the bovine blood calcium checker as a rapid and simple measuring tool for the ionized calcium concentration in cattle

Point-of-care (POC) devices that veterinary practitioners can use to easily and rapidly measure blood ionized calcium (iCa) levels in cows immediately after withdrawing a blood sample on the dairy farm are needed. Aims of present studies was to compare the commercially available ion-selective electrode handheld iCa meter (bovine blood iCa checker) with the benchtop blood gas analyzer GEM premier 3500 and handheld analyzer i-STAT 1. Sixty-two paired-point whole blood samples were obtained from three cows with hypocalcemia experimentally induced by Na₂-EDTA infusion. Whole blood samples were also obtained from the 36 cows kept on a farm in field conditions. The results using the bovine blood iCa checker correlated with those using the GEM premier 3500 and i-STAT 1. Bovine blood iCa checker was “compatible” with the GEM premier 3500 and i-STAT 1 because the frequency of differences between the measurements within ± 20% of the mean were 100% (65/65, >75%) and 90.8% (59/65, >75%), respectively. In the field trial, the blood iCa concentration measured by the bovine blood Ca checker was significantly positively correlated with that measured by the i-STAT 1 portable analyzer. Bovine blood iCa checker was “compatible” with the i-STAT 1 because the frequency of differences between the measurements within ± 20% of the mean was 100% (36/36, >75%). Results from these findings, the bovine blood iCa checker may be applied as a simplified system to measure the iCa concentration in bovine whole blood.

Pharmacokinetics of magnesium and its effects on clinical variables following experimentally induced hypermagnesemia

The objectives of this study were to describe pharmacokinetic and pharmacodynamic changes as a result of a single intravenous administration of magnesium sulfate (MgSO₄ ) to healthy horses. MgSO₄ is a magnesium salt that has been used to calm horses in equestrian competition and is difficult to regulate because magnesium is an essential constituent of all mammals. Six healthy adult female horses were administered a single intravenous dose of MgSO₄ at 60 mg/kg of body weight over 5 min. Blood, urine, and cerebrospinal fluid (CSF) samples were collected, and cardiovascular parameters were monitored and echocardiograms performed at predetermined times. Noncompartmental pharmacokinetic analysis was applied to plasma concentrations of ionized magnesium (Mg²⁺ ). Objective data were analyzed using the Wilcoxon rank-sum test with p < .05 used as a determination for significance. Plasma concentrations of Mg²⁺ increased nearly fivefold, ionized calcium (Ca²⁺ ) decreased by nearly 10%, and the Ca²⁺ to Mg²⁺ ratio declined more than 3.5-fold and remained different than baseline until 24 hr (p < .05). Significant changes were seen with urinary fractional excretion of electrolytes, cardiovascular parameters, and echocardiographic measurements. No changes were detected in CSF electrolyte concentrations. The decrease in Ca²⁺ result of hypermagnesemia supports the interaction between these cations. Alterations detected in plasma electrolyte concentrations and urinary fractional excretion of electrolytes may serve as biomarkers for regulatory control for the nefarious administration of MgSO₄ .

Selected Physicochemical Properties of Saliva in Menopausal Women-A Pilot Study

The aim of this study was to estimate differences in selected physicochemical properties of saliva between menopausal and premenopausal women. Methods: The study population consisted of 9 menopausal women and 15 women of the control group. Laboratory tests included the determination of pH saliva, salivary flow rate, and concentrations of lactoferrin, lysozyme, immunoglobulin A, and ionized calcium. Results: Among menopausal women, statistically significant differences were observed in values of salivary flow rate and lysozyme and ionized calcium concentrations; however, no statistically significant differences for pH and concentrations of lactoferrin and immunoglobulin A were found. The salivary flow rate in the study group was significantly lower compared to that in premenopausal women. In relation to lysozyme, statistically significant differences were found between control group and menopausal women to the disadvantage of the latter. However, the concentration of ionized calcium in the saliva of menopausal women was distinctly higher than in the saliva of the control group. Conclusion: The saliva of menopausal women appeared significantly different from that of the control group. Differences in physicochemical parameters such as salivary flow rate and lysozyme and ionized calcium concentrations were observed. These differences in saliva properties observed in menopause can potentially affect the oral environment of women in this particular period, possibly increasing the risk of some pathological changes in the oral cavity and consequently indicating the need to take special care of this group of female patients in order to help them maintain proper oral health. Dentists and gynecologists should be aware of the problems associated with menopause and need to provide these women complete health care, including dental care as an integral part.

Changes in ionized calcium concentration in the blood of dairy cows with peracute coliform mastitis

We determined the clinical signs and blood ionized calcium (iCa) levels in dairy cows with peracute coliform mastitis (PCM). The clinical scores at the onset of the disease (day 0) and on day 2 and subsequent days were significantly (P<0.01) higher than those of healthy cows. We found a positive correlation (r=0.894, P<0.01) between iCa and total calcium (TCa) concentrations in the blood of healthy cows ; however there was no correlation from day 0 to day 3 in the blood of PCM cows. Multiple regression analysis revealed that the concentration of iCa was correlated with rectal temperature, hematocrit value, platelet count, and albumin level of PCM cows at the onset of disease (r= −0.804, r=0.6576, r=0.6182, r=0.284, P<0.01, respectively). There was no correlation between the TCa concentration and these parameters for PCM cows at day 0. Low blood iCa concentration at day 0 for PCM cows was related to symptoms of septic shock involving hypothermia, activation of the blood coagulation system, and dehydration.

Resolution of hypercalcemia in primary hyperparathyroidism with vitamin D replacement

Vitamin D deficiency is common in patients with primary hyperparathyroidism. We present a case of primary hyperparathyroidism with a positive parathyroid scan and history of nephrolithiasis. The patient had normal albumin and renal function but was vitamin D deficient. After treatment with vitamin D for 13 months, her parathyroid hormone values declined in parallel with the elevation in vitamin D. Although her total calcium normalized, her ionized calcium remained elevated throughout treatment. We believe vitamin D deficiency should be carefully monitored in primary hyperparathyroidism.

Calcium state estimation by total calcium: the evidence to end the never-ending story

Background Total blood calcium (TCa) is routinely used to diagnose and manage mineral and bone metabolism disorders. Numerous laboratories adjust TCa by albumin, though literature suggests there are some limits to this approach. Here we report a large retrospective study on agreement rate between ionized calcium (iCa) measurement and TCa or albumin-adjusted calcium measurements. Methods We retrospectively selected 5055 samples with simultaneous measurements of iCa, TCa, albumin and pH. We subgrouped our patients according to their estimated glomerular filtration rate (eGFR), albumin levels and pH. We analyzed each patient's calcium state with iCa as reference to determine agreement rate with TCa and albumin-adjusted calcium using Payne, Clase, Jain and Ridefelt formulas. Results The Payne formula performed poorly in patients with abnormal albumin, eGFR or pH levels. In patients with low albumin levels or blood pH disorders, Payne-adjusted calcium may overestimate the calcium state in up to 80% of cases. Similarly, TCa has better agreement with iCa in the case of hypoalbuminemia, but performed similarly to the Payne formula in patients with physiological albumin levels. The global agreement rate for Clase, Jain and Ridefelt formulas suggests significant improvement compared to Payne calcium adjustment but no significant improvement compared to TCa. Conclusions Total and albumin-adjusted calcium measurement leads to a misclassification of calcium status. Moreover, accurate calcium state determination depends on blood pH levels, whose measurement requires the same pre-analytical restrictions as iCa measurement. We propose that iCa should instead become the reference method to determine the real calcium state.

The possibility of using effluent ionized calcium to assess regional citrate anticoagulation in continuous renal replacement therapy

AIM

This study aimed to investigate whether effluent ionized calcium was an appropriate indicator to assess anticoagulant effect in continuous renal replacement therapy with regional citrate anticoagulation instead of post-filter ionized calcium.

METHODS

In total, 48 paired samples of effluent fluid and post-filter blood were obtained from critically ill patients who required continuous renal replacement therapy. All samples were taken for ionized calcium measurements and were assessed by point-of-care analyzer. Correlations and agreements between two methods were performed by Pearson linear analysis and Bland-Altman analysis accordingly.

RESULTS

The mean post-filter ionized calcium was 0.42 ± 0.12 mmol/L, and mean ionized calcium level of effluent fluid was 0.39 ± 0.11 mmol/L. The ionized calcium level of effluent fluid was significantly correlated with post-filter ionized calcium in all continuous renal replacement therapy patients. Bland-Altman analysis showed that the mean difference of ionized calcium between two sampling sites in all continuous renal replacement therapy patients was -0.02 mmol/L with 95% confidence interval ranging from -0.09 to 0.04 mmol/L. The significant correlations and agreements were also demonstrated in continuous veno-venous hemofiltration, continuous veno-venous hemodialysis, and continuous veno-venous hemodiafiltration modalities separately.

CONCLUSION

The effluent ionized calcium could be a considerable substitute for post-filter ionized calcium to monitor the validity of regional citrate anticoagulation in continuous renal replacement therapy with less blood loss.

Determination of a serum total calcium concentration threshold for accurate prediction of ionized hypercalcemia in dogs with and without hyperphosphatemia

Background

Total serum calcium (tCa) concentrations are poorly predictive of ionized calcium (iCa) status in dogs.

Hypothesis

There is an optimal threshold of tCa concentration that is highly predictive of ionized hypercalcemia and this threshold is higher in hyperphosphatemic dogs as compared to nonhyperphosphatemic dogs.

Animals

Nonhyperphosphatemic (n = 1593) and hyperphosphatemic (n = 250) adult dogs.

Methods

Retrospective medical record review of paired tCa and iCa concentration measurements in dogs presented to a university teaching hospital over a 5‐year period. Positive and negative predictive values, sensitivity, and specificity were calculated for tCa concentration thresholds of 11.0‐15.0 mg/dL (upper limit of laboratory reference interval = 11.5 mg/dL) in nonhyperphosphatemic and hyperphosphatemic groups.

Results

In nonhyperphosphatemic dogs, an optimal tCa concentration threshold of 12.0 mg/dL resulted in a positive predictive value of 93% (95% confidence interval [CI], 84%‐98%) and sensitivity of 52% (95% CI, 43%‐61%) for ionized hypercalcemia. An optimal tCa concentration threshold was not identified for hyperphosphatemic dogs. The nonhyperphosphatemic dogs had a higher prevalence of ionized hypercalcemia than the hyperphosphatemic dogs (7 versus 3%, P = .04) and a lower prevalence of ionized hypocalcemia (23 versus 62%, respectively; P < .001).

Conclusions and Clinical Importance

High tCa concentrations are strongly predictive of ionized hypercalcemia in nonhyperphosphatemic adult dogs and should prompt further diagnostic testing to determine the underlying cause of hypercalcemia. In this population, dogs without increased tCa concentrations rarely had ionized hypercalcemia, but iCa concentrations still should be evaluated in patients with tCa concentrations within the reference interval if there is clinical suspicion for calcium abnormalities.

Time-dependent variation of ionized calcium in serum samples

Introduction

The aim of this study was to compare ionized calcium (iCa) concentrations in arterial heparinized blood and venous serum and to investigate time-dependent variation of iCa in serum samples centrifuged and analysed at different times.

Materials and methods

Ionized calcium was measured (N = 25) in arterial blood within 20 min after puncture, and in serum within 10 min after centrifugation conducted 30 min after sampling. Effect of time between sampling and centrifugation was examined in three tubes (N = 30) centrifuged 15, 30 and 60 min after sampling, and analysed within 10 min. Effect of time between centrifugation and analysis was investigated in three tubes (N = 31) centrifuged 30 min after sampling and analysed: 0-10, 30-40 and 90-100 min after centrifugation. Ionized calcium was measured on the Siemens RapidLab 348EX analysers. Statistical significance was tested using Wilcoxon test and ANOVA analysis. Clinical significance was judged against reference change values (RCV).

Results

No statistically significant difference was found between iCa in arterial blood and serum (P = 0.274). A statistically significant decrease was found: in tubes centrifuged 60 and 15 min after sampling versus 30 min (P = 0.005, P = 0.003); and in tubes analysed 30-40 and 90-100 min after centrifugation versus 0-10 min (P = 0.021, P = 0.027). Clinically significant changes were observed: 60 versus 30 min (centrifugation) and 90-100 versus 0-10 and 30-40 min (analysis).

Conclusions

Timely analysed arterial blood and serum samples can be used interchangeably. To avoid clinically significant variations, serum tubes should be centrifuged within 30 min after sampling, and analysis should be performed within 30 min after centrifugation.

EVALUATION OF PLASMA 25-HYDROXYVITAMIN D, IONIZED CALCIUM, AND PARATHYROID HORMONE IN GREEN SEA TURTLES (CHELONIA MYDAS) EXPOSED TO DIFFERENT INTENSITIES OF ULTRAVIOLET B RADIATION

For many reptile species, adequate ultraviolet B (UVB) radiation is essential for proper calcium metabolism. In this study, the effects of UVB radiation on calcium metabolism were evaluated in green sea turtles (Chelonia mydas). 25-Hydroxyvitamin D, parathyroid hormone (PTH), and ionized calcium (iCa) were measured in juvenile (n = 18, 9 indoor, 9 outdoor) and adult (n = 8, 4 indoor, 4 outdoor) turtles. All animals were fed an identical diet. Outdoor animals had access to unfiltered sunlight, whereas indoor animals were housed under artificial lighting without UVB. Mean values for 25-hydroxyvitamin D for the outdoor and indoor groups were 34.33 ± 7.98 nmol/L and 7.11 ± 1.69 nmol/L for juveniles and 73.25 ± 30.34 nmol/L and 14.0 ± 11.52 nmol/L for adults respectively. Mean values for iCa for the outdoor and indoor groups were 0.98 ± 0.07 mmol/L and 0.99 ± 0.06 mmol/L for juveniles and 1.18 ± 0.22 mmol/L and 0.97 ± 0.18 mmol/L for adults respectively. UVB exposure (P < 0.001) and age (P < 0.001) had a significant effect on 25-hydroxyvitamin D as well as a significant interaction between the two variables (P = 0.008), with highest values in adult outdoor turtles. There was a significant interaction between age group and UVB status for iCa (P = 0.036), with greater values in older outdoor turtles. 25-Hydroxyvitamin D and total calcium were positively correlated, rs = 0.39, P = 0.042. iCa and calcium-to-phosphorus ratios were also positively correlated, rs = 0.42, P = 0.027. These results suggest that UVB exposure is an important source of 25-hydroxyvitamin D for green sea turtles and has significant effects on calcium metabolism in this species. PTH values in this study were near the minimum limits of detection and suggest that current mammalian-based PTH assays are not valid for reptiles.

Effects of pH and the plasma or serum concentrations of total calcium, chloride, magnesium, l-lactate, and albumin on the plasma ionized calcium concentration in calves

Background

The plasma ionized calcium concentration (cCa²⁺) represents the biologically active form of calcium and is the preferred method for evaluating calcium status in animals. Different pH‐corrective equations have been developed for human plasma, but the validity of the equations for bovine plasma is unknown.

Hypothesis

We hypothesized that pH‐corrective equations for bovine plasma would be similar to those used for human plasma; cCa²⁺ was dependent on the plasma concentrations of total calcium (cTCa), chloride (cCl), L‐lactate (cLactate), and albumin (cAlbumin); and the in vitro and in vivo cCa²⁺‐pH relationships would differ.

Animals

Ten healthy calves (in vitro study), 1426 critically ill calves.

Methods

The in vitro plasma log₁₀(cCa²⁺)‐pH relationship was determined by CO₂ tonometry of 465 plasma samples. Plasma cCl was altered by equivolume dilution of plasma with 3 electrolyte solutions of different cCl. The in vivo plasma cCa²⁺‐pH relationship was investigated and validated using clinicopathologic data extracted from the medical records of 950 (model development) and 476 (model validation) critically ill calves.

Results

pH‐corrective equations for bovine plasma were similar to those used for human plasma. Plasma cCa²⁺ increased in vitro with increases in plasma cCl. Plasma cCa²⁺ in critically ill calves was associated with plasma cTCa, blood pH, plasma cCl, serum cMg, and cL‐lactate (R² = 0.69) but not plasma cAlbumin.

Conclusions and Clinical Importance

Calculation of cCa²⁺ from cTCa in calf plasma or serum requires adjustment for at least pH and cCl when 1 or both are outside the reference range.

Ionized calcium in human cerebrospinal fluid and its influence on intrinsic and synaptic excitability of hippocampal pyramidal neurons in the rat

It is well-known that the extracellular concentration of calcium affects neuronal excitability and synaptic transmission. Less is known about the physiological concentration of extracellular calcium in the brain. In electrophysiological brain slice experiments, the artificial cerebrospinal fluid traditionally contains relatively high concentrations of calcium (2-4 mM) to support synaptic transmission and suppress neuronal excitability. Using an ion-selective electrode, we determined the fraction of ionized calcium in healthy human cerebrospinal fluid to 1.0 mM of a total concentration of 1.2 mM (86%). Using patch-clamp and extracellular recordings in the CA1 region in acute slices of rat hippocampus, we then compared the effects of this physiological concentration of calcium with the commonly used 2 mM on neuronal excitability, synaptic transmission, and long-term potentiation (LTP) to examine the magnitude of changes in this range of extracellular calcium. Increasing the total extracellular calcium concentration from 1.2 to 2 mM decreased spontaneous action potential firing, induced a depolarization of the threshold, and increased the rate of both de- and repolarization of the action potential. Evoked synaptic transmission was approximately doubled, with a balanced effect between inhibition and excitation. In 1.2 mM calcium high-frequency stimulation did not result in any LTP, whereas a prominent LTP was observed at 2 or 4 mM calcium. Surprisingly, this inability to induce LTP persisted during blockade of GABAergic inhibition. In conclusion, an increase from the physiological 1.2 mM to 2 mM calcium in the artificial cerebrospinal fluid has striking effects on neuronal excitability, synaptic transmission, and the induction of LTP. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Read the Editorial Highlight for this article on page 435.

Hypercalcemia of Malignancy in a Dog Diagnosed With Cholangiocellular Carcinoma

A 4-year-old, neutered male Golden Retriever was presented with a 1-week history of weight loss, polyuria, and polydipsia. The diagnostic workup showed an increased ionized calcium concentration, mild increase in serum creatinine and urea concentration, and severe hyperlipasemia. A complete abdominal ultrasound revealed multiple hepatic nodules. A cytological diagnosis of malignant epithelial neoplasia, highly suggestive of bile duct adenocarcinoma was made. In order to confirm the presumptive diagnosis of hypercalcemia of malignancy due to the presence of a hepatic neoplasia, serum parathormone-related peptide concentration was measured, and the result revealed an increased concentration. The dog was hospitalized and received supportive treatments consisting of intravenous furosemide and fluid therapy. After ruling out lymphoma and hypoadrenocorticism, oral prednisone was initiated and ionized calcium concentration decreased gradually down to normal concentration after 7 days of hospitalization. Chemotherapy with intravenous epirubicin was initiated based on the cytological diagnosis. One month after diagnosis and due to the worsening of its clinical condition, the dog was humanely euthanized. Postmortem examination confirmed a cholangiocellular carcinoma. To our knowledge, this is the first report of malignant hypercalcemia associated with cholangiocellular carcinoma in a dog.

Ionized magnesium and calcium concentration and their ratio in equine plasma samples as determined by a regulatory laboratory compared to a clinical reference laboratory

Magnesium sulfate (MgSO₄ ) was administered to calm competition horses. We evaluated the impact of regulatory requirements for the handling of blood samples on plasma ionized magnesium (iMg), ionized calcium (iCa), the iMg to iCa ratio, and pH. We hypothesized that iCa, iMg. and iMg/iCa would be similar among storage and collection methods. Four blood samples were collected from each of 50 horses on the same day: Group 1 - collection in a heparinized syringe and processed within hours in a clinical laboratory; Group 2 - collection into a plasma separator tube (PST) centrifuged just prior to analysis, and plasma processed as in (1); Group 3 - collection into a PST, refrigerated, shipped via overnight carrier to the United States Equestrian Federation (USEF) Equine Drug Testing and Research laboratory, centrifuged just prior to analysis, and plasma processed; and Group 4 - as in Group 3, but stored frozen at -80°C for 90 days, thawed, and plasma processed as in Group 3. Results for iMg/iCa are unit-less, adjusted iMg for potential influence of plasma protein and iCa, and highly correlated with iMg pH (r = -.933; P < 0.01). Samples processed immediately in a clinical reference laboratory had the greatest iMg/iCa. Both iMg/iCa and pH predictably decreased after freezing (P < 0.001). These data suggest that the iMg/iCa mirrors alterations in iMg regardless of storage and collection methods. This understanding can facilitate the development of a regulatory threshold for the control of the nefarious use of magnesium sulfate in competing horses, and an understanding of potential changes to iMg/iCa with storage of B samples.

Blood calcium, glucose and haematology profiles of parturient bitches diagnosed with uterine inertia or obstructive dystocia

Bitches with dystocia most often present with clinical signs of uterine inertia (UI). The aetiology of myometrial dysfunction in most of these cases is still not elucidated. We compared blood ionized calcium (iCa) and glucose concentrations in bitches diagnosed with primary UI (PUI, n = 14), secondary UI (SUI, n = 6) or obstructive dystocia (OD, n = 6), and we described their haematology profiles. Bitches diagnosed with UI had a patent birth canal and delivered no puppies yet (PUI) or only part of the whole litter (SUI). The OD group had no UI and showed strong abdominal contractions. Blood iCa did not differ between the PUI, SUI and OD groups and was not influenced by litter size. There was a significant positive relationship (R²  = .241, p = .013) between iCa concentrations and the dam's body weight. Glucose concentrations were also not significantly different between dystocia groups or influenced by body weight and litter size. Hypocalcaemia was detected in 11 bitches, and hypoglycaemia in two bitches. Pregnancy-associated anaemia was seen in about one-third of the bitches. Eight of 12 dogs had increased platelet counts, and ten had leukocytosis with mature neutrophilia. Although iCa did not differ between dystocia groups, low concentrations may have contributed to the development of UI in some of the small size bitches. Hypoglycaemia was uncommon, and therefore, we consider low glucose concentrations not to have played an important role in the pathogenesis of UI in our study population. Pregnancy-associated anaemia, thrombocytosis, leukocytosis and mature neutrophilia were common findings in otherwise healthy bitches diagnosed with different forms of dystocia.

Blood ionized calcium levels and acute-phase blood glucose kinetics in goats after intramammary infusion of lipopolysaccharide

The aim of this study was to determine the blood ionized calcium (Ca) levels and acute-phase blood glucose kinetics in goats with mastitis induced by an intramammary challenge of lipopolysaccharide (LPS). Five goats were subjected to intramammary challenge of either LPS (10 µg) or saline (control). Some clinical manifestations (rectal temperature, pulse rate, respiration rate, ruminal motility, physical activity, and dehydration) were observed, and blood was collected for the measurement of several parameters [ionized and total Ca levels, blood glucose level, pH, and white blood count (WBC)] at 0 (just before challenge), 1–4, 6, 8, 12 and 24 hr post-challenge in both the LPS and control phases. Milk was collected at 0 (just before challenge), 4, 8, 12 and 24 hr post-challenge to measure the somatic cell count (SCC) and N-acetyl-beta-D-glucosaminidase (NAGase) activity. In the LPS phase, increased rectal temperature, significantly decreased ionized Ca and total Ca levels and WBCs were observed compared with those at 0 hr, although there were no differences in all parameters between phases. LPS infusion significantly increased SCCs in milk and NAGase activity. The present results demonstrated that, during the acute phase of mastitis induced by intramammary challenge by LPS at a concentration sufficient to cause general symptoms in goats, a decreased blood ionized Ca level occurs, but not hypoglycemia.

Evaluation of Bone Density, Serum Total and Ionized Calcium, Alkaline Phosphatase and 25-hydroxy Vitamin D in Papillary Thyroid Carcinoma, and their Relationship with TSH Suppression by Levothyroxine

BACKGROUND

This study aimed to evaluate the situation of Bone Mineral Density (BMD), Z score, T score, serum level of corrected and ionized calcium, alkaline phosphatase and 25-hydroxy vitamin D in percutaneous transhepatic cholangiography (PTC) patients and correlation of these variants with thyroid stimulating hormone (TSH) suppression level by levothyroxine.

MATERIALS AND METHODS

Among the patients referred to Esfahan's endocrinology research center, 34 PTC patients (aged 20-50 years) with a history of thyroidectomy and conceived radioactive iodine and suppressive dose of levothyroxine were evaluated in this case-control study, and 38 healthy persons participated as the control group (matched by age and sex, body mass index). Bone density was evaluated with the DEXA method in four areas: Lumbar spine, femoral neck, and trochanter and distal of forearm. A reference laboratory assessed TSH, corrected and ionized calcium, Alkaline phosphatase (ALP) and 25OH vitamin D levels using fasting plasma and evaluated correlation of TSH level with variants by multivariate variance analysis.

RESULTS

There was no significant difference in bone density and laboratory data (unless TSH) between the groups. In the PTC group, there was no significant correlation between TSH and difference values of BMD, Z score or T score, corrected calcium (P value = 0.12), ionized calcium (P = 0.54), ALP (P = 0.22) and 25 OH vitamin D (P = 0.38). There was no significant correlation in the TSH subgroups with BMD. The TSH suppression level has no relation with the elevated prevalence of low BMD, hypocalcemia and vitamin D deficiency. Difference in odds ratio was not significant for osteopenia and osteoporosis between the TSH subgroups (TSH < 0.02, >0.02 and <0.1 and >0.1 mu/L).

CONCLUSION

Suppressive therapy with levothyroxine cannot decrease BMD, Z score and T score in PTC patients.

HEALTH SURVEY INCLUDING SELECTED BLOOD PARAMETERS IN THE AFRICAN SLENDER SNOUTED CROCODILE (MECISTOPS CATAPHRACTUS) AT THE ABIDJAN ZOO IN CÔTE D'IVOIRE

The Zoo National d'Abidjan (Abidjan Zoo) in Côte d'Ivoire, West Africa, holds the world's largest captive population of African slender-snouted crocodiles (Mecistops cataphractus, formerly Crocodylus cataphractus), at 36 adults, 16 yearlings, and 23 hatchlings. Twelve yearling and 12 adult slender-snouted crocodiles at the Abidjan Zoo were restrained for physical exam, body condition scoring, and venipuncture in September 2015. Blood samples collected from the supravertebral venous sinus were analyzed using a handheld blood analyzer (Abaxis® I-stat, Abaxis, Inc., Union City, California 94587, USA) with Chem8+ cartridges (CLIAwaived, Inc., San Diego, California 92130, USA). The adult crocodiles appeared in good general health and demonstrated blood values similar to those of other reptiles. The yearlings had low, ionized calcium values and low hematocrit and hemoglobin levels compared with the adult crocodiles and to other crocodile reference ranges. These findings may dramatically improve the health of the crocodiles and help to ensure a thriving captive population of this critically endangered species.

Association of Serum Calcium Levels with Infarct Size in Acute Ischemic Stroke: Observations from Northeast India

BACKGROUND

Calcium is known to be major mediator in ischemic neuronal cell death. Recent studies have shown that elevated serum calcium levels at admission in patients with stroke have been associated with less severe clinical deficits and with better outcomes.

AIM

The aim of this to determine the correlation between serum calcium (total, corrected, and ionized) and infarct size (IS) in patients with acute ischemic stroke.

MATERIALS AND METHODS

Data were collected from 61 patients presenting with acute ischemic stroke from May 2015 to April 2016 at a tertiary care institute in Northeast India. Only patients aged ≥40 years and diagnosed as having acute ischemic cerebrovascular stroke with clinical examination and confirmed by a computed tomography scan were included in the study. Serum calcium levels (total, albumin corrected, and ionized) were collapsed into quartiles, and these quartile versions were used for calculating correlation. Pearson's correlation coefficient was used for comparing calcium levels with IS.

RESULTS

Total calcium, albumin-corrected calcium, and ionized calcium had a statistically significant negative correlation with IS with r = -0.578, -0.5396, and -0.5335, respectively. Total and ionized calcium showed a significant negative correlation with IS across all four quartiles. Albumin-corrected calcium levels showed a significant negative correlation with IS only across the lowest and highest quartiles.

CONCLUSION

The findings in our study suggest that serum calcium can be used as a prognostic indicator in ischemic stroke as its levels directly correlates with the IS.

THE EFFECT OF UVB RADIATION ON SERUM VITAMIN D AND IONIZED CALCIUM IN THE AFRICAN SPOONBILL (PLATALEA ALBA)

Metabolic bone disease (MBD) was diagnosed in two chicks produced by a captive breeding colony of African spoonbills (Platalea alba). The birds were housed indoor during the winter breeding season and had no access to natural sunlight. When the index cases occurred, the nesting birds and chicks had a mean 25-hydroxyvitamin D (25-OHD) concentration of 9.9 ± 2.7 nmol/L and a mean ionized calcium (iCa) concentration of 0.98 ± 0.12 mmol/L (winter pretreatment). For comparison purposes, serum was collected the following summer; mean 25-OHD was 20.8 ± 3.9 nmol/L and mean iCa was 1.32 ± 0.05 mmol/L (summer). During the following breeding season, ultraviolet B (UVB) lighting was provided to the flock, resulting in a mean 25-OHD of 19.0 ± 5.6 nmol/L and mean iCa of 1.23 ± 0.06 mmol/L (winter treatment 1). Both 25-OHD and iCa were significantly higher compared with winter pretreatment, and 25-OHD was not significantly different from summer, indicating that treatment during the winter months succeeded in increasing 25-OHD levels to summer levels. However, winter treatment 1 and summer iCa were significantly different. During the next breeding season (winter treatment 2), the birds were exposed to a light with higher UVB output. The mean 25-OHD of the flock was 16.5 ± 7.2 nmol/L, and the mean iCa increased to 1.34 ± 0.04 mmol/L. Both were comparable to summer values. Healthy chicks were hatched during both breeding seasons, and no further cases of MBD occurred during the course of the study. Provision of a UVB light source to captive African spoonbills maintained indoors during the winter months can increase 25-OHD and iCa to levels equivalent to those seen in the summer months, when birds have unrestricted access to natural sunlight. UVB lighting is recommended for all breeding spoonbills that do not have access to natural sunlight.

Usefulness and feasibility of measuring ionized calcium in haemodialysis patients

Background

Measuring blood calcium level is recommended in haemodialysis (HD) patients. The Kidney Disease Improving Global Outcomes position states that the measurement of ionized calcium (ICa) level is preferred, but in the clinical setting, due to technical difficulties, total calcium (tCa) level is preferred to ICa.

Aim

The aim of this study was to test the possibility of delayed ICa analysis using frozen serum, and so to identify the factors associated with predialysis ICa level and compare the ability of tCa and Alb-Ca to predict ICa level and finally to compare the survival rate according to the three calcium measurements.

Methods

All prevalent HD patients, dialysed by a native AV fistula in a 3 × 4 to 3 × 8 h schedule, had their predialysis ICa, tCa and Alb-Ca levels and usual mid-week biology recorded. Intergroup comparisons between ICa quartile were performed. Bland–Altman plots and linear regression were used to assess the differences between 30 fresh and frozen samples. Survival analyses were performed using ICa and tCa levels.

Results

Comparing fresh blood and frozen serum samples, linear regression (y = 0.98 + 0.02, r = 0.961) showed that the two methods were quite identical with the same mean ICa value (1.1 ± 0.1 mmol/L, P = 0.45). A total of 160 HD patients were included in the study. Hypocalcaemia, using ICa values, was highly prevalent in our population (40%) whereas hypercalcaemia was observed only in three cases (1.8%). In predicting ICa hypocalcaemia (<1.12 mmol/L, n = 64), the use of tCa was accurate in 48.4% of patients, and the use of Alb-Ca was accurate in only 17.2% of patients; tCa was not a predictive factor for hypercalcaemia (ICa > 1.32 mmol/L, n = 3); Alb-Ca value predicted hypercalcaemia in 2/3 of the patients. In predicting normocalcaemia, the use of tCa values was correct in 92.4% of patients and the use of Alb-Ca values in 88.1% of patients; only younger age (P = 0.03) and female sex (P = 0.01) were associated with higher ICa quartile. None of the three calcium measures was significantly associated with survival rate using log-rank and Cox models adjusted for age, dialysis vintage, diabetes and sex.

Conclusion

In the present study, we report that (1) delayed ICa measure is feasible in dialysis patients using a freezing technique, (2) hypocalcaemia is highly prevalent in HD patients and poorly predicted by Alb-Ca level, (3) the main factor associated with ICa level is sex of the individual and (4) calcaemia is not associated with survival rate using any of the three methods.