Integration of acid-base and electrolyte disorders

Sodium-chloride difference is not strongly correlated with base excess in chronic kidney disease: an anion gap problem

INTRODUCTION

The prevalence of metabolic acidosis is high in patients with chronic kidney disease (CKD). For the diagnosis, a blood gas analysis is necessary, but not always available. The aim of the study was to evaluate the base excess (BE) of the sodium-chloride difference (BENa-Cl = Na+-Cl--34 mmol/l) as a screening parameter for hyperchloremic metabolic acidosis.

METHODS AND STATISTICAL ANALYSIS

We retrospectively performed acid-base analyses of 168 non-dialysed patients with CKD according to the physiologic and to the Stewart's approach. We performed linear regression analysis, Bland-Altman plot and receiver operating characteristics (ROC) analysis of BENa-Cl and BE to evaluate the accuracy of BENa-Cl predicting the BE. We further investigated possible confounding factors.

RESULTS

The corrected R2 for the correlation of BENa-Cl and BE was 0.60 (p < 0.001). The Bland-Altman plot showed a good overall agreement. The bias was negligible, but the 95%-limits of agreement showed a wide interval (10.4 mmol/l). For BE ≤ 2 mmol/l, the ROC analysis yielded an AUC of 0.89 and moderate sensitivity (0.75) and specificity (0.86) for the optimal BENa-Cl threshold (≤ 2 mmol/l). Subgroup analysis showed similar results. The main factor for the imprecision of BENa-Cl predicting the BE across all stages of CKD is the variability of the serum anion gap (SAG).

CONCLUSIONS

The BENa-Cl is not an adequate parameter for screening of hyperchloremic acidosis because of the high variability of the SAG. Only, if the BENa-Cl is ≤ 5 mmol/l, a hyperchloremic acidosis should be suspected. Therefore, a complete blood gas analysis is necessary for the correct diagnosis of acid-base disorders in patients with chronic kidney disease.

Chloride removal and bicarbonate replacement by isotonic sodium bicarbonate-based continuous hemodiafiltration: a novel method to correct severe metabolic acidosis

BACKGROUND

Previous reports highlighted the efficacy of hemofiltration utilizing isotonic sodium bicarbonate solution as replacement fluid for severe metabolic acidosis. This approach corrects metabolic acidosis by eliminating chloride and supplementing bicarbonate. Here, we present the results of an in vitro study aimed at determining the effect of Isotonic sodium bicarbonate-based Continuous HemoDiafiltration (IBB-CHDF).

METHODS

Conventional Continuous HemoDiaFiltration (CHDF) and IBB-CHDF utilized aqueous solutions mimicking blood's electrolyte composition. To assess the efficacy and safety, we compared serial changes in pH, HCO3-, Na+, and K+ concentrations. Blood flow rate was 100 mL/min, and the dialysis fluid flow rate maintained 1.0 L/h for both CHDF and IBB-CHDF. Replacement flow rates ranged from 0.5 to 1.5 L/h for CHDF and 0.1 to 1.5 L/h for IBB-CHDF.

RESULTS

At a replacement flow rate of 0.5 L/h with IBB-CHDF, bicarbonate increased from 14.7 mEq/L to within the physiological range (25.9 mEq/L), whereas in conventional CHDF, the post-treatment bicarbonate concentration did not increase (16.5 mEq/L). The maximum bicarbonate concentration achieved was 22.0 mEq/L at a replacement flow rate of 1.5 L/h in conventional CHDF. Notably, in IBB-CHDF, the sodium concentration remained constant at 150 mEq/L, 10 mEq/L higher than conventional CHDF, and did not escalate despite increasing the replacement flow rate.

CONCLUSION

IBB-CHDF effectively corrects metabolic acidosis without inducing sodium and water overload by eliminating excess chloride while providing bicarbonate.

An educational case of toluene intoxication: importance of kidney function and timing in diagnosis

Metabolic acidosis (MA) is common in daily clinical settings and requires evaluation not only by serum anion gap (AG) but also by urine AG (UAG) and urine osmolal gap (UOG) to investigate potential causes and determine appropriate treatment. Herein, we report an educational case of non-gap (normal AG) MA (pH 7.16, HCO3- 8.4, AG 11.6) with nausea and fatigue. The patient had three episodes of hospital admission with MA in the previous three months. Although serum lactate and ketone levels were negative, the AG levels were notably inconsistent (elevated or not) each time. Nevertheless, the patient was suspected to have toluene intoxication because of low UAG and high UOG levels in the non-gap acidosis phase. Eventually, he was diagnosed with toluene intoxication due to a significantly elevated urinary hippurate level (28.7 g/L) despite never admitting to using toluene. Additionally, he had a high AG only in the presence of significant kidney dysfunction, which suggests that the high AG was either due to kidney dysfunction or accumulated hippurate in the blood (when UOG was high). Thus, it should be noted that the use of serum AG alone may lead to incorrect determination of cause(s) of MA when kidney dysfunction coexists, and that UAG and UOG, in addition to AG, are necessary to determine correct diagnosis.

Quantification of Metabolic Acidosis at Bedside by S.A.L.T Approach

Introduction

Traditionally, metabolic acidosis is analyzed using an anion gap (AG). The aim of the study was to compare the utility of quantitative David Story's simplified Stewart approach against traditional approach to analyze metabolic acidosis. ICU setting. Analytical, cross-sectional observational study.

Methods

Blood gas reports of 50 adult critically ill patients with primary metabolic acidosis at admission were analyzed using both approaches. With traditional approach, acidosis was classified simply as high or normal AG acidosis. With S.A.L.T approach, the components of base deficit were further quantified into sodium chloride, albumin, lactate, and other ions effects. A contribution of sodium chloride or albumin effect of > 30% to the base deficit was considered significant. The proportion of patients with such abnormalities was determined. Descriptive statistics was used.

Results

The mean ± standard deviation (SD) age of patients was 54.52 ± 19.71 years, 52% were males, and 72% were medical admissions. The median (interquartile range [IQR]) Sequential Organ Failure Assessment score was 10 (5-13). The mean ± SD pH, bicarbonate, base excess, and albumin were 7.198 ± 0.13, 11.73 ± 4.2 mmol/L, -15.13 ± 5.6 mmol/L, and 2.9 ± 0.77 g%, respectively. The median (IQR) of serum lactate was 6.77 (1.53, 16.32) mmol/L. Hyponatremia and hypochloremia were seen in 68% and 46% of patients, respectively. Eighty-eight percent of patients had acidosis due to other ions, 52% due to lactates. Twenty-eight percent had a significant sodium chloride effect and 32% had significant hypoalbuminemia.

Conclusion

Quantification of base deficit of metabolic acidosis using S.A.L.T approach showed changes in sodium chloride levels and hypoalbuminemia affecting base deficit in nearly 30% of the patients. Quantification of metabolic acidosis using S.A.L.T approach is likely to help treat metabolic acidosis more appropriately, with clinical implications.

Renal calcification in children with renal tubular acidosis: What a paediatrician ‎should ‎know‎

Renal tubular acidosis (RTA) can lead to renal calcification in children, which can cause various complications and impair renal function. This review provides pediatricians with a comprehensive understanding of the relationship between RTA and renal calcification, highlighting essential aspects for clinical management. The article analyzed relevant studies to explore the prevalence, risk factors, underlying mechanisms, and clinical implications of renal calcification in children with RTA. Results show that distal RTA (type 1) is particularly associated with nephrocalcinosis, which presents a higher risk of renal calcification. However, there are limitations to the existing literature, including a small number of studies, heterogeneity in methodologies, and potential publication bias. Longitudinal data and control groups are also lacking, which limits our understanding of long-term outcomes and optimal management strategies for children with RTA and renal calcification. Pediatricians play a crucial role in the early diagnosis and management of RTA to mitigate the risk of renal calcification and associated complications. In addition, alkaline therapy remains a cornerstone in the treatment of RTA, aimed at correcting the acid-base imbalance and reducing the formation of kidney stones. Therefore, early diagnosis and appropriate therapeutic interventions are paramount in preventing and managing renal calcification to preserve renal function and improve long-term outcomes for affected children. Further research with larger sample sizes and rigorous methodologies is needed to optimize the clinical approach to renal calcification in the context of RTA in the pediatric population.

Alactic base excess is an independent predictor of death in sepsis: A propensity score analysis

PURPOSE

Alactic base excess (ABE) is a novel biomarker defined as the sum of lactate and standard base excess and estimates the renal capability of handling acid-base disturbances in sepsis. The objective of this study is to see if ABE is an independent predictor of mortality in septic patients with and without renal dysfunction.

MATERIALS AND METHODS

We retrospectively studied 1178 patients with sepsis and septic shock. Patients were divided according to ABE values: 1) negative ABE (<-3 mmol/L); 2) neutral ABE (≥ - 3 and < 4 mmol/L); and 3) positive ABE (≥4 mmol/L). The effect of ABE on mortality was evaluated using Cox regression weight by inverse probability weighting (IPWT) analysis after propensity score assessment. Additionally, we performed a stratified analysis in patients with GFR > 60 mL/min/1.73 m2.

RESULTS

Negative ABE patients had higher mortality than patients with neutral ABE (adjusted HR 1.43; 95%CI 1.02-2.01). Also, in patients with GFR > 60 mL/min/1.73 m2 (n = 493), we observed higher mortality in patients with negative ABE (adjusted HR 2.43; 95%CI 1.07-5.53).

CONCLUSIONS

Negative ABE is an independent predictor of in-hospital mortality in septic patients with and without renal dysfunction.

An Update on Kidney Ammonium Transport Along the Nephron

Acid-base homeostasis is critical to the maintenance of normal health. The kidneys have a central role in bicarbonate generation, which occurs through the process of net acid excretion. Renal ammonia excretion is the predominant component of renal net acid excretion under basal conditions and in response to acid-base disturbances. Ammonia produced in the kidney is selectively transported into the urine or the renal vein. The amount of ammonia produced by the kidney that is excreted in the urine varies dramatically in response to physiological stimuli. Recent studies have advanced our understanding of ammonia metabolism's molecular mechanisms and regulation. Ammonia transport has been advanced by recognizing that the specific transport of NH3 and NH₄⁺ by specific membrane proteins is critical to ammonia transport. Other studies show that proximal tubule protein, NBCe1, specifically the A variant, significantly regulates renal ammonia metabolism. This review discusses these critical aspects of the emerging features of ammonia metabolism and transport.

Strong ions and charge-balance

It has been shown that the ability to predict the pH in any chemically characterized fluid, together with its buffer-capacity and acid content can be based on the requirement of electroneutrality, conservation of mass, and rules of dissociation as provided by physical chemistry. More is not required, and less is not enough. The charge in most biological fluids is dominated by the constant charge on the completely dissociated strong ions but, nonetheless, a persistent narrative in physiology has problematized the notion that these have any role at all in acid-base homeostasis. While skepticism is always to be welcomed, some common arguments against the importance of strong ions are examined and refuted here. We find that the rejection of the importance of strong ions comes with the prize that even very simple systems such as fluids containing nothing else, or solutions of sodium bicarbonate in equilibrium with known tensions of CO₂ become incomprehensible. Importantly, there is nothing fundamentally wrong with the Henderson-Hasselbalch equation but the idea that it is sufficient to understand even simple systems is unfounded. What it lacks for a complete description is a statement of charge-balance including strong ions, total buffer concentrations, and water dissociation.

Clinical outcome and risk factors for acute fulminant myocarditis supported by venoarterial extracorporeal membrane oxygenation: An analysis of nationwide CSECLS database in China

BACKGROUND

To assess the outcomes and risk factors for adult patients with acute fulminant myocarditis (AFM) supported with venoarterial extracorporeal membrane oxygenation (VA ECMO) in China mainland.

METHODS

Data were extracted from Chinese Society of ExtraCorporeal Life Support (CSECLS) Registry database. Data from adult patients who were diagnosed with AFM and needed VA ECMO in the database were retrospectively analyzed. The primary outcome was 90-day mortality after ECMO initiation in patients with AFM supported with VA ECMO. Cox proportional hazard regression model was used to examine the risk factors associated with 90-day mortality.

RESULTS

Among 221 patients enrolled and followed up to 90 days, 186 (84.2%) patients weaned from ECMO and 159 (71.9%) patients survived and discharged home. The median age was 38 years (IQR 29-49) and males (n = 115) represented 52.0% of the total accounted patients. The median ECMO duration was 134 h (IQR 96-177 h). The main adverse event during ECMO course was bleeding (16.3%), followed by infection (15.4%). In the multivariate Cox model analysis, cardiac arrest prior to ECMO initiation (adjusted HR 2.529; 95%CI: 1.341-4.767, p = 0.004), lower pH value (adjusted HR 0.016; 95%CI: 0.010-0.059, p < 0.001) and higher lactate concentration at 24 h after ECMO initiation (adjusted HR 1.146; 95%CI: 1.075-1.221, p < 0.001) were associated with 90-day mortality.

CONCLUSIONS

71.9% patients with AFM (clinical diagnosed) supported with VA ECMO survived. Cardiac arrest prior to ECMO, lower pH and higher lactate concentration at 24 h after ECMO initiation were correlated with 90-day mortality of AFM patients supported with VA ECMO.

The association between serum anion gap and all-cause mortality of unselected adult patients: A retrospective cohort study of >20,000 patients

BACKGROUND

Even though the serum anion gap (AG) is frequently measured in clinical practice, there is not much research that has examined long-term mortality in unselected adult patients. Our study's objective was to investigate how serum anion gap levels could be used to predict death in unselected participants.

METHODS

The relationship between baseline serum AG levels and short-, intermediate-, and long-term all-cause mortality in unselected adult patients is examined using the Cox proportional risk analysis, smoothed curve fitting, subgroup analysis, and Kaplan-Meier survival curves.

RESULTS

After screening the database using the appropriate method, a total of 26,270 patients were enrolled in our study for the final data analysis. Our study used smoothed curve fit plots and COX proportional risk regression models incorporating cubic spline functions to evaluate the association between AG levels and all-cause mortality in a non-selected population, and the results indicated a non-linear relationship. In the fully adjusted model, we found that AG levels were positively associated with 30-day, 90-day, 365-day, and 4-year all-cause mortality in unselected adult patients with HRs of 1.08 95% CIs (1.06, 1.09); 1.08 95% CIs (1.06, 1.09); 1.08 95% CIs (1.07, 1.08); 1.07 95% CIs (1.06, 1.07).

CONCLUSION

Serum anion gap levels were positively correlated with all-cause mortality in unselected adult patients, with increasing levels of serum anion gap increasing patient mortality.

Fluid Stewardship of Maintenance Intravenous Fluids

Despite the frequent use of maintenance intravenous fluids (mIVF) in critically ill patients, limited guidance is available. Notably, fluid overload secondary to mIVF mismanagement is associated with significant adverse patient outcomes. The Four Rights (right drug, right dose, right duration, right patient) construct of fluid stewardship has been proposed for the safe evaluation and use of fluids. The purpose of this evidence-based review is to offer practical insights for the clinician regarding mIVF selection, dosing, and duration in line with the Four Rights of Fluid Stewardship.

Acid content and buffer-capacity: a charge-balance perspective

Rational treatment and thorough diagnostic classification of acid-base disorders requires quantitative understanding of the mechanisms that generate and dissipate loads of acid and base. A natural precondition for this tallying is the ability to quantify the acid content in any specified fluid. Physical chemistry defines the pH-dependent charge on any buffer species, and also on strong ions on which, by definition, the charge is pH-invariant. Based, then, on the requirement of electroneutrality and conservation of mass, it was shown in 1914 that pH can be calculated and understood on the basis of the chemical composition of any fluid. Herein we first show that this specification for [H⁺] of the charge-balance model directly delivers the pH-dependent buffer-capacity as defined in the literature. Next, we show how the notion of acid transport as proposed in experimental physiology can be understood as a change in strong ion difference, ΔSID. Finally, based on Brønsted-Lowry theory we demonstrate that by defining the acid content as titratable acidity, this is equal to SID_ref - SID, where SID_ref is SID at pH 7.4. Thereby, any chemical situation is represented as a curve in a novel diagram with titratable acidity = SID_ref - SID as a function of pH. For any specification of buffer chemistry, therefore, the change in acid content in the fluid is path invariant. Since constituents of SID and titratable acidity are additive, we thereby, based on first principles, have defined a new framework for modeling acid balance across a cell, a whole organ, or the whole-body.

Clinical Approach to Assessing Acid-Base Status: Physiological vs Stewart

Evaluation of acid-base status depends on accurate measurement of acid-base variables and their appropriate assessment. Currently, 3 approaches are utilized for assessing acid-base variables. The physiological or traditional approach, pioneered by Henderson and Van Slyke in the early 1900s, considers acids as H⁺ donors and bases as H⁺ acceptors. The acid-base status is conceived as resulting from the interaction of net H⁺ balance with body buffers and relies on the H₂CO₃/HCO₃^- buffer pair for its assessment. A second approach, developed by Astrup and Siggaard-Andersen in the late 1950s, is known as the base excess approach. Base excess was introduced as a measure of the metabolic component replacing plasma [HCO₃^-]. In the late 1970s, Stewart proposed a third approach that bears his name and is also referred to as the physicochemical approach. It postulates that the [H⁺] of body fluids reflects changes in the dissociation of water induced by the interplay of 3 independent variables-strong ion difference, total concentration of weak acids, and PCO₂. Here we focus on the physiological approach and Stewart's approach examining their conceptual framework, practical application, as well as attributes and drawbacks. We conclude with our view about the optimal approach to assessing acid-base status.

Increased intrarenal post-glomerular blood flow is a key condition for the development of calcineurin inhibitor-induced renal tubular acidosis in kidney transplant recipients

BACKGROUND

Hyperchloremic metabolic acidosis (HCMA) from renal tubular acidosis (RTA) is common in kidney transplant (KT) recipients. Calcineurin inhibitors (CNIs) are a potential cause of RTA, and whether HCMA is a determinant of poor graft prognosis is controversial.

METHODS

The subjects were living-donor KT recipients (LDKTRs, n = 47) and matched donors (n = 43). All cases of rejection, extrarenal causes, and respiratory disorders were excluded. HCMA was defined as having a [Na+]-[Cl- ] value of ≤34 or starting alkalization. We determined the potential causes of HCMA in LDKTRs at 3 months (m) and 1 year (y) post-KT. We examined renal hemodynamic parameters in 26 LDKTRs at 1 y post-KT: namely, glomerular filtration rate (GFR), renal plasma flow (RPF), filtration fraction (FF; GFR/RPF) and pre-/post-glomerular vascular resistance (pre-/postVR).

RESULTS

The HCMA incidence in the 3-m post-KT LDKTR group was higher than that of the donors (51.0% vs. 6.9%, p < 0.001, adjusted odds ratio: 6.7-15.7). Among adjusted factors, the most dominant HCMA contributor was low hemoglobin concentration (Hb ≤ 12 g/dl). Compared to non-HCMA cases, HCMA patients had low FF and low post-VR (p = 0.008, 0.003, respectively) suggesting increased intrarenal post-glomerular blood flow. The high pathological score of alternative arteriolar hyalinosis (aah) ≥2 was a significant HCMA risk. The tacrolimus trough level was not high in HCMA but was significantly high in HCMA in the low post-VR setting (p = 0.002).

CONCLUSION

Among LDKTRs, low hemoglobin level is an important contributor to the manifestation of HCMA in the induction period, and increased intrarenal post-glomerular blood flow is a key condition for the development of CNI-induced RTA.

Macronutrients and Micronutrients in Parenteral Nutrition for Preterm Newborns: A Narrative Review

Preterm neonates display a high risk of postnatal malnutrition, especially at very low gestational ages, because nutritional stores are less in younger preterm infants. For this reason nutrition and growth in early life play a pivotal role in the establishment of the long-term health of premature infants. Nutritional care for preterm neonates remains a challenge in clinical practice. According to the recent and latest recommendations from ESPGHAN, at birth, water intake of 70-80 mL/kg/day is suggested, progressively increasing to 150 mL/kg/day by the end of the first week of life, along with a calorie intake of 120 kcal/kg/day and a minimum protein intake of 2.5-3 g/kg/day. Regarding glucose intake, an infusion rate of 3-5 mg/kg/min is recommended, but VLBW and ELBW preterm neonates may require up to 12 mg/kg/min. In preterm infants, lipid emulsions can be started immediately after birth at a dosage of 0.5-1 g/kg/day. However, some authors have recently shown that it is not always possible to achieve optimal and recommended nutrition, due to the complexity of the daily management of premature infants, especially if extremely preterm. It would be desirable if multicenter randomized controlled trials were designed to explore the effect of early nutrition and growth on long-term health.

Hyperchloremic metabolic acidosis due to saline absorption during laser enucleation of the prostate: a case report

Background

Recent technological advancements have enabled the use of electrolyte solutions such as saline or buffered electrolyte solution during transurethral resection or laser enucleation of the prostate. However, saline absorption may cause hyperchloremic metabolic acidosis.

Case presentation

A male in his late seventies underwent holmium laser enucleation of the prostate under a combination of subarachnoid block and general anesthesia. Intraoperatively, abdominal distension prompted the attending anesthesiologist to consider the possibility of SGA malposition, and the trachea was intubated. Oropharyngeal and neck edema was observed, and laboratory examination revealed considerable acidosis with hyperchloremia. Further evaluation confirmed the absorption of a large amount of saline into the circulation via the perforated bladder. Application of the simplified Stewart approach clearly suggested that hyperchloremia was the principal cause of metabolic acidosis. The dilution of albumin attenuated acidosis.

Conclusions

Absorption of normal saline during laser enucleation of prostate caused hyperchloremic metabolic acidosis and airway edema.

Detection of COVID-19 severity using blood gas analysis parameters and Harris hawks optimized extreme learning machine

Coronavirus disease-2019 (COVID-19) has made the world more cautious about widespread viruses, and a tragic pandemic that was caused by a novel coronavirus has harmed human beings in recent years. The new coronavirus pneumonia outbreak is spreading rapidly worldwide. We collect arterial blood samples from 51 patients with a COVID-19 diagnosis. Blood gas analysis is performed using a Siemens RAPID Point 500 blood gas analyzer. To accurately determine the factors that play a decisive role in the early recognition and discrimination of COVID-19 severity, a prediction framework that is based on an improved binary Harris hawk optimization (HHO) algorithm in combination with a kernel extreme learning machine is proposed in this paper. This method uses specular reflection learning to improve the original HHO algorithm and is referred to as HHOSRL. The experimental results show that the selected indicators, such as age, partial pressure of oxygen, oxygen saturation, sodium ion concentration, and lactic acid, are essential for the early accurate assessment of COVID-19 severity by the proposed feature selection method. The simulation results show that the established methodlogy can achieve promising performance. We believe that our proposed model provides an effective strategy for accurate early assessment of COVID-19 and distinguishing disease severity. The codes of HHO will be updated in https://aliasgharheidari.com/HHO.html.

New strategies of diagnostic and therapeutic approach to emergencies in the evolution of patients with diabetes mellitus (Review)

Diabetes mellitus, known as the most widespread disease in the world, along with four other chronic diseases, involves major expenditures and significant human resources for care, thus representing a burden on any type of health care system especially due to its rapid evolution of acute and chronic complications. For the emergency department (ED), the requirements of patients with acute complications of diabetes, determine expenses which are three times higher than those for non-diabetic patients and their hospitalizations are four times more frequent. The acute complications for which patients with diabetes most frequently require the ED are hypoglycemic, hyperosmolar, or ketoacidosis coma as well as alterations of the general condition that is typical of hypoglycemia, diabetic ketoacidosis (DKA), hyperglycemic hyperosmolar state and new-onset hyperglycemia. Hypoglycemia and the Somogyi phenomenon are the most common complications of type 1 diabetes but they can also occur in patients with type 2 diabetes who are treated with insulin through its overdose. DKA can occur in type 1 and 2 diabetes either by administering inadequate doses of insulin or due to the existence of precipitating factors such as stress, acute myocardial infarction, infections, sepsis, and/or gastrointestinal bleeding. Hyperosmolar hyperglycemic status is the most common complication in patients with type 2 diabetes and DKA. Treating the acute complications of diabetes in the ED involves, besides taking immediate measures to assess and maintain vital functions, monitoring patients, assessing blood sugar, electrolytes, urea, creatinine, and bicarbonate, and applying appropriate immediate therapeutic measures for each type of acute diabetes complication.

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

Wearable sweat sensors have received significant research interest and have become popular as sweat contains considerable health information about physiological and psychological states. However, measured biomarker concentrations vary with sweat rates, which has a significant effect on the accuracy and reliability of sweat biosensors. Wearable sweat loss measuring devices (SLMDs) have recently been proposed to overcome the limitations of biomarker tracking and reduce inter- and intraindividual variability. In addition, they offer substantial potential for monitoring human body homeostasis, because sweat loss plays an indispensable role in thermoregulation and skin hydration. Previous studies have not carried out a comprehensive and systematic review of the principles, importance, and development of wearable SLMDs. This paper reviews wearable SLMDs with a new health perspective from the role of sweat loss to advanced mechanisms and designs. Two types of sweat and their measurement significance for practical applications are highlighted. Then, a comprehensive review of advances in different wearable SLMDs based on hygrometers, absorbent materials, and microfluidics is presented by describing their respective device architectures, present situations, and future directions. Finally, concluding remarks on opportunities for future application fields and challenges for future sweat sensing are presented.

Risk factors for recurrent positive results of the nucleic acid amplification test for COVID-19 patients: a retrospective study

Positive retests of COVID-19 represent a public health concern because of the increased risk of transmission. This study explored whether factors other than the nucleic acid amplification test (NAAT) contribute to positive retest results. Patients with COVID-19 admitted to the Guanggu district of the Hubei Maternal and Child Health Hospital between February 17 and March 28, 2020, were retrospectively included. The patients were grouped into the negative (n = 133) and positive (n = 51) retest groups. The results showed that the proportion of patients presenting with cough was higher (P < 0.001) and the proportion of patients with dyspnea was lower (P = 0.018) in the positive than in the negative retest group. The positive retest group showed shorter durations between symptom onset and hospitalization (P < 0.001) and symptom onset and the first positive NAAT (P = 0.033). The positive retest group had higher basophil counts (P = 0.023) and direct bilirubin (P = 0.032) and chlorine concentrations (P = 0.023) but lower potassium concentrations (P = 0.001) than the negative retest group. Multivariable regression analysis showed that coughing (OR = 7.59, 95% CI 2.28–25.32, P = 0.001) and serum chloride concentrations (OR = 1.38, 95% CI 1.08–1.77, P = 0.010) were independently associated with a positive retest result. Coughing and serum chloride concentrations were independent risk factors for positive NAAT retest results. Patients with a hospital stay of < 2 weeks or a short incubation period should stay in isolation and be monitored to reduce transmission. These results could help identify patients who require closer surveillance.

Normal saline or balanced salt solutions for fluid administration with a focus on critical care and emergency medicine settings

In an effort to expedite the publication of articles , AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

Development of a Multivariable Prediction Model for Citrate Accumulation in Liver Transplant Patients Undergoing Continuous Renal Replacement Therapy with Regional Citrate Anticoagulation

INTRODUCTION

Patients with impaired citrate metabolism may experience citrate accumulation (CA), which causes life-threatening metabolic acidosis and hypocalcemia. CA poses a challenge for clinicians when deciding on the use of regional citrate anticoagulation (RCA) for patients with liver dysfunction. This study aimed to develop a prediction model integrating multiple clinical variables to assess the risk of CA in liver transplant patients.

METHODS

This single-center prospective cohort study included postoperative liver transplant patients who underwent continuous renal replacement therapy (CRRT) with RCA. The study end point was CA. A prediction model was developed using a generalized linear mixed-effect model based on the Akaike information criterion. The predictive values were assessed using the receiver operating characteristic curve and bootstrap resampling (times = 500) to estimate the area under the curve (AUC) and the corresponding 95% confidence interval (CI). A nomogram was used to visualize the model.

RESULTS

This study included 32 patients who underwent 133 CRRT sessions with RCA. CA occurred in 46 CRRT sessions. The model included lactate, norepinephrine >0.1 μg/kg/min, alanine aminotransferase, total bilirubin, and standard bicarbonate, which were tested before starting each CRRT session and body mass index, diabetes mellitus, and chronic kidney disease as predictors. The AUC of the model was 0.867 (95% CI 0.786-0.921), which was significantly higher than that of the single predictor (p < 0.05). A nomogram visualized the prediction model.

CONCLUSIONS

The prediction model integrating multiple clinical variables showed a good predictive value for CA. A nomogram visualized the model for easy application in clinical practice.

Sodium Bicarbonate in Different Critically Ill Conditions: From Physiology to Clinical Practice

Intravenous sodium bicarbonate is commonly used in several critically ill conditions for the management of acute acidemia independently of the etiology, and for the prevention of acute kidney injury, although this is still controversial from a physiologic point of view.

Electrolyte Analysis and Replacement: Challenging a Paradigm in Surgical Patients

Postoperative patients are susceptible to alterations in electrolyte homeostasis. Although electrolytes are replaced in critically ill patients, stable asymptomatic non-intensive care unit (ICU) patients often receive treatment of abnormal electrolytes. We hypothesize there is no proven benefit in asymptomatic patients. In 2016, using the electronic medical records and pharmacy database at a university academic medical center, we conducted a retrospective cost analysis of the frequency and cost of electrolyte analysis (basic metabolic panel [BMP], ionized calcium [Ca], magnesium [Mg], and phosphorus [P]) and replacement (potassium chloride [KCl], Mg, oral/iv Ca, oral/iv P) in perioperative patients. Patients without an oral diet order, with creatinine more than 1.4, age less than 16 years, admitted to the ICU, or with length of stay of more than 1 week were excluded. Nursing costs were calculated as a fraction of hourly wages per laboratory order or electrolyte replacement. One hundred thirteen patients met our criteria over 11 months. Mean length of stay was 4 days; mean age was 54 years; and creatinine was 0.67 ± 0.3. Electrolyte analysis laboratory orders (n = 1,045) totaled $6,978, and BMP was most frequently ordered accounting for 36% of laboratory costs. In total, 683 doses of electrolytes cost the pharmacy $1,780. Magnesium was most frequently replaced, followed by KCl, P, and Ca. Nursing cost associated with electrolyte analysis/replacement was $7,782. There is little evidence to support electrolyte analysis and replacement in stable asymptomatic noncritically ill patients, but their prevalence and cost ($146/case) in this study were substantial. Basic metabolic panels, pharmacy charges for potassium, and nursing staff costs accounted for the most significant portion of the total cost. Considering these data, further research should determine whether these practices are warranted.

Use of intravenous sodium bicarbonate in neonatal intensive care units in Italy: a nationwide survey

Background

Metabolic Acidosis (MA) is a disturbance of the acid-base balance that can occur in preterm and critically ill term neonates due to different etiologies. Intravenous sodium bicarbonate (SB) has been traditionally used to correct such unbalance, despite the lack of evidence about its safety and efficacy. In literature, reported undesirable effects of treatment with SB in neonates include worsening of intracellular acidosis, impairment of myocardial function, cerebral blood flow fluctuations and intracranial hemorrhage. A national survey was conducted by the Neonatal Pharmacotherapy Study Group of the Italian Society of Neonatology with the aim to assess and describe attitudes and practices concerning the use of SB, particularly for the treatment of MA in Italian NICUs.

Methods

A questionnaire regarding treatment of MA and SB prescription habits was sent to the directors of 120 Italian NICUs from June 2017 to March 2018.

Results

The survey response rate was 97.5% (117/120 centers). Findings showed that in 55% of the surveyed NICUs (64/117 units) it is common practice to correct MA with intravenous SB. On the other hand, the remaining 45% of the units try to solve the metabolic disturbances adopting different approaches (improving perfusion, adjusting ventilation parameters or increasing blood volume). Moreover, to prevent the occurrence of MA, 37.6% of the NICUs (44/117) include buffer salts (lactate, acetate or both) in parenteral nutrition prescriptions. SB is also used as a treatment for other conditions, mainly pathologies with bicarbonate loss and tubular acidosis (respectively in 53.8 and 32.5% of the NICUs).

Conclusion

This survey showed how SB is a commonly used treatment for MA in more than half of Italian NICUs, with indications and prescription criteria that significantly vary across centers. Based on current knowledge, it is reasonable to suggest that the management of neonatal MA should be firstly directed to identify the underlying disorders. Thus, the use of SB should be reserved only for selected cases, also considering the severity of SB adverse effects and the lack of evidence about its efficacy. Guidance for the management of MA is required to harmonize practices and reduce the use of potentially inappropriate and unsafe treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-021-00955-3.

Baseline and incident hypochloremia in chronic heart failure outpatients: Clinical correlates and prognostic role

BACKGROUND

Electrolyte serum disorders are associated with poor outcome in chronic heart failure. The aim of this study sought to identify the main driver of incident hypochloremia in chronic HF (CHF) outpatients and to determine the prognostic value of baseline and incident hypochloremia.

METHODS

Consecutive CHF outpatients were enrolled and clinical, laboratoristic and echocardiographic evaluations were performed at baseline and repeated yearly in a subgroup of patients. Baseline and incident hypochloremia were evaluated. During an up to 5-year follow-up, all-cause mortality was the primary end-point for outcome.

RESULTS

Among 506 patients enrolled, 120 patients died during follow-up. At baseline, hypochloremia was present in 10% of patients and it was associated with mortality at univariate (HR: 3.25; 95%CI: 2.04-5.18; p<0.001) and at multivariate analysis (HR 2.14; 95%CI: 1.23-3.63; p: 0.005) after correction for well-established CHF prognostic markers. Among patients with repeated evaluations and without baseline hypochloremia, in 13% of these, incident hypochloremia occurred during follow-up and furosemide equivalent daily dose was its first determinant (HR for 1 mg/die: 1.008; 95%CI: 1.004-1.013; p<0.001) at forward stepwise logistic regression analysis. Finally, incident hypochloremia was associated with mortality at univariate (HR: 4.69; 95%CI: 2.69-8.19; p<0.001) as well as at multivariate analysis (HR: 2.97; 95%CI: 1.48-5.94; p: 0.002).

CONCLUSIONS

In CHF outpatients baseline and incident hypochloremia are independently associated with all-cause mortality, thus highlighting the prognostic role of serum chloride levels which are generally unconsidered. Future studies should evaluate if the strict monitoring and correction of hypochloremia could exert a beneficial effect on prognosis.

Effects of alkaline agents on respiratory characteristics in rabbit models of respiratory failure

This study aimed to investigate the effects of alkaline agents on reducing strong inspiratory effort. Rabbits with hypercapnia or lung injury, induced via repeated lung lavage following injurious ventilation, were treated with Saline, NaHCO₃, or Trometamol. In the hypercapnia, minute ventilation and tidal volume were unchanged during NaHCO₃ administration; however, one hour after the end of NaHCO₃ these parameters decreased (82.1+/-7.8 %, 90.8+/-6.0 % of the baseline, respectively, p < 0.05). Trometamol reduced minute ventilation, tidal volume, and respiratory rate after infusion (59.8+/-19.0 %, 87.0+/-9.2 %, 68.2+/-18.4 % of the baseline, respectively, p < 0.05). Alkaline agents did not cause a large change in the cerebrospinal fluid acid-base balance. In the lung injury model, NaHCO₃ and Trometamol had little effect on ventilation. However, Trometamol reduced transpulmonary pressure. Trometamol exerted more inhibitory effects on ventilation than NaHCO₃ in the hypercapnia model, and Trometamol reduced the transpulmonary pressure in the lung injury model.

Electrolyte Disorders and the Nervous System

PURPOSE OF REVIEW

This article provides an overview of the major electrolyte disorders and discusses in detail the homeostasis, etiologies, neurologic manifestations, and treatment of these disorders.

RECENT FINDINGS

The diagnosis and management of hyponatremia continue to evolve. Diagnostic accuracy is improved by assessing serum and urine osmolality as well as urinary sodium. Avoiding overcorrection of hyponatremia is crucial to avoid osmotic demyelination syndrome, although even careful correction can cause osmotic demyelination syndrome in patients who have other risk factors. The clinical presentation of osmotic demyelination syndrome has expanded, with many patients presenting with extrapontine myelinolysis in addition to central pontine myelinolysis.

SUMMARY

Electrolyte disorders often present with neurologic manifestations. Whereas disorders of some electrolytes, such as sodium, preferentially affect the central nervous system, disorders of others, such as potassium and calcium, have significant neuromuscular manifestations. An understanding of the pathophysiology of these disorders and recognition of these manifestations are crucial for the practicing neurologist as the symptoms are reversible with correct management.

Acid-base effects of continuous infusion furosemide in clinically stable surgical ICU patients: an analysis based on the Stewart model

OBJECTIVES

We sought to test the strength of correlation between predicted and observed systemic acid-base status based on the Stewart model equations during continuous infusion (CI) furosemide therapy.

DESIGN, SETTING AND PARTICIPANTS

This was a prospective, single-center, observational study conducted in the Surgical ICU of a large academic medical center. Ten critically ill patients who received CI furosemide were included.

MAIN OUTCOMES AND MEASURES

The primary purpose was to characterize the relationship between changes in serum electrolyte and acid-base status and the excretion of electrolytes in the urine during infusion of CI furosemide in critically ill patients. As a secondary endpoint, we sought to evaluate the predictive application of the Stewart model. Over 72-h, intake and output volumes, electrolyte content of fluids administered, plasma and urine electrolytes, urine pH, and venous blood gases were collected. Predicted and observed changes in acid-based status were compared for each day of diuretic therapy using Spearman's correlation coefficient.

RESULTS

The mean (SD) strong ion difference (SID) increased from 45.2 (3.2) at baseline to 49.6 (4.0) after 72 h of continuous infusion furosemide. At Day 1, the mean SID (observed) (SD) was 47.5 (3.5) and the predicted SID was 49.5 (5.8). Day 1 observed plasma SID was positively correlated with the predicted SID (r_s = 0.80, p = 0.01). By Days 2 and 3, the correlations of observed and predicted SID were no longer statistically significant.

CONCLUSIONS AND RELEVANCE

Using the Stewart model, increases in SID as an indicator of metabolic alkalosis due to the chloruretic effects of furosemide were observed. Predicted and observed SID correlated well over the first 24 h of treatment.

The arterial blood gas algorithm: Proposal of a systematic approach to analysis of acid-base disorders

Abnormalities in the acid-base balance are common clinical problems and can have deleterious effects on cellular function and be a clue to various disorders. Therefore, it is important for the clinician to make a precise diagnosis of the acid-base disorder(s) present for a proper treatment. Three approaches have been proposed to evaluate acid-base disorders: a bicarbonate-centric approach; the Stewart approach, and the base excess approach. Although the latter two have many adherents, we will only discuss the bicarbonate-centric approach. This approach is simpler to utilize at the bedside, has a physiological evaluation of the acid-base disorder, presents an easily understandable approach to assess severity, and provides a more solid foundation for the development of effective therapies. Therefore, the following discussion will be limited to an examination of this approach. In this case-centric review, important new concepts will be introduced first; their benefits and limitations discussed; and then their utilization to analyze actual cases will be shown. A systematic approach algorithm that incorporates these new concepts has been generated and will be highlighted.

Pre-treatment serum bicarbonate predicts for primary tumor control after stereotactic body radiation therapy in patients with localized non-small cell lung cancer

BACKGROUND

Tumor aggressiveness and hypoxia are linked to acidosis in the tumor microenvironment (TME). We hypothesized that low pre-treatment serum bicarbonate, potentially correlating with an acidic and hypoxic TME, predicts for poor outcomes after stereotactic body radiation therapy (SBRT) for non-small cell lung cancer (NSCLC).

METHODS

We included patients with localized NSCLC treated to a biologically effective dose (BED) ≥ 100 Gy, with available pre-treatment bicarbonate values within 3 months of treatment. We used receiver operating characteristic analysis to determine the bicarbonate concentration optimally predicting for primary tumor recurrence, and evaluated its association with recurrence and survival. We validated our findings in an independent cohort of patients from three collaborating institutions.

RESULTS

A total of 110 patients and 114 tumors were included in the training cohort, with median follow-up of 15.0 months. Bicarbonate < 26 mEq/L was associated with primary tumor recurrence on univariate (HR = 5.92; 95% CI 1.69-24.88; p = 0.005) and multivariate analysis (HR = 5.48; 95% CI 1.37-25.19; p = 0.020). The validation cohort consisted of 195 patients and 208 tumors with median follow-up of 27.5 months. In the validation cohort, bicarbonate < 26 mEq/L was again associated with primary tumor recurrence on univariate (HR = 3.38; 95% CI 1.27-9.37; p = 0.015) and multivariate analysis (HR = 3.33; 1.18-10.07; p = 0.023).

CONCLUSIONS

Pre-treatment bicarbonate predicts for primary tumor control in NSCLC treated with SBRT and may be useful for risk stratification. These findings should be confirmed prospectively.

[Interpretation of acid-base disorders]

Keeping blood pH levels stable within narrow limits is prerequisite for maintaining normal body function. Disruptions of this equilibrium can occur for a variety of reasons and may result in life-threatening conditions. Therefore, the identification and the interpretation of acid-base disorders are of great importance in emergency medicine. The same applies to intensive care as well as to almost all areas of internal medicine. In this article, we provide a practical overview of all relevant acid-base disorders that are due to both metabolic and respiratory disturbances. In addition, it shows how they can be diagnosed in everyday clinical practice by applying the simplified Stewart Approach.

Metabolomic profiling identifies novel associations with Electrolyte and Acid-Base Homeostatic patterns

Electrolytes have a crucial role in maintaining health and their serum levels are homeostatically maintained within a narrow range by multiple pathways involving the kidneys. Here we use metabolomics profiling (592 fasting serum metabolites) to identify molecular markers and pathways associated with serum electrolyte levels in two independent population-based cohorts. We included 1523 adults from TwinsUK not on blood pressure-lowering therapy and without renal impairment to look for metabolites associated with chloride, sodium, potassium and bicarbonate by running linear mixed models adjusting for covariates and multiple comparisons. For each electrolyte, we further performed pathway enrichment analysis (PAGE algorithm). Results were replicated in an independent cohort. Chloride, potassium, bicarbonate and sodium associated with 10, 58, 36 and 17 metabolites respectively (each P < 2.1 × 10-5), mainly lipids. Of all the electrolytes, serum potassium showed the most significant associations with individual fatty acid metabolites and specific enrichment of fatty acid pathways. In contrast, serum sodium and bicarbonate showed associations predominantly with amino-acid related species. In the first study to examine systematically associations between serum electrolytes and small circulating molecules, we identified novel metabolites and metabolic pathways associated with serum electrolyte levels. The role of these metabolic pathways on electrolyte homeostasis merits further studies.

Comparative analysis of acid-base balance in patients with severe sepsis and septic shock: traditional approach vs. physicochemical approach

Introduction: The evaluation of metabolism and the diagnostic classification of acid-base disorders has generated great controversy. Acid-base balance (ABB) is approached by means of the physicochemical and Henderson’s models.Objective: To compare two diagnostic approaches to ABB in patients with severe sepsis.Materials and methods: Prospective, descriptive study conducted in patients with severe sepsis. ABB was analyzed within the first 24 hours. The diagnosis was compared according to each model and the causes of the disorders were compared according to the physicochemical model.Results: 38 patients were included in the study, of which 21 (55%) were women; the mean age was 49 years, the median APACHE II, 13.28, and the mortality at 28 days, 24.3%. The traditional approach identified 8 patients with normal ABB, 20 with metabolic acidosis, and 10 with other disorders. Based on the physicochemical model, all subjects had acidosis and metabolic alkalosis. Increased strong ion difference (SID) was the most frequently observed disorder.Conclusion: The physicochemical model was useful to diagnose more patients with acid-base disorders. According to these results, all cases presented with acidosis and metabolic alkalosis; the most frequent proposed mechanism of acidosis was elevated SID. The nature of these disorders and their clinical relevance is yet to be established.

Effects of saline or albumin fluid bolus in resuscitation: evidence from re-analysis of the FEAST trial

BACKGROUND

Fluid resuscitation is the recommended management of shock, but increased mortality in febrile African children in the FEAST trial. We hypothesised that fluid bolus-induced deaths in FEAST would be associated with detectable changes in cardiovascular, neurological, or respiratory function, oxygen carrying capacity, and blood biochemistry.

METHODS

We developed composite scores for respiratory, cardiovascular, and neurological function using vital sign data from the FEAST trial, and used them to compare participants from FEAST with those from four other cohorts and to identify differences between the bolus (n=2097) and no bolus (n=1044) groups of FEAST. We calculated the odds of adverse outcome for each ten-unit increase in baseline score using logistic regression for each cohort. Within FEAST participants, we also compared haemoglobin and plasma biochemistry between bolus and non-bolus patients, assessed the effects of these factors along with the vital sign scores on the contribution of bolus to mortality using Cox proportional hazard models, and used Bayesian clustering to identify subgroups that differed in response to bolus. The FEAST trial is registered with ISRCTN, number ISRCTN69856593.

FINDINGS

Increasing respiratory (odds ratio 1·09, 95% CI 1·07-1·11), neurological (1·26, 1·21-1·31), and cardiovascular scores (1·09, 1·05-1·14) were associated with death in FEAST (all p<0·0001), and with adverse outcomes for specific scores in the four other cohorts. In FEAST, fluid bolus increased respiratory and neurological scores and decreased cardiovascular score at 1 h after commencement of the infusion. Fluid bolus recipients had mean 0·33 g/dL (95% CI 0·20-0·46) reduction in haemoglobin concentration after 8 h (p<0·0001), and at 24 h had a decrease of 1·41 mEq/L (95% CI 0·76-2·06; p=0·0002) in mean base excess and increase of 1·65 mmol/L (0·47-2·8; p=0·0070) in mean chloride, and a decrease of 0·96 mmol/L (0·45 to 1·47; p=0·0003) in bicarbonate. There were similar effects of fluid bolus in three patient subgroups, identified on the basis of their baseline characteristics. Hyperchloraemic acidosis and respiratory and neurological dysfunction induced by saline or albumin bolus explained the excess mortality due to bolus in Cox survival models.

INTERPRETATION

In the resuscitation of febrile children, albumin and saline boluses can cause respiratory and neurological dysfunction, hyperchloraemic acidosis, and reduction in haemoglobin concentration. The findings support the notion that fluid resuscitation with unbuffered electrolyte solutions may cause harm and their use should be cautioned. The effects of lower volumes of buffered solutions should be evaluated further.

FUNDING

Medical Research Council, Department for International Development, National Institute for Health Research, Imperial College Biomedical Research Centre.

[Interpretation of Arterial Blood Gas Analysis]

Interpretation of Arterial Blood Gas Analysis Abstract. Arterial blood gas test is a common diagnostic method in clinical practice. It can detect the presence and identify the causes of acid-base and oxygenation disturbances. The correct interpretation of the results begins with a careful clinical evaluation of the patient and the knowledge of the basic principles of acid-base regulation. A systematic stepwise approach is recommended to find an accurate diagnosis and to better identify mixed acid-base disorders. Here, a possible approach according to the physiological model is presented.

The Comorbidity Burden of Hidradenitis Suppurativa in the United States: A Claims Data Analysis

INTRODUCTION

Prior studies have reported that hidradenitis suppurativa (HS) is accompanied by a myriad of physical and mental conditions. However, given the small sample sizes and the limited number of pre-selected comorbidities, these studies do not provide a complete picture of the comorbidity burden of HS in the USA. Moreover, the relationship between HS severity and comorbidity burden has yet to be characterized. Using a large US claims database, we estimated the comorbidity burden associated with HS, stratified by disease severity.

METHODS

A retrospective matched cohort design was used. Patients with HS were classified into two severity cohorts (milder and more severe) using an empirical algorithm based on treatments received. The comorbidity burden was compared between each HS cohort and their matched HS-free cohort, and between patients with milder vs. those with more severe forms of HS.

RESULTS

Several physical and mental comorbidities were found to be more prevalent in both cohorts of patients with milder and more severe forms of HS than in their matched HS-free cohorts. The comorbidity burden also increased greatly as the disease progressed to more severe forms.

CONCLUSIONS

The results of this study highlight the complexity of the comorbidity burden of HS patients and the need for a multidisciplinary approach to optimize the management of HS and its numerous associated comorbidities.

FUNDING

AbbVie, Inc.

Parenteral nutrition for preterm infants: Issues and strategy

Due to transient gut immaturity, most very preterm infants receive parenteral nutrition (PN) in the first few weeks of life. Yet providing enough protein and energy to sustain optimal growth in such infants remains a challenge. Extrauterine growth restriction is frequently observed in very preterm infants at the time of discharge from hospital, and has been found to be associated with later impaired neurodevelopment. A few recent randomized trials suggest that intensified PN can improve early growth; whether or not such early PN improves long-term neurological outcome is still unclear. Several other questions regarding what is optimal PN for very preterm infants remain unanswered. Amino acid mixtures designed for infants contain large amounts of branched-chain amino acids and taurine, but there is no consensus on the need for some nonessential amino acids such as glutamine, arginine, and cysteine. Whether excess growth in the first few weeks of life, at a time when very preterm infants receive PN, has an imprinting effect, increasing the risk of metabolic or vascular disease at adulthood continues to be debated. Even though uncertainty remains regarding the long-term effect of early PN, it appears reasonable to propose intensified initial PN. The aim of the current position paper is to review the evidence supporting such a strategy with regards to the early phase of nutrition, which is mainly covered by parenteral nutrition. More randomized trials are, however, needed to further support this type of approach and to demonstrate that this strategy improves short- and long-term outcome.

Metabolic acidosis and the role of unmeasured anions in critical illness and injury

Acid-base disorders are frequently present in critically ill patients. Metabolic acidosis is associated with increased mortality, but it is unclear whether as a marker of the severity of the disease process or as a direct effector. The understanding of the metabolic component of acid-base derangements has evolved over time, and several theories and models for precise quantification and interpretation have been postulated during the last century. Unmeasured anions are the footprints of dissociated fixed acids and may be responsible for a significant component of metabolic acidosis. Their nature, origin, and prognostic value are incompletely understood. This review provides a historical overview of how the understanding of the metabolic component of acid-base disorders has evolved over time and describes the theoretical models and their corresponding tools applicable to clinical practice, with an emphasis on the role of unmeasured anions in general and several specific settings.

Role of Hypohalous Acids in Basement Membrane Homeostasis

SIGNIFICANCE

Basement membranes (BMs) are sheet-like structures of specialized extracellular matrix that underlie nearly all tissue cell layers including epithelial, endothelial, and muscle cells. BMs not only provide structural support but are also critical for the development, maintenance, and repair of organs. Animal heme peroxidases generate highly reactive hypohalous acids extracellularly and, therefore, target BMs for oxidative modification. Given the importance of BMs in tissue structure and function, hypohalous acid-mediated oxidative modifications of BM proteins represent a key mechanism in normal development and pathogenesis of disease. Recent Advances: Peroxidasin (PXDN), a BM-associated animal heme peroxidase, generates hypobromous acid (HOBr) to form sulfilimine cross-links within the collagen IV network of BM. These cross-links stabilize BM and are critical for animal tissue development. These findings highlight a paradoxical anabolic role for HOBr, which typically damages protein structure leading to dysfunction.

CRITICAL ISSUES

The molecular mechanism whereby PXDN uses HOBr as a reactive intermediate to cross-link collagen IV, yet avoid collateral damage to nearby BM proteins, remains unclear.

FUTURE DIRECTIONS

The exact identification and functional impact of specific hypohalous acid-mediated modifications of BM proteins need to be addressed to connect these modifications to tissue development and pathogenesis of disease. As seen with the sulfilimine cross-link of collagen IV, hypohalous acid oxidative events may be beneficial in select situations rather than uniformly deleterious. Antioxid. Redox Signal. 27, 839-854.

Effect of Intravenously Administered Crystalloid Solutions on Acid-Base Balance in Domestic Animals

Intravenous fluid therapy can alter plasma acid-base balance. The Stewart approach to acid-base balance is uniquely suited to identify and quantify the effects of the cationic and anionic constituents of crystalloid solutions on plasma pH. The plasma strong ion difference (SID) and weak acid concentrations are similar to those of the administered fluid, more so at higher administration rates and with larger volumes. A crystalloid's in vivo effects on plasma pH are described by 3 general rules: SID > [HCO3-] increases plasma pH (alkalosis); SID < [HCO3-] decreases plasma pH (alkalosis); and SID = [HCO3-] yields no change in plasma pH. The in vitro pH of commercially prepared crystalloid solutions has little to no effect on plasma pH because of their low titratable acidity. Appreciation of IV fluid composition and an understanding of basic physicochemical principles provide therapeutically valuable insights about how and why fluid therapy can produce and correct alterations of plasma acid-base equilibrium. The ideal balanced crystalloid should (1) contain species-specific concentrations of key electrolytes (Na+ , Cl- , K+ , Ca++ , Mg++ ), particularly Na+ and Cl- ; (2) maintain or normalize acid-base balance (provide an appropriate SID); and (3) be isosmotic and isotonic (not induce inappropriate fluid shifts) with normal plasma.

Balanced crystalloids for septic shock resuscitation

Timely fluid administration is crucial to maintain tissue perfusion in septic shock patients. However, the question concerning which fluid should be used for septic shock resuscitation remains a matter of debate. A growing body of evidence suggests that the type, amount and timing of fluid administration during the course of sepsis may affect patient outcomes. Crystalloids have been recommended as the first-line fluids for septic shock resuscitation. Nevertheless, given the inconclusive nature of the available literature, no definitive recommendations about the most appropriate crystalloid solution can be made. Resuscitation of septic and non-septic critically ill patients with unbalanced crystalloids, mainly 0.9% saline, has been associated with a higher incidence of acid-base balance and electrolyte disorders and might be associated with a higher incidence of acute kidney injury. This can result in greater demand for renal replacement therapy and increased mortality. Balanced crystalloids have been proposed as an alternative to unbalanced solutions in order to mitigate their detrimental effects. Nevertheless, the safety and effectiveness of balanced crystalloids for septic shock resuscitation need to be further addressed in a well-designed, multicenter, pragmatic, randomized controlled trial.

Hyperphosphatemia, a Cause of High Anion Gap Metabolic Acidosis: Report of a Case and Review of the Literature

Patient: Male, 74

Final Diagnosis: Metabolic acidosis due to hyperphosphatemia

Symptoms: Abdominal pain

Medication:—

Clinical Procedure: —

Specialty: Nephrology