Hypocalcaemia during rapid blood transfusion in anaesthetized man

Retrospective analysis of the effects of hypocalcemia in severely injured trauma patients

BACKGROUND

It has been suggested that the Lethal Triad be modified to include hypocalcemia, coined as the Lethal Diamond. Hypocalcemia in trauma has been attributed to multiple mechanisms, but new evidence suggests that traumatic injury may result in the development of hypoCa independent of blood transfusion. We hypothesize that hypocalcemia is associated with increased blood product requirements and mortality.

METHODS

A retrospective study of 1,981 severely injured adult trauma patients from 2016 to 2019. Ionized calcium (iCa) levels were obtained on arrival and subjects were categorized by a threshold iCa level of 1.00 mmol/L and compared. Univariable and multivariable logistic regression analysis was performed.

RESULTS

The hypocalcemia (iCa <1.00 mmol/L) group had increased rate of overall (p = 0.001), 4-hr (p = 0.007), and 24-hr (p = 0.003) mortality. There was no difference in prehospital transfusion volume between groups (p = 0.25). Hypocalcemia was associated with increased blood product requirements at 4 h (p <0.001), 24 h (p <0.001), and overall hospital length of stay (p <0.001). Logistic regression analysis showed increased odds of 4-hour mortality (OR 0.077 [95 % CI 0.011, 0.523], p = 0.009) and 24-hour mortality (OR 0.121 [95 % CI 0.019, 0.758], p = 0.024) for every mmol/L increase in iCa.

CONCLUSIONS

This study shows the association of hypoCa and traumatic injury. Severe hypoCa was associated with increased odds of early and overall mortality and increased blood product requirements. These results support the need for future prospective trials assessing the role of hypocalcemia in trauma.

Association Between Ionized Calcium Concentrations During Hemostatic Transfusion and Calcium Treatment With Mortality in Major Trauma

BACKGROUND

Transfusion of citrated blood products may worsen resuscitation-induced hypocalcemia and trauma outcomes, suggesting the need for protocolized early calcium replacement in major trauma. However, the dynamics of ionized calcium during hemostatic resuscitation of severe injury are not well studied. We determined the frequency of hypocalcemia and quantified the association between the first measured ionized calcium concentration [iCa] and calcium administration early during hemostatic resuscitation and in-hospital mortality.

METHODS

We performed a retrospective cohort study of all admissions to our regional level 1 trauma center who (1) were ≥15 years old; (2) presented from scene of injury; (3) were admitted between October 2016 and September 2018; and (4) had a Massive Transfusion Protocol activation. They also (1) received blood products during transport or during the first 3 hours of in-hospital care (1st3h) of trauma center care and (2) had at least one [iCa] recorded in that time. Demographic, injury severity, admission shock and laboratory data, blood product use and timing, and in-hospital mortality were extracted from Trauma Registry and Transfusion Service databases and electronic medical records. Citrate load was calculated on a unit-by-unit basis and used to calculate an administered calcium/citrate molar ratio. Univariate and multivariable logistic regression analyses for the binary outcome of in-hospital death were performed.

RESULTS

A total of 11,474 trauma patients were admitted to the emergency department over the study period, of whom 346 (3%; average age: 44 ± 18 years; 75% men) met all study criteria. In total, 288 (83.2%) had hypocalcemia at first [iCa] determination; 296 (85.6%) had hypocalcemia in the last determination in the 1st3h; and 177 (51.2%) received at least 1 calcium replacement dose during that time. Crude risk factors for in-hospital death included age, injury severity score (ISS), new ISS (NISS), Abbreviated Injury Scale (AIS) head, admission systolic blood pressure (SBP), pH, and lactate; all P < .001. Higher in-hospital mortality was significantly associated with older age, higher NISS, AIS head, and admission lactate, and lower admission SBP and pH. There was no relationship between mortality and first [iCa] or calcium dose corrected for citrate load.

CONCLUSIONS

In our study, though most patients had hypocalcemia during the 1st3h of trauma center care, neither first [iCa] nor administered calcium dose corrected for citrate load were significantly associated with in-patient mortality. Clinically, hypocalcemia during early hemostatic resuscitation after severe injury is important, but specific treatment protocols must await better understanding of calcium physiology in acute injury.

State-of-the-art methods for the treatment of severe hemorrhagic trauma: selective aortic arch perfusion and emergency preservation and resuscitation-what is next?

Trauma is a primary cause of death globally, with non‐compressible torso hemorrhage constituting an important part of “potentially survivable trauma death.” Resuscitative endovascular balloon occlusion of the aorta has become a popular alternative to aortic cross‐clamping under emergent thoracotomy for non‐compressible torso hemorrhage in recent years, however, it alone does not improve the survival rate of patients with severe shock or traumatic cardiac arrest from non‐compressible torso hemorrhage. Development of novel advanced maneuvers is essential to improve these patients’ survival, and research on promising methods such as selective aortic arch perfusion and emergency preservation and resuscitation is ongoing. This review aimed to provide physicians in charge of severe trauma cases with a broad understanding of these novel therapeutic approaches to manage patients with severe hemorrhagic trauma, which may allow them to develop lifesaving strategies for exsanguinating trauma patients. Although there are still hurdles to overcome before their clinical application, promising research on these novel strategies is in progress, and ongoing development of synthetic red blood cells and techniques that reduce ischemia‐reperfusion injury may further maximize their effects. Both continuous proof‐of‐concept studies and translational clinical evaluations are necessary to clinically apply these hemostasis approaches to trauma patients.

Clinicophysiological, haematobiochemical and electrocardiographic effects of homogenous and heterogenous blood transfusion in traumatized dogs

Twenty four clinical cases of dogs having the history of the accidents irrespective of their age and sex were included in this study. The definite diagnosis was made on the basis of haematobiochemical, radiographic, ultrasonographic and laparoscopic findings. The animals were divided randomly into 3 groups, viz. A, B and C comprising equal number of animals. After the definite diagnosis, patients were subjected to surgical intervention i.e. splenectomy. The animals of groups A, B, and C were subjected to the administration of anaesthetic combination of atropine sulphate, diazepam and thiopental sodium just to pass endotracheal tube followed by either isoflurane (2–2.5%) or sevoflurane (3–3.5%) and also subjected to whole blood transfusion of cattle, buffalo and dogs in groups A, B & C respectively either during the operation or just after the operation.The efficacy of blood transfusion was judged on the basis of effects on various clinicophysiological and haematobiochemical parameters recorded before and after the administration of blood. Electrocardiographic studies were also made. It was concluded that in case of the trauma of spleen, homogenous transfusion of the blood in traumatized patient is most beneficial however in case of the emergency condition, heterogenous blood transfusion from cattle and buffaloes may also be made to save the life of the patients.

Serum electrolyte imbalance and prognostic factors of postoperative death in adult traumatic brain injury patients: A prospective cohort study

Electrolyte imbalances are common in traumatic brain injury. It shares the cause of perioperative morbidity and mortality. Types of intravenous fluid resuscitation, osmotic diuretics, massive blood loss, and intracranial pathology were considered as the potential factors to worsen electrolyte abnormalities in these patients. The aims of this study were to report the incidence of electrolyte imbalance in traumatic brain injured patients and to assess the association between electrolyte imbalance and other prognostic factors to death within 24 hours of the injury.The study was carried out in the northern university, tertiary-care hospital of Thailand. The patients aged from 18 to 65 years old, presented with traumatic brain injury, and needed for emergency craniotomy were included. We excluded the patients who had minor neurosurgical procedures, pregnancy, and undergone cardiopulmonary resuscitation from the Emergency Department.Among 145 patients recruited, 101 (70%) had Glasgow Coma Scale (GCS) score ≤ 8, 25 (17%) had GCS score 9 to 12, and 19 (13%) had GCS score 13 to 15. The most common diagnosis were subdural hematoma and epidural hematoma, 51% and 36%, respectively. Hypokalemia was the most common electrolyte imbalance at 65.5%. The results of the use of a multivariable logistic regression model show that the odds of postoperative death in TBI patients were increased with high levels of blood glucose, hypernatremia, and acidosis.Hypokalemia was the most common electrolyte imbalance in TBI patients. Hypernatremia, acidosis, and hyperglycemia significantly increased the odds ratio of death in the first 24 hours post TBI.

Citrate Anticoagulation during CVVH in High Risk Bleeding Patients

Background

Regional citrate anticoagulation (RCA) is an effective form of anticoagulation for continuous renal replacement therapy (CRRT) in patients with contraindications to heparin. Its use has been very limited, possibly because of the need for special infusion solutions and difficult monitoring of the metabolic effects.

Objective

To investigate the safety and the feasibility of an RCA method for continuous veno-venous hemofiltration (CVVH) using commercially available replacement fluid.

Methods

We evaluated 11 patients at high risk of bleeding, requiring CVVH. RCA was performed using commercially available replacement fluid solutions to maintain adequate acid-base balance. We adjusted the rate of citrate infusion to achieve a post-filter ionized calcium concentration [iCa] <0.4 mmol/L when blood flow was <250 ml/min, or <0.6 mmol/L when blood flow was >250 ml/min. When needed, we infused calcium gluconate to maintain systemic plasma [iCa] within the normal range.

Results

Twenty-nine filters ran for a total of 965.5 h. Average filter life was 33.6±20.5 h. Asymptomatic hypocalcemia was detected in 6.9% of all samples. No [iCa] values <0.9 mmol/L were observed. Hypercalcemia (1.39±0.05 mmol/L) occurred in 2.5% of all samples. We observed hypernatremia (threshold 153 mmol/L) and alkalosis (threshold 7.51) in only 9.3% and 9.4% respectively of all samples, mostly concomitantly. No patient showed any signs of citrate toxicity. Conclusions: We developed a protocol for RCA during CVVH using commercially available replacement fluid that proved safe, flexible and applicable in an Intensive Care Unit (ICU) setting.

Pre-hospital transfusion of packed red blood cells in 147 patients from a UK helicopter emergency medical service

BACKGROUND

Early transfusion of packed red blood cells (PRBC) has been associated with improved survival in patients with haemorrhagic shock. This study aims to describe the characteristics of patients receiving pre-hospital blood transfusion and evaluate their subsequent need for in-hospital transfusion and surgery.

METHODS

The decision to administer a pre-hospital PRBC transfusion was based on clinical judgment. All patients transfused pre-hospital PRBC between February 2013 and December 2014 were included. Pre-hospital and in-hospital records were retrospectively reviewed.

RESULTS

One hundred forty-seven patients were included. 142 patients had traumatic injuries and 5 patients had haemorrhagic shock from a medical origin. Median Injury Severity Score was 30. 90% of patients receiving PRBC had an ISS of >15. Patients received a mean of 2.4(±1.1) units of PRBC in the pre-hospital phase. Median time from initial emergency call to hospital arrival was 114 min (IQR 103-140). There was significant improvement in systolic (p < 0.001), diastolic (p < 0.001) and mean arterial pressures (p < 0.001) with PRBC transfusion but there was no difference in HR (p = 0.961). Patients received PRBC significantly faster in the field than waiting until hospital arrival. At the receiving hospital 57% required an urgent surgical or interventional radiology procedure. At hospital arrival, patients had a mean lactate of 5.4(±4.4) mmol/L, pH of 6.9(±1.3) and base deficit of -8.1(±6.7). Mean initial serum adjusted calcium was 2.26(±0.29) mmol/L. 89% received further blood products in hospital. No transfusion complications or significant incidents occurred and 100% traceability was achieved.

DISCUSSION

Pre-hospital transfusion of packed red cells has the potential to improvde outcome for trauma patients with major haemorrhage. The pre-hospital time for trauma patients can be several hours, suggesting transfusion needs to start in the pre-hospital phase. Hospital transfusion research suggests a 1:1 ratio of packed red blood cells to plasma improves outcome and further research into pre-hospital adoption of this strategy is needed.

CONCLUSION

Pre-hospital PRBC transfusion significantly reduces the time to transfusion for major trauma patients with suspected major haemorrhage. The majority of patients receiving pre-hospital PRBC were severely injured and required further transfusion in hospital. Further research is warranted to determine which patients are most likely to have outcome benefit from pre-hospital blood products and what triggers should be used for pre-hospital transfusion.

Rapid Transfusion Devices for Hemorrhagic Cardiothoracic Trauma

Cardiothoracic trauma patients are frequently hypovolemic and hypothermic and may require massive transfusion, which can itself causesuch complications as acidosis, electrolyte imbalance (hypocalcemia and hyperkalemia), hypothermia, di lutional coagulopathy, and adultrespiratory distress syn drome. At the present time, there are a number of rapid infu sion devices such as Level I® (capable of delivering 37°C at a flow rate of up to 600 ml/min), Fluid Management System® (FMS®) (which can deliver 37.5°C of fluid at a flow rate of up to 500 ml/min), Rapid Infusion System® (RIS®) (which can pro vide up to 1,500 ml of 37°C fluid in one and one half minutes), and Rapid Solution Administration Set® (RSASO) (which can not only deliver a maximum of 2,200 m/min, but can warm the fluid to normothermia at a flow rate of 500 ml/min). However, pressurized devices such as Level IO can cause air embolism, interstitial infiltration and the compartment syndrome, and the flow rate is not operator-controlled. Devices such as FMS®, RIS®, and RSAS® incorporate a cardiotomy reservoir which has the potential for clot formation when any calcium-con taining solution is added. In this article, rapid infusion devices are compared, and complications associated with massive transfusion are described.

Aortic Hemostasis and Resuscitation: Preliminary Experiments Using Selective Aortic Arch Perfusion With Oxygenated Blood and Intra-aortic Calcium Coadministration in a Model of Hemorrhage-induced Traumatic Cardiac Arrest

OBJECTIVES

Selective aortic arch perfusion (SAAP) uses a thoracic aortic balloon occlusion catheter for heart and brain perfusion in cardiac arrest to achieve return of spontaneous circulation (ROSC). SAAP with oxygenated stored blood was studied in a model of hemorrhage-induced cardiac arrest. The study hypothesis was that intra-aortic calcium coadministration would be required to maintain normal aortic arch blood ionized calcium during SAAP and to achieve ROSC.

METHODS

Twelve anesthetized, domestic swine underwent severe hemorrhage and liver injury resulting in cardiac arrest. Whole blood and packed red blood cells (RBCs) stored in citrate anticoagulant served as perfusates for SAAP. Experiments were performed with four combinations of SAAP with oxygenated stored blood and intra-aortic calcium gluconate infusion: 1) whole blood without calcium, 2) whole blood with calcium, 3) lactated Ringers-diluted packed RBCs with calcium, and 4) normal saline-diluted packed RBCs with calcium. Aortic arch blood ionized calcium was monitored. Occurrence of ventricular dysrhythmias, success rate for ROSC, and the need for simultaneous intra-aortic calcium infusion were assessed.

RESULTS

Selective aortic arch perfusion using whole blood without intra-aortic calcium (n = 2) resulted in severe aortic blood ionized hypocalcemia, refractory ventricular fibrillation, and no ROSC. SAAP using whole blood with intra-aortic calcium (n = 4) resulted in ROSC in all four animals. Two of four developed ventricular fibrillation that was successfully defibrillated. SAAP using packed RBCs with intra-aortic calcium resulted in ROSC in all six animals, but the intra-aortic calcium dose needed to maintain normal aortic arch blood ionized calcium levels was one-third of that needed for SAAP with whole blood. Dilution of packed RBCs with lactated Ringers (n = 2) resulted in formation of small clots in the perfusion circuit which were not seen with packed RBCs diluted with normal saline (n = 4).

CONCLUSIONS

Selective aortic arch perfusion with stored whole blood or packed RBCs requires simultaneous intra-aortic calcium infusion to overcome citrate anticoagulant calcium binding, avoid refractory ventricular fibrillation, and allow for ROSC.

Citrate anticoagulation during continuous renal replacement therapy in pediatric critical care

OBJECTIVE

To provide the pediatric intensivist an in-depth understanding of citrate as regional anticoagulant during continuous renal replacement therapy.

DATA SOURCES AND DATA SELECTION

We searched the PubMed.gov database using the initial key words: citrate anticoagulation [title] AND continuous; citrate [title] AND pediatric AND continuous; prospective pediatric renal replacement AND citrate; and regional citrate anticoagulation. Additional searchers were performed using EMBASE, CINAHL, and SCOPUS with similar keywords and limits. Further articles were gathered from bibliographic references of relevant studies and reviews. Only articles published in English were reviewed.

DATA EXTRACTION AND DATA SYNTHESIS

In the pediatric population, there are no prospective interventional or randomized studies comparing regional versus systemic anticoagulation. However, there are 11 (retrospective and prospective observational studies) in the pediatric population using citrate anticoagulation. These studies have shown that regional citrate anticoagulation in the pediatric population can be effective, provide equivalent circuit survival, and decrease bleeding compared with heparin anticoagulation. In the adult population, there are six prospective randomized controlled trials comparing the efficacy of regional citrate anticoagulation versus heparin. Two systematic reviews with meta-analysis of these six trials have been performed. The adult data on the use of regional citrate anticoagulation during continuous renal replacement therapy show a decreased risk of bleeding and at the least equivalent circuit survival as compared to heparin. Current pediatric and adult studies support regional citrate anticoagulation as an effective alternative to systemic heparin anticoagulation in most patient populations.

CONCLUSIONS

Continuous renal replacement therapy is the most common modality of renal replacement in the critical care setting. Regional anticoagulation is an ideal option in a critically ill child after recent surgery or with coagulopathy. Therefore, regional citrate anticoagulation in the pediatric critical care population requiring renal replacement therapy is commonly employed. Complications of citrate anticoagulation can be avoided with a greater understanding of the properties and clearance of citrate. Continued reporting of observational data and the development of prospective multicenter trials using citrate anticoagulation are needed to ensure safe and standardized care in the pediatric population.

Effects of Liver Function on Ionized Hypocalcaemia following Rapid Blood Transfusion

OBJECTIVE: Hypocalcaemia detrimentally affects the cardiovascular system and massive transfusion-related hypocalcaemia is particularly severe in end-stage liver disease patients undergoing liver transplantation (LT). This study, therefore, compared the severity and duration of ionized hypocalcaemia between patients with normal and impaired liver function. METHODS: Patients ( n = 26 per group) were transfused at a rate of 10 ml/kg within 10 min with packed red blood cells (PRBCs) during LT (group LP) or spinal surgery (group SP), or were infused with 0.9% normal saline during spinal surgery (group SN). Serum levels of ionized calcium were assessed before (T0), just after (T1), and at 20 (T2) and 60 min (T3) after transfusion. RESULTS: Transfusion with PRBCs caused more severe ionized hypocalcaemia than 0.9% normal saline at T1. In contrast to the faster (20 min) normalization in group SP, ionized hypocalcaemia in group LP persisted at T3. Serum ionized calcium levels at T3 showed correlations with vital signs, blood glucose, serum potassium, base deficit and lactate. CONCLUSION: Rapid blood transfusion caused more severe and prolonged ionized hypocalcaemia in patients with liver dysfunction than in those with normal liver function.

Incidence of ionized hypocalcemia in septic dogs and its association with morbidity and mortality: 58 cases (2006-2007)

OBJECTIVE

To determine the incidence rate and prognostic significance of ionized hypocalcemia (iHCa) among septic dogs.

DESIGN

Retrospective study.

SETTING

Veterinary teaching hospital.

ANIMALS

Fifty-eight septic dogs that were presented to Cornell University Hospital for Animals between January 2006 and December 2007.

PROCEDURE

Cases were diagnosed with sepsis if they exhibited 2 or more criteria of the systemic inflammatory response syndrome with a concurrent documented infectious focus. Cases were excluded if diagnosed with a concurrent illness reportedly associated with calcium derangements. Lowest, mean, and highest blood ionized calcium concentrations were recorded and statistically analyzed for an association with morbidity, as measured by duration of hospitalization and number of blood product transfusions, and outcome. In addition, the incidence rate of iHCa was recorded.

RESULTS

Of the 58 cases included in this study, iHCa was documented in 4 of 6 (67%) patients that died, 5 of 19 (26%) euthanized patients and 5 of 33 (15%) patients that survived to discharge, with an overall incidence of 24%. Dogs that died during hospitalization had more severe iHCa than patients that were discharged or euthanized as well as significantly lower mean ionized calcium concentrations than patients who were discharged. Severity of iHCa was also associated with a longer duration of hospitalization. The highest ionized calcium concentration was not associated with outcome.

CONCLUSION AND CLINICAL RELEVANCE

This study is the first to document the incidence of iHCa among septic dogs. Because both low mean ionized calcium and the lowest documented ionized calcium concentration are associated with poor outcome, it is likely that both the severity and duration of hypocalcemia are important in these patients. Further prospective studies investigating the prognostic significance, etiology and treatment of iHCa among septic veterinary patients are needed to better understand its role in sepsis.

The value of initial ionized calcium as a predictor of mortality and triage tool in adult trauma patients

Ionized hypocalcemia is a common finding in critically ill patients, but the relationship between ionized hypocalcemia and mortality risk in trauma patients has not been well established. The aim of this study was to assess the usefulness of initial ionized calcium (iCa) in predicting mortality in the trauma population, and evaluate its superiority over the three other triage tools: base deficit, systemic inflammatory response syndrome (SIRS) score, and triage-revised trauma score (t-RTS). A pro-and retrospective study was performed on 255 consecutive trauma patients admitted to our Emergency Medical Center from January to December, 2005, who underwent arterial blood gas analysis. Multivariate logistic regression analysis confirmed iCa (<or=0.88 mM/L), low Glasgow coma scale score, and a large transfusion amount to be significant risk factors associated with mortality (p<0.05). The sensitivities of iCa, base deficit, SIRS score, and t-RTS were 82.9%, 76.4%, 67.1%, and 74.5%, and their specificities were 41.0%, 64.1%, 64.1%, and 87.2%, respectively. Receiver operating characteristic curve analysis determined the areas under the curves of these parameters to be 0.607+/-0.062, 0.736+/-0.056, 0.694+/-0.059, and 0.875+/-0.043, respectively (95% confidence interval). Although initial iCa (<or=0.88 mM/L) was confirmed as a significant risk factor associated with mortality, it exhibited a poorer discriminative power for mortality prediction than other predictors, especially t-RTS.

Cardiac arrests associated with hyperkalemia during red blood cell transfusion: a case series

BACKGROUND

Transfusion-associated hyperkalemic cardiac arrest is a serious complication of rapid red blood cell (RBC) administration. We examined the clinical scenarios and outcomes of patients who developed hyperkalemia and cardiac arrest during rapid RBC transfusion.

METHODS

We retrospectively reviewed the Mayo Clinic Anesthesia Database between November 1, 1988, and December 31, 2006, for all patients who developed intraoperative transfusion-associated hyperkalemic cardiac arrest.

RESULTS

We identified 16 patients with transfusion-associated hyperkalemic cardiac arrest, 11 adult and 5 pediatric. The majority of patients underwent three types of surgery: cancer, major vascular, and trauma. The mean serum potassium concentration measured during cardiac arrest was 7.2 +/- 1.4 mEq/L (range, 5.9-9.2 mEq/L). The number of RBC units administered before cardiac arrest ranged between 1 (in a 2.7 kg neonate) and 54. Nearly all patients were acidotic, hyperglycemic, hypocalcemic, and hypothermic at the time of arrest. Fourteen (87.5%) patients received RBC via central venous access. Commercial rapid infusion devices (pumps) were used in 8 of 11 (72.7%) of the adult patients, but RBC units were rapidly administered (pressure bags, syringe pumped) in all remaining patients. Mean resuscitation duration was 32 min (range, 2-127 min). The in-hospital survival rate was 12.5%.

CONCLUSION

The pathogenesis of transfusion-associated hyperkalemic cardiac arrest is multifactorial and potassium increase from RBC administration is complicated by low cardiac output, acidosis, hyperglycemia, hypocalcemia, and hypothermia. Large transfusion of banked RBCs and conditions associated with massive hemorrhage should raise awareness of the potential for hyperkalemia and trigger preventative measures.

Tolerable infusion rate of citrate based on clinical signs and the electrocardiogram in conscious dogs

BACKGROUND & AIMS

The possible clinical significance of the toxic effects of citrate has not yet been fully clarified. This study was therefore conducted to confirm the toxicity and determine the tolerable infusion rate of citrate administered by rapid intravenous infusion to conscious dogs.

METHODS

Citrate solutions were infused via the cephalic vein of 4 conscious dogs at 0.33, 0.67, or 1.33mmol/kg/h up to 1.33mmol/kg. Clinical signs and the electrocardiogram were observed during and after infusion. Serum citrate and ionized calcium levels were also measured.

RESULTS

Although the mean citrate level increased in accordance with the infusion rate, the calcium level decreased. No significant changes in clinical signs or the electrocardiogram were observed during infusion at 0.33mmol/kg/h despite an increase in the serum citrate level to 1.22+/-0.11mmol/l (pre-infusion value: 0.38+/-0.01mmol/l) and a decrease in the serum calcium level to 1.28+/-0.03mmol/l (pre-infusion value: 1.50+/-0.05mmol/l). Vomiting and QTc prolongation were observed at 0.67mmol/kg/h or higher. Salivation and tachycardia were observed at 1.33mmol/kg/h.

CONCLUSIONS

Based on clinical signs and the electrocardiogram, the tolerable infusion rate of citrate in conscious dogs is concluded to be 0.33mmol/kg/h.

Regional citrate anticoagulation during simulated treatments of sustained low efficiency diafiltration

Renal replacement therapy is frequently required for critically ill patients with a high risk of bleeding. Conventional heparinization strategies to prevent extracorporeal blood circuit clotting can cause significant haemorrhage in such patients because of systemic anticoagulation. Regional citrate anticoagulation (RCA) is a well-established technique that minimizes this complication by the decalcification of blood in the extracorporeal circuit such that it is incapable of clotting. To date, there are no reports on the use of RCA for sustained low-efficiency dialysis/diafiltration (SLED), a hybrid therapy that involves the use of conventional haemodialysis machinery to deliver lower solute clearances over prolonged periods of time. In preparation for clinical study, an in vitro simulation of SLED was devised (blood substitute flow 250 mL/min, dialysate flow 200 mL/min, predilution haemofiltration 100 mL/min). Blood substitute was decalcified by an infusion of 4% trisodium citrate (TSC) proximally into the extracorporeal blood circuit, with partial restoration of calcium homeostasis from dialysate containing ionized [Ca2+] at 0.9 mmol/L. This simulation was used to establish first the 4% TSC requirement for therapeutic decalcification, and second the associated changes in ionized [Ca2+] and [Mg2+] within the blood substitute from chelation with citrate and subsequent removal of the resulting divalent cation-citrate complex. Serial measurements of blood substitute [Ca2+] from strategic points along the extracorporeal circuit showed therapeutic decalcification was not achieved with 4% TSC infusion rates up to 400 mL/h, and extrapolation of experimental results suggests that 450 mL/h will be required. Under these conditions, ionized [Ca2+] and [Mg2+] in the blood substitute venous return and would be 0.42 and 0.2 mmol/L, respectively, with 0.35 mmol of citrate being returned per minute via the blood substitute venous return. These results were modelled for various changes in SLED operating parameters, and discussed in detail. An appropriate regimen for 4% TSC infusion and divalent cation replacement is proposed for clinical study in the future.

Damage control surgery and intensive care

The introduction and establishment of the 'damage control surgery' concept has led to increasing numbers of severely injured and unstable patients being presented to Intensive Care Units (ICU) for ongoing resuscitation. These patients present many challenges for the Intensive Care team and emphasise the need for a multidisciplinary approach to optimise trauma patient management. Multiple issues need to be addressed simultaneously while the overall aim is to rapidly achieve a physiological environment that will allow the best possible recovery. The 'lethal triad' of hypothermia, acidosis, and coagulopathy due to initial hypovolaemia require aggressive correction. From the outset ICU management must also attempt to minimise the complications of these injuries and the resuscitative process. This review will address some of the key issues relating to the care of these patients in the ICU.

Serum levels of calcium and albumin in survivors versus nonsurvivors after critical injury

PURPOSE

Injured patients who require aggressive resuscitation with intravenous (IV) fluids and blood products will frequently acquire low levels of serum calcium (CA) and albumin (ALB) in the intensive care unit (ICU) as result of this therapy. The purpose of this longitudinal study was to determine the time course of CA and ALB during ICU admission in survivors (S) compared to nonsurvivors (N) after major trauma. The study design is to verify if CA, ALB, or albumin-corrected CA can be used as indicators of patient survivability after critical injury.

MATERIALS AND METHODS

CA and ALB values were retrospectively recorded in 64 random subjects (S= 32 and N= 32) admitted to the Trauma ICU for 3 or more days. CA and ALB data points were partitioned into 6 time frames of ICU care. Mean values and standard error of the mean for each frame were obtained to depict parametric differences in the time profiles for S versus N. Subgroup analysis was used to determine the impact of blood transfusions on CA and ALB levels. Albumin-corrected CA was computed for every patient at each measurement point and then partitioned into the 6 time frames of ICU care. Parametric t-test and nonparametric rank sum analysis were used to evaluate the ability of CA, ALB, and ALB-corrected CA at discriminating S from N. Each predictive covariate was ranked, divided into quartiles (grades = normal, mild, moderate, severe), and correlated with patient survival likelihood (viz., ratio of S to N in each quartile).

RESULTS

Parametric and non-parametric analysis of collected data indicates that the response patterns of CA were significantly different ( P<.00005 ) in S versus N. Time profiles of CA and ALB exhibited similar reductions in both S and N during the resuscitation phase (ie, "hypocalcemia of trauma"). But from these nadir points, CA response patterns in S tended to steadily elevate toward normal levels (ie, "responders"), while N exhibited no such increase in CA values (ie, "nonresponders"). Data revealed that survival likelihood in trauma patients after 3 ICU days is proportional to the upward response of CA from depressed values present after the initial resuscitation. Decreased CA levels after 3 ICU days were associated with decreased survival (Table 1). Rank sum testing showed that values of CA corrected for ALB creates less obvious difference in S and N than uncorrected CA. Subgroup analysis showed a linear decrease in CA and ALB levels with increasing units of blood transfused during treatment for trauma.

CONCLUSIONS

CA changes during ICU care demonstrate distinct response patterns (P <.00005) for survivors versus nonsurvivors. The magnitude of upward response in CA after the fluid resuscitation phase is a marker that correlates with a patient's ability to withstand the physiologic stresses encountered during ICU treatment after major trauma. Our findings indicate that uncorrected CA values are a better guide for calcium replacement therapy in trauma patients than albumin-adjusted CA. This study suggests that response patterns of CA can be a useful reference to aid in monitoring the progress of critically injured patients.

Citrate pharmacokinetics and metabolism in cirrhotic and noncirrhotic critically ill patients

OBJECTIVES

To investigate pharmacokinetics and metabolism of sodium citrate in critically ill patients. To determine the risk of citrate accumulation in the setting of liver dysfunction (cirrhosis, hepatorenal syndrome).

DESIGN

Prospective cohort study.

SETTING

Intensive Care Unit, Department of Medicine IV, University Hospital Vienna.

PATIENTS

Consecutive critically ill cirrhotic (n = 16) and noncirrhotic patients (n = 16).

INTERVENTIONS

Infusion of sodium citrate (0.5 mmol.kg-1.hr-1) and calcium chloride (0.17 mmol.kg-1.hr-1) for 2 hrs. Analysis of serial arterial blood samples.

MEASUREMENTS AND MAIN RESULTS

Total body clearance of citrate was normal in noncirrhotic critically ill patients but significantly reduced in cirrhotic patients (710 vs. 340 mL/min, p =.008). Citrate peak concentrations and concentration over time were increased by 65% and 114% in cirrhotic patients (p <.001), respectively; volumes of distribution were similar. Net metabolic changes were quantitatively similar, with pH and plasma bicarbonate concentrations increasing more slowly in cirrhotic patients. No citrate-related side effects were noted. Citrate clearance could not be predicted by standard liver function tests and was not appreciably influenced by renal function and Acute Physiology and Chronic Health Evaluation II scores.

CONCLUSIONS

This first systematic study on citrate pharmacokinetics and metabolism in critically ill patients confirms a major role of hepatic citrate metabolism by demonstrating reduced citrate clearance in cirrhotic patients. Pharmacokinetic data could provide a basis for the clinical use of citrate anticoagulation in critically ill patients. Provided dose adaptation and monitoring of ionized calcium, citrate anticoagulation seems feasible even in patients with decompensated cirrhosis. Metabolic consequences of citrate infusion were not different between groups in this study but may be more pronounced in prolonged infusion.

Increased total to ionized calcium ratio during continuous venovenous hemodialysis with regional citrate anticoagulation

BACKGROUND

Citrate anticoagulation is commonly used for continuous venovenous hemodialysis (CVVHD) to minimize the risk of bleeding complications. We have previously reported a liver failure patient undergoing citrate-based CVVHD with elevated serum total to ionized calcium ratio. Diminished liver metabolism of citrate with resultant elevated systemic citrate was thought to be the cause.

METHODS

To determine the incidence and clinical significance of an elevated total to ionized calcium ratio during citrate-based CVVHD, 161 patients undergoing citrate-based CVVHD were screened for the presence of an elevated total to ionized calcium ratio (the subset with increased total to ionized calcium ratio comprised the study group). Because all patients in the study group had liver failure, two control groups of patients with normal total to ionized calcium ratios were formed-those without liver failure (control I) and those with liver failure (control II).

RESULTS

An elevated total to ionized calcium ratio was detected in 12% of all patients. Thirty-three percent of liver failure patients demonstrated an elevated total to ionized calcium ratio. The study group demonstrated significantly higher mean total calcium levels, significantly lower mean ionized calcium levels, and significantly higher mean total to ionized calcium ratios than controls. As a result, the study group also had significantly increased mean calcium chloride replacement requirements in comparison with controls. The mean calcium to citrate infusion ratio was elevated in the study group in comparison with controls. An elevated total to ionized calcium ratio was associated with increased mortality in comparison with controls. No patients suffered complications from ionized hypocalcemia or elevated serum total calcium.

CONCLUSIONS

Systemic citrate accumulation as evidenced by an elevated total to ionized calcium ratio occurs commonly in patients requiring CVVHD using citrate-based regional anticoagulation. Observing changes in the total to ionized calcium ratio can aid in early detection of patients with hepatic failure who are unable to appropriately metabolize citrate and will require calcium chloride infusion rates significantly above normal.

Hypocalcemia: a pervasive metabolic abnormality in the critically ill

Hypocalcemia has been reported in critically ill patients, most commonly in association with sepsis syndrome. However, the severity and incidence of hypocalcemia in nonseptic but critically ill patients has not been well defined. Therefore, the goal of this study was to identify and compare the frequency and degree of hypocalcemia in critically ill patients with differing underlying illnesses (those admitted to medical, surgical, trauma, neurosurgical, burn, respiratory, and coronary intensive care units [ICUs]; group A; n = 99). Results were compared with the frequency and degree of hypocalcemia in non-critically ill ICU patients (initially admitted to an ICU but discharged within 48 hours; group B; n = 50) or hospitalized non-ICU patients (group C; n = 50). Incidences of hypocalcemia (ionized calcium [Ca] < 1.16 mmol/L [less than normal]) were 88%, 66%, and 26% for groups A, B, and C, respectively (P: < 0.001). In group A, the frequency of hypocalcemia did not depend on the ICU setting or presence of sepsis. However, the occurrence of hypocalcemia correlated with both Acute Physiology and Chronic Health Evaluation II score (r = -0.39; P: < 0.001) and patient mortality (eg, hazard ratio for death, 1.65 for Ca decrements of 0.1 mmol/L; P: < 0.002). Hypomagnesemia, number of blood transfusions, and presence of acute renal failure were each associated with depressed Ca levels. A weak association (r = -0.12; P: = 0.09) was noted between serum Ca level and QT interval. Clinical concern stemming from hypocalcemia was underscored by the substantial use of intravenous (IV) Ca therapy ( approximately 2 to 3 g IV). We conclude that hypocalcemia is extremely common in hospitalized patients (up to 88%) and correlates with severity of illness, but not with a specific illness per se. Whether it directly impacts patient survival remains unknown. Resolution of this issue appears to be critical because of the frequency with which it leads to high-dose IV Ca therapy.

Hypocalcaemia in severe meningococcal infections

AIM

To determine the incidence of hypocalcaemia in critically ill children with meningococcal disease.

METHODS

In a prospective cohort study, 70 of 80 patients admitted consecutively with a clinical diagnosis of meningococcal disease to intensive care had measurements of total and ionised calcium on admission. Parathormone and calcitonin were measured in a proportion of the children.

RESULTS

Total and ionised calcium concentrations were low in 70% of the children. There was a weak relation of calcium concentration to the volume of blood derived colloid which had been given, but a good relation to disease severity, where sicker children had lower calcium concentrations. Although the parathormone concentration was higher in children with lower calcium concentrations, some children had low ionised calcium concentrations, without an increase of parathormone concentration. Serum calcitonin concentration was not related to calcium concentrations.

CONCLUSION

Hypocalcaemia is common in meningococcal disease.

Pulmonary calcifications: a review

Pulmonary calcification is a common asymptomatic finding, usually discovered on routine chest X-ray or at autopsy. Pulmonary calcifications are caused mainly by two mechanisms: the dystrophic form and the metastatic form (1). Despite the different aetiologies, the pulmonary function and clinical manifestations are quite similar in both forms. We present a review of the clinical and radiology findings of the different aspects of pulmonary calcifications according to its pathogenesis and its anatomic distribution: parenchymal, lymphe node and pleural.

Comparison of Adsol and CPDA-1 blood preservatives during simulated massive resuscitation after hemorrhage in swine

BACKGROUND

In recent years, there has been a change from the use of blood stored in CPDA-1 to the use of red cells (RBCs) stored in electrolyte mixtures, such as Adsol (AS-1 RBCs). However, because Adsol contains mannitol, as well as increased amounts of glucose relative to CPD and CPDA-1, concerns have been expressed as to possible harmful effects (recipient hyperglycemia, inappropriate osmotic diuresis) that it might induce under conditions of massive RBC transfusion.

STUDY DESIGN AND METHODS

A hemorrhagic shock animal model was used to evaluate the effects of large-volume infusion of CPDA-1 or Adsol on glucose homeostasis and on urinary output under conditions that were devoid of extensive surgical manipulation. Hemorrhage was induced in 10 female Pitman-Moore mini-pigs to maintain mean arterial blood pressure at 55 mmHg for 90 minutes. After the return of autologous RBCs plus 1 L of 0.9-percent sodium chloride, the animals were given solution equivalent to the solute load in either 20 units of CPDA-1 whole blood (63 mL x 20 = 1260 mL) or 20 units of AS-1 RBCs (100 mL x 20 = 2000 mL) over a period of 90 minutes. Animals were monitored to determine physiologic and blood chemical responses to infusion of the solutions and to determine if there was hyperglycemia or inappropriate diuresis in the Adsol-treated group.

RESULTS

Animals that received CPDA-1 developed significant hypocalcemia, arterial hypotension, and elevated blood glucose concentrations; two of five animals died of circulatory collapse. In contrast, glucose metabolism in the Adsol recipients was well-regulated, serum ionized calcium concentration was not significantly altered, and all animals survived. No evidence of inappropriate diuresis was observed.

CONCLUSION

Administration of large amounts of Adsol was not associated with hyperglycemia or inappropriate osmotic duiresis in hemorrhaged and resuscitated minipigs. These data suggest that fewer physiologic changes may be associated with the massive transfusion of AS-1 RBCs than with that of CPDA-1 whole blood.

Hextend, a physiologically balanced plasma expander for large volume use in major surgery: a randomized phase III clinical trial. Hextend Study Group

Hextend (BioTime, Inc., Berkeley, CA) is a new plasma volume expander containing 6% hetastarch, balanced electrolytes, a lactate buffer, and physiological levels of glucose. In preclinical studies, its use in shock models was associated with an improvement in outcome compared with alternatives, such as albumin or 6% hetastarch in saline. In a prospective, randomized, two-center study (n = 120), we compared the efficacy and safety of Hextend versus 6% hetastarch in saline (HES) for the treatment of hypovolemia during major surgery. Patients at one center had a blood sample drawn at the beginning and the end of surgery for thromboelastographic (TEG) analysis. Hextend was as effective as HES for the treatment of hypovolemia. Patients received an average of 1596 mL of Hextend: 42% received >20 mL/kg up to a total of 5000 mL. No patient received albumin. Hextend-treated patients required less intraoperative calcium (4 vs 220 mg; P < 0.05). In a subset analysis of patients receiving red blood cell transfusions (n = 56; 47%), Hextend-treated patients had a lower mean estimated blood loss (956 mL less; P = 0.02) and were less likely to receive calcium supplementation (P = 0.04). Patients receiving HES demonstrated significant prolongation of time to onset of clot formation (based on TEG) not seen in the Hextend patients (P < 0.05). No Hextend patient experienced a related serious adverse event, and there was no difference in the total number of adverse events between the two groups. The results of this study demonstrate that Hextend, with its novel buffered, balanced electrolyte formulation, is as effective as 6% hetastarch in saline for the treatment of hypovolemia and may be a safe alternative even when used in volumes up to 5 L.

IMPLICATIONS

Hextend (BioTime, Inc., Berkeley, CA) is a new plasma volume expander containing 6% hetastarch, balanced electrolytes, a lactate buffer, and a physiological level of glucose. It is as effective as 6% hetastarch in saline for the treatment of hypovolemia but has a more favorable side effects profile in volumes of up to 5 L compared with 6% hetastarch in saline.

Unexpected severe hypocalcemia during continuous venovenous hemodialysis with regional citrate anticoagulation

Citrate is known to induce acute hypocalcemia in patients undergoing liver transplantation during the anhepatic phase. We describe the case of a 71-year-old woman with fulminant hepatic failure secondary to hepatitis A, who was started on continuous venovenous hemodialysis (CVVHD) for acute renal failure. Because anticoagulation with heparin was untenable, regional anticoagulation was accomplished by trisodium citrate (46.7%) infusion. Unfortunately, severe hypocalcemia developed when citrate accumulated because of impaired hepatic metabolism. Because of chelation by citrate, the ionized calcium concentration declined to values as low as 2.72 mg/dL (normal, 4.5 to 5.6 mg/dL), whereas the total calcium concentration remained in the normal range. With an unusually high calcium chloride infusion rate via a central line (up to 140 mL/h of 10 mEq/dL CaCl2) and additional boli of CaCl2 (for a total of 190 mEq), the ionized calcium concentration could be maintained at target levels. Nevertheless, the ionized calcium concentration was maintained in the normal range, and the total calcium concentration increased to a value as high as 15 mg/dL. Thus, the total to ionized calcium ratio was 3.5:1. After 24 hours of treatment, trisodium citrate infusion was gradually reduced from 15 mL/h to 7 mL/h, and the calcium chloride infusion was decreased to 50 mL/h. Nevertheless, persistence of the elevated total to ionized calcium ratio (3:1) indicated citrate accumulation likely secondary to decreased hepatic metabolism. Using this approach, the patient was successfully maintained on CVVHD with regional citrate anticoagulation for a total of 11 days without any additional complications. We conclude that CVVHD with regional citrate anticoagulation can be used in patients with acute hepatic failure if increased CaCl2 requirements are anticipated and if citrate is infused at a lower rate compatible with decreased citrate metabolism. Citrate accumulation should be suspected in patients with an elevated total to ionized Ca++ ratio during CVVHD with citrate anticoagulation.

Replacement of massive blood loss

Treatment of massive blood loss has experienced major changes during the recent decade. The transition towards pure component therapy has been the most significant issue, which has compelled the clinician to revise some of their basic strategies in treatment of massively bleeding patients. The importance of adequate volume resuscitation with crystalloids and colloids is still unrefutable, but the therapy of hemorrhagic derangements has changed. Plasma-poor red cells (RC) are now commonly used instead of whole blood (WB) or packed red blood cells (PRBC) to correct oxygen carrying capacity during massive blood loss. As the plasma content of RC is minimal, deficit of plasma and coagulation factors develops earlier than during transfusion of WB and PRBC. Hypofibrinogenemia develops first followed by other coagulation factor deficits and later by thrombocytopenia. Therefore the use of fresh frozen plasma (FFP) is the primary intervention to treat abnormal bleeding encountered in the replacement of massive blood loss with RC. As the development of thrombocytopenia is a highly individual phenomenon, the transfusion of platelets should be guided by repeatedly determined platelet counts.

Calcium administration for cardiovascular support in critically ill patients: when is it indicated?

Calcium has a fundamental role in the maintenance of myocardial function and vascular tone. The ionized form of calcium is the most important physiologically, and this form needs to be measured to assess physiologically active calcium levels. Ionized hypocalcemia can occur as a result of various pathophysiological disturbances, and it is seen frequently in critically ill patients. Several investigators have observed a poorer prognosis in those patients with ionized hypocalcemia. It is unclear whether calcium supplementation is beneficial in these patients. It may improve cardiovascular performance, but, in contrast, it may contribute to cellular damage (especially during hypoxia following cardiopulmonary resuscitation). In sepsis, there may be an increased cellular influx of calcium, which may be deleterious to cellular function; indeed, calcium entry blockers in this situation may be protective. We review the role of calcium as an inotropic agent, its interaction with other inotropic agents, and its use during blood transfusion and during cardiopulmonary resuscitation.

Fatal myocardial depression and circulatory collapse associated with complement activation induced by plasma infusion in severe porcine sepsis

We have previously reported that fresh frozen plasma (FFP) may induce a rapid irreversible shock when repeatedly infused in pigs challenged with Gram-negative sepsis. The aims of the present study were to elucidate the cardiovascular nature of the shock and determine the aetiologic role of tumour necrosis factor (TNF), complement activation and halothane anaesthesia. Three groups of anaesthetized piglets were inoculated with a lethal dose of live E. coli bacteria. Groups I (n = 8) and III (n = 8) were anaesthetized with halothane and group II (n = 8) with ketamine. Animals in groups I and II received repeated infusions of FFP, whereas animals in group III received repeated infusions of 7% albumin. Six animals in group I and four animals in group II died during the first plasma infusion. Survival time was significantly longer in group II (P = 0.04) compared to group I. No animals in group III died during the albumin infusions, and no adverse effects were observed during the infusions. In group I the plasma induced shock was characterized by abruptly falling mean arterial pressure, cardiac index, systemic vascular resistance index and left ventricular contractility. Concomitant increases were recorded in left ventricular filling pressure and central venous pressure. Group II demonstrated a similar, but delayed response. Plasma infusion was associated with a significant increase in terminal complement complex (TCC) (P < 0.03 in group I, P < 0.05 in group II) and depletion of serum ionized calcium. We conclude that FFP may induce fatal myocardial depression and circulatory collapse in severe sepsis. Complement activation may be of aetiologic importance.

Hypocalcemic emergencies

Chronic hypocalcemia occurs frequently, although emergent hypocalcemia does not. When hypocalcemia is suspected, verification of ionized hypocalcemia is required and an etiopathologic search warranted. Etiology-specific therapy is suggested, although at times emergent intravenous calcium is indicated. Long-term nonspecific therapy includes oral calcium and vitamin D supplementation.

Hypercalcitoninemia and hypocalcemia in acutely ill children: studies in serum calcium, blood ionized calcium, and calcium-regulating hormones

We studied the hypotheses that serum calcium and blood ionized calcium would be low in acutely ill children and would rise with clinical improvement. In 15 children admitted to the pediatric intensive care unit, the blood ionized calcium level was 4.45 +/- 0.06 mg/dl (1.11 +/- 0.015 mmol/L) on entry versus 5.17 +/- 0.03 mg/dl (1.29 +/- 0.01 mmol/L) in control subjects (p less than 0.005), rose significantly on days 2 and 3, and was 5.12 +/- 0.04 mg/dl (1.28 +/- 0.01 mmol/L) at discharge (p less than 0.005). Changes in serum calcium level were similar, whereas serum magnesium and phosphorus levels were normal and did not change. Basal serum parathyroid hormone concentrations were elevated, rose further during the study, and were normal at discharge. Serum parathyroid hormone levels correlated inversely with blood ionized calcium levels, indicating that compensatory hyperparathyroidism occurs with low blood ionized calcium concentrations. Basal serum calcitonin values were evaluated on entry and decreased with clinical improvement. Serum calcitonin levels correlated significantly with low blood ionized calcium levels, indicating that hypercalcitoninemia may play a role in the pathogenesis of hypocalcemia in these children. Urine calcium excretion was not increased in the four children studied. We speculate that with clinical improvement, a rise in serum parathyroid hormone levels and a decline in serum calcitonin levels may help restore normocalcemia in these acutely ill children.