Extracorporeal Life Support for Refractory Cardiac Arrest from Accidental Hypothermia: A 10-Year Experience in Edinburgh

[Extracorporeal cardiopulmonary resuscitation-An orientation]

Both in-hospital and out-of-hospital cardiac arrests are associated with a high mortality. In the past survival advantages for patients could be achieved by optimizing the chain of rescue and postresuscitation treatment; however, for patients with refractory cardiac arrest, there have so far been few promising treatment options. For selected patients with refractory cardiac arrest who do not achieve return of spontaneous circulation with conventional cardiopulmonary resuscitation (CPR), extracorporeal (e)CPR using venoarterial extracorporeal membrane oxygenation is an option to improve the probability of survival. This article describes the technical features, important aspects of treatment, and the current data situation on eCPR in patients with in-hospital or out-of-hospital cardiac arrest.

[Extracorporeal cardiopulmonary resuscitation-An orientation]

Both in-hospital and out-of-hospital cardiac arrests are associated with a high mortality. In the past survival advantages for patients could be achieved by optimizing the chain of rescue and postresuscitation treatment; however, for patients with refractory cardiac arrest, there have so far been few promising treatment options. For selected patients with refractory cardiac arrest who do not achieve return of spontaneous circulation with conventional cardiopulmonary resuscitation (CPR), extracorporeal (e)CPR using venoarterial extracorporeal membrane oxygenation is an option to improve the probability of survival. This article describes the technical features, important aspects of treatment, and the current data situation on eCPR in patients with in-hospital or out-of-hospital cardiac arrest.

E-CPR in Cardiac Arrest due to Accidental Hypothermia Using Intensivist Cannulators: A Case Series of Nine Consecutive Patients

Background: Severe accidental hypothermia (AH) accounts for over 1300 deaths/year in the United States. Early extracorporeal life support (ECLS) is recommended for hypothermic cardiac arrest. We describe the use of a rapid-deployment extracorporeal cardiopulmonary resuscitation (E-CPR) team using intensivist physicians (IPs) as cannulators and report the outcomes of consecutive patients cannulated for ECLS to manage cardiac arrest due to AH. Methods: We reviewed all patients managed with veno-arterial (V-A) ECLS for hypothermic cardiac arrest between January 1, 2017 and November 1, 2021. For each patient- age, sex, cause of hypothermia, initial core temperature, initial rhythm, time from arrest to cannulation, cannula configuration, pH, lactate, potassium, cannulation complications, duration of ECLS, hospital length of stay, mortality, and cerebral performance category (CPC) at discharge were reviewed. Results: Nine consecutive patients were identified that underwent V-A ECLS for cardiac arrest due to AH. Seven (78%) were witnessed arrests. Initial rhythm was ventricular fibrillation (VF) in eight patients and pulseless electrical activity (PEA) in one. The mean initial core temperature was 23.8 degrees Celsius. The mean time from arrest to cannulation was 58 min (range 17 to 251 min). There were no complications related to cannulation. The mean duration of ECLS was 39.1 h. All nine patients were discharged alive with a Cerebral Performance score of one or two. Conclusion: In this case series of consecutive patients reporting intensivist-deployed E-CPR for cardiac arrest due to AH, all patients survived to discharge with a favorable neurologic outcome. A rapidly available E-CPR team utilizing intensivist cannulators may improve outcomes in patients with cardiac arrest due to AH.

Extracorporeal membrane oxygenation versus conventional rewarming for severe hypothermia in an urban emergency department

BACKGROUND

Severe hypothermia (core body temperature < 28°C) is life-threatening and predisposes to cardiac arrest. The comparative effectiveness of different active internal rewarming methods in an urban U.S. population is unknown. We aim to compare outcomes between hypothermic emergency department (ED) patients rewarmed conventionally using an intravascular rewarming catheter or warm fluid lavage versus those rewarmed using extracorporeal membrane oxygenation (ECMO).

METHODS

We performed a retrospective cohort analysis of adults with severe hypothermia due to outdoor exposure presenting to an urban ED in Minnesota, 2007-2021. The primary outcome was hospital survival. We also calculated the rewarming rate in the 4 h after ED arrival and compared these data between patients rewarmed with ECMO (the extracorporeal rewarming group) versus without ECMO (the conventional rewarming group). We repeated these analyses in the subgroup of patients with cardiac arrest.

RESULTS

We analyzed 44 hypothermic ED patients: 25 patients in the extracorporeal rewarming group (median temperature 24.1°C, 84% with cardiac arrest) and 19 patients in the conventional rewarming group (median temperature 26.3°C, 37% with cardiac arrest; 89% received an intravascular rewarming catheter). The median rewarming rate was greater in the extracorporeal versus conventional group (2.3°C/h vs. 1.5°C/h, absolute difference 0.8°C/h, 95% confidence interval [CI] 0.3-1.2°C/h) yet hospital survival was similar (68% vs. 74%). Among patients with cardiac arrest, hospital survival was greater in the extracorporeal versus conventional group (71% vs. 29%, absolute difference 42%, 95% CI 4%-82%).

CONCLUSIONS

Among ED patients with severe hypothermia and cardiac arrest, survival was significantly higher with ECMO versus conventional rewarming. Among all hypothermic patients, ECMO use was associated with faster rewarming than conventional methods.

Successful Nonextracorporeal Life Support Resuscitation and Rewarming of a Patient with Hypothermia in Cardiac Arrest

We report full recovery of a patient with hypothermia in cardiac arrest following continuous and prolonged cardiopulmonary resuscitation (CPR) and conventional, nonextracorporeal life support (non-ECLS) methods. A 57-y-old man presented with unwitnessed cardiac arrest and a core temperature of 23°C (73°F). The presenting cardiac rhythm was ventricular fibrillation. The team administered epinephrine and performed defibrillation and CPR. Because ECLS was unavailable at the facility, the medical team externally and internally rewarmed the patient using heated blankets, forced warmed air, thoracic lavage, and warmed IV fluids. The patient achieved return of spontaneous circulation after 4 h 56 min of continuous CPR and rewarming. The medical team admitted the patient to the intensive care unit. He achieved full neurologic recovery the following day. When ECLS is not available and transfer is not appropriate because of patient instability or hospital location, conventional rewarming methods and continuous, prolonged CPR can lead to successful outcomes in patients with hypothermia in cardiac arrest. This case demonstrates that CPR in patients with hypothermia-associated cardiac arrest can lead to full recovery.

Extracorporeal Life Support in Accidental Hypothermia with Cardiac Arrest-A Narrative Review

Severely hypothermic patients, especially suffering cardiac arrest, require highly specialized treatment. The most common problems affecting the recognition and treatment seem to be awareness, logistics, and proper planning. In severe hypothermia, pathophysiologic changes occur in the cardiovascular system leading to dysrhythmias, decreased cardiac output, decreased central nervous system electrical activity, cold diuresis, and noncardiogenic pulmonary edema. Cardiac arrest, multiple organ dysfunction, and refractory vasoplegia are indicative of profound hypothermia. The aim of these narrative reviews is to describe the peculiar pathophysiology of patients suffering cardiac arrest from accidental hypothermia. We describe the good chances of neurologic recovery in certain circumstances, even in patients presenting with unwitnessed cardiac arrest, asystole, and the absence of bystander cardiopulmonary resuscitation. Guidance on patient selection, prognostication, and treatment, including extracorporeal life support, is given.

Treatment of the lung injury of drowning: a systematic review

Background

Drowning is a cause of significant global mortality. The mechanism of injury involves inhalation of water, lung injury and hypoxia. This systematic review addressed the following question: In drowning patients with lung injury, what is the evidence from primary studies regarding treatment strategies and subsequent patient outcomes?

Methods

The search strategy utilised PRISMA guidelines. Databases searched were MEDLINE, EMBASE, CINAHL, Web of Science and SCOPUS. There were no restrictions on publication date or age of participants. Quality of evidence was evaluated using GRADE methodology.

Results

Forty-one papers were included. The quality of evidence was very low. Seventeen papers addressed the lung injury of drowning in their research question and 24 had less specific research questions, however included relevant outcome data. There were 21 studies regarding extra-corporeal life support, 14 papers covering the theme of ventilation strategies, 14 addressed antibiotic use, seven papers addressed steroid use and five studies investigating diuretic use. There were no clinical trials. One retrospective comparison of therapeutic strategies was found. There was insufficient evidence to make recommendations as to best practice when supplemental oxygen alone is insufficient. Mechanical ventilation is associated with barotrauma in drowning patients, but the evidence predates the practice of lung protective ventilation. There was insufficient evidence to make recommendations regarding adjuvant therapies.

Conclusions

Treating the lung injury of drowning has a limited evidentiary basis. There is an urgent need for comparative studies of therapeutic strategies in drowning.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03687-2.

Rewarming From Hypothermic Cardiac Arrest Applying Extracorporeal Life Support: A Systematic Review and Meta-Analysis

Introduction: This systematic review and meta-analysis aims at comparing outcomes of rewarming after accidental hypothermic cardiac arrest (HCA) with cardiopulmonary bypass (CPB) or/and extracorporeal membrane oxygenation (ECMO). Material and Methods: Literature searches were limited to references with an abstract in English, French or German. Additionally, we searched reference lists of included papers. Primary outcome was survival to hospital discharge. We assessed neurological outcome, differences in relative risks (RR) of surviving, as related to the applied rewarming technique, sex, asphyxia, and witnessed or unwitnessed HCA. We calculated hypothermia outcome prediction probability score after extracorporeal life support (HOPE) in patients in whom we found individual data. P < 0.05 considered significant. Results: Twenty-three case observation studies comprising 464 patients were included in a meta-analysis comparing outcomes of rewarming with CPB or/and ECMO. One-hundred-and-seventy-two patients (37%) survived to hospital discharge, 76 of 245 (31%) after CPB and 96 of 219 (44 %) after ECMO; 87 and 75%, respectively, had good neurological outcomes. Overall chance of surviving was 41% higher (P = 0.005) with ECMO as compared with CPB. A man and a woman had 46% (P = 0.043) and 31% (P = 0.115) higher chance, respectively, of surviving with ECMO as compared with CPB. Avalanche victims had the lowest chance of surviving, followed by drowning and people losing consciousness in cold environments. Assessed by logistic regression, asphyxia, unwitnessed HCA, male sex, high initial body temperature, low pH and high serum potassium (s-K+) levels were associated with reduced chance of surviving. In patients displaying individual data, overall mean predictive surviving probability (HOPE score; n = 134) was 33.9 ± 33.6% with no significant difference between ECMO and CPB-treated patients. We also surveyed 80 case reports with 96 victims of HCA, who underwent resuscitation with CPB or ECMO, without including them in the meta-analysis. Conclusions: The chance of surviving was significantly higher after rewarming with ECMO, as compared to CPB, and in patients with witnessed compared to unwitnessed HCA. Avalanche victims had the lowest probability of surviving. Male sex, high initial body temperature, low pH, and high s-K+ were factors associated with low surviving chances.

A systematic review of current ECPR protocols. A step towards standardisation

Aim

Extracorporeal cardiopulmonary resuscitation (ECPR) can treat cardiac arrest refractory to conventional therapies. Our goal was to identify the best protocol for survival with good neurological outcome through the evaluation of current inclusion criteria, exclusion criteria, cannulation strategies and additional therapeutic measures.

Methods

A systematic literature search was used to identify eligible publications from PubMed, Embase, Web of Science and Cochrane for articles published from 29 June 2009 until 29 June 2019.

Results

The selection process led to a total of 24 eligible articles, considering 1723 patients in total. A good neurological outcome at hospital discharge was found in 21.3% of all patients. The most consistent criterion for inclusion was refractory cardiac arrest (RCA), used in 21/25 (84%) of the protocols. The preferred cannulation method was the percutaneous Seldinger technique (44%).

Conclusion

ECPR is a feasible option for cardiac arrest and should already be considered in an early stage of CPR. One of the key findings is that time-to-ECPR seems to be correlated with good neurological survival. An important contributing factor is the definition of RCA. Protocols defining RCA as >10 ​min had a mean good neurological survival of 26.7%. Protocols with a higher cut-off, between 15 and 30 ​min, had a mean good neurological survival of 14.5%. Another factor contributing to the time-to-ECPR is the preferred access technique. A percutaneous Seldinger technique combined with ultrasonography and fluoroscopic guidance leads to a reduced cannulation time and complication rate. Conclusive research around prehospital cannulation still needs to be conducted.

Outcomes of Extracorporeal Life Support Use in Accidental Hypothermia: A Systematic Review

BACKGROUND

Extracorporeal life support (ECLS) has been used in the treatment of accidental hypothermia with hemodynamic instability, with promising outcomes. This systematic review examines ECLS treatment of accidental hypothermia to assess outcomes.

METHODS

An electronic search was performed to identify articles reporting ECLS use for treatment of accidental hypothermia. Only reports describing patients aged more than 16 years after January 1, 2005, were included. Nineteen studies were identified comprising 47 patients. Demographic information, perioperative variables, and outcomes were extracted for analysis.

RESULTS

Median patient age was 48 years (interquartile range (IQR), 29 to 56), and 72.3% (34 of 47) were male. On presentation, median body temperature was 24.6°C (IQR, 22.2° to 26°C), median potassium level 4.3 mmol/L (IQR, 3.4 to 4.6 mmol/L), and median Glasgow Coma Scale score 3 (IQR, 3 to 7). Cardiac arrest occurred in 35 of 47 patients (74.5%). Median time to ECLS initiation from scene was 155 minutes (IQR, 113 to 245). Median ECLS duration was 18 hours (IQR, 4 to 27), with median rewarming rate of 2°C per hour (IQR, 1.5° to 4°). Median intensive care unit stay and hospital length of stay were 8 days (IQR, 2 to 16) and 17 days (IQR, 10 to 36), respectively. Inhospital mortality was 19.1% (9 of 47). Median discharge Glasgow Coma Scale score was 15 (IQR, 15 to 15) with minor long-term cognitive impairments noted in 6 of 47 patients (19.4%). Survival was significantly associated with potassium on presentation (P < .001), initial body temperature (P < .001), and ECLS rewarming rate (P < .001).

CONCLUSIONS

Extracorporeal life support is a viable cardiac support option for rewarming patients with accidental hypothermia, and initial potassium level, initial body temperature, and ECLS rewarming rate appear to be significantly associated with survival.

A novel ECG-biomarker for cardiac arrest during hypothermia

Background

Treatment of arrhythmias evoked by accidental or therapeutic hypothermia and rewarming remains challenging. We aim to find an ECG-biomarker that can predict ventricular arrhythmias at temperatures occurring in therapeutic and accidental hypothermia.

Main body

Evaluation of ECG-data from accidental and therapeutic hypothermia patients and experimental data on ECG and ventricular fibrillation (VF) threshold in hypothermic New Zealand White Rabbits. VF threshold was measured in rabbit hearts cooled to moderate (31 °C) and severe (17 °C) hypothermia. QRS-interval divided by corrected QT-interval (QTc) was calculated at same temperatures. Clinical QRS/QTc data were obtained after a systematic literature review. Rabbit QRS/QTc values correlated with risk for VF (correlation coefficient: 0.97). Human QRS/QTc values from hypothermic patients, showed similar correlation with risk for ventricular fibrillation in the experimental data (correlation coefficient: 1.00).

Conclusions

These calculations indicate that QRS/QTc has potential as novel biomarker for predicting risk of hypothermia-induced cardiac arrest. Our findings apply both to victims of accidental hypothermia and to patients undergoing therapeutic hypothermia during surgery or after e.g. cardiac arrest.

Veno-Arterial Extracorporeal Membrane Oxygenation for Cardiogenic Shock

Extracorporeal membrane oxygenation has evolved, from a therapy that was selectively applied in the pediatric population in tertiary centers, to more widespread use in diverse forms of cardiopulmonary failure in all ages. We provide a practical review for cardiovascular clinicians on the application of veno-arterial extracorporeal membrane oxygenation in adult patients with cardiogenic shock, including epidemiology of cardiogenic shock, indications, contraindications, and the extracorporeal membrane oxygenation circuit. We also summarize cannulation techniques, practical management and troubleshooting, prognosis, and weaning and exit strategies, with attention to end of life and ethical considerations.

Impact of rewarming rate on the mortality of patients with accidental hypothermia: analysis of data from the J-Point registry

BACKGROUND

Accidental hypothermia (AH) is defined as an involuntary decrease in core body temperature to < 35 °C. The management of AH has been progressing over the last few decades, and numerous techniques for rewarming have been validated. However, little is known about the association between rewarming rate (RR) and mortality in patients with AH.

METHOD

This was a multicentre chart review study of patients with AH visiting the emergency department of 12 institutions in Japan from April 2011 to March 2016 (Japanese accidental hypothermia network registry, J-Point registry). We retrospectively registered patients using the International Classification of Diseases, Tenth Revision code T68: 'hypothermia'. We excluded patients whose body temperatures were unknown or ≥ 35 °C, who could not be rewarmed, whose rewarmed temperature or rewarming time was unknown, those aged < 18 years, or who or whose family members had refused to join the registry. RR was calculated based on the body temperature on arrival at the hospital, time of arrival at the hospital, the documented temperature during rewarming, and time of the temperature documentation. RR was classified into the following five groups: ≥2.0 °C/h, 1.5-< 2.0 °C/h, 1.0-< 1.5 °C/h, 0.5-< 1.0 °C/h, and < 0.5 °C/h. The primary outcome of this study was in-hospital mortality. The association between RR and in-hospital mortality was evaluated using multivariate logistic regression analysis.

RESULT

During the study, 572 patients were registered in the J-Point registry, and 481 patients were included in the analysis. The median body temperature on arrival to the hospital was 30.7 °C (interquartile range [IQR], 28.2 °C-32.4 °C), and the median RR was 0.85 °C/h (IQR, 0.53 °C/h-1.31 °C/h). The in-hospital mortality rates were 19.3% (11/57), 11.1% (4/36), 14.4% (15/104), 20.1% (35/175), and 34.9% (38/109) in the ≥2.0 °C/h, 1.5-< 2.0 °C/h, 1.0-< 1.5 °C/h, 0.5-< 1.0 °C/h, and < 0.5 °C/h groups, respectively. Multivariate regression analysis revealed that in-hospital mortality rate increased with each 0.5 °C/h decrease in RR (adjusted odds ratio, 1.49; 95% confidence interval, 1.15-1.94; P_trend < 0.01).

CONCLUSION

This study showed that slower RR is independently associated with in-hospital mortality.

Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update

To provide guidance to clinicians, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and a balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations. This is the 2019 update of the Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update.

Management of accidental hypothermia: an established extracorporeal membrane oxygenation centre experience

Introduction:

Data on management of severe accidental hypothermia published from an established high-volume extracorporeal membrane oxygenation centre are scarce.

Methods:

A total of 28 patients with intravesical temperature lower than 28°C on admission were either treated with veno-arterial extracorporeal membrane oxygenation or rewarmed conservatively.

Results:

A total of 10 patients rewarmed on veno-arterial extracorporeal membrane oxygenation (age: 37 ± 12.6 years) and 18 conservatively (age: 55.2 ± 11.2 years) were collected over a course of 5 years. The dominant cause was alcohol intoxication with exposure to cold (39%), 12 patients were resuscitated prior to admission. The admission temperature in the extracorporeal membrane oxygenation group (23.8 ± 2.6°C) was lower than in the non–extracorporeal membrane oxygenation group (26.0 ± 1.5°C, p = 0.01). The peripheral percutaneous veno-arterial extracorporeal membrane oxygenation was always cannulated in malignant arrhythmias causing refractory cardiac arrest. The typical extracorporeal membrane oxygenation blood flow was 3-4 L/minute and sweep gas flow 2 L/minute, the median extracorporeal membrane oxygenation duration was 48.3 (28.1-86.7) hours. The median rates of rewarming did not differ (0.41 (0.35-0.7)°C/hour in extracorporeal membrane oxygenation and 0.77 (0.54-0.98)°C/hour in non–extracorporeal membrane oxygenation, p = 0.46) as well as the admission arterial lactate, pH and potassium. Their development was not different between the groups except for higher pH between the third and ninth hour of rewarming in the extracorporeal membrane oxygenation group. The hospital mortality was 10% in the extracorporeal membrane oxygenation group and 11.1% in the non–extracorporeal membrane oxygenation group with the median last Glasgow Coma Scale 15 and Cerebral Performance Score 1.

Conclusion:

Veno-arterial extracorporeal membrane oxygenation for severe hypothermia shows promising outcome data collected in an extracorporeal membrane oxygenation/extracorporeal cardiopulmonary resuscitation centre located in a European urban area. Except for presence of refractory cardiac arrest, the established hypothermia-related prognostic indicators did not differ between patients in need for extracorporeal membrane oxygenation and those rewarmed without extracorporeal membrane oxygenation.

Moderate brain hypothermia started before resuscitation improves survival and neurobehavioral outcomes after CA/CPR in mice

AIM OF THE STUDY

No definitive experimental or clinical evidence exists whether brain hypothermia before, rather than during or after, resuscitation can reduce hypoxic-ischemic brain injury following cardiac arrest/cardiopulmonary resuscitation (CA/CPR) and improve outcomes. We examined the effects of moderate brain hypothermia before resuscitation on survival and histopathological and neurobehavioral outcomes in a mouse model.

METHODS

Adult C57BL/6 male mice (age: 8-12 weeks) were subjected to 8-min CA followed by CPR. The animals were randomly divided into sham, normothermia (NT; brain temperature 37.5 °C), and extracranial hypothermia (HT; brain temperature 28-32 °C) groups. The hippocampal CA1 was assessed 7 day after resuscitation by histochemical staining. Neurobehavioral outcomes were evaluated by the Barnes maze (BMT), openfield (OFT), rotarod, and light/dark (LDT) tests. Cleaved caspase-3 and heat shock protein 60 (HSP70) levels were investigated by western blotting.

RESULTS

The HT group exhibited higher survival and lower CA1 neuronal injury than did the NT group. HT mice showed improved spatial memory in the BMT compared with NT mice. NT mice travelled a shorter distance in the OFT and tended to spend more time in the light compartment in the LDT than did sham and HT mice. The levels of cleaved caspase-3 and HSP70 were non-significantly higher in the NT than in the sham and HT groups.

CONCLUSIONS

Moderate brain hypothermia before resuscitation improved survival and reduced histological neuronal injury, spatial memory impairment, and anxiety-like behaviours after CA/CPR in mice.

Characteristics and outcome of patients with hypothermic out-of-hospital cardiac arrest: Experience from a European trauma center

BACKGROUND

Aim of the study was to investigate patient characteristics, survival rates and neurological outcome among hypothermic patients with out-of-hospital cardiac arrest (OHCA) admitted to a trauma center.

METHODS

A review of patients with OHCA and a core temperature ≤32°C admitted to a trauma center between 2004 and 2016.

RESULTS

Ninety-six patients (mean temperature 25.8°C±3.9°C) were entered in the study, 37 (39%) of them after avalanche burial. 47% showed return of spontaneous circulation (ROSC) prior to hospital admission. Survival with Glasgow-Pittsburgh Cerebral Performance Category (CPC) scale 1 or 2 was achieved in 25% of all patients and was higher in non-avalanche than in avalanche cases (35.6% vs 8.1%, p=0.002). Witnessed cardiac arrest was the most powerful predictor of favourable neurological outcome (RR: 10.8; 95% Confidence Interval: 3.2-37.1; Wald: 14.3; p<0.001), whereas ROSC prior to admission and body core temperature were not associated with survival with favourable neurological outcome. Cerebral CT scan pathology within 12h of admission increased the risk for unfavourable neurological outcome 11.7 fold (RR: 11.7; 95% CI: 3.1-47.5; p<0.001). Favourable neurological outcome was associated lower S 100-binding protein (0.69±0.5μg/l vs 5.8±4.9μg/l, p 0.002) and neuron-specific enolase (34.7±14.2μg/l vs 88.4±42.7μg/l, p 0.004) concentrations on intensive care unit (ICU) admission.

CONCLUSIONS

Survival with favourable neurological outcome was found in about a third of all hypothermic non-avalanche patients with OHCA admitted to a trauma center.

The impact of hypothermia on serum potassium concentration: A systematic review

BACKGROUND

Blood potassium is the main prognostic biomarker used for triage in hypothermic cardiac arrest. The aim of this review was to assess the impact of hypothermia on blood potassium levels and compare the underlying pathophysiological theories.

METHODS

The Medline electronic database was searched via PubMed for articles published from January 1970 to December 2016. The search strategy included studies related to hypothermia and potassium levels. The relevant literature on clinical studies and experimental studies was reviewed by the authors.

RESULTS

Among the 50 studies included in the review, 39 (78%) reported a decrease in blood potassium levels upon hypothermia onset. Hypothermic hypokalaemia is linked to an intracellular shift rather than an actual net loss. The intracellular shift is caused by a variety of factors such as enhanced functioning of Na+K+ATPase, beta-adrenergic stimulation, pH and membrane stabilisation in deep hypothermia. In contrast, hypothermia can act as an aggravating factor in severe trauma with hyperkalaemia being an indicator of an irreversible state of cell death. An increase in the blood potassium level during hypothermia may result from a lack of enzyme functioning at cold temperatures and blocked active transport.

CONCLUSION

Hypothermia causes an initial decrease of potassium levels; however, the final stage of hypothermic cardiac arrest can induce hyperkalaemia due to cell lysis and final depolarisation. Better understanding the physiopathology of potassium levels during accidental hypothermia could be critically important to better select patients who could benefit from aggressive resuscitation therapy such as extracorporeal cardiopulmonary resuscitation.