Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

Rewarming After Severe Accidental Hypothermia Using the Esophageal Heat Transfer Device: A Case Report

Patients with severe accidental hypothermia require active rewarming. External rewarming may not be successful in severe hypothermia, and use of invasive techniques is limited to regional centers and is associated with vascular access site and other complications. We present a patient with severe accidental hypothermia who was successfuly rewarmed using a novel esophageal heat transfer device. A 55-year-old male (175 cm, 71 kg) was admitted with the first recorded temperature 23.3°C. Rewarming using renal replacement therapy circuit was unsuccessful because of severe hypotension. We inserted the esophageal heat transfer device and rewarmed him successfully to target temperature 35-36°C. After rewarming, we maintained his body temperature in the range 35-36°C until accidental removal of the device. We observed no major adverse effects. To conclude, rewarming from severe accidental hypothermia was possible using the esophageal heat transfer device.

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.

Swedish-Norwegian co-operation in the treatment of three hypothermia victims: a case report

BACKGROUND

Accidental hypothermia with cardiac arrest represents a challenge for pre-hospital rescuers as well as in-hospital staff. For pre-hospital personnel, the main focus is to get the patient to the correct destination without unnecessary delay. For in-hospital personnel early information is vital to assess the possibility for resuscitation with extracorporeal re-warming. The challenge is augmented when rescuers must cross national borders to reach and/or deliver the patients. We present a case where three adolescent boys suffered severe hypothermia after a canoeing accident in Sweden.

CASE PRESENTATION

Three 14-year-old boys were canoeing a mountain lake close to the Norwegian border when their boat capsized and they all fell into the cold water. The rescue operation was hampered by rough weather conditions, and immersion times spanned from 63 to 125 min. Flight times from the scene of accident to the nearest ECMO center in Norway (Trondheim) and Sweden (Umeå) were about 30 and 90 min respectively. Two of the victims showed no vital signs after retrieval from the water and had extremely low body temperatures. They were brought to Trondheim University Hospital where they were resuscitated successfully with extracorporeal re-warming. Unable to be weaned from ECMO in the initial phase, both patients were retrieved by mobile ECMO teams to Karolinska University Hospital, from where they were discharged to their homes with good outcomes, although with some sequelae. A third victim with moderate to severe hypothermia without cardiac arrest was treated at a local hospital, from where he after a short stay was discharged without physical sequelae.

CONCLUSION

These cases are a reminder of the traditional mantra that «no one is dead until warm and dead». Good communication between pre- and in-hospital staff can be vital for optimizing patient treatment when handling victims of severe hypothermia, and especially when there is multiple victims. Communication between neighboring countries, but even neighboring regions within the same country, can be challenging. We encourage regions similar to ours to review protocols regarding hypothermia management, making them more robust before incidents like this take place.

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.

Measurements of rates of cooling of a manikin insulated with different mountain rescue casualty bags

Background

Accidental hypothermia is common in those who sustain injuries in remote environments. This is unpleasant and associated with adverse effects on subsequent patient outcomes. To minimise further heat loss, a range of insulating systems are available to mountain rescue teams although the most effective and cost-efficient have yet to be determined.

Methods

Under ambient, still, dry, air conditions, a thermal manikin was filled with water at a temperature of 42 °C and then placed into a given insulation system. Water temperature was then continuously observed via an in-dwelling temperature sensor linked to a PROPAQ 100 series monitor and recorded every 10 min for 130 min. This method was repeated for each insulating package.

Results

The vacuum mattress/Pertex©/fibrepile blanket system, either on its own or coupled with the Wiggy bag, was the most efficient with water temperatures only decreasing by 3.2 °C over 130 min. This was followed by the heavy-weight casualty bags without the vacuum mattress/Pertex©/fibrepile blanket system, decreasing by 4.2–4.3 °C. With the Blizzard bag, a decline in water temperature of 5.4 °C was seen over the study duration while a decrease of 9.5 °C was noted when the plastic survival bag was employed.

Conclusions

Under the still-air conditions of the study, the vacuum mattress/Pertex©/fibrepile blanket was seen to offer comparable insulation effectiveness compared to be both heavy-weight casualty bags. In turn, these three systems appeared more efficient at insulating the manikin than the Blizzard bag or plastic survival bag.

Electronic supplementary material

The online version of this article (doi:10.1186/s13728-017-0055-7) contains supplementary material, which is available to authorised users.

Endovascular rewarming in the emergency department for moderate to severe accidental hypothermia

BACKGROUND

Endovascular temperature control catheters can be utilized for emergent rewarming in accidental hypothermia. The purpose of this study was to compare patients with moderate to severe hypothermia rewarmed with an endovascular temperature control catheter versus usual care at our institution.

METHODS

We conducted a retrospective, observational cohort study of patients with moderate to severe accidental hypothermia (core body temperature less than 32°C) in the Emergency Department of an urban, tertiary care medical center. We identified the rewarming techniques utilized for each patient, including those who had an endovascular temperature control catheter placed (Quattro© or Icy© catheter, CoolGuard© 3000 regulation system, Zoll Medical). Rewarming rates and outcomes were compared for patients with and without the endovascular temperature control catheter. We systematically screened for procedural complications.

RESULTS

There were 106 patients identified with an initial core temperature less than or equal to 32°C; 52 (49%) patients rewarmed with an endovascular temperature control catheter. Other methods of rewarming included external forced-air rewarming (85, 80%), bladder lavage (17, 16%), gastric lavage (10, 9%), closed pleural lavage (6, 6%), and peritoneal lavage (3, 3%). Rate of rewarming did not differ between the groups with and without catheter-based rewarming (1.3°C/h versus 1.0°C/h, difference 0.3°C, 95% confidence interval [CI] of the difference 0-0.6°C) and neither did survival (70% versus 71%, difference 1%, 95% CI -17 to 20%). We did not identify any significant vascular injuries resulting from endovascular catheter use.

CONCLUSION

The endovascular temperature control system was not associated with an increased rate of rewarming in this cohort with moderate to severe hypothermia; however, this technique appears to be safe and feasible.

A concept for optimizing avalanche rescue strategies using a Monte Carlo simulation approach

Recent technical and strategical developments have increased the survival chances for avalanche victims. Still hundreds of people, primarily recreationists, get caught and buried by snow avalanches every year. About 100 die each year in the European Alps-and many more worldwide. Refining concepts for avalanche rescue means to optimize the procedures such that the survival chances are maximized in order to save the greatest possible number of lives. Avalanche rescue includes several parameters related to terrain, natural hazards, the people affected by the event, the rescuers, and the applied search and rescue equipment. The numerous parameters and their complex interaction make it unrealistic for a rescuer to take, in the urgency of the situation, the best possible decisions without clearly structured, easily applicable decision support systems. In order to analyse which measures lead to the best possible survival outcome in the complex environment of an avalanche accident, we present a numerical approach, namely a Monte Carlo simulation. We demonstrate the application of Monte Carlo simulations for two typical, yet tricky questions in avalanche rescue: (1) calculating how deep one should probe in the first passage of a probe line depending on search area, and (2) determining for how long resuscitation should be performed on a specific patient while others are still buried. In both cases, we demonstrate that optimized strategies can be calculated with the Monte Carlo method, provided that the necessary input data are available. Our Monte Carlo simulations also suggest that with a strict focus on the "greatest good for the greatest number", today's rescue strategies can be further optimized in the best interest of patients involved in an avalanche accident.

Clinical course and prognostic factors of patients in severe accidental hypothermia with circulatory instability rewarmed with veno-arterial ECMO - an observational case series study

Background

Recently, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) has become the rewarming treatment of choice in hypothermic cardiac arrest. The detailed indications for extracorporeal rewarming in non-arrested, severely hypothermic patients with circulatory instability have not been established yet. The primary purpose of the study was a preliminary analysis of all aspects of the treatment process, as well as initial identification of mortality risk factors within the group of severely hypothermic patients, treated with arteriovenous extracorporeal membrane oxygenation (VA-ECMO). The secondary aim of the study was to evaluate efficacy of VA-ECMO in initial 6-h period of treatment

Methods

From July 2013 to June 2016, thirty one hypothermic patients were accepted for extracorporeal rewarming at Severe Accidental Hypothermia Center, Cracow. Thirteen patients were identified with circulatory instability and were enrolled in the study. The evaluation took into account patients’ condition on admission, the course of therapy, and changes in laboratory and hemodynamic parameters.

Results

Nine out of 13 analyzed patients survived (69%). Patients who died were older, had lower both systolic and diastolic pressure, and had increased creatinine an potassium levels on admission. In surviving patients, arterial blood gases parameters (pH, BE, HCO₃) and lactates would normalize more quickly. Their potassium level was lower on admission as well. The values of the core temperature on admission were comparable. Although normothermia was achieved in 92% of patients, none of them had been weaned-off VA-ECMO in the first 6 h of treatment.

Discussion and Conclusions

In our preliminary study more pronounced markers of cardiocirculatory instability and organ hypoperfusion were observed in non-survivors. Future studies on indications to extracorporeal rewarming in severely hypothermic, non-arrested patients should focus on the extent of hemodynamic disturbances. Short term (<6 h) treatment in severe hypothermic, non-arrested patients seems to be not clinically appropriate.

Should capnography be used as a guide for choosing a ventilation strategy in circulatory shock caused by severe hypothermia? Observational case-series study

Background

Severe accidental hypothermia can cause circulatory disturbances ranging from cardiac arrhythmias through circulatory shock to cardiac arrest. Severity of shock, pulmonary hypoperfusion and ventilation-perfusion mismatch are reflected by a discrepancy between measurements of CO₂ levels in end-tidal air (EtCO₂) and partial CO₂ pressure in arterial blood (PaCO₂). This disparity can pose a problem in the choice of an optimal ventilation strategy for accidental hypothermia victims, particularly in the prehospital period. We hypothesized that in severely hypothermic patients capnometry should not be used as a reliable guide to choose optimal ventilatory parameters.

Methods

We undertook a pilot, observational case-series study, in which we included all consecutive patients admitted to the Severe Hypothermia Treatment Centre in Cracow, Poland for VA-ECMO in stage III hypothermia and with signs of circulatory shock. We performed serial measurements of arterial blood gases and EtCO₂, core temperature, and calculated a PaCO₂/EtCO₂ quotient.

Results

The study population consisted of 13 consecutive patients (ten males, three females, median 60 years old). The core temperature measured in esophagus was 20.7–29.0 °C, median 25.7 °C. In extreme cases we have observed a Pa-EtCO₂ gradient of 35–36 mmHg. Median PaCO₂/EtCO₂ quotient was 2.15.

Discussion and Conclusion

Severe hypothermia seems to present an example of extremely large Pa-EtCO₂ gradient. EtCO₂ monitoring does not seem to be a reliable guide to ventilation parameters in severe hypothermia.

Good neurological outcome after accidental hyopthermia presenting with asytole

A 43-year-old woman became exhausted and fainted on descent at 1127 MAMSL altitude and snowfall. A rescue team diagnosed asystole. With manual cardiopulmonary resuscitation (CPR) she was transported to the next extracorporeal life support (ECLS) center. Admission temperature was 20.7 °C. CPR continued until ECLS was initiated. Two days later she was awake, orientated, and with no neurological deficits. With hypothermic cardiac arrest, a favorable outcome depends on early continuous CPR, triage, and ECLS rewarming. It holds true that "nobody is dead until they are warmed and dead" if one cools first and arrests thereafter.

Warming the head of hypothermic patient - is it always safe?

The head warming in hypothermic victims is an alternative way of heat donation, which does not inhibit shivering and does not impede the access to the patient’s chest. It seems to be a safe method in mild hypothermia. The authors of the review article “Accidental hypothermia – an update” suggest this way of heat donation, without indicating precisely, in which group of patients it can be applied. In severe hypothermia, the brain-protective effect of cold is well known. The decreased need of oxygen allows good neurological outcome after long lasting cardiac arrest. Therefore, in deep hypothermia, the brain tissue should be rather insulated from the heat source than warmed.