Accidental hypothermia

Measuring core temperature using the proprietary application and thermo-smartphone adapter

Fast and accurate measurement of core body temperature is crucial for accidental hypothermia treatment. We have developed a novel light and small adapter to the headset jack of a mobile phone based on Android. It has been applied to measure temperature and set up automatic notifications (e.g. Global Positioning System coordinates to emergency services dispatcher, ECMO coordinator). Its validity was confirmed in comparison with Vital Signs Monitor Spacelabs Healthcare Elance 93300 as a reference method, in a series of 260 measurements in the temperature range of 10-42 °C. Measurement repeatability was verified in a battery of 600 measurements (i.e. 100 readings at three points of 10, 25, 42 °C for both esophageal and tympanic catheters). Inter-method difference of ≤0.5 °C was found for 98.5% for esophageal catheter and 100% for tympanic catheter measurements, with concordance correlation coefficient of 0.99 for both. The readings were almost completely repeatable with water bath measurements (difference of ≤0.5 °C in 10 °C: 100% for both catheters; in 25 °C: 99% for esophageal catheter and 100% tympanic catheter; in 42 °C: 100% for both catheters). This lightweight adapter attached to smartphone and standard disposable probes is a promising tool to be applied on-site for temperature measurement in patients at risk of hypothermia.

Accidental hypothermia: factors related to long-term hospitalization. A retrospective study from northern Finland

Accidental hypothermia has a low incidence, but is associated with a high mortality rate. Knowledge about concomitant factors, complications, and length of hospital stay is limited. A retrospective cohort study on patients with accidental hypothermia admitted to Oulu University Hospital in Finland, over a 5-year period. Patients were categorized as short-stay patients (7 days or less) and long-stay patients (more than 7 days) according to their length of stay in hospital. From a total of 105 patients, 67 patients were included in the analyses. Alcohol abuse was the most common concomitant factor (54 %). Median length of hospital stay was 4 days, and 16 patients (24 %) stayed in hospital over 7 days (median 15 days). Thirty-day mortality was low (14/105, 13 %). Patients with long-term hospitalization had a lower initial temperature (28.4 versus 31.2 °C, p = 0.011), a lower level of consciousness (GCS score 8.4 versus 12.8, p = 0.003), more severe acidosis (pH 7.08 versus 7.28, p = 0.005, and lactate 7.2 versus 3.9, p = 0.043), and a lower level of platelets (183 versus 242, p = 0.041) on admission compared with short-stay patients. Thirty-six patients (54 %) had at least one complication, and this prolonged median hospital treatment for 2.5 days (p < 0.001). Alcohol is the most common concomitant factor and every fourth patient spends more than 7 days in hospital. Long-term hospitalization is related to a lower core temperature, lower consciousness, more severe lactic acidosis, lower platelet level and infections, rhabdomyolysis, and renal failure.

Protection against cold - a survey of available equipment in Swedish pre-hospital services

BACKGROUND

The aim of this study was to survey the current equipment used for prevention, treatment and monitoring of accidental hypothermia in Swedish pre-hospital services.

METHODS

A questionnaire was sent to all road ambulance services (AS), the helicopter emergency medical services (HEMS), the national helicopter search and rescue service (SAR) and the municipal rescue services (RS) in Sweden to determine the availability of insulation, active warming, fluid heating, and low-reading thermometers.

RESULTS

The response rate was 77% (n = 255). All units carried woollen or polyester blankets for basic insulation. Specific windproof insulation materials were common in the HEMS, SAR and RS units but only present in about half of the AS units. Active warming equipment was present in all the SAR units, but only in about two-thirds of the HEMS units and about one-third of the AS units. About half of the RS units had the ability to provide a heated tent or container. Low-reading thermometers were present in less than half of the AS and HEMS units and were non-existent in the SAR units. Pre-warmed intravenous fluids were carried by almost all of the AS units and half of the HEMS units but infusion heaters were absent in most units.

CONCLUSION

Basic insulation capabilities are well established in the Swedish pre-hospital services. Specific wind and waterproof insulation materials, active warming devices, low-reading thermometers and IV fluid heating systems are less common. We suggest the development and implementation of national guidelines on accidental hypothermia that include basic recommendations on equipment requirements.

A 95 year-old suffering circulatory arrest after accidental hypothermia: a case report

BACKGROUND

The elderly are vulnerable to cold and prone to accidental hypothermia, both because of environmental and endogenous factors. The incidence of severe accidental hypothermia among the elderly is poorly described, but many cases probably go unrecorded. Going through literature one finds few publications on severe hypothermia among the elderly, and, to our knowledge, nothing about extracorporeal re-warming of geriatric hypothermia victims.

CASE PRESENTATION

We present a case were a 95 year-old man with severe accidental hypothermia and circulatory arrest was brought to our hospital under on-going CPR, and was successfully resuscitated with extracorporeal circulation. He was discharged to his home without physical sequelae a few weeks later.

CONCLUSION

The decision whether or not to continue resuscitation of a nonagenarian can be difficult in many respects. Knowing that resuscitation with extracorporeal circulation is resource intensive may complicate the discussion. In light of our experience with this case we discuss medical and ethical aspects of modern treatment of severe accidental hypothermia.

A Guideline-Based Policy to Decrease Intensive Care Unit Admission Rates for Accidental Hypothermia

RATIONALE

Despite guidelines advising passive rewarming for mild accidental hypothermia (AH), patients are frequently admitted to intensive care unit (ICU) for active rewarming using a forced-air warming device. We implemented a new policy at our institution aimed at safely reducing ICU admissions for AH. We analyzed our practice pre- and post-policy intervention and compared our experiences with acute care hospitals in Connecticut.

METHODS

A retrospective chart review was performed on 203 participants with AH identified by primary and secondary discharge codes. Our new policy recommended passive rewarming on the medical floors for mild hypothermia (>32°C) and ICU admission for moderate hypothermia (<32°C). Practices of other Connecticut hospitals were obtained by surveying ICU nurse managers and medical directors.

RESULTS

Over a 3-year period, prior to rewarming policy change, 64% (n = 92) of patients with AH were admitted to ICU, with a mean ICU length of stay (LOS [SD]) of 2.75 (2.2) days. After the policy change, over a 3-year period, 15% (n = 9) were admitted to ICU (P < .001), with an ICU LOS of 2.11 (0.9) days (P = 0.005). In both groups with AH, altered mental status, infection, and acute alcohol intoxication were the most common diagnoses at presentation. Alcohol intoxication was more prevalent in the post-policy intervention group, pre 17% versus post 46% (P < .001). No complications such as dermal burns or cardiac arrhythmias were noted with forced-air warming device use during either time period. Among the 29 hospitals surveyed, 20 used active rewarming in ICU or intermediate care units and 9 cared for patients on telemetry units. Most hospitals used active external rewarming for core body temperature of <35°C; however, 37% of hospitals performed active rewarming at temperatures >35°Cor lacked a policy.

CONCLUSIONS

Reserving forced-air warming devices for the treatment of moderate-to-severe hypothermia (<32°C) significantly reduced ICU admissions for AH.

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.

Bradycardia and Hypothermia Complicating Azithromycin Treatment

Patient: Male, 4

Final Diagnosis: Febrile neutropenia

Symptoms: Fever

Medication: Azithromycin

Clinical Procedure: —

Specialty: Infectious Diseases

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.

Epidemiology and outcomes of children with accidental hypothermia: A propensity-matched study

BACKGROUND

The purpose of this study was to explore the epidemiology and outcomes of hospitalized children with a diagnosis of accidental hypothermia.

METHODS

The 2012 Kids' Inpatient Database, detailing discharge diagnoses in children admitted to US hospitals, was analyzed using International Classification of Diseases, Ninth Revision, Clinical Modification codes to filter out relevant patients. Children ages 1 month to 17 years were included in the analysis. Demographic and outcome variables in the hypothermia group were compared with the rest of the patients. In a separate analysis, children with hypothermia were matched 1:1 using a correlative propensity score using sex, age, hospital region, income quartiles, race, ventilation status, coagulopathy, drowning, and All Patient Refined Diagnosis Related Groups severity score and their outcomes were compared with controls. The sample data were weighted to get a national estimate.

RESULTS

Accidental hypothermia was present in 1,028 cases out of 1,915,435 discharges. Children with hypothermia were more likely to be males (54.7% vs. 50.9%; p < 0.05) and infants (32.6% vs. 17.5%); they were less likely to be teens (30% vs. 37.8%). Children with hypothermia were more likely to be admitted in the Southern region (48.3% vs. 38.4%; p < 0.05) and have a higher mortality rate compared to all other discharges (8.5% vs. 0.3%; p < 0.05) or when compared with the matched controls (8.9% vs. 4.4%).

CONCLUSIONS

The diagnosis of accidental hypothermia significantly increased mortality in hospitalized children. Interestingly, accidental hypothermia was more common in Southern states compared to the other areas of the United States.

LEVEL OF EVIDENCE

Prognostic/epidemiological study, level III.

Microscopic examination of pituitary glands in cases of fatal accidental hypothermia

In cases of death caused by hypothermia, histological analysis can be used to determine the cause of death. Certain histological alterations of the pituitary glands in hypothermia have been reported in the literature, including haemorrhage, hyperaemia and cellular vacuolization of cells in the anterior lobe. In the present study, the validity of these morphological alterations as markers for fatal accidental hypothermia was investigated in autopsy material. A total of 34 pituitary glands in cases of verified fatal accidental hypothermia were examined histologically (haematoxylin and eosin, ferric, azan) and immunohistochemically (LCA, ACTH, C5b-9). The findings were compared with 61 cases in a control group. Hyperaemia was found in 50.0% of the study group cases and 59.0% of the control group cases. Cellular vacuolization was observed in one case (2.9%) in the study group and one case (1.6%) in the control group. Acute or recent haemorrhage in the glandular tissue was never detected. In our study, the histopathological characteristics described in the literature as pathognomonic for hypothermia could not be confirmed. Furthermore, histological differences in the pituitary glands between fatal hypothermia cases and control group cases were not observed.

Modelling accidental hypothermia effects on a human body under different pathophysiological conditions

Accidental exposure to cold water environment is one of the most challenging situations in which hypothermia occurs. In the present work, we aim to characterise the energy balance of a human body subjected to such extreme environmental conditions. This study is carried out using a recently developed computational model and by setting boundary conditions needed to simulate the effect of cold surrounding environment. A major finding is the capacity of the body core regions to maintain their temperature high for a substantial amount of time, even under the most extreme environmental conditions. We also considered two disease states that highlight the spectrum of possible pathologies implicated in thermal regulation of the human body. These states are (i) cardiomyopathy, which affects the operating capacity of the heart, and (ii) malnutrition, which directly impairs the body’s ability to regulate heat exchange with the environment. We have found that cardiomyopathy has little influence on the thermal balance of the human body, whereas malnutrition has a profound negative effect on the thermal balance and leads to dramatic reduction in core temperature.

A Novel Cooling Method and Comparison of Active Rewarming of Mildly Hypothermic Subjects

OBJECTIVE

To compare the effectiveness of arteriovenous anastomosis (AVA) vs heated intravenous fluid (IVF) rewarming in hypothermic subjects. Additionally, we sought to develop a novel method of hypothermia induction.

METHODS

Eight subjects underwent 3 cooling trials each to a core temperature of 34.8±0.6 (32.7 to 36.3°C [mean±SD with range]) by 14°C water immersion for 30 minutes, followed by walking on a treadmill for 5 minutes. Core temperatures (Δtes) and rates of cooling (°C/h) were measured. Participants were then rewarmed by 1) control: shivering only in a sleeping bag; 2) IVF: shivering in sleeping bag and infusion of 2 L normal saline warmed to 42°C at 77 mL/min; and 3) AVA: shivering in sleeping bag and circulation of 45°C warmed fluid through neoprene pads affixed to the palms and soles of the feet.

RESULTS

Cold water immersion resulted in a decrease of 0.5±0.5°C Δtes and 1±0.3°C with exercise (P < .01); with an immersion cooling rate of 0.9±0.8°C/h vs 12.6±3.2°C/h with exercise (P < .001). Temperature nadir reached 35.0±0.5°C. There were no significant differences in rewarming rates between the 3 conditions (shivering: 1.3±0.7°C/h, R² = 0.683; IVF 1.3±0.7°C/h, R² = 0.863; and AVA 1.4±0.6°C/h, R² = 0.853; P = .58). Shivering inhibition was greater with AVA but was not significantly different (P = .07).

CONCLUSIONS

This study developed a novel and efficient model of hypothermia induction through exercise-induced convective afterdrop. Although there was not a clear benefit in either of the 2 active rewarming methods, AVA rewarming showed a nonsignificant trend toward greater shivering inhibition, which may be optimized by an improved interface.

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.

[Cardiac support and replacement systems]

In recent years, the widespread use of partial mechanical cardiac support and even temporary complete replacement of cardiac function has been established in many intensive care units in the treatment of refractory cardiogenic shock. There is a difference between partial left-ventricular assist devices (LVAD) and the possibility of complete heart (and lung) replacement by extra corporeal life support (ECLS). Despite the use of mechanical support devices, the mortality of cardiogenic shock remains high. The consideration of using percutaneous LVAD and ECLS in cardiogenic shock should be considered in refractory cardiogenic shock patients in addition to support by catecholamines and after early revascularization in acute coronary syndromes. However, there are no large randomized studies evaluating mechanical support systems with respect to outcome in cardiogenic shock patients. German and international guidelines do not recommend the routine use of mechanical support as a first-line treatment in cardiogenic shock patients and emphasize that their application should be restricted to patients with therapy refractory shock. In other cases of noninfarct-related cardiogenic shock (e. g., poisoning, myocarditis), ECLS use should be considered as bridging therapy. ECLS may also be considered in cardiopulmonary resuscitation which is termed E‑CPR. According to registry data, E‑CPR may reduce mortality in selected patients. A possible application of ECLS is severe accidental hypothermia with cardiac arrest despite limited data. In these rare cases, early ECLS should be considered for rewarming and stabilization.

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.

Severe hypothermia in transported pullets: case study of its occurrence, diagnosis and treatment using active external rewarming technique

Sixty pullets, aged 17 weeks, were presented when presumed to be 'dead' after being exposed to wet-cold weather transportation. The birds appeared unconscious and their feathers were soaking wet, and with a body rigid and cold to touch. The aim of the study was to resuscitate the hypothermic pullets. Blood samples were obtained and core body temperature recorded before and after rewarming. The birds were resuscitated using active external rewarming technique. Blood samples revealed significant (P < 0.05) decreases in the concentrations of serum electrolytes of Na, Cl, K, Ca and P; and renal function and activities of the serum enzymes of AST, ALT, ALP and CRT decreased compared to baseline reference normal values. Colonic temperature, recorded through the cloacae, revealed a temperature of 29 ± 0.4°C. The presumptive diagnosis was severe hypothermia. Treatment of the pullets using active external rewarming technique for 7 to 10 h resulted in successful restoration of all the behavioural, biochemical and colonic temperature responses to normal values. The treatment resulted in a complete recovery of all the birds with no signs of illness at 4-week follow-up. To the best of our knowledge, this study is one of the first reports to evaluate the behavioural and biochemical responses of pullets accidentally exposed to severe hypothermia, and successful treatment of the birds using active external rewarming technique.

The International Hypothermia Registry (IHR): Dieter's ESAO Winter Schools and Beat's International Hypothermia Registry

Accidental hypothermia could be listed as an 'orphan disease,' since mild hypothermia is common but has no severe medical consequences, whereas severe hypothermia is rare and life-threatening. In order to increase our knowledge, find new outcome predictors, and propose better guidelines for the treatment of deep accidental hypothermia victims, we created the International Hypothermia Registry (IHR: https://www.hypothermia-registry.org), which will allow us to gather a large number of cases in order to achieve statistical significance and issue evidence-based recommendations.

Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents

To provide guidance to clinicians and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the prevention, rescue, and medical management of avalanche and nonavalanche snow burial victims. Recommendations are graded on the basis of quality of supporting evidence according to the classification scheme of the American College of Chest Physicians.

Neurologic complications of acute environmental injuries

Environmental injuries can result in serious neurologic morbidity. This chapter reviews neurologic complications of thermal burns, smoke inhalation, lightning strikes, electric injury, near drowning, decompression illness, as well as heat stroke and accidental hypothermia. Knowing the pathophysiology and clinical presentation of such injuries is essential to proper management of primary and secondary medical complications. This chapter highlights the most frequently encountered neurologic injuries secondary to common environmental hazards, divided into the topics: injuries related to fire, electricity, water, and the extremes of temperature.

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.

Hypothermia and targeted temperature management in cats and dogs

OBJECTIVE

To review current knowledge surrounding the effects, treatment, and prognosis of hypothermia in people, dogs, and cats, as well as the application of therapeutic hypothermia in clinical medicine.

ETIOLOGY

Hypothermia may be a primary or secondary condition, and may be due to environmental exposure, illness, medications, anesthesia, or trauma. Hypothermia has been applied therapeutically in human medicine for a variety of conditions, including postcardiac arrest. In veterinary medicine, the technique has been applied in cardiac surgeries requiring bypass and in a patient with intractable seizures.

DIAGNOSIS

Hypothermia can be diagnosed based on presenting temperature or clinical signs, and appropriate diagnosis may require nontraditional thermometers.

THERAPY

Rewarming is the primary treatment for accidental hypothermia, with intensity ranging from passive surface rewarming to extracorporeal rewarming. The goal is to return the core temperature to a level that restores normal physiologic function of all body processes. Other supportive therapies such as intravenous fluids are typically indicated, and if cardiopulmonary arrest is present, prolonged resuscitation may be required. In cases of secondary hypothermia, reversal of the underlying cause is important.

PROGNOSIS

There are few prognostic indicators in human and veterinary patients with hypothermia. Even the most severely affected individuals, including those presenting in cardiopulmonary arrest, have potential for complete recovery with appropriate therapy. Therapeutic hypothermia has been shown to improve outcome in people following cardiac arrest. Further studies are needed to examine this application in veterinary medicine, as well as appropriate therapy and prognosis for cases of spontaneous hypothermia.

A Case of Severe Accidental Hypothermia Successfully Treated with Cardiopulmonary Bypass

After missing for seven days, a 34-year-old female was found with a rectal temperature of 19.8oC. Instead of attempting aggressive rewarming in the emergency department she was directly transferred to the operating room for extracorporeal rewarming. She received cardiopulmonary bypass (CPB) for 66 minutes at an initial warming rate of 12oC/ hour and warmed to 36.2oC. Her postoperative course was complicated by sepsis, which eventually led to bilateral below-knee amputations after refusing antibiotics. She was discharged 22 days after admission, with full neurologic recovery. This remarkable case highlights the emerging role of CPB as the definitive therapy for severe accidental hypothermia.

Brief Rewarming Blunts Hypothermia-Induced Alterations in Sensation, Motor Drive and Cognition

Background: It is well known that cold exposure experienced during occupational or recreational activities may adversely affect motor, cognitive performance, and health. Most research has used prolonged passive external rewarming modalities and focused on the direct effects on the kinetics of physiological and psychological responses in hypothermic subjects. However, the brief whole body rewarming effects on physiological and psychological responses in parallel with functional consequences on cognitive and neurophysiological functions have not been investigated. This study explores these effects in 12 healthy young men.

Methods: Subjects (20 ± 1 years) participated in 4 randomized trials, which were designed to compare the effects of whole-body brief (5-min) rewarming in 37°C water with rewarming for the same duration in 24°C (air) thermoneutral environment in mildly hypothermic subjects. After each rewarming, indicators of neuromuscular function (reflexes, central activation ratio, electromyography of exercising muscle, and contractile properties of calf muscles) and cognitive function (attention, simple motor speed, and information processing speed) were assessed.

Results: Compared to rewarming in thermoneutral environment, after brief rewarming in 37°C water, significantly lower metabolic heat production (MHP) (206 ± 33.4 vs. 121.9 ± 24.3 W·m², P < 0.01), heart rate (76 ± 16 vs. 60 ± 12 b·min⁻¹, P < 0.01), cold strain (6.4 ± 3.1 vs. 5.3 ± 2.7, P < 0.01), improved thermal comfort and induced cessation of shivering were found. Electrically induced maximum torque amplitudes increased (P100, 102.8 ± 21.3 vs. 109.2 ± 17.5 Nm and PTT100, 83.1 ± 17.1 vs. 92.7 ± 16.0 Nm, P < 0.05), contraction half-relaxation time decreased (599.0 ± 53.8 vs. 589.0 ± 56.3 ms, P < 0.05), and M_max-wave latency shortened (17.5 ± 2.2 vs. 15.6 ± 2.0 ms, P < 0.05) after 37°C water rewarming. Unlike rewarming in thermoneutral environment, 37°C water rewarming blunted the hypothermia-induced alterations in neural drive transmission (4.3 ± 0.5 vs. 3.4 ± 0.8 mV H-reflex and 4.9 ± 0.2 vs. 4.4 ± 0.4 mV V-wave, P < 0.05), which increased central fatigue during a 2-min maximum load (P < 0.05). Furthermore, only in brief warm water rewarming cerebral alterations were restored to the control level and it was indicated by shortened reaction times (P < 0.05).

Conclusions: Brief rewarming in warm water rather than the same duration rewarming in thermoneutral environment blunted the hypothermia-induced alterations for sensation, motor drive, and cognition, despite the fact that rectal and deep muscle temperature remained lowered.

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

BACKGROUND

Cardiac arrest caused by accidental hypothermia is a rare phenomenon with a significant mortality rate if untreated. The consensus is that these patients should be rewarmed with extracorporeal life support (ECLS) with the potential for excellent survival and neurologic outcomes. However, given the lack of robust data and clinical trials, the optimal management of such patients remains elusive.

OBJECTIVE

In this single-center study, we looked at the outcomes of all adult patients undergoing salvage ECLS for cardiac arrest caused by accidental hypothermia over a 10-year period from June 2006 to June 2016.

METHODS

These data were obtained from the Royal Infirmary of Edinburgh cardiothoracic surgery database. The patients' hard copy case notes, TrakCare (InterSystems Corp, Cambridge, MA), picture archiving and communications system (PACS), and WardWatcher databases were used to cross-check the accuracy of the acquired data.

RESULTS

Eleven patients met the inclusion criteria. The etiology of hypothermia was exposure to cold air (64%) and cold water immersion (36%). Two (18%) were treated with extracorporeal membrane oxygenation and the rest with cardiopulmonary bypass. The mean age was 51 years (range 32-73), and the mean core body temperature on admission was 20.6°C (range <18-24°C). The overall survival rate to hospital discharge was 72%, with 75% of survivors having no chronic neurologic impairment.

CONCLUSION

Our case series shows the remarkable salvageability of patients suffering prolonged cardiac arrest caused by accidental hypothermia, particularly in the absence of asphyxia, trauma, or severe hyperkalemia. ECLS is a safe and effective rewarming treatment and should be used to aggressively manage this patient group.

Outcome After Rewarming From Accidental Hypothermia by Use of Extracorporeal Circulation

BACKGROUND

Accidental hypothermia with arrested circulation remains a condition associated with high mortality. In our institution, extracorporeal circulation (ECC) rewarming has been the cornerstone in treating such patients since 1987. We here explore characteristics and outcomes of this treatment, to identify significant merits and challenges from 3 decades of experience in ECC rewarming.

METHODS

Sixty-nine patients rewarmed by ECC during the period from December 1987 to December 2015 were analyzed. One patient was excluded from the analyses because of combined traumatic cerebral injury. The analysis was focused on patient characteristics, treatment procedures, and outcomes were focused. Survivors were evaluated according to the cerebral performance categories scale. Simple statistics with nonparametric tests and χ² tests were used. Median value and range are reported.

RESULTS

Median age was 30 years (minimum 1.5, maximum 76), and the cause of accidental hypothermia was cold exposure (27.9%), avalanche (5.9%), and immersion/submersion accidents (66.2%). Eighteen patients survived (26.5%). The survival rate did not improve during the years. Survivors had lower serum potassium (p = 0.002), higher pH (p = 0.03), lower core temperature (p = 0.02), and shorter cardiopulmonary resuscitation time (p = 0.001), but ranges were wide. Although suspected primary hypoxia and hypothermia were associated with lower survival, we observed a 10.5% survival of these victims. Sixteen survivors had good outcome (cerebral performance category 1 or 2), whereas 2 patients with suspected primary hypoxia survived with severe cerebral disability (cerebral performance category 3).

CONCLUSIONS

Despite extended experience with ECC rewarming, improved handling strategies, and intensive care, no overall improvement in survival was observed. Good outcome was observed even among patients with a dismal prognosis.

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

BACKGROUND

This paper provides an up-to-date review of the management and outcome of accidental hypothermia patients with and without cardiac arrest.

METHODS

The authors reviewed the relevant literature in their specialist field. Summaries were merged, discussed and approved to produce this narrative review.

RESULTS

The hospital use of minimally-invasive rewarming for non-arrested, otherwise healthy, patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionised the management of hypothermic cardiac arrest, with survival rates approaching 100 % in some cases. Hypothermic patients with risk factors for imminent cardiac arrest (temperature <28 °C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS-centre. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanical CPR can be helpful. Delayed or intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern post-resuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimise pre-hospital triage, transport and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and post-resuscitation care.

CONCLUSIONS

Based on new evidence, additional clinical experience and clearer management guidelines and documentation, the treatment of accidental hypothermia has been refined. ECLS has substantially improved survival and is the treatment of choice in the patient with unstable circulation or cardiac arrest.

Extracorporeal Membrane Oxygenation (ECMO) for Hypothermic Cardiac Deterioration: A Case Series

Accidental hypothermia can lead to untoward cardiac manifestations and arrest. This report presents a case series of severe accidental hypothermia with cardiac complications in three emergency patients who were treated with extracorporeal membrane oxygenation (ECMO) and survived after re-warming. The aim of this discussion was to encourage more clinicians to consider ECMO as a re-warming therapy for severe hypothermia with circulatory collapse and to prompt discussion about decreasing the barriers to its use. Niehaus MT , Pechulis RM , Wu JK , Frei S , Hong JJ , Sandhu RS , Greenberg MR . Extracorporeal membrane oxygenation (ECMO) for hypothermic cardiac deterioration: a case series. Prehosp Disaster Med. 2016;31(5):570-571.

Dual Antiplatelet Therapy (DAPT) versus No Antiplatelet Therapy and Incidence of Major Bleeding in Patients on Venoarterial Extracorporeal Membrane Oxygenation

Aims

Bleeding is a frequent complication in patients on venoarterial extracorporeal membrane oxygenation (VA-ECMO). An indication for dual antiplatelet therapy due to coronary stent implantation is present in a considerable number of these patients. The objective of this retrospective study was to evaluate if dual antiplatelet therapy (DAPT) significantly increases the high intrinsic bleeding risk in patients on VA-ECMO.

Methods and Results

A total of 93 patients were treated with VA-ECMO between October 2010 and October 2013. Average time on VA-ECMO was 58.9 ± 1.7 hours. Dual antiplatelet therapy was given to 51.6% of all patients. Any bleeding was recorded in 60.2% of all patients. There was no difference in bleeding incidence in patients on DAPT when compared to those without any antiplatelet therapy including any bleeding (66.7% vs. 57.1%, p = 0.35), BARC3 bleeding (43.8% vs. 33.3%, p = 0.31) or pulmonary bleeding (16.7% vs. 19.0%, p = 0.77). This holds true after adjustment for confounders. Rate of transfusion of red blood cells were similar in patients with or without DAPT (35.4% vs. 28.6%, p = 0.488).

Conclusions

Bleeding on VA-ECMO is frequent. This registry recorded no statistical difference in bleeding in patients on dual antiplatelet therapy when compared to no antiplatelet therapy. When indicated, DAPT should not be withheld from VA ECMO patients.

Minimally invasive extracorporeal circulation resuscitation in hypothermic cardiac arrest

Current guidelines for the treatment of hypothermic cardiocirculatory arrest recommend extracorporeal life support and rewarming, using cardiopulmonary bypass or extracorporeal membrane oxygenation circuits. Both have design-related shortcomings which may result in prolonged reperfusion time or insufficient oxygen delivery to vital organs. This article describes clear advantages of minimally invasive extracorporeal circulation systems during emergency extracorporeal life support in hypothermic arrest. The technique of minimally invasive extracorporeal circulation for reperfusion and rewarming is represented by the case of a 59-year-old patient in hypothermic cardiocirculatory arrest at 25.3°C core temperature, with multiple trauma. With femoro-femoral cannulation performed under sonographic and echocardiographic guidance, extracorporeal life support was initiated using a minimally invasive extracorporeal circulation system. Perfusing rhythm was restored at 28°C. During rewarming on the mobile circuit, trauma surveys were completed and the treatment initiated. Normothermic weaning was successful on the first attempt, trauma surgery was completed and the patient survived neurologically intact. For extracorporeal resuscitation from hypothermic arrest, minimally invasive extracorporeal circulation offers all the advantages of conventional cardiopulmonary bypass and extracorporeal membrane oxygenation systems without their shortcomings.

Cardiopulmonary responses during the cooling and the extracorporeal life support rewarming phases in a porcine model of accidental deep hypothermic cardiac arrest

Background

This study aimed to assess cardiac and pulmonary pathophysiological responses during cooling and extracorporeal life support (ECLS) rewarming in a porcine model of deep hypothermic cardiac arrest (DHCA). In addition, we evaluated whether providing a lower flow rate of ECLS during the rewarming phase might attenuate cardiopulmonary injuries.

Methods

Twenty pigs were cannulated for ECLS, cooled until DHCA occurred and subjected to 30 min of cardiac arrest. In order to assess the physiological impact of ECLS on cardiac output we measured flow in the pulmonary artery using Doppler echocardiography as well as a modified thermodilution technique using the Swan-Ganz catheter (injection site in the right ventricle). The animals were randomized into two groups during rewarming: a group with a low blood flow rate of 1.5 L/min (LF group) and a group with a normal flow rate of 3.0 L/min (NF group). The ECLS temperature was adjusted to 5 °C above the central core. Cardiac output, hemodynamics and pulmonary function parameters were evaluated.

Results

During the cooling phase, cardiac output, heart rhythm and blood pressure decreased continuously. Pulmonary artery pressure tended to increase at 32 °C compared to the initial value (20.2 ± 1.7 mmHg vs. 29.1 ± 5.6 mmHg, p = 0.09). During rewarming, arterial blood pressure was higher in the NF than in the LF group at 20° and 25 °C (p = 0.003 and 0.05, respectively). After rewarming to 35 °C, cardiac output was 3.9 ± 0.5 L/min in the NF group vs. 2.7 ± 0.5 L/min in LF group (p = 0.06). At the end of rewarming under ECLS cardiac output was inversely proportional to the ECLS flow rate. Moreover, the ECLS flow rate did not significantly change pulmonary vascular resistance.

Discussion

Using a newly developed experimental model of DHCA treated by ECLS, we assessed the cardiac and pulmonary pathophysiological response during the cooling phase and the ECLS rewarming phase. Despite lower metabolic need during hypothermia, a low ECLS blood flow rate during rewarming did not improved cardiopulmonary injuries after rewarming.

Conclusion

A low ECLS flow rate during the rewarming phase did not attenuate pulmonary lesions, increased blood lactate level and tended to decrease cardiac output after rewarming. A normal ECLS flow rate did not increase pulmonary vascular resistance compared to a low flow rate. This experimental model on pigs contributes a number of pathophysiological findings relevant to the rewarming strategy for patients who have undergone accidental DHCA.

Ketamine use in current clinical practice

After nearly half a century on the market, ketamine still occupies a unique corner in the medical armamentarium of anesthesiologists or clinicians treating pain. Over the last two decades, much research has been conducted highlighting the drug's mechanisms of action, specifically those of its enantiomers. Nowadays, ketamine is also being utilized for pediatric pain control in emergency department, with its anti-hyperalgesic and anti-inflammatory effects being revealed in acute and chronic pain management. Recently, new insights have been gained on ketamine's potential anti-depressive and antisuicidal effects. This article provides an overview of the drug's pharmacokinetics and pharmacodynamics while also discussing the potential benefits and risks of ketamine administration in various clinical settings.

The chain of survival in hypothermic circulatory arrest: encouraging preliminary results when using early identification, risk stratification and extracorporeal rewarming

Background

The prognosis in hypothermic cardiac arrest is frequently good despite prolonged period of hypoperfusion and cardiopulmonary resuscitation. Apart from protective effect of hypothermia itself established protocols of treatment and novel rewarming techniques may influence on outcome.

The purpose of the study was to assess the outcome of patients with hypothermic circulatory arrest treated by means of arterio-venous extracorporeal membrane oxygenation (ECMO) according to locally elaborated protocol in Severe Accidental Hypothermia Center in Cracow, Poland.

Methods

Prospective observational case-series study – all patients with confirmed hypothermic cardiac arrest consulted with hypothermia coordinator were accepted for extracorporeal rewarming, unless contraindications for ECMO were observed (active bleeding).

Results

The study population consisted of 10 patients (7 male, median age 48.5 years). The core temperature measured esophageally was 16.9–28.4 °C, median 22 °C. On admission 5 patients presented with asystole and 5 with ventricular fibrillation. Duration of circulatory arrest before ECMO implantation was 107 to 345 min (median 156 min). The duration of ECMO support was 1.5 to 91 h (median 22 h). Cardiorespiratory stability and full neurologic recovery was achieved in 7 patients. The duration of mechanical ventilation was 88–437 h (median 177 h) and the length of stay in the ICU was 8–26 days (median 15 days). All survivors had mildly impaired (1 patient, LVEF 40 %) or preserved (6 patients, LVEF 55–65 %) left ventricular systolic function at the time of discharge from ICU. The cause of death of non-survivors (three patients) was acute myocarditis, massive retroperitoneal bleeding, and massive gastrointestinal bleeding.

Discussion and Conclusions

Our data confirm the high survival rate (70 %) and excellent neurologic outcome in hypothermic cardiac arrest. The following key elements seem to impact the final prognosis: the appropriate coordination of the rescue operation, immediate high-quality CPR (preferably using mechanical chest compression system) and application of ECMO for rewarming and cardiorespiratory support.

Problems and Pitfalls of Qualification for Extracorporeal Rewarming in Severe Accidental Hypothermia

OBJECTIVES

When establishing the Severe Hypothermia Treatment Centre, certain problems and pitfalls regarding the qualification for extracorporeal rewarming were encountered. The authors shared their experience and opened a discussion with other centers that deal with severe, accidental hypothermia.

DESIGN

Retrospective analysis of medical records of all patients examined by the hypothermia coordinator.

SETTING

Patients consulted and treated by the Severe Hypothermia Treatment Centre.

PARTICIPANTS

Patients who underwent accidental hypothermia.

INTERVENTIONS

From July 2013 until January 2016, hypothermia coordinators at the Severe Hypothermia Treatment Centre examined the cases of 152 hypothermic patients. Of those cases, 127 patients were subjected to noninvasive rewarming in referral hospitals and 25 were accepted to the center for extracorporeal rewarming.

MEASUREMENTS AND MAIN RESULTS

Difficulties that deferred or delayed the implementation of extracorporeal membrane oxygen rewarming were identified and addressed, including low platelet/red blood count, intraperitoneal fluid of unknown origin, abnormal results of head computed tomography, extremes of age, bleeding from the external auditory meatus, inaccuracy of infrared-based thermometers, iatrogenic trauma to the femoral vessels, chronic/terminal comorbidities, poisonings, pregnancy, hypoglycemia, hemodynamic stability despite severe hypothermia, and decontamination protocol.

CONCLUSIONS

The problems discussed may delay the use of extracorporeal membrane oxygen rewarming in hypothermic patients but should not discourage medical teams from the implementation of extracorporeal rewarming. The prognosis for severe hypothermia is favorable, even with a long resuscitation time and low core temperatures.

Accidental hypothermia in severe trauma

Hypothermia, along with acidosis and coagulopathy, is part of the lethal triad that worsen the prognosis of severe trauma patients. While accidental hypothermia is easy to identify by a simple measurement, it is no less pernicious if it is not detected or treated in the initial phase of patient care. It is a multifactorial process and is a factor of mortality in severe trauma cases. The consequences of hypothermia are many: it modifies myocardial contractions and may induce arrhythmias; it contributes to trauma-induced coagulopathy; from an immunological point of view, it diminishes inflammatory response and increases the chance of pneumonia in the patient; it inhibits the elimination of anaesthetic drugs and can complicate the calculation of dosing requirements; and it leads to an over-estimation of coagulation factor activities. This review will detail the pathophysiological consequences of hypothermia, as well as the most recent principle recommendations in dealing with it.