Accidental hypothermia

Hibernation and hemostasis

Hibernating mammals have developed many physiological adaptations to accommodate their decreased metabolism, body temperature, heart rate and prolonged immobility without suffering organ injury. During hibernation, the animals must suppress blood clotting to survive prolonged periods of immobility and decreased blood flow that could otherwise lead to the formation of potentially lethal clots. Conversely, upon arousal hibernators must be able to quickly restore normal clotting activity to avoid bleeding. Studies in multiple species of hibernating mammals have shown reversible decreases in circulating platelets, cells involved in hemostasis, as well as in protein coagulation factors during torpor. Hibernator platelets themselves also have adaptations that allow them to survive in the cold, while those from non-hibernating mammals undergo lesions during cold exposure that lead to their rapid clearance from circulation when re-transfused. While platelets lack a nucleus with DNA, they contain RNA and other organelles including mitochondria, in which metabolic adaptations may play a role in hibernator's platelet resistance to cold induced lesions. Finally, the breakdown of clots, fibrinolysis, is accelerated during torpor. Collectively, these reversible physiological and metabolic adaptations allow hibernating mammals to survive low blood flow, low body temperature, and immobility without the formation of clots during torpor, yet have normal hemostasis when not hibernating. In this review we summarize blood clotting changes and the underlying mechanisms in multiple species of hibernating mammals. We also discuss possible medical applications to improve cold preservation of platelets and antithrombotic therapy.

Characteristics of antipsychotic drug-induced hypothermia in psychogeriatric inpatients

OBJECTIVE

Hypothermia is a potentially lethal adverse reaction to typical and atypical antipsychotic drugs (APD). Among predisposing factors are advanced age and comorbid somatic diseases. The aim of this study was to assess the incidence of hypothermia and quantify risk factors.

METHOD

Charts of N = 3002 psychogeriatric inpatients were screened for incidence of hypothermia (body core temperature <35.0°C). The frequency of hypothermia was compared between patients treated with versus without APD and, within the sample of APD-treated patients, for (1) specific APD, (2) sex, (3) main diagnosis, and (4) age.

RESULTS

N = 54 cases (2.6%) of hypothermia occurred in APD-treated patients and 12 cases (1.3%) in non-APD-treated patients (p = 0.024). In APD-treated patients, only male sex (p = 0.038) and pipamperone were associated with a higher incidence of hypothermia (p = 0.0017). Whereas the main diagnosis delirium showed a trend to significance, age did not correlate with hypothermia.

CONCLUSION

Medication with pipamperone was associated with an increased risk of hypothermia. The advanced age of our sample might as well explain the high incidence of hypothermia within our sample and the failure to detect high age as a risk factor due to a ceiling effect.

Hypothermia due to Antipsychotic Medication: A Systematic Review

BACKGROUND

Hypothermia is a rare, but potentially fatal adverse effect of antipsychotic drug (APD) use. Although the opposite condition, hyperthermia, has been researched extensively in the context of the malignant antipsychotic syndrome, little is known about hypothermia due to APDs.

OBJECTIVE

This study aimed to review the literature on hypothermia in the context of APD use, and formulate implications for research and clinical care.

METHODS

A systematic search was made in PubMed and Ovid Medline.

RESULTS

The literature search yielded 433 articles, including 57 original case descriptions of hypothermia developed during APD use with non-toxic plasma levels. All cases together indicate that the risk of developing hypothermia is highest during the 7 days following initiation, or increase in dosage, of APDs, especially in the presence of additional predisposing factors, such as advanced age, exposure to cold, adjuvant use of benzodiazepines, and (subclinical) hypothyroidism. In addition, data derived from drug-monitoring agencies suggest that the prevalence of APD-related hypothermia is at least 10 times higher than suggested by the literature.

CONCLUSION

We conclude that health-care professionals need to monitor the body temperature of patients starting with (an increased dose of) APDs for a duration of 7-10 days to prevent hypothermia, especially in the presence of multiple risk factors. Moreover, systematic studies are needed to establish the actual prevalence of APD-related hypothermia as well as the relative risk for individual APDs.

Therapeutic peritoneal lavage with warm saline solution as an option for a critical hypothermic trauma patient

INTRODUCTION

In this paper, we present the case of a 63-year-old woman, who was found in her flat lying unconscious on the floor for an unknown time. At the time of admission, her core temperature was 24 °C and ventricular fibrillation was detected on the electrocardiogram (ECG). Because of the unstable conditions, the persistent nonperfusing cardiac rhythm and the dramatically inhibited coagulation cascade, a peritoneal lavage connected to a rapid infuser was performed for rewarming, instead of using a transportable heart-lung machine and a haemodialysis device. After a prolonged cardiopulmonary resuscitation (CPR), the patient could be transferred to the intensive care unit (ICU) in a stable condition. After 40 days in the ICU, recovery was fast, and another month of treatment later, she could be discharged back home without any discomfort.

CONCLUSION

This report illustrates the successful use of the peritoneal lavage for rewarming a severely hypothermic patient without any extracorporeal rewarming device. Furthermore, it can be used in nearly every hospital if the necessary equipment is affordable. It is demonstrated that this technique is able to provide good outcomes for all victims of accidental hypothermia.

Severe hypothermia with cardiac arrest: complete neurologic recovery in a 4-year-old child

A 4-year-old girl was lost for 17 hours in a snowstorm. Upon discovery, her core temperature was 72 degrees F (22 degrees C). While undergoing endotracheal intubation in the emergency department, she experienced sudden ventricular fibrillation and cardiac arrest. Closed chest cardiopulmonary resuscitation (CPR) was instituted, and standard rewarming measures were begun. Despite this, neither core temperature, nor the patient's arrhythmia, changed. An infraumbilical "mini-laparotomy" incision was made, with placement of a large silicone peritoneal dialysis catheter into the abdomen. This was then connected to a rapid infuser device, with the delivery of 1L of warmed, normal saline every 90 seconds. The core temperature reached 29 degrees C in 15 minutes, and a palpable pulse was detected. Lavage was continued until core temperature reached 34 degrees C, at which time transport to the pediatric intensive care unit was arranged. She was extubated the next day and discharged home, on the fourth hospital day, with apparent complete neurologic recovery. This is the first report of the successful use of rapid high-volume peritoneal lavage for the treatment of accidental severe hypothermia in a pediatric patient.

Transcutaneous pacing in a hypothermic-dog model

STUDY OBJECTIVE

To evaluate the hemodynamic response to transcutaneous pacing (TCP) during rewarming from hypothermia.

METHODS

We conducted a prospective, controlled laboratory investigation using 20 mongrel dogs. The animals were anesthetized, intubated, and mechanically ventilated. Arterial pressure, core temperature, and cardiac rhythm were continuously monitored. All dogs were cooled to a core temperature of 27 degrees C; experimental animals were then subjected to TCP with active rewarming, and control animals underwent sham transcutaneous pacing and rewarmed in the same manner. Serial hemodynamic measurements, time to rewarming, and cardiac isoenzyme concentrations were analyzed.

RESULTS

Rewarming was accomplished significantly faster in the paced group (171.5 +/- 31.5 minutes) than in the control group (254 +/- 55.9 minutes, P < .05). After rewarming, the mean cardiac index in the paced dogs returned to 84% of baseline, compared with 63% of baseline in the nonpaced group (P < .05). None of the paced animals demonstrated significant hemodynamic deterioration, potentially lethal arrhythmias, or other evidence of myocardial injury.

CONCLUSION

TCP is safe, effective and easily implemented in dogs. In this small series of dogs, TCP restored and maintained hemodynamic stability and allowed the hypothermic animals to rewarm in half the time required by their nonpaced counterparts.

Epidemiology of hypothermia: fatalities and hospitalisations in New Zealand

BACKGROUND

Hypothermia occurs within domestic and non-residential settings. Most epidemiological data originate from the northern hemisphere, with little data being generally available concerning cases from New Zealand and Australia.

AIMS

The National Health Statistics Centre (New Zealand) records hospital discharges and deaths. This study isolated hypothermia cases, to quantify its incidence and identify risk groups.

METHODS

The morbidity and mortality files for the years 1979-86 (cases = 3,808,717) and 1977-86 (cases = 259,325; respectively) were searched by three investigators.

RESULTS

Hypothermia hospitalisations were identified (6.9 per 100,000 per year). There were 176 deaths from hypothermia, representing 0.07% of the 259,325 deaths from all causes for the same period (0.537 per 100,000 people per year); of these fatalities, 72.2% were classified as domestic, and 27.8% as non-residential; of the domestic fatalities, 86.6% were 65 + years and 35.5% of these were male. Within the non-residential category, 75.5% were aged 13-65, of which 94.6% were male. The hospitalisation incidence was 12.7 times the fatality incidence, with the majority of hospitalisations being of domestic origin (88.4% of total), and occurring mostly within the lower and upper age extremes. Neonatal domestic hypothermia accounted for 72.6% of all domestic hospitalisations, and the elderly constituted 72.0% of the remaining cases. The proportion of New Zealand fatalities caused by hypothermia was 0.067%; lower than reported in the United Kingdom.

CONCLUSIONS

The two main non-neonatal groups contributing to cases of hypothermia were males aged 13-65 years, and the elderly. In the aged, the proportion of hypothermia-related deaths was no different from that associated with other disorders, however, the case-fatality ratio was three times greater, highlighting the need for improving prevention and management strategies.

Efficacy and safety of prehospital rewarming techniques to treat accidental hypothermia

STUDY OBJECTIVE

Evaluation of inhalation rewarming and peripheral rewarming for reducing the body core temperature afterdrop and accelerating rewarming rates.

DESIGN

Prospective, randomized human experimentation.

SETTING

Physiology laboratory with cooling during ice water immersion and rewarming in rescue sleeping bags in a windy, cold (2 C) air environment.

TYPE OF PARTICIPANTS

Eight experimental subjects who were cooled to clinical hypothermia (35.0 C), rectal or esophageal temperature (Tr or Te).

MEASUREMENTS AND MAIN RESULTS

Afterdrop was characterized as minimum Tr and Te plus recovery time to the Tr and Te levels at the onset of rewarming. Rewarming rates 30 and 60 minutes after maximum afterdrop for Tr and Te were measured. By analysis of variance, inhalation rewarming and peripheral rewarming evaluated separately or in combination did not significantly influence afterdrop duration, afterdrop recovery, or rewarming rates.

CONCLUSION

With no physiological benefit and hazards identified (inhalation rewarming burning the face, peripheral rewarming eliminating carbon monoxide equal to 300 to 600 ppm), inhalation rewarming and peripheral rewarming are not recommended for the prehospital treatment of mild hypothermia.

Rewarming by hemodialysis for hypothermia: failure of heparin to prevent DIC

Disseminated intravascular coagulation (DIC) is an infrequent but known complication of hypothermic injury. Previous work with a dog model had indicated that DIC could be prevented if the animals were treated with heparin prior to rewarming. We report here the case of a young man treated with core rewarming by hemodialysis who developed DIC despite the use of heparin during dialysis.

Comparison of gastric lavage and thoracic cavity lavage in the treatment of severe hypothermia in dogs

A study was undertaken to compare warm gastric (Group 1) and closed thoracic cavity (Group 2) lavage for rewarming severely hypothermic dogs. Adult mongrel dogs were monitored by intra-arterial catheter, central venous catheter, and ECG, and by central venous, esophageal, and rectal temperature probes. Animals were externally cooled to an average of 21.2 C using ice bags. Eight Group 1 and eight Group 2 animals underwent continuous warm saline gastric or closed thoracic cavity lavage, respectively, using afferent and efferent nasogastric and thoracostomy tubes. No animal suffered ventricular fibrillation during tube placement. The closed lavage system consisted of a high-efficiency heat exchanger, a roller pump infusion device, and a heat exchange fluid bath. The lavage fluid circulated at a flow rate of 550 mL/min and a temperature of 39 C. Thoracic lavage animals were followed clinically for 24 hours for evidence of complications, then euthanized and autopsied. The mean time required to rewarm the animals 10 C by central venous temperature probe was 210.9 +/- 18.6 minutes for the gastric group and 99.3 +/- 23.0 minutes for the thoracic group (P less than .001). Rectal temperature consistently lagged behind central venous temperature during both the cooling and rewarming phases in both treatment groups. All of the thoracic lavage animals made an uneventful recovery. Continuous warm saline thoracic cavity lavage for core rewarming of severely hypothermic dogs is more effective than gastric lavage, and appears to be safe.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of bretylium tosylate as prophylaxis and treatment in hypothermic ventricular fibrillation in the canine model

We conducted a study to determine if bretylium tosylate (BT) is effective in the prophylaxis and treatment of hypothermic ventricular fibrillation (VF) in the setting of various maneuvers thought to induce this lethal arrhythmia. Twenty-two mongrel dogs were cooled to 24 C after being placed in a cold room. At 24 C, a double-blinded placebo or BT solution was infused. The dogs then were removed from the cold. They underwent the following sequential maneuvers: oral endotracheal extubation and intubation, central line and nasogastric tube placement, vigorous movement, and Swan-Ganz catheter insertion. If VF ensued, arterial blood gases were drawn, and BT was given only if refractory to countershock and epinephrine. Of the dogs that were given placebo, six of 11 (55%) fibrillated with manipulation, as compared with one of 11 (9%) dogs pretreated with BT (P = .067). Three of the 11 dogs that received BT fibrillated within minutes of its infusion. In the placebo dogs that fibrillated, four required BT and two defibrillated with countershock alone or with epinephrine prior to achieving stable rhythms.

Profound accidental hypothermia treated with peritoneal dialysis

In five women and two men, profound accidental hypothermia--core temperature on admission 24-28 degrees C--was treated with peritoneal dialysis. In two cases 16 gauge intravenous catheters were used, without difficulty, for the dialysis. Six of the seven patients were intoxicated by hypnotics, and four also by alcohol. Two patients died--one 38 hours after admission due to acute myoglobinuric renal failure arising from gangrene of an arm, and the other after 71 hours, due to cerebral herniation. The remaining five patients recovered without cerebral sequelae. Peritoneal dialysis is a useful procedure for rewarming patients with profound accidental hypothermia.

Severe exposure hypothermia: a resuscitation protocol

Although hypothermia has been described as an emergency in suspended animation, severe degrees of hypothermia mandate appropriate aggressive intervention. Because of cardiac instability with core temperature below 28 C, aggressive invasive rewarming by F-F partial bypass is often ideal in this setting. In contrast, a gentle approach in other therapeutic maneuvers is equally important to prevent iatrogenic induction of VF in nonarrested victims. If the only definite criterion for diagnosis of death in hypothermia is failure to respond to resuscitation and rewarming, successful resuscitation must carefully balance aggressive and gentle interventions. Because CPR protocols involve legal as well as medical questions, additional prospective data are especially critical for resolving controversies in the initial management of profound exposure hypothermia.

Neardrowning and cold water immersion

Though usually preventable, drowning remains a major cause of accidental death in our society. The lethal common denominator in drowning and neardrowning deaths is hypoxia. Aggressive treatment both at the scene and in the hospital is recommended even in those who initially appear lifeless. Hypothermia and the diving reflex probably explain the incredible survival stories in neardrowning. Remember the maxim in cold water immersion: "One is not dead until warm and dead!"

Thermal and cardiovascular changes during three methods of resuscitation from mild hypothermia

The interrelations among core temperatures (cardiac, esophageal, tympanic, rectal), skin temperature, and cardiovascular function (cardiac output, arterial pressure, heart rate, total peripheral resistance) were studied in a conscious subject during entry into mild hypothermia through cold water (10 degrees C) immersion, and during rewarming by three basic procedures: peripheral heat donation (bath); core heat donation (inhalation); and no exogenous heat (spontaneous). Swan-Ganz catheterization of the heart enabled measurement of cardiac temperature as well as cardiac output by the thermal dilution method. During cooling, all sites of core temperature measurement showed similar rates of entry into hypothermia. However, during the rewarming procedures, divergent patterns of temperature change among the four sites occurred. Rectal and tympanic temperatures were not representative of cardiac temperature, but esophageal temperature was, and is therefore most suitable as a criterion for experimental evaluation of the thermal benefit of various core rewarming techniques. During the first 30 min of rewarming, rates of increase in cardiac temperature for bath, inhalation, and spontaneous procedures varied according to the proportions 4:2:1, respectively. No afterdrop of cardiac temperature occurred with the inhalation or spontaneous procedures, but an afterdrop at this site did occur during the first 15 min of bath rewarming as soon as skin temperature was greater than 30 degrees C. This afterdrop coincided with cardiovascular changes including abrupt decreases in arterial pressure and total peripheral resistance, along with increases in heart rate and cardiac output. Such evidence of increased peripheral circulation was not observed with the inhalation and spontaneous methods. The findings relate to experimental evaluation of rewarming techniques and principles for resuscitation of hypothermia victims, especially in the first-aid situation.

Accidental hypothermia: a community hospital perspective

Hypothermia, especially in an urban environment, is often an unsuspected and therefore underdiagnosed clinical entity. Of 60 cases recorded over a two-year period in a typical community hospital in Philadelphia, 26 (43%) involved patients under 60 years of age; ambient air temperatures at admission exceeded 50 F (10 C) in 28 (47%) of the 60 cases. Hypothermia thus cannot necessarily be attributed to advanced age or cold climates or seasons. The severity of hypothermia did not correlate with either the season of the year or the ambient air temperature. Diabetes and alcohol abuse appear to be risk factors for hypothermia, being present in 18 (30%) and 14 (23%) of our patients, respectively. Every emergency department should have a protocol for identification and management of the hypothermia victim to allow timely institution of appropriate rewarming techniques.

Extreme hypothermia and ventricular fibrillation

A 31-year-old white man with a core temperature of 60.8 F (16 C) and ventricular fibrillation was successfullly resuscitated using active core and external rewarming techniques. Rectal temperature at the time of reestablished electromechanical cardiac activity was 68 F (20 C), a temperature previously thought to be incompatible with successful resuscitation from venticular fibrillation. We are not aware of previous case reports describing survival following a lower documented core temperature.

Hypothermia: quantitative aspects of therapy

Quantitative aspects of various methods of warming are presented comparing the peripheral method of warm bath immersion to the central method of ventilation with heated water-saturated air, infusion of warmed intravenous solutions, peritoneal lavage with warmed solutions, and hemodialysis or cardiopulmonary bypass. The need to convert arterial blood gas results for body temperature is emphasized. Two cases demonstrate combined use of peripheral warming using warming mattress and blankets and central warming with ventilation and infusion.