The treatment of hypothermia

Prehospital Active and Passive Warming in Trauma Patients

OBJECTIVE

Hypothermia is common among trauma patients and can lead to a serious rise in morbidity and mortality. This study was performed to investigate the effect of active and passive warming measures implemented in the prehospital phase on the body temperature of trauma patients.

METHODS

In a multicenter, multinational prospective observational design, the effect of active and passive warming measures on the incidence of hypothermia was investigated. Adult trauma patients who were transported by helicopter emergency medical services (HEMS) or ground emergency medical services with an HEMS physician directly from the scene of injury were included. Four HEMS/ground emergency medical services programs from Canada, the United States, and the Netherlands participated.

RESULTS

A total of 80 patients (n = 20 per site) were included. Eleven percent had hypothermia on presentation, and the initial evaluation occurred predominantly within 60 minutes after injury. In-line fluid warmers and blankets were the most frequently used active and passive warming measures, respectively. Independent risk factors for a negative change in body temperature were transportation by ground ambulance (odds ratio = 3.20; 95% confidence interval, 1.06-11.49; P = .03) and being wet on initial presentation (odds ratio = 3.64; 95% confidence interval, 0.99-13.36; P = .05).

CONCLUSION

For adult patients transported from the scene of injury to a trauma center, active and passive warming measures, most notably the removal of wet clothing, were associated with a favorable outcome, whereas wet patients and ground ambulance transport were associated with an unfavorable outcome with respect to temperature.

Regulation of Coagulation Abnormalities and Temperature in Organ Donors

The 3 most common reasons for abnormal coagulation of blood in organ donors result from prior medications, consumption or dilution of coagulation factors and platelets during massive transfusion, and disseminated intravascular coagulation. Evaluation and treatment of these conditions are reviewed, and recommendations are provided for ordering appropriate laboratory tests and blood bank products.

Extended stability of intravenous 0.9% sodium chloride solution after prolonged heating or cooling

PURPOSE

The primary objective of this study was to evaluate the stability and sterility of an intravenous 0.9% sodium chloride solution that had been cooled or heated for an extended period of time.

METHODS

Fifteen sterile 1 L bags of 0.9% sodium chloride solution were randomly selected for this experiment. Five bags were refrigerated at an average temperature of 5.2°C, 5 bags were heated at an average temperature of 39.2°C, and 5 bags were stored at an average room temperature of 21.8°C to serve as controls. All samples were protected from light and stored for a period of 199 days prior to being assayed and analyzed for microbial and fungal growth.

RESULTS

There was no clinically significant difference in the mean sodium values between the refrigerated samples, the heated samples, and the control group. There were no signs of microbial or fungal growth for the duration of the study.

CONCLUSION

A sterile intravenous solution of 0.9% sodium chloride that was heated or cooled remained stable and showed no signs of microbial or fungal growth for a period of 199 days. This finding will allow hospitals and emergency medical technicians to significantly extend the expiration date assigned to these fluids and therefore obviate the need to change out these fluids every 28 days as recommended by the manufacturer.

Susceptibility to mortality related to temperature and heat and cold wave duration in the population of Stockholm County, Sweden

Background

Ambient temperatures can cause an increase in mortality. A better understanding is needed of how health status and other factors modify the risk associated with high and low temperatures, to improve the basis of preventive measures. Differences in susceptibility to temperature and to heat and cold wave duration are relatively unexplored.

Objectives

We studied the associations between mortality and temperature and heat and cold wave duration, stratified by age and individual and medical factors.

Methods

Deaths among all residents of Stockholm County between 1990 and 2002 were linked to discharge diagnosis data from hospital admissions, and associations were examined using the time stratified case-crossover design. Analyses were stratified by gender, age, pre-existing disease, country of origin, and municipality level wealth, and adjusted for potential confounding factors.

Results

The effect on mortality by heat wave duration was higher for lower ages, in areas with lower wealth, for hospitalized patients younger than age 65. Odds were elevated among females younger than age 65, in groups with a previous hospital admission for mental disorders, and in persons with previous cardiovascular disease. Gradual increases in summer temperatures were associated with mortality in people older than 80 years, and with mortality in groups with a previous myocardial infarction and with chronic obstructive pulmonary disease (COPD) in the population younger than 65 years. During winter, mortality was associated with a decrease in temperature particularly in men and with the duration of cold spells for the population older than 80. A history of hospitalization for myocardial infarction increased the odds associated with cold temperatures among the population older than 65. Previous mental disease or substance abuse increased the odds of death among the population younger than 65.

Conclusion

To increase effectiveness, we suggest preventive efforts should not assume susceptible groups are the same for warm and cold days and heat and cold waves, respectively.

[Severe accidental hypothermia with cardiac arrest and extracorporeal rewarming. A case report of a 2-year-old child]

In patients with severe hypothermia and cardiac arrest, active rewarming is recommended by extracorporeal circulation with cardiopulmonary bypass. The current guidelines for resuscitation of the European Resuscitation Council now include the recommendation regarding patients with hypothermia remaining comatose after initial resuscitation to accomplish an active rewarming only up to a temperature of 32-34 degrees C and to maintain a mild hypothermia for 12-24 h. We report the case of a 2-year-old boy who suffered from severe hypothermia after falling into ice-cold water. On discovery cardiac arrest with asystole was present and the first measured temperature was 23.8 degrees C. Resuscitation led to restoration of spontaneous circulation. The patient was rewarmed by extracorporeal circulation with cardiopulmonary bypass to 33 degrees C then mild hypothermia was maintained for a further 12 h. On the third day after the accident the patient was extubated and after a further 9 days was discharged without any sequelae.

Active internal re-warming using a centrifugal pump and heat exchanger following haemorrhagic shock, surgical trauma and hypothermia in a porcine model

BACKGROUND

The centrifugal vortex blood pump (CVBP) using heparin-bonded circuitry allows re-warming of hypothermic trauma patients without anticoagulation. Study objectives were to confirm efficacy, and to characterise the physiology of CVBP re-warming in a porcine model.

METHODS

Sixteen pigs were randomised to conventional or CVBP re-warming. They were bled to a mean arterial pressure of 30 mmHg and cooled to 29 degrees C. A physiological analysis was recorded during resuscitation to normo-tension and re-warming back to 37 degrees C.

RESULTS

CVBP animals re-warmed significantly faster: 85.0+16.4 min versus 217.4+49.3 min (p<0.0001). Activated clotting time was significantly elevated in both groups at 29 degrees C with a marked trend to normalise faster in CVBP pigs. The peak cardiac index (CI) was significantly lower (1.14+0.68 versus 4.83+1.50 L/(min m2), while the systemic vascular resistance (SVR) was significantly higher (4239.9+1173.0 versus 1472.6+451.2 dyn x S x m2/cm5) with CVBP (p<0.001).

CONCLUSION

CVBP is simple and very effective at re-warming hypothermic animals and may also reverse coagulopathy more quickly. Physiological derangements of elevated SVR and diminished CI require further study to elaborate underlying aetiology, and define optimal re-warming strategies.

Kardiopulmonale Reanimation nach Heroinintoxikation und Hypothermie

We present the case of a 21-year-old female drug addict with severe accidental hypothermia (core body temperature 27.5 degrees C) and cardiorespiratory arrest. After successful cardiopulmonary resuscitation the patient was actively internally rewarmed without the use of extracorporal circulation. Although at the first clinical presentation the patient appeared to be dead, an excellent neurological outcome was achieved. This case report reviews the epidemiology, pathophysiology, prognostic markers and the therapeutic approaches of severe hypothermia.

Cold Injury Syndrome and Neurodevelopmental Changes in Survivors

BACKGROUND

The aim of this study was to extend and develop knowledge of the clinical parameters of cold injury syndrome (CIS) in hypothermic infants and newborns, so that morbidity, mortality, and neurodevelopmental disturbances associated with the condition can be reduced.

METHODS

This retrospective, 10-year cohort study investigated 103 hypothermic infant and newborn patients (aged 0-60 days) admitted to the Pediatric Department between January 1, 1976 and December 31, 1985. Medical records of 67 survivors and 36 children who died were analyzed. Of the survivors, 24 consented to undergo assessment of neuropsychological and neurodevelopmental outcomes.

RESULTS

At presentation, all patients manifested cold skin and limbs, while 96 (93.2%) were sleepy, hypotonic and inactive. Cyanosis with bradycardia, bradypnea, and apneic crisis (AC) was observed in 80 (77.7%) patients, and 65 (63.1%) demonstrated diffuse intravascular coagulation (DIC). Pulmonary hemorrhage, AC, respiratory distress syndrome, and DIC represented the primary causes of death. Higher body temperatures on admission reduced the risk of death. Of the 24 patients assessed for neuropsychological and neurodevelopmental outcomes, all but one had normal intellectual capabilities, whereas 16 (66.7%) showed signs of neurodevelopmental disturbances.

CONCLUSIONS

The severity of hypothermia, leukopenia, and thrombocytopenia with DIC correlates with prognosis and death rate. Hypothermia in infants and newborns can cause psychological and neurodevelopmental disturbances in survivors.

Successful use of venovenous extracorporeal membrane oxygenation in accidental hypothermic cardiac arrest

Cardiopulmonary bypass is usually used for rewarming and for providing cardiac support in patients with severe hypothermia and cardiovascular instability. We report the first case of accidental severe hypothermia associated with prolonged cardiac arrest that was successfully managed by venovenous extracorporeal membrane oxygenation.

Refractory ventricular fibrillation in accidental hypothermia: salvage with cardiopulmonary bypass

A 20-year old woman presented with prolonged refractory ventricular fibrillation and pulmonary oedema following hypothermia while she was under self-administered heroin in an attempt to commit suicide. She was successfully resuscitated with cardiopulmonary bypass for core rewarming and internal defibrillation.

Use of a Centrifugal Vortex Blood Pump and Heparin-Bonded Circuit for Extracorporeal Rewarming of Severe Hypothermia in Acutely Injured and Coagulopathic Patients

BACKGROUND

Standard rewarming methods for posttraumatic hypothermia are ineffective or require systemic heparinization. Centrifugal vortex blood pumps (CVBPs), heparin-bonded circuits, and, potentially, percutaneous access techniques, facilitate the institution of an extracorporeal circulation by noncardiac surgeons.

METHODS

Seven severely hypothermic patients requiring emergent operative intervention were rewarmed intraoperatively using the CVBP with heparin-bonded circuitry.

RESULTS

Patients were critically ill (average Injury Severity Score of 43.5 [SD, 13.6] for the traumatized patients). The mean temperature before rewarming was 31.5 degrees C (SD, 1.6 degrees C). The CVBP outflow site was the common femoral vein in all patients, with the inflow into the superficial femoral artery (n = 2), contralateral common femoral vein (n = 2), and internal jugular vein (n = 3). The mean time to rewarm to 37 degrees C was 73.3 (SD, 30.5) minutes. All patients survived the initial operation, although the ultimate survival was 43%.

CONCLUSION

Noncardiac surgeons can effectively use an extracorporeal rewarming strategy incorporating a heparin-bonded CVBP to rapidly rewarm hypothermic coagulopathic patients undergoing surgery.

Pilot investigation of hypothermia in neonates receiving extracorporeal membrane oxygenation

BACKGROUND

Infants requiring extracorporeal membrane oxygenation (ECMO) support represent a high risk group in terms of cerebral injury. Mild hypothermia both during and after cerebral hypoxic ischaemia appears to be a promising strategy for offering neuroprotection.

OBJECTIVE

To investigate whether mild hypothermia was both feasible and safe in infants receiving ECMO as a prelude to any formal assessment of this approach in a randomised trial.

METHODS

Twenty infants (body weight less than 5 kg) with severe cardiopulmonary insufficiency, referred for ECMO support at Glenfield Hospital, Leicester, were enrolled in this study. Twenty consecutive infants (compromising four groups of five) were studied. Baseline data were obtained from a control group who were run throughout their course at 37 degrees C. The patients in the next group were managed with a core temperature of 36 degrees C for the first 12 hours of their ECMO run, before being warmed up to 37 degrees C. After successful completion, the next group of five were cared for at 35 degrees C for the first 12 hours, and, there having been no previous complications, the final group were cared for at 34 degrees C for the first 12 hours. Patients were assessed clinically and biologically. In addition to routine laboratory tests, cytokines (interleukin 6, interleukin 8, tumour necrosis factor alpha, and C reactive protein) were measured and coagulation tests (D-dimer, thrombin-antithrombin III complex, plasmin-alpha(2)-antiplasmin complex) were performed serially for five days.

RESULTS

There were no significant differences among the four groups in gestational age, birth weight, age at the time of ECMO, Apgar scores at one and five minutes, pH before cannulation, oxygenation index, duration of ECMO, and survival rate to discharge from hospital. No adverse effects of mild hypothermia were found on patient management during ECMO. Laboratory data for up to five days of ECMO also showed no difference among the four groups.

CONCLUSION

Mild hypothermia (34 degrees C) for the initial 12 hours of an ECMO run is feasible.

Accidental hypothermia and active rewarming: the metabolic and inflammatory changes observed above and below 32 degrees C

OBJECTIVES

In accidental hypothermia the underlying physiological mechanisms responsible for poor outcome during rewarming through 32 degrees C remain obscure, although possible associations include changes in acid-base balance, divalent cations, and inflammatory markers. This study investigated the metabolic and inflammatory changes that occur during the rewarming of hypothermic patients.

METHODS

Eight patients, four men and four women, age 45 to 85 years, admitted with core temperatures <35 degrees C were included in the study. Patients were rewarmed with dry warm blankets and fluid replaced by crystalloid at 40 degrees C. Bloods for pH, ionised calcium (Ca(2+)) and magnesium (Mg(2+)), parathyroid hormone (PTH), interleukin 1 (IL1), interleukin 6 (IL6), tissue necrosis factor alpha (TNFalpha), were collected at presentation, during rewarming, and at 24 hours.

RESULTS

Four patients were admitted with mild (32 degrees -35 degrees C) and four with moderate (28 degrees -32 degrees C) hypothermia. Rewarming to 32 degrees C had no significant effect on the presenting acidosis (p=0.1740), although above 32 degrees C pH increased with temperature (p<0.0001). There was a negative correlation between pH and both Ca(2+) (p=0.0005) and Mg(2+) (p=0.0488) below 32 degrees C; above this temperature the relation was significant only for Ca(2+) (p=0.0494). PTH and Ca(2+) correlated positively (p=0.0041) and negatively (p=0.0039) below and above 32 degrees C respectively. There was no relation between IL1 or TNFalpha with Ca(2+) during rewarming, but IL6 and Ca(2+) correlated positively (p=0.0039) and negatively (p=0.0018) when presentation temperature was below and above 32 degrees C respectively.

CONCLUSIONS

During rewarming pH remains unchanged until patient temperature approaches 32 degrees C. Ca(2+) and Mg(2+) decline is associated with the pH increase above 32 degrees C. Poor outcome is associated with presentation temperature (<32 degrees C), non-physiological correlation between IL6-PTH-Ca(2+), and age (>or=84 years).

A new method of continuous venovenous rewarming

PURPOSE

Hypothermia is a significant problem in medicine and is part of a deadly triad, including hypothermia, acidosis, and coagulopathy. Multiple methods of rewarming are used to treat moderate hypothermia. The purpose of this study was to compare the effectiveness of continuous venovenous rewarming (CVVR) using the FMS 2000 (Belmont Instrument Corp., Billerica, Massachusetts) in conjunction with external rewarming techniques versus external rewarming alone in the porcine model.

METHODS

Ten subject animals, each weighing approximately 40 kg, were evenly divided and randomly assigned to either a control group using external rewarming techniques alone or the CVVR group utilizing the FMS 2000 in addition to the external rewarming techniques used in the control group. Hypothermia was induced in the swine model using cold water immersion to achieve a core temperature of 30 degrees C. Both esophageal and rectal temperature probes were used to monitor and record core body temperatures every 15 minutes during the experiment. Each study animal was then rewarmed until a core temperature of at least 37 degrees C was recorded in both the esophageal and rectal probes. The animals were observed clinically for 3 days after the study.

RESULTS

The average time required to rewarm the control group was 253 minutes, compared with 113 minutes in the CVVR group. After 30 minutes of rewarming, the difference between the 2 groups with respect to core temperature was statistically significant (p = 0.002). A drop in core temperature after the initiation of rewarming, or after-drop, was noted in the control group animals, but not in the CVVR group. This difference was statistically significant after 15 minutes of rewarming (p = 0.015)

CONCLUSIONS

Venovenous rewarming utilizing the FMS 2000 fluid management system is more effective than is standard therapy alone for rewarming in the moderately hypothermic porcine model. This finding may prove clinically useful in the treatment of patients suffering from moderate hypothermia.

Hypothermia: a cold influence on trauma

Hypothermia is a life-threatening condition and can be a significant comorbid factor in a trauma patient. Certain social and medical characteristics can put a person at high risk for hypothermia, and special care must be provided to prevent and treat lower than normal body temperatures. In this article, a literature review was used to describe etiologies, assessment, treatment, and complications of hypothermia in the trauma patient.

Core rewarming via warm lavage liquid ventilation in a swine model of hypothermia-associated ventricular fibrillation

OBJECTIVES

To determine whether warm lavage liquid ventilation (LV) would provide rapid cardiopulmonary rewarming in swine with severe hypothermia and ventricular fibrillation.

METHODS

Intubated common swine (n = 3; mean +/- SEM weight 26+/-1.2 kg) were cooled to a mean aortic temperature of 26.4+/-0.9 degrees C. Ventricular fibrillation was induced by transthoracic electrical shock. Rewarming was initiated by continuous endotracheal instillation of warm (44 degrees C) pre-oxygenated, perfluorocarbon liquid at 5 mL/kg/min. Endotracheal instillation of perfluorocarbon occurred while standard gas ventilation continued. Manual chest compressions were performed throughout the 30-minute rewarming process. Outcome measures were the absolute and relative rates of change of all temperatures.

RESULTS

After 30 minutes of warm lavage LV, the mean aortic and pulmonary artery temperatures increased by 6.6+/-0.6 degrees C, respectively. Esophageal, nasal, and rectal temperatures did not change significantly. In one animal, normal sinus rhythm spontaneously returned after 16 minutes of rewarming.

CONCLUSIONS

During cardiac arrest, warm lavage liquid ventilation may produce rapid cardiopulmonary rewarming.

Regulation of coagulation abnormalities and temperature in organ donors

The 3 most common reasons for abnormal coagulation of blood in organ donors result from prior medications, consumption or dilution of coagulation factors and platelets during massive transfusion, and disseminated intravascular coagulation. Evaluation and treatment of these conditions are reviewed, and recommendations are provided for ordering appropriate laboratory tests and blood bank products.

Intravenous administration of levothyroxine for treatment of suspected myxedema coma complicated by severe hypothermia in a dog

A 7-year-old male English Coonhound with suspected myxedema coma complicated by severe hypothermia and metabolic abnormalities was treated with a combination of active external and core rewarming techniques, i.v. and oral administration of levothyroxine, supplemental oxygen, and administration of fluids (0.9% NaCl solution). Myxedema coma develops as a consequence of severe hypothyroidism and is characterized by a hypometabolic, stuporous state. Myxedema coma is associated with a high mortality rate, and most reported cases have involved Doberman Pinschers. Intravenous administration of levothyroxine can be used successfully in combination with oral administration to restore normal metabolic function and assist in warming and thermoregulation, although dosages should be conservative to avoid adverse cardiovascular effects.