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 survivor of 12 episodes

Accidental hypothermia is defined as an environmentally induced reduction of the core body temperature to 35 degrees C or below, where there is no primary endocrine or preoptic anterior hypothalmic dysfunction. We report a survivor of 12 episodes of accidental hypothermia. A comparison of his rewarming rates with passive external versus active core rewarming by inhalation of heated humidified oxygen via nasotracheal tube is provided. Multiple predisposing factors contributed to the repeated episodes of hypothermia. Anatomic causes of repeated nonaccidental hypothermia were excluded.     

Rewarming from immersion hypothermia: a comparison of three techniques

Rewarming from immersion hypothermia has been assessed in sheep by the use of three techniques — hot bath, body insulation and airway warming. Though the hot bath was the fastest of the methods of rewarming studied, consideration of temperature gradients and therefore total body heat diminished its advantage in comparison with central body rewarming via the airway (CBRW), which in turn showed considerably advantage over body insulation alone. CBRW did not have any thermal advantage gained on assisting the ventilation as compared with spontaneous breathing. The results illustrate the importance of adequate insulation of the body to prevent further heat loss and this was found to be true whether or not airway warming was being used. The site of heat uptake with CBRW was determined and observations were made on the physical behaviour of temperature gradients.     

重度烧伤术后低体温患者复温方案的制订及实践

目的 总结重度烧伤患者术后低体温的管理经验。 方法 组建多学科管理团队,基于循证医学制订重度烧伤患者术后低体温管理方案,包括建立复温单元、明确复温启动和终止标准、核心温度监测方法及监测频率、适合烧伤患者的复合复温措施、复温仪器的维护管理、护士复温技能的培训考核等。 结果 重度烧伤患者低体温持续时间由（274.38±149.43） min缩短至（107.89±65.39） min,复合复温方案执行率由21.88%提高至83.33%,核心体温监测正确率由18.75%提高至97.22%。 结论 重度烧伤术后低体温患者复温方案有利于提高护理质量。     

Forced air surface rewarming in patients with severe accidental hypothermia.

Methods of rewarming patients with severe accidental hypothermia remain controversial. This paper reports our experience with the use of forced air rewarming in patients with severe accidental hypothermia and a body core temperature below 30 degrees C. Fifteen hypothermic patients (body core temperature 24-30 degrees C) were successfully treated with forced air rewarming to a body core temperature above 35 degrees C (mean rewarming rate 1.7 degrees C/h, range from 0.7 to 3.4 degrees C/h). An afterdrop phenomenon was not observed in any of the patients. Nine hypothermic patients (group 1) had no prehospital cardiac arrest, all nine were long-term survivors and made a full recovery. Six patients (group 2) had prehospital cardio circulatory arrest with restoration of spontaneous circulation. None of the group 2 patients survived long-term. Group 1 and group 2 patients did not differ in core temperature (26.6+/-1.6 degrees C group 1 and 27.0+/-1.8 degrees C group 2). Group 2 patients needed catecholamine support during rewarming more frequently (83 versus 22%) and had higher lactate levels and lower pH values at all points of observation. In conclusion our preliminary data indicate that forced air rewarming is an efficient and safe method of managing patients with severe accidental hypothermia. The poor outcome of patients with a history of prehospital cardiopulmonary resuscitation is probably due to irreversible ischaemic brain damage in primarily asphyxiated avalanche and near-drowning victims, rather than the consequence of the rewarming method used.     

Hypothermia. Saving patients from the big chill.

Although hypothermia is a serious and sometimes fatal condition, prompt recognition and institution of appropriate rewarming techniques may save even profoundly affected persons. The diagnosis of hypothermia should be considered when patients present with alterations of cerebral function without apparent explanation, especially in the presence of underlying predisposing illnesses and conditions. When hypothermia is suspected, an accurate core temperature must be obtained. Application of rewarming techniques appropriate to the degree of hypothermia may be lifesaving. Conservative use of pharmacotherapy is warranted.     

Avoiding caesarean section in maternal hypothermia associated with marked fetal distress

A 37-weeks pregnant woman was admitted to the accident and emergency department with hypothermia following possible drug misuse. Although her pulse and blood pressure were normal, her fetus was found to have marked bradycardia. This caused anxiety and quick transfer of the unconscious and still hypothermic woman to the maternity unit. The baby was, however, not immediately delivered by caesarean section. Instead, rewarming of the mother was undertaken, which produced a rise in fetal heart rate as the maternal temperature rose. A healthy baby was eventually born after spontaneous labour. This report discusses the effects of hypothermia on the body and fetus. It also discusses the rationale for delaying delivery of baby until hypothermia is corrected.     

Thoracic lavage in accidental hypothermia with cardiac arrest--report of a case and review of the literature

BACKGROUND: Accidental hypothermia resulting in cardiac arrest poses numerous therapeutic challenges. Cardiopulmonary bypass (CPB) should be used if feasible since it optimally provides both central rewarming and circulatory support. However, this modality may not be available or is contraindicated in certain cases. Thoracic lavage (TL) provides satisfactory heat transfer and may be performed by a variety of physicians. This paper presents the physiological rationale, technique, and role for TL in accidental hypothermia with cardiac arrest. METHODS: A patient with hypothermic cardiac arrest, treated by the author using TL, serves as the basis for this report. A search of the English language literature using PubMed (National Library of Medicine, Bethesda, Maryland) was conducted from 1966 to 2003 and 13 additional patients were identified. Demographic information, lavage method, rewarming rate, complications, and neurological outcome were analysed. RESULTS: There were numerous causes for hypothermia, with drug and alcohol intoxication being the most common (n = 4; 28.6%). Patient age ranged from 8 to 72 years (median = 36 years). Mean core temperature was 24.5+/-0.60 degrees C. Most patients were without blood pressure or pulse upon presentation to the Emergency Department and the predominant cardiac rhythm was ventricular fibrillation (VF) (n = 9; 64.3%). Thoracic lavage was accomplished by thoracotomy in seven patients and tube thoracotomy in the remaining seven. Median rewarming rate was 2.95 degrees C/h. Median time until sinus rhythm was restored was 120 min. Median length of hospital stay was 2 weeks. Four (28.6%) patients died. Complications were seen in 12 (85.7%) patients. Among survivors, neurological outcome was normal in 8 (80%) while two were left with residual impairments. CONCLUSIONS: Patients presenting in cardiac arrest from accidental hypothermia may be rewarmed effectively using TL. Among survivors, normal neurological recovery is seen. Thoracic lavage should be strongly considered for these patients if CPB is not available or contraindicated.     

温度干预护理对全麻术后低体温患者的影响

目的探讨全麻恢复期低体温的护理措施，以避免低体温导致的不良反应。方法选择54例择期腹部手术后发生低体温的患者，随机分为对照组和试验组，每组27例。分别监测术前和人麻醉复苏室（PACU）时的体温，记录患者在PACU的复温时间和停留时间。结果温度干预护理后低体温患者复温时间和在PACU停留时间明显缩短。结论加强对PACU患者的体温护理，可缩短患者在PACU的复温时间、停留时间，减少低体温造成的并发症，减轻患者的经济负担。     

Diagnosis and treatment of hypothermia

Although hypothermia is most common in patients who are exposed to a cold environment, it can develop secondary to toxin exposure, metabolic derangements, infections, and dysfunction of the central nervous and endocrine systems. The clinical presentation of hypothermia includes a spectrum of symptoms and is grouped into the following three categories: mild, moderate, and severe. Management depends on the degree of hypothermia present. Treatment modalities range from noninvasive, passive external warming techniques (e.g., removal of cold, wet clothing; movement to a warm environment) to active external rewarming (e.g., insulation with warm blankets) to active core rewarming (e.g., warmed intravenous fluid infusions, heated humidified oxygen, body cavity lavage, and extracorporeal blood warming). Mild to moderate hypothermia is treated easily with supportive care in most clinical settings and has good patient outcomes. The treatment of severe hypothermia is more complex, and outcomes depend heavily on clinical resources. Prevention and recognition of atypical presentations are essential to reducing the rates of morbidity and mortality associated with this condition.     

Accidental hypothermia.

Individuals at extremes of age and those who have certain underlying medical conditions are at greatest risk for hypothermia. Hypothermia may occur during any season of the year and in any climate. Prompt recognition of hypothermia and early institution of the rewarming techniques are imperative for a successful outcome with minimal complications. Several rewarming techniques are available and the decision to use any of them depends on the degree of hypothermia, the condition of the patient, and the rewarming rate possible with the technique chosen.     

Severe accidental hypothermia with or without hemodynamic instability: rewarming without the use of extracorporeal circulation

BACKGROUND: The optimal rewarming technique for patients in deep accidental hypothermia with core temperatures below 28 degrees C is not established. Several authors believe that extracorporeal rewarming is essential, especially for patients with hemodynamic instability. Others believe that invasive rewarming ought to be reserved for patients in cardiac arrest. We describe our experience with a strictly conservative technique without the use of invasive rewarming devices in patients with severe accidental hypothermia and a sustained perfusion rhythm. METHODS: A cohort study extending from 1991 to 2000, including all patients received at the emergency department of the University Hospital of Vienna with severe hypothermia, a core temperature of maximum 28 degrees C and no preclinical cardiac arrest. RESULTS: 36 patients with deep hypothermia were included in the study. Their core temperatures ranged from 20.2 degrees C to 28 degrees C; the median temperature was 25.75 degrees C (25th and 75th percentile, 24.2/27.3). Fourteen patients were intoxicated and their multimorbidity was high. All of 19 patients with stable hemodynamics and 14 of 17 patients with unstable hemodynamics were successfully rewarmed to normothermia with warmed infusions, inhalation rewarming and forced air rewarming. The rewarming process took 9.5 hours (8/10.5) and required a volume load of 4820 ml (2735/5770). The rewarming rate was 1.09 degrees C per hour (0.94/1.25). Although 92% of the patients were successfully rewarmed to normothermia, in-hospital mortality was 42%, but was largely related to comorbidity. DISCUSSION: A conservative approach is highly successful in achieving normothermia in patients with deep hypothermia with or without stable hemodynamics. In-hospital mortality of severe accidental hypothermia in urban conditions is high; comorbidity might play a major role. The influence of the rewarming strategy on late in-hospital mortality remains unclear.     

Hypothermia. Cold-water drowning

Cold-water submersion results in rapidly induced hypothermia. The body's physiologic response to this insult is, in some ways, similar to that of controlled hypothermia employed in the hospital setting, with the time sequencing being greatly enhanced. The application of hypothermic techniques employed with extracorporeal heat exchange on cardiopulmonary bypass to those of cold-water submersion requires careful differentiation, especially during rewarming phases. Conversely, protecting the brain from hypoxic injury (and thus a favorable neurologic recovery) following cold-water submersion can be favorably modified by the co-existence of hypothermia. The protective effects of safe usage of hypothermic without neurologic damage is multifaceted and influenced by age, time, temperature and intracellular pH, metabolic rate, biochemical changes, high-energy storage depots, as well as institution of rewarming techniques. Criteria for brain death established by the President's commission does not apply to the hypothermic patient. According to colleagues, rewarming to between 30 and 34 degrees C is essential before discontinuing resuscitative measures because of the multifactoral influences that the hypothermic state entails. A child who appears asystolic, apneic, and with absence of central nervous system activity after cold-water submersion, requiring intensive resuscitative efforts, may have a favorable outcome. This does not absolutely suggest a devastating outcome as we have seen in those children "frozen alive," who are hypothermic but have been effectively resuscitated, rehabilitated, and allowed to return to normal life activities. Although combined intensive and rehabilitative efforts of the medical team are essential in the care of these children, foremost in our minds should be prevention of these accidents.     

胸腹部手术后低体温患者的护理

目的 对手术后发生低体温患者采取及时正确的复温,避免低体温可能产生的并发症。方法 对82例手术后低体温病人采取定时、正确的测量体温,经常触摸病人四肢皮肤和远端小动脉搏动,覆盖电热毯,加温静脉输液,调节室温等,使其在3～5h内恢复正常体温。结果 采取复温措施患者体温与低温时体温比较.经t检验,有显著性差异(t=30.08,P<0.01)。结论较大手术后病人易发生低体温且常被忽视,而影响手术效果,及时正确的复温能减少术后并发症,确保手术疗效。     

Full neurological recovery from profound (18.0 degrees C) acute accidental hypothermia: successful resuscitation using active invasive rewarming techniques

The case of a 17-year-old girl brought into the emergency department (ED) having been found in a field semi-clad and overtly hypothermic is reported. A weak carotid pulse, agonal breathing and fixed dilated pupils were noted. On arrival in the ED she was in asystolic cardiopulmonary arrest. Initial core body temperature was 18 degrees C. After 4 h of closed cardiopulmonary resuscitation and rewarming using a haemofiltration circuit, she made a full recovery with no adverse neurological sequelae. In this case report, the importance of prolonged resuscitation in cardiopulmonary arrest secondary to acute severe environmental hypothermia and the successful use of a haemofiltration circuit to deliver active core rewarming are highlighted.     

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.

The evaluation and management of accidental hypothermia

Accidental hypothermia is defined as an unintentional decrease in core body temperature to below 35 degrees C. Hypothermia causes hundreds of deaths in the United States annually. Victims of accidental hypothermia present year-round and in all climates with a potentially confusing array of signs and symptoms, but increasing severity of hypothermia produces a predictable pattern of systemic organ dysfunction and associated clinical manifestations. The management of hypothermic patients differs in several important respects from that of euthermic patients, so advance knowledge about hypothermia is prerequisite to optimal management. The paucity of randomized clinical trials with hypothermic patients precludes creation of evidence-based treatment guidelines, but a clinically sound management strategy, tailored to individual patient characteristics and institutional expertise and resources, can nonetheless be gleaned from the literature. This article reviews the epidemiology, pathophysiology, clinical presentation, and treatment of accidental hypothermia. Initial evaluation and stabilization, selection of a rewarming strategy, and criteria for withholding or withdrawing support are discussed.     

Rapid rewarming after mild hypothermia accentuates the inflammatory response after acute volume controlled haemorrhage in spontaneously breathing rats

Accidental hypothermia is a common companion of trauma/haemorrhage, and several clinical studies have identified reduced body temperature as an independent risk predisposing to increased morbidity and mortality. Accordingly, the majority of trauma care guidelines prescribe early and aggressive rewarming of hypothermic patients. Enzyme reactions are generally downregulated at temperatures below 37 degrees C, including most of those responsible for the inflammatory response. The rationale for adhering to these recommendations uncritically may therefore be questioned. In a rat model of mild hypothermia and haemorrhagic shock we wanted to compare the influence of rapid rewarming with persistently reduced temperature on the synthesis of early inflammatory mediators and organ function. Thirty-four male albino Sprague-Dawley rats were studied. Withdrawal of 2.5 ml blood/100 g body weight was performed over 10 min, with simultaneous reduction of body temperature to 32.5-33.5 degrees C. Seventy-five minutes after initiation of bleeding, two-thirds of the shed blood was retransfused. One group (n=17) was rewarmed to normothermia, the other (n=17) was kept hypothermic. The study was terminated after an observation period of 2 h. At the end of the study the rewarmed animals had a significantly lower mean arterial pressure, higher heart rate, higher synthesis of reactive oxygen species from peritoneal phagocytes, increased circulating levels of nitric oxide, and higher values of the organ markers aspartate aminotransferase and urea. The pro-inflammatory cytokines TNF-alpha and IL-6, the anti-inflammatory cytokine IL-10, the organ markers alanine aminotransferase, alpha-glutathione S-transferase and creatinine, as well as organ injury scores were equal in both groups. Three rewarmed rats died prematurely, versus one hypothermic animal. In conclusion, the results suggest that during the early stages after haemorrhagic shock, rapid rewarming from mild hypothermia may have unfavourable effects both on basic haemodynamic variables, and on the internal inflammatory environment of cells and tissues.     

Successful treatment of severe accidental hypothermia with cardiac arrest for a long time using cardiopulmonary bypass - report of a case

ABSTRACT: Accidental hypothermia is defined as an unintentional decrease in body temperature to below 35°C, and cases in which temperatures drop below 28°C are considered severe and have a high mortality rate. This study presents the case of a 57-year-old man discovered drifting at sea who was admitted to our hospital suffering from cardiac arrest. Upon admittance, an electrocardiogram indicated asystole, and the patient's temperature was 22°C. Thirty minutes of standard CPR and external rewarming were ineffective in raising his temperature. However, although he had been in cardiac arrest for nearly 2 h, it was decided to continue resuscitation, and a cardiopulmonary bypass (CPB) was initiated. CPB was successful in gradually rewarming the patient and restoring spontaneous circulation. After approximately 1 month of rehabilitation, the patient was subsequently discharged, displaying no neurological deficits. The successful recovery in this case suggests that CPB can be considered a useful way to treat severe hypothermia, particularly in those suffering from cardiac arrest.     

Rôle de l’équipe paramédicale dans la réalisation du contrôle ciblé de la température après un arrêt cardiaque récupéré

Therapeutic hypothermia, also called targeted temperature management, is increasingly used in the intensive care unit (ICU), based on its assessed neuroprotective effects against ischemia-reperfusion-induced brain damage. Targeted temperature management is indicated in comatose adult patients after cardiac arrest if successfully resuscitated from a witnessed out-of-hospital cardiac arrest of presumed cardiac cause with an initial rhythm of ventricular fibrillation or non-perfusing ventricular tachycardia and in a stable hemodynamic condition. Patients after in-hospital cardiac arrest or with other initial rhythms may also benefit. When indicated, therapeutic hypothermia should be quickly performed and tightly controlled. Both surface and core cooling methods target a body temperature of 32 to 34 °C. Thus, it is mandatory to know how to simply manage the routinely available techniques in order to perform hypopthermia as soon as possible, being aware of all side-effects that may alter the expected benefits. Therefore, implementing hypothermia in the ICU involve the whole medical and paramedical staff.