REVIEWHypothermia in the trauma patient
Introduction
Hypothermia in humans is defined as a core temperature below 35 °C,4., 37. and has traditionally been classified into zones of severity based on the physiologic changes that occur with decreasing body temperature.12 Mild hypothermia, with core temperatures between 32–35 °C, is usually well tolerated, with compensatory cardiovascular changes designed to maintain temperature homeostasis. Below 32 °C, however, cardiac conduction disturbances become apparent, and at 28 °C serious dysrhythmias can occur. Below 28 °C heat production mechanisms begin to fail, and at 20 °C virtually all patients are asystolic.
These original definitions were introduced to describe hypothermia resulting from environmental exposures. In a multicenter study of over 400 cases of hypothermia due to exposure, core temperature less than 32 °C was associated with 21% mortality.6 In trauma patients, however, the presence of hypothermia was associated with a much higher mortality than patients who had suffered exposure. Jurkovich found that in 71 adult trauma victims, core temperature less than 32 °C was associated with 100% mortality, independent of the presence of shock, injury severity score, or volume of fluid resuscitation.30 Because the prognosis associated with hypothermia in the trauma victim is so poor, a separate classification of hypothermia has been developed for use in the injured patient (Table 1). As such, hypothermia in the trauma patient is classified as mild (36–34 °C), moderate (34–32 °C), or severe (below 32 °C).15
Section snippets
Physiologic effects of hypothermia
Regulation of body temperature occurs in the hypothalamus, which receives input from thermoreceptors along the distribution of the internal carotid artery, the posterior hypothalamus, and peripheral skin receptors.35 Homeothermic responses to cold include increased muscle tone and shivering, as well as metabolic increases from release of catecholamines and thyroxine.
Hypothermia can have marked physiologic effects on the cardiac, pulmonary, neurologic, and haemostatic systems (Table 2). In
Causes of hypothermia in the trauma patient
From the time of injury, trauma itself alters the normal central thermoregulation and blocks the shivering response. The thermoneutral zone is defined as the ambient temperature at which basal thermogenesis offsets continuing heat losses, and in humans, occurs at 28 °C.12 Maintaining euthermia when ambient temperatures are below the thermoneutral zone requires increased heat production and oxygen consumption. When tissue oxygen consumption is limited by shock, insufficient heat production occurs
Management of hypothermia
The first step in correcting hypothermia is the determination of core temperature. Unfortunately, studies have indicated that temperature is not often measured in the trauma patient, especially those who are severely injured.44 While oral and rectal temperatures are most commonly employed in the emergent setting, oesophageal and bladder temperatures have been shown to correlate more closely with core temperatures.35 A more recent development is the use of infrared tympanic membrane thermometry,
Hypothermia in the operating room
Hypothermia in the injured patient has marked clinical implications. Trauma patients with a core temperature of less than 32 °C were noted to have 100% mortality,30 compared to a 23% mortality for patients with the same temperature from exposure related hypothermia.6 Although many of these deaths are attributed to underlying conditions or associated diseases, several studies have demonstrated a significantly higher mortality among trauma victims with hypothermia. These studies have shown that
Ongoing research and controversies
Despite the physiologic changes induced by hypothermia and the potential for complications in the trauma patient, hypothermia has been noted historically to improve outcomes in certain clinical situations. Induced hypothermia is routinely employed during organ transplantation, cardiac surgery, and neurologic surgery, as it limits tissue ischaemia by decreasing overall metabolic activity and cellular oxygen consumption. As such, some authors have proposed that hypothermia may provide a
Summary
Hypothermia is a common finding in the trauma patient, and contributes to increased morbidity and mortality in this group of critically ill patients. Although initial temperatures may be normal, decreases in core temperatures during the course of initial evaluation and resuscitation are common. Hypothermia contributes to alterations in physiologic functions, and through alterations of the normal coagulation function, can contribute to further haemorrhage and shock in the injured patient. Both
References (70)
- et al.
Traumatic hypothermia is related to hypotension, not resuscitation
Ann. Emerg. Med.
(1996) - et al.
Improved survival of hemorrhagic shock with oxygen and hypothermia in rats
Resuscitation
(1991) - et al.
Multicenter hypothermia survey
Ann. Emerg. Med.
(1987) - et al.
Hypothermia, coagulopathy, and acidosis
Surg. Clin. N. Am.
(2000) - et al.
Hypothermia and acidosis worsen coagulopathy in the patient requiring massive transfusion
Am. J. Surg.
(1990) Advances in the management of hypothermia
Surg. Clin. N. Am.
(1995)- et al.
Induced hypothermia and rewarming after hemorrhagic shock
J. Surg. Res.
(2002) - et al.
The effect of different degrees of hypothermia on myocardium in treatment of hemorrhagic shock
J. Surg. Res.
(1990) - et al.
Hypothermia in trauma patients
J. Am. Coll. Surg.
(1999) - et al.
Extracorporeal cardiopulmonary life support with heparin-bonded circuitry in the resuscitation of massively injured trauma patients
Am. J. Surg.
(1995)
Adverse effects of hypothermia in postoperative patients
Am. J. Surg.
Forced air speeds rewarming in accidental hypothermia
Ann. Emerg. Med.
Cold water submersion and cardiac arrest in treatment of severe hypothermia with cardiopulmonary bypass
Resuscitation
Thrombolysis with tissue plasminogen activator (tPA) is temperature dependent
Thromb. Res.
Suppression of shivering decreases oxygen consumption and improves hemodynamic stability during postoperative rewarming
Ann. Thorac. Surg.
Factors influencing arterial PO2 during recovery from anaesthesia
Br. J. Anaesth.
The effects of hypothermia and injury severity on blood loss during trauma laparotomy
J. Trauma
Predicting life-threatening coagulopathy in the massively transfused trauma patient: hypothermia and acidosis revisited
J. Trauma
Comparison of ear-based, bladder, oral and axillary methods for core temperature measurements
Crit. Care Med.
Abdominal gunshot wounds. An urban trauma center’s experience with 300 consecutive patients
Ann. Surg.
Very hot intravenous fluid in the treatment of hypothermia
Am. J. Surg.
Continuous arteriovenous rewarming: rapid reversal of hypothermia in critically ill patients
J. Trauma
Continuous arteriovenous rewarming: experimental results and thermodynamic model simulation of treatment for hypothermia
J. Trauma
Continuous arteriovenous rewarming; report of a new technique for treating hypothermia
J. Trauma
Comparison of three methods of rewarming from hypothermia: advantages of extracorporeal blood warming
J. Trauma
Extracorporeal venovenous recirculation for the treatment of hypothermia during elective aortic surgery: a phase I study
Surgery
Incidence and timing of hypothermia in trauma patients undergoing operations
J. Trauma
The impact of hypothermia on dilutional coagulopathy
J. Trauma
Hypothermia and severe trauma
Aust. N. Z. J. Surg.
Comparison of tympanic, esophageal and blood temperatures during mild hypothermic cardiopulmonary bypass: a study using an infrared emission detection tympanic thermometer
J. Clin. Monit.
A review of the literature concerning resuscitation from hypothermia. Part I. The problem and general approaches
Aviat. Space Environ. Med.
The role of hypothermia in the management of severe brain injury: a meta-analysis
Arch. Neurol.
Mild intraoperative hypothermia increases duration of action and spontaneous recovery of vecuronium blockade during nitrous oxide-isoflurane anesthesia in humans
Anesthesiology
Cited by (172)
Prehospital Active and Passive Warming in Trauma Patients
2023, Air Medical JournalMassive Hemorrhage Protocol: A Practical Approach to the Bleeding Trauma Patient
2023, Emergency Medicine Clinics of North AmericaAn analysis of the incidence of hypothermia in casualties presenting to emergency departments in Iraq and Afghanistan
2020, American Journal of Emergency MedicineCitation Excerpt :Hemostasis functions under well-regulated parameters. Deviations outside acceptable temperature ranges results in systemic dysfunction. [2] During hemorrhage, anaerobic metabolism leads to a buildup of lactic acid. [7]
Hypothermia-rewarming: A Double-edged sword?
2019, Medical Hypotheses