Chapter 226: Hypothermic Patient Management

INTRODUCTION

The Centers for Disease Control and Prevention (CDC) reported 13,419 deaths from hypothermia in the United States between 2003 and 2013.¹ Approximately 67% of deaths were in males. Many think these figures underestimate the number of cases because standard thermometers do not measure low temperatures.^1,2 Hypothermia is defined as a core body temperature below 35°C.² The normal physiologic thermoregulatory responses fail below this level and lead to an inability to generate enough heat to maintain bodily functions.^3,4 Accidental hypothermia is further classified as primary or secondary.⁵ Primary accidental hypothermia occurs when a healthy individual’s heat production is overcome by environmental factors.^6-9 Secondary accidental hypothermia occurs when predisposing factors lead to disruption of temperature homeostasis and increase the individual’s susceptibility to lesser environmental stresses (e.g., drug intoxication, endocrine disorders, and trauma).³ Traumatic injury is a common example of an acquired condition associated with hypothermia.⁵

There are multiple reasons why trauma patients are at an increased risk for hypothermia.¹⁰ These include extended prehospital time, resuscitation with room temperature intravenous fluids, exposure to environmental factors, and physiologic characteristics of the trauma. Bleeding and hypoperfusion alter thermoregulation. Hypothermia is an independent risk factor for increased morbidity and mortality in trauma patients because of its association with coagulopathy and multiple organ failure.¹¹

Significant emphasis has been placed on the prevention of hypothermia as well as early recognition and correction of hypothermia in the prehospital setting. Hypothermia can progress after the patient arrives in the Emergency Department.¹² Many studies have demonstrated this phenomenon in traumatically injured patients.^13-15 This recognition has prompted development of multidisciplinary approaches to maintaining normothermia as the patient moves through the hospital.¹⁶ The importance of continuity and communication in dealing with hypothermia cannot be overstated.

There are many other groups at risk for hypothermia. Infants lack a shivering response and exhibit a larger surface-to-volume ratio leading to rapid heat loss.^17,18 Hypothermia is seen more frequently in southern states and during colder months.¹⁹ Malnourished or very thin individuals contain less insulating adipose tissue and less energy for metabolic heat generation.^18,20-22 Endocrine disorders (e.g., hypothyroidism, hypoglycemia, diabetes, and adrenal insufficiency) lower metabolic heat production.^17,20 Underlying infections, poverty, dementia, and conditions that impair peripheral vasoconstriction (e.g., burns and psoriasis) predispose to hypothermia. Drugs of abuse lead to diminished awareness of cold surroundings while others (e.g., opiates, clonidine, and tramadol) directly block the shivering mechanism.^20,22,23

Alcohol has been cited as the most common factor associated with hypothermia.¹⁸ Alcohol decreases shivering, causes hypoglycemia, and inhibits metabolic heat production.²⁴ Alcohol affects the hypothalamus. It changes the thermoregulatory set point and cold perception.^18,25,26 Peripheral vasodilation increases heat loss and perceived comfort at cold temperatures and diminishes the drive to find ...