Hypothermia

Chapter 67 Hypothermia



Howard M. Corneli, MD



1 Why are children more prone to hypothermia than adults?




image Children have larger body surface–to–mass ratios.


image They may have less insulation, faster metabolism, and smaller energy reserves.


image They may be more at risk for medical illness, trauma, or environmental exposure.



2 Does hypothermia require severe cold exposure?


No. Unfortunately, clinicians may suspect hypothermia only when severe environmental exposure is evident. Any immersion in warm or cold water, or any major illness or trauma, may precipitate hypothermia. It is also seen in conditions as diverse as sepsis, hypoglycemia, drug ingestion, and child abuse, any of which may be occult.


Children are more at risk than adults for iatrogenic hypothermia due to rescue, transport, and resuscitation.



3 Why is hypothermia overlooked in pediatric patients in the emergency department (ED)?


Hypothermia victims only appear cold in the mild range of hypothermia. In deeper hypothermia, signs such as shivering, pallor, cyanosis, and agitation are replaced by flushing, edema, muscular rigidity, and decreased mental status. Standard clinical thermometers only measure down to 94° F (34° C).



4 What are some risk factors for hypothermia?
































Trauma Rescue
Severe illness Transport
Immersion or submersion Resuscitation
Exposure to wind or cold air Intoxication, especially with:
Central nervous system illness or injury   Alcohol
Hypothalamic dysfunction   Barbiturates
Endocrine impairment   Phenothiazines
Metabolic impairment Burns and weeping dermatoses
Iatrogenic causes Child abuse (e.g., cold water baths)


5 What clinical clues should prompt measurement of core temperature?




image Any of the above risk factors (including, but not limited to, any critical care patient)


image Decreased mental status, respiration, or circulation without other obvious cause


image A J (Osborne) wave on electrocardiogram (Fig. 67-1) is diagnostic when present, but is seen in only about 10–80% of cases in various series.


image

Figure 67-1 EKG showing Osborne or J wave.


Nolan J, Soar J: Images in resuscitation: The ECG in hypothermia. Resuscitation 64:133, 2005.



6 How should temperatures be taken to detect hypothermia?


A low-reading thermometer must be used. Oral and axillary temperatures are unreliable. Rectal temperatures are subject to damping, artifact, and time lags up to 1 hour. If used, rectal temperatures must be taken deep in the rectum for at least several minutes. The reliability of tympanic temperatures in the setting of significant hypothermia has not been established. Temperature probes in the bladder, esophagus, or nasopharynx are typically used to provide core temperatures of the trunk.


Danzl DF, Pozos RS: Accidental hypothermia. N Engl J Med 331:1756, 1994.



7 Define mild, moderate, and severe hypothermia




image Mild hypothermia: Temperature ranges from approximately 32° to 35° C. In this range, the body attempts to combat heat loss by shivering, increasing metabolism and vasoconstriction.


image Moderate hypothermia: Temperature spans the range from 28° to 32° C. In this range, compensatory mechanisms begin to fail, and mental status may be altered.


image Severe hypothermia: Temperature (< 28° C) leads to failed thermoregulation, metabolic shutdown, and paradoxical vasodilatation accompanied by hypovolemia, decreased perfusion, and stupor or coma.


Corneli HM: Hot topics in cold medicine: Controversies in accidental hypothermia. Clin Pediatr Emerg Med 2:179–191, 2001.



8 Describe some landmarks for converting between Celsius and Fahrenheit


At the upper end of the hypothermic range, 35° C equals 95° F. The threshold of severe hypothermia, 28° C, can be inverted to yield 82° F. Starting with these landmarks, an approximate 2:1 ratio between degrees Fahrenheit and degrees Celsius gives workable conversions. For example, 30° C, an increase of 2° from 28° C, is equivalent to 86° F, an increase of 4° from 82° F.

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Sep 1, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Hypothermia

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