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Chapter 19. Hypothermia/Hyperthermia and Rhabdomyolysis

Janice L Zimmerman, MD, FCCP
DOI: 10.1378/critcare.21.19
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Sections

Objectives 
  • Understand the physiologic responses associated with hypothermia.

  • Outline supportive measures and rewarming techniques for the management of hypothermia.

  • Describe predisposing factors for heat stroke, its clinical manifestations, and cooling methods.

  • Discuss the clinical presentations and management of malignant hyperthermia and neuroleptic malignant syndrome.

  • Describe the etiologies, clinical manifestations, and treatment of rhabdomyolysis.

Synopsis 

Hypothermia results from an increase in heat loss, decrease in heat production, or impaired thermoregulation. Moderate to severe hypothermia presents with multiorgan involvement with prominent cardiovascular manifestations. Rewarming techniques are chosen based on clinical manifestations and availability of resources. Passive external rewarming is used for all patients to prevent further heat loss. Active external rewarming and active core rewarming techniques are often combined and used for patients with moderate to severe hypothermia.

Heat stroke results from an increase in heat production or decrease in heat loss. Heat stroke is classified as classic (nonexertional) or exertional heat stroke. In addition to supportive care, cooling is accomplished with conductive or evaporative methods. Overaggressive hydration should be avoided in the elderly patients to avoid cardiac decompensation with cooling.

Malignant hyperthermia results from a genetic muscle defect triggered by exposure to anesthetic agents. The syndrome is characterized by hyperthermia, muscle contracture, and cardiovascular instability. Prompt recognition allows discontinuation of the precipitating agent and institution of dantrolene. Neuroleptic malignant syndrome is an idiosyncratic reaction, usually to neuroleptic drugs, that is characterized by hyperthermia, muscle rigidity, alterations in mental status, autonomic dysfunction, and rhabdomyolysis. Treatment is removal of the agent, use of dantrolene for muscle rigidity, dopamine agonists, and supportive care.

Rhabdomyolysis results from muscle injury caused by a wide variety of etiologies. The maintenance of intravascular volume and renal perfusion is the most important aspect of preventing renal failure. Electrolyte abnormalities, particularly hyperkalemia, should be anticipated and treated expeditiously.

References

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