Cardiac arrest in hyperthermia and malignant hyperthermia
Hyperthermia and malignant hyperthermia
Hyperthermia is characterized by a body temperature exceeding the typical range of 36.5-37.6°C (97.7-99.7°F). It arises when heat production or acquisition surpasses the body’s capacity for heat elimination.
Hyperthermia can induce an inflammatory state similar to the Systemic Inflammatory Response Syndrome (SIRS). Body temperatures surpassing 40°C (104°F) are potentially hazardous and may precipitate cardiac arrest. The classification of hyperthermia is delineated in Table 1 below.
| Severity | Clinical presentation | Treatment |
|---|---|---|
| Mild hyperthermia | Thirst. Weakness. | Cold environment. Passive cooling. Cold oral fluids. |
| Heat syncope | Discomfort, anxiety, dizziness, syncope. | Cold environment. Cold intravenous fluids (1-2 L crystalloid, with rate 500 ml/h). Cold shower. Ice packs. |
| Heat stroke (>40°C) | Neurological symptoms, confusion, convulsion, tachycardia, hypotension, coma. | As above but with lower temperatures. Electrolyte replacement. Large infusions of fluids are typically needed. |
Body temperature should decrease at a rate of 0.1°C/min during the cooling process.
Malignant hyperthermia
Malignant hyperthermia may manifest under two primary circumstances:
- Due to a genetic mutation in the RYR1 receptor, resulting in persistent muscle contraction upon administration of halogenated anesthetic agents.
- As an idiosyncratic response to substances such as MDMA (ecstasy) or amphetamines.
In either scenario, there is sustained muscle activation, leading to marked heat generation, acidosis, and the subsequent development of hyperkalemia. This condition is potentially fatal and necessitates prompt intervention, including sedation and the administration of Dantrolene.
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