Hypothermia

Hypothermia is a fall in core body temperature below approximately 35°C (95°F) — the lower boundary of the range a healthy body normally defends. The body generates heat through metabolism and loses it constantly to its surroundings; hypothermia occurs when those losses outpace production long enough that the thermoregulatory system cannot compensate.

It appears in two distinct roles on these pages. In animal pharmacology it is one of the four hallmarks of the cannabinoid tetrad, a standard protocol used to confirm CB1 activity in rodents. In human harm-reduction contexts it describes a real outcome when a substance blunts the perception of cold, impairs the shivering response, or creates a false sense of warmth while heat continues to escape.

How it works · its role

The hypothalamus acts as the body's thermostat, triggering shivering and vasoconstriction when core temperature begins to fall. As temperature drops below 35°C these defences weaken. Cognitive slowing and loss of coordination appear first, followed by confusion — which is dangerous because the person losing heat may not recognise the threat.

Below roughly 32°C shivering stops, a sign the body can no longer self-rescue. Cardiac rhythm becomes unstable at lower temperatures, and ventricular fibrillation becomes a serious risk at severe stages. Even deep hypothermia is survivable with prompt external rewarming, but the window for safe self-care narrows quickly once shivering ceases.

Relevance to substances & effects

Alcohol is the textbook example in this corpus. It dilates peripheral blood vessels, drawing warm blood toward the skin surface and producing a strong subjective sensation of warmth. In cold environments this markedly accelerates heat loss. The warmth feels genuine; the danger is not perceived. Intoxication further clouds judgment, reducing the likelihood that someone will seek shelter or notice the signs of cooling.

Cannabinoids reliably lower core temperature in rodents — one reason hypothermia was built into the tetrad as a marker of CB1 activity. How much this translates to clinically meaningful cooling in humans at typical doses, in normal indoor environments, remains less well characterised.

CNS depressants as a class — opioids, benzodiazepines, GHB — reduce metabolic heat production and can blunt or delay the shivering response. In a cold environment, or when layered with alcohol, these effects are additive.

Clinical · risk note

Warning signs follow a rough sequence: shivering and clumsiness first; then confusion, slurred speech, and growing sedation; finally, cessation of shivering as deeper cooling sets in. A person who has stopped shivering but remains cold to the touch is past the mild stage.

First response: move the person out of cold, remove wet clothing, and apply gentle external warmth — blankets, body heat, a warm (not hot) environment. Rough or sudden movement of a severely hypothermic person can precipitate cardiac arrhythmia. Moderate and severe stages are medical emergencies; call emergency services rather than attempting field management alone.