Heat Stroke and Sunstroke: Causes

Pathogenesis (development of disease)

Sunstroke results from prolonged direct sunlight on the unprotected head and neck, resulting in irritation of the meninges (brain membranes) and brain tissue, which can lead to an inflammatory response. Note: Heat illnesses (heat cramps, heat exhaustion, and heat stroke) can develop completely independently and seemingly abruptly, i.e., there is no particular sequence of specific stages of illness. Heat exhaustion (synonyms: heat faintness, heat syncope) is caused by heat vasovagal (“excessive vagotonus affecting the vessels). As a result of the heat, there is dilatation (widening) of the peripheral blood vessels. Heat cramps result from fluid and electrolyte losses (salt depletion of the body, especially sodium). Heat stroke is the most severe form of heat injury. Heat stroke can be the result of salopriver heat exhaustion (salt depletion) as well as hydropriver heat exhaustion (water depletion). There is an increase in heat production with a simultaneous decrease in heat dissipation. Heat stroke is an endogenous septic disease that can lead to multi-organ failure due to damage to the liver and lungs and central nervous system (CNS). Individuals with severe preexisting conditions such as diabetes mellitus or alcohol use are particularly at risk. Note: Heat stroke is usually preceded by heat exhaustion.

Etiology (causes)

Biographic causes

  • Age of life – older age*
  • Low fitness level* (see also overweight and exercise status under “Overweight”).
  • Social isolation (risk factor for the development of heat stroke).
  • Living in the attic (risk factor for developing heat stroke).

Behavioral causes

  • Nutrition
    • Insufficient fluid and electrolyte intake (electrolyte deficiency), i.e. insufficient compensation of sweat losses.
  • Consumption of stimulants
    • Alcohol* (alcohol consumption is considered a risk factor for heat illness regardless of physical exertion).
  • Drug use (can trigger hyperthermia).
    • 3,4-Methylenedioxypyrovalerone (MDPV, “bath salts“).
    • Amphetamines (indirect sympathomimetic).
    • Cocaine
    • “magic mushrooms” (psilocybin)
    • Methylenedioxyamphetamine (Ecstasy)
    • Phenylcyclohexylpiperidine (PCP, “angel dust”).
  • Physical activity
    • Sports
    • Severe physical exertion under high ambient temperature and insufficient hydration → exercise-induced hyperthermia
    • No heat acclimatization*
    • Dehydration*
  • Sleep deprivation*
  • Overweight (BMI ≥ 25; obesity)* ; heat incident for:
    • Trained overweight: almost 4 times higher risk.
    • Untrained overweight recruits: 8-fold increased risk.
  • No head covering (i.e. sun exposure to uncovered skull → thermal meningitis/ meningitis).
  • Thermal insulating clothing
  • Prolonged standing in hot environment → see below symptoms/heat syncope.

Disease-related causes (here: current health situation)* .

  • Diabetes mellitus
  • Febrile diseases
  • Cardiovascular disease (cardiovascular disease) (risk factor for developing heat stroke).
  • Viral infections

Medications that can negatively affect thermoregulation or provoke desiccosis (dehydration):

  • Α2-adrenoceptor agonists (α2-agonists for short).
  • Laxatives
  • Anticholinergics, antidepressants: increase heat production and thus increase body temperature, which leads to increased sweating and thus electrolyte losses!
  • Antihistamines
  • Benzodiazepines
  • Beta-blockers: reduction in cardiac output, which may impair heat adaptation.
  • Diuretics and ACE inhibitors/ angiotensin II receptor antagonists: dehydration and/or electrolyte imbalance due to hyponatremia.
  • Ephedrine-containing drugs
  • Calcium channel blockers (calcium antagonists, calcium antagonists).
  • Lithium
  • Neuroleptics, Selective Serotonin Reuptake Inhibitors (SSRIs): inhibition of central thermoregulation.
  • Mao inhibitor
  • Muscarinic receptor antagonists: decrease sweat secretion and thus risk of overheating.
  • Phenothiazines
  • Salicylates
  • Thyroid hormones
  • Sedation by dopaminergic and Parkinson’s drugs: lowering the perception of heat exhaustion or reducing the feeling of thirst and thus risk of exsiccosis.
  • Serotonin-releasing substances (SSRIs, tramadol, triptans).
  • Tricyclic antidepressants

Environmental pollution – intoxications

  • High ambient temperature*
    • Heat (heat day: > 30 °C; desert day: > 35 °C)Note: Above 37 degrees it can be critical for humans, especially if it is humid.
  • High humidity*
  • Lack of air movement*
  • Lack of shadow*

* Risk factors of exertion-induced heat stroke.