Etiology and Stages of Heat Stroke
Heat stroke is an extremely severe and rapidly progressing form of hyperthermia. The primary etiological factor is exposure to high-intensity external heat. The risk of developing this pathology increases manifold when natural adaptation mechanisms to elevated temperatures are inefficient.
The pathogenesis is characterized by rapid progression:
- Intensive overheating of the organism begins.
- A brief compensation phase is initiated. This phase often proceeds so rapidly that it has no clinical manifestations.
- A rapid and sharp failure of thermoregulatory mechanisms occurs.
- Transition into the decompensation phase. During this period, the rectal body temperature can reach life-threatening values of 42–43 °C in a very short time.
Heat stroke is fundamentally defined by this brief adaptation instantly giving way to profound decompensation.
Intoxication Factors and Systemic Complications
Excessive elevation of body temperature triggers a massive cascade of biochemical disorders, leading to severe endotoxemia. Three groups of toxic substances accumulate in the blood:
- Excess proteolysis products: ammonia, ammonia derivatives, and various peptides.
- Abnormal lipid metabolism products: epoxides, ketone bodies, lipid peroxides, and aldehydes.
- Medium-sized molecules (MSMs): polyamines, oligosaccharides, glycoproteins, and oligopeptides.
This progressive intoxication exacerbates systemic dysfunction. It causes erythrocyte hemolysis and a significant increase in microvessel wall permeability.
Simultaneously, severe hemostatic consequences develop: blood viscosity increases, systemic hypercoagulation occurs, along with microthrombosis and disseminated intravascular coagulation (DIC syndrome). Microcirculation is severely disrupted.
Mortality from heat stroke reaches 30%. The main causes of death include acute intoxication, respiratory arrest, and heart failure resulting from cardiac fibrillation or asystole.
Sunstroke: Specifics of Nervous System Injury
Sunstroke is a typical form of severe hyperthermic condition with a high risk of mortality. Its primary cause lies in the direct action of solar energy on the brain. The infrared spectrum (thermal radiation) possesses the greatest pathogenic effect.
Unlike convection and conduction heat, infrared radiation can heat both superficial and deep tissues simultaneously. It intensively heats brain tissue, including the area housing the neurons of the thermoregulatory center, which accounts for the very rapid development of the pathology.
Pathogenesis consists of a combination of general hyperthermia and specific CNS injury:
- Direct neuronal damage: metabolism and plastic processes in brain cells are disrupted.
- Vascular and cerebrospinal fluid (CSF) dynamics shifts: arterial hyperemia increases, lymph production rises, and venous hyperemia progresses.
- Complications: brain edema and multiple hemorrhages into the brain parenchyma develop.
- Mechanical factor: vascular disturbances lead to brain compression.
- Secondary CNS damage: compression combined with disrupted metabolism causes severe ischemia, hypoxia, and damage to nerve centers.
The ultimate result is critical systemic failure and death.