Training at Shaolin: Heat disorders.

Here is a fairly technical article concerning the pathophysiology of heat stroke, an uncommon but nevertheless, occasional concern when training in the summer heat of Shaolin Temple.

Heatstroke is defined as the combination of hyperthermia (core temperature >105°F [40.6°C]) and neurologic impairment. There are 2 types of heatstroke: classic nonexertional heatstroke (NEHS) and exertional heat stroke (EHS).[3] From 1979 to 1997, the National Centers for Health Statistics (NCHS) reported 7,046 deaths secondary to heat, or 371 deaths per year; this is presumed to underestimate the true numbers of deaths. Those older than age 65 years make up almost half of these cases. Heatstroke is seen less often in subtropical areas than in temperate climates. The 2003 heat wave in France is attributed for the deaths of more than 10,000 people.

The 80% mortality rate associated with heatstroke can be reduced to as low as 10% if heatstroke is recognized early and cooling treatment is initiated promptly. The damage caused by this condition is directly related to the temperature and the length of time it remains elevated. The classic presentation is that of hyperthermia, anhidrosis, and neurologic deficit. Some patients, however, will still sweat, and others will begin to cool en route to the hospital; these patients might not meet the classic temperature criteria.

Classic NEHS occurs most frequently in very young and very old individuals during heat waves. Also at risk for NEHS are alcoholics, the chronically or mentally ill, and those who are dehydrated. Patients present with high temperatures, lack of sweating, and altered mental status. Neurologic complaints may include irritability, lethargy, confusion, ataxia, seizures, and coma. Psychiatric-type symptoms, such as delusions or hallucinations, can also occur. The classic triad is not always present. Sweating may occur, and patients may present with temperatures <105.8°F (41°C). Additional symptoms and signs may include vomiting, diarrhea, tachycardia, hypotension, and tachypnea.

EHS typically occurs in healthy young patients participating in vigorous physical activity in hot environments,but it can occur at ambient temperatures as low as 70°F (21.1°C) as well. Those affected with EHS present with hyperthermia, altered mental status, and diaphoresis. They can exhibit strange behaviors or syncope during physical activity, as well as experience abdominal cramps, nausea, vomiting, diarrhea, headache, and dizziness. Because these patients retain their ability to sweat, their temperatures may drop after physical activity has stopped but before presentation at the hospital. Risk factors for EHS include viral infections, fatigue, dehydration, the use of stimulants, and not being acclimatized to higher temperatures.

In addition to elevated temperatures and neurologic signs and symptoms, other organ systems may also be affected in EHS, including the cardiovascular, pulmonary, gastrointestinal, hepatic, renal, and musculoskeletal systems. The stress caused to the cardiovascular system can be particularly worrisome in the elderly. Tachycardia at 130-140 bpm and greater is common, as is hypotension resulting from dehydration, redistribution of blood to the skin, and collapse of vascular tone. Patients can be tachypneic and hypoxic for various reasons, including atelectasis, noncardiogenic pulmonary edema, and aspiration. Liver and renal failure can pose serious risks to those surviving the neurologic insult. Rhabdomyolysis is common and, along with hypotension, often leads to renal failure. Liver failure also commonly occurs, possibly secondary to direct heat injury and hypoxia. Disseminated intravascular coagulation may also occur.

Multisystem damage is a result of the widespread deadly cellular effects of heat and the body's resultant inflammatory response. Multisystem injury leads to increased morbidity and mortality. In a retrospective study on heatstroke victims, Varghese et al found that the overall mortality rate was 70% for all cases, but it was 85% in patients with multiorgan failure. These investigators found that elevation of creatine kinase, elevation of liver transaminases, and metabolic acidosis were each predictors of poor patient prognosis.