New Delhi: The National Centre for Disease Control (NCDC) has said that the cause of death should be certified as heat stroke or hyperthermia where the measured antemortem body temperature at the time of collapse was more than or equal to 40.6 degrees Celsius. The ‘Autopsy Findings in Heat Related Deaths’, a set of guidelines released by the NCDC, defined heat-related death as a death in which exposure to high ambient temperature either caused the loss of life or significantly contributed to it.
Deaths may also be certified as heat stroke or hyperthermia with lower body temperatures when cooling has been attempted prior to arrival at the hospital and/or when there is a clinical history of mental status changes and elevated liver and muscle enzymes, the document stated in the section ‘Criteria to Label Heat Stroke or Heat-Related Death’.
It also said that in cases where the antemortem body temperature cannot be established but the environmental temperature at the time of collapse was high, an appropriate heat-related diagnosis should be listed as the cause of death or as a significant contributing condition.
“A significant number of these deaths will occur in persons having some preexisting disease known to be exacerbated by heat stress. These deaths can be certified as heat-related, with the disease being considered a significant contributing condition, or vice versa,” the criterion stated.
The NCDC document stated that recognition and confirmation of heat-related mortality has emerged as a challenge as different sectors use different case definitions, assessment mechanisms and linked response measures often leading to various estimates.
“This highlights the importance of understanding characteristics of exposure, physiological factors affecting heat strain, illnesses, and death and adaptation measures (behavioural, institutional) utilised,” the guidelines said.
Saying that autopsy findings are nonspecific, the document recommended that autopsy is not mandatory in all cases of heat-related illnesses.
The diagnosis of heat-related death is based principally on investigative information; autopsy findings are nonspecific. The decision to autopsy should be based on the circumstances of the death, the age of the deceased, and the available resources, it said.
The collection of blood, urine, and vitreous humor for toxicologic examination is highly desirable if the condition of the body allows it, the NCDC recommended, adding that when these specimens are collected and preserved, toxicologic analyses can be performed as resources become available.
The NCDC underlined that all pathologists and forensic pathologists to be aware of the criteria to label a death as heat-related/heat stroke. Necessary training and sensitisation are required for pathologists and forensic pathologists, it stated.
According to the document, rapid, severe decompression of the body’s heat dissipation mechanisms following short-term or sustained heat exposure leads to heat stroke.
Physiological responses to heat gain, through ambient heat exposure or exertion, also require the heart to pump harder and faster. For people with pre-existing heart conditions, this can lead to a mismatch between a high oxygen demand of the cardiac muscles and reduced oxygen supply.
If sustained, it can lead to cardiovascular collapse. Therefore, cardiovascular events are a primary pathway leading to high mortality among older adults. High existing burden of cardiovascular diseases in the population and elevated cardiovascular strain from heat stress, translates to cardiovascular mortality being the leading cause of death during extreme heat, the document said.
Heat-derived lung damage, such as pulmonary oedema and acute respiratory distress syndrome, combined with the high rates of people with pre-existing respiratory conditions, and increased pulmonary stress due to heat-related hyperventilation and elevated air pollution during heatwaves, is accountable for the second highest source of mortality and morbidity during heatwaves, following cardiovascular disease.
Exposure to extreme heat is also associated with acute kidney injury, adverse pregnancy outcomes, mental health impacts, and an increase in non-accidental and injury-related deaths, the NCDC document said.
