Hyperthermia

Original Editor - Neha Duhan Top Contributors - Neha Duhan, Uchechukwu Chukwuemeka, Claire Knott, Evelyne Bahire, Kim Jackson and Lucinda hampton

Introduction

Hyperthermia refers to a group of heat-related conditions characterized by an abnormally high body temperature. In lay terms it is "overheating". It is an abnormally high body temperature caused by a failure of the heat-regulating mechanisms of the body to deal with the heat coming from the environment.

• Hyperthermia is defined as a body temperature greater than 40°^C and consists of a spectrum of conditions that range from mild (heat oedema, heat rash) to life-threatening (heat stroke).
• Risk for these conditions can increase with the combination of outside temperature, general health and individual lifestyle.
• In humans, core body temperature ranges from 95.9°^F to 99.5°^F (35.5°^C to 37.5°^C) during the day.

See also Heat Illness in Sports

Levels of Heat Illness

Patient is being sprayed with cool water,1943.

Heat-related illnesses start out mildly uncomfortable and progress all the way to life-threatening. The conditions are, from least serious to most serious: heat oedema, heat rash, heat syncope, heat cramps, heat exhaustion and heatstroke.

1. Heat Oedema and Heat Rash: Heat oedema and heat rash are both the mildest sorts of heat illness. Heat oedema may occur as the body tries to dissipate heat by vasodilation and a shift of blood flow to the skin. This mostly happens in the lower extremities as fluid creates inflammation in the feet and ankles. Heat rash (also known as prickly heat or miliaria Rubra) is a pinpoint red rash that forms on the skin that was covered by clothing. This generally occurs in areas that have a higher concentration of heat glands, such as the trunk and groin, and is caused by the rise in sweat saturating the clothing and skin surface clogging sweat ducts.
2. Heat Syncope: Heat syncope, or fainting caused by heat, can happen during excessive heat exposure because blood is being shunted to the skin and extremities. Rapid changes in body position (frequently seen in sitting to standing, or bending over and standing back up) may lead to a temporary change in blood pressure that causes an individual to faint. Most athletes recover quickly once laid flat, which allows blood flow to normalise. That being said, falling due to a rapid loss of consciousness could lead to a concussion, and an athlete who faints due to heat should be evaluated before being allowed to continue training or competing.
3. Heat Cramps: Heat cramps or muscle spasms have been notoriously linked with dehydration and electrolyte imbalances over the years. However, exercise-associated muscle cramps are more commonly related to a wider range of variables like fatigue and muscular imbalances. Although harmful to performance, exercise-associated muscle cramps are generally harmless to our health and most ordinarily occur on one side of the body. If experiencing bilateral, or both sides, cramping or full body cramping, this is often linked to a more serious condition like extreme dehydration or hyponatremia (depleted electrolytes from excessive water consumption) and should be immediately addressed by a physician or the medical team at the event.
4. Heat Exhaustion: Heat exhaustion should be taken seriously and managed quickly because it can advance to severe and potentially life-threatening conditions like heat stroke. Heat exhaustion classically presents with fatigue, dizziness, excessive sweating, nausea, vomiting, headache, fainting, weakness, and cold, clammy skin. An athlete with exhaustion typically still has normal cognitive and neurological function. They should be able to answer questions about their condition, where they are, who they are, etc.
5. Heat Stroke: Heatstroke is characterized by a core body temperature >104°F (40°C) with altered central nervous system functions such as irritability, confusion, combativeness, or maybe worse, loss of consciousness. Hot and dry skin is a sign of heat stroke, but it is important to understand an athlete may be sweating and still have heat stroke. The altered CNS function is the hallmark difference between heat exhaustion and heat stroke, but when unsure, treat the situation as if the athlete has heat stroke. Athletes showing signs of heat stroke have to be treated by medical professionals as soon as possible. It should be stressed that heat stroke is incredibly severe and may cause death if not treated quickly.

People at risk

• The Elderly
• Being dehydrated.
• Age-related changes to the skin such as impaired blood circulation and inefficient sweat glands.
• Heart, lung and kidney diseases, as well as any illness that causes general weakness or fever.
• High blood pressure or other conditions that require changes in diet. eg people on salt-restricted diets may be at increased risk. However, salt pills should not be used without first consulting a doctor.
• Reduced sweating, caused by medications such as diuretics, sedatives, tranquilizers and certain heart and blood pressure drugs.
• Taking several drugs for various conditions. It is important, however, to continue to take prescribed medication and discuss possible problems with a physician.
• Being substantially overweight or underweight.
• Drinking alcoholic beverages.
• Traumatic brain injured patients
• Exercise overdose

Management

Normal Body Temperature

If you suspect that someone is suffering from a heat-related illness:

1. Get the person out of the heat and into a shady, air-conditioned or other cool place. Urge them to lie down.
2. If you suspect heat stroke, call emergency number.
3. Encourage the individual to shower, bathe or sponge off with cool water.
4. Apply a cold, wet cloth to the wrists, neck, armpits, and/or groin. These are places where blood passes close to the surface of the skin, and the cold cloths can help cool the blood.
5. If the person can swallow safely, offer fluids such as water, fruit and vegetable juices, but avoid alcohol and caffeine

Cooling Technique

Indications for cooling include any signs of heat-related illness in the presence of an elevated body temperature. Previously, heat-related illness has been defined as core body temperature greater than 40 C. However, any elevation above normal body temperature in asymptomatic patient is an indication to consider cooling.

• The objective is to rapidly decrease the temperature below 40 C, with the final goal of reaching normal range (36°^C to 38°^C).
• It is important to note if the patient's other vital signs, like hemodynamic instability, indicate severe heat stroke, in which case, rapid cooling is the most crucial intervention to stabilize the patient.