Hypothermia and Hyperthermia are conditions associated with overwhelmed body mechanisms. When the core temperature of the body falls below the minimum temperature required to maintain basic metabolic functions, it is called hypothermia and when the body gains more heat than it loses it is called hyperthermia. This article will talk about both hyperthermia and hypothermia, and the differences between them in detail highlighting their clinical features, symptoms, causes, investigation, and also the course of treatment they require.
What is Hypothermia?
Hypothermia is a condition where the core temperature of the body falls below the minimum temperature required to maintain basic metabolic functions of the body. The minimum body temperature is considered to be 35 degrees Celsius. Even though the body temperature is regulated tightly by various mechanisms, when the body comes into contact with extreme cold, these normal heat generating mechanisms cannot keep up with the heat loss, and thus cause hypothermia. There are four levels of hypothermia: mild hypothermia (body temperature 32-35 degrees Celsius), moderate hypothermia (body temperature 28-32 degrees Celsius), severe hypothermia (body temperature 20-28 degrees Celsius) and profound hypothermia (body temperature less than 20 degrees Celsius).
Mild hypothermia triggers all the mechanisms that generate heat to regulate the body temperature. Therefore, the body reacts to hypothermia by shivering, high blood pressure, rapid heart rate, rapid breathing and constriction of peripheral blood vessels to generate/preserve heat. Blood glucose level rises because liver releases glucose, and insulin secretion falls, and entry of glucose into cells diminishes. In alcoholics, blood sugar level tends to go down.
Violent shivering, mild confusion, slow pace movements, and bluish discoloration of peripheries are symptoms of Moderate hypothermia. In severe hypothermia, heart rate and blood pressure drop significantly. Amnesia, slow speech occurs. Organ failure leads to death. Paradoxical undressing is a phenomenon where patients with hypothermia undress due to confusion. There is also a behavior called terminal burrowing where the affected tend to hide in an enclosed space.
Prevention of hypothermia includes proper clothing and abstaining from alcohol. Rewarming is the recommended method of treatment for hypothermia. Passive, external rewarming involves dry warm clothes and moving to a warm environment. This uses the normal reheating mechanisms of the body. Active external rewarming involves hot air and other heat generating devices. Active internal rewarming involves warmed intravenous fluids, irrigation of body cavities with warm saline.
What is Hyperthermia?
Hyperthermia develops because the body gains more heat than it loses. Body heat is tightly regulated. The brain has a set point temperature to use as a baseline in temperature regulation. In hyperthermia, the set point remains unchanged while in fever it changes. Dry, warm skin, nausea, vomiting, headache, and excessive sweating are symptoms of hyperthermia. Common causes of hyperthermia are heat stroke, drugs and protective equipment. Heat stroke occurs because body mechanisms of heat loss are overwhelmed by metabolic heat generation and high environmental temperature. Many antipsychotics, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, tricyclic antidepressants, amphetamines, cocaine, halothane, succinyl choline, and anticholinergic drugs can cause hyperthermia. Fever reducing drugs like paracetamol, NSAID do not lower body temperature in hyperthermia. If they do, then hyperthermia can be excluded. Low cost measures like light dressing, wet clothing, keeping wet with sweat, fans, air conditioning are very effective in preventing hyperthermia. The underlying cause for hyperthermia should be removed. Drug induced hyperthermia indicates the need for immediate cessation of the offending drug. Studies have shown that fever reducing drugs have a role in treating hyperthermia. Passive cooling involves resting in a shaded, cool area and removing clothes. Active cooling involves drinking cool water, air conditioning, and fanning.
What is the difference between Hypothermia and Hyperthermia?
• Both conditions are due to overwhelmed body mechanisms.
• Hypothermia is a drop in core body temperature while hyperthermia is a rise.
• Hypothermia triggers the heat preserving mechanisms while hyperthermia triggers the heat loss.
• Rewarming treats hypothermia while cooling treats hyperthermia.