体温の低下

Hypothermia occurs when body temperature drops due to prolonged cold exposure that surpasses the body's ability to produce heat. Heat loss with extended cold exposure overpowers thermoregulation. It can develop accidentally through drowning in cold water or be induced deliberately during surgical procedures to reduce metabolism and oxygen requirements. Toxin exposures, metabolic imbalances, and infections also cause hypothermia.

Early hypothermia symptoms include shivering, memory loss, depression, and impaired judgment. Patients develop cyanosis as skin begins to turn blue. A slowed heart rate, shallow breathing, weak pulse, and low blood pressure also occur. These signs indicate the body's thermoregulation is failing and immediate intervention is needed.

Hypothermia is classified by core temperature readings. Mild hypothermia ranges from 32°C to 35°C and results from impaired thermoregulation. Moderate hypothermia occurs between 28°C and 32°C from sustained extreme cold exposure. Severe hypothermia falls below 28°C from prolonged extreme cold and can cause cardiac dysrhythmias, unconsciousness, and insensitivity to pain.

Frostbite develops from prolonged exposure to extreme cold when ice crystals accumulate inside cells, causing irreversible tissue damage and circulation loss. Earlobes, nose tips, fingers, and toes are particularly vulnerable due to their exposure and distance from the core. The affected region becomes white, waxy, stiff, and numb, with symptoms including severe pain and blisters.

Critical interventions include removing damp clothing and replacing it with dry garments, then covering patients snugly with blankets. In emergencies, have the patient rest under blankets adjacent to a warm person. Conscious patients benefit from consuming hot liquids like soup while avoiding alcohol and caffeinated beverages. Cover the head and place heating pads near heat-loss areas like the head and neck.

Accidental hypothermia is more common in older adults and frequently goes unnoticed because symptoms develop gradually and may be attributed to other conditions. Older adults have reduced ability to sense temperature changes and generate heat efficiently. Their impaired thermoregulation makes them vulnerable to hypothermia even in moderately cool environments, requiring heightened clinical awareness.

Severe hypothermia can cause life-threatening cardiac dysrhythmias and loss of consciousness. Patients become insensitive to painful stimuli and may exhibit clinical signs resembling death. In extreme frostbite cases, gangrene can develop, potentially requiring amputation. Both conditions pose serious health risks if not treated promptly with appropriate medical intervention.