Freeze phenomenon

Introduction Freezing, also known as accidental hypothermia, is a serious systemic disease caused by hypothermia caused by cold environment and mainly caused by nervous system and cardiovascular damage. Frostbite (forstbite) is a local tissue damage caused by cold, which is more common in limbs and face. Frostbite is a local temperature that is too low, resulting in local vasoconstriction, post-expansion, increased capillary wall permeability, plasma exudation, tissue edema, intravascular blood concentration and vascular wall damage, resulting in thrombosis leading to tissue necrosis. Lesions can be limited to the skin or involve deep tissues, including muscles and bones.

Cause

Freezing often occurs when staying in a cold environment and working for too long, and its lack of warmth and cold protection measures can also occur when it is buried in snow or immersed in ice water. Frostbite can occur at temperatures that are not too low, even above 0°C, often due to wearing tight or wet footwear. Old people, infants, extremely debilitated and chronic cardiovascular disease, patients with anterior pituitary and hypothyroidism, cerebral vascular sequelae, occasionally in the low temperature room can also occur frozen and frostbite. Hunger, fatigue, alcohol, etc. are more likely to induce this disease.

Freezing is a skin temperature and deep-temperature receptor that stimulates the anterior view of the brain. The adrenergic sympathetic nerve contracts the surface to maintain body temperature, while the motor nerves increase muscle tension and jitter to generate heat. However, the added heat is limited, only 40% to 60% more than in the quiet state. Cold causes an increase in oxygen consumption and cardiac output. In an environment of 5 ° C, the oxygen consumption is increased by about 3 times and the cardiac output is increased by 95%. The cold affects awareness and thinking activities, reducing responsiveness and ability to work. When the cold continues to exist, the body temperature drops below 35 ° C and is called low temperature. Low temperatures affect brain and heart function and impede energy metabolism such as glucose. When the body temperature is 26 ~ 33 °C, the cold directly acts on the myocardium, slows the heartbeat and arrhythmia; at 17~26 °C, the hemoglobin and oxygen have increased affinity, the oxygen release is reduced, and the tissue is hypoxic; at 12 °C, the cell membrane sodium channel Blocking, sodium ions can not enter the cell, so that the muscle fiber has no stress reaction, and there is sensory and motor nerve paralysis. The surrounding blood vessels dilate and cause heat loss, further causing the body temperature to drop. If the hypothermia is short, the function of the nerves and muscles can be restored when the body temperature rises. If the hypothermia lasts for several hours, the nerves and muscles undergo degeneration, and even if the body temperature returns to normal, its function is difficult to recover. After freezing, the vascular endothelial cells are damaged. After thawing, thrombus is formed in the lumen of the blood vessel and tissue ischemic necrosis is caused.

an examination

Related inspection

Skin test body temperature measurement

Frostbite is a local temperature that is too low, resulting in local vasoconstriction, post-expansion, increased capillary wall permeability, plasma exudation, tissue edema, intravascular blood concentration and vascular wall damage, resulting in thrombosis leading to tissue necrosis. Lesions can be limited to the skin or involve deep tissues, including muscles and bones.

Differential diagnosis

The skin of the frostbite is pale, cold, painful and numb. According to the degree of damage, it is clinically divided into four degrees. The first and second degrees are mainly tissue blood circulation disorders, and the third and fourth degrees have different depths of tissue necrosis.

Once: shallow skin frostbite. The skin began to pale, followed by blue-violet, and later redness, itching, tingling and paresthesia.

Second degree: frostbite on the whole skin. In addition to redness and swelling, blisters appear and are susceptible to infection after blistering. If there is no infection, after 2 to 3 weeks, the water will dry up and become a cockroach.

Third degree: frostbite affects the full layer of the skin and subcutaneous tissue. The skin changes from pale to blue, turning to black, and the feeling disappears. Necrotic tissue shedding forms ulcers and is prone to secondary infection. It can leave scars after healing and can affect function.

Four degrees: skin, subcutaneous tissue, muscles, and even bones are frostbitten. The frostbite is dark gray, with edema and blisters on the edges, and complete loss of sensation and movement. After 2 to 3 weeks, the necrotic tissue was clearly demarcated, forming dry gangrene, edema and secondary infection turned into wet gangrene. There are often disabilities and dysfunctions. A small number of infections can be complicated by pneumonia, pericarditis.

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