A dangerous reduction of blood flow throughout the body tissues, which may occur with severe injury or illness. Shock in this sense is physiological shock, as distinct from the mental distress that may follow a traumatic experience. In most cases, reduced blood pressure is a major factor in causing shock and is one of its main features. Shock may develop in any situation in which blood volume is reduced, blood vessels are abnormally widened, the heart’s action is weak, blood flow is obstructed, or there is a combination of these factors. Causes include severe bleeding or burns, persistent vomiting or diarrhoea, myocardial infarction, pulmonary embolism, peritonitis, and some types of poisoning. Symptoms of shock include rapid, shallow breathing; cold, clammy skin; rapid, weak pulse; dizziness; weakness; and fainting. Untreated, shock can lead to collapse, coma, and death. Emergency treatment is required. This involves an intravenous infusion of fluid, a blood transfusion, oxygen therapy, and, if necessary, morphine or similar powerful analgesics. Further treatment depends on the underlying cause. (See also anaphylactic shock; septic shock; shock, electric; toxic shock syndrome.)


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