Shock is a term applied to any of a number of abnormal body conditions commonly characterized by lowered blood pressure accompanied by weak, rapid pulse, lowered metabolic rate, depressed body temperature, collapse or varying degrees of weakness, pallor, "cold sweats", rapid, shallow respiration, and, often, nausea and vomiting.
In primary shock, which occurs only immediately after injury or emotional disturbance, the symptoms are produced by the action of the nervous system on the blood vessels. Physical or psychic pain results in an expansion of the superficial capillaries of the body, which normally hold about twenty percent of the total blood volume at any one time; in shock these capillaries hold and retain over sixty percent of the total blood volume.
Secondary, traumatic, surgical, or wound shock is a form of shock occurring several hours after an injury or surgical operation; the symptoms in this form of shock are thought by scientists to be produced either by the toxic action of substances such as histamine, which are released at the site of injury, or by decrease in blood volume caused by the escape of blood or plasma into the tissues at the site of the injury. Secondary shock is especially important in wartime; improvements in methods of blood transfusion during World War II have re-sulted in more efficient prevention of shock. Transfusion of plasma or of whole blood increases the volume of circulating blood, raising the blood pressure and ensuring adequate distribution of oxygenated blood throughout the body. Recent experiments indicate that plasma substitutes, or plasma volume expanders, such as dextrin, gelatin, and periston, are more effective for this purpose than whole blood. The patient is kept warm and sedation is applied to relieve pain.
Anaphylactic shock is a form of shock resulting from body sensitization to proteins; this form of shock may result in quick death. The problem of anaphylactic shock is exceedingly complex because of the large number of protein substances to which individuals may become hypersensitive.
