shock

n.

the condition associated with circulatory collapse, when the arterial blood pressure is too low to maintain an adequate supply of blood to the tissues. The patient has a cold sweaty pallid skin, a weak rapid pulse, irregular breathing, dry mouth, dilated pupils, and a reduced flow of urine.

Shock may be due to a decrease in the volume of blood, as occurs after internal or external haemorrhage, burns, dehydration, or severe vomiting or diarrhoea. It may be caused by reduced activity of the heart, as in coronary thrombosis, myocardial infarction, or pulmonary embolism. It may also be due to widespread dilation of the veins so that there is insufficient blood to fill them. This may be caused by the presence of bacteria in the bloodstream (bacteraemic or toxic shock), a severe allergic reaction (anaphylactic shock: see anaphylaxis), overdosage with such drugs as opioids or barbiturates, or the emotional shock due to a personal tragedy or disaster (neurogenic shock). Sometimes shock may result from a combination of any of these causes, as in peritonitis. The treatment of shock is determined by the cause.