It is defined as a generalized acute reduction in the perfusion of tissues by which there is oxygen deficiency in the cells. It is characterized by reduction in effective circulating volume and reduction in arterial blood pressure.
Etiology: Shocks are classified into 6 types, viz. hypovolemic, cardiogenic, vasogenic, endotoxic, neurogenic, anaphylactic. Hypovolemic shock occurs when there is severe haemorrhage, plasma or fluid loss due to burns, intestinal obstruction, vomiting, diarrhoea, diuresis and pancreatitis. Cardiogenic shock is seen in myocardial infarction, coronary block, cardiac arrest, congestive heart failure, acute heart failure and ventricular fibrillation. Vasogenic shock occurs owing to severe trauma, burn, intestinal rupture and prolapse of uterus, where there is loss of effective blood volume. Endotoxic shock takes place owing to various septicemic conditions particularly caused by Gram -ve organisms, at times by Gram + organisms. Absorption of toxins from intestine and mammary gland may also result in endotoxic or septic shock.Neurogenic shock is due to pain or depression of central nervous system. Anaphylactic shock occurs owing to antigen and antibody combination in abnormal way releasing histamine or histamine like substances leading to dilation of the vessels and reduction in effective blood volume.
Clinical signs: There is tachycardia, diminished heart sounds, muscular weakness and cold extremities. Mucous membranes are pale or slightly cyanotic. Pulse is weak and animal is in recumbency or coma.
Diagnosis: There is decrease in blood pH. Eosinophil count is increased due to adrenocortical dysfunction. Haemoconcentration may be present or absent. Plasma protein may or may not be decreased. BUN and creatinine levels are high. The ECG findings include prolongation of QRS interval and peaked T wave or inversion of T wave indicating myocardial ischemia as well as hyperkalemia.
Treatment: Blood volume can be restored by administration of blood, plasma expanders or isotonic fluid (saline solution, ringer's solution) depending upon the cause of the problem to prevent anoxia and tissue damage. Corrective measures should be taken to treat haemorrhage, sepsis or cardiac failure. Glucocorticoids should be administered as early as possible. Antibiotics, vasodilators, anti-inflammatory drugs, digitoxin and calcium therapy should be instituted depending on the cause of the shock. Animal should have access to sufficient fresh air.