Shock

In medicine, shock (hypoperfusion) is a life-threatening medical emergency characterized by inability of the body to supply enough oxygen to meet tissue requirements. Hypotension is usually, though not always, present. Without prompt medical treatment, shock usually causes death.

Types of shock

• Hypovolemic shock. The single most common cause of shock is blood volume loss, resulting from a serious wound or a severe burn leading to hypovolemic shock.
• Cardiogenic shock is caused by the failure of the heart to pump effectively. This can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include arrhythmias, or cardiac valve problems.
• Distributive shock. As in hypovolemic shock there is an insufficient volume of blood. This form of relative hypovolaemia is the result of dilation of bloodvessels. Examples of this form of shock are:
• Septic shock is caused by overwhelming infection leading to vasodilation. It is treated by antibiotics, fluid replacement, and vasoconstrictors.
• Acute adrenal insufficiency is not infrequently the result of discontinuing corticosteroid treatment without tapering the dosage.
• Less commonly severe anaphylactic reactions may cause anaphylactic shock as allergens trigger widespread vasodilation and movement of fluid out of the blood into the tissues.
• The rarest cause of shock is acute spinal cord injury leading to neurogenic shock. Neurogenic shock is caused by the sudden loss of the sympathetic nervous system signals to the smooth muscle in vessel walls. Without this constant stimulation the vessels relax resulting in a sudden decrease in peripheral vascular resistance and decreased blood pressure.
• Obstructive shock. Hereby the flow of blood is obstructed. Several conditions result in this form of shock.
• Cardiac tamponade, in which blood in the pericardium prevents inflow of blood into the heart (venous return). Or constrictive pericarditis which has the same effect.
• Pneumothorax. Through increased intrathoracic pressure bloodflow to the heart is prevented (venous return).
• Pulmonary embolism is the result of a thromboembolic incident in bloodvessels of the lungs and hinders the return of blood to the heart.