Shock (Acute Peripheral Circulatory Failure)

Shock may be defined as a clinical state characterized by an acute fall on blood pressure usually below 80 mm Hg, tachycardia, feeble pulse which may even imperceptible, pale cold skin, perspiration, thirst and oliguria. Psysiologically, it represents an acute reduction in blood flow through the capaillaries with consequent dimunition in the blood supply to vital organs. As a result of these changes, both the transport of oxygen and other vutrients to the tissues and the removal of tissue metabolites are impaired; finally, functional and structural changes takes place in the organs affected. The last features distinguishes it from collapse which is of short duration and is not followed by organ damage. Following types of shock syndrome are usually well recognized. However, it is important to remember that though the various types of shock have been described separately, they are not mutually exclusive, and on occasions, more then one factor may be contributing towards the shock syndrome in a given case.

A.      Cardiogenic Shock.

This is primary due to impaired cardiac function though hypovolaemia may play a small contributory part in some cases.

B.      Septic Shock.

This is a special type of shock which result from severe infections, especially gram negative bacteraemia with release of endotoxins into the circulation.

C.      Neurogenic Shock.

Acute hypotension and shock are occasionally due to neuropathic factors and many follow:  Administration of certain drugs e.g., anaesthetics, sympathicolytics and other anti-hypertensive agents, ingestion of barbiturates and phenothiazines, B) Spinal cord injury and C) autonomic distribunces as in peripherial neuropathies and amyloidosis. Such cases will be need treatment according to the specific cause responsible for the shock.

D.      Anaphylatic Shock.

This is a special type of shock which may occurs with dramatic suddenness. It is due to antigen Antobody reaction which may induced by the antigenic substance. The most dangerious reactions occurs after administration of such agents intravenously but serious anaphylactic reaction may also follow their use by other routes such as intramuscular, subcutaneous, intradermal or even oral. In most of the anaphylaxix is related to IgE.

The shock in such cases is due to release of histamine and bradykinin which result in marked peripherial vasodilatation thereby reducing the quantity of circulatering blood with consequent hypotension. Clinically, it is characterized by features of laryngeal oedema, bronchospasm, urticarial eruption and angioedema.