Shock is a circulatory disturbance characterized by acute reduction of blood flow and impaired profusion (blood supply) of tissue with resultant inadequate cellular oxygenation.
The effective blood flow is reduced rapidly as a consequences of decreased cardiac output, due to deficiency of venous return to the heart and impairment of cardiac function. The shock may be primary shock and secondary shock.
Primary or Initial Shock:
It results from sudden reduction of venous return to the heart caused by neurogenic vasodilation of splanchnic area. Primary shock occurs immediately after trauma or may result from severe pain due to various causes or from severe emotional disturbances such as fear, grief etc.
The patient becomes unconscious;there is paleness, weakness, weak and rapid pulse with low blood pressure. Some people call it "fainting fit". It is usually a transient neurovascular collapse.
Secondary or True Shock:
In fact it is due to difference between volume of blood and capacity of the vascular system.
The disparity may be due to decrease in the blood volume or increase in the volume capacity of vascular system or combination of both. It tends to be progressive in the form of circulatory failure and damage to the tissues of the body. It may kill the patient if not treated properly.
Due to anaerobic glycolysis taking place in the cells, there are lactic acid and pyruvic acid end products. The accumulation of these cause rupture of lysosome within cell which liberates lytic enzyme which causes death of the cell.
TYPES OF SHOCK:
The types of shock are generally classified on the basis of principal cause and these are:
1- TRAUMATIC SHOCK:
It is produced due to certain reasons which include excessive loss of blood from ruptured vessels which is primary cause, there is absorption of product of tissue autolysis from the area of injury which leads to generalized vascular permeability and traumatic shock may be related to pain and neurogenic mechanism postulated to cause alterations in the vasomotor control of peripheral circulation with peripheral pooling of blood.
2- HEMORRHAGIC SHOCK:
It follows acuter loss of critical volume of blood. The blood loss necessary to induce shock varies with rate of loss. Slow losses of even 40% of the blood volume is better tolerated than a sudden loss of 10-20%.
3- BURN SHOCK:
It is due to hypovolemia which in turn is due to loss of fluid mainly in the form of plasma in and about the lesions as a consequence of increased vascular permeability caused by thermal injury, vasoactive substances from burnt tissues are absorbed and increase the permeability and thus further reduce blood volume.
4- SURGICAL SHOCK:
This shock may be due to combination of prolonged anesthesia lowers blood pressure, hemorrhage during operation by cutting large blood vessels, emotional reactions.
5- SEPTIC SHOCK AND ENDOTOXIC SHOCK:
It occurs in patients having excessive bacterial infections. The most causative agents are the G- negative rods with their elaboration of endo-toxins. Hence it is also called G-negative endotoxic shock.
6- CARDIOGENIC SHOCK:
It is sometimes called circulatory collapse due to rapid insufficiency of cardiac pump.
Myocardial Infraction is the general cause. If infraction is severe, action of the heart muscles may be so impaired that it leads to decreased cardiac tamponade, pulmonary embolism and rupture of papillary muscles of cardiac valves. All those conditions lead to cardiac pump insufficiency.
Signs and Symptoms of Shock:
The sign and symptoms are pale and cool skin, cold sweat, cool nose tip, sunken eyes, anxiety, hypotension and shallow respiration.
Treatment of Shock:
Clinically in the treatment of shock corticosteroid administration has immense value. It certainly decreases capillary permeability and restores vessel wall tone. It is well known that administration of corticoids or various diseases cause adrenal atrophy.
So patients easily go into conditions of shock even under minor stress and anesthesia. The patient need much care and prompt therapy with corticoid.
The role of non-epinephrine in the treatment of shock is important. There is evidence that myocardial failure contributes to irreversibly of hemorrhagic shock.
References:
1- Wikipedia
2- https://www.medicinenet.com/shock/article.htm#shock_facts