Stages of shock
shock is divided into the following three major stages:1. A nonprogressive stage (sometimes called the compensated stage), in which the normal circulatory compensatory mechanisms eventually cause full recovery without help of therapy.
2. A progressive stage, in which, without therapy, the shock becomes steadily worse until death.
3. An irreversible stage, in which the shock has progressed to such an extent that all forms of known therapy are inadequate to save the
person’s life.
Nonprogressive Shock : It is also called compensated shock, meaning that compensatory mechanisms are enough to prevent further deterioration of the circulation.
The compensatory mechanisms include:
1. Baroreceptor reflexes, which elicit powerful
sympathetic stimulation of the circulation.
2. Central nervous system ischemic response,
3. Reverse stress-relaxation of the circulatory system,which causes the blood vessels to contract around the diminished blood volume, so that the blood volume that is available more adequately fills the circulation.
4. Renin angiotensin system.
5. Formation of vasopressin (antidiuretic hormone) by the posterior pituitary gland, increases water retention by the kidneys.
6. Stimulation of thirst center and increase appetite for salt intake.
Progressive Shock:
-Cardiac Depression. When the arterial pressure falls low enough, coronary blood flow decreases below that required for adequate nutrition of the myocardium. This weakens the heart muscle and thereby decreases the cardiac output more.
-Vasomotor Failure sever arterial blood reduction cause vasomotor center depression so no further sympathetic stimulation.
-Blockage of Very Small Vessels—due to sluggish blood flow.
-Increased Capillary Permeability. After many hours of capillary hypoxia and lack of other nutrients, the permeability of the capillaries gradually increases, and large quantities of fluid begin to transude into the tissues. This decreases the blood volume even more.
-Release of Toxins by Ischemic Tissue.
Irreversible Shock Aftershock has progressed to a certain stage, transfusion or any other type of therapy becomes incapable of saving the person’s life.
Physiology of treatment in shock:
-Replacement therapy Blood and Plasma Transfusion. If a person is in shock caused by hemorrhage, the best possible therapy is usually transfusion of whole blood. If the shock is caused by plasma loss, the best therapy is administration of plasma; when dehydration is the cause, administration of an appropriate electrolyte solution can correct the shock.
-Treatment of Shock with Sympathomimetic Drugs—Sometimes Useful These drugs include norepinephrine, epinephrine, these drugs can be used in neurogenic shock, in which the sympathetic nervous system is severely depressed and in anaphylactic shock, The sympathomimetic drugs have a vasoconstrictor effect that opposes the vasodilating effect of histamine.
-Other Therapy
Treatment by the Head-Down Position. When the pressure falls too low in most types of shock, especially in hemorrhagic and neurogenic shock, placing the patient with the head at least 12 inches lower than the feet helps tremendously in promoting venous return,
Oxygen Therapy. Because the major deleterious effect of most types of shock is too little delivery of oxygen to tissue.