Question

Hypo-volemic shock, a sudden loss of a large volume of blood, can cause arterial blood pressure to drop significantly, which can compromise blood flow. However, if the loss of blood is not too great, say less than 20% or so, the circulatory system usually responds almost immediately in two ways to restore adequate blood flow. Based upon your understanding of the circulatory system, and control of blood pressure explain what quick cardiovascular adjustments are made to restore flow. Be sure to explain how each adjustment works

Answer 1

When blood loss is less than 10 percent of total volume then it results in first stage or compensated stage of hypovolemic shock.

Regulatory mechanisms operate successfully to reestablish normal blood pressure. They are

1. Baroreceptor mechanism

2. Renal mechanism and ADH mechanism.

1. BARORECEPTOR MECHANISM –

The ischemic response by baroreceptors immediately initiate strong sympathetic stimulation which leads to vasoconstriction associated with tachycardia.

2. RENAL MECHANISM –

In response to shock the JG apparatus of the kidney releases large amounts of renin which further results in formation of angiotensin 2. Angiotensin 2 results in potent vasoconstriction. It also increases the release from adrenal cortex. Aldosterone in turn promotes retention of salt and water by kidneys which helps kidneys in restoration of blood pressure.

ADH MECHANISM –

ADH also causes retention of water by kidneys and it also enhances the vasoconstriction.

Because of severe vasoconstriction caused by regulatory mechanisms, normal blood pressure is established. Retention of water by kidneys along with the fluid shift mechanism that moves water from interstitial space and interstitial lumen restores the blood volume.