Question

Define circulatory shock. Explain what hypovolemic shock is and list the ways a person may suffer from hypovolemic shock. Describe the mechanisms the body initiates in an attempt to compensate for shock, and how these mechanisms have the potential to maintain blood flow homeostasis.

Answer 1

Circulatory shock is defined as a syndrome in which tissues are hypoperfused ( reduced amount of blood flow)to the extent that blood flow is inadequate to maintain metabolic demands. this condition is charecterized by decreased blood pressure and decreased pulse rate.

Hypovolemic shock is most often the result of blood loss after a major blood vessel bursts or from a serious injury, this is a life-threatening condition that results when you lose more than 20 percent of your body's blood or fluid supply as a result it mahes it difficult for the heart pump blood to all parts of the body

Hypovolemic shock may occur due to bleeding from serious cuts or injury, ruptured ectopic pregnancy, could also occur due to severe dehydration, postoperative bleeding, etc

The body has a number of compensatory mechanisms that become activated in an attempt to restore arterial pressure and blood volume back to normal, in all these mecanism the principal theme is that reduction in blood volume during acute blood loss causes a fall in central venous pressure and cardiac filling. This leads to reduced cardiac output and arterial pressure.

Baroreceptor mechanism, these receptors are mechanoreceptors located in carotid sinus and in aortic arch,their function is to sense pressure changes by responding to change in the tension of the arterial wall, when there is drop in the blood pressure this will sensed by the baroreceptors as a result they decrease the firng of an impulse this causes vasomotor center to activate sympathetic activity in heart and blood vessels, this in turn will increase the heart rate and vasoconstriction this will in turn increase in blood pressure. sympathetic influence has  little direct influence on brain and coronary blood vessels, so these circulations can benefit from the vasoconstriction that occurs in other organs, so in this condition, cardiac output is redistributed from less important organs to the brain and myocardium, both of which are critical for survival.

The kidneys also play a role in response to reduced blood pressure, it releases renin as a part of Renin-Angiotensin-Aldosterone mechanism, renin causes , increased level of Angiotensin-2 and aldosterone, This causes vascular constriction, enhanced sympathetic activity, stimulation of ADH release, activation of thirst mechanisms, and very importantly, increased renal reabsorption of sodium and water to increase blood volume. and excretion of potassium, all these results in increased blood volume and blood pressure.