Hypovolemic Shock Caused by Plasma Loss
Loss of plasma from the circulatory system, even without loss of red blood cells, can sometimes be severe enough to reduce the total blood volume markedly, causing typical hypovolemic shock similar in almost all details to that caused by hemorrhage. Severe plasma loss occurs in the following conditions:
1. Intestinal obstruction is often a cause of severelyreduced plasma volume. Distention of the intestine in intestinal obstruction partly blocks venous blood flow in the intestinal walls, which increases intestinal capillary pressure. This in turn causes fluid to leak from the capillaries into the intestinal walls and also into the intestinal lumen. Because the lost fluid has a high protein content, the result is reduced total blood plasma protein as well as reduced plasma volume.
2. In almost all patients who have severe burns or other denuding conditions of the skin, so much plasma is lost through the denuded skin areas that the plasma volume becomes markedly reduced.
The hypovolemic shock that results from plasma loss has almost the same characteristics as the shock caused by hemorrhage, except for one additional com-plicating factor: the blood viscosity increases greatly as a result of increased red blood cell concentration in the remaining blood, and this exacerbates the slug-gishness of blood flow.
Loss of fluid from all fluid compartments of the body is called dehydration; this, too, can reduce the blood volume and cause hypovolemic shock similar to that resulting from hemorrhage. Some of the causes of this type of shock are (1) excessive sweating, (2) fluid loss in severe diarrhea or vomiting, (3) excess loss of fluid by nephrotic kidneys, (4) inadequate intake of fluid and electrolytes, or (5) destruction of the adrenal cortices, with loss of aldosterone secretion and conse-quent failure of the kidneys to reabsorb sodium, chloride, and water, which occurs in the absence of the adrenocortical hormone aldosterone.