Question

Your patient has lost a lot of blood. Because his blood type was unknown at first they did a ringers and then plasma replacement for volume instead of whole blood. This morning’s complete blood cell count was measured at 37%.

​A) What condition is this? How do you expect the kidney’s to respond in terms of cells?

Answer 1

A. The patient has lost a lot of blood as his RBC count is only 37%. Normal blood counts should be 45% of blood. This condition is known as hemorrhage. Hemorrhage is excessive blood loss or bleeding. Due to bleeding, the renal blood flow to the kidneys is also decreased. Kidneys receive 20-25% of the cardiac output. Hence, if the cardiac output decreases, blood flow to kidneys also decreases. The sympathetic nerve fibers in the kidneys will release norepinephrine, which is a vasoconstrictor. The release of norepinephrine will increase the vascular resistance. This leads to decreased flow to the kidneys.

In response to reduced blood flow, juxtamedullary cells of the kidneys will secrete renin. Renin stimulates Aldosterone secretion in adrenal cortex, which increases absorption of water and sodium, urine output will decrease. This is the mechanism to increase blood volume.

In terms of cells, the kidneys respond to hemorrhage and will stimulate the secretion of erythropoietin by the interstitial fibroblast. Erythropoietin is the hormone which will stimulate the production of red blood cells by bone marrow. Erythropoietin stimulates hematopoietic stem cells in the bone marrow to differentiate into red blood cells. Thus, number of red blood cells will increase in blood.