Page 373 - Critical Care Nursing Demystified

358 CRITICAL CARE NURSING DeMYSTIFIED

water at the distal tubule, which again conserves sodium and water. The RAAS
system does an excellent job in conserving water and sodium to increase intra-
vascular volume when activated in hemorrhagic shock or dehydration. How-
ever, this system creates a vicious cycle of unwanted sodium and fluid retention
when a poorly pumping heart is the culprit in dropping the GFR. Fluid and salt
retention can quickly lead to heart failure and cardiogenic shock, especially in
the patient with acute or chronic renal failure. Therefore, the RAAS is helpful
in any type of shock except cardiogenic.

Renin-Angiotension-Aldosterone System

Decreased arterial BP
Decreased GFR
Increase in renin secretion
Increase in angiotension I
Increase in angiotension II
↓
Decrease in water and salt excretion Increase in aldosterone
Concentration of urine excreted Increase in water and salt reabsorption Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
(short term) (Longer-term fluid retention)
Results in
↓
Increased intravascular volume
Increased GFR

The kidneys are essential organs impacting all body systems. The work of the
kidneys is extensive, including
Excreting waste products and excess fluid in the urine
Maintaining water balance and controlling BP
Controlling electrolytes levels
Maintaining acid-base balance

Stimulating production of red blood cells through erythropoietin
Activating vitamin D synthesis
Secreting prostaglandins and growth hormones
Circulation to the kidneys is supplied by the renal artery, which branches
from the abdominal aorta just above the mesenteric arteries. The kidneys
receive one-quarter of the blood into the renal artery, which articulates with