Physiologic Effects of Acute Renal Failure
A major physiologic effect of acute renal failure is retention in the blood and extracellular fluid of water, waste products of metabolism, and electrolytes. This can lead to water and salt overload, which in turn can lead to edema and hypertension. Excessive retention of potassium, however, is often a more serious threat to patients with acute renal failure, because increases in plasma potassium concentration (hyperkalemia) to more than about 8 mEq/L (only twice normal) can be fatal. Because the kidneys are also unable to excrete sufficient hydrogen ions, patients with acute renal failure develop metabolic acidosis, which in itself can be lethal or can aggravate the hyperkalemia.
In the most severe cases of acute renal failure, com-plete anuria occurs. The patient will die in 8 to 14 days unless kidney function is restored or unless an artifi-cial kidney is used to rid the body of the excessive retained water, electrolytes, and waste products of metabolism. Other effects of diminished urine output, as well as treatment with an artificial kidney, are dis-cussed in the next section in relation to chronic renal failure.