During clinical hemodialysis in a patient suffering from acute renal uremia, how is the dialyzing fluid formulated relative to the patient's blood plasma?

Answer and explanation

Correct answer: D. Matches plasma mineral composition but lacks nitrogenous wastes to allow waste diffusion

  1. Step 1: In hemodialysis, blood is drawn from a peripheral artery, anticoagulated with heparin, and pumped through a cellophane dialyzer unit.
  2. Step 2: The dialyzing fluid surrounding the porous cellophane tubing is formulated to have the exact osmolarity and electrolyte balance as normal blood plasma.
  3. Step 3: Because the dialysate contains zero urea, uric acid, and creatinine, these toxic metabolic wastes diffuse freely down their steep concentration gradients out of the blood across the cellophane membrane into the dialyzing fluid.
Answer
It has the identical mineral electrolyte composition as plasma but is completely devoid of nitrogenous wastes like urea and creatinine
Why not the others: 'It contains twice the normal concentration of urea...' would cause fatal urea diffusion into the patient's blood; 'It is completely free of all electrolytes, containing only pure distilled water' would cause massive hemolysis due to severe osmotic water influx into erythrocytes; 'It contains high concentrations of potassium...' would cause hyperkalemia and lethal cardiac arrhythmias.

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