Final answer:
An intravenous infusion of 5% dextrose with 0.45% sodium chloride and 20 mEq of potassium has been prescribed to prevent hypokalemia.
Step-by-step explanation:
The primary reason that an intravenous infusion of 5% dextrose with 0.45% sodium chloride and 20 mEq of potassium has been prescribed is to prevent hypokalemia.
Hypokalemia is a condition characterized by low potassium levels in the body. An intravenous infusion of potassium, along with fluids containing dextrose and sodium chloride, helps replenish potassium and maintain electrolyte balance in the postoperative client with a nasogastric tube set to low intermittent suction.