Final answer:
A nurse should administer a diuretic to a client with stage IV heart failure, crackles in the lungs, and fluid overload to reduce blood volume and alleviate symptoms.
Step-by-step explanation:
The medication that a nurse should plan to administer to a client with stage IV heart failure, crackles in the lungs, and fluid overload is a diuretic. Diuretics are prescribed to reduce blood volume and alleviate fluid overload, which is a common problem in advanced heart failure. By promoting the excretion of excess fluids and sodium through urine, diuretics help relieve symptoms like pulmonary congestion indicated by crackles in the lungs. A frequently used diuretic in such cases is hydrochlorothiazide, which inhibits the Na/Cl symporter in the distal convoluted tubule (DCT) and collecting duct, resulting in a loss of sodium along with water, which follows passively by osmosis. This mechanism of action is consistent with the drug working on the loop of Henle and inhibiting the reabsorption of Na* and Cl-.