A nurse is caring for a client whose current bag of total parenteral nutrition (TPN) has finished infusing, and the next bag is not yet available. Which of the following fluids should the nurse prepare to administer?

Phenytoin is a hydantoin anticonvulsantthat stabilizes neuronal membranes by delaying the influx of sodium ions during action potentials. It has a narrow therapeutic indexand significant effects on cardiac conduction, specifically lengthening the refractory period. Due to its potential to depress myocardial automaticity, it is strictly avoided in patients with certain pre-existing conduction system abnormalities.

Rationale:

A.Sinus bradycardia is a major contraindication for phenytoin because the drug can further depress cardiac conduction and automaticity. Phenytoin possesses class IB antiarrhythmic properties, which can lead to severe cardiovascular collapse or heart block in patients with slow heart rates. Administering this drug to a bradycardic patient poses a life-threatening risk of asystole.

B.A history of cholecystitis, or inflammation of the gallbladder, does not contraindicate the use of phenytoin for seizure management. While phenytoin is metabolized by the liver, it does not have a direct impact on gallbladder function or the formation of gallstones. The nurse would prioritize monitoring liver enzymes rather than focusing on a history of cholecystitis.

C.Taking vitamin B12 supplements does not prevent a patient from receiving phenytoin, as there is no dangerous interaction between the two. Interestingly, long-term phenytoin use is actually associated with folate deficiency rather than issues with B12. Supplements are generally safe and may be necessary for patients with concurrent nutritional deficiencies during anticonvulsant therapy.

D.Ibuprofen is a non-steroidal anti-inflammatory drug that does not have a documented clinical contraindication with the administration of phenytoin. While phenytoin has many drug-drug interactions involving the cytochrome P450 system, ibuprofen is not typically one that causes toxicity. The nurse can safely administer both medications as long as standard monitoring is performed.

Spironolactoneis a potassium-sparing diuretic that functions as an aldosterone antagonistin the distal convoluted tubule and collecting duct. It promotes the excretion of sodium and water while retaining potassium, making it effective for hypertension but dangerous in the presence of renal insufficiency. Significant contraindications include pre-existing hyperkalemiaor concurrent use of other medications that inhibit the renin-angiotensin-aldosterone system, as these combinations exponentially increase the risk of lethal cardiac dysrhythmias.

Rationale:

A. The client is currently taking lisinopril, an ACE inhibitor, which also increases serum potassium by suppressing aldosterone secretion. Combining lisinopril with spironolactone creates a synergistic effect that leads to severe hyperkalemia. This drug-drug interaction is a major clinical concern because both agents reduce the kidneys' ability to excrete potassium. The nurse must report this concurrent therapy to prevent potential cardiac toxicityresulting from excessive potassium accumulation.

B. The client's potassium level of 5.6 mEq/L already indicates hyperkalemia, as it exceeds the normal physiological limit of 5.0 mEq/L. Administering spironolactone to a client with an already elevated potassium concentration is strictly contraindicated. Increasing the potassium burden through potassium-sparingeffects could lead to peaked T waves, conduction blocks, or asystole. This laboratory finding must be addressed and corrected before any further potassium-retaining medications are administered.

C. A BUN(blood urea nitrogen) of 30 mg/dL signifies impaired renal clearance and decreased glomerular filtration. Elevated nitrogenous waste products often indicate that the kidneys are unable to maintain proper electrolyte balance. Since spironolactone relies on renal excretion and affects renal tubular transport, its use in a client with azotemia is highly risky. This finding suggests the client is at an increased risk for metabolic imbalancesif the diuretic is initiated.

D. A creatininelevel of 2 mg/dL is double the upper limit of the normal range, indicating significant renal dysfunction. Spironolactone is generally contraindicated or requires extreme caution in patients with a creatinine clearance that is significantly reduced. Impaired renal function prevents the body from managing the potassium-sparing effects of the drug, leading to a rapid and dangerous rise in serum electrolytes. This objective marker of kidney failuremakes the new prescription inappropriate for the client's current clinical status.