A nurse is reviewing the laboratory results of a client who received a dose of sodium polystyrene sulfonate. Which of the following labs should the nurse monitor to evaluate if the medication has been effective?

Atorvastatin is an HMG-CoA reductase inhibitorthat lowers cholesterol by blocking the rate-limiting step of hepatic cholesterol synthesis. Its primary therapeutic goal is the reduction of atherogenic lipoproteinsto prevent cardiovascular disease and stroke. Effective therapy is measured by a significant improvement in the lipid profile, specifically targeting the reduction of low-density lipoproteins(LDL).

Rationale:

A.Decreased HDL levels would indicate a worsening of the patient's cardiovascular risk profile rather than effective treatment. High-density lipoprotein (HDL) is considered "good" cholesterol because it helps remove other forms of cholesterol from the bloodstream. A successful response to statin therapy would involve maintaining or slightly increasing HDL levels to provide better cardioprotective benefits.

B.Increased serum transaminase levels are an adverse effect of atorvastatin indicating potential hepatotoxicity, not therapeutic effectiveness. Statins are metabolized by the liver and can occasionally cause inflammation or damage to hepatocytes. If these enzymes (AST and ALT) rise significantly, the nurse must report this finding as it may necessitate the discontinuation of the medication.

C.Decreased LDL levels are the hallmark indicator of effective atorvastatin therapy. Low-density lipoprotein is the primary target for statins because it contributes to plaque buildup in the arteries, leading to atherosclerosis. A significant reduction in LDL proves that the HMG-CoA reductase inhibitor is successfully lowering the production of harmful cholesterol and reducing overall cardiovascular risk.

D.Increased creatine kinase (CK) levels are a laboratory marker for muscle damage and a sign of a serious adverse effect called rhabdomyolysis. This condition involves the breakdown of skeletal muscle fibers, which can lead to acute renal failure. Elevated CK levels are a reason for concern and immediate clinical intervention, not a sign that the cholesterol-lowering treatment is working.

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.