A nurse is caring for a 4-year-old child who has meningitis and is receiving gentamicin. Which of the following laboratory values should the nurse report to the provider?

Gentamicin is an aminoglycoside antibiotic commonly used to treat severe bacterial infections, such as meningitis, in pediatric patients. Although highly effective, it has a narrow therapeutic window and is well-known for its potential to cause nephrotoxicity (kidney damage) and ototoxicity (hearing loss). Because the drug is primarily excreted by the kidneys, the nurse must meticulously monitor renal function markers, as an elevation in these values often indicates the onset of drug-induced acute kidney injury. Rationale: A. A creatinine level of 1.4 mg/dL is significantly higher than the expected reference range for a 4-year-old child and must be reported immediately. Creatinine is a byproduct of muscle metabolism that is filtered almost entirely by the kidneys; an elevation indicates a decrease in the glomerular filtration rate. This rise strongly suggests nephrotoxicity, requiring a possible dose adjustment or discontinuation of the medication to prevent permanent renal damage. B. A blood urea nitrogen (BUN) level of 12 mg/dL falls within the normal reference range for a child (5 to 18 mg/dL). Although BUN is used to assess kidney function, it is also influenced by other factors such as hydration status, protein intake, and liver function. Since this value is stable and within the expected limits, it does not suggest a complication of the gentamicin therapy. C. A BUN level of 6 mg/dL is at the lower end of the normal reference range for a 4-year-old child. A low BUN is generally not a cause for concern in this clinical setting and may simply reflect the child's small muscle mass or adequate hydration. It does not indicate the presence of drug-induced nephrotoxicity. D. A creatinine level of 0.3 mg/dL is within the expected reference range of 0.2 to 0.5 mg/dL for a preschool-age child. This finding suggests that the kidneys are effectively filtering waste products and that the gentamicin is not currently causing detectable nephrotoxic damage. The nurse should continue to monitor this value alongside serum drug levels (trough and peak) to ensure the medication remains at a safe and therapeutic concentration.