The nurse is caring for a client who is receiving gentamicin IV. Which adverse effect is most important for the nurse to report to the healthcare provider (HCP)?

Choice A reason: Vertigo can occur with gentamicin due to ototoxicity, but it is not as immediately life-threatening as nephrotoxicity. While important, it does not represent the most urgent adverse effect to report compared to renal impairment. Choice B reason: Nausea is a common side effect of many medications, including antibiotics. It is uncomfortable but not dangerous, and it does not require urgent reporting unless severe or persistent. Choice C reason: Headache may occur with gentamicin use, but it is nonspecific and not a critical adverse effect. It does not indicate organ damage or toxicity. Choice D reason: Oliguria is the most important adverse effect to report because gentamicin is nephrotoxic. Reduced urine output indicates impaired kidney function, which can progress to acute renal failure if not addressed promptly. Early recognition and reporting allow for immediate intervention, such as discontinuing the drug or adjusting the dosage, to prevent permanent renal damage.