A 70-year-old client on day 6 of gentamicin develops creatinine rising from 1.0 to 1.6 mg/dL, urine output 0.4 mL/kg/h, new tinnitus, and reports the room "feels like it is spinning" with unsteady gait. Which is the priority nursing action?

Aminoglycosides cause both nephrotoxicity and ototoxicity. Nephrotoxicity is reversible if recognized early — risk increases with prolonged therapy more than 5 to 7 days, supratherapeutic trough levels, advanced age, hypovolemia, pre-existing renal disease, and concurrent nephrotoxins (vancomycin, IV contrast, NSAIDs, ACE inhibitors, ARBs, loop diuretics). Ototoxicity affects both vestibular (vertigo, ataxia, oscillopsia, fall risk) and cochlear (high-frequency hearing loss progressing to lower frequencies, tinnitus); cochlear damage can be permanent. The combination in this scenario — rising creatinine, oliguria, new tinnitus, vertigo — strongly suggests aminoglycoside toxicity. Standard nursing response: (1) hold the next dose and notify the prescriber immediately; (2) anticipate dose hold or discontinuation and substitution with a non-aminoglycoside agent guided by culture; (3) repeat creatinine and aminoglycoside trough; (4) audiology consult for formal hearing evaluation, vestibular assessment for balance and gait safety; (5) fall precautions — bed rails, call light within reach, assistance with ambulation, footwear, and reorientation; (6) review and minimize concurrent nephrotoxins; (7) ensure adequate hydration unless contraindicated. Documenting and continuing, increasing the dose, and adding a second aminoglycoside are unsafe.

AKI plus tinnitus plus vertigo on day 6 = aminoglycoside toxicity. Hold and notify, fall precautions, audiology and renal evaluation. Cochlear damage may be permanent.