An elevated trough must be reported before the next dose is given.
Before you read
Test yourself first: 5 questions
Question 1 of 5
A nurse is caring for a client receiving IV vancomycin with a scheduled trough level. When should the nurse ensure the trough blood sample is drawn?
Answer: A. A trough level is drawn just before (within about 30 minutes of) the next scheduled dose to measure the lowest concentration and guide dosing. A peak is drawn after the dose has distributed. Drawing during or immediately after the infusion would reflect a peak, not a trough.
Question 2 of 5
A client receiving an aminoglycoside (e.g., gentamicin) has 'peak and trough' levels drawn to:
Answer: B. Peak and trough monitoring ensures the drug is therapeutic (peak) and not accumulating to toxic, nephro/ototoxic levels (trough). Doses are adjusted accordingly.
Question 3 of 5
An order reads gentamicin 7.5 mg/kg/day divided every 8 hours for a 12 kg child. How many milligrams should the nurse give per dose?
Answer: B. Daily dose is 12 kg times 7.5 mg/kg equals 90 mg/day. Every 8 hours means 3 doses per day, so 90 divided by 3 equals 30 mg per dose.
Question 4 of 5
A nurse is teaching a client about using a peak flow meter at home to monitor asthma control. The client's personal best is 400 L/min and today's reading is 250 L/min. Into which zone does this reading fall?
Answer: B. Peak flow zones are based on percentage of personal best: green (good control) is 80 to 100 percent, yellow (caution) is 50 to 79 percent, and red (medical alert) is below 50 percent. A reading of 250 L/min is 62.5 percent of a personal best of 400, which falls in the yellow zone, indicating the client should follow the action plan and may need the rescue inhaler.
Question 5 of 5
A client on an aminoglycoside antibiotic (e.g., gentamicin) should be monitored for which toxicities?
Answer: B. Aminoglycosides are nephrotoxic and ototoxic — monitor renal function (creatinine), hearing/balance, and peak/trough levels.
Keep the streak going with more questions like these, each with a full rationale.
What is gentamicin (peak and trough)?
Its major toxicities are nephrotoxicity and irreversible ototoxicity. The key principle is drawing peaks and troughs correctly so the trough stays low enough to protect the kidneys and ears.
Key points to remember
- Gentamicin is a bactericidal aminoglycoside with a narrow therapeutic window requiring serum level monitoring.
- The trough is drawn just before the next dose and the peak is drawn about 30 minutes after the infusion ends.
- A high trough reflects drug accumulation and increases the risk of nephrotoxicity and ototoxicity.
- Nephrotoxicity is usually reversible, but ototoxicity (hearing loss, tinnitus, vertigo) can be permanent.
- Therapeutic trough is generally below 2 mcg/mL and therapeutic peak is roughly 5 to 10 mcg/mL for traditional dosing.
- The risk increases when combined with other nephrotoxic drugs such as loop diuretics or vancomycin.
Nursing priorities
- Draw the trough right before the next dose and the peak about 30 minutes after the infusion ends.
- Hold the dose and notify the provider if the trough is elevated.
- Monitor renal function, intake, and output throughout therapy.
- Assess for ototoxicity by asking about tinnitus, hearing changes, and dizziness.
- Ensure adequate hydration and avoid concurrent nephrotoxic drugs when possible.
Labs & values
Patient teaching
- Report any ringing in the ears, hearing changes, or dizziness right away.
- Drink plenty of fluids unless your provider restricts them.
- Blood will be drawn at specific times to keep the drug at a safe level.
- Report any decrease in your urination.
Red flags: report now
- An elevated trough must be reported before the next dose is given.
- Tinnitus, hearing loss, or vertigo may indicate ototoxicity and must be reported promptly.
- Decreased urine output or rising creatinine signals nephrotoxicity and must be reported.
References
Clinical references for this topic
