Question

Which inhalational anaesthetic agent is contraindicated in renal failure?

• A. Isoflurane
• B. Desflurane
• C. Halothane
• D. Methoxyflurane

Hint:

Think of the volatile agent whose extensive metabolism releases nephrotoxic fluoride.

Answer 1

The Correct Option is D

Step 1: Some volatile anaesthetics undergo metabolism that releases free inorganic fluoride ions. High serum fluoride levels are nephrotoxic and can damage the renal tubules, so a heavily metabolised agent is dangerous in patients with poor renal reserve.

Step 2: Methoxyflurane is the classic offender. It undergoes extensive metabolism, including intrarenal metabolism, generating large amounts of fluoride ion. This is the major cause of methoxyflurane nephrotoxicity, which can produce a high-output (polyuric) renal failure.

Step 3: Because of this fluoride-mediated nephrotoxicity, methoxyflurane is contraindicated in renal failure and is essentially no longer used in clinical practice. It is also hepatotoxic.

Step 4: Isoflurane, desflurane and halothane undergo far less metabolism and do not produce nephrotoxic fluoride levels, so they are not the answer.