If no MEP responses are detected for 15-20 minutes after induction, which muscle relaxant was likely used?

When assessing the scenario where no motor evoked potential (MEP) responses are detected for 15-20 minutes following induction of anesthesia, the selected muscle relaxant is likely succinylcholine.

Succinylcholine is a depolarizing neuromuscular blocker that acts by binding to the nicotinic acetylcholine receptors at the neuromuscular junction, resulting in an initial depolarization followed by paralysis. This paralysis can be profound and rapid, leading to a significant reduction in MEP responses. The effects of succinylcholine are typically short-lived; however, if it were used in a situation where MEPs are still unobtainable for an extended period, it could indicate a prolonged neuromuscular block, potentially due to other underlying factors (such as electrolyte imbalances or atypical plasma cholinesterase).

In contrast, non-depolarizing muscle relaxants such as rocuronium, vecuronium, and cisatracurium have a different mechanism of action and their effects would generally be observable sooner, especially if neuromuscular monitoring is employed. These agents are competitive antagonists that inhibit neuromuscular transmission but do not produce the same immediate and profound block as succinylch