There is some confusion about the contribution of reversal of residual paralysis to the occurrence of postoperative nausea and vomiting. The aim of this review is to discuss whether antagonism of residual paralysis is a cause of postoperative nausea and vomiting, and to assess the risk of residual paralysis if the reversal is omitted. Data from a meta-analysis published before 1998 were considered, along with trials published after that date to assess the influence of reversal of residual paralysis on postoperative nausea and vomiting, and the likelihood of harm when antagonism was omitted. Moreover, an overview of pathophysiological consequences, incidence and clinical consequences of residual paralysis is given and the actual criteria of the adequacy of neuromuscular recovery presented.

When emetic outcomes are combined across all trials and all different neostigmine doses, there is no beneficial effect from omitting neostigmine on postoperative nausea and vomiting, but there is some evidence of a dose-responsiveness with neostigmine; higher doses may have emetic properties. However, omitting reversal introduces a non-negligent risk of residual paralysis. An improved understanding of the pathological consequences of residual paralysis (i.e. impaired laryngeal and pharyngeal muscle function, alterations in hypoxic ventilatory control, reduced margin of safety) led to establishment of more rigorous criteria for defining adequacy of neuromuscular recovery. A train-of-four ratio of ≥0.9 is now accepted as the index of adequate recovery of neuromuscular function. Applying this new definition, residual paralysis becomes a frequent adverse side-effect. Neuromuscular recovery should therefore be routinely monitored in ambulatory patients and residual paralysis prevented by reversing neuromuscular block.