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.

Background and objective The aim of the study was to test the peripheral analgesic action of neostigmine. Intraplantar administration of neostigmine was studied in carrageenan-injected rats.

Methods After assessing baseline values (T0) for paw circumference and the paw withdrawal threshold on both hind paws, the right hind paw was injected with 0.2mL of 1% carrageenan and the left hind paw with 0.2mL of saline (0.9% NaCl). Two hours later (T1), both hindpaws were tested for inflammation (paw circumference) and for hyperalgesia (paw withdrawal threshold) and subsequently 20 mg of neostigmine was injected in the right hind paw. The paw withdrawal threshold was tested again 10 (T2), 20 (T3) and 60 min (T4) and paw circumference 60 min (T4) after neostigmine injection.

Results Carrageenan injection in the right hindpaw was associated with a decrease in the paw withdrawal threshold reflecting mechanical hyperalgesia (P < 0.001) and an increase in paw circumference reflecting oedema (P < 0.001) in the right hind paw when compared with the left side from T1 to T4. Neostigmine had no effect on paw circumference and the paw withdrawal threshold at measuring points T2, T3 and T4 when compared with T1 in the right hindpaw. Conclusion Our results support the lack of peripheral analgesic effect of neostigmine.

Background and objective We have assessed the analgesic efficacy and side-effects of neostigmine when added to lidocaine for axillary brachial plexus block, in a prospective, randomized, double-blind, placebo-controlled study.

Methods We studied 34 ASA I or II patients undergoing elective ambulatory carpal tunnel release. Axillary brachial plexus block was performed using a peripheral nerve stimulator to locate the median nerve. All patients were administered 1.5% lidocaine 450 mg and epinephrine 5 μg mL−1. Patients were allocated randomly to one of two groups. Neostigmine 500|ig was added in group N, and saline 1 mL in group S.

Results The duration of analgesia did not significantly differ between groups [mean (SD)]: 812.5 (456.9) for group S vs. 746.7 (474.1) min for group N (P >0.05). The need for supplementary analgesia did not significantly differ between groups: 4.4 (1.5) extra doses for group S vs. 3.8 (2.2) extra doses for group N (P>0.05). Visual analogue pain scores and occurrence of side-effects did not significantly differ between groups.

Conclusion Neostigmine does not seem to be of clinical value for peripheral nerve blocks.

The aim of the present study was to evaluate the effects of neostigmine as a final anaesthetic manoeuvre on colonic anastomoses. A colonic anastomosis was constructed in 40 Sprague-Dawley rats. The animals were divided into two groups: (1) rats receiving intravenous saline solution (placebo); and (2) rats receiving an intravenous injection of neostigmine. The size of the caecum, and the diameters of the pre-anastomotic and post-anastomotic colon were measured during the operation and 4 days after surgery, when all the animals were sacrificed. At this time, the presence of adhesions was also investigated. Each segment containing an anastomosis was removed, and the bursting pressure and bursting wall tension were determined. Loss of caecum diameter was significantly greater in group 2 than in group 1 (P=0.03). Dilatation and obstruction of the colon were significantly more frequent in group 1 (dilatation, P=0.01; obstruction, P=0.047). Also, consumption of water by group 2 was greater than that by group 1 (P=0.049). No statistically significant differences were found between the diameters of the colon (pre- and post-anastomosis), or with respect to general adhesions and adhesions to the anastomotic line. No significant differences were found between anastomotic resistance (determined in terms of bursting pressure and bursting wall tension) in the two groups. The inclusion of neostigmine in an anaesthetic protocol under experimental setting did not reduce the resistance of colonic anastomoses and did not compromise normal healing. Moreover, obstruction caused by peristaltic weakness might be prevented by the expulsion of stool that is induced by the strong contraction of the colonic smooth muscle.