Decreasing enflurane concentrations and d-tubocurarine neuromuscular blockade

To study the effect of decreasing the concentration of enflurane on a combined enflurane-d-tubocurarine (dTC) neuromuscular blockade, six ASA class I or II patients were studied using a continuous infusion of dTC and a sequence of decreasing end-tidal concentrations of enflurane. A constant infusion of dTC and a 2.2 per cent end-tidal concentration of enflurane decreased twitch tension to 8 per cent of control. Maintaining this same infusion rate of dTC, but decreasing the end-tidal concentration of enflurane to 1.35 and 0.5 per cent, increased the twitch tension to 57 and 91 per cent of control, respectively. The authors conclude that the enflurane contribution to muscle relaxation dissipates in a dose-dependent manner as the end-tidal concentration of enflurane is reduced. This factor may provide additional safety for patients because the anesthetic produces a component of relaxation that is readily reversible with time without the use of acetylcholinesterase inhibitors.