Comparision of Different Dose of Neostigmine at Advanced Decurarization

Neuromuscular blockers (NMB) are currently used in anesthesia. Residual paralysis (RP) due to NMB is responsible for respiratory disorders after extubation. Neuromuscular blockade is monitored by train-of-four (TOF) stimulation at the adductor pollicis. To exclude a RP a mechanomyographic TOF ratio of 0.9 is mandatory. But mecanomyography is not available in clinical routine. Acceleromyography is the most currently monitoring available in daily practice but it has been proved that an acceloromyographic (AMG) TOF ratio of 1.0 is necessary to exclude a RP. The incidence of RP in recovery room is underestimated. So to perform a safe extubation, reversal of the neuromuscular blockade is necessary when an AMG TOF ratio has not reached 1.0. Reversal of neuromuscular blockade is achieved with neostigmine. The recommended dose is 0.04 mg/kg. The administration of neostigmine causes parasympathomimetic effects which has to be reversed with atropine. When neuromuscular blockade is light (AMG TOF ratio of 0.4 which corresponds to the absence of fade at the visual evaluation of the TOF), a low dose of neostigmine might be sufficient with less side effects expected. The goal of the study is to compare the delay between a light neuromuscular block and an AMG TOF ratio of 1.0 for three neostigmine regimens of neostigmine 0.04, 0.02, 0.01 mg/kg with atropine respectively 0.02, 0.01, 0.005 mg/kg and a placebo.