Despite neuromuscular transmission monitoring and pharmacological reversal allowing a train of four ratio recovery higher than 0.9, patients receiving neuromuscular blocking agent during general anesthesia have a high risk of postoperative pulmonary complications. While this train of four ratio threshold is considered as the gold standard to confirm the lack of residual paralysis, tetanus 100 Hz stimulation showed a marked fade. This result has been observed in absence of reversal agent administration.

Therefore, the present study has been designed to compare the recovery of train of four stimulation, tetanus 50 Hz and tetanus 100 Hz stimulation in patient receiving rocuronium during general anesthesia and reversed by an anticholinesterase agent (neostigmine). Neostigmine will be injected once four muscular contractions of the adductor pollicis muscle will be observed after a train of four stimulation, at a dose (40 µg/kg) in accordance with the clinical practice worldwide admitted.

Two questions have to be investigated. First, is this dose of neostigmine sufficient to allow a complete recovery of tetanus stimulations ? Second, due to the pharmacological properties of neostigmine, does a recurarisation phenomenon occur following repeated tetanus stimulations ? The attented results of this study will be to propose a new thinking on what we really need to make relevant progress in the safety aspects of residual paralysis outcome.

Inclusion Criteria:

• ASA clinical status 1 to 3 informed consent obtained before anesthesia induction

Exclusion Criteria:

• ASA clinical status 4 emergency surgery scheduled surgery in prone position hepatic or renal disease BMI higher than 35 allergy to rocuronium or neostigmine