The vast majority of patients receive neuromuscular blockers during surgical procedures, either as a single injection to facilitate intubation or as repeated injections to induce muscle relaxation necessary for surgery. The action of neuromuscular blockers is monitored by measuring the contraction force of the adductor of the thumb after stimulation of the ulnar nerve.Different types of stimulation, such as train-of-four (TOF), post- Tetanus count (PTC), double-burst stimulation (DBS) measure different degrees of curarization.The duration of action of neuromuscular blockers has significant interindividual variability. If the investigators know how to measure the degree of curarization of a patient at a given time, it is difficult to know how long it will take to recover neuromuscular function.

The purpose of this study is to determine if the individual recovery of a patient can be predicted form data obtained at the beginning of his/her recovery curve. The investigators propose to record all neuromuscular transmission monitoring data in 100 patients. From these data, the investigators will try to develop an algorithm that would extrapolate the recovery curve of an isolated patient from the fist neuromuscular monitoring data.

Inclusion Criteria:

• Patients undergoing a surgical intervention with rocuronium
• Patients covered by the Belgian social security system

Exclusion Criteria:

• Allergy towards rocuronium
• 20< Body Mass Index <30
• Hepatocellular insufficiency, either clinical or abnormal liver tests
• Renal insufficiency, defined as Modification of diet in renal disease (MDRD) <40ml / min or Cockgroft <50ml / min
• Need to antagonize the curare