Obesity in the world represents a growing share of the general population. At hospital, the management of these patients could be problematic especially when calculating the drug dosage.

According to the French guidelines, neostigmine, a cholinesterase inhibitor, should be used to reverse a residual neuromuscular blockade at a dose of 0.4 mg/kg of total body weight in non-obese patients. In morbidly-obese patients, with the modification of the fat/lean mass ratio, the optimal dose of neostigmine is non-consensual. To calculate the dose of neostigmine, some anesthesiologists use the total body weight, others use the ideal body weight and others use the adjusted body weight.

Due to this practice variability, It may be useful to observe the mean time to recovery of neuromuscular blockade and side effects after pharmacological reversal according to the dosage of neostigmine.

Inclusion Criteria*:

• Adult obese patients (≥ 18 years and BMI ≥ 35 Kg/m²), both sexes
• Any elective bariatric surgery
• Neuromuscular blockade with rocuronium
• Maintenance of anesthesia with a halogenated agent
• Free patient, without guardianship or subordination
• Patients with a social security coverage
• No opposition given by the patient after clear and fair information

Exclusion Criteria*:

• Patients with hypersensitivity to the active substance or to other derivatives, or to any of the excipients of neostigmine,
• Emergency surgery,
• Severe renal and / or hepatic insufficiency,
• Persons benefiting from enhanced protection, namely pregnant women, breastfeeding women, persons deprived of their liberty by a judicial or administrative decision, persons staying in a health or social institution, adults under legal protection and finally sick people in emergency situation.

patients whose BMI will be higher than 35 kg/m²