Aim: To optimize the use of rocuronium (a neuromuscular blocking agent) in obese patients undergoing gastric bypass or gastric banding.

Background: During general anaesthesia, a neuromuscular blocking agent is needed to allow surgery and airway management. Optimal dosing is important in order to avoid inadequately muscle relaxation, but also to avoid overdosage, which can result in prolonged anaesthesia and respiratory complications.

Main hypothesis: Rocuronium dosed according to ideal body weight results in shorter duration of action compared to rocuronium dosed according to corrected body weight without prolonged onset time or compromised airway management or surgical demands for muscle relaxation.

Inclusion Criteria:

• Age 18-65 years.
• Elective laparoscopic gastric banding or gastric bypass.

Exclusion Criteria:

• Expected difficult endotracheal intubation based on anatomic or pathologic findings or history.
• Known or suspected neuromuscular disease, known to affect the neuromuscular blockade.
• Severely impaired renal or hepatic function, as evaluated by the investigator.
• Known or suspected allergy to drugs used in the trial.
• Daily or expected use during the trial of the following drugs, known to affect neuromuscular transmission: Inhalational anaesthetics, magnesiumsalts, clindamycin, polymyxins and aminoglycosides (gentamicin, neomycin, netilmicin, streptomycin og tobramycin).