The Effect of Rocuronium on the Response of Composite Variability Index (CVI) to Laryngoscopy

Eighty subjects will be recruited from those scheduled for surgery requiring general anesthesia at St Vincent's Hospital. Subjects must have American Society of Anesthesiologists (ASA) status of 1 or 2 (be fairly healthy), a BMI between 18-35 (reasonably healthy weight), and be between the ages of 18 and 75. They will not be eligible if they take certain medications or are expected to have a difficult intubation.

Subjects will be randomized (assigned by chance) to one of four rocuronium doses of 0, 0.2, 0.4, or 0.6 mg kg-1. All are acceptable clinical doses for performing a laryngoscopy. In the operating room, routine monitors will be applied, including a Bispectral Index (BIS) sensor and an M-Entropy sensor. Subjects will receive 0.025 mg kg-1 midazolam (a standard pre-op dose) and will be put to sleep. Once asleep, the subject will receive a rocuronium dose, followed by laryngoscopy three minutes later. The anesthesiologist performing the laryngoscopy will not know what dose of rocuronium the subject received. CVI, entropy, amount of muscle relaxation, and vital signs will be monitored and recorded throughout the procedure.

Subjects will receive propofol and remifentanil infusions during the case. These are commonly used medications for anesthesia. The subjects will also be randomized to two additional groups. One group will receive a remifentanil infusion of 2ng ml-1 and the other group will receive a 8ng ml-1 remifentanil infusion. Both doses are acceptable and often used during standard clinical care. The propofol infusion will be adjusted to keep the BIS number between 45-60. The anesthesiologist will not be able to see the CVI value. The times of certain intraoperative events, such as intubation and incision, will be recorded. All subjects will receive a morphine bolus (0.10-0.15 mg/kg) towards the end to reduce post-operative pain, as per standard clinical care. As the subject wakes up, time to eye opening and orientation will be recorded. The subject will rate their pain on a numerical pain scale and the quality of emergence will be assessed.

Upon arrival in the post anesthesia care unit (PACU), subjects will be asked to rate their pain again using the same pain scale. The pain score will be evaluated every 10 minutes for half an hour, then every hour until they are discharged from PACU.