The Effect of Neuromuscular Blockade on the Composite Variability Index (CVI) During Laryngoscopy

This study will randomize patients to one of four doses of rocuronium: no rocuronium, 0.2,
0.4, and 0.6 milligrams per kilo of body weight; the last dose is the standard amount for
adults. It is expected that the group given the highest dose of rocuronium will have
diminished CVI values. By including intermediate doses, information about the function of
CVI in states of less than full muscle relaxation, or paralysis, will be obtained. This
information is critically important for the development of the composite variability index,
because during general anesthesia patients are usually maintained in a state of less than
full paralysis. If the CVI response to stimulation in the intermediate groups is similar to
the group receiving no rocuronium, the monitor may find wide clinical applicability. If the
response is similar to the maximal rocuronium group, the index may only be reliable in
states with no muscle relaxant, which will greatly limit clinical utility.

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.

Inclusion Criteria:

- Presence of ASA physical status class I or II. (This will exclude subjects with
significant medical problems).

- Body mass index between 18 and 35 kg m-2.

- No use of psychotropic or neuropsychiatric medications.

- A airway assessment with no indication of a difficult intubation including a class I
or II Mallampati airway and a mandible-to-hyoid distance of greater than three
fingerbreadths.

- Age between 18-75 years.

Exclusion Criteria:

- Does not meet inclusion criteria.