A Comparison Of Remifentanil EC₅₀ For Mcgrath Video Laryngoscope And Macintosh Laryngoscope

Objective To determine the optimal effect-site concentration of remifentanil required to prevent tracheal intubation response in50%of patients during target-controlled infusion (TCI) of propofol between McGrath video laryngoscope and Macintosh laryngoscopeMethods Sixty ASA Ⅰ or Ⅱ patients undergoing elective surgery were randomly assigned to either the Macintosh or McGrath group (30per group). Anesthesia was conducted by target-controlled infusion of propofol at a target plasma concentration of3μg· ml-1in each group. When an Observers Assessment of Alertness/Sedation (OAA/S) score of1was achieved, intravenous rocuronium0.5mg· kg-1, then remifentanil was infused waiting for the predicted propofol effect-site concentrations arrived at2.4μg· ml-1and bispectral index (BIS) was less than60, then tracheal intubation was performed. Mean arterial blood pressure (MAP), Heart rate (HR) and BIS were recorded before insertion (baseline) and immediately and1min and2min and5min after insertion respectively. The intubation response was graded as successful or failure by the Helbo-Hansen scoring system. Success was defined as:A score of2or less in all five variables by the insertion scoring system and MAP、HR variation<20%of the baseline values within5min after insertion. The next effect-site concentration of remifentanil was given by the modified Dixon’s up-and-down method,the ratio of two concecutive effect-site concentration was1.2. The median effective concentration of remifentanil for tracheal intubation was determined using the probit regression model.Results The media effect-site concentration of remifentanil for tracheal intubation with the McGrath laryngoscope was2.7ng· ml-1(2.4～3.1ng· ml-1;95%confidence interval),and that of the Macintosh laryngoscope was3.0ng/ml(2.5-3.3ng/ml;95%confidence interval). There was no difference in the total intubation scores. No patients showed signs of muscle rigidity. Arterial pressures or heart rate did not differ between the groups.Conclusion During the target-controlled infusion (TCI) of propofol The EC50of effectsite concentration of remifentanil for is2.7ng· ml-1(95%CI2.4-3.1ng/ml) using McGrath videolaryngoscope,while3.0ng/ml(2.5-3.3ng/ml)for Macintosh laryngoscope. We did notdetect any major complications using this technique for either method.