Neuropsychological recovery after midazolam coinduced general anesthesia

INTRODUCTION: Following ambulatory surgery, rapid return of cognitive function is imperative. Data on the recovery of cognitive function after low dose midazolam coinduced general anesthesia is limited. It is unknown if coinduced general anesthesia allows faster return of function due to lower total drug dosages or prolongs cognitive recovery due to benzodiazepine effects. This study uses neuropsychological testing to measure cognitive recovery after midazolam coinduced anesthesia compared to propofol induced controls in ambulatory gynecology patients undergoing short laparoscopic procedures. -- METHODS: With approval of the hospital research ethics board, 88 eligible patients were randomized in a double blind manner into one of two groups; propofol 2mg/kg control (n=44) or midazolam 0.02mglkg with propofol 1 mg/kg coinduced group (n=44). All patients received a standardized general anesthetic including endotracheal intubation. Neuropsychological objective testing consisted of a Digit Symbol Substitution Test (DSST), a Trieger Dot Test (TDT) and five Visual Analogue Scales (VAS) for subjective assessment of anxiety, sedation, coordination, confusion and drowsiness. Tests were completed preoperatively and postoperatively every 30 minutes until discharged. Intraoperative variables (including adverse events, hemodynamics), time to discharge, Post Anesthesia Care Unit (PACU) narcotic and anti-emetic use were recorded. -- RESULTS: At 60 minutes postoperatively, 84 of the 88 subjects had complete data sets. Statistical significance was not reached (all p's >0.05) on tests of postoperative neuropsychological recovery comparing the propofol control group and the midazolam coinduced group. The groups had clinically similar scores on the VAS testing, DSST (51.8+/-12.7 vs. 55.7+/- 10.5 p=O.l2, 95%CI -9.01 to 1.11 to detect a difference of 13.8) and TDT (7.9+/-7.3 vs. 7.1+/- 5.8 p=0.56). The DSST, TDT and VAS data were further analyzed using repeated measures ANCOV A to compare groups over time (with baseline preoperative test scores as covariate) and no significant difference (DSST p = 0.78) was found based upon group randomization. There was no significant difference in intraoperative hemodynamic parameters, the incidence of adverse events (3 (7 .1%) vs. 2(4.8%)); failed induction (5(11.9%) vs. 5(11.9%)); length of PACU stay (1 :31 +/-37 vs. 1:23+/-32 min); PACU morphine (0.13+/-0.10 vs. 0.13+/-0.11mg/kg); ondansetron rescue (13(31 %) vs. 12(28.6%)). There was no intraoperative awareness in either group. -- DISCUSSION: Midazolam in a low dose (0.02mg/kg) used as a component of coinduced general anesthesia for short ambulatory procedures does not appear to alter cognitive recovery as measured by neuropsychological testing compared to standard propofol (2mg/kg) induction. Intraoperative and PACU variables also appear to be similar between techniques. Thus, there is no disadvantage in recovery characteristics nor does there appear to be any advantage or disadvantage with respect to hemodynamic stability, quality of induction or drug cost. Due to rarity of intraoperative recall, we cannot conclude if midazolam is protective