Effects of dexmedetomidine on propofol and remifentanil infusion rates during total intravenous anesthesia for spine surgery in adolescents

INTRODUCTION: Total intravenous anesthesia with propofol and a synthetic opioid is a frequently chosen anesthetic technique for posterior spinal fusion. Despite its utility, adverse effects may occur with high or prolonged propofol dosing regimens including delayed awakening. The current study investigated the propofol-sparing effects of the concomitant administration of the alpha(2)-adrenergic agonist, dexmedetomidine, during spinal fusion surgery in adolescents. METHODS: The surgical database of the department of orthopedic surgery was searched and patients (12-21 years of age) were identified who had undergone spinal fusion for either idiopathic or neuromuscular scoliosis during the past 24 months. Patients were assigned to two groups. Group 1 included patients anesthetized with propofol and remifentanil and group 2 included patients anesthetized with dexmedetomidine, propofol, and remifentanil. In the latter group, dexmedetomidine was administered as a continuous infusion of 0.5 microg.kg(-1).h(-1) started after the induction of anesthesia without a loading dose. Propofol was adjusted to maintain the bispectral index (BIS) number at 40-50 and remifentanil was adjusted to maintain the mean arterial pressure (MAP) at 50-65 mmHg. Labetolol or hydralazine was used if the MAP could not be maintained at 50-65 mmHg with remifentanil up to a maximum dose of 0.6 microg/kg/min. Statistical analysis included a nonpaired t-test for parametric data (age, weight, remifentanil/propofol infusion requirements, and heart rate/blood pressure values). A nonparametric statistical analysis (Dunn) was used to compare BIS numbers. Parametric data are presented as the mean +/- SD while nonparametric data are presented as the median and the 95th percentile confidence intervals. RESULTS: Twelve patients received propofol-remifentanil-dexmedetomidine and 24 received propofol-remifentanil. There were no differences in the demographic data, BIS numbers or hemodynamic parameters between the two groups. There was a reduction in the propofol infusion requirements in patients who also received dexmedetomidine (71 +/- 11 microg.kg(-1).min(-1)) compared with those receiving only propofol-remifentanil (101 +/- 33 microg.kg(-1).min(-1), P = 0.0045). No difference was noted in the remifentanil infusion requirements or the use of supplemental agents (hydralazine and labetolol) to maintain controlled hypotension. CONCLUSION: The concomitant use of dexmedetomidine in patients undergoing spinal fusion reduces propofol infusion requirements when compared with those patients receiving only propofol and remifentanil.