Evaluation of the Most Effective Dose of Remifentanil During Le Fort I Osteotomy

Statement of the problem: Le Fort I osteotomy (L-I) requires extensive dissection and manipulation of tissue which results in hemodynamic instability. High blood pressure during L-I causes adverse effects such as increased blood loss, decreased quality of the operating field, and disturbance of the endocrine immune response (Dolman, JOMS, 2000). Remifentanil is an ultrashort-acting opioid used in anesthesia worldwide. Although remifentanil appears to offer a more superior intraoperative hemodynamic stability during stressful surgical events than fentanyl (Guy, Anesthesiology, 1997), bolus administration of remifentanil produces bradycardia. Few investigations have been conducted regarding hemodynamics during L-I under remifentanil anesthesia. The purpose of this study was to clarify the most effective dose of remifentanil during L-I.

Materials and methods�: Twenty-one orthognathic patients (men 9, women 12) who were classified as ASA physical status I or II at Tokyo Medical University Hospital were enrolled in this randomized controlled double-blind study. The study was approved by the research ethics committee of Tokyo Medical University Hospital. Written informed consent was obtained from all the patients before participating in the study. Oxygen-propofol-remifentanil general anesthesia was administrated to all the patients. The dosage of propofol, obtained from bispectral index value 50 (± 5) was maintained throughout the procedure. Hemodynamics, including invasive arterial blood pressure, was monitored and data were recorded every 5 minutes for data collection. All the patients had a double jaw surgery and L-I was performed before the mandible surgery. All L-I procedures were performed by a single surgeon. Before starting L-I, 3.6 mL of 2% xylocain (including 0.0675 mg of epinephrine/1.8 mL) was injected into predetermined vestibular regions. The patients were randomly assigned to the following 3 groups: Group 1) 0.25 μg/kg/min (n = 7); Group 2) 0.5 μg/kg/min (n = 7); Group 3) 0.75 μg/kg/min (n = 7). The study endpoints were as follows: a) mean arterial blood pressure (MAP); b) systolic blood pressure; c) heart rate (HR). Data were recorded at 3 time intervals: i) before L-I (20-minute period before surgery); ii) during L-I (from the beginning of surgery to the down fracture technique); iii) after L-I (20-minute period after the down fracture technique). Values obtained every 5 minutes were calculated for each group at each time point and averaged. The rates of increase between before L-I and during L-I and between before L-I and after L-I were calculated.

Methods of data analysis: Data were analyzed using one-way analysis of variance (Bonferroni’s Multiple Comparison Test) after Bartlett's test.

Results: One patient was excluded because of endotracheal tube damage which required reintubation. Therefore, data were obtained from 20 patients. The average operating times (minutes) in each group were 53.1, 46.7, and 49, respectively. The rate of MAP increase from before L-I to during L-I in the 0.25 μg/kg/min group was 10.8% (n = 7). The rate of MAP increase from before L-I to during L-I in the 0.75 μg/kg/min group was 2.1% (n = 6). A similar trend was observed from before L-I to after L-I. The 0.75 μg/kg/min group showed a significantly reduced rate of MAP increase “during L-I” and “after L-I” compared with the 0.25 μg/kg/min group (P < 0.05). The rates of increase in HR from before L-I to during L-I and from before L-I to after L-I in the 0.75 μg/kg/min group were -0.8% (n = 6) and -3.4%, respectively. The HRs decreased both from before L-I to during L-I and from before L-I to after L-I in the 0.75 μg/kg/min group; however, these were not statistically significant.

Conclusion: Remifentanil administration at 0.75 μg/kg/min stabilized hemodynamics during L-I without significant side effects.

1. Dolman RM, JOMS, 2000
2. Guy J, Anesthesiology, 1997