39 Impact of timing of preoperative gabapentin administration on postoperative somnolence

Abstract

Preoperative gabapentin administration decreases postoperative pain, but is associated with increased risk of prolonged postoperative somnolence and respiratory depression. This study aims to assess the optimal preoperative timing for gabapentin administration in patients undergoing gynecologic surgery to minimize risk of prolonged postoperative somnolence. A retrospective cohort study evaluated patients who underwent gynecologic surgery and received preoperative gabapentin. Patients were grouped based on timing from gabapentin administration to surgical incision (less than 4 hours vs. greater than or equal to 4 hours). Preoperative, intraoperative, and postoperative data was abstracted and compared. A total of 225 patients were included. Gabapentin was administered less than 4 hours prior to skin incision for 127 patients (group 1) and greater than or equal to 4 hours in 98 patients (group 2). Demographics were similar between the groups with the exception of chronic pain (group 1 = 17.6%; group 2 = 34.7%; P value 0.005) and surgical indication (group 1 = pelvic pain (29.1%); group 2 = pelvic pain (55.1%); P value < 0.001). Surgical approach was minimally invasive in 95.3% of patients in group 1 and 91.8% of patients in group 2. Hysterectomy was the most frequent procedure(group 1 = 50.4%; group 2 = 54.1%), followed by excision of endometriosis (group 1 = 27.6%; group 2 = 43.9%).Narcotic administration preoperatively (P value 0.35) and intraoperatively (P value 0.50) were similar between the two groups, while group 1 had a lower postoperative narcotic administration (group 1 median morphine milligram equivalents (MME) = 0.019; group 2 median MME = 7.50; P value < 0.001).The minutes from surgical closure until time the patient received a Richmond Agitation Sedation Scale (RASS) score of 0 and initial Post-Anesthesia Care Unit (PACU) pain score (VAS) were similar for both groups (P value = 0.46 and P value = 0.40, respectively). Initial PACU oxygen administration volume (P value = 0.26), hours from surgical closure until patient transitioned to room air (P value = 0.82), and initial PACU respiratory rate (P value = 0.92) were similar between both groups. PACU stay duration (P value = 0.45), unplanned admission secondary to excessive somnolence (P value = 0.58), and the initial PACU Glasgow Coma Scale (GCS) score (P value = 0.85) showed no statistically significant difference. Administration of gabapentin less than or greater than 4 hours preoperatively does not significantly affect postoperative somnolence or respiratory depression. However, administration of gabapentin within 4 hours of first incision was associated with less postoperative narcotic administration, suggesting that the analgesic effects of gabapentin are more effective when given within 4 hours of surgery.