Factors that influence pain intensity and fentanyl requirements after a gynecologic laparotomy

The association between pain intensity and its control by intravenous patient-controlled analgesia (IV-PCA) with fentanyl after a laparotomy for cystectomy/salphingoophorectomy, myomectomy, or hysterectomy was investigated. IV fentanyl infusion was administered to patients (n = 94) at 3 μg/kg/h to provide intraoperative analgesia after induction of general anesthesia. Postoperative fentanyl requirements were quantified via IV-PCA, and the amounts of rescue fentanyl required both during and after surgery were recorded. Mean values for PCA use as well as the visual analog scores (VAS) for pain were documented for up to 24 hours. The association between postoperative fentanyl requirements and VAS were then analyzed by using Mann-Whitney or Kruskal-Wallis tests. Patients with lower midline incisions had greater degrees of pain (p < .05) during the first 16 hours after surgery but did not consume more fentanyl compared with patients with Pfannenstiel incisions. Subjects who underwent operations lasting >4 hours required more rescue fentanyl during surgery (p < .05). However, this group consumed less fentanyl during the first 4 hours after surgery (p < .05). The demand at the fourth 4-hour period was lower among subjects undergoing myomectomy compared with cystectomy/salphingoophorectomy or hysterectomy (p = .045). Only a poor correlation was observed between pain intensity and analgesic usage. Postoperative pain intensity is influenced by the type of surgical incision but not the type of gynecologic surgery nor the duration of surgery. The relationship between subjective pain ratings with analgesic consumption is weak. Prolonged intraoperative administration of continuous IV fentanyl infusion may reduce fentanyl requirements in the immediate postoperative period.