January 2001
PART ONE OF A TWO-PART SERIES ON MULTI-MODAL ANALGESIA AFTER LAPAROSCOPIC SURGERY

Goldstein A, Grimault P, Henique A, Keller M, Fortin A, Darai E.
Anesth Analg 2000;91:403-7

Commentary by Beverly Philip, M.D.

Preventing Postoperative Pain by Local Anesthetic Instillation After Laparoscopic Gynecologic Surgery: A Placebo-Controlled Comparison of Bupivacaine and Ropivacaine

There are several components of pain after laparoscopic gynecological surgery. Scapular pain secondary to peritoneal insufflation occurs especially when an exaggerated Trendelenburg position is used. In addition, there is visceral pain, and pain caused by pelvic inflammation and traction on uterus and tubes. These multiple causes suggest that a multimodal approach to analgesic therapy may be highly effective. Local anesthetic infiltration has been shown to attenuate postoperative pain after laparoscopic cholecystectomy. However, there have been only a few reports on the efficacy of intraperitoneal local anesthetic administration for pain relief after laparoscopic gynecologic surgery, and bupivacaine has been the local anesthetic agent most often used. The newer local anesthetic agent, ropivacaine, is less cardiotoxic and hence can be administered in larger doses. The authors undertook a study comparing ropivacaine (150 mg) with bupivacaine (100 mg) and with placebo. This was a prospective, double-blind randomized placebo-controlled study. Its objective was to assess whether intraperitoneal instillation of local anesthetics can decrease postoperative pain and delay its appearance. The authors also sought to compare the efficacy of bupivacaine and ropivacaine as local anesthetics.

One hundred eighty adult ASA I - II patients undergoing operative gynecologic laparoscopy were enrolled. The specific surgical procedures included ovarian and tubal procedures, laparoscopic-assisted vaginal hysterectomy, lysis of adhesions, and myomectomy; the procedures were evenly distributed among the three treatment groups. In France where this study was performed, these are all in-patient procedures. Patients received premedication with either hydroxyzine or midazolam. General anesthesia was induced with 20-30ug sufentanil and propofol. Muscle relaxation was provided with vecuronium or cisatracurium. The block was monitored, and neuromuscular block reversing agents were not given. Controlled ventilation was maintained with 50% oxygen/nitrous oxide with 1-1.2 MAC desflurane or 0.8-1 MAC sevoflurane. Sufentanil injections were administered if perioperative analgesia was insufficient, 10-20 ug/hour.

Patients were randomly allocated to receive either bupivacaine 0.5% with epinephrine- 100 mg [B], ropivacaine 0.75%- 120 mg [R], or 0.9% sodium chloride [S]. A 20 ml syringe containing 20 ml of the solution was prepared by a nurse who was blinded to the study, as were the surgeons, PACU nurses and ward nurses. All patients had the instillation of 20 ml of the solution in a standardized manner by the operating surgeon, under visual control at the end of the surgical procedure: 7 ml under each sub-diaphragmatic area and 6 ml at the surgical site (in case of a bilateral procedure: 5+5+5+5 ml). The standard postoperative analgesia regimen used at that hospital included the administration of acetaminophen, NSAIDs, and morphine. An infusion of acetaminophen (2 g propacetamol) and 100 mg ketoprofen was started 30-60 min before end of surgery and given every 6 hours for 24 hours. In the PACU, pain was evaluated every 5 minutes using a numeric scale 0 —10, which had been explained to the patients during the pre-anesthetic visit. In case of pain >4 using the numeric scale, 2 mg boluses of IV morphine were injected and repeated every 5 minutes until a pain score of <4 was obtained. To prevent PONV, 1 mg droperidol was administered. This could be repeated once and also 4 mg ondansetron given in case of nausea. Pain assessment using the same scale was done every 4 hours by the nursing staff on the ward. The dose and frequency of morphine administration was recorded.

The efficacy of local anesthetic instillation was determined for two endpoints- the dose of morphine required at the wake-up from anesthesia, and the dose of morphine required to provide and maintain analgesia (<4) during the first 24 postoperative hours. Parenteral analgesia was administered for 24 hours on the ward, after which the patients received oral nonopioid analgesics on request. PONV was rated by the nurse on a four-point scale, where zero equaled no PONV, one equaled only nausea, two equaled mild vomiting, successfully treated by droperidol, and 3 equaled "heavy vomiting" requiring other treatments in addition to droperidol.

The results showed significant differences between the two groups who received local anesthetics and the one group that did not. The morphine dose required to obtain a pain score of <4 at wake-up was significantly smaller in Groups B and R than in Group S. The morphine consumption in Group R was also significantly less than in Group B. The consumption of subcutaneous morphine during the first 24 hours in the ward was significantly less in Groups B and R than in Group S. The 24-hour morphine consumption in Group R was also significantly less than Group B.

Both local anesthetics were effective in the prevention of PONV with statistically significant differences for all levels of PONV compared with saline. There was no significant difference between groups B and R. Antiemetic treatment of symptoms was required for only 10% in Group B and 15% in Group R, but for 43% of patients in Group S. No adverse side effects were observed in any of the groups.

It should be noted that the incidence of PONV in the study overall is fairly high. This may be related to use of relatively large doses of sufentanil for induction and possibly also for maintenance (although the total sufentanil dose used was not reported). Furthermore, the postoperative administration of morphine may have added to PONV. Also, remember that the patients in the study were inpatients, and the incidence of PONV would be expected to be [even] higher with patients who are ambulated postop.

In summary, both bupivacaine and ropivacaine were effective at reducing pain and PONV when instilled intraperitoneally at the end of laparoscopy at wake-up and for the first 24-hours postop. The study also showed that 150 mg ropivacaine significantly reduced the need for morphine compared with 100 mg bupivacaine.