Local anesthetic reduced morphine use in study

OB/GYN News, July 15, 2002 by Sherry Boschert

The 20 women who received an infusion of 0.25% bupivacaine rated their pain in the days after C-section at essentially the same levels reported by the 16 women who had an infusion of normal saline.

LOS ANGELES -- Women given continuous infusion of a local anesthetic in their cesarean section incisions used 40% less morphine in the first 48 hours after surgery in a small randomized, prospective, placebo-controlled trial.

All patients received morphine postoperatively through patient-controlled anesthesia, but those in the bupivacaine group required less morphine, Dr. Vanessa A. Givens said at the annual meeting of the American College of Obstetricians and Gynecologists.

By relieving pain through infusion of a local anesthetic and reducing the use of morphine, women may avoid some of the side effects of narcotics such as nausea and drowsiness and be better able to immediately begin bonding with their babies, Dr. Givens suggested at the meeting.

The patients were blinded to the treatment received. Mean pain scores reported by both groups on the 0-10 visual analog scale were 4 at both 12 hours and 24 hours and 2 at 48 hours. A visual analog scale score of 3 or less is considered adequate pain relief, said Dr. Givens of the University of Tennessee, Memphis.

By 12 hours after C-section, women in the bupivacaine group used less morphine than those in the control group (26 mg vs. 43 mg). Women also used less morphine at 24 hours (47 mg vs. 79 mg) and 48 hours (73 mg vs. 128 mg).

In the study, the ON-Q postoperative pain relief system, manufactured by the I-Flow Corporation, Lake Forest, Calif., was used to deliver the C-section infusions.

A small pump that can be carried, attached to a patient's clothing or taped to skin acts as a reservoir for the local anesthetic to be delivered to the incision at a rate of 4 cc/hour through two perforated infusion catheters placed in the incision before closing.

Before closure patients also received an additional 25 cc of bupivacaine or saline injected into the subcutaneous space.

The ON-Q device has been approved by the Food and Drug Administration, and more than 30 studies are underway to document its effectiveness in controlling pain after a variety of surgeries, including hysterectomy The devices were supplied free to the researchers by Ethicon EndoSurgery which was marketing the ON-Q system at the time of the study.

All patients received epidural anesthesia and delivered by planned Pfannenstiel incision. The study excluded patients with signs of infection or hemolysis, elevated liver enzymes, and low platelet count syndrome; drains placed intraoperatively; or laboratory evidence of coagulopathy.

The etiology of postcesarean pain is both uterine and incisional, although it has been unclear how much each contributes. The results suggest that a significant amount of pain following C-section is superficial in origin, Dr. Givens said.