Continuous Local Anesthesia Aids Postop Pain and Recovery

PARIS, Aug. 24 -- Anesthetic infusion directly into the wound after colorectal cancer surgery may improve pain control and speed recovery, researchers found.

In a small study, patients needed significantly less morphine postop (P=0.0004) when local anesthetic was continuously infused into the surgical wound, said Marc Beaussier, M.D., Ph.D., of St-Antoine University Hospital here, and colleagues.

Furthermore, they reported in the September issue of the journal Anesthesiology, return of bowel function and discharge from the hospital improved by an average of one day (P=0.02).

The new technique, because of "its simplicity may [become] an important instrument in our analgesic armentarium across several major surgical procedures," commented Henrik Kehlet, M.D., of the Juliane Marie Centre in Copenhagen, and Spencer S. Liu, M.D., of the Hospital for Special Surgery and Cornell University in New York, in an accompanying editorial.

Previous studies had shown that the new technique is useful as part of postoperative pain control in cardiac, thoracic, major gynecologic and other types of surgery.

However, little to no benefit was seen after open abdominal surgery, possibly because the catheters were placed subcutaneously, ignoring the fascia of the abdominal muscles and peritoneum, the researchers said.

So, the researchers randomized 42 patients at three hospitals undergoing colorectal cancer resection to receive either the local anesthetic ropivacaine (Naropin 0.2%, 10 ml bolus then 10 ml/h) or placebo through a special multi-holed catheter, placed during the procedure. The catheter ran the full length of the surgical incision and was placed deep in the wound, between the closed peritoneum and the fascia.

Treatment continued for the first 48 hours after surgery. Both groups received patient-controlled intravenous morphine, the standard for postoperative pain.

Immediately after surgery in the post-anesthesia care unit, fewer patients in the ropivacaine group than in the placebo group needed intravenous morphine (15 versus 20), with a significantly lower total dose (4 versus 7 mg, P=0.004).

Over the first three postoperative days, the ropivacaine group also needed significantly lessmorphine (48 mg versus 84, P=0.0004) and had lower pain intensity at rest and during coughing (both P<0.01).

Opioid use was also lower during the day after the catheter was removed, suggesting, the researchers said, that the analgesic effect may outlast the duration of the wound infusion, perhaps by blocking sensitization of spinal dorasal horn neurons.

Fewer patients in the ropivacaine group needed rescue analgesia use over the first two postoperative days, but the difference was not significant.

Morphine side effects were not significantly different between groups, including severe postop nausea and vomiting requiring treatment. No major adverse events occurred, nor were there any effects seen on wound infections or healing.

But there were some significant postoperative recovery advantages to local anesthesia wound infusion. The researchers reported:

• Better sleep quality the first two nights after surgery versus placebo as measured on a visual analog scale (7.9 versus 5.0 cm on night one and 8.6 versus 6.9 cm on night two, both P<0.001).
• Shorter time to recovery of bowel function versus placebo, a key determinant of hospital stay (74 versus 105 h, P=0.02).
• Shorter duration of hospitalization (115 versus 147 h, P=0.02).

Serum ropivacaine levels remained within safe limits throughout the study, the researchers said. After 24 hours of infusion, the highest unbound concentration was 0.12 ?g/ml, which was slightly above the threshold for mild central nervous system toxicity in studies of healthy subjects.

It "suggests a sufficient margin of safety with the use of the studied infusion regimen, but cautions against using higher ropivacaine doses in this setting," they wrote.

Nevertheless, larger studies will be needed to draw definite conclusions about the safety of this technique, they noted. Questions also remain about the choice of local anesthetic, the optimal dose, and whether patient controlled administration would work, they added.

The analgesic technique may not work in patients with a dysfunctioning stoma, or previous abdominal surgery that included peritoneal resection, the investigators said.

But for most patients, it could "be considered as an interesting alternative to epidural analgesia," they concluded.

Comparative studies with epidural analgesia and other local anesthetic techniques are needed to determine differences in technical failures, costs and side effects, Drs. Kehlet and Liu said.