Less pain with femoral nerve block catheters after ACL reconstruction

Catheters also potentially minimize the need for opioid analgesics during postop period.

Using femoral nerve block catheters after ACL reconstruction maintains postoperative pain below the moderate-to-severe threshold for up to four days, according to a recent study.

Brian Williams, MD, and colleagues at the University of Pittsburgh Medical Center conducted the prospective trial. The researchers recruited 270 patients between July 2001 and January 2005; 235 patients completed final follow-up. All patients received standardized spinal anesthesia, intravenous sedation and perioperative multimodal analgesia, and were discharged the day of surgery, according to the study.

The researchers randomly assigned patients to one of three postoperative treatment groups, all of which involved drug infusion through a femoral nerve catheter, as follows:

Placebo group: 30 ml saline bolus plus saline infusion (270 ml at 5ml/hour);
Group I (SbSi): levobupivacaine (0.25%) bolus with saline infusion; and
Group II (LbLi): levobupivacaine (0.25%) bolus and infusion.

Researchers evaluated patients preoperatively and on days one through four and on day seven postoperatively to determine numeric rating scale (NRS) pain scores. They set the moderate-to-severe pain threshold at a score of 5 or above, according to the study.

Higher pain scores in placebo group

Williams and colleagues found that patients treated with local anesthetic administered through a perineural femoral catheter had NRS pain scores below 5 during the first four days following surgery. In contrast, patients who received infusions of normal saline reported higher pain scores, according to the study.

“Routine use of the perineural femoral catheter technique applied routinely to patients undergoing this surgery makes a significant advance in providing sustained analgesia on an outpatient basis, while potentially minimizing the need for opioid analgesics throughout the postoperative course,” the authors said in the study, published in Anesthesiology.

On postop days one and two, 50% of placebo-treated patients had NRS scores of 5 or above, but only 25% of Group II patients posted such scores (P<.001). Patients in Group II had a median pain score of 2, compared with a median score of 4 for placebo-treated patients, according to the study.

On the first postop day, Group I had a median NRS score of 3, which was significantly lower than the placebo group. However, beyond postop day one, there were no pain score differences between these two groups, the authors noted. “This finding is consistent with the anticipated effect once the initial bolus wore off,” they said.

Patients in Group II experienced significant improvements in NRS pain scores, having a median NRS score of 2 on postop days three and four, compared to placebo patients (P=.043) and patients in Group I (P=.018) combined. Both placebo patients in Group I patients had a median NRS pain score of 3, according to the study.

No difference at one week

For Group I, LbLi treatment only predicted lower NRS pain scores on postop days one through four. On day seven, researchers found no significant differences among the three treatment groups.

No differences were found between the three study groups in their need for immediate postoperative opioids. But the researchers did find that more patients with active femoral nerve block bolus treatments — 79% of Group I and Group II — did not require opioids during their in-hospital stay, while 69% of SbSi placebo patients required such opioids (P=.078).

“Use of multimodal techniques for analgesia after knee surgery leads to significant reductions in pain during the first four days after surgery, as well as the potential for reduced chronic pain risks up to one year after surgery,” the authors said.

For more information:
Williams B, Kentor M, Vogt M, et al. Reduction of verbal pain scores after anterior cruciate ligament reconstruction within 2-day continuous femoral nerve block. Anesthesiology. 2006;104:315-327.