Epidural versus femoral nerve sheath catheter for postoperative analgesia following total knee arthroplasty

Intrpduction. Postoperative pain following total knee arthroplasty is a major concern among the anesthesia and orthopedic services (1). The search continues for superior methods in postoperative analgesic regimens with diminished side effects (1,3). Epidural catheter and femoral nerve sheath catheter infusions have been shown to be effective methods for postoperative analgesia (1,2,3,4). No effort has been made to compare the effectiveness of continuous epidural analgesia to that of continuous femoral nerve sheath analgesia. We reported here results comparing femoral nerve sheath catheter infusions versus epidural catheter infusions for postoperative analgesia following unilateral total knee arthroplasty. Methods. This randomized, double blinded study was approved by the Internal Review Board of Pennsylvania Hospital. After informed consent, 17 patients were randomized to two groups. Surgical arthroplasty was performed under spinal anesthesia with conscious sedation. Each patient in both groups received an epidural catheter prior to the delivery of the spinal anesthetic, and a femoral nerve sheath catheter immediately postoperatively. In group one (n=9), postoperative analgesia was accomplished with a standard infusion of-bupivicaine 0.125% and fentanyl 2.5 ug/cc, at a rate of 12 cc/hr. Group one patients also received a femoral nerve sheath placebo infusion of 0.9% normal saline. In group two (n=8), the postoperative analgesia was accomplished with a femoral nerve sheath catheter infusion of 0.25% bupivicaine at 12 cc/hr, while the epidural catheter received a placebo infusion of 0.9% normal saline. Results. Pain scores using a visual analogue scale were lower for group 2 patients but not to a level of statistical significance (p>0.1). Two patients were excluded and one patient was terminated early. One group 1 patient developed bilateral motor blockade, while two group 1 patients experienced unilateral motor blockade. Only one group 2 patient developed unilateral motor blockade. Nausea and emesis scores were minimal for both groups. Sedation scores were also similar for both groups. Discussion. The use of continuous femoral nerve sheath catheter infusions and epidural infusions appears to be a safe and efficacious method of analgesia following total knee arthroplasty. At this point in our data collection statistical significance has not proven either method to be superior in providing analgesia postoperatively. Our clinical data, however, appears to support the superiority of femoral nerve sheath catheters in providing analgesia with a decreased incidence of side effects.