Background: Continuous femoral nerve blockade (CFNB) is often used for postoperative analgesia after total knee arthroplasty (TKA). CFNB can be instituted using a variety of techniques. Stimulating catheters (SC) have the advantage of confirming placement of the catheter close to the nerve during advancement.
Methods: In this randomized, controlled, double-blind trial, we compared a SC with a nonstimulating catheter (NSC) technique for institution of CFNB and its effects on quality of analgesia after TKA performed under general anesthesia in 82 patients. Patients were randomized to have CFNB instituted using either a NSC or a SC technique. Sensory blockade was assessed 10 and 20 min after injection of lidocaine via femoral catheter and on postoperative days 1 (POD 1) and 2 (POD 2). A standardized multimodal analgesic technique, including a single injection sciatic block (preoperative), i.v. morphine (patient-controlled analgesia), celecoxib, and paracetamol, was administered to all patients. Outcome variables included morphine requirements, pain scores, and markers of early recovery.
Results: The proportion of patients with sensory blockade in the femoral nerve distribution was between 90% and 95% at all measurement times with no difference between groups. In the first 24 h, the NSC group required 19.5 (1-67) [median (10th-90th centiles)] mg morphine compared with the SC Group 18 (2-51) mg (P = 0.69). At 24 h, the 95% confidence interval for difference in morphine consumption between groups was -8 to 5 mg. There was no difference between groups in visual analog scale scores at rest on POD 1 and POD 2, during active and passive physiotherapy; and in markers of early recovery after surgery.
Conclusions: In this study, blind catheter advancement was as reliable as a SC technique for establishing and maintaining CFNB for postoperative analgesia as a part of multimodal analgesia technique after TKA.