Abstract
We prospectively studied the effects of intermittent (n=13) and continuous (n=7) femoral nerve blocks on postoperative pain after total knee arthroplasty. All patients were managed with general anesthesia. An indwelling catheter for femoral nerve block was inserted under ultrasound echography with the aid of electrical nerve stimulation, after completion of the surgery. After bolus injection of 0.3% ropivacaine 20 ml, 13 patients received 0.2% ropivacaine 4 ml every hour (intermittent group), and 7 received 0.2% ropivacaine at a rate of 4 ml/hour (continuous group). Patients were given pentazocine 15 mg when pain occurred. Postoperative pain was assessed with a numerical rating scale (NRS), number of pentazocine injections, range of passive movement of the knee joint, and satisfaction of patients. Pain intensity, range of passive knee-joint movement, and satisfaction did not differ among the groups. The intermittent group received significantly less pentazocine than the continuous group did on the next day after surgery. The frequency of patients unsatisfied with pain treatment was 50% for the intermittent group and 29% in the continuous group. We conclude that because neither intermittent nor continuous femoral nerve block give sufficient pain relief for total knee arthroplasty, other methods of pain treatment should be studied.
