Chang Kil Park

Optimizing dose infusion of 0.125% bupivacaine for continuous femoral nerve block after total knee replacement

Background The optimal dose infusion of 0.125% bupivacaine via a femoral catheter after total knee replacement (TKR) has not been defined. This study examined various dose infusions of bupivacaine to determine the analgesic quality in patients receiving a continuous femoral nerve block (CFNB). Methods Patients were randomized to receive a single-injection femoral nerve block (SFNB) or CFNB performed with 20 ml of 0.125% bupivacaine, followed by a continuous infusion of 0.125% bupivacaine in four groups (n = 20 per group): 1) 0 ml/h (SFNB), 2) 2 ml/h, 3) 4 ml/h, and 4) 6 ml/h. The pain intensity at rest and on knee movement was assessed using a visual analog scale (VAS) for the first 2 postoperative days. The cumulative bolus use of IV patientcontrolled analgesia (PCA) with a morphine-ketorolac combination was evaluated. Results A lower cumulative bolus of IV PCA was noted in all CFNB groups compared to SFNB on postoperative days (PODs) 1 and 2, respectively (P < 0.05). Lower VAS scores at rest were observed in the 4 ml/h and 6 ml/h groups than in the SFNB group on PODs 1 and 2, respectively, but only on POD 2 in the 2 ml/h group (P < 0.05). Lower VAS scores on movement were noted in the 4 ml/h than the SFNB group on PODs 1 and 2, but only on POD 1 in 6 ml/h (P < 0.05). Conclusions The minimum effective infusion rate of 0.125% bupivacaine for CFNB after TKR appears to be 4 ml/h according to the VAS pain scores.

Optimizing the dose of intrathecal morphine when combined with continuous 3-in-1 nerve block after total knee replacement

BACKGROUND Continuous femoral 3-in-1 block alone is insufficient for the treatment of severe pain after total knee replacement (TKR). Intrathecal (IT) morphine provides effective postoperative analgesia but may result in many side effects. The optimal dose of spinal morphine when combined with continuous 3-in-1 block after TKR is not known. METHODS Patients were randomized to receive IT morphine in five groups (n = 20 per group): 1) 0.0 mg, 2) 0.05 mg, 3) 0.1 mg, 4) 0.15 mg, and 5) 0.2 mg. All patients received continuous 3-in-1 block performed with 20 ml of 0.25% bupivacaine, followed by a continuous infusion of 0.125% bupivacaine at the rate of 2 ml/h plus PCA boluses of 1 ml with a lockout of 10 minutes. The intensity of pain at rest and on movement of the knee was assessed by using a visual analog scale for the first two postoperative days. RESULTS All treatment groups produced effective pain relief and decreased cumulative femoral PCA bolus use of 0.125% bupivacaine compared with control, respectively (P < 0.05); however, there were no significant differences among the treatment groups. The incidence of vomiting was significantly more frequent with 0.1-0.2 mg IT morphine groups compared with control, respectively (P < 0.05). The rate of administration of antipruritic medication was increased as IT morphine dose increased (P < 0.05). CONCLUSIONS Use of 0.05 mg IT morphine would appear to provide the optimal balance between pain relief and adverse effects following TKR.