Popliteal sciatic perineural local anesthetic infusion: a comparison of three dosing regimens for postoperative analgesia.

BACKGROUND This randomized, double-blind study investigated the efficacy of continuous and patient-controlled ropivacaine infusion via a popliteal sciatic perineural catheter in ambulatory patients undergoing moderately painful orthopedic surgery of the foot or ankle. METHODS Preoperatively, patients (n = 30) received a posterior popliteal sciatic perineural catheter and nerve block. Postoperatively, patients were discharged home with a portable infusion pump delivering 0.2% ropivacaine (500 ml) in one of three dosing regimens: the basal group (12-ml/h basal rate, 0.05-ml patient-controlled bolus dose), the basal-bolus group (8-ml/h basal rate, 4-ml bolus dose), or the bolus group (0.3-ml/h basal rate, 9.9-ml bolus dose). RESULTS The bolus group experienced an increase in baseline pain, breakthrough pain incidence and intensity, and sleep disturbances compared with the other two groups (P < 0.05 for all comparisons). Compared with the basal-bolus group, the basal group experienced an increase in these outcome measures only after local anesthetic reservoir exhaustion, which occurred earlier than in the other two groups (P < 0.05 for all comparisons). Satisfaction scores did not differ among the three groups. CONCLUSIONS This study demonstrates that when providing analgesia with 0.2% ropivacaine via a popliteal sciatic perineural catheter after moderately painful surgery of the foot or ankle, a continuous infusion is required to optimize infusion benefits. Furthermore, adding patient-controlled bolus doses allows for a lower continuous basal rate and decreased local anesthetic consumption and thereby increases the duration of infusion benefits when in an ambulatory environment with a limited local anesthetic reservoir.