The role of continuous background infusions in patient-controlled epidural analgesia for labor and delivery

The use of a background infusion with intravenous patient-controlled analgesia (IV-PCA) increases drug consumption without any additional contribution to analgesia. There are no data on the potential advantage of a background infusion administered with patient-controlled epidural analgesia (PCEA) for labor and delivery. Sixty women were randomized to one of four groups and received either: (a) demand dose PCEA (demand dose = 3 mL; lockout interval = 10 min); (b) continuous infusion plus demand dose PCEA (two separate infusion rates: 3 mL/h and 6 mL/h); or (c) a fixed-rate continuous epidural infusion (CEI) at 12 mL/h. All patients received 0.125% bupivacaine with 2 μg/mL of fentanyl. The study protocol was double-blind and placebo- controlled. Visual analog pain scores, motor strength, and bilateral pinprick analgesia were assessed every half hour by a blinded observer. Pain scores, cephalad extent of sensory analgesia, and motor block were no different among the study groups during the first and second stages of labor. Cumulative hourly bupivacaine use was similar among all PCEA study groups. However, use of PCEA (in whatever mode) provided a 35% dose-sparing effect in comparison to CEI. The PCEA groups receiving no background infusion or a 3-mL/h background infusion had a greater need for physician-administered supplemental bupivacaine during the first stage of labor. While not statistically significant, a trend toward increased need for supplementation was seen in these same patient groups over the entire course of labor and delivery. Patients with a continuous background infusion of 6 mL/h plus demand dose PCEA obligatorily received 33% of their maximum hourly demand dose as a background infusion. The need for physician-administered supplementation was minimal. Yet, pain scores, extent of sensory analgesia, degree of motor block, and cumulative hourly bupivacaine use were equivalent to all other PCEA groups. Thus, administration of a significant but modest proportion (i.e., 33%) of the maximum hourly demand dose as a continuous background infusion is appropriate for PCEA during labor and delivery.