The Effect of Manipulation of the Programmed Intermittent Bolus Time Interval and Injection Volume on Total Drug Use for Labor Epidural Analgesia: A Randomized Controlled Trial

BACKGROUND: Programmed intermittent bolus administration of epidural anesthetic solution compared with continuous infusion results in decreased anesthetic consumption and increased patient satisfaction. In this randomized and blinded study, we evaluated bupivacaine consumption and other analgesic outcomes when the programmed intermittent bolus time interval and volume were manipulated during the maintenance of epidural labor analgesia. METHODS: Healthy, term, nulliparous women in spontaneous labor had combined spinal-epidural labor analgesia initiated with intrathecal bupivacaine 1.25 mg and fentanyl 15 mu g, followed by an epidural test dose (lidocaine 45 mg with epinephrine 15 mu g). Subjects were randomized to 1 of 3 programmed intermittent bolus dose regimens for maintenance of analgesia: 2.5 mL every 15 minutes (2.5/15), 5 mL every 30 minutes (5/30), or 10 mL every 60 minutes (10/60). The maintenance epidural solution consisted of bupivacaine 0.625 mg/mL with fentanyl 1.95 mu g/mL. Breakthrough pain was treated initially with patient-administered epidural bolus doses, followed by manual boluses administered by the anesthesiologist if necessary. The primary outcome was total bupivacaine consumption per hour of labor. A linear mixed-effects model was used to model each patient's overall bupivacaine consumption per hour; the fixed effect was basal bupivacaine administration rate and the random effect was the area under the pain score versus time curve. RESULTS: One hundred ninety women were studied. The median (interquartile range) adjusted bupivacaine consumption per hour of labor was 8.8 mg (8.0-9.7 mg) in group 10/60 compared with 10.0 mg (9.3-10.8 mg) in group 5/30 and 10.4 mg (9.6-11.2 mg) in group 2.5/15 (P = 0.005). There were no differences in area under the pain score versus time curve, pain scores at delivery, patient-controlled epidural analgesia requests or administrations, number of manual bolus doses for breakthrough pain, time to first patient-controlled epidural analgesia or manual bolus dose, or patient satisfaction with labor analgesia. CONCLUSIONS: Extending the programmed intermittent bolus interval and volume from 15 minutes to 60 minutes, and 2.5 mL to 10 mL, respectively, decreased bupivacaine consumption without decreasing patient comfort or satisfaction. (Anesth Analg 2011;112: 904-11)