Programmed Intermittent Epidural Boluses (PIEB) for Maintenance of Labor Analgesia: A Superior Technique to Continuous Epidural Infusion?

Continuous epidural infusions (CEI) of local anesthetics with patient-controlled epidural analgesia (PCEA) is the most popular method of maintaining epidural labor analgesia in the United States (1).However, over a decade ago, evidence began to emerge showing that epidural pumps programmed to deliver intermittent epidural boluses (PIEB) of local anesthetic provide more effective analgesia that CEI (2-4).The suggested mechanism of superior epidural analgesia with PIEB compared to CEI is greater spread of anesthetic solution within the epidural space, and therefore better sensory blockade compared to CEI.These clinical observations are consistent findings of more uniform spread with large volumes and correspondingly high injectate pressures in cadavers (5), and observations of greater dye solution spread in semi-absorbent paper with boluses compared to continuously infused solution (despite the same hourly volume being administered) (6).The importance of bolus administration of epidural local anesthetics with or without opioids may also explain why PCEA compared to CEI reduces the need for manual clinician boluses for breakthrough pain, and decreased amount of local anesthetic used (7), and why PIEB regimes with larger boluses and longer lockouts (10 mL every 60 min) are more effective than smaller boluses and shorter lockouts (2.5 mL every 15 min) (8).