Changes in sensory block level during a programmed intermittent epidural bolus regimen for labour analgesia: a prospective observational cohort study.

Abstract

In the context of a programmed intermittent epidural bolus (PIEB) regimen for labour analgesia, one can identify an upper sensory block level (USBL), defined as the highest dermatome with any altered sensation to cold, and a lower sensory block level (LSBL), defined as the highest dermatome with complete sensory block to cold. This study investigated whether and how these sensory block levels vary within PIEB cycles. We enrolled patients requesting epidural analgesia. An epidural catheter was placed at L2/L3 or L3/L4. A test dose of 3mL of bupivacaine 0.125% with fentanyl 3.3µg·mL-1 was administered, followed by 12mL of the same solution as the loading dose. A PIEB plus patient-controlled epidural analgesia (PCEA) regimen was initiated 40min after the loading dose, with bupivacaine 0.0625% with fentanyl 2µg·mL-1: PIEB 10mL, PIEB interval 40min, PCEA 5mL, lockout interval 10min, maximum hourly 30mL. As per institutional protocol, sensory block levels to ice were assessed 20min after the loading dose and then hourly. Patients included in the study underwent eight extra assessments: immediately before the second and fourth PIEB and 10, 20, and 30min after the second and third PIEB. We studied 30 patients. The USBL and LSBL achieved their peak value 100min after the loading dose. The median [interquartile range] USBL was T8 [T9-T7] and T6 [T7-T4] 20 and 100min after the loading dose, respectively; LSBL was T10 [T11-T6] and T8 [T9-T6], respectively. There was no significant variation in USBL or LSBL within the PIEB cycle between the second and the third or the third and the fourth PIEB. Once peak sensory block levels are established, there is no significant variation in the USBL and LSBL within the PIEB cycles. www. gov (NCT04716660); registered 21 January 2021.