Programmed intermittent epidural bolus for labor analgesia during first stage of labor: a biased-coin up and down sequential allocation trial to determine the optimum interval time between boluses of a fixed volume of 5ml of bupivacaine 0.125% plus fentan
Abstract Number: O-01
Abstract Type: Original Research
Background: Programmed Intermittent Epidural Bolus (PIEB) analgesia has been shown to be superior to Continuous Epidural Analgesia (CEI) (1). While PIEB regimens with bupivacaine 0.0625% with fentanyl produce highly effective analgesia, sensory block levels may be unnecessarily high (2). It is unknown whether regimens administering higher concentration and smaller volume of bupivacaine will result in lower levels of sensory block while maintaining the same quality of analgesia. We conducted a study to establish the optimal time interval between boluses of 5ml of bupivacaine 0.125% plus fentanyl 2mcg/ml to produce analgesia in 90% of women during first stage of labor without breakthrough pain.
Methods: This was a double-blind sequential allocation trial with a biased-coin up and down design to determine the effective interval 90% (EI90) for the PIEB regimen. We recruited nulliparous women requesting epidural analgesia. Epidural catheter placement was performed with the assistance of ultrasound at L2/L3 or L3/L4. A multi-orifice epidural catheter was inserted 5 cm into the epidural space. A 3mL test dose of bupivacaine 0.125% plus fentanyl 3.3 mcg/ml was followed by a loading dose of 12ml of the same solution. After 20 minutes, in those whose pain scores achieved Verbal Numerical Rating Scores ≤ 1/10, the PIEB regimen was set to start one hour after the loading dose. The PIEB bolus dose was fixed at 5 ml of bupivacaine 0.125% plus fentanyl 2mcg/ml. The PIEB interval for the first patient was 60 minutes. The PIEB interval for subsequent patients was set at varying time intervals (60, 50, 40 and 30 minutes) according to the biased-coin design. The PIEB regimen included a PCEA of 5 ml with a lockout of 10 minutes. The primary outcome was effective analgesia, defined as no requirement for PCEA or MD administered bolus for 6 hours after the initiation of PIEB, or until the patient presented full cervical dilatation, whichever occurred first. Pain scores, sensory block levels to ice and pinprick, degree of motor block and non-invasive blood pressure were recorded every hour.
Results: We studied 40 patients. The EI90 was 36.5 minutes (95%CI 34.0, 39.0) using the truncated Dixon and Mood method and 34.2 minutes (95%CI 30.8, 41.5) using Isotonic Regression analysis. Overall, sensory block was above T6 in 20/40 women when assessed by ice and in 10/34 women when assessed by pinprick. Overall, 34/40 women exhibited no motor block. No patient required treatment for hypotension.
Discussion: The optimal time interval between programmed intermittent boluses of 5 mL of bupivacaine 0.125% with fentanyl 2 mcg/mL is approximately 35 minutes. A significant number of women will exhibit sensory block above T6 to ice. Our results suggest no advantage of this regimen over regimens utilizing larger volumes of bupivacaine 0.0625% (2).
References: 1) Anesth Analg 2013; 116:133-44; 2) Anesth Analg 2017; 124: 537-541.