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An Automated Programmable Intermittent Epidural Bolus (PIEB) Timer Unit: A Clinical Research Tool
Abstract Number: S-25
Abstract Type: Original Research
Intro: Patient controlled epidural analgesia (PCEA) with a continuous basal epidural infusion (CEI) delivered by an infusion pump is commonly used for labor analgesia. Studies have shown that CEI replaced with programmed intermittent epidural bolus (PIEB) results in lower total local anesthetic use and fewer PCEA demand boluses while providing equivalent labor analgesia. However, there is currently no commercial pump that can deliver PIEB combined with PCEA. Prior studies that evaluated the efficacy of PIEB with PCEA required 2 pumps with 2 infusion bags. Since the 2-pump system is clinically impractical, our goal is use commercially available items to design and build a compact PIEB timer unit that connects to the existing epidural infusion pump to deliver PIEB with PCEA.
Methods: A prototype of the PIEB timer unit (Fig 1) consists of a switch to set the timer interval, a PCEA button cable plugged into the timer unit, and an on-off switch for enabling PIEB function. A cable connects the relay output to the input of the infusion pump (Gemstar, Hospira Inc). An 8-bit central processing unit chip (MC9S08JM60, Freescale Semiconductor) was the brain of the PIEB timer unit, which triggers the relay to activate the infusion pump to deliver the programmed bolus based on the set time interval. A simple assembly language program was used to program the central processing chip, and the unit was powered with 4 AA batteries or an AC adapter. The device was connected to the pump (set at 3mL bolus, 5 min lockout, max 40 mL/h without CEI) with the PIEB timer interval set at 5, 15, 30 or 60 min, respectively. The set PIEB deliveries were each tested over a 24h period and compared against the data recorded in the Gemstar pump to evaluate the accuracy of the PIEB timer interval.
Results: All set PIEBs were delivered correctly as programmed with the PIEB timer. The accuracy (% time difference of PIEB timer vs Gemstar pump) was 99.89% (< 1.6 min difference in 24h). Battery life was >48h with a 15 min timer interval setting.
Discussion: This PIEB timer unit provides a useful clinical and research tool to provide accurate PIEB plus PCEA with or without CEI while using a single pump and infusion bag. With the use of an intelligent chip in the PIEB timer, future research can include a self-learning programmable PIEB timer to automatically adjust the PIEB interval based on demand bolus feedback.
Wong CA. A&A 2006;102:904-9.
Capogna G. A&A 2011;113(4):826-31.