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Is PIEB superior to PCEA for labor analgesia? A novel In-vitro variable resistance and flow dynamic epidural simulation model analyzes this controversy.
Abstract Number: T210-187
Abstract Type: Original Research
Clinical studies have conflicting conclusions of superiority of Programmable Intermittent Epidural Bolus (PIEB) over Patient Controlled Epidural (PCEA), or continuous epidural (CEA) for labor analgesia. Epidural spread of drugs is dependent on several factors and these have not been elucidated. We designed an epidural model to analyze epidural flow dynamics of currently used epidural labor analgesia modes and study a high volume PCEA as a ‘test’ mode.
Methods: An epidural space of 3 to 4 mm was fabricated by interposing 1¾ inch diameter PVC tube into a 2-inch diameter clear polycarbonate (PC) tube. The PVC tube was wrapped with two layers of Bounty absorbable paper with wavy pattern to simulate noncontiguous epidural space and absorption of the fluid by fat and vasculature. Intervertebral foramina of 78 mm2, interspaced 30 mm apart, were fashioned on each side of the PC tube. Two sets of models were fabricated for simultaneous study. The epidural catheter was placed inside the epidural space and connected to Cadd Solo pump programed with PIEB (9 ml q45min pump delivered, and 10 ml q10 min, patient option, limit 48 ml/hr), PCEA8 (8 ml/hr,8 ml q15 min, limit 32 ml), PCEA6 (6/6q15,32), and 12 ml/hr CEA. The driving fluid was normal saline with methylene blue. The patient-controlled boluses were used as permissible in each mode to the maximum limit allowed . The distribution of the dye was analyzed using SketchAndCalc Area Calculator. The effect of gravity was studied in by repeating simulations for each of PIEB and PCEA6 modes in lateral position by turning the model 90 degrees. In addition, the effect of decreased resistance in the epidural space for these two modes was studied by decreasing one layer of Bounty paper. A ‘test’ high volume PCEA12 (12/10 q15,42) was also studied in both supine and lateral positions.
Results: Areas of spread are shown in figure and varied from 189.1 (PIEB) to 52.8 cm2 (CEA) demonstrating PIEB’s superiority over PCEA6, 8, and CEA (Figure). In simulated lateral position, gravity favored better spread in the dependent area. Decreasing resistance increased epidural area of distribution, (PIEB 229 to 410, and PCEA6 113 to 289 cm2). ‘Test’ high volume mode PCEA12 was as effective as PIEB (185 vs 189 cm2). This novel model demonstrates that volume and frequency of doses together with position and compliance of epidural space determines final distribution of epidural fluid.
Ref:IJOA 2016;26:32-38. GM-4, SOAP 2018; S1B6, SOAP 2018