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Using high fidelity pressure monitoring to compare different loss of resistance techniques for epidural placement.
Abstract Number: SAT-16
Abstract Type: Original Research
Background: There are many approaches for epidural loss of resistance (LOR) technique; air vs saline, glass vs plastic syringes, continuous vs intermittent pressure. We hypothesized that high fidelity pressure monitoring from the epidural syringe will be able to provide quantifiable measures of compliance changes and identify one technique as more sensitive.
Methods: This study received formal IRB waiver as a non-human study. We evaluated B-Braun 5 cc glass syringes and Periflex 8mL plastic LOR syringes on the Genesis Epidural Spinal-Injector simulator, using 18G Touhy epidural needles (B-Braun). The epidural syringe was connected by 3-way stop cock to Edwards Lifesciences TruWave invasive pressure transducer with sampling interval of 6μsec. Data processing of signal was performed with Rugloop2, pressure-time curves were generated with MATLAB and Excel. All 24 members of the OB Anesthesia team (faculty, fellows and CRNA’s) participated in this study; each performed epidural insertion under pressure monitoring using 8 separate techniques: continuous-glass-air (CGA), continuous-glass-saline (CGS), continuous-plastic-air (CPA), continuous-plastic-saline (CPS), intermittent-glass-air (IGA), intermittent-glass-saline (IGS), intermittent-plastic-air (IPA), intermittent-plastic-saline (IPS). Order was randomized. After each attempt, the provider reported sensitivity of LOR on an 11-point VAS (0-10). Data was de-identified and analyzed by 2 blinded investigators. For continuous pressure LOR, we assessed the slope of the “downstroke” (Fig 1A) as the linear slope from the 5% to the 50% change. We compared 4 data sets: CGA vs CGS; CPA vs CPA; CGS vs CPS and CGA vs CPA. We used four paired t-tests to compare data for all subjects; p=0.05/4=0.0125 (Bonferroni); data calculated using SPSS. For intermittent pressure LOR, we averaged 3 “upstrokes” (Fig 1B), before LOR and the upstroke after LOR; the endpoint was the %change in slope from BL.
Results: The data for slopes of downstroke using continuous LOR are presented in Fig 1. There were no significant differences between any of the pairs assessed. Data for intermittent LOR was collected but not interpreted in time for the abstract but will be available by the time of the SOAP meeting.
Conclusion: For LOR with continuous pressure there was no quantitative difference between glass vs plastic syringes or air vs saline. Data has yet to be assessed for intermittent pressure.