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When Millimeters Count, Epidural Loss of Resistance Techniques Differ: A Simulator Study
Abstract Number: S1B-4
Abstract Type: Original Research
Introduction: Postdural puncture headache is a complication of accidental dural puncture (ADP) that occurs in 1.5% of routine epidural placements . Epidural simulators have been used to teach anesthesiology providers the loss of resistance (LOR) technique to identify the epidural space . We measured overshoot of the needle tip past a LOR plane in a mixed reality simulator for three LOR techniques to infer the likelihood of traversing the epidural space and associated ADP.
Methods: Three LOR techniques were studied: incremental needle advancement, with intermittent LOR assessment (II); continuous needle advancement, with high frequency intermittent LOR assessment (CI); and continuous needle advancement, with continuous LOR assessment (CC). We asked 41 consenting anesthesia providers to identify LOR using each approach 5 times with the LOR set at random depths in the simulator software. A linear mixed model for repeated measures was used to assess mean differences in overshoot between techniques. The technique was modeled as a repeated measure to account for within-participant correlations. Secondary analyses included operator experience level (AA or CRNA, resident or fellow, and attending) as a fixed effect and as part of an interaction with technique (level × technique).
Results: The primary outcome measure was needle tip overshoot (in millimeters) after LOR was felt. There were significant mean differences in overshoot due to technique (F(2,39) = 56.29, p < 0.001). Specifically, overshoot was greater in II (mean = 3.8mm, 95%CI: 3.4 – 4.2) vs. CC (mean = 1.8mm, 95%CI: 1.4 – 2.2; p <0.001) or CI (mean = 1.4mm, 95%CI: 1.0 – 1.8; p < 0.001) (Fig. 1). CC and CI were not statistically different (p = 0.179). Training level did not have a significant relationship with overshoot (p = 0.317) or a significant interaction with technique (p = 0.447).
Conclusion: The II LOR assessment technique demonstrated the greatest needle tip overshoot into the simulated epidural space after LOR was felt. This was consistent across all experience levels. Our study demonstrates that the LOR assessment technique II results in the deepest needle advancement beyond the actual LOR. If our simulator data are representative of what would occur in actual patients, our findings suggest ADP may be more likely with technique II than with the CI or CC LOR identification techniques.
1. Can J Anaesth 2003;50:460-9
2. J Med Educ 1969;44:515-9