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The accuracy of SLIDE: a novel ultrasound software system for automatic identification of lumbar vertebral levels in parturients - a prospective observational study.
Abstract Number: S4A-6
Abstract Type: Original Research
Introduction: Lumbar ultrasonography has been used to facilitate neuraxial needle placements in parturients. However, the acquisition and interpretation of ultrasound (US) images can be challenging. We developed a proprietary US software system (SLIDE) that in real-time automatically identifies vertebral landmarks while the operator slides the US transducer over the lumbar spine2. We sought to compare the accuracy of the SLIDE versus manual palpation (PAL) methods for determining the primary target of L3-4 interspace, using the traditional lumbar US (LUS) method as a reference standard.
Methods: After ethics board approval and written consent, 76 healthy term parturients scheduled for cesarean delivery under spinal anesthesia were recruited. An anesthesiologist first identified the L3-4 interspace using the PAL method. Next, a non-anesthesiologist identified the L3-4 interspace using the SLIDE method. Finally, an expert provider used the LUS method to determine the reference location for the L3-4 interspace. Measurements obtained between methods were blinded using the transparency sheet technique. The primary outcome was accuracy of L3-4 identification with SLIDE and PAL compared to LUS. The raw percentage agreement and Gwet’s AC1 were calculated. Mixed-effects logistic regression was used to determine the relationship between accuracy and demographic variables. Secondary outcomes included accuracy of other lumbar levels identification and time to identify L3-4 interspace.
Results: Compared to LUS, the raw agreement was 69.7%, Gwet’s AC1 0.59 (95% CI: 0.41-0.77) for PAL and 84.2%, AC1 0.82 (95% CI: 0.70-0.93) for SLIDE. In general, where PAL disagreed with LUS, it identified L2-3 more often than L4-5. However, when SLIDE disagreed with LUS, it was equally above or below L3-4. The SLIDE method was significantly more accurate in locating L3-4, and all other lumbar interspaces after controlling for BMI (OR=2.99; 95% CI 1.21-8.65; p=0.02). The median(IQR) times to obtain L3-4 for PAL, SLIDE and LUS were 0.43 (0.38-0.48) min, 1.5 (1.0-2.2) min and 1.6 (1.4-2.1) min, respectively.
Conclusion: Compared to PAL, SLIDE was by 14% more accurate in identifying L3-4 interspaces in healthy elective cesarean delivery patients. Additionally, SLIDE was more accurate in identifying all other lumbar interspaces and conferred greater accuracy in higher BMI patients.
1. Ecimovic P et al. IJOA 2010
2. Beigi P et al. Ultrasound Med. Biol 2017