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Accuracy of 3D Ultrasound for Identification of Epidural Needle Skin Insertion Point in Parturients; A Prospective Observational Study
Abstract Number: S-02
Abstract Type: Original Research
We developed a novel 3D ultrasound (3DUS) Thick Slice image processing technique and innovative epidural needle guide to facilitate real-time, single-operator, midline epidural needle insertions [1,2]. We hypothesized that 3DUS would identify an appropriate needle puncture site within a ≤ 5 mm radius as compared to the gold standard manual palpation technique in term parturients.
Based on a previous 2DUS study, power calculations determined a sample size of 20 term parturients to be recruited . Subjects were seated upright on the edge of a leveled bed while L2-3 and L3-4 levels were palpated and then marked laterally. The 3DUS transducer (Ultrasonix model m4DC7-3/40) was placed in the paramedian plane with a custom-made clip-on needle guide to visualize the ligamentum flavum. An erasable marker was used to indicate where the needle, sliding in the guide, would touch the skin (picture). The skin mark was copied onto a transparency and erased from the skin. The epidural needle puncture site was then identified using the standard palpation technique, marked, and then transferred onto the same transparency. A single researcher scanned and palpated at both levels. The primary outcome was the distance (mean ± standard deviation) between the 3DUS and palpation points measured on the transparency.
To date, we have recruited 19 out of 20 subjects. In 95% of our measurements (36 out of 38) 3DUS identified midline epidural needle puncture sites within a 5mm radius compared to the standard palpation technique. The mean distance between the two points was 2.9 mm and the standard deviation was 1.5mm.
The new 3D Thick Slice US offers reliable localization of midline epidural needle puncture sites in parturients. Future studies should assess the benefit of the 3DUS for the real time visualization of the epidural needle insertion.
 Rasoulian et al., Canadian Anes. Soc. Meet. S51, 2010.
 Rasoulian et al., LNCS Vol. 7915, 51-60, 2013.
 Tran et al., Canadian J Anesthesia, 57(4), 313-321, 2010.