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Identification of the L3-L4 Intervertebral Space in Obese Pregnant Women at Term in the Sitting and Lateral Positions: Palpation Method (Tuffier's Line) vs Ultrasound Imaging.
Abstract Number: F-23
Abstract Type: Original Research
Background: Tuffier’s line (TL) allegedly at L4 or L4-L5 level may be an unreliable landmark in pregnant women and in obese patients for lumbar techniques (1,2). The correct identification of the intervertebral space (IVS) for combined spinal-epidural techniques is important to avoid medullar puncture (3). We hypothesized that the identification of the L3-L4 IVS by palpation (TL) in the lateral position would result in a greater risk of error of at least 2 levels compared to the sitting position in term pregnant women with a BMI ≥30 kg/m2.
Methods: Adult term non-laboring pregnant women with a BMI ≥30 were recruited. Prior spine surgery and scoliosis were exclusion criterias. For each patient, anesthesiologists identified the L3-L4 IVS using the palpation method in the sitting and lateral positions. The investigator then performed an ultrasound imaging (US) to determine the accuracy of the level found in both positions. The difference between the IVS by palpation vs US was recorded. The primary outcome was the prevalence of overestimation of the L3-L4 IVS by at least 2 levels when relying on palpation vs US in the sitting and lateral positions. Uterine height, waist size and patient comfort were recorded as secondary outcomes. The McNemar test, the Fisher exact test and the Wilcoxon Mann-Whitney test were used for statistical analysis.
Results: In 94 patients, a difference of at least 2 levels was found in 14 patients (15%) in the sitting position and in 9 patients (10%) in the lateral position. The McNemar test resulted in a NS value of 0.1317. In 5 cases, T12-L1 level was identified as the target level (4 in the sitting position, 1 in the lateral position). No difference was found in the secondary outcomes.
Discussion: We did not find any difference in the accuracy of the level assessment by palpation between the sitting and lateral positions compared to US. We considered a difference of at least 2 levels to be significant since it would result in performing a neuraxial technique too high (L1-L2). Although the majority of assessments was correct, 10-15% were at least 2 levels higher in both positions and, in some cases, overestimation placed the L3-L4 level at the T12-L1 IVS. Caution must be taken when choosing a level for a subarachnoid puncture in this population and the use of US may be a helpful tool.
1. Allison JL Anesth & Analg 2011
2. Lin N. BMC Anesthesiology 2015
3. Reynolds F Anaesthesia 2001