Importance of Forward Leaning in Optimizing Sitting Position for Administration of Labor Neuraxial Analgesia in Term Parturients: An Ultrasonographical Study

Abstract

Abstract Background: There is controversy on the optimal sitting position for women in labor undergoing neuraxial analgesia placement in relation to the interspinous space. In this prospective observational study, we investigated the five sitting positions in order to identify the optimal position that provides the widest lumbar interspinous space (LIS) for neuraxial needle insertion in laboring parturients using ultrasonographic measurements. Methods: Methods: We performed ultrasonographic measurements on 38 participants at three lumbar levels (L2-L3, L3-L4 and L4-L5) in five different sitting positions: fetal sitting position (FS), traditional sitting position (TS), crossed legs sitting position (CLS), hamstring stretch sitting position (HSS) and modified hugging sitting position (MHS). These five positions were subdivided into two groups based on whether the torso was leaned forward: Hip Flexed Only (HFO) group and Hip Flexed and Leaning forward (HFL) group. The primary outcome was the LIS distances between two adjacent lumbar vertebrae as measured by ultrasonography. The comfort level of each position was also rated by participants. Normal distribution of data was checked by the Shapiro–Wilk test. The interspinous space of subjects was evaluated with paired t-test. Wilcoxon signed rank-test was performed to compare the comfort level of 5 positions. We use adjusted P values to accommodate multiple tests. Adjust P values were calculated by using Holm’s correction. P 0.05 was considered statistically significant. Results: In the HFO group, the widest LIS was at L2-L3 (FS: Δ L2-L3 vs. L3-L4 = 2.20 mm, Δ L2-L3 vs. L4-L5 = 1.90 mm, TS: Δ L2-L3 vs. L3-L4 = 2.90 mm, Δ L2-L3 vs. L4-L5 = 1.90 mm, CLS: Δ L2-L3 vs. L3-L4 = 2.60 mm). At the L3-L4 level, the HFL group generated wider LIS than the HFO group. Compared with positions in the HFO group, MHS showed a significantly increased LIS by 8.74% (Δ MHS vs. FS=2.5mm, 95%CI: 0.1-3.9mm), 9.93% (Δ MHS vs. TS=2.9mm, 95%CI: 1.4-4.3mm), and 7.05% (Δ MHS vs. CLS=2.1mm, 95%CI: 0.1-3.3mm). HSS showed a significantly increased LIS by 8.56% (Δ HSS vs. TS=2.5mm, 95%CI: 1.2-3.8mm) and 7.12% (Δ HSS vs. CLS=2.1mm, 95%CI: 0.5-3.6mm). At L2-L3 and L4-L5, there was no statistically significant difference between five sitting positions at each lumbar level. MHS had the highest comfort level and was preferred by 47.37% of subjects. Discussion: In term parturients, the width of the interspinous space was maximally increased in HFL positions with forward lean compared to HFO positions without forward lean at L3-L4. This implies that the forward leaning process could be crucial for successful neuraxial administration. The modified hugging sitting position was found to be more comfortable than the hamstring-stretch sitting position. For HFO parturients, whose forward leaning mobility is limited, the L2–L3 level showed the widest LIS for neuraxial access.