Ultrasound-facilitated neuraxial anaesthesia in obstetrics

Comparison of ultrasonographic anatomy of spine in traditional sitting position versus crossed leg position in term pregnancy: A prospective, observational, crossover study

Background and Aims

The traditional sitting position (TSP) and crossed leg sitting position (CLSP) are positions used for neuraxial anaesthesia. This study compared the interspinous space (ISS) distance using ultrasound assessment of the spine in these positions in parturients in term gestation.

Methods

This prospective, observational study involved ultrasonographic spine assessment in 100 parturients in term gestation with them in either TSP or CLSP. The median sagittal view measured the crescent-shaped hyperechoic reflections of the spinous processes and ISSs in L3-L4, L4-L5 and L5-S1 levels. The paramedian sagittal oblique view showed interlaminar spaces (ILSs). Paired t-test and Chi-square test were used for continuous and categorical variables, respectively.

Results

The ISS distance (cm) increased in CLSP compared to TSP at levels L3-L4 (1.44 [0.34] [1.34-1.54] versus 1.22 [0.30] [1.12-1.32], P = 0.04), L4-L5 (1.34 [0.39] [1.20-1.48] versus 1.14 [0.30] [0.96-1.32], P = 0.01) and L5-S1 (1.28 [0.33] [1.17-1.39] versus 1.18 [0.23] [1.11-1.26], P = 0.02). The ILS distance (cm) increased in CLSP compared to TSP at interspaces L3-L4 (1.27 [0.34] [1.18-1.36] versus 1.12 [0.20] [1.08-1.16], P = 0.001), L4-L5 (1.26 [0.33] [1.17-1.35] versus 1.19 [0.32] [1.12-1.26], P = 0.01) and L5-S1 (1.28 [0.33] [1.18-1.38] versus 1.16 [0.27] [1.09-1.23], P = 0.001).

Conclusion

Crossed leg sitting position for neuraxial anaesthesia in term pregnancy results in more widening of both interspinous and interlaminar spaces compared to traditional sitting position.