A randomized controlled trial of preinsertion ultrasound guidance for spinal anaesthesia in pregnancy: outcomes among obese and lean parturients: ultrasound for spinal anesthesia in pregnancy.

Purpose: The present study was conducted to examine if preinsertion lumbar ultrasound scanning helps with performance of spinal puncture, as a tool for decreasing the number of puncture attempts and spinal procedure time and increasing the success rate. We hypothesized that ultrasound can facilitate neuraxial blockade, particularly in pregnant women with difficult topographic anatomy.

Methods: One hundred (50 lean, BMI <30 kg/m(2), and 50 obese, BMI ≥30 kg/m(2)) parturients scheduled for cesarean delivery were divided into ultrasound and control groups. Subarachnoid block was performed with prepuncture ultrasound examination in lean parturients (group 1, n = 25) and in obese parturients (group 2, n = 25), and subarachnoid block was performed without prepuncture ultrasound examination in lean parturients (group 3, n = 25) and in obese parturients (group 4, n = 25). The number of puncture attempts and puncture levels were recorded.

Results: A lower number of puncture attempts and fewer puncture levels were detected in ultrasound (US) groups (p < 0.001). First attempt success rate under US guidance was 92 % in comparison to 44 % using a conventional technique in obese parturients (p < 0.001). In 52 % of the lean patients and in 54.2 % of the obese patients, the intercristal line was at the L3-L4 and at the L2-L3 interspace, respectively. The duration of spinal procedure was shorter in US groups (22 vs. 52 s, p = 0.031). We found a high correlation between ultrasound and needle depth (r = 0.709, p < 0.001).

Conclusions: We found a high level of success in the prepuncture ultrasound-determined insertion point. The ultrasound imaging technique can be a reliable guide to facilitate spinal anesthesia, especially in obese parturients.