METHODS: Parturients with a body mass index (BMI) ≥30 kg/m2 scheduled for elective cesarean delivery were randomized to undergo spinal anesthesia using the conventional landmark location technique (landmark group, n = 40) or prepuncture ultrasound examination (ultrasound group, n = 40). All participants underwent spinal anesthesia in the lateral position. The primary outcome was the first-attempt success rate. Secondary outcomes were the number of skin punctures and needle passes, procedure times, patient satisfaction, changes in the intended interspace, and incidence of complications.
RESULTS: The ultrasound group had a significantly higher first-attempt success rate (87.5% vs 52.5%; P = .001), fewer cases requiring >10 needle passes (1 vs 17; P < .001), and fewer skin punctures and needle passes (P < .001 for both). There was no statistically significant difference in the time taken to identify the needle insertion site between the 2 groups (202.5 vs 272.0 seconds; P = .580). Both the spinal injection time and total procedure time were significantly longer in the landmark group (P < .001). Patient satisfaction scores were significantly higher in the ultrasound group (P = .001). Among patients with BMI between 30 and 34.9 kg/m2, there was no statistically significant difference in the first-attempt success rate (P = .407), number of cases with >10 needle passes (P = .231), spinal injection time (P = .081), or total procedure time (P = .729); however, more time was required to identify the needle insertion site in the ultrasound group (P < .001). For patients with BMI between 35 and 43 kg/m2, the ultrasound group had a significantly higher first-attempt success rate (P ≤ .041), fewer cases with >10 needle passes (P ≤ .01), and shorter procedure times, including the time required to identify the needle insertion site (P < .001).
CONCLUSIONS: Prepuncture ultrasound examination can facilitate spinal anesthesia in the lateral position in obese parturients (35 kg/m2 ≤ BMI ≤ 43 kg/m2) by improving the first-attempt success rate, reducing the number of needle passes and puncture attempts, shortening the total procedure time, and improving patient satisfaction.