الفهرس 
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Abstract
Most studies of ultrasound-assisted spinal anesthesia in the obstetric population are dated and nonblinded with inconsistent designs. This double-blind, randomized controlled study aimed to compare the ultrasonography with the conventional palpation techniques for spinal anesthesia in obese parturients undergoing cesarean delivery. We hypothesized that the use of preprocedural ultrasonography would decrease the number of needle passes required for obtaining free CSF flow. Eligible subjects were American Society of Anesthesiologists physical status II parturients with full term singleton pregnancy and Body Mass Index (BMI) ≥ 35 Kg/m2 undergoing elective cesarean delivery using spinal anesthesia. Exclusion criteria were age < 19 years, women presenting in labor, or having contraindications to neuraxial anesthesia (coagulopathy, increased intracranial pressure, or local skin infection). Two hundred eighty patients were randomly allocated into 2 equal groups (ultrasonography and palpation groups). All procedures were performed by a single experienced anesthesiologist. Patients and investigators assessing the outcome data were blinded to group allocation. A systematic spinal ultrasonography assessment and a sham procedure were performed in the ultrasonography and palpation groups, respectively, before attempting spinal anesthesia. The primary outcome was the number of needle passes required for obtaining free CSF flow. Secondary outcomes were the success rate at the first skin puncture, the success rate at the first needle pass, the number of performed skin punctures, the duration of the procedure, patient satisfaction from the procedure, the incidence of complications (unintentional vascular puncture) and the incidence of failed block. Data from 280 (140 patients in the ultrasonography group and 140 patients in the palpation group) were analyzed. The number of needle passes required to obtain free flowing CSF was 3(1-34) in the ultrasonography and 3(1-23) in the palpation group (Observed Treatment Effect was 0.00007 (-0.00005 to 1); P = 0.62). There were no significant differences between the 2 groups in the success rate at the first skin puncture, the success rate at the first needle pass, or patient satisfaction. The median (range) duration of spinal anesthesia procedure was 76 (26-734) seconds in the ultrasonography group and 59 (19-700) seconds in the palpation group; the difference between the 2 groups was insignificant (P = 0.077) when the data were compared using the Mann-Whitney U test. The overall rate of complications of the procedure was low in both groups. For experienced anesthesiologists, it remains unclear whether preprocedural ultrasonography improves the spinal anesthesia technique in obese parturients undergoing cesarean delivery.