Ultrasound guided versus conventional identification of the epidural space in obese parturients: A pilot study
Abstract Number: 31
Abstract Type: Original Research
Introduction: The epidural catheter failure rate is higher in the obese obstetric population, presumably from obscured landmarks, as well as false losses-of-resistance. Ultrasound (US) identification of the anatomy of the vertebral column and epidural space is a non-invasive method of visualizing the epidural space. The purpose of this study was to evaluate if the time to epidural catheter placement in obese parturients would be decreased with the use of ultrasonography compared to conventional methods.
Methods: Parturients with a body mass index (BMI) >35 kg/m2 gave consent to participate in this IRB-study. Exclusion criteria included scoliosis or previous back surgery. Upon request for labor analgesia, patients were randomized into the US or control group. Patients in the US group had US identification of the anatomy at the L3-4 and L2-3 interspace and the distance to the lig. flavum was noted. Skin markings were placed to identify the midline and center of the interspinous space and the distance to the lig. flavum was communicated to the anesthesiologist performing the procedure. The primary outcome was the epidural catheter placement time (Tuohy needle insertion to epidural catheter placement). Data collected included patient demographics, quality of surface landmarks, time to perform the US, total time (US and epidural catheter placement time), experience of the anesthesiologist, number of redirections and interspinous levels attempted, and patient satisfaction. Groups were compared using a 2-tailed t-test and P<0.05 was considered significant.
Results: 18 patients participated. There were no differences in the age, BMI, or quality of surface landmarks between groups. There was no difference in the experience level of the anesthesiologist between the groups. The mean epidural placement time was 154 seconds shorter in the US group (Figure) (P=0.28), however, the total placement time was not different. There was no difference in the number of redirections, number of interspinous levels attempted, or patient satisfaction scores between groups.
Discussion: Although there was no difference in the epidural placement time between groups, this study was probably underpowered to identify this difference. If a difference does exist, the time to perform the US may negate the time savings gained from visualizing the epidural space in obese parturients. A larger study is planned to evaluate a possible time savings with the use of the US in this population