Utility of ultrasonography in identification of midline and epidural placement in severely obese parturients

BACKGROUND: Due to body habitus, lumbar epidural placement can be challenging in severely obese parturients. Several studies have been published assessing the usefulness of ultrasonography in the placement of neuraxial blocks. One patient population that is under-represented in these studies is the severely obese parturient. We sought to determine if performing an abbreviated ultrasound exam of the lumbar spine to determine midline by locating spinous process could facilitate lumbar epidural placement in severely obese parturients. METHODS: One hundred fifty patients with a Body Mass Index (BMI) of ≥35 kg/m2 were randomized into two groups. The palpation (P) group had midline identified by the traditional palpation technique. The ultrasonography (U) group had midline identified by ultrasound visualization of the spinous process in the transverse plane. Midline identification and epidural placement were done by both junior and senior anesthesiology residents at our teaching institution. RESULTS: Data were analyzed on all 150 patients. BMI was similar in the U and P groups (43.3 vs. 44.4 kg/m2, P=0.359). Time for epidural placement (6.2 vs. 9.0 minutes, P<0.01) and total procedure time (6.9 vs. 9.5 minutes, P<0.01) were significantly less in the U group. The number of needle passes (2.1 vs. 2.8, P=0.02) was also less in the U group. There was no significant difference in the failure rates of the U and P groups (4.0% vs. 9.3%, P=0.19). CONCLUSIONS: The use of an abbreviated ultrasound exam to identify midline in severely obese parturients can reduce the time required for lumbar epidural placement.