Indirect sonographic guidance for epidural anesthesia in obese pregnant patients

Obesity and edema frequently obscure anatomic landmarks and result in technical difficulties during epidural anesthesia administration. However, the method of indirect sonographic guidance permits identification of the midline by sagittal scan of the laminae of lumbar vertebrae 2, 3, and 4.

Thirty-six obese women scheduled for elective repeat cesarean delivery were prospectively studied. Use of a 5-MHz transducer positioned with the transducer center site over the second or third interspace allowed measurement of skin-to-lamina distance by the electronic calipers of a Toshiba SAL-32B or RT 3000 GE machine, prediction of needle depth for epidural puncture (EP), and skin marking of the site. After the transducer was removed, a 9.5- or 11.4-cm Tuohy needle was percutaneously advanced perpendicularly from the site until EP was achieved.

Needle depth was measured by marker and measure, and epidural anesthesia was successfully administered to all patients. Simple linear regression analysis was performed with strong positive results. Indirect and continuous sonographic guidance studies designed to determine whether sonography reduces complications are planned.