A Novel Way to Estimate Epidural Depth in Morbidly Obese Parturient

The Use of Ultrasound With the Epidural Depth Equation (EQ-US) to Estimate Epidural Depth (Est-D) in Morbidly Obese Parturients (BMI>40Kg/m2) Will Have a High Correlation With Actual Epidural Needle Depth (ND)

The purpose of this study is to determine the correlation between actual epidural needle depth (ND) and the use of ultrasound with an epidural depth equation (EQ-US) to estimate epidural depth (Est-D) in morbidly obese parturients. It is well documented that in women with a BMI greater than 40 kg/m2 successful epidural placement is more difficult. To the best of our knowledge the use of an epidural depth equation, which was developed in an earlier study using height and weight, with ultrasound visualization will improve identification of the epidural space.

The investigators plan to enroll women who are morbidly obese (BMI > 40 kg/m2) and request epidural analgesia for labor. After written informed consent, 160 patients will have the use of the epidural depth equation with ultrasound (EQ-US) to estimate epidural depth (Est-D). US visualization of the epidural space will be completed by the principle investigator who has had extensive training in epidural US visualization. The EQ-US depth will be recorded. After US use, another provider who is listed as an investigator will place the epidural catheter without prior knowledge of the estimated epidural depth with the use of the equation and US. The actual needle depth to the epidural space (ND) will be recorded. Data collected from the patient's medical record will include demographic data (age, height, weight) gravidity, parity, and cervical dilation. Measured variables will include the estimated epidural depth (Est-D) as measured by the epidural depth equation with the use of ultrasound (EQ-US), and actual epidural needle depth (ND). The investigators believe that the use of ultrasound with the epidural depth equation (EQ-US) to estimate epidural depth (Est-D) in morbidly obese parturients will have a high correlation with actual epidural needle depth (ND).

Ultrasound using the Sonosite S-Nerve® US system (SonoSite, Bothell,WA) to measure depth to epidural space in morbidly obese parturients.

Measured using the Pearson correlation coefficient between actual epidural needle depth (ND) and epidural depth as estimated by the epidural depth equation (EQ-US) followed by ultrasound (longitudinal and transverse planes) measurement.

at the time of labor epidural catheter insertion (an average of 5 minutes for ultrasound visualization)

Inclusion Criteria: All women of childbearing age (including children aged 14 years and above) with a BMI > 40kg/m2 who request epidural analgesia at Magee-Womens Hospital will be eligible to participate in the study. Men will not be included since they can not become pregnant. All patients will be recruited at Magee-Womens Hospital. Exclusion Criteria: Patients with severe preeclampsia will be excluded from the study, as these patients may have significant edema which could alter ultrasound and/or epidural needle depth measurement. Patients with a history of back surgery, significant scoliosis, and/or lumbar pathology (i.e. Ankylosing Spondylitis) will be excluded from the study because these conditions could complicate ultrasound visualization and/or epidural needle placement.