Utility of Ultrasound in Identification of Midline and Placement of Epidural in Severely Obese Parturients

The use of ultrasound has expanded into many areas of medicine including the identification of bony landmarks to facilitate epidural placement in obstetric anesthesia. Using ultrasound for epidural placement has become popular over the last decade with several studies being published on the topic. The likely increase in popularity for ultrasound use in the obstetric population is the need to more reliably locate bony landmarks as the traditional palpation technique has been shown to be an inaccurate way to accomplish this. Given the fact that the long-taught palpation technique can be inaccurate and studies have validated the use of ultrasound for epidural placement, ultrasound technique is routinely taught by the obstetric anesthesiologists to the anesthesiology residents at the University of Alabama at Birmingham (UAB). Also, since both techniques are considered standard practice at UAB, anesthesia providers (residents, fellows, and faculty) are free to choose either technique to locate bony structures of the back prior to epidural placement. Since no current study has specifically addressed its use in the obese pregnant patient, the investigators would like to validate its use in this population.

In this study, investigators will evaluate the use of ultrasound in the obese population to determine if its use will decrease the time it takes to place the epidural and number of attempts required when compared to the traditional palpation technique. The study will also determine the success rate of epidural placement in both the palpation and ultrasound groups.

• Palpation (Procedure): Traditional epidural methods used for the identification of the midline using palpation prior to procedure
• Ultrasound (Device): Lumbar spinal ultrasound performed for identification of the midline prior to procedure.

Primary outcomes

• Time for Epidural Placement [Baseline up to 1 hour]: Comparing the time it takes for epidural placement in the palpation group vs. the ultrasound group. Measured in minutes from local anesthesia skin wheal to administration of the epidural test dose.
• Number of Needle Passes [Baseline up to 1 hour]
• Total Time [Baseline up to 1 hour]

Secondary outcomes

• Time to Identify Midline [Baseline up to 1 hour]: Comparing the time it takes to locate midline of the back in the palpation group vs. the ultrasound group. Measured in minutes from the start of the identification process until completion of the midline identification process.
• Epidural Failure Rate [Baseline up to 1 hour]: Comparing the number of epidural failures in the palpation vs. ultrasound group.
• Number of Top-offs Required [Baseline up to 1 hour]

Sex: Female, ages: 19 Years to 45 Years, accepts healthy volunteers

Inclusion Criteria:

* patient request for a labor epidural
* BMI≥35

Exclusion Criteria:

* BMI<35
* patient refusal of a labor epidural
* coagulopathy
* platelets<80,000
* prior spine procedure or instrumentation
* a diagnosis of scoliosis
* an intracranial or spinal mass

Participant flow

Outcome results

• Time for Epidural Placement (Primary), Mean, minutes: Palpation Group 9.0 +/- 6.8; Ultrasound Group 6.2 +/- 3.8
• Number of Needle Passes (Primary), Mean, needle passes: Palpation Group 2.8 +/- 2.0; Ultrasound Group 2.1 +/- 1.4
• Total Time (Primary), Mean, Minutes: Palpation Group 9.5 +/- 6.8; Ultrasound Group 6.9 +/- 3.9
• Time to Identify Midline (Secondary), Mean, seconds: Palpation Group 30.9 +/- 16.3; Ultrasound Group 44.5 +/- 24.7
• Epidural Failure Rate (Secondary), Number, failed epidurals: Palpation Group 7; Ultrasound Group 3
• Number of Top-offs Required (Secondary), Mean, number of topoffs required: Palpation Group 0.5 +/- 1.1; Ultrasound Group 0.4 +/- 0.9

Adverse events

Time frame: Baseline up to 1 hour

• Study Protocol and Statistical Analysis Plan (PDF, 2015-06-19)

• Mark F Powell, MD, Principal investigator, University of Alabama at Birmingham