Prediction of epidural depth before labor epidural placement-A Normogram
Abstract Number: 49
Abstract Type: Original Research
Introduction: Prior knowledge of depth from skin to the epidural space can increase the epidural catheter placement success rate.1 We did a study to determine if ultrasound (US) measurement of the depth from skin to the epidural space prior to labor epidural placement decreases the failed epidural placement rate and developed a normogram based on patient height and weight for prediction of the distance from the skin to the epidural space.
Methods: In this prospective, randomized, non-blinded study, 370 parturients for elective labor epidural analgesia were randomized into one of to two groups: ultrasound determination of epidural space depth before epidural catheter placement (US group), or standard labor epidural catheter placement without the use of ultrasound (Control group) placed by resident trainees. Using a sterile technique, in the sitting position, epidural catheters were placed midline in both groups through a 17 gauge Tuohy needle in the L3-4 or L4-5 vertebral interspace using a saline loss of resistance technique. Multivariate linear regression was used to create a normogram based on height and weight of the patient.
Results: An equation to determine the lower lumbar intervertebral distance from the skin to the epidural space using multivariate linear regression analysis with height and weight as factors reveals the distance to be:
Epidural Depth = 5.63 - [0.025 x Ht (cm)] + [0.040 x Wt (kg)]
A normogram based on height and weight for prediction of the distance from the skin to the epidural space is presented.
Conclusion: The Normogram we have presented can be used to estimate the approximate epidural depth and help in the actual placement of the labor epidural by resident trainees.
1. National Institute for Health and Clinical Excellence. Ultrasound Guided Catherisation of the Epidural Space: Understanding NICE Guidance. January, 2008.