Background Ultrasound is commonly used to facilitate epidural catheter placement. However, data are lacking regarding its potential to confirm its position in the epidural space. Our aim was to visualize flow in the epidural space of patients receiving epidural analgesia for labor using color flow Doppler ultrasound.
Methods We conducted a prospective observational cohort study that included patients who had delivered vaginally under epidural analgesia. We used a 5–2 mHz curvilinear probe in a left and right paramedian longitudinal oblique view to visualize the anterior and posterior complex at the interspace of epidural catheter insertion, one and two interspaces above and below. At each window, the color flow Doppler function was used to visualize flow within the epidural space on injection of normal saline (1 mL). If no flow was visualized at any interspace, one assessment at the level of insertion was repeated with a 1 mL air/saline mixture. We studied a convenience sample size of 40 patients.
Results We visualized flow in the epidural space in all 40 patients. Flow was visualized on injection of 1 mL of saline in 37/40 patients (93%). In the remaining 3/40 patients (7%), flow was visualized with an air/saline mixture. Flow on injection of saline was visualized only at the interspace of insertion in 26/37 patients (70%), at the interspace of insertion and one interspace above in 10/37 (27%), or only at one interspace above in 1/37 (3%). Flow was visualized only on the left or on the right paramedian view in 19/37 patients (51%), despite a symmetrical sensory block in all patients.
Conclusion Color flow Doppler ultrasound is a feasible and fast way to determine flow in the epidural space in the obstetric population. Its potential clinical uses are confirmation of the epidural catheter position after placement, as well as troubleshooting of unsatisfactory epidural analgesia. Interestingly, our results suggest that epidural catheters predominantly remain at the interspace of insertion.
Trial registration number NCT05126745.
- REGIONAL ANESTHESIA
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Presented at This study was presented in part at the 54th Annual Meeting of the Society for Obstetric Anesthesia and Perinatology, Chicago, May 11, 2022–14, May 2022.
Contributors OFCvdB helped with study design, data collection, data analysis, writing the manuscript, and is the author responsible for the overall content of the manuscript. YG helped with study design, data collection and writing the manuscript. CA helped with study design, data collection and writing the manuscript. NS helped with study design, data collection and writing the manuscript. KD helped with data collection and writing the manuscript. JCAC helped with study design, data collection, data analysis and writing the manuscript. OFCvdB is the author responsible for all content.
Funding JCAC is supported by the Merit Awards Program from the Department of Anesthesiology and Pain Medicine, University of Toronto.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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