Assessment of Catheter Flow Direction Using Color Flow Doppler in Labor Epidurals

Epidural analgesia is commonly used for pain relief in labor and involves placement of a catheter in the epidural space. Failure of epidural analgesia may occur in 12-16% of epidural catheter placements. It is defined as inadequate analgesia after the local anesthetic loading dose, despite use of appropriate dose/concentration of local anesthetic. Failure to provide adequate epidural analgesia is commonly caused by malposition of the epidural catheter. Many factors may influence the position of the tip of the epidural catheter and the resulting spread of local anesthetic into the epidural space, and consequently the quality of analgesia. Previously, X-ray exposure was required to assess catheter position in the epidural space. Recent developments have allowed the anesthesiologist to assess the catheter position at the bedside after its placement, using color flow Doppler ultrasonography.

The investigators will perform an observational study to determine epidural catheter flow direction in the obstetrical population using color flow Doppler ultrasound. Women who have delivered under epidural analgesia, either vaginal or caesarean delivery, will be approached for the study before the epidural catheter is removed.

The investigators aim to determine epidural flow relative to the insertion site, describe the findings and to correlate them with other clinical outcomes.