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Gravity Flow Technique to Validate Proper Positioning of Epidural Needle Tip
Abstract Number: S1B-5
Abstract Type: Original Research
Introduction: The failure rate of lumbar epidural analgesia for labor may be as high as 23% . One cause of failure is misidentification of the epidural space. Methods to increase the likelihood of properly positioning the epidural needle tip have been advocated, including a combined spinal-epidural (CSE) technique with  or without  intrathecal administration of medication, and electronically transducing the pressure waveform from the tip of the epidural needle . Another method to confirm proper placement of the epidural needle tip is the gravity flow technique, in which the vascular pulsations from the epidural space are mechanically transduced . This study was designed to prospectively assess the efficacy of the gravity flow technique in parturients requesting epidural analgesia for labor.
Methods: Written consent was obtained from 100 parturients requesting epidural analgesia for labor. A 17G Tuohy needle was used to locate the epidural space using loss of resistance to air. A 20 mL syringe was filled with labor analgesia solution (bupivacaine 0.04%, epinephrine 1.66 mcg/mL, sufentanil 0.4 mcg/mL) and attached via a 3-way stopcock to an 81 cm intravenous extension tubing, which was then primed with the solution. Next, the extension tubing was attached to the hub of the Touhy needle, the syringe was elevated, and the stopcock opened to entrain an air bubble, which was observed for synchronous fluctuation with the maternal pulse. Once observed, 15 to 20 mL of analgesic solution was allowed to flow by gravity through the epidural needle, and a 19G catheter was threaded. Epidural analgesia was confirmed by the presence of bilateral lower abdominal hypesthesia to ice within 30 minutes.
Results: We observed fluctuations in synch with the maternal pulse in all 100 subjects, and bilateral hypesthesia was achieved in all subjects within 30 minutes.
Discussion: Recently, transducing the pressure waveforms from the epidural space has been described as a means of confirming proper epidural needle tip position . However, this is a cumbersome technique requiring a transducer and a monitor, which may not be readily available in labor rooms. Furthermore, it is relatively expensive in comparison with the low cost mechanical manometry of the gravity flow technique, which requires only sterile intravenous extension tubing and 3-way stopcock to observe the vascular pulsations of the epidural space . This simple technique reliably provides valuable information to determine whether or not the epidural needle tip is properly positioned in the epidural space, and helps to reduce the incidence of failed labor epidural analgesia.
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