Power Doppler Ultrasonography in Localization of Epidural Catheter

Five milliliters of sterile saline will be administered as a flush through the needle while recording the color flow doppler images. The same procedure will be repeated with a slow injection of 5 mL of saline. The speed of injection will not be standardized.

"All color flow Doppler images will be performed with a Phillips CX50 ultrasound machine using a 5.0 MHz a low frequency curvilinear US probe. A two-dimensional transverse interspinous view was used to visualize the posterior complex (ligamentum flavum, epidural space and dura). After loss of resistance to normal saline, the color flow Doppler function will be turned on to examine flow through the epidural needle tip.~The ultrasound probe was positioned in the transverse axis slightly below the epidural needle but still in the interspinous space ."