Ultrasonic localization of the lumbar epidural space
Lumbar epidural anesthesia was performed in 26 patients by an anesthesiology resident at either the L2-L3 or L3-L4 interspace using the loss-of-resistance technique. Measurements obtained ultrasonically the night before were not available to this resident. In the 22 successful epidural anesthetics, a good correlation between predicted distance (ultrasound) and measured needle distance occurred (r=0.99, p<0.0001). Average distance to the epidural space was 4.6 cm by both a priori ultrasound and a posteriori needle measurements. Among the 26 lumbar epidural anesthetics, four blocks were unsuccessful. Two unsuccessful blocks were characterized by a centimeter difference between the ultrasound measured distance and the needle measured distance. The other two unsuccessful blocks were due to accidental dislodgement of the catheter from the epidural space with removal of the needle.