Ultrasonography and epidural anaesthesia. Technical possibilities and boundaries of ultrasonic examination of the epidural space

Epidural anaesthesia (EA) is the most important analgesia technique in obst etrics for delivery. In pregnancy, hormonal adjustments lead to an arte rat ion of tissue consistency, which often causes an early, untimely loss of re sistance. Apart from mere inspection and palpation, no useful diagnostic me thod prior to EA performance has been established yet. In this prospective study, we examined 100 pregnant women, who had been admitted for childbirth and were undergoing epidural block (level L3-L4) for delivery. Sonotopogra phy of the lumbar epidural structures was performed directly before epidura l puncture and childbirth. We evaluated the visibility of all anatomical st ructures and compared all distances measured by ultrasonography and du ri n g puncture. The correlation between distances measured by ultrasound and by puncture needle was high (r(2)=0.79). No obvious dependency was found betw een ultrasonic and puncture angle (r(2)=0.19). The temporal distance from u ltrasonic examination and puncture causes unavoidable differences: each dev iation between ultrasound and puncture conditions causes a modification of the puncture depth. The patient acceptance of the procedure was very good. Ultrasonography offers the possibility to determine site and direction of e pidural puncture and distance of the epidural space to the skin even before the puncture attempt. The ultrasound controlled EA for delivery can easily be inserted into the clinical routine. Ultrasonography can fill an importa nt diagnostic gap in regional anaesthesia.