Abstract
Needles for Combined Spinal-Epidural Anesthesia (CSEA) have been classified into the following three types:
1) Needle through needle type,
2) Needle through needle with back-eye type,
3) Needle beside needle type,
Each type of Combined Spinal-Epidural Needle has an individual maximal protrusion length of the spinal needle (7mm-15mm).
The subarachnoid puncture cannot be successfully performed, if the epidural needle is deflected from the midline of the epidural space, or the protrusion length of the spinal needle is not long enough to penetrate the dura.
The techniques of epidural puncture have also influenced the protrusion length of spinal needle at the subarachnoid puncture.
Paramedian approach required a longer protrusion length than the midline approach (8.0mm vs. 5.5mm, respectively).
To identify the epidural space, injection of saline (5ml) resulted in a longer protrusion length than that of air (9.7mm vs. 5.4mm, respectively).
It is important for successful CSEA to perform correct epidural and subarachnoid puncture, and to understand the protrusion length of spinal needle beyond the end of epidural needle related to the characteristics of needles and the techniques of puncture.
