What is the incidence of PDPH following inadvertent dural puncture during attempted epidural anesthesia?
Unintentional dural puncture during attempted epidural anesthesia occurs with a reported incidence of 1-5% depending on operator experience. Because of the large size of epidural needles, PDPH following dural puncture occurs with an incidence as high as 85%.
The characteristic bilateral frontal-occipital headache which improves with recumbency is thought to be caused by the persistent leakage of CSF from the tear in the dura. The resulting intracranial hypotension allows the brain to sag when the patient is upright, which places traction on pain-sensitive intracranial vascular structures. Reflex vasodilation and vascular engorgement contributes to the headache. Seventy-five to 85% of PDPHs resolve spontaneously before 5 days. There are reports of PDPHs lasting for more than a year.
A lower incidence of PDPH occurs if the epidural needle pierces the dura while the needle bevel is oriented parallel to the long (vertical) axis of the spine compared to when the bevel is oriented perpendicular to the spine (24% compared with 70%)5. The likely explanation for this is that the normal tension directed along the long axis of the dura holds a horizontally-oriented hole open and pulls a vertically-oriented hole closed.
When performing epidural anesthesia, rather than obtaining a loss of resistance with the bevel facing cephalad, it has been recommended that one advance the needle with the bevel parallel to the long axis of the spine to decrease the incidence of PDPH if the dura is punctured. When threading a catheter, the needle should be rotated 90 degrees to face the bevel cephalad once entry into the epidural space has been confirmed. Results of recent clinical studies support the practice of needle rotation6 despite previous assertions that needle rotation increases the rate of dural puncture7, 8.
Some recommend that following an unintentional dural puncture a catheter should be threaded into the subarachnoid space and the technique be converted to a continuous spinal anesthetic if possible. The catheter can be used for postoperative or labor analgesia. A decreased incidence of PDPH when a subarachnoid catheter has been left in place for 12-24 hours has been demonstrated by some studies9, 10 but not by others11, 12.
Misidentification of a subarachnoid catheter for an epidural catheter should be prevented by clearly labeling the subarachnoid catheter as such. If an infusion is not started, it is recommended that the catheter be occluded by tying knots in it to prevent its use.