Headache after attempted epidural block: the role of intrathecal air

Postmeningeal puncture headache (PMPH) is typically attributed to the loss of cerebrospinal fluid (CSF). However, when it occurs after an attempted epidural puncture, it may be due to either CSF loss or, potentially, to the subarachnoid injection of air used as a part of "loss-of-resistance" testing. This study was performed to examine the relation between intrathecal air and PMPH.

Using a loss-of-resistance test with an air-filled (n = 1,812; air group) or saline-filled (n = 1,918; saline group) syringe, epidural block was performed in patients with acute or chronic pain. The dura was judged to be perforated not only when backflow of CSF was recognized in the needle but also when signs and symptoms solely attributable to meningeal perforation were seen, such as high spinal blockade or severe motor blockade. The incidence, onset time, and duration of PMPH in the air and saline groups were compared. In all patients with signs of meningeal perforation, brain computed tomography was examined.

The incidence of PMPH in the air group (32 cases) was significantly higher than that in the saline group (5 cases), although the occurrences of meningeal perforation between the air (48 cases) and saline (51 cases) groups did not differ significantly. Intrathecal air bubbles were detected on brain computed tomography in both the deep supraspinal structures such as the ventricles, Silvian fissures and cisterns, and the superficial subarachnoid space in 30 of 32 patients with PMPH in the air group, whereas no intrathecal air bubbles were seen in the saline group. PMPH was significantly more rapid in onset and shorter in duration in the air group than that in the saline group.

The use of air for loss-of-resistance testing during epidural block was associated with a higher incidence of PMPH, which might be attributable to subarachnoid air injection and CSF leakage.