Higher Cerebrospinal Fluid pH may Contribute to the Development of Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage

Recent investigations have shown that many factors may cause delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH). To find new potential contributors to DCI, this retrospective study compared gas data in the cerebrospinal fluid (CSF) between patients with and without DCI. The subjects were 61 consecutive patients with SAH classified as Fisher group III on admission computed tomography scans, whose aneurysms were obliterated by clipping or coiling within 24 h post-SAH. Thirty-three patients were treated with CSF drainage. CSF samples were chronologically obtained from CSF drains or lumbar taps. Patients with DCI were more frequently treated with CSF drainage, especially cisternal drainage, and were associated with significantly higher pH and lower partial pressure of carbon dioxide (PCO₂) in the CSF compared with patients without DCI, although CSF concentrations of bicarbonate ion as well as arterial blood gas data were not different between the two groups. Total hemoglobin concentrations in the drained or tapped CSF were higher in patients with no DCI compared with patients with DCI at any sampling time, suggesting that CSF hemoglobin was not efficiently removed in patients with DCI. This study revealed higher CSF pH and lower CSF PCO₂ as new potential contributors to the development of DCI, which might result from inappropriate CSF drainage that failed to remove clot and acid metabolites in it efficiently. Both of the disturbed CSF gas and inappropriate CSF drainage may cause constriction of the arteries and arterioles, leading to DCI.