Spectrophotometric analysis of CSF after subarachnoid hemorrhage: limitations in the diagnosis of rebleeding.

We studied the course of CSF xanthochromia after subarachnoid hemorrhage by serial spectrophotometric analysis of lumbar CSF in 15 patients without clinical or CT evidence of rebleeding. The xanthochromic index rose in some patients up to the seventeenth day, and the proportion of oxyhemoglobin or the absolute concentration of hemoglobin often fluctuated. Therefore, rebleeding can be demonstrated in lumbar CSF only by increased xanthochromia, if previous samples had shown a decrease. These criteria could be applied in only 6 of 17 consecutive patients with rebleeding as demonstrated by CT, and they were met in 5.