Symtoms of SAH
Differential diagnosis of SAH
Subarachnoid haemorrhage (SAH) is spontaneous arterial bleeding into the subarachnoid space, usually from a cerebral aneurysm.
|Patients who have bled and in whom the diagnosis is initially missed, often present with a further bleed, in a poorer condition and with a worse outcome than in those in whom the correct diagnosis is made promptly. It is thus crucially important to detect SAH in all patients in whom it has occurred.|
Late presentations often confuse CT-findings whilst invasive catheter angiography to confirm suspected aneurysm carries with it a small but definite risk of increased morbidity and mortality. There is thus a need for a procedure for detecting those CT-negative patients presenting with a history suggestive of SAH who actually have sustained a SAH and to eliminate the diagnosis in the remainder without the need for catheter angiography i.e. CSF xanthachromia assay.
Following haemorrhage into the CSF, red blood cells undergo lysis and phagocytosis; the liberated oxyhaemoglobin is converted in-vivo in a time-dependent manner into bilirubin and sometimes methaemoglobin. Of these three pigments, only bilirubin arises solely from in-vivo conversion, (oxyhaemoglobin and methaemoglobin may both be produced in-vitro as well as in-vivo.) Consequently diagnosis of SAH may follow detection of primarily CSF bilirubin and oxyhaemoglobin, (upon analysis the presence of oxyhaemoglobin alone should be treated with caution and a repeat specimen advised.)
- Collection of any precious specimen requires that the clinician informs the laboratory staff, that a sample is on its way and that it be brought directly to Clinical Biochemistry personnel only (x7887/7888 or Bleep 233.) This is especially true of CSF Xanthachromia investigations, for which repeated lumbar puncture precludes the possibility of obtaining an accurate result as a result of the trauma incurred through initial sampling (bloody tap).
- Requests may be made via EPR through searching for: "CSF Xanthachromia."
- Whenever possible collect four sequential specimens. The specimen for spectrophotometry (sent to clinical biochemistry) should always be the last fraction of CSF to be taken.
- The specimen must be protected from light (typically submitted to Pathology wrapped in aluminium foil or envelope – whichever is most readily available.)
- Use of pneumatic tube systems to transport the CSF specimen to the laboratory is to be avoided and it should be submitted in the laboratory with a simultaneously drawn blood sample for serum bilirubin and total protein measurement.
- Record the timing of sampling (lumbar puncture) relative to that of possible haemorrhage; this should be more than 12 hours.
- Laboratory staff will be in contact in due course with the results provided all relevant contact information is available on the initial request form/ electronic order (please note: a bleep number is preferable so as to ensure effective result dissemination and expedited patient management.)
Last updated: 17 August 2016