It is crucially important to detect subarachnoid haemorrhage ( SAH ) in all patients in whom it has occurred to select patients for angiography and preventative surgery. A computerized tomography ( CT ) scan is positive in up to 98% of patients with SAH presenting within 12 hours, but is positive in only 50% of those presenting within one week.
Cerebrospinal fluid ( CSF ) bilirubin spectrophotometry can be used to determine the need for angiography in those few CT-negative patients in whom clinical suspicion of a SAH remains high; it may remain positive up to two weeks after the event. A lumbar puncture (LP) should only be performed > 12 hours after the onset of presenting symptoms. Whenever possible collect sequential specimens. Always ensure that the least blood-stained CSF sample taken (usually the last) is sent for bilirubin analysis. Protect the CSF from light and avoid vacuum tube transport systems, if possible. Always use spectrophotometry in preference to visual inspection. All CSF specimens are precious and should always be analysed unless insufficient sample is received. Centrifuge the specimen at >2000rpm for 5 min as soon as possible after receipt in the laboratory. Store the supernatant at 4℃in the dark until analysis. An increase in CSF bilirubin is the key finding, which supports the occurance of SAH but is not specific for this. In most positive cases, bilirubin will occur with oxyhaemoglobin.
UV/Vis spectrophotometry scans of CSF xanthochromia although the recommended technique can be difficult to interpret. The trace produced requires the user to manually draw a tangent between two points. This in many cases can be very subjective and offers the potential for introducing calculation errors.
BIO-C Version 7 software
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