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Xanthochromia is not pathognomonic for subarachnoid hemorrhage
1Section of Emergency Medicine, Brown Medical School, Department of Emergency Medicine, Rhode Island Hospital, Providence, RI 02903, USA.
Objective:
To test the hypothesis that xanthochromia may be observed in traumatic lumbar puncture (LP). Xanthochromia, the yellow discoloration of cerebrospinal fluid (CSF) caused by hemoglobin catabolism, is classically thought to arise within several hours after subarachnoid hemorrhage (SAH). The presence of xanthochromic supernatant is often used to distinguish the elevated red blood cell (RBC) count observed in the CSF of SAH from the elevated RBC count observed after traumatic LP.
Methods:
The authors developed a model of traumatic LP by adding whole blood to pigment-free CSF to obtain RBC concentrations of 0, 5000, 10000, 20000, 30000, and 40000 RBC/ microL. Supernatant from centrifuged samples was assessed for xanthochromia by spectrophotometry. Xanthochromia was considered present if the absorption followed a characteristic oxyhemoglobin curve with a maximal absorption greater than 0.023 at 415 nm.
Results:
Samples with at least 30000 RBC/ microL demonstrated xanthochromia immediately. Samples with 20000 RBC/ microL demonstrated xanthochromia within one hour, and samples with 10000 RBC/ microL or less, within two hours.
Conclusions:
Cerebrospinal fluid xanthochromia may be observed within two hours after traumatic LP and sooner in samples with greater than 10000 RBC/ microL. Conversely, xanthochromia in traumatic LP with less than 5000 RBC warrants further investigation for SAH. When the CSF RBC count is elevated above 10000 RBC/ microL, or the time between sample acquisition and analysis is prolonged, the clinician should not rely on xanthochromia to confirm SAH.