Topic: Subarachnoid Hemorrhage
Subject: Medicine
A 25-year-old male presents 5 hours after the onset of the worst headache of my life. His temperature is 37.0°C (98.6°F), blood pressure 140/90 mm Hg, respiratory rate 20/min, and pulse rate 90 beats/min. The patient is lethargic but oriented; there are no focal neurologic findings, but neck stiffness is present. Unenhanced CT of the head is negative. You elect to perform a lumbar puncture. At this time, which one of the following findings in bloody spinal fluid would indicate a diagnosis of subarachnoid hemorrhage?

Correct Answer : A.

Xanthochromia is a yellow, orange, or pink discoloration of the CSF, most often caused by the lysis of RBCs resulting in hemoglobin breakdown to oxyhemoglobin, methemoglobin, and bilirubin. Discoloration begins after RBCs have been in spinal fluid for about two hours, and remains for two to four weeks.5 Xanthochromia is present in more than 90 percent of patients within 12 hours of subarachnoid hemorrhage onset.
> The WBC:RBC ratio is more useful in diagnosing meningitis with traumatic taps. The ratio could be similar in subarachnoid hemorrhage or traumatic spinal tap.
> The 1:1000 ratio of g of protein/L to RBC/L is a correct approximation but would not be very useful in distinguishing subarachnoid hemorrage from traumatic tap.
> Glucose in cerebrospinal fluid will drop with chemical meningitis caused by blood. This reduction is less than with most infections. It does not drop below a level of 2.2 mmol/L.