Distribution of hematocrit values after aneurysmal subarachnoid hemorrhage

Low hematocrit values are common after subarachnoid hemorrhage and may be associated with elevated cerebral blood flow and transcranial Doppler ultrasound (TCD) velocities, which may confound the interpretation of velocity as an indicator of vasospasm. The exact distribution of hematocrit among a neurosurgical population would be useful in assessing the magnitude of this difficulty but has not been previously reported. A database containing hematocrit values recorded at TCD examinations over a period of 7 years was reviewed. Two thousand four hundred thirteen hematocrit values were recorded for 575 patients. The distribution of hematocrit values was recorded among patients and among TCD studies. Eighteen percent of the patient population achieved a hematocrit of 26% or less at some point in their hospital stay, whereas 57% of patients achieved a hematocrit of 30% or less. Six percent of the TCD studies were associated with a hematocrit of 26% or less, while 33% of the studies were associated with a hematocrit of 30% or less.