Differentiation of early subarachnoid hemorrhage from traumatic lumbar puncture.

The problem of early differentiation of "traumatic tap" from subarachnoid hemorrhage (SAH) was studied in the rabbit by determining the changes in percentage of hemolysis and in lactate concentrations in CSF within the first twenty-four hours following induced SAH. The 0.3 to 7% hemolysis which occurred was relatively independent both of the time following SAH and of the number of red blood cells (rbc) in the cerebrospinal fluid (CSF). There was, on the other hand, a significant and time-dependent increase in CSF lactate concentration early after SAH, suggesting the potential clinical value of the detection of increased lactate with a relatively normal lactate/pyruvate ratio in hemorrhagic CSF. Until this can be evaluated in human subjects, however, determination of the rbc counts or total hemoglobin concentrations in serially collected samples of CSF remains the best clinical method.