The electrical potential difference and impedance between CSF and blood in unanesthetized man.

The electrical potential difference (PD) between cerebrospinal fluid (CSF) and blood has been studied extensively in animals. To obtain data from man the PD and impedance were recorded from the lumbar subarachnoid space of thirteen unanaesthetized patients with a presumably normal blood--brain barrier. The spontaneous PD ranged from 1 mV to 5 mV, CSF positive to blood. Hyperventilation and CO2-inhalation changed the PD with a mean slope of deltaPD/deltapHa of --4.16 mV/pH. The CSF-blood PD in unanaesthetized man is similar in direction to that found in dogs, goats and rats, but its sensitivity to change in arterial pH may be less.