Increased free fatty acid turnover in CSF during hypotension in dogs.

Cerebrospinal fluid turnover rates of FFA were investigated using ventriculocisternal perfusion techniques. Seven conscious dogs were perfused over a 6-h period from the lateral ventricle to the cisterna magna with mock cerebrospinal fluid (CSF) containing [14C]palmitate and 100 mumol/l of FFA. One hundred and twenty minutes of perfusion were allowed to establish equilibrium of the FFA concentration in the ventricular space. Moderate hemorrhage hypotension was then induced (MABP greater than 60 mmHg) for 3 h, followed by rapid retransfusion and a final hour of perfusion. Cerebral blood flow did not change significantly (45 +/- 6 before, 53 +/- 6 after hemorrhage, and 47 +/- 5 ml.min-1. 100 g-1 after retransfusion). Cerebral arteriovenous difference of O2, glucose, and pH increased significantly during hemorrhage. Hypotension was accompanied by an increased turnover of FFA from 60 to 120 nmol/min (P less than 0.01) in the CSF. FFA turnover was directly correlated with the fatty acid concentration of the CSF (r = 0.77). It is speculated that the increased fatty acid turnover during hypotension may indicate increased phospholipid turnover and/or increased oxidation by tissues lining the ventricular space.