Changes in the rate of formation and resistance to reabsorption of cerebrospinal fluid during deliberate hypotension induced with adenosine or hemorrhage.

Abstract

Adenosine is recommended for induction of deliberate hypotension. Although its effects on brain vasculature and metabolism and intracranial pressure have been reported, its effects on cerebrospinal fluid dynamics have not. In this study the rate of cerebrospinal fluid formation (Vf), resistance to reabsorption of cerebrospinal fluid (Ra), and electroencephalogram (EEG) activity were determined in rabbits before and during decrease of cerebral perfusion pressure (CPP) with intravenous (iv) adenosine or hemorrhage. In the adenosine group (n = 6), Vf and Ra were determined at control CPP, at CPP of 50, 35, and 28 mmHg achieved with iv adenosine, and at CPP greater than 60 mmHg achieved with iv adenosine combined with iv phenylephrine. In the hemorrhage group (n = 6), Vf and Ra were determined at the first four experimental conditions only. Control values for Vf (9 +/- 3 and 9 +/- 4 microliter.min-1, mean +/- SD) and Ra (428 +/- 567 and 412 +/- 144 cmH2O.ml-1.min) did not differ between groups. In the adenosine group, Vf did not change significantly when CPP was decreased. However, in the hemorrhage group, Vf decreased significantly at CPP of 50 and 35 mmHg and became unmeasurable at CPP of 28 mmHg. Ra did not change significantly in either group. An increase of low-frequency (0.5-3.0 Hz) EEG activity and/or decrease of higher-frequency (3.5-30 Hz) EEG activity occurred at CPP of 28 mmHg in the adenosine group and at CPP of 35 mmHg in the hemorrhage group.(ABSTRACT TRUNCATED AT 250 WORDS)