Increasing ventilation pressure increases cortical subarachnoid cerebrospinal fluid prostanoids in newborn pigs

This study examines the responses of pial arterioles and venules to increased mean airway pressure (P aw-) in newborn pigs. We further characterized the changes in cortical subarachnoid cerebrospinal fluid prostanoids with increased P aw-, both before and after cyclooxygenase inhibition with indomethacin. Eight chloralose anesthetized newborn pigs were equipped with closed cranial windows and ventilated with a conventional infant pressure-cycled respirator. Increasing P aw- from 3.2 +/- 0.3 cm water to 14.3 +/- 0.6 cm water did not change pial arteriole or venule diameters. Cerebrospinal fluid prostanoids (6-keto-PGF1 alpha, TxB2, PGE2, and PGF2 alpha), however, were increased reversibly (3- to 5-fold) by increasing P aw-. After indomethacin (5 mg/kg, intravenous) pial arterioles constricted approximately 15% with increased P aw-. These results suggest that increasing ventilation pressure increases brain prostanoid production. Prostanoids appear to inhibit vasoconstriction and may be important in maintaining cerebral blood flow during the stress of mechanical ventilation.