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

This study examines the responses of pial arterioles and venules to increased mean airway pressure (Pāw̄) in newborn pigs. We further characterized the changes in cortical subarachnoid cerebrospinal fluid prostanoids with increased Pāw̄, both before and afer 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 Pāw̄ 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-PGF₁α, TxB₂, PGE₂, and PGE₂α), however were increased reversibly (3- to 5-fold) by increasing Pāw̄. After indomethacin (5mg/kg, intravenous) pial arterioles constricted approximately 15% with increased Pāw̄. These results suggest that increasing ventilation pressures increases brain prostanoid production. Prostanoids appear to inhibit vasoconstriction and may be important in maintaining cerebral flow during the stress of mechanical ventilation.