Role of prostanoids in cerebrovascular responses to asphyxia and reventilation in newborn pigs.

Cerebral hemodynamics during asphyxia and reventilation were investigated in normothermic, hypothermic (35 degrees C), and indomethacin-pretreated (5 mg/kg iv) anesthetized, newborn pigs. In the normothermic group, total cerebral blood flow (CBF) measured with radioactive microspheres was 57 +/- 12 ml.min-1 x 100 g-1 during baseline, 104 +/- 19 at 1 min of asphyxia, 39 +/- 5 at 5 min of asphyxia, 186 +/- 16 at 8 min of reventilation, and 95 +/- 20 at 16 min of reventilation. During asphyxia and reventilation blood flow to brain stem was better regulated than to cerebrum or cerebellum. Baseline CBF was similar in the indomethacin and hypothermic groups (32 +/- 2 and 41 +/- 5 ml.min-1 x 100 g-1, respectively; n = 5 for each group). However, during asphyxia, blood flow was never less in either one of these groups than in the normothermic group in spite of a lack of arterial hypercapnia at 1 min in the hypothermia group. During reventilation, blood flow was sometimes lower in the hypothermic and indomethacin groups than the normothermic group but never lower when considered on a percentage change from baseline basis. We conclude that inhibition of prostanoid production with indomethacin did not limit vasodilation during these conditions.