INDOMETHACIN COMPROMISES HEMODYNAMICS DURING POSITIVE-PRESSURE VENTILATION, INDEPENDENTLY OF PROSTANOIDS

We examined whether prostanoids contribute to the impaired cardiac function and decrease in regional blood flow induced by increasing mean airway pressure. Using microspheres, we measured cardiac output and major organ blood flow and assayed prostaglandin E2, 6-ketoprostaglandin F1alpha, and thromboxane B2 in blood at mean airway pressures of 5-25 cmH2O in mechanically ventilated newborn piglets treated with ibuprofen (40 mg/kg, n = 6), indomethacin (0.3 mg/kg, n = 6), or vehicle (n = 6). Blood gases and pH were stable throughout the experiments. Prostanoid levels remained constant, with increasing mean airway pressure in vehicle-treated pigs and were unchanged by indomethacin. However, ibuprofen decreased the prostanoid levels at all mean airway pressures studied (P < 0.01). As ventilatory pressure was progressively increased, cardiac output decreased gradually and similarly by 42-45% (P < 0.05) in all groups. At the highest mean airway pressure, blood flow decreased to the kidneys by 37-57%, to the ileum by 58-74%, and to the colon by 53-71% (P < 0.05) in all groups. Cerebral blood flow remained constant at all ventilatory pressures regardless of the treatment. There was no difference in cardiac output and regional hemodynamics between ibuprofen- and vehicle-treated animals. However, after indomethacin, ileal blood flow at the higher ventilatory pressures was 41-46% lower and cerebral blood flow at all mean airway pressures was 14-25% lower than after the other treatments (P < 0.05). Thus the decreases in cardiac output and regional blood flow induced by positive-pressure ventilation are not mediated by prostanoids. Indomethacin compromises regional hemodynamics during increased mean airway pressure, and this effect is also independent of prostanoids.