PULMONARY HEMODYNAMICS AND PLASMA ENDOTHELIN-1 DURING HYPOXEMIA AND REOXYGENATION WITH ROOM AIR OR 100-PERCENT OXYGEN IN A PIGLET MODEL

The immediate effect on the pulmonary circulation of reoxygenation wit h either room air or 100% O-2 was studied in newborn piglets. Hypoxemi a was induced by ventilation with 8% O-2 until base excess was <-20 mm ol/L or mean arterial blood pressure was <20 mm Hg. Reoxygenation was performed with either room air (n = 9) or 100% O-2 (n = 9). Mean pulmo nary artery pressure increased during hypoxemia (p = 0.012). After 5 m in of reoxygenation, pulmonary artery pressure increased further from 24 +/- 2 mm Hg at the end of hypoxemia to 35 +/- 3 mm Hg (p = 0.0077 v ersus baseline) in the room air group and from 27 +/- 3 mm Hg at the e nd of hypoxemia to 30 +/- 2 mmHg (p = 0.011 versus baseline) in the O- 2 group (NS between groups). Pulmonary vascular resistance index incre ased (p = 0.0005) during hypoxemia. During early reoxygenation pulmona ry vascular resistance index decreased rapidly to values comparable to baseline within 5 min of reoxygenation in both groups (NS between gro ups). Plasma endothelin-1 (ET-1) decreased during hypoxemia from 1.5 /- 0.1 ng/L at baseline to 1.2 +/- 0.1 ng/L at the end of hypoxemia (p = 0.003). After 30 min of reoxygenation plasma ET-1 increased to 1.8 +/- 0.3 and 1.5 +/- 0.2 ng/L in the room air and O-2 groups, respectiv ely (p = 0.0077 in each group versus end hypoxemia; NS between groups) . We conclude that hypoxemic pulmonary hypertension and plasma ET-1 no rmalizes as quickly when reoxygenation is performed with room air as w ith 100% O-2 in this hypoxia model with newborn piglets.