Pulmonary hypertensive crisis is a life-threatening condition, in which the blood pressure in
the pulmonary artery, vein, and capillaries. Infusion of hypertonic saline solutions expand
the circulating volume, thus allowing more blood to flow and reducing pressure in the artery,
vein, and capillaries. Furthermore, infusion of hypertonic saline has been shown to reduce
both systemic and pulmonary vascular resistances in adults. If the pulmonary vascular
resistance decreases more or to the same degree as the systemic resistance, infusion of
hypertonic saline may prove beneficial in the treatment of pulmonary hypertensive crisis. The
primary objective of this study is to investigate how a clinically relevant dose of
hypertonic saline affects the systemic and pulmonary circulations in children undergoing
cardiac catheterization during general anesthesia. This study hypothesizes that an infusion
of hypertonic saline over 10 minutes will reduce the pulmonary vascular resistance more than
the systemic vascular resistance.