Distribution of cardiac output and oxygen delivery in an acute animal model of single-ventricle physiology.

BACKGROUND

When single-ventricle physiology is established acutely (ie, after a Norwood procedure), the combination of limited cardiac output and hypoxemia could result in limited oxygen transport to systemic organs. This study investigates the regional distribution of cardiac output and oxygen delivery after creation of single-ventricle physiology.

METHODS

Single-ventricle physiology was created in 8 piglets, and 8 other piglets served as sham control animals. Aortopulmonary shunt, echocardiography-guided atrial septostomy, tricuspid valve avulsion, and pulmonary artery occlusion allowed the left ventricle to support systemic and pulmonary circulations. Physiologic parameters and regional blood flow were determined at baseline and at 30 and 120 minutes after conversion to single-ventricle physiology. Parameters were compared by means of 1-way and 2-way analysis of variance.

RESULTS

Single-ventricle physiology resulted in lower diastolic arterial pressure, oxygen saturation, and arterial oxygen saturation (P < .05), whereas hemoglobin was unchanged. Cerebral blood flow increased markedly in control animals (P = .04). In contrast, in single-ventricle physiology regional blood flow was unchanged in the brain, higher in the myocardium (P = .1), and mildly reduced in low-priority organs (liver, kidneys, and bowel). Cerebral oxygen delivery increased in control animals, whereas in animals with single-ventricle physiology, oxygen delivery decreased in the brain, liver, kidneys, and bowel (P < .05) and was unchanged in the myocardium. Total-body oxygen delivery decreased in animals with single-ventricle physiology (P < .001) but not in control animals. Total-body oxygen consumption was unchanged in both groups.

CONCLUSIONS

This study shows that in acute single-ventricle physiology hypoxemia and limited regional blood flow reduce oxygen transport to low-priority organs and partly to the brain. These findings might contribute to the understanding of gastrointestinal and neurologic complications in children with single-ventricle physiology.