901-107 Fetal Model of Single Ventricle Physiology: Hemodynamic Effects of Epinephrine, Sodium Bicarbonate, and Calcium Chloride

Neonatal and infant patients (pts) with single ventricle physiology (SVP) following bypass, for e,g, pts after stage I repair of hypoplastic left heart syndrome (HLHS), often suffer from hemodynamic instability early after surgery, Specific hemodynamic effects of pharmacologic resuscitation are poorly understood. To examine these issues a model of SVP was created in fetal lambs: a Damus procedure was performed in fetal lambs using a 10 mm ePTFE tube graft and the main pulmonary artery was ligated distally. Pulmonary blood flow (PBF) was provided by creating a 6 mm systemic to pulmonary artery shunt. Neonatal lambs with SVP were delivered normally at term, At 48 hours after birth the lambs (n = 10) were instrumented and monitored. Ultrasonic flow probes were placed on the aorta and the shunt to measure systemic blood flow (SBF) and PBF. Interventions were performed In random order before and after cardiopulmonary bypass and a 30 min period of hypothermic circulatory arrest to mimic the clinical setting e.g. stage I repair of HLHS. The effects on systemic and pulmonary vascular resistances (SVR and PVR), PBF, and SBF are shown below Intervention PBF SBF PVR:SVR PBF 1 SBF 1 PVR:SVR 1 Epi infusion 2 13.5 * 20.8 * +6.8 13.8 * 14.5 * -7.5 Bicarbonate 3 9.2 * 13.5 * -4.5 10.2 * 16.6 * -0.4 Ca chloride 4 7.9 * 16.8 * +2.6 12.64 * 18.7 * -1.7 Epi bolus 5 94.1 * -68.8 * -88.8 * Values represent percent increase or decrease from baseline. 1: post bypass; 2: epinephrine O. 1 μg/kg/min; 3: sodium bicarbonate 2 mEq/kg 4: calcium chloride 10 mg/kg; 5: epinephrine 1 in 10,000: 0.05 ml/kg * P l 0.05. In summary this is the first reported model which provides a useful tool to study neonatal SVP Epinephrine infusion, sodium bicarbonate bolus, and calcium chloride bolus increased both PBF and SBF. Epinephrine bolus even at half the recommended code dose caused a tremendous increase in PBF and severe decrease in systemic blood flow causing metabolic acidosis. On average it took 5 min for the flows to return to base line values. This suggests that epinephrine boluses should be used judiciously and probably be considerably smaller in the management of patients with SVP. Calcium chloride had a good inotropic effect without significant effect on PVR:SVR ratio.