Phosphodiesterase inhibitor-based vasodilation improves oxygen delivery and clinical outcomes following stage 1 palliation

Background-Systemic vasodilation using α-receptor blockade has been shown to decrease the incidence of postoperative cardiac arrest following stage 1 palliation (S1P), primarily when utilizing the modified Blalock-Taussig shunt. We studied the effects of a protocol in which milrinone was primarily used to lower systemic vascular resistance (SVR) following S1P using the right ventricular to pulmonary artery shunt, measuring its effects on oxygen delivery (DO₂) profiles and clinical outcomes. We also correlated Fick-based assessments of DO₂ with commonly used surrogate measures. Methods and Results-Neonates undergoing S1P were treated according to best clinical judgment prior to (n=32) and following (n=24) implementation of a protocol that guided operative, anesthetic, and postoperative management, particularly as it related to SVR. A majority of the subjects (n=51) received a modified right ventricular to pulmonary artery shunt. In a subset of these patients (n=21), oxygen consumption (VO₂) was measured and used to calculate SVR, DO₂, and oxygen debt. Neonates treated with the protocol had significantly lower SVR (P=0.02), serum lactate (P<0.001), and Sa-vO₂ difference (P<0.001) and a lower incidence of CPR requiring extracorporeal membrane oxygenation (E-CPR, P=0.02) within the first 72 postoperative hours. DO₂ was closely associated with SVR (r₂=0.78) but correlated poorly with arterial (SaO₂) and venous (SvO₂) oxyhemoglobin concentrations, the Sa-vO₂ difference, and blood pressure. Conclusions-A vasodilator protocol utilizing milrinone following S1P effectively decreased SVR, improved serum lactate, and decreased postoperative cardiac arrest. DO₂ correlated more closely with SVR than with Sa-vO₂ difference, highlighting the importance of measuring VO₂ in this population.