Phosphodiesterase Inhibitor‐Based Vasodilation Improves Oxygen Delivery and Clinical Outcomes Following Stage 1 Palliation

Abstract

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 ( DO 2 ) profiles and clinical outcomes. We also correlated Fick‐based assessments of DO 2 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 ( VO 2 ) was measured and used to calculate SVR , DO 2 , and oxygen debt. Neonates treated with the protocol had significantly lower SVR ( P =0.02), serum lactate ( P <0.001), and Sa‐v O 2 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. DO 2 was closely associated with SVR (r 2 =0.78) but correlated poorly with arterial (SaO 2 ) and venous (SvO 2 ) oxyhemoglobin concentrations, the Sa‐v O 2 difference, and blood pressure. Conclusions A vasodilator protocol utilizing milrinone following S1P effectively decreased SVR , improved serum lactate, and decreased postoperative cardiac arrest. DO 2 correlated more closely with SVR than with Sa‐v O 2 difference, highlighting the importance of measuring VO 2 in this population. Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifier: NCT 02184169.