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

Abstract

BackgroundSystemic 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 ResultsNeonates 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‐vO 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 (r2=0.78) but correlated poorly with arterial (SaO2) and venous (SvO2) oxyhemoglobin concentrations, the Sa‐vO 2 difference, and blood pressure.ConclusionsA 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‐vO 2 difference, highlighting the importance of measuring VO 2 in this population.Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT02184169.

Impact of a Composite Valved RV-PA Graft After Stage 1 Palliation

“…(1) There was an important learning curve that took place throughout the duration of this study that may have affected the results. (2) Although most patients included in the study were treated according to a protocol for the perioperative and postoperative care of these patients, a higher fraction of patients undergoing homograft placement were treated according to an institutional protocol that decreased systemic vascular resistance and decreased the incidence of cardiac arrest [14]. It is possible that some of the perioperative findings noted here were in part related to the protocol.…”

“…In most patients undergoing homograft placement, the valved portion was enshrouded with an external 8-Â 15-mm biliary stent (Cordis, Tipperary, Ireland) to prevent dilation of the valved portion and incompetence of the valve. Since January 2014, our practice has been to routinely leave the sternum open and to implement early vasodilator treatment in the intensive care unit [14].…”

Physiologic effects of delayed sternal closure following stage 1 palliation

“…In a sub-set of patients (n = 22 patients), oxygen consumption was measured and used to calculate systemic blood flow by the modified Fick principle as previously described (Oxygen Consumption Based Assessment of Hemodynamics in Newborns, NCT02184169). 5 Surgical variables, including anatomic sub-types, ischaemic times, and listing of subsequent operations, were extracted from an internal surgical database. Technical performance scores were assessed at the time of discharge or reintervention before discharge, as previously described.…”

“…Similarly, it is difficult to exclude the possibility of an era effect over this seven-year study, as several aspects of care changed during that time, including our approach to systemic vasodilator use. 5 Our understanding of the physiologic effects of delayed sternal closure and the ability to predict failed sternal closures may improve if a larger number of patients can be included under a homogeneous care environment. This may be possible by protocolising care and completing this study at several large centres simultaneously.…”

“…During this period, variations in temperature, systemic vascular resistance, bleeding, sedation, and ventricular function all combine to increase the risks of low cardiac output syndrome and sudden cardiac arrest 3 4 These risks can be reduced by standardising practice surrounding the use of vasodilators, inotropes, sedatives, as well as temperature and bleeding management, which has led to improvement in short-term outcomes in several studies 5 6 The use of delayed sternal closure has also been frequently used as a technique in the post-operative care of patients following the stage 1 palliation 7 …”