Commentary: Pursuing the optimal vasoactive support post–stage I Norwood: Don't trust, just verify

Abstract

Central MessageThe use of vasopressin in the post-Norwood period is associated with blood pressure response at the expense of increased pulmonary blood flow and decreased systemic oxygen delivery.See Article page 217. The use of vasopressin in the post-Norwood period is associated with blood pressure response at the expense of increased pulmonary blood flow and decreased systemic oxygen delivery. See Article page 217. Since its original report, it has been recognized that the stage I palliation for hypoplastic left heart syndrome represents a formidable challenge in terms of surgical reconstruction as well as perioperative management. While early efforts to embrace and reproduce this palliative strategy were focused on the technical details, success was elusive until a thorough understanding of this physiology was achieved. Perhaps the most significant initial success was the incorporation of novel physiological concepts, a delicate circulatory balance between systemic, pulmonary, and coronary circulations, which did not conform to the conventional biventricular circulation in series. In addition, perioperative management presented the additional challenge that following a major surgical reconstruction, commonly with a period of myocardial ischemia, these patients continue to face increased cardiac demands, secondary to the mandatory volume burden in the presence of only one ventricle. Not surprisingly, many patients receive some type of vasoactive support in the perioperative period. The question is which one is the optimal? A physiology characterized by a single ventricle with systemic and pulmonary circulations connected in parallel at the arterial level is unique and underscores the importance of how the relationship between systemic vascular resistance (SVR)/pulmonary vascular resistance affects the distribution of the single-ventricle output. Previous work based on mass spectrometry demonstrated that dopamine has an important effect on resistance ratio relationship, leading to alterations of the Qp/Qs balance associated with lower oxygen delivery despite a vasopressor response.1Li J. Zhang G. Holtby H. Humpl T. Caldarone C.A. Van Arsdell G.S. et al.Adverse effects of dopamine on systemic hemodynamic status and oxygen transport in neonates after the Norwood procedure.J Am Coll Cardiol. 2006; 48: 1859-1864Crossref PubMed Scopus (67) Google Scholar Bronicki and colleagues2Bronicki R.A. Acosta S. Savorgnan F. Flores S. Achuff B.J. Loomba R. et al.The acute influence of vasopressin on hemodynamic status and tissue oxygenation following the Norwood procedure.J Thorac Cardiovasc Surg Open. 2022; 9: 217-224Scopus (1) Google Scholar use a series of noninvasive surrogates of oxygen delivery to describe their observations with the use of vasopressin (AVP), a vasoactive drug that increases SVR, without affecting cardiac contractility or ventricular end-diastolic volume, therefore associated with decreased stroke volume and ejection fraction as the blood pressure rises. This should be cause for great concern, considering the perioperative Norwood physiology already described. As it could have been anticipated, AVP infusion was associated with a blood pressure response as well as increase in Qp/Qs and cerebral and renal oxygen extraction ratio in patients undergoing stage I Norwood, who received a conduit from the right ventricle to the pulmonary artery. This can be interpreted as secondary to elevation of SVR, shunting a larger proportion of the cardiac output toward the pulmonary circulation. Surprisingly, and despite the potential for diastolic runoff, patients who received a systemic to pulmonary artery shunt had a lower blood pressure response, which could be expected as more runoff into the pulmonary circulation occurs, but more importantly they had no significant change in Qp/Qs or cerebral and renal oxygen extraction ratio. While these observations are difficult to reconcile, several potential explanations could be possible. Perhaps the use of a larger right ventricle to pulmonary artery conduit indexed to body surface area allowed for more diversion of blood away from the systemic circulation, or the native neurohumoral response could have been already heightened and resulted in a blunted response to AVP, or perhaps the findings could be explained by error in sampling by the noninvasive surrogate monitoring. Nevertheless, this work emphasizes the importance of understanding what we do in clinical practice, the need to follow sound physiologic principles, and to always remember that the end-goal is optimization of oxygen delivery and not set on one arbitrary hemodynamic parameter. While this work has important limitations, its relevance is not based on the answers it provides but rather raising many good additional questions, bringing us back to think critically about what we choose to do and the reasons behind it. The acute influence of vasopressin on hemodynamic status and tissue oxygenation following the Norwood procedureJTCVS OpenVol. 9PreviewArginine vasopressin (AVP) is used to treat hypotension. Because AVP increases blood pressure by increasing systemic vascular resistance, it may have an adverse effect on tissue oxygenation following the Norwood procedure. Full-Text PDF Open Access