‘Which vasoactive agent?’ for the sick child is a question that suggests the existence of a ready answer. But, with critically ill children, the ‘answer’ is context-specific. What is the clinical situation? Is the predominant problem impaired myocardial function post cardiopulmonary bypass, decreased systemic vascular resistance in sepsis or diastolic dysfunction in restrictive cardiomyopathy? What about age and ethnicity? In fact, the optimal inotrope relies on factors that medical science has not yet entirely elucidated—such as genomic/genetic and developmental variations in inotrope receptor distribution and function and underlying variability in host responses to varying clinical situations.