Pediatric cardiac surgery patients commonly suffer from alterations in vascular tone in the early post-operative period. Pharmacologic manipulation of systemic vascular resistance (SVR) can be complex in a variety of special patient situations including extremes of age, presence of left sided valvar lesions and the use of mechanical circulatory support. Familiarity with how these special circumstances alter SVR and the response to pharmacologic intervention will allow for tailored therapy and hopefully, optimized outcomes. This article addresses the eighth topic of the special issue entitled "Pharmacologic strategies with afterload reduction in low cardiac output syndrome after pediatric cardiac surgery".