Acute porphyria is a group of rare disorders in the biosynthesis pathway of heme that can result in severe neurovisceral attacks leading to morbidity and mortality. Perioperative complications have been largely prevented due to avoidance of precipitants and early treatment of symptoms. However, these measures may not always be successful, because not all physiological stressors can be evaded. This case illustrates a porphyria attack precipitated by prolonged cardiopulmonary bypass that manifested as postoperative delayed emergence, failure to wean from mechanical ventilation, autonomic insufficiency requiring significant vasoactive agents, and, ultimately, failure to thrive. The patient passed after withdrawal of care.