Protamine, a protein isolated from salmon sperm, is used to reverse the anticoagulating effects of heparin during cardiac surgery involving cardiopulmonary bypass (CPB), but it can cause hemodynamic depression.[1] This protamine-induced circulatory suppression is related to 3 mechanisms: myocardial depression caused by tumor necrosis factor-alpha (TNF-α),[2] vasodilation induced by nitric oxide,[3] and pulmonary hypertension mediated by arachidonic acid cascade.[4]. This evidence concerns the gene TNF and pulmonary arterial hypertension.