Acute physiologic changes after bypass graft surgery may temporarily result in reduced drug elimination and dosing requirements for the desired effect. Substantially lower doses for drugs such as the direct thrombin inhibitor argatroban may need to be considered when initiating therapy soon after surgery if the therapeutic window is narrow and impaired liver, kidney, or cardiac function is present. Initial dosing approaches, with follow-up infusion rate adjustments and allowances for the extended time needed to establish and maintain an activated partial thromboplastin time value in the target ratio range, also need to consider the risk of thrombosis or bleeding complications. The duration of reduced dosing may depend on several variables, and, as systems recover, the dosage may need to be adjusted upwards. Retrospective analysis for identifying heparin-induced thrombocytopenia may be difficult in situations where other causes of thrombocytopenia are present, suggesting that posttest scoring methods also be considered to confirm its presence until better, validated methods become available.