Took care of a patient who came to OR for a redo-sternotomy and triple valve replacement on ECMO.
Scroll down to see how we managed the patient’s possible HIT. The patient had a low score on her 4Ts assessment. Therefore, we opted to move forward before the functional assay came back with results as the patient was in dire need of triple valve replacement.
The goals of treatment for HIT are threefold: Interrupt the pathological immune response, inhibit the uncontrolled generation of thrombin, and minimize the complications.
Cessation of heparin alone does not sufficiently reduce the risk of thrombosis. The next step in management targets the uncontrolled generation of thrombin with the use of direct thrombin inhibitors (DTIs). Argatroban is preferred in patients with renal insufficiency, whereas lepirudin is the drug of choice for patients with liver disease. Bivalirudin is another hirudin analog that differs from lepirudin in that it is hemodialyzable and primarily undergoes enzymatic elimination. Its half-life is the shortest, 20-25 minutes, making bivalirudin the safest option since there are no reversal agents available.
All three agents can be monitored using the activated partial thromboplastin time (aPTT) to levels of 1.5 to 2.0 above baseline. Once the platelet count has increased to a minimum of 150,000/µL bridging therapy to warfarin is essential for the safe transition from DTIs.
Iloprost is a prostacyclin analogue that reversibly inhibits platelet aggregation. Plasma exchange was successful in reducing anti-P4/heparin antibodies and allowed for the restoration of a normal platelet count, essentially reversing the disease.
Intraoperative infusion of epoprostenol sodium for patients with heparin-induced thrombocytopenia undergoing cardiac surgery. The Japanese Journal of Thoracic and Cardiovascular Surgery. , Volume 54, Issue 8, pp 348–350.
Bivalirudin for Cardiopulmonary Bypass in the Setting of Heparin-Induced Thrombocytopenia and Combined Heart and Kidney Transplantation— Diagnostic and Therapeutic Challenges. Journal of Cardiothoracic and Vascular Anesthesia 31 (2017) 354–364.
Anticoagulation during Cardiopulmonary Bypass in Patients with Heparin-induced Thrombocytopenia Type II and Renal Impairment Using Heparin and the Platelet Glycoprotein IIb–IIIa Antagonist Tirofiban. Anesthesiology 2 2001, Vol.94, 245-251.
What we did:
- Prior to giving heparin, we started alprostadil (PGE1) infusion at 1mcg/min and increased the doseage as tolerated to 5mcg/min. We did offset the hypotension with levophed and vasopressin.
- We gave our routine dose of heparin.
- No heparin resistance noted. Because this would be a long pump run, we opted to give an antifibrinolytic infusion as well as bolus.
- This patient required higher than normal amounts of pressors and ultimately received methylene blue to help with vasoplegia.
- We reversed the heparin with protamine and stopped the PGE1 at that time.