Milrinone-induced platelet inhibition in patients supported on veno-aterial extracorporal membrane oxygenation: a case series

ABSTRACT

Case Report Purpose: Milrinone is an inodilator that is used in the treatment of cardiogenic dysfunction and shock. It causes increased cardiac output by stimulating myocardial contractility, enhancing cardiac relaxation, and reducing afterload via phosphodiesterase III inhibition, preventing cyclic adenosine monophosphate (cAMP) degradation. Increased cAMP concentrations are known to inhibit platelet aggregation. Veno-arterial-extracorporeal membrane oxygenation (VA-ECMO) is an extracorporeal treatment option for inotrope-refractory cardiogenic shock and is often used in conjunction with inodilators. Often, patients supported on ECMO require systemic anticoagulation to prevent clotting complications. Therefore, thromboelastography (TEG) with platelet mapping is used to help gauge a patient's clotting status and gives clinicians information about the degree of platelet inhibition present. We present the case of two patients, both supported on VA-ECMO, who developed platelet inhibition with clinically significant bleeding while on milrinone, requiring the cessation of the milrinone infusion. Cases First, we present an adult female in her fourth decade of life who required VA-ECMO for Covid-19 ARDS and cardiogenic shock. TEG platelet mapping was obtained for clinically significant bleeding from her trachea and gastrointestinal tract. Ten days after starting milrinone, adenosine-5'-diphosphate (ADP) inhibition was elevated at 67.4% and arachidonic acid (AA) inhibition normal at 1.8%. Twenty days after starting milrinone, ADP inhibition was 93.3% and AA inhibition was 76.4%. Milrinone discontinued and repeat TEG platelet mapping (10 days after discontinuation) showed ADP inhibition of 76.8% and AA inhibition of 0%. Her lowest ADP inhibition was 41.9%, approximately 1 month after milrinone discontinuation. Milrinone again attempted and ADP inhibition was 87.9% and AA inhibition 89.2% within 24 hours of initiation. No data available for platelet inhibition prior to starting milrinone. Next, we present a 9 year old female with acute myeloid leukemia who required VA-ECMO for septic shock. Initial TEG platelet mapping, obtained 2 days after milrinone initiation, showed ADP inhibition of 43.6% and AA inhibition of 98.7%. Two days after discontinuation of milrinone, her ADP inhibition was 19.6% but AA inhibition remained elevated at 91.9%. However, after 4 days off milrinone, her ADP inhibition was normal at 15.5% and AA inhibition mildly elevated at 33.6%. No data available for platelet inhibition prior to starting milrinone. Conclusion(s) Milrinone is a known platelet inhibitor due to increased intracellular cAMP concentrations. For patients on ECMO and milrinone, care should be given to the degree of platelet inhibition and potential risk of clinically significant bleeding. Further studies are needed to further investigate the correlation between milrinone, platelet inhibition, and clinically significant bleeding in ECMO patients. Copyright © 2023 Southern Society for Clinical Investigation.