(1451) Thrombocytopenia With Concomitant CRRT: Heparin Allergy or HIT the Brakes

Introduction: Acute kidney injury necessitating continuous renal replacement therapy (CRRT) is a common complication for critically ill patients. Thrombocytopenia etiology is often challenging to determine and CRRT has been associated with its development . A 4T score can help determine pre-test probability of heparin-induced thrombocytopenia (HIT) for thrombocytopenic patients receiving heparin products. However, CRRT impacts three-fourths of the criteria assessed in the 4T score, increasing the likelihood of inappropriately collecting a costly, resource-intensive laboratory test.

Methods: Retrospective observational study of surgical patients between January 1 2023 and 2024 receiving CRRT for >24 hours. Patients were excluded if platelets on admission were < 150,000 uL or non-surgical patients. Data collected included duration of CRRT; platelets on admission, discharge, initiation and completion of CRRT; HIT antibody sent; optimal density; concomitant anticoagulation. Due to the small number of patients with a HIT antibody, only descriptive statistics could be performed.

Results: A total of 42 courses, for 38 patients were included. Patients received an average of 8.1 days of CRRT. Platelets were a median of 258,000uL on admission and nadired at 126,500uL. The mean drop occurred 4.9 days into CRRT. Within 72 hours of discontinuation, platelets increased to a median of 243,220. Six patients (15.8%) had a HIT antibody sent, with average platelet nadir of 62,833uL. No HIT antibodies were positive (average optical density of 0.076).

Conclusions: There are many reasons platelets decline, making elucidating the precise source of the blood dyscrasia a challenge. A 4T score guide pre-test probability of HIT based on the degree and timing of platelet decline, thrombosis, and other causes of thrombocytopenia. CRRT can skew the pre-test assumption of HIT towards pursuing an expensive, labor-intensive laboratory test. Of the 6 patients from whom a HIT antibody was collected, only two were not treated for HIT with a non-heparinoid anticoagulant, indicating the clinical suspicion for HIT was low enough in these patients to not avoid heparin. In the setting of CRRT, additional clinical judgement should be exercised in the setting of thrombocytopenia to decrease unnecessary strain on the patient and healthcare system.