Ashley West, BCCCP, BCPS, PharmD
Yale New Haven Health
New Haven, Connecticut
Disclosure information not submitted.
Madiha Shah
Clinical Pharmacist
Yale New Haven Hospital, United States
Disclosure information not submitted.
Diana Lemieux, BCCCP, PharmD
Clinical Pharmacy Specialist
Yale New Haven Hospital, United States
Disclosure information not submitted.
Title: Identification of Pseudo-Heparin Resistance in Critically Ill Patients with COVID-19
Case Report Body:
Introduction:
Studies have shown that patients with COVID-19 have elevated factor VIII and fibrinogen levels, which can artificially lower activated partial thromboplastin time (PTT). In hospitals using PTT to monitor unfractionated heparin (UFH) activity, falsely low PTT can lead to inappropriate increases of UFH rates, thereby increasing bleeding risk. Furthermore, patients with COVID-19 may have an increased incidence of pseudo-heparin resistance (PHR), a condition where falsely low PTTs lead to UFH rates greater than 35,000 units/day, making UFH seem ineffective when it is actually therapeutic. Discordance between PTT and anti-Xa (aXa) levels (subtherapeutic PTT with therapeutic aXa or therapeutic PTT with supratherapeutic aXa) can be used to identify PHR. We present three cases of patients at least 18 years old (yo) who were found to have discordant PTT and aXa levels obtained from the same blood sample while on UFH.
Description:
Patient A was a 68 yo male on UFH for pulmonary embolism (PE) treatment with rates escalating from 20,800 to 45,800 units/day over 23 days. Patient B was a 61 yo male on UFH for PE treatment with rates escalating from 35,400 to 60,000 units/day over 7 days. Patient C was a 55 yo male on UFH for STEMI and prothrombotic risk with rates escalating from 16,600 to 46,800 units/day over 21 days. AXa levels were checked for patients A and B following bleeding events despite seemingly therapeutic PTT levels. AXa levels were checked for patient C for continuously subtherapeutic PTT despite high rates of UFH. All three patients had COVID-19, had a body mass index in the 20s, and required blood transfusions while on UFH.
Discussion:
Patients with COVID-19 are at increased risk of PHR. Failure to identify PHR can lead to inappropriately high rates of UFH and increased risk of bleeding events. Following identification of these three patients, clinical pharmacists at this large academic medical center were educated on PHR to increase awareness and promote earlier detection. Furthermore, and aXa monitoring protocol for UFH is actively being piloted to enhance safety for this patient population.