Background: The mainstay of treatment for symptomatic pulmonary embolism  (PE) is anticoagulation (AC).  Patients with higher-risk PE may require advanced interventions such as thrombolytic therapy, surgical thrombectomy, or even extracorporeal membrane oxygenation (ECMO). Because of its short half-life and availability of a reversal agent, unfractionated heparin (UFH) is commonly used when percutaneous or surgical interventions are being considered. The standard weight based dosing of UFH is 80U/kg bolus followed by an infusion started at 18U/kg/hr, titrated to a target activated partial thromboplastin time (aPTT) of 1.5 to 2.5x the control range or an anti-Xa level of 0.3 to 0.7u/mL. The efficacy of UFH in reaching and maintaining appropriate anticoagulation is poorly understood. REBEL Cast 125: 1st 48 Hours of PE Management – How Good is Unfractionated Heparin? Click here for Direct Download of the Podcast Paper: Prucnal CK et al. Analysis of Partial Thromboplastin Times in Patients With Pulmonary Embolism During the First 48 Hours of Anticoagulation With Unfractionated Heparin. Acad Emerg Med 2020. PMID: 31625654 Clinical Question: How effective is UFH in obtaining appropriate anticoagulation during the first 48 hours of administration to patients with acute PE? What They Did: Retrospective analysis of a PE response team (PERT) data base Single, large, urban academ