RESIDUAL ORAL ANTICOAGULANT LEVELS SUPPORT TIMELY HIP FRACTURE SURGERY IN ADULT HIP FRACTURE PATIENTS RECEIVING PRE-INJURY ANTICOAGULATION: A PILOT STUDY

Anticoagulation use for prevention of thrombotic and embolic adverse events is increasingly common. As the global population ages, hip fracture incidence is also increasing. Up to 40% of hip fracture patients are taking an oral anticoagulant (OAC) at the time of their injury. Pre-injury OAC use can result in delayed time-to-surgery (TTS) and increased complications and mortality. However, anesthetic and bleeding considerations must also be balanced. There are currently no guidelines for safe and timely surgical management of hip fracture patients receiving pre-injury OAC. The aim of this pilot study was to evaluate the residual pre-operative OAC levels in patients requiring urgent hip fracture surgery. This is a planned subgroup analysis of an ongoing single centre, prospective cohort study, where adult patients 50 years or older presenting with a hip fracture requiring urgent surgical intervention and on pre-injury OAC were included. Following informed or surrogate consent, participants underwent a blood draw at the time of hospital admission, as well as pre-operatively if there was a delay beyond 24 hours between admission and surgery. The primary outcome measure was residual pre-operative OAC level, described relative to time from last dose, analyzed using medication-specific OAC reagents and pre-established normative curves (STA Compact Max hemostasis analyzer, Stago). Participants were dichotomized to those with an elevated pre-operative OAC level and those who did not. Renal function, co-morbidities, post-operative adverse events, PT, and blood transfusions were collected. Descriptive statistics and independent samples t-tests were used comparing between those who had elevated pre-operative OAC level and those who did not. A total of 10 patients who required urgent hip fracture surgery and were taking pre-injury apixaban were included, with a mean age of 84.4 (SD=8.9) years, and with 60% being female. Nine patients had normal renal function, as defined by a creatinine clearance of 50ml/min or greater at the time of hospital admission. The mean time from last does to the time of the pre-operative blood draw was 37.3 (SD=31.0) hours. The mean residual apixaban level pre-operatively was 54.3 (SD=46.7) ng/mL, which was above the normal reference range (0-23 ng/mL); however, there were three patients with normal pre-operative apixaban levels. Three patients had both an admission and a pre-operative residual OAC level measured, which demonstrated a decrease from abnormally high (mean=71.3 ng/mL) to within a normal (mean = 22.3 ng/mL). There was a significant decrease in pre-operative hemoglobin (mean=129.4 [SD=14.5]) compared with post-operative hemoglobin (mean=109.7 [SD=24.0]; p < 0 .05), with 40% of patients requiring a blood transfusion. There were no cardiac, pulmonary, or thrombosis-related adverse events within the 3-month follow-up. There were no differences in change in hemoglobin, need for blood transfusion, or PT between those with elevated pre-operative OAC level and those with normal levels. Safe and timely surgical care of hip fracture patients on OACs is a priority, given the potential to decrease morbidity and mortality. This study supports that patients with normal pre-operative renal function who undergo surgery within 48 hours from their last OAC dose did not experience any additional adverse event risk.