Intravenous Heparin During Radiocephalic Arteriovenous Access Creation: A Target Trial Emulation
Patrick Heindel1, James J Fitzgibbon1, Eric Secemsky2, C. Keith Ozaki1, Mohamad A Hussain1
1Brigham and Women's Hospital, Boston, MA;2Beth Isreal Deconess Medical Center, Boston, MA
INTRODUCTION: The effectiveness and safety of intraoperative heparin during open autogenous hemodialysis access creation is unknown, and practice patterns vary widely.
METHODS: Using pooled data from two 2014-2019 international multicenter hemodialysis access creation randomized trials (PATENCY-1 and -2; ClinicalTrials.gov NCT02110901 and NCT02414841), we emulated a new randomized trial to assess the effect of intravenous (IV) heparin administration during creation of radiocephalic autogenous arteriovenous access (RC-AVF). Target trial emulation is an emerging framework for extending causal inference principles used in randomized trials to the analysis of non-experimental data. All patients randomized in the PATENCY trials undergoing RC-AVF creation were eligible for emulated trial enrollment. The intervention was IV heparin use (vs. none) during the index case. Treatment allocation and start of 30-day follow-up occurred on postop-day-zero. The primary effectiveness and safety outcomes were access thrombosis and bleeding events, respectively. Bleeding events were defined as any incisional or extra-incisional hemmorhage or hematoma. We emulated randomization and accounted for selection bias due to loss-to-followup with inverse probability weighting. The treatment propensity score was estimated using the pre-exposure covariates age, sex, body-mass-index, tobacco use, hemodialysis status, prior access failure history, medical comorbidities, anticoagulation use, antiplatelet use, access location (snuffbox, wrist, or forearm), regional anesthesia, vessel diameter, use of heparinized saline, central venous catheter presence, calendar time, trial site and enrollment (PATENCY-1 or -2). The propensity score for loss-to-followup was estimated using additional time-varying covariates of time since enrollment and number of access interventions. Marginal risks were estimated using propensity score weighted parametric time to event analysis and 95% confidence intervals were generated with 500 resamples of the non-parametric bootstrap.
RESULTS: A total of 914 patients were enrolled; 61% received IV heparin. Mean (SD) age was 58 (13) years, 22% were female, and 45% were on hemodialysis at access creation. About half (47%) of patients were taking an anti-platelet and 9% were taking an anticoagulant. After inverse probability weighing, the maximum absolute standardized mean difference in confounders was 0.037 (0.40 unweighted). The risk of access thrombosis was lower in the heparin group throughout the 30-day followup, with an absolute risk difference (95% CI) of -0.3% (-0.9-0.0) at 2 days and -2.8% (-6.0-0.4) at 30 days (risk ratio 0.73, 95% CI 0.48-1.06, Figure). No difference in the risk of bleeding events was observed, with a risk at 30 days of 2.4% (1.3-3.6%) after heparin and 2.8% (1.2-4.7%) without heparin (risk ratio 1.01, 95% CI 0.40-2.11, Figure). Incisional hematoma was the most common bleeding event (75%), and only one patient required operative intervention (hematoma evacuation) for bleeding.
CONCLUSIONS: During RC-AVF creation, IV heparin does not seem to increase bleeding risk and may decrease risk of early thrombosis. 
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