• Jean-Philippe Rioux, Bruno De Bortoli, Serge Quérin, Clément Déziel, Stéphan Troyanov, and François Madore.
• Nephrology Division, Hôpital du Sacré-Coeur de Montréal, Montreal, Québec H4J 1C5 Canada. jp@complices.qc.ca
• J Vasc Access. 2009 Jul 1;10(3):180-2.

BackgroundAccurate measurement of the international normalized ratio (INR) may be difficult in hemodialysis (HD) patients with heparin-locked central catheters. Blood contamination with locking solutions may interfere with INR measurement when samples are collected directly from the catheter.MethodsThe aim of our study was to evaluate a novel sampling method for the measurement of INR in HD patients with heparin-locked central catheters. This novel method consists of measuring the INR directly from the dialysis circuit (arterial bloodline sample port) after 1 hr of treatment regardless of heparin administration during dialysis. We compared this method to the gold standard (peripheral venipuncture prior to dialysis) using the paired t-test. We included 30 patients (23 with warfarin therapy and 7 without).ResultsINRs obtained using the novel sampling method were only minimally overestimated compared to venipuncture values (mean INR overestimation: 0.2 +/- 0.2). This overestimation was not clinically significant and did not lead to changes in warfarin prescription for any of the patients. Correlation tests confirmed the influence of heparin administration on INR overestimation (R=0.4; p=0.05). This influence was present mostly among patients receiving more than 100 Units/kg of heparin during their treatment.ConclusionThis novel sampling technique provides a convenient and simple method of monitoring INR among HD patients.

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