Measurement of the international normalized ratio (INR) in hemodialysis patients with heparin-locked central venous catheters: evaluation of a novel blood sampling method.
BACKGROUND
Accurate 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.


METHODS
The 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).


RESULTS
INRs 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.


CONCLUSIONS
This novel sampling technique provides a convenient and simple method of monitoring INR among HD patients.
Rioux
Jean-Philippe
JP
Nephrology Division, Hôpital du Sacré-Coeur de Montréal, Montreal, Québec H4J 1C5 Canada. jp@complices.qc.ca
De Bortoli
Bruno
B
Quérin
Serge
S
Déziel
Clément
C
Troyanov
Stéphan
S
Madore
François
F
D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D001777:Blood Coagulation / Q000187:drug effects*; D001800:Blood Specimen Collection; D002405:Catheterization, Central Venous / Q000009:adverse effects / Q000295:instrumentation*; D002408:Catheters, Indwelling / Q000009:adverse effects; D004867:Equipment Design; D005260:Female; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D019934:International Normalized Ratio; D007676:Kidney Failure, Chronic / Q000097:blood / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D018962:Phlebotomy; D011237:Predictive Value of Tests; D006435:Renal Dialysis; D014859:Warfarin / Q000008:administration & dosage
D000925:Anticoagulants; D014859:Warfarin; D006493:Heparin