Sampling for international normalized ratios in patients on hemodialysis with central venous catheters

The primary objectives of this study were to evaluate the effect of varying heparin concentrations on International Normalized Ratio values and to assess the accuracy of these values deter mined through the arterial line of the dialysis circuit Twenty-two patients on hemodialysis with central venous catheters were studied After a peripheral venipuncture, timed samples from the arterial line of the hemodialysis circuit were obtained after dialysis was initiated and prior to initiating heparin. Assays for coagulation parameters were performed. There was no signifcant difference in any coagulation parameter measured from the arterial line samples compared to the venipuncture samples. Serial heparin dilutions in vitro demonstrated that residual amounts of heparin in the central venous catheter may falsely elevate International Normalized Ratio values. This study demonstrates that accurate International Normalized Ratio values in patients on hemodialysis with heparinized central venous catheters can be obtained ericiently and cost-effectively from the arterial line within 1 minute of dialysis initiation.