Clinical Chemistry, Vol 41, 1038-1041, Copyright © 1995 by American Association for Clinical Chemistry

D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK): alternative anticoagulant to heparin salts for blood gas and electrolyte specimens

ME Lyon, JS Fine, PJ Henderson and AW Lyon
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.

D-Phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK), a selective thrombin inhibitor, was evaluated as an alternative anticoagulant to lithium heparin (LiHep) for blood gas and whole-blood electrolyte analyses. Initial studies in serum revealed a negative proportional bias for ionized calcium (iCa) concentration measured in the range of increasing concentrations of LiHep (-0.02 mmol/L iCa per 33 kIU/L), whereas no bias in iCa concentration was detected with increasing concentrations of PPACK. No anticoagulant-dependent changes in serum sodium, potassium, chloride, glucose, lactate, ionized magnesium, or pH were detected with either PPACK or LiHep. Similarly, no bias was observed in the measurement of whole-blood PO2, PCO2, pH, or sodium or potassium concentrations with either anticoagulant. Whole blood anticoagulated with LiHep (33 kIU/L) demonstrated a consistent - 0.06 +/- 0.01 mmol/L bias for iCa compared with a nonanticoagulated whole-blood control. In comparison, no iCa bias was observed with PPACK- anticoagulated whole blood. We conclude that PPACK has ideal bias-free properties as an anticoagulant in analyses for blood gases, electrolytes, and iCa.