D-PHENYLALANYL-L-PROLYL-L-ARGININE CHLOROMETHYL KETONE (PPACK) - ALTERNATIVE ANTICOAGULANT TO HEPARIN SALTS FOR BLOOD-GAS AND ELECTROLYTE SPECIMENS

D-Phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK), a sele ctive thrombin inhibitor, was evaluated as an alternative anticoagulan t to lithium heparin (LiHep) for blood gas and whole-blood electrolyte analyses. Initial studies in serum revealed a negative proportional b ias for ionized calcium (iCa) concentration measured in the range of i ncreasing concentrations of LiHep (-0.02 mmol/L iCa per 33 kIU/L), whe reas no bias in iCa concentration was detected with increasing concent rations of PPACK. No anticoagulant-dependent changes in serum sodium, potassium, chloride, glucose, lactate, ionized magnesium, or pH were d etected with either PPACK or LiHep. Similarly, no bias was observed in the measurement of whole-blood Po-2, Pco(2), pH, or sodium or potassi um concentrations with either anticoagulant. Whole blood anticoagulate d with LiHep (33 klU/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 whol e blood. We conclude that PPACK has ideal bias-free properties as an a nticoagulant in analyses for blood gases, electrolytes, and iCa.