Use of thrombin inhibitors ex vivo allows critical care clinical chemistry and hematology testing on common specimens.
OBJECTIVE: To evaluate the suitability of the thrombin inhibitors PPACK (D-phenylalanyl-L-prolyl-L-arginine chloromethylketone) or Argatroban for anticoagulation of blood prior to critical care testing of whole blood or plasma. DESIGN AND METHODS: Initially we evaluated the effect of PPACK (0-200 microM) or Argatroban (0-590 microM) on serum glucose, urea, creatinine, calcium and electrolyte tests on two chemistry analyzers (Hitachi 717 and Ektachem 700XR). Subsequently plasma and serum from whole blood samples containing either heparin 15,000 IU/L or PPACK 75 microM or Argatroban 245 microM or no anticoagulant were tested and compared. We analysed and compared whole blood containing either PPACK 75 microM or Argatroban 245 microM or ethylenediaminetetraacetic acid (EDTA) using a Coulter STK-R hematology analyzer at intervals for 90 minutes. RESULTS: The measurement of electrolytes, urea, creatinine, calcium or glucose was unaffected by either Argatroban or PPACK in either serum or anticoagulant-specific plasmas (p > 0.05). For specimens from individual donors, serum potassium was higher than plasma potassium, irrespective of anticoagulant used. Clinically equivalent complete blood counts were achieved for 60 minutes using EDTA-whole blood, or whole blood containing 245 microM Argatroban or 75 microM PPACK. However automated differential white cell counting was not reliable with either form of thrombin inhibitor-whole blood. Argatroban-anticoagulated blood demonstrated concentration and time dependent changes in platelet counts, whereas platelet counts were stable in blood containing 75 microM PPACK for up to 90 minutes. CONCLUSION: Specimens of blood anticoagulated with either 75 microM PPACK or 245 microM Argatroban can be used for either critical care chemistry or hematology testing.