Arterial and venous Thrombelastograph (R) variables differ during cardiac surgery

The Thrombelastograph(R) (TEG(R), Haemoscope Corp., Skokie, IL) coagulation analyzer is an effective point-of-care monitor for routine clinical practi ce and clinical research. Prior investigators have used either arterial or venous samples of blood for TEG(R) measurements. We conducted this prospect ive cohort study to determine potential differences in TEG(R) variables bet ween arterial and venous blood samples. Arterial and venous samples were dr awn from 40 cardiac surgical patients, yielding 134 pairs for comparison. T wenty-nine comparisons (control) were between arterial and arterial samples and were not significantly different. For the arterial and venous comparis ons (n = 105), mean (+/- SD) arterial and venous values were the following: reaction time, 10 +/- 2 mm. vs 13 +/- 4 mm, P = 0.004; maximum amplitude, 59 +/- 9 mm vs 49 +/- 12 mm, P < 0.001; <alpha> angle, 61 +/- 10 degrees vs 51 +/- 14 degrees, P < 0.001; K, 5 +/- 2 mm vs 8 +/- 4 mm, P = 0.007; and lysis, 2.5 +/- 1.7 vs 2.5 +/- 2.0 (not significant), arterial versus venous , respectively. Arterial blood samples demonstrated TEG(R) values reflectin g stronger (larger maximum amplitude) and faster (shorter reaction time and K value, wider a angle) clot formation. The results suggest that users of TEG(R) coagulation analyzers should be consistent with the site of blood sa mpling given the potential differences obtained.