Thromboelastography with citrated blood: comparability with native blood, stability of citrate storage and effect of repeated sampling

Thromboelastography (TEG) with recalcified citrate blood is used as an alternative to native blood, but there is insufficient data regarding sample reliability and stability over time. Thus, TEG parameters of freshly drawn native blood were compared with those of recalcified citrated blood without celite in 10 healthy subjects, and the effect of repeated sampling over 240-min storage was evaluated. All TEG parameters following citrate storage remained stable between 30 min [clot formation time (k) = 7.2 +/- 0.6 min; maximum amplitude (ma) = 48.5 +/- 1.9 mm] and 2 h (k = 7.1 +/- 0.6 min; ma = 46.2 +/- 2.5 mm) after initial sampling, but were not comparable with native blood (k = 9.3 +/- 0.7 min; ma = 43.5 +/- 2.5 mm) at any time point. TEG parameters of repeatedly sampled citrated blood had a significant overall hypercoagulable trend throughout 4 h following sampling. In conclusion, in order to achieve reproducible results, citrated blood without celite may be utilized between 30 min and 2 h following sampling, but in normal subjects the TEG parameters following citrate storage are not comparable with native blood, possibly because of incomplete inhibition of the activation of the coagulation cascade. Thus, citrated blood can be used as a surrogate of native blood in assessing coagulation using TEG, but if repeated sampling is used the trend in hypercoagulability must be considered. (C) 2004 Lippincott Williams Wilkins.