FIBTEM PLUS Provides an Improved Thromboelastometry Test for Measurement of Fibrin-Based Clot Quality in Cardiac Surgery Patients
BACKGROUND:
The viscoelastic functional
fibrinogen (FF) and FIBTEM assays measure the contribution of fibrin to
clot strength. Inhibition of platelet function is a necessary
precondition for these tests to work. We investigated a novel test for
measuring fibrin-based clotting, FIBTEM PLUS, in cardiac surgery and
compared it with FF and FIBTEM.
METHODS:
A prospective,
observational study was performed which included 30 patients undergoing
cardiac surgery with cardiopulmonary bypass (CPB). Blood samples were
drawn at the beginning of surgery (pre-CPB), approximately 20 minutes
before weaning from CPB and 5 minutes after heparin neutralization. FF,
FIBTEM, and FIBTEM PLUS tests were performed in duplicate for all blood
samples. Additional coagulation parameters, including platelet count,
plasma fibrinogen levels, factor XIII activity, and heparin
concentration, were also recorded for each sample.
RESULTS:
At
all time points, the lowest mean maximum clot firmness (MCF) was
observed with FIBTEM PLUS, although a statistically significant
difference between FIBTEM and FIBTEM PLUS was observed only at baseline
(mean values 22 vs 19 mm, P = 0.01; FF value for comparison: 27.7 mm).
FF maximum amplitude (MA) values were significantly higher than FIBTEM
MCF and FIBTEM PLUS MCF pre-CPB, during CPB and after heparin
neutralization (P ≤ 0.001 for FF MA versus FIBTEM MCF and for FF MA
versus FIBTEM PLUS MCF at all time points). The difference between
FIBTEM MCF and FIBTEM PLUS MCF correlated with platelet count (r =
0.46;P < 0.001), whereas differences between FF MA and FIBTEM MCF, or
FF MA and FIBTEM PLUS MCF did not (r = -0.07, P = 0.51; r = 0.16, P =
0.12, respectively). Differences between the assays were unrelated to
heparin levels, which decreased considerably after protamine
administration compared with heparin levels recorded before weaning from
CPB (decrease from 2.1 to 0.1 U/mL and from 2.8 to 0.2 U/mL for
anti-factor IIa and anti-factor Xa, respectively). Agreement between
duplicate measurements was similar with FIBTEM and FIBTEM PLUS assays
and lower with FF. Significant positive correlations were found between
MCF or MA and fibrinogen concentration (all P < 0.001); the highest
correlation was with FIBTEM PLUS MCF (r = 0.70).
CONCLUSION:
The
FIBTEM PLUS assay produces precise results. At baseline, it provides
greater inhibition of platelets than FIBTEM, but there is no meaningful
difference between FIBTEM PLUS and FIBTEM in patients with low platelet
counts.
