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Activated Clotting Time Measured by Hemochron Signature Elite in Adult Cardiac Surgery: Implications for Clinical
Filippo Maria Russo1, Andrea Artoni2, Mauro Cotza3
1Department of Anesthesia Critical Care and Emergency, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
Insights
The Hemochron Signature Elite (ACTe) and Hemochron Response (ACTr) activated clotting time devices show no correlation in cardiac surgery patients. Switching devices without adjusting thresholds can lead to unnecessary unfractionated heparin redosing, despite adequate anticoagulation.
Area of Science:
- Anesthesiology
- Cardiovascular Surgery
- Hematology
Background:
- Activated clotting time (ACT) monitoring is crucial for unfractionated heparin (UFH) management during cardiopulmonary bypass (CPB).
- Different ACT devices may yield varying results, potentially impacting anticoagulation management decisions.
Purpose of the Study:
- To assess the concordance between the Hemochron Response (ACTr) and Hemochron Signature Elite (ACTe) devices in adult cardiac surgery patients.
- To evaluate the correlation between ACTe measurements and anti-Xa levels.
Main Methods:
- A multicenter, prospective observational study involving 35 adult cardiac surgery patients.
- Patients received UFH, and ACTr and ACTe were measured alongside anti-Xa levels.
- Statistical analyses included Pearson correlation, linear regression, and Bland-Altman tests.
Main Results:
- No significant correlation was found between ACTe and ACTr (r = 0.157, p = 0.369).
- Limited agreement was observed (R² = 0.025), with ACTe underestimating ACTr (mean bias -20.7%).
- Anti-Xa levels correlated positively with ACTe (r = 0.587, p < 0.001) and confirmed adequate anticoagulation.
Conclusions:
- ACTe and ACTr demonstrate poor concordance in this patient population.
- Switching between ACT devices without adjusting target thresholds may result in unnecessary UFH redosing.
- Anti-Xa levels provide a reliable measure of anticoagulation, independent of ACT device discrepancies.
Objectives:
To assess concordance between Hemochron Response (ACTr) and the three-activator device Hemochron Signature Elite (ACTe) in adult cardiac surgery patients. To evaluate the correlation between ACTe and anti-Xa values.
Design:
Multicenter, prospective observational study.
Setting:
University hospitals.
Participants:
Thirty-five elective adult cardiac surgery patients.
Interventions:
Patients received 300 IU/kg of unfractionated heparin (UFH) before cardiopulmonary bypass (CPB), as recommended by guidelines. ACTe was the reference device, with ACTe target ≥ 450 seconds required to establish adequate anticoagulation during CPB. Otherwise, an additional 100 IU/kg UFH was administered, up to a maximum cumulative dose of 500 IU/kg. Blood samples for ACTe and ACTr and samples for anti-Xa activity were collected simultaneously at baseline and after each UFH administration. The analyses included Pearson correlation, linear regression, and the Bland-Altman test.
Measurements And Main Results:
Thirty-five patients were enrolled (71% male, median age 68 years). After 300 IU/kg UFH, 13 (37%) patients required a second heparin dose due to ACTe less than 450 seconds despite ACTr ≥ 450 seconds and 5 (14%) due to ACT less than 450 seconds with both devices. Following the second UFH administration, 10/18 (55%) patients still did not reach the target ACTe despite an ACTr ≥ 450 seconds, requiring a third UFH administration. ACTe and ACTr showed no correlation (r = 0.157, p = 0.369). Linear regression analysis demonstrated limited agreement (R2 = 0.025). Bland-Altman analysis indicated a mean bias of -20.7% (95% CI -75.28% to +35.5%), with ACTe underestimating ACTr. The predicted ACTe, corresponding to an ACTr threshold of 450 seconds, was 357 seconds. Anti-Xa levels always exceeded 4 IU/mL, confirming adequate anticoagulation in all cases and were positively correlated to ACTe (r = 0.587, p < 0.001). Predicted ACTe interval corresponding to anti-Xa levels of 4 IU/mL was 263 to 515 seconds.
Conclusions:
ACTe and ACTr showed no correlation. Switching devices without adjusting ACT thresholds leads to unnecessary UFH redosing, despite adequate anticoagulation as measured by anti-Xa levels.
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