Authors: van Haeren MMT, et al.
Anesthesia & Analgesia. September 05, 2025. doi:10.1213/ANE.0000000000007753
This substudy compared the ROTEM Delta and ROTEM Sigma devices during cardiac surgery, focusing on clotting time (CT) EXTEM values in the presence of high-dose heparin. Eighty-six patients undergoing thoracic aortic surgery had paired ROTEM measurements before heparinization and during cardiopulmonary bypass.
Results showed that CT EXTEM increased significantly more with the Sigma than with the Delta device after heparinization (mean increase 24 vs 17 seconds). On average, Sigma measured CT EXTEM at 101 seconds during bypass, crossing the 100-second threshold in 38% of patients, compared with 96 seconds and 30% for Delta. This suggests Sigma is more sensitive to heparin, likely due to differences in reagents between devices. Additional differences were observed in MCF EXTEM and FIBTEM values, with Sigma yielding consistently lower FIBTEM values.
What You Should Know
• ROTEM Sigma shows greater prolongation of CT EXTEM under heparin than Delta.
• More patients cross the 100-second transfusion threshold with Sigma.
• Device reagent differences likely explain the discrepancy.
• Using Delta-based transfusion cutoffs with Sigma may trigger unnecessary plasma or PCC transfusions.
• Local calibration of Sigma thresholds is recommended.
Practice Implication
Institutions transitioning from ROTEM Delta to Sigma should recalibrate transfusion algorithms, especially for heparinized patients. Applying Delta-based thresholds risks overtreatment. Alternatively, delaying viscoelastic testing until after protamine reversal may reduce misinterpretation, though calibration of Sigma values remains essential.
References
van Haeren MMT, et al. Anesth Analg. 2025. doi:10.1213/ANE.0000000000007753
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