The Annals of thoracic surgery
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Activated clotting time (ACT) was used in 300 consecutive patients undergoing cardiac operations to determine the adequacy of heparin reversal. Mean ACT prior to protamine sulfate administration was 9 minutes 40 seconds. ⋯ Normal values for ACT usually coincided with clotting in the operative field. ACT proved to be a reliable guide to protamine sulfate administration.