An investigation of a new activated clotting time "MAX-ACT" in patients undergoing extracorporeal circulation

Galina Leyvi, Linda Shore-Lesserson, Donna Harrington, Frances Vela-Cantos, Sabera Hossain

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Activated clotting time (ACT) is a test used in the operating room for monitoring heparin effect. However, ACT does not correlate with heparin levels because of its lack of specificity for heparin and its variability during hypothermia and hemodilution on cardiopulmonary bypass (CPB). A modified ACT using maximal activation of Factor XII, MAX-ACT (Actalyke MAX-ACT; Array Medical, Somerville, NJ), may be less variable and more closely related to heparin levels. We compared MAX-ACT with ACT in 27 patients undergoing CPB. We measured ACT, MAX-ACT, temperature, and hematocrit at six time points: baseline; postheparin; on CPB 30, 60, and 90 min; and postprotamine. Additionally, we assessed anti-Factor Xa heparin activity and antithrombin III activity at four of these six time points. With institution of CPB and hemodilution, MAX-ACT and ACT did not change significantly but had a tendency to increase, whereas concomitant heparin levels decreased (P = 0.065). Neither test correlated with heparin levels. ACT and MAX-ACT did not differ during normothermia but did during hypothermia, and ACT was significantly longer than MAX-ACT (P = 0.009). At the postheparin time point, ACT-heparin sensitivity (defined as [ACT postheparin - ACT baseline]/ [heparin concentration postheparin - heparin concentration baseline]) was greater than MAX-ACT-heparin sensitivity (analogous calculation for MAX-ACT; 520 [266 - 9366] s·U-1·mL-1 vs 468 [203 - 8833] s·U-1·mL-1; P = 0.022).

Original languageEnglish (US)
Pages (from-to)578-583
Number of pages6
JournalAnesthesia and analgesia
Issue number3
StatePublished - 2001
Externally publishedYes

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine


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