29, 42, 88
The schedule's most frequent test, the ACT, is the one Saifee 2020 found least interpretable on a circuit — r=0.99 with coagulation factors, insensitive to heparin below 0.5 U/mL, and correlated with neither when multiple parameters change.
Free haemoglobin is the only haemolysis marker with a stated frequency in either schedule. The 4-hour post-dose-change anti-Xa rule is the part most often omitted in practice. Neither schedule claims an evidence base — the frequencies are convention, and the panel should be audited against the daily phlebotomy volume it generates.
The ELSO Red Book 6th edition adult cardiac chapter reproduces a monitoring schedule (Table 28-2, adapted from McMichael): ACT every 1 to 2 hours (hourly until the heparin dose has been unchanged for 6 hours, then 2-hourly); aPTT every 6 to 12 hours; anti-factor Xa every 6 to 12 hours OR 4 hours after each heparin change; platelets every 6 to 12 hours; INR, fibrinogen and full blood count every 12 to 24 hours; antithrombin daily or as needed; PLASMA FREE HAEMOGLOBIN DAILY; thromboelastometry daily or as needed for bleeding or thrombotic complications. The neonatal chapter (Table 9-1) gives a parallel schedule with targets: anti-Xa 0.3 to 0.7 u/mL, platelets over 50,000 to 100,000/uL, haematocrit over 35 to 40 percent, antithrombin over 50 to 80 percent.
Laboratory monitoring schedule