TABLE 2.

Heparin resistance: Definition criteria

Type of heparin	Heparin dose		Anti‐Xa (IU/mL)
Sodium or calcium UFH	>35 000 IU/day*	AND	≤0.7
Calcium UFH	>15 000 IU/day	AND	≤0.2
LMWH	>200 IU/Kg b.w.	AND	≤0.6
LMWH	>4000 IU/day	AND	≤0.2

^*Patients who exceeded the therapeutic heparin dosage without reaching the expected anti‐Xa level and those exceeding the prophylactic heparin dosage without reaching the anti‐Xa prophylactic range were considered resistant. Asterisk denotes criteria included in Ref. 18, while the other listed criteria are defined in‐house.

Abbreviations: b.w., body weight; LMWH, low molecular weight heparin; UFH, unfractioned heparin.