Nomogram for adjusting unfractionated heparin in adults using anti-factor Xa activity or* the aPTT

Bolus: 80 units/kg (using total body weight) Maximum = 10,000 units
Initial infusion rate: 18 units/kg/hr (using total body weight) Maximum = 2000 units/hour
If using anti-factor Xa activity* (IU/mL)	Response	If using aPTT* (seconds)^¶
0.00 to 0.09	Bolus 25 units/kg Increase infusion by 3 units/kg/hour Repeat assay in 6 hours	<40
0.10 to 0.19	Increase infusion by 2 units/kg/hour Repeat assay in 6 hours	40 to 49
0.20 to 0.29	Increase infusion by 1 unit/kg/hour Repeat assay in 6 hours	50 to 69
0.30 to 0.7	NO CHANGE (within therapeutic range) Repeat assay in 6 hours Once therapeutic for two assays, may change to once daily assays	70 to 110^¶
0.71 to 0.79	Decrease infusion by 1 unit/kg/hour Repeat assay in 6 hours	111 to 120
0.80 to 0.89	STOP INFUSION for 1 hour, then decrease by 2 units/kg/hour Repeat assay 6 hours after restarting the infusion	121 to 130
0.90 to 0.99	STOP INFUSION for 1 hour, then decrease by 3 units/kg/hr Repeat assay 6 hours after restarting the infusion	131 to 140
1.00 to 1.09	STOP INFUSION for 2 hours, then decrease by 4 units/kg/hr Repeat assay 6 hours after restarting the infusion	141 to 150
≥1.10	STOP INFUSION for 2 hours, then decrease by 5 units/kg/hr and notify clinician Repeat assay 6 hours after restarting the infusion	>150

This is one example of a weight-based heparin dosing nomogram using either anti-factor Xa activity or aPTT for therapeutic heparin dosing (eg, for acute VTE). Only one measure should be used (anti-factor Xa or aPTT); they are rarely concordant. All doses are based on actual body weight in kilograms. The initial and subsequent bolus doses, infusion rate changes, and dosing intensity based on the indication for unfractionated heparin (eg, VTE, stroke, acute coronary syndrome) should be established separately for each institution. Refer to UpToDate for additional details.

aPTT: activated partial thromboplastin time; VTE: venous thromboembolism; IU: international units.

* Only one measurement (the anti-factor Xa activity level or the aPTT) should be used; they are rarely concordant. If aPTT is used to adjust heparin, check with your laboratory to determine the aPTT values (in seconds) that would correspond to the anti-factor Xa values in this table.

¶ The therapeutic ranges for the aPTT (corresponding to an anti-factor Xa activity of 0.3 to 0.7 IU/mL) are dependent on local reagents and instrumentation and must be established by each individual institution.

Courtesy of Allison E Burnett, PharmD, PhC, CACP.

Graphic 122945 Version 4.0

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Nomogram for adjusting unfractionated heparin in adults using anti-factor Xa activity or* the aPTT