Smith and Wheeler developed a protocol for dosing unfractionated heparin based on patient weight and the plasma anti-factor Xa activity. The authors are from William W. Backus Hospital and the University of Connecticut in Norwich, Connecticut.
Parameters:
(1) actual body weight of the patient in kilograms
(2) plasma anti-factor Xa activity in units/mL
Initial intravenous bolus: 26 units per kg
Initial intravenous infusion: 15 units per kg per hour
Anti-Factor Xa activity is measured every 6 hours until endpoint is reached, then every 24 hours.
Endpoint: 2 consecutive anti-Factor Xa results between 0.3 to 0.7 units/mL
Anti-Factor Xa Activity
Step 1
Step 2 (units/kg/h)
< 0.2 units/mL
Give initial bolus again.
Infusion + 4 units/kg/h
0.2 to 0.29 units/mL
Infusion + 2 units/kg/h
0.3 to 0.70 units/mL
Continue Infusion Rate
0.71 to 0.80 units/mL
Infusion - 1 unit/kg/h
0.81 to 0.99 units/mL
Infusion - 2 units/kg/h
>= 1.00 units/mL
Hold infusion for 1 hour.
Infusion - 3 units/kg/h
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