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Heparin Dosing Calculator

All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgment. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.   Read the disclaimer
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Select desired weight preference based on local protocol

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Standard Infusion Bag

DVT /PE Guidelines

If DVT/PE with risk factors was chosen, please specify dosing guidelines
Initial Load: units/kg    Initial Rate: units/kg/hr
Safety option: Modify if necessary- Used for DVT/PE if selected.

Limit the maximum initial bolus to: units  
Limit the maximum initial infusion rate to: units/hr

Unstable angina / NSTEMI Guidelines

IF UA / NSTEMI selected above, Fill in the section below. 
UA / NSTEMI Limits:
Initial Load: units/kg   Initial Rate units/kg/hr
Max initial bolus: units.  Max initial infusion rate: units/hr
 
In general, weight based nomograms are much more likely to achieve therapeutic levels  within 48 hours. It is important to note that the most critical factor in reducing the risk of recurrent thromboembolism is reaching a therapeutic PTT within 24-48 hours. Traditional  regimens that normally begin with 1000 u/hr are less likely to achieve this goal.   See heparin overview below...
 

 

 

Heparin Overview
Suspected Venous thromboembolic disease *Obtain baseline APTT, prothrombin time (PT), CBC count
*Check for contraindication to heparin therapy
*Order imaging study
*Consider giving heparin, 5,000 IU IV
Confirmed venous thromboembolic disease Rebolus with heparin, 80 IU/kg IV; start maintenance infusion at 18 IU/kg

Check APTT at 6 h, to maintain a range corresponding to a therapeutic heparin level

Check platelet count between days 3 and 5

Start warfarin therapy on day 1 at 5 mg; adjust subsequent daily dose according to the INR

Stop heparin therapy after > 4 to 5 d of combined therapy, when INR is > 2.0

Anticoagulate with warfarin for > 3 mo (goal INR 2.5; range, 2.0 to 3.0)

Weight Based heparin nomogram

APTT Dose Change
Units/kg/hr
Additional action Next APTT
< 35 (1.2 x mean normal) +4 Rebolus with 80 IU/kg 6
35 to 45 (1.2 to 1.5 x mean normal) +2 Rebolus with 40 IU/kg 6
46 to 70‡ (1.5 to 2.3 x mean normal) 0 ------ 6  §
71 to 90 (2.3 to 3.0 x mean normal) -2 ------ 6
> 90 (> 3 x mean normal) -3 Stop infusion 1 hour 6
*Initial dosing: loading, 80 IU/kg; maintenance infusion: 18 IU/kg/h (APTT in 6 hours).
†The therapeutic range in seconds should correspond to a plasma heparin level of 0.2 to 0.4 IU/mL by protamine sulfate, or 0.3 to 0.6 IU/mL by amidolytic assay; when APTT is checked at 6 h or longer, steady-state kinetics can be assumed.
§Repeat APTT every 6 h during the first 24 h; thereafter, monitor APTT once every morning, unless it is outside therapeutic range.
1. Raschke RA, ReillyBM, Guidry JR, Fontana JR, Srinivas S. The weight-based heparin dosing nomogram compared with a "standard care" nomogram: a randomized controlled trial.  Ann Intern Med 1993; 119:874-81.

2. Hull, RD, Raskob, GE, Rosenbloom, D, et al (1992) Optimal therapeutic level of heparin therapy in patients with venous thrombosis. Arch Intern Med 152,1589-1595

3. Elliot, GC, Hiltunen, SJ, Suchyta, M, et al (1994) Physician-guided treatment compared with a heparin protocol for deep vein thrombosis. Arch Intern Med 154,999-1004.

4. Flaker, GC, Bartolozzi, J, Davis, V, et al (1994) Use of a standardized heparin nomogram to achieve therapeutic anticoagulation after thrombolytic therapy in myocardial infarction. Arch Intern Med 154,1492-1496

Adjuctive therapy with heparin following thrombolysis in acute myocardial infarction
IV heparin with alteplase, reteplase, or tenecteplase:  Standard-dose heparin  (bolus of 5,000 IU, followed by 1,000 IU/h (grade 1C); or weight-adjusted dosing (bolus of 60 IU/kg [4,000 IU maximum] followed by 12 IU/kg [1,000 IU/h maximum] (grade 2C); adjust dosing to maintain an APTT of 50 to 70.  Heparin should not be given < 4 h after fibrinolytic therapy, and should be given when the APTT is < 70 s; goal APTT = 50 to 70 s; continue infusion for > 48 h.

Heparin Resistance

Reference: Jack Hirsh, Theodore E. Warkentin, Stephen G. Shaughnessy, Sonia S. Anand, Jonathan L. Halperin, Robert Raschke, Christopher Granger, E. Magnus Ohman, and James E. Dalen.  Heparin and Low-Molecular-Weight Heparin Mechanisms of Action, Pharmacokinetics, Dosing, Monitoring, Efficacy, and Safety.  Chest 2001 119: 64S-94S

Patients that require greater than 35,000 units of heparin/day to reach the therapeutic range are considered heparin resistant. This may be related to antithrombin III deficiency; increase in clearance; elevated heparin binding proteins, factor VIII, fibrinogen or platelet factor 4.

"A randomized, controlled trial has shown that adjusting dosage by anti-Xa heparin concentrations results in favorable clinical outcomes in heparin-resistant patients despite lower doses of heparin and subtherapeutic APTT levels.

For patients who require > 35,000 units of heparin per 24 hours, the dose should be adjusted to maintain anti-Xa heparin levels of 0.35 to 0.70 IU/mL.  In a randomized, controlled trial in 131 patients with venous thromboembolism requiring > 35,000 U of heparin per day, monitoring the APTT was compared to anti-Xa heparin activity with no significant differences in clinical outcomes, but the group monitored using anti-Xa heparin levels required significantly less heparin with no difference in bleeding. This approach is especially useful for patients at high risk of bleeding when continued heparin therapy is necessary. Substitution of LMWH may be inadvisable in such patients due to its long half-life and the lack of an effective neutralizing agent. Although measurement of AT levels has also been recommended in the management of heparin resistance, low values are usually secondary to heparin therapy,  rather than the cause of heparin resistance."

Heparin use in stroke patients

Recommended reading: Gregory W. Albers, Pierre Amarenco, J. Donald Easton, Ralph L. Sacco, and Philip Teal.  Antithrombotic and Thrombolytic Therapy for Ischemic Stroke.  Chest 2001 119: 300S-320S
Also refer to protocols from Massachusetts General Hospital Stroke Service (associated with Harvard Medical School).  Recommended guidelines from Massachusetts General include: 

Neuro: Suspected or proven embolic stroke without high risk of progression

Bolus Initial Infusion Target APTT Labs
None 12 units/kg/hour 50-70 6 hrs post bolus or any rate change

Neuro: Cerebral venous sinus thrombosis or strokes at risk for progression. These include critical large vessel stenosis (carotid, basilar or MCA) or patients with fluctuating ischemic symptoms

Bolus Initial Infusion Target APTT Labs
80 units/kg IV up to a max of 5,000 units 12 units/kg/hr to a max of 1,200 units/hr for normal body habitus and 1,800 units/hr for morbid obesity 50-70 seconds Check PTT 6 hours after bolus or after any rate change

Peripheral Venous Thrombosis: DVT, PE

Bolus Initial Infusion Target APTT Labs
80 units/kg IV up to a max of 7,500 18 units/kg/hr max dose of 1800 units/hr 60-85 seconds Check PTT 6 hours after bolus or after any rate change

 

Monitoring: Baseline labs: PT, PTT, CBC (Hgb, Hct, platelet count).  

QOD labs: Hgb, Hct.  
    
Daily labs:
platelet count, PTT. The patient should be monitored daily for signs / symptoms of bleeding.
Mechanism of action Heparin acts as a catalyst to accelerate the rate at which antithrombin III neutralizes thrombin and other activated clotting factors.
Half-life 0.4 to 2.5 hours (Usual: 1.5 hrs)
Heparin resistance Patients with familial antithrombin III deficiency. Also patients with fever, post-op, some with PE, MI, thrombophlebitis, infections with thrombosing tendencies or extensive thrombotic disorders, especially in conjunction with malignant neoplasms.
Heparin-induced thrombocytopena Two forms of H.I.T exist.
(1) Early benign, reversible, non-immune thrombocytopenia.

(2) Late, more serious IgG-mediated version which can cause a  profound drop in the platelet count.

H.I.T. usually begins between 5 to 15 days after therapy, but it can occur within hours of starting therapy in patients who have received heparin previously.
Consider therapy with danaparoid or similar agent.

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