What is the appropriate dosing for a Heparin (unfractionated heparin) infusion?

From the Guidelines

Heparin drip dosing should typically follow a weight-based protocol starting with a bolus of 80 units/kg followed by an initial infusion rate of 18 units/kg/hour, as recommended by recent guidelines 1. The dose is then adjusted based on activated partial thromboplastin time (aPTT) results, which should be checked 6 hours after starting therapy and 6 hours after any dose adjustment. The target aPTT is usually 1.5-2.5 times the control value (approximately 60-80 seconds, though this varies by institution) 1. Some key points to consider when administering heparin include:

• If the aPTT is below target, give an additional bolus of 80 units/kg and increase the infusion rate by 4 units/kg/hour.
• If the aPTT is above target, hold the infusion for 1 hour and decrease the rate by 2 units/kg/hour.
• For critically ill patients or those with high thrombotic risk, a more aggressive protocol may be used.
• Patients should be monitored for bleeding complications, and platelet counts should be checked regularly to detect heparin-induced thrombocytopenia. Heparin works by binding to antithrombin III, enhancing its ability to inactivate several coagulation factors including thrombin and factor Xa, thereby preventing clot formation and extension 1. It's also important to note that the safety and efficacy of fixed dose, unmonitored, subcutaneous UFH has been reported to be comparable to LMWH in the treatment of patients with acute VTE, but further investigation is warranted before this regimen can be routinely used in patients with cancer 1. In terms of specific dosing, a study published in the Mayo Clinic Proceedings provides a clear outline of the recommended dosing for unfractionated heparin, which includes an intravenous bolus of 80 U/kg followed by an infusion of 18 U/kg per hour 1. Overall, the key to effective heparin drip dosing is careful monitoring and adjustment of the dose based on aPTT results, as well as attention to potential complications such as bleeding and heparin-induced thrombocytopenia.

From the FDA Drug Label

The dosing recommendations in Table 1 are based on clinical experience be adjusted for the individual patient according to the results of suitable laboratory tests, the following dosage schedules may be used as guidelines: Table 1: Recommended Adult Full-Dose Heparin Regimens for Therapeutic Anticoagulant Effect *Based on 68 kg patient METHOD OF ADMINISTRATION FREQUENCY RECOMMENDED DOSE Continuous Intravenous Infusion Initial Dose 5,000 units by intravenous injection Continuous 20,000 to 40,000 units/24 hours in 1,000 mL of 0.9% Sodium Chloride Injection, USP (or in any compatible solution) for infusion

The recommended adult full-dose heparin regimen for therapeutic anticoagulant effect via continuous intravenous infusion is an initial dose of 5,000 units by intravenous injection, followed by a continuous infusion of 20,000 to 40,000 units/24 hours in 1,000 mL of 0.9% Sodium Chloride Injection, USP (or in any compatible solution) for infusion 2.

From the Research

Heparin Drip Dosing

• Heparin drip dosing is a complex process that requires careful monitoring and adjustment to ensure effective anticoagulation and minimize the risk of bleeding complications 3.
• Unfractionated heparin (UFH) is a heterogeneous mixture of glycosaminoglycans that bind to antithrombin, catalyzing the inactivation of thrombin and other clotting factors, but its pharmacokinetic and pharmacodynamic properties can be unpredictable 3.
• Low-molecular-weight heparin (LMWH) has more predictable pharmacokinetic and pharmacodynamic properties than UFH and has replaced UFH for most clinical indications, but its use in patients with severe obesity or renal insufficiency requires careful monitoring with an anti-factor Xa assay 3, 4.
• In patients with apparent heparin resistance, anti-factor Xa monitoring may be superior to measurement of activated partial thromboplastin time (aPTT) 3.
• The therapeutic range for anti-factor Xa activity depends on the dosing interval, and anti-factor Xa monitoring is prudent when administering weight-based doses of LMWH to patients who weigh > 150 kg 3.

Special Considerations

• In patients with renal insufficiency, UFH infusion may be preferable to LMWH injection, but LMWH is safe for prophylactic use in patients with renal failure 3, 4.
• Tinzaparin may be a safe and effective option for VTE treatment and prevention in cancer patients with renal failure 4.
• Antithrombin deficiency is a common cause of heparin resistance, and antithrombin concentrate may be used to overcome this resistance 5.
• Patients with impaired renal function are at increased risk for bleeding complications, and dose reductions are recommended for many anticoagulants, including LMWH and non-vitamin K antagonist oral anticoagulants (NOAC) 6.

Monitoring and Adjustment

• Regular monitoring of renal function and anti-Xa levels is necessary when using LMWH in patients with renal insufficiency 4.
• Dose adjustments may be necessary to prevent bleeding complications, and the use of alternative anticoagulants may be considered in certain situations 3, 4, 6, 7.