From the FDA Drug Label
2.3 Therapeutic Anticoagulant Effect with Full-Dose Heparin 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 Deep Subcutaneous (Intrafat) Injection Use a different site for each injection to prevent the development of hematoma Initial Dose 5,000 units by intravenous injection, followed by 10,000 to 20,000 units of a concentrated solution, subcutaneously Every 8 hours or 8,000 to 10,000 units of a concentrated solution Every 12 hours 15,000 to 20,000 units of a concentrated solution Intermittent Intravenous Injection Initial Dose 10,000 units, either undiluted or in 50 to 100 mL of 0. 9% Sodium Chloride Injection, USP Every 4 to 6 hours 5,000 to 10,000 units, either undiluted or in 50 to 100 mL of 0.9% Sodium Chloride Injection, USP 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 dosage of heparin for critically ill patients is not explicitly stated in the label. However, the label provides general guidelines for therapeutic anticoagulant effect with full-dose heparin.
- For deep subcutaneous injection, the initial dose is 5,000 units by intravenous injection, followed by 10,000 to 20,000 units of a concentrated solution subcutaneously every 8 hours or 8,000 to 10,000 units every 12 hours.
- For intermittent intravenous injection, the initial dose is 10,000 units every 4 to 6 hours, with 5,000 to 10,000 units either undiluted or in 50 to 100 mL of 0.9% Sodium Chloride Injection, USP.
- For continuous intravenous infusion, the initial dose is 5,000 units by intravenous injection, with a continuous infusion of 20,000 to 40,000 units/24 hours in 1,000 mL of 0.9% Sodium Chloride Injection, USP. It is essential to adjust the dosage according to the patient's coagulation test results and to monitor the patient's aPTT, INR, and platelet count regularly. 1
From the Research
Heparin dosing in critically ill patients should be individualized, but the most recent and highest quality study suggests that prophylactic dosing of heparin 3 times/day versus twice/day was not associated with differences in new venous thromboembolism (VTE) or safety outcomes 2.
Heparin Dosing Considerations
When considering heparin dosing in critically ill patients, several factors must be taken into account, including the patient's weight, renal function, and bleeding risk.
- For unfractionated heparin (UFH), an initial bolus of 80 units/kg is recommended, followed by a continuous infusion starting at 18 units/kg/hour, with dose adjustments based on activated partial thromboplastin time (aPTT) or anti-Xa levels 3.
- For low molecular weight heparin (LMWH), such as enoxaparin, the standard treatment dose is 1 mg/kg twice daily, but this should be reduced to 0.5 mg/kg twice daily in patients with creatinine clearance below 30 mL/min 4.
- Critically ill patients often require higher heparin doses due to increased levels of acute phase reactants like factor VIII and fibrinogen, which create a relative heparin resistance.
Monitoring and Adjustments
Regular monitoring is essential, with aPTT checks recommended 6 hours after initiation and 6 hours after any dose change.
- Platelet counts should be monitored every 2-3 days to detect heparin-induced thrombocytopenia.
- In patients with obesity, actual body weight should be used for initial dosing, with potential capping for extremely obese individuals.
- For patients with high bleeding risk, consider starting with lower doses and more frequent monitoring.
Recent Study Findings
A recent study found that therapeutic-dose anticoagulation with heparin did not result in a greater probability of survival to hospital discharge or a greater number of days free of cardiovascular or respiratory organ support than did usual-care pharmacologic thromboprophylaxis in critically ill patients with Covid-19 5.
Key Takeaways
- Individualized heparin dosing is crucial in critically ill patients.
- Monitoring and dose adjustments should be based on aPTT or anti-Xa levels.
- Patients with renal dysfunction or obesity require special consideration.
- Recent studies suggest that therapeutic-dose anticoagulation with heparin may not be beneficial in all critically ill patients, and prophylactic dosing regimens may be sufficient in some cases 2, 5.