Heparin, an anticoagulant, and Normal Saline (0.9% sodium chloride solution) are frequently used in medical settings. Heparin prevents blood clots, while Normal Saline is primarily a fluid replacement and diluent. Whether they can be “run together” depends on the clinical context: if they are mixed for continuous infusion or administered sequentially in the same intravenous line.
Defining the Components
Heparin is an anticoagulant that functions by accelerating the activity of antithrombin III. This protein inactivates key clotting factors, inhibiting the formation of new blood clots and preventing existing ones from enlarging. Due to its potency and narrow therapeutic range, Heparin requires careful, weight-based dosing and frequent laboratory monitoring.
Normal Saline is an isotonic solution containing 0.9% sodium chloride, meaning its salt concentration is similar to human blood. It is widely used for intravenous fluid replacement to maintain hydration and electrolyte balance. Normal Saline also serves as a standard diluent for many intravenous medications and is routinely used to flush an IV line to keep it patent.
Compatibility for Continuous Infusion
Heparin and Normal Saline are chemically compatible, making Normal Saline the preferred diluent for preparing Heparin solutions for continuous infusion. This compatibility ensures the stability of the Heparin molecule when diluted in 0.9% sodium chloride. Diluting Heparin in this manner helps the drug maintain its anticoagulant activity throughout the infusion period.
Stability studies have demonstrated that Heparin retains its potency for at least 24 hours when diluted in Normal Saline and stored in plastic intravenous bags. This stability profile is significantly better than when Heparin is diluted in solutions containing dextrose, where a loss of activity, sometimes 40% to 55%, can occur.
Due to Heparin’s high-alert status, preparation for continuous infusion is typically performed under controlled conditions in a hospital pharmacy. These standardized protocols use specific, defined concentrations, such as 100 units of Heparin per milliliter of Normal Saline, often provided in commercially pre-mixed bags. This level of control minimizes the risk of improper compounding, which could lead to a loss of drug potency or inaccurate dosing. Clinical practice relies on these pre-mixed or pharmacy-prepared solutions.
Sequential Use in IV Line Maintenance
Normal Saline and Heparin are often administered sequentially for the maintenance of intravenous catheters. This procedural compatibility is distinct from the chemical compatibility required for continuous mixing. Normal Saline is routinely used as a flush before and after administering any medication, including Heparin, to clear the IV line.
This flushing process ensures that the therapeutic Heparin dose reaches the bloodstream without being diluted or interacting with any residual medication left in the tubing. For instance, if the IV line was previously used for administering a lipid-containing solution, a Normal Saline flush is necessary before a Heparin flush to prevent precipitation. The use of Normal Saline in this sequence is a mechanical action to maintain line patency and prevent drug incompatibility within the catheter itself.
In the context of maintaining catheter patency, a very low-concentration Heparin flush solution, typically 10 to 100 units per milliliter, may be used after the Normal Saline flush. This low-dose heparin is not for systemic anticoagulation, but rather to prevent blood clotting within the catheter lumen. However, many current clinical guidelines now suggest that Normal Saline alone is as effective as a Heparin flush for maintaining the patency of peripheral venous catheters, offering a safer alternative by eliminating the potential for Heparin-related complications.