Normal saline (0.9% sodium chloride) is compatible with IVIG for flushing IV lines, but it should not be used to dilute the product. This is a critical distinction. You can run saline through the tubing before and after an IVIG infusion to clear the line, but you cannot add saline to the IVIG bag or bottle itself. If dilution is needed, 5% dextrose in water (D5W) is the standard choice across nearly all IVIG brands.
Flushing vs. Diluting: Why the Difference Matters
IVIG is a concentrated solution of immunoglobulin proteins. These proteins can clump together, or aggregate, when exposed to certain conditions. Mixing saline directly into the product changes the ionic strength of the solution, which can alter protein solubility and trigger aggregation. Protein aggregates are believed to be responsible for the majority of adverse reactions during IVIG infusions, including fever, chills, and headache.
Flushing a line with saline is a different situation. When you flush, the saline passes through the tubing briefly and does not sit in prolonged contact with the concentrated IVIG solution. The amount of mixing is minimal, so the risk of destabilizing the proteins is negligible. That’s why manufacturers generally approve saline for flushing but prohibit it as a diluent.
Brand-Specific Rules
While the general rule holds across products, each IVIG brand has slightly different compatibility instructions in its FDA-approved prescribing information. The differences matter enough that you should always check the specific product you’re working with.
- Privigen (10% liquid): Can be diluted only with D5W. The infusion line may be flushed with either D5W or 0.9% sodium chloride.
- Gamunex-C: If dilution is required, use D5W only. Do not dilute with saline. The infusion line can be flushed with either D5W or 0.9% sodium chloride. If using a heparin lock, flush with D5W or saline afterward, not with heparin.
- Gammagard Liquid: Do not use normal saline as a diluent. The infusion line may be flushed with normal saline.
- Gammagard S/D: This is the notable exception. It should only be flushed with D5W. Normal saline is not recommended even for line flushing with this product.
The pattern is consistent: D5W is universally acceptable for both flushing and dilution, while saline is acceptable for flushing with most brands but never for dilution. Gammagard S/D breaks even that pattern by restricting flushing to D5W only.
Practical Administration Guidelines
IVIG should be infused through a dedicated, separate infusion line. It should never be mixed with other IV medications, regardless of the fluid running through the line. If a patient has another infusion running, IVIG needs its own line or port.
Before starting the infusion, visually inspect the product. It should appear clear or slightly opalescent, ranging from colorless to pale yellow. If the solution looks turbid, cloudy, or contains visible particles or deposits, do not infuse it.
Most modern IVIG products come as ready-to-use liquid formulations that do not require any dilution at all. The question of saline compatibility most often comes up in the context of line flushing or when a patient needs a slower, more dilute infusion to reduce side effects. In those cases where dilution is truly needed, D5W is always the correct choice.
Why Protein Aggregation Is a Concern
IVIG carries a high protein load. When the proteins aggregate, they can increase plasma viscosity and activate the body’s complement system, a branch of the immune response that triggers inflammation. This is one proposed mechanism behind the blood clot risk associated with IVIG infusions. Aggregated proteins may also increase platelet activity, further raising clotting risk.
Several factors influence how well a patient tolerates an IVIG infusion: the salt and sugar content of the specific product, the volume being infused, the pH, the osmolality, and the infusion rate. Using the wrong diluent adds an unnecessary variable to an already complex picture. Sticking to the manufacturer’s instructions for each product removes one avoidable source of adverse reactions.