Saline Lock vs. Heparin Lock (Heplock)

The maintenance of intravenous (IV) catheters, both peripheral and central, is essential to ensure safe and reliable access for fluid administration, medication delivery, and other clinical interventions. Two commonly used solutions for maintaining catheter patency are heparinized saline (heparin lock) and 0.9% sodium chloride (saline lock). While heparin has historically been used as the default agent, increasing evidence has prompted a re-evaluation of its necessity in routine catheter maintenance.

Heparin was traditionally favored due to its anticoagulant properties, under the assumption that it could reduce fibrin buildup and clot formation within catheters. However, heparin is not without risks. These include heparin-induced thrombocytopenia (HIT), allergic reactions, drug incompatibility, and the potential for systemic anticoagulation. Additionally, the use of heparin introduces a risk of dosage and administration errors, particularly concerning in high-risk populations such as pregnant women, neonates, or patients on multiple medications.

A 2003 study by Niesen compared heparin versus saline for peripheral intravenous (PIV) lock maintenance in pregnant women, finding no significant difference in catheter patency between the two solutions. Given the vulnerability of this patient group to anticoagulant complications, the results supported saline as an effective and potentially safer alternative (1).

Nearly a decade later, Wang and colleagues conducted a prospective controlled trial assessing preservative-free 0.9% sodium chloride for flushing and locking peripheral IV access devices. The study concluded that saline maintained catheter function effectively and without the risks associated with heparin. The authors emphasized that proper flushing technique and frequency were more important than the specific solution used and recommended saline as the default agent in general clinical practice (2).

More recently, the European Recommendations on Peripheral Intravenous Access Devices (ERPIUP), published in 2023 under the World Congress on Vascular Access (WoCoVA), offered expert consensus on peripheral vascular access management. The guidelines strongly support using saline for peripheral IV maintenance and limiting the use of heparin to specific high-risk scenarios, such as long-term central access or total parenteral nutrition. These recommendations reflect a growing trend toward simplified, evidence-based protocols that reduce unnecessary medication use (3).

The most recent and comprehensive analysis comes from Santomauro et al., who published an umbrella review in 2024 comparing heparin versus saline lock in adults with central venous catheters. Drawing from studies in oncology, intensive care, and surgical populations, the review found no statistically significant difference between the two solutions in preventing catheter occlusion, catheter-related infections, or thrombosis. The authors concluded that heparin is not superior to saline and advocated for the adoption of saline as the standard of care due to its safety, simplicity, and cost-effectiveness (4).

Although heparin is still warranted in some specialized clinical circumstances, such as long-term catheter management in select oncology patients, evidence increasingly supports removing it from routine use for peripheral or short-term central lines. Saline is equally effective at maintaining patency, carries a lower risk profile, and reduces the potential for adverse drug events.

High-quality evidence currently supports using normal saline instead of heparin to lock IV catheters in most adult patients. With comparable efficacy, fewer risks, and practical advantages in cost and handling, saline is the preferred agent in modern vascular access protocols.

References

1. Niesen KM, Harris DY, Parkin LS, Henn LT. The effects of heparin versus normal saline for maintenance of peripheral intravenous locks in pregnant women. J Obstet Gynecol Neonatal Nurs. 2003;32(4):503-508. doi:10.1177/0884217503255203
2. Wang R, Luo O, He L, Li JX, Zhang MG. Preservative-free 0.9% sodium chloride for flushing and locking peripheral intravenous access device: a prospective controlled trial. J Evid Based Med. 2012;5(4):205-208. doi:10.1111/jebm.12004
3. Pittiruti M, Van Boxtel T, Scoppettuolo G, et al. European recommendations on the proper indication and use of peripheral venous access devices (the ERPIUP consensus): A WoCoVA project. J Vasc Access. 2023;24(1):165-182. doi:10.1177/11297298211023274
4. Santomauro I, Campani D, Tiozzo V, et al. Heparin versus normal saline locking for prevention of occlusion, catheter-related infections and thrombosis in central venous catheter in adults: Overview of systematic reviews. J Vasc Access. 2024;25(6):1741-1748. doi:10.1177/11297298221103201