Intravenous (IV) therapy delivers fluids, nutrients, and medications directly into a patient’s bloodstream. Maintaining this access is necessary even when continuous fluid administration is not required. The practice of keeping the intravenous line open, or maintaining patency, is commonly referred to as KVO (Keep Vein Open). This slow, continuous infusion ensures the IV access remains functional and ready for immediate use.
Understanding the KVO Concept
The purpose of a Keep Vein Open (KVO) infusion is to maintain the patency of the intravenous catheter. Patency means the line is open and unobstructed, allowing fluid to flow freely into the vein. This minimal flow prevents complications that would otherwise block the line.
The KVO rate is intentionally low; it is not intended to provide therapeutic hydration or nutritional support. Its function is to deliver just enough fluid to continuously flush the catheter tip and the inner lining of the tubing. Without this minimal flow, blood can reflux into the catheter, leading to the formation of a clot (thrombus) and causing occlusion.
This slow drip also helps prevent the buildup of drug precipitates or bacterial biofilms inside the catheter. Maintaining this open pathway ensures healthcare providers have immediate, reliable access to the patient’s circulatory system for rapid drug delivery or fluid administration.
Standard Rates for Keeping a Vein Open
The standard rate for a Keep Vein Open infusion is not a single, fixed number but a low range dictated by facility protocols. For adult patients, the typical KVO rate falls within 10 to 20 milliliters per hour (mL/hr). This rate is often the lowest available setting on an electronic infusion pump, the preferred method for controlling IV flow with high precision.
This minimal flow rate delivers a small volume of fluid, such as saline, achieving patency without significantly contributing to the patient’s overall fluid intake. The use of electronic pumps has standardized the KVO rate to an hourly volume measurement. The Infusion Nurses Society (INS) commonly recommends 10 mL/hr for electronic volumetric pumps.
While 10 mL/hr is a frequent standard, research suggests that such low flow rates may not always be sufficient to clear the catheter tip entirely, potentially promoting clotting. Some models suggest a higher rate, perhaps 30 to 40 mL/hr, could be more effective at preventing occlusion in peripheral IV catheters. The prescribed rate is ultimately a balance between maintaining line function and minimizing the patient’s fluid load.
When a KVO Rate is Ordered
A Keep Vein Open rate is ordered when a patient requires intermittent venous access. This is common when a patient receives scheduled intravenous medications, and the KVO infusion maintains readiness between doses, avoiding the need to repeatedly start and stop the line.
A frequent application is when a patient is awaiting a diagnostic procedure, such as a CT scan or MRI, requiring the intermittent injection of contrast media. The KVO flow keeps the line clear and patent during the waiting period. KVO is also ordered for patients at risk of a sudden medical emergency or those with unstable conditions. This ensures a functioning IV line is immediately available for life-saving drugs or rapid fluid resuscitation.
How Patient Needs Affect the Final Rate
The standard KVO rate serves as a starting point, but the final prescribed rate is adjusted based on specific patient factors and clinical policies. The most significant consideration is the patient’s body size and fluid sensitivity, especially in pediatric and geriatric populations. Infants and young children have a smaller total blood volume, making them highly susceptible to fluid overload.
For neonates weighing less than 5 kilograms, the KVO rate is drastically reduced, often to 0.8 to 1 mL/hr. Older children may receive 3 to 5 mL/hr. Similarly, a frail elderly patient with heart or kidney failure may require a lower-than-standard adult rate, perhaps closer to 5 mL/hr, to mitigate the risk of fluid accumulation.
Facility policies also introduce variation. Some institutions mandate a higher minimum rate for central venous lines to prevent occlusion, while others adhere to the lower 10 mL/hr standard for all adult lines.