KVO stands for “keep vein open,” and it refers to a very slow IV drip, typically between 1 and 10 mL per hour, used to maintain access through an intravenous catheter when a patient isn’t actively receiving medication or fluids. You may also see it written as TKO, meaning “to keep open.” The two abbreviations are interchangeable.
Why a Slow Drip Keeps the Line Working
When an IV catheter sits idle in a vein with no fluid moving through it, blood can flow back into the tubing and form small clots. Those clots can block the catheter entirely, which means the line has to be removed and a new one started. A KVO rate prevents this by pushing just enough fluid through the catheter to keep it clear without delivering a meaningful volume of liquid to the patient.
This matters most when medications are given on a schedule rather than continuously. Between doses, the IV line would otherwise sit unused for hours. Running a slow background drip maintains the catheter so the next dose can be delivered without delay. It also keeps the line ready for emergencies where immediate IV access could be critical.
Typical Flow Rates
There is no single universal KVO rate. Hospitals set their own standards, and rates vary depending on the patient and the equipment. Most facilities use a rate somewhere between 1 and 10 mL per hour for adults. A survey of Illinois hospital pharmacists found that 87% of responding institutions either had a standardized KVO rate on file or required that a specific rate be written into each order.
Modern infusion pumps handle this automatically. When a programmed infusion finishes, the pump can switch itself to a preset KVO rate rather than stopping completely. On the Alaris pump system, for example, the KVO rate is configurable from 1 to 20 mL per hour, and hospitals can set a different default for each clinical profile. This automatic transition prevents the catheter from clotting while a nurse prepares the next infusion or assesses the patient.
KVO in Children and Newborns
In pediatric patients, KVO rates need more careful consideration because even small volumes of extra fluid represent a larger proportion of a child’s total body weight. One study defined a “keep vein open” infusion in children as anything at or below 10 mL per hour, but noted that for babies weighing under 5 kg, that rate is already more than half of what would be considered their full maintenance fluid volume. In other words, what counts as a trickle for an adult can be a substantial fluid load for a very small child.
Research in newborns has not found a clear benefit to running a slow drip compared to simply locking the catheter with a small flush of saline. A Cochrane review of studies in the neonatal population reached the same conclusion. Because of this, and because tubing connected to active infants carries an entanglement risk, many pediatric units prefer saline locks over continuous KVO drips when possible.
KVO Rate vs. Saline Lock
A saline lock is the main alternative to a KVO drip. Instead of running fluid continuously, a nurse flushes the catheter with a small syringe of sterile saline and then caps it off. The 2024 Infusion Therapy Standards of Practice from the Infusion Nurses Society recommend using preservative-free saline to lock peripheral catheters after each intermittent infusion or at least every 24 hours. The recommended flush volume is at least twice the internal volume of the catheter and any attached extension tubing.
For central lines like PICCs, locking can be done with either saline or a diluted heparin solution to provide additional clot prevention. The choice between a KVO drip and a saline lock depends on how frequently the line will be used, the patient’s fluid tolerance, and hospital protocol. A patient who needs IV medications every few hours may do fine with a saline lock between doses, while someone who could need emergency access at any moment might benefit from a continuous KVO drip that guarantees the line is always flowing.
Risks of Continuous KVO Infusions
Although the volumes are small, a KVO drip running around the clock still adds up. At 10 mL per hour, a patient receives 240 mL of extra fluid over 24 hours. For most healthy adults, that amount is trivial. For patients with heart failure, kidney disease, or conditions where fluid balance is tightly managed, even that modest volume can contribute to overload. This is one reason many institutions have moved toward saline locks as the default, reserving continuous KVO infusions for situations where uninterrupted access is genuinely necessary.
The other consideration is vein irritation. Any fluid running through a peripheral catheter for an extended period increases the risk of inflammation at the insertion site. The longer a line stays in with continuous flow, the higher the chance of complications that require removing and replacing it. Saline locks, by contrast, leave the catheter idle between flushes, which can reduce mechanical irritation to the vein wall.
Why the Practice Varies So Much
Despite being a routine part of IV care, KVO has surprisingly little standardized evidence behind it. A 2016 review in the nursing literature described it as a “sacred cow,” a longstanding practice without clear origins or robust research to define the ideal rate. More than 50% of Canadian nurses surveyed reported regularly using a KVO rate between doses of intermittent medications, but the specific rates they used varied widely. This is why you will see different numbers quoted in different settings. The concept is consistent, but the execution depends heavily on institutional policy, patient size, and clinical judgment.