The Core Purpose of IV Flushing
Intravenous (IV) catheter flushing is a fundamental nursing procedure designed to maintain the functionality and safety of a vascular access device [1.6.2]. The primary goals of flushing are to physically clear the catheter's internal lumen, prevent the mixing of incompatible medications, and, most importantly, prevent catheter occlusion (blockage) [1.6.1, 1.6.3]. Occlusions can occur from blood clots (thrombotic) or from the precipitation of incompatible drugs [1.6.1]. Proper flushing clears residual medications and blood, reducing the risk of vein irritation, phlebitis, and serious catheter-related bloodstream infections (CRBSI) [1.6.1, 1.7.5]. Failing to flush an IV line can lead to significant underdosing, with studies showing that 2% to 33% of a medication dose can be lost in the infusion line if not flushed [1.7.1].
Flushing Technique: The SASH and Pulsatile Methods
The standard procedure for intermittent medication administration is the SASH method: Saline, Administer medication, Saline, Heparin [1.8.1]. The initial saline flush confirms patency, while the final saline flush clears the medication from the catheter [1.6.1]. The heparin flush, if required, is used to lock the line and prevent clotting when not in use [1.8.1].
Clinicians are encouraged to use a pulsatile or push-pause technique [1.6.1, 1.8.4]. This involves injecting the flush solution in a series of short, rapid pushes rather than one continuous stream. This method creates turbulence within the catheter, which is more effective at scrubbing the internal walls and clearing away fibrin or medication deposits compared to a smooth, laminar flow [1.6.1]. It's also critical to use a syringe with a diameter of 10 mL or larger for central lines and PICCs to avoid generating excessive pressure that could rupture the catheter [1.4.2, 1.6.1].
Flushing Frequency: Peripheral vs. Central Lines
The required frequency for flushing depends heavily on the type of catheter, its usage, and institutional policy. There is no single universal standard, but evidence-based guidelines provide a strong framework.
Peripheral Intravenous Catheters (PIVCs)
A PIVC is the most common type of IV, typically inserted into a vein in the hand or arm. For intermittently used PIVCs, flushing is recommended to maintain patency.
- Frequency: Guidelines vary, with common recommendations including every 8 to 12 hours or as infrequently as every 24 hours when the line is not in active use [1.2.1, 1.2.3, 1.2.4]. Some studies have found that a 24-hour flushing interval is safe and may have lower complication rates than more frequent flushing [1.2.2].
- Events: A PIVC must always be flushed before and after each medication administration to ensure the full dose is delivered and to prevent incompatibilities [1.4.4].
Central Venous Access Devices (CVADs)
CVADs, which include peripherally inserted central catheters (PICCs), tunneled catheters (e.g., Hickman), and implanted ports, terminate in a large central vein. Their maintenance protocols are often more stringent.
- PICC Lines: When not in continuous use, PICC lines are typically flushed daily to weekly. For example, a weekly flush is recommended for lines not in active use [1.2.3]. Some protocols specify a daily flush with saline, followed by heparin if there is no continuous infusion [1.3.2, 1.3.4].
- Tunneled Catheters: These also typically require a daily flush with saline for each lumen when in use [1.3.2].
- Implanted Ports: For ports that are accessed, they are flushed after each use [1.3.5]. When not in use (de-accessed), maintenance flushing is far less frequent, typically every 4 weeks with saline and/or heparin [1.2.6, 1.3.5].
Comparison of Flushing Protocols
| Catheter Type | Maintenance Flush Frequency (When Not in Use) | Flush After Medication/Use | Typical Flush Solution | Typical Volume |
|---|---|---|---|---|
| Peripheral (PIVC) | Every 8-24 hours [1.2.1, 1.2.4] | Yes, before and after [1.4.4] | 0.9% Normal Saline [1.5.3] | 3-10 mL [1.2.3] |
| PICC Line | Daily to weekly [1.2.3, 1.3.4] | Yes, before and after [1.3.6] | Saline, sometimes with Heparin [1.3.4] | 10 mL Saline, 3-5 mL Heparin [1.3.4, 1.3.5] |
| Tunneled Central Line | Daily per lumen [1.3.2, 1.3.3] | Yes, before and after [1.3.1] | Saline, sometimes with Heparin [1.3.3] | 10 mL Saline, 3-5 mL Heparin [1.3.4] |
| Implanted Port (Port-a-Cath) | Every 4 weeks when de-accessed [1.2.6, 1.3.5] | Yes, after each access [1.3.5] | Saline, often with Heparin lock [1.2.6, 1.3.5] | 10-20 mL Saline, 5 mL Heparin [1.3.5] |
Saline Lock vs. Heparin Lock: What Does Evidence Say?
The debate between using 0.9% sodium chloride (normal saline) versus a heparin solution to lock catheters is ongoing. For years, heparin was standard practice due to its anticoagulant properties that prevent clotting [1.5.5]. However, research and a focus on safety have shifted practice.
- For PIVCs: The use of normal saline is now widely recommended and is considered as effective, if not superior, to heparin in maintaining patency [1.5.3]. Given the risks associated with heparin (an anticoagulant), such as heparin-induced thrombocytopenia (HIT) and bleeding, saline is a safer, simpler, and more cost-effective choice [1.5.3].
- For CVADs: The evidence is more mixed, and practice often varies by institution [1.5.1]. Many studies show little to no significant difference between saline and heparin in preventing central line occlusions [1.5.2, 1.5.6]. Some guidelines still recommend a heparin lock for certain long-term devices like implanted ports or PICCs when they are not in use, but the trend is moving toward saline-only protocols where possible [1.3.4, 1.3.5].
Conclusion: A Practice Guided by Evidence and Policy
The answer to how often is an IV supposed to be flushed is not a single number but a set of principles. Flushing is required before and after every intermittent use to ensure medication efficacy and prevent complications [1.4.4]. Maintenance flushing frequency varies from every 8 hours for a PIVC to every 4 weeks for an implanted port [1.2.1, 1.2.6]. While saline has become the standard for peripheral lines, the choice between saline and heparin for central lines remains institution-dependent, with a growing body of evidence supporting saline-only protocols to enhance patient safety [1.5.3, 1.5.6]. Adherence to aseptic technique, the push-pause method, and institutional guidelines is paramount for all IV maintenance procedures.
Authoritative Link: Infusion Nurses Society (INS) Standards of Practice
