Line flushing to prevent medicine loss following intravenous fluid therapy

There is a lack of standardized practice and national guidance to support flushing technique following administration of intravenous medicines. This article summarises new guidelines on post infusion flushing


There is a lack of standardized practice and national guidance to support flushing technique after administration of intravenous medicines. To help healthcare organizations review their practice and procedures to tackle underdosing due to non-flushing, the National Infusion and Vascular Access Society has updated its guidance on post-infusion flushing. This article summarises its key recommendations.

Citation: Dix A (2021) Line flushing to prevent medicine loss after intravenous fluid therapy. Nursing Times [online]; 117: 5, 22-23.

Author: Ann Dix is ​​acting assistant practice and learning editor, Nursing Times.

  • This article has been double-blind peer reviewed
  • Scroll down to read the article or download a print-friendly PDF here (if the PDF fails to fully download please try again using a different browser)


Hospitalized adults commonly need intravenous (IV) fluid therapy to prevent or correct problems with their fluid and / or electrolyte status, so assessing and managing patients’ fluid and electrolyte needs is fundamental to good patient care (National Institute for Health and Care Excellence, 2017 ). As NICE (2017) states: “Although mismanagement of fluid therapy is rarely reported as being responsible for patient harm, it is likely that as many as one in five patients on IV fluids and electrolytes suffer complications or morbidity due to their inappropriate administration.”

Unless flushing is undertaken after infusion, residual drugs can occur in the ‘dead space’ in infusion sets, causing underdosing in small-volume infusions of <250mL (National Infusion and Vascular Access Society, 2021). This underdosing can be “a problem for patient safety and effectiveness of the therapy, especially for those drugs where dosage is adjusted to body weight” (Plagge et al, 2010). Furthermore, if an unflushed infusion set is then used to administer other infusions, it risks the bolus effect (rapid injection or push administration of the medicine) or incompatibilities between the residual medicine and other infusions (NIVAS, 2021).

Despite these risks, NIVAS (2021) indicates that “in clinical practice, flushing IV infusion sets in adult patients is rare, with the exception of administration of chemotherapy in oncology”. A study in one teaching hospital showed that 74% of administration sets were not flushed, and non-flushing occurred in> 90% of gravity infusions and 61% of pump infusions in all areas except oncology, which was the only area where flushing was standard practice (Harding et al, 2020). The same study showed that antibiotics were commonly infused and up to 21% of each antibiotic dose was often discarded.

One problem is a lack of national guidance, standardization or evidence to support flushing technique (NIVAS, 2021). To help address the under-recognized problem of underdosing due to non-flushing, NIVAS has updated its guidance online flushing to help healthcare organizations review their practice and procedures, and develop local policies to minimize the risks of underdosing.

The NIVAS (2021) guidance gives practitioners and organizations an overview of residual medicine volumes in infusion sets, along with best-practice recommendations for flushing based on the available evidence and expert consensus. The guidance should be used in conjunction with local medicines policy and NICE guidance on IV fluid therapy for hospitalized adults (NICE, 2017). The NIVAS updated guidance is summarized below.

Administering IV therapy

It is important to avoid reusing infusion-giving sets for different medicine solutions if the solutions are not compatible. Infusion sets can be used continuously for multiple fluid infusions such as sodium chloride 0.9%, following local policy.

There are several infusion methods and the potential impact of flushing / lack of flushing depends on the dead space of the infusion-giving set used and the volume of the infusion. IV infusion sets administering large-volume medicine infusions (≥250ml) or hydration fluids do not need flushing as the proportion of medicine remaining in the set will be relatively small.

IV syringe injection (bolus)

Injecting directly into the peripheral venous access does not require an infusion set and the cannula should be flushed before and after administering the IV medicine, according to local policy.

Syringe infusion pump

When using a syringe pump, an IV extension tube connects the patient’s venous access device to the syringe. Syringe infusion sets hold around 2ml of solution, depending on the type and length of the tube, and the set used.

Infusion bag

This method is used for medicines that need to be administered at a slower rate than via syringe injection (for example, certain antibiotics). It allows fast dilution into the bloodstream and reduces the risk of chemical phlebitis (inflammatory response). Medicine is added to the bag or available as a ready-to-administer infusion, and the bag is connected to the vascular access device via an infusion set with a needle-free connector.

Once the bag is empty, the infusion set and tubing will still contain around 20-30ml of medicine, depending on the type / length of tube and administration method used (gravity or pump). This residual volume is likely to be more clinically significant for small infusions of ≤100ml and, in particular, 50ml bags (Harding et al, 2020).

Line flushing post infusion

Fixed-rate infusions

A total medicine dose administered over a set time period is prescribed (for example, 2g ceftriaxone over 30 minutes) and flushing directions depend on how the infusion has been administered:

  • Syringe pump – disconnect the syringe from the infusion set and flush the line with 0.9% sodium chloride (or a compatible diluent) at the same infusion rate as the medicine just administered. This may require a syringe pump to administer;
  • Volumetric pump or gravity – flush the infusion set with 0.9% sodium chloride (or compatible dilutant) using one of the two methods for flushing bag infusions outlined below.

Variable-rate continuous infusions via syringe or volumetric pump

Central venous access device. If possible, aspirate the device contents after discarding the infusion set, then flush with 0.9% sodium chloride.

Peripheral IV cannula. This is used, for example, to administer strong sedatives or anaesthetics. Discard the infusion set and flush the cannula at the same rate as the administration of the infused medicine; this will help avoid a bolus effect.

Infusions administered from a bag

The flushing method depends on whether there are one or two ports on the IV infusion set. To avoid the risk of fluid overload, take care to minimize the volume of fluid used for flushing in patients who receive multiple daily infusions or are fluid restricted.

When a one-port IV infusion set is used, flush the set using a 100ml or 50ml bag of 0.9% sodium chloride or equivalent compatible fluid. At least 20ml is usually required to administer the residual medicine; it should be infused at the same rate as the original medicine and disconnected on reaching the required flush volume. The additional port on a two-port IV infusion set allows the infusion chamber to be filled with diluent from a syringe or bag of fluid; as such, the residual medicine in the tubing can administered at the same rate as the previous infusion.

Once the cannula has been cleared of IV drugs, a push – pause technique should be used to flush the device to avoid blood reflux at the distal indwelling end, as this can cause occlusion.

Avoiding push administration of medicine

In infusion sets

Ensuring the flushing or subsequent infusion rate is the same as that of infusion of the medicine avoids inadvertent push (rapid) administration of medicine from the dead space in an infusion set. The NIVAS (2021) guidance points to an incident reported to the National Reporting and Learning System in which a bag of Hartmann’s solution infused faster than a previous infusion of potassium chloride in 0.9% sodium chloride, causing the patient to receive an unintended push of the residual potassium solution.

From residual volume in vascular access devices

There is a risk of unintended push administration from residual anesthetic or sedative medicines left in the lumens of vascular access devices after surgery and other procedures. A warning patient safety alert – NHS England (2014) – required local system review and, if required, an action plan to prevent such incidents occurring after surgery or other procedures requiring anesthetic.

Recommended procedures to prevent patients returning to wards / units with cannulas or IV lines in place containing residual drugs include prompts in documentation and at patient handover in the procedural area to confirm that all cannulas and IV lines that may contain residual drugs have been fully flushed or removed (NHS Improvement, 2017).


Line flushing is needed to prevent medicine loss after IV fluid therapy but is rarely standard practice. Post-infusion flushing is required for small-volume infusions to ensure patient safety and therapy effectiveness. Accidental push dosing can occur if the correct flushing technique is not used.

Key points

  • Flushing lines is necessary to prevent medicine loss after intravenous fluid therapy
  • Post-infusion flushing is rarely standard practice, which can compromise patient safety and the effectiveness of intravenous therapy
  • The risks associated with failure to flush depend on the volume of the infusion and the dead space of the infusion device used
  • A new infusion set must be used for each new medicine, and line flushing is recommended for small volume infusions of <250ml
  • Accidental push dosing can occur if the appropriate flushing technique is not used
  • This article is a summary of NIVAS’s (2021) guidance. To read more about the rationale behind the guidelines, read the opinion piece by Andrew Barton, chair of NIVAS, at:

Harding M et al (2020) Best practice for delivering small-volume intermittent intravenous infusions. Journal of Infusion Nursing; 43: 1, 47-52.

National Infusion and Vascular Access Society (2021) Intravenous Administration of Medicines to Adults: Guidance on “Line Flushing” – Version 3. NIVAS.

NHS England (2014) Residual Anaesthetic Drugs in Cannulae and Intravenous Lines., 14 April.

NHS Improvement (2017) Confirming Removal or Flushing of Lines and Cannulae After Procedures. NHSI.

National Institute for Health and Care Excellence (2017) Intravenous Fluid Therapy in Adults in Hospital. NICE.

Plagge H et al (2010) Evaluation of the dead volume in intravenous short-term infusion. European Journal of Hospital Pharmacists: Science; 16: 2, 31-37.

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