Central venous access devices (CVADs): flush volumes

This guideline covers the flushing of central venous access devices (CVADs) used with Great Ormond Street Hospital (GOSH).

These include:

  • Skin tunnelled cuffed central venous catheters (CVCs) (commonly referred to as Hickman® catheters, Broviac® catheters). These CVCs may have one, two or three separate lumens.
  • Implanted ports (Ports) (commonly referred to as ports, port-a-cath, Bardport®). May have one or two reservoirs/chambers.
  • Peripherally inserted central catheter (PICC). There are two types of PICCs used within GOSH, open-ended (non valved) i.e. Cook® peripherally inserted central catheter with clamps in situ or valved catheters i.e. Groshong® NXT ClearVueTM PICC). These may have one or two separate lumens.
  • Tunnelled non cuffed CVCs (TNC-CVC) may have 1 or 2 separate lumens.
  • Long-term skin tunnelled haemodialysis/apheresis CVCs (may be referred to as PermCath®/Splitcath®). These may have one or two lumens.
  • Short-term/temporary non-tunnelled haemodialysis/apheresis CVCs (Gamcath®). These may have one or two lumens.
  • Short-term non-tunnelled CVC (acute care CVC, may also be referred to in practice as neck line/subclavian line or femoral line). Usually made of polyurethane. These may have one, two or three separate lumens.

If the child/young person has a CVAD in situ that is not listed here, refer to the manufacturer of the CVAD for further information on flush volumes. Otherwise contact your ward education team or the Central Vascular Access Team (CVAT).

Purpose of flushing CVADs

Routine flushing of CVADs is performed at established intervals to promote and maintain patency and prevent the mixing of incompatible medications and solutions (Royal College of Nursing (RCN) 2010). Sodium chloride 0.9% or other compatible solution must be used before, between and after the administration of incompatible medications and/or solutions (RCN 2010; National Patient Safety Agency (NPSA) 2008).

Standard flushing solutions used most frequently for CVADs includes sodium chloride 0.9% and/or heparinised sodium chloride (various strengths 10-5,000 units per ml) (Hadaway 2006; Richardson 2007; Dougherty and Lister 2008).

Heparin versus sodium chloride 0.9% only flushes

Low dose heparin flushes are frequently used to fill the lumens of a CVAD between use in an attempt to prevent thrombus formation and to prolong the duration of catheter patency. However, the efficacy of this practice is unclear (Loveday et al 2014; Bishop et al 2007). Some clinicians and manufacturers recommend heparin flushes when CVADs are infrequently accessed (e.g. implanted ports) or are used for blood processing (i.e. apheresis or haemodialysis) (Loveday et al 2014).

A review of the evidence on heparin flushes by UK Medicines Information indicates that the evidence for heparin flushes is unclear and inconclusive (UK Medicines Information 2012). A rapid response report issued by the NPSA in April 2008 advised organisations to review local policies in order to minimise the use of heparin flush solutions for all vascular access devices (NPSA 2008

The requirement for heparin over 0.9% sodium chloride may be a function of catheter bore, as large bore catheters (i.e. apheresis/haemodialysis catheters) allow faster back-tracking of blood up the lumen (Bishop et al 2007).

There is a lack of research in children on the efficacy of heparin flushes. Whilst changing from heparin to sodium chloride 0.9% flushes for CVADs would result in cost savings and more importantly a reduction in risks of inadvertent administration of an overdose of heparin, current research does not appear to support such a complete withdrawal of heparin. Indeed it is not known whether withdrawing heparin from use in CVADs would lead to an increase in occlusion and premature removal of such devices (Toft 2007). Loveday et al (2014) advocate the use of sodium chloride to flush and lock lumens that are accessed frequently.

Risks associated with heparin flush solutions

Decreasing unnecessary exposure to heparin is important to minimise adverse effects associated with heparin use, e.g. autoimmune mediated heparin-induced thrombocytopenia, allergic reactions and the potential for bleeding complications following multiple, unmonitored heparin flushes (Loveday et al 2014).

Problems known to occur when heparin flush solutions are used include:

  • Confusion with other 'look-a-like' products (NPSA 2008).
  • Using unlabelled heparin syringes (NPSA 2008).
  • Errors in calculating and diluting heparin (NPSA 2008).
  • Incompatibility of heparin with other medicines (Toft 2007).
  • Administration of incorrect strength of heparin i.e. 10,000 units per mL instead of 10 units per mL resulting in the deaths of three infants (Toft 2007).
  • Heparin interfering with blood test results if it is present in the CVAD or cannula (Toft 2007).
  • Administration of heparin without a prescription or patient group direction increases the risks of errors (NPSA 2008).

General guidance when flushing CVADs

Use of an aseptic non touch technique (ANTT) and good standards of hand washing can reduce the risk of infection when using CVADs. Refer to clinical guidelines on ANTT for intravenous therapy and hand hygiene. 

Heparin 1-10 units/ml should be used for neonates and paediatric patients (Infusion Nurses Society 2006). The concentration of heparin used should be the lowest possible that will maintain patency (RCN 2010).

Solutions and frequency of flushing may be dependent on whether the catheter is open ended (e.g. Hickman® or Cook®) or valved. Sodium chloride 0.9% is recommended by manufacturers of valved catheters. Valved CVADs should be flushed with 0.9% sodium chloride according to manufacturer's instructions (RCN 2010; Bishop et al 2007). Frequency of flushing can vary from daily to weekly (Dougherty and Lister 2008).

If the child is receiving one or more intravenous drugs each day via an accessed (needle in situ) implanted port, then 10 units per ml of heparin can be used to flush the device (Bravery 2008; Frey 2007; Bishop et al 2007; Hagle 2007). When the implanted port will not be used for four weeks manufacturers and clinicians recommend that 100 units per ml of heparin is used to flush the port (Frey 2007; Hagle 2007; RCN 2010; Dougherty and Lister 2008; Bravery 2008).

All flush solutions used for CVADs must be administered in accordance with the appropriate patient group direction or patient specific direction (Nursing and Midwifery Council 2008; NPSA 2008).

The volume of the flush solution should be equal to at least twice the volume of the catheter and add on devices (RCN 2010).

10ml syringes should be used to flush CVADs (Bishop et al 2007). Excessive force should be avoided when flushing CVADs. If resistance is felt during flushing and force is applied to the syringe plunger this can result in high pressure within the catheter which may rupture. Before use, the CVAD should be checked for patency using a 10ml or larger syringe containing 0.9% sodium chloride (Dougherty and Lister 2008).

To avoid systemic heparinisation when using apheresis/haemodialysis the high-strength heparin must be aspirated from the CVAD prior to use and the CVAD flushed with 0.9% sodium chloride. An amount equivalent to the catheter priming volume or 'dead space' of 1,000 units per ml of heparin should be instilled after use (Bravery and Wright 1998; GOSH 2015). The priming volumes are printed on the external clamp or catheter for reference (GOSH 2015). If the priming volume is not visible, then refer to the manufacturers volumes or contact the haemodialysis unit 

Flushing techniques

For detailed guidance on how to flush a CVAD refer to the clinical guideline on Central Venous Access Devices.

There are two main methods of flushing used to maintain patency - the turbulent or pulsatile flush and positive pressure (Dougherty 2006; Hadaway 2006; Dougherty and Lister 2008; RCN 2010).

Turbulent/pulsatile flush

This method is used to clear the catheter of blood or drugs that may adhere to the internal surface of the catheter. This technique utilises a rapid stop-start or push-pause method when injecting the flush solution into the catheter (Hadaway 2006; Dougherty 2006; Dougherty and Lister 2008).

This technique is based on the concept of laminar and turbulent fluid flow. Laminar fluid flows in undisturbed layers, with the fastest current in the centre of the lumen. Turbulent flow moves in swirls and eddies. Theoretically, turbulent flow removes any blood attached to the catheter wall and thus reduces the risk of catheter lumen occlusion (Hadaway 2006).

Positive pressure flushing

This technique prevents or reduces the risk of blood reflux into the catheter lumen when the syringe is detached from the hub and pressure is released. The technique involves using a smooth flush and then clamping the catheter whilst instilling the last part of the flush, so that 0.5-1ml of solution is left in the syringe immediately after which the pressure is released on the syringe.

For valved PICCs, continue to flush the PICC whilst removing the luer-slip syringe from the needleless access device - do not use a luer-lock syringe. This technique will ensure that a positive pressure is created when the syringe is removed from the PICC and consequently minimise the risk of blood refluxing into the lumen of the catheter.

This technique is not needed if using a positive-displacement or positive-pressure, valved injection cap or neutral injection cap (Richardson 2007). Always follow the manufacturers' instructions for using injection caps as different techniques are required for different caps.

Flushing volumes

The volume of the flush solution should be equal to at least twice the volume of the catheter and add-on devices (RCN 2010).

The internal volume of the catheter will differ depending on the type of catheter and its size (Dougherty 2006). Many of the long term CVADs used at GOSH will have been trimmed during insertion to fit each individual child, therefore the internal volume of the catheters will be less than the companies stated catheter priming volume.

The following flush volumes are given as a guide. The child's size and clinical condition will also dictate the amount of flush to use, which will rely on the HCP's clinical judgement at the time.


Skin tunneled cuffed CVC:  Bard 2.7Fr, 4.2Fr or Cook 4Fr (single lumen) 

Action Volume Solution
To access patency & routine access 1-2 ml Sodium chloride 0.9%
In-between / after IV medication  1-2 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 2-3 ml Sodium chloride 0.9%
Catheter accessed (daily or more) 1-2 ml Sodium chloride 0.9%
Catheter accessed (weekly or less than once a day) as a lock 0.5 ml Heparin sodium 10 units per ml

Actual catheter priming volumes: 2.7Fr=0.15ml, 4.2 Fr=0.3ml. Bard Access Systems. Cook Medical 4Fr= 0.5ml]


Skin tunneled cuffed CVC:  Cook 5Fr (dual lumen) 

Action Volume Solution
To assess patency & routine access  1-2 ml Sodium chloride 0.9%
In-between / after IV medication 1-2 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 2-3 ml Sodium chloride 0.9%
Catheter accessed (daily or more) as a lock  1 ml Heparin sodium 10 units per ml
Catheter infrequent use or at home as a lock. (Flush both lumens twice a week to maintain patency) 1 ml Heparin sodium 100 units per ml

Actual pre trimmed catheter priming volumes: 0.5ml each lumen


Skin tunneled cuffed CVC: 6.6Fr, 9.6Fr (single lumen), 7Fr, 9Fr, 10Fr and 12Fr (dual lumen)

Action Volume Solution
To assess patency & routine access  2-4 ml Sodium chloride 0.9%
In-between / after IV medication 2-4 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 3-6 ml Sodium chloride 0.9%
Catheter accessed (daily or more) 2-4 ml Sodium chloride 0.9%
Catheter accessed (weekly or less than once a day) as a lock 2 ml Heparin sodium 10 units per ml

Actual pre trimmed catheter priming volumes: 6.6 Fr=0.7ml, 9.6Fr=1.8ml, 7Fr= 0.8ml (white)/1.0ml (red), 9Fr=0.7ml (white)/1.3ml (red), 10Fr=1 .3ml (white)/1.3ml (red), 12Fr=1.6ml (white)/1.6ml (red) Bard Access Systems, Cook Medical 6.5Fr = 1.1ml


Implanted Ports (Bard low profile or Cook Petite)

Action Volume Solution
To assess patency & routine access  2-3 ml Sodium chloride 0.9%
In-between / after IV medication 2-3 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 3-6 ml Sodium chloride 0.9%
Port accessed (daily or more) 2-3 ml Sodium chloride 0.9%
Port access/de-access (weekly use) 2 ml Heparin sodium 10 units per ml
Port access/de-access (monthly or less than weekly 2 ml Heparin sodium 100 units per ml

Actual pre trimmed catheter priming volumes: 

  • Bard port chamber 0.2ml & catheter 0.6ml = total 0.8mls
  • Cook port chamber 0.35ml & catheter 0.56 = total 0.91mls

Implanted Ports (Bard large 6.6Fr or Cook Standard 6.5Fr)

Action Volume Solution
To assess patency & routine access  2-4 ml Sodium chloride 0.9%
In-between / after IV medication 2-4 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 3-6 ml Sodium chloride 0.9%
Port accessed as lock (daily or more) 2-4 ml Sodium chloride 0.9%
Port access/de-access as lock (weekly use) 2.5 ml Heparin sodium 10 units per ml
Port access/de-access as lock (monthly or less than weekly 2.5 ml Heparin sodium 100 units per ml

Actual pre trimmed catheter priming volumes:

  • Bard port chamber 0.6ml & catheter 0.6ml = total 1.2mls
  • Cook port chamber 0.62ml & catheter 0.56 = total 1.18mls

PICC open ended – Cook cuffed & uncuffed: 3Fr & 4Fr

Action Volume Solution
To assess patency & routine access  1-2 ml Sodium chloride 0.9%
In-between / after IV medication 1-2 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 2-3 ml Sodium chloride 0.9%
After catheter access as a lock 1 ml Heparin sodium 10 units per ml
Catheter access (weekly as a lock) 1 ml Heparin sodium 10 units per ml

Actual pre trimmed catheter priming volume: 3Fr = 0.5mls & 4Fr = 0.6mls

3Fr cuffed CVCs are placed as a PICC at GOS


PICC - valved: 4Fr (single) and 5Fr (dual)

Action Volume Solution
To assess patency & routine access  1-2 ml Sodium chloride 0.9%
In-between / after IV medication 1-2 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 2-3 ml Sodium chloride 0.9%
Catheter access as a lock 2-3 ml Sodium chloride 0.9%

Actual pre trimmed catheter priming volume:4Fr = 0.42ml, 5Fr = 0.35mls each lumen for the 45cm lengths


Short-term non-tunneled CVCs

Action Volume Solution
To assess patency & routine access  1-2 ml Sodium chloride 0.9%
In-between / after IV medication 1-2 ml Sodium chloride 0.9% or dextrose 5% 
Flushing after blood sampling 2-3 ml Sodium chloride 0.9%
Catheter access as a lock1  1 ml Sodium chloride 0.9%

CVCs for extracorporeal therapies (Haemodialysis/apheresis CVCs (long and short term)

Refer to the GOSH Central venous access (temporary) for extracorporeal therapies guideline for flushing information 

Note: before using the catheter the indwelling heparin must be aspirated from the appropriate lumen

References

Bishop L, Dougherty L, Bodenham A, Mansi J, Crowe P, Kibbler C, Shannon M, Treleaven J. (2007) Guidelines on the insertion and management of central venous access devices in adults. Int J Lab Hematol 29 (4): 261-78.

Bravery K. (2008) Paediatric intravenous therapy in practice. In Dougherty L and Lamb J: Intravenous therapy in nursing practice. Oxford, Blackwell Publishing.

Bravery K A and Wright L. (1998) Practical considerations of peripheral blood stem cell collection in children with solid tumours. European Journal of Oncology Nursing 2: 123-128.

Dougherty L. (2006) Central venous access devices. Care and management. Oxford, Blackwell Publishing

Dougherty L and Lister S. (2008) Vascular access devices: insertion and management. In  Dougherty L and Lister S: The Royal Marsden Hospital Manual of clinical nursing procedures. Chichester, Wiley-Blackwell.

Frey AM. (2007) Pediatric intravenous therapy. In Weinstein S M: Plumer's principles and practice of intravenous therapy: an Illustrative Procedural Guide. Philadelphia, Lippincott Williams and Wilkins

Great Ormond Street Hospital (2015) Central venous access (temporary) for extracorporeal therapies. Clinical guideline. [last accessed 29/06/16].

Hadaway L. (2006) Heparin locking for central venous catheters. The Journal of the Association for Vascular Access 11: 224-231.

Hagle M. (2007) Central venous access. In  Weinstein S M: Plumer's Principles and Practice of Intravenous Therapy: an Illustrative Procedural Guide. Philadelphia, Lippincott Williams and Wilkins.

Infusion Nurses Society (2006) Infusion nursing standards of practice. Journal of Infusion Nursing 29: S1-S92.

Loveday, H.P. Wilson, J.A. Pratt, R.J. Golsorkhi, A. Bak, J.B. Prieto, J. and Wilcox, M. (2014) epic 3: National Evidence-Based Guidelines for Preventing Healthcare-Associated Infections in NHS Hospitals in England. Journal of Hospital Infection, supplement S1-S70

National Patient Safety Agency (2008) Rapid response report NPSA/2008/RRR002. Risks with intravenous heparin flush solutions. [last accessed 29/06/16].

Nursing and Midwifery Council. (2008) Standards for medicines management. [last accessed 29/06/16].

Richardson DK. (2007) Vascular access nursing. Practice, standards of care, and strategies to prevent infection: A review of flushing solutions and injection caps. The Journal of the Association of Vascular Access 12: 74-84.

Royal College of Nursing. (2010) Standards for infusion therapy. London, Royal College of Nursing

Toft B. (2007) Independent review of the circumstances surrounding four serious adverse incidents that occurred in the Oncology Day Beds Unit, Bristol Royal Hospital for Children on Wednesday, 3 January 2007.

UK Medicines Information. (2012) Should heparin based flushing solutions be used in preference to saline to maintain the patency of indwelling intravascular catheters and cannulae? [last accessed 29/06/16].

Document control information

Lead Author(s)

Anne Ho, Central Vascular Access Team, Interventional Radiology

Additional Author(s)

Karen Bravery, Nurse practitioner & IV practice development lead for Infection, Cancer and Immunity, Infection, Cancer and Immunity

Document owner(s)

Karen Bravery, Nurse practitioner & IV practice development lead for Infection, Cancer and Immunity

Approved by

Guideline Approval Group

Reviewing and Versioning

First introduced: 
01 October 2001
Date approved: 
26 June 2016
Review schedule: 
Three years
Next review: 
26 June 2019
Document version: 
5.0
Previous version: 
4.0