Flush volumes for central venous access devices (CVADs)

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

These include:

• Skin tunnelled central venous catheters (CVCs) (commonly referred to as Hickman^® catheters, Broviac^® catheters). These CVCs may have one, two or three separate lumens.

• Implanted ports (IP) (commonly referred to as ports, port-a-cath, Bardport®). May have one or two reservoirs/chambers.

• Peripherally inserted central catheter (PICC) (commonly incorrectly referred to as long-line, PIC, short long line). There are two types of PICC used within GOSH, open ended ie Cook^® peripherally inserted central catheter with clamps in situ or valved catheters ie Groshong^® NXT ClearVue^TM PICC). These may have one or two separate lumens.

• Long term skin tunnelled haemodialyis/apheresis CVCs (PermCath^®). 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 refered 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 has a CVAD in situ that is not listed here, contact the manufacturer of the CVAD for further information as regards flush volumes or the Intravenous Therapy team, Immunology, Cancer, Infectious Diseases (ICI) for advice.

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) 2005).

Sodium chloride 0.9% or other compatible solution must be used before, between and after the administration of incompatible medications and/or solutions (RCN 2005; National Patient Safety Agency (NPSA) 2007).

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%

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 unproven (Pratt et al 2007; Bishop et al 2007). 

A recent 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 2008).

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) (Appendix 1).

Some clinicians and manufacturer's recommend heparin flushes when CVADs are infrequently accessed (eg implanted ports) or are used for blood processing (ie apheresis or haemodialysis) (Pratt et al 2007).

Apheresis/haemodialysis catheters are commonly flushed with heparin 1,000-5,000 units per ml to maintain patency.

The requirement for heparin over 0.9% sodium chloride may be a function of catheter bore, as large bore catheters (ie 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 withdrawal of heparin.

Indeed it is not known whether withdrawing heparin from use in CVAD's would lead to an increase in occlusion and premature removal of such devices (Toft 2007).

Other studies have demonstrated an increase in infections when changing from heparin to sodium chloride 0.9% (Jacobs et al 2004; Schilling et al 2006) (Appendix 2).

Risks associated with heparin flush solutions

Decreasing unnecessary exposure to heparin is important to minimise adverse effects associated with heparin use, eg autoimmune mediated heparin-induced thrombocytopenia, allergic reactions and the potential for bleeding complications following multiple, unmonitored heparin flushes (Pratt et al 2007).

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

• Confusion with other 'look alike' 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 ie 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. ANTT must be used when accessing CVADs, hands must be decontaminated and an effective hand washing technique used before accessing a CVAD.

Clean or sterile gloves should be used when accessing CVADs (Pratt et al 2007). Refer to clinical guidelines aseptic non touch technique (ANTT) for intravenous therapy and hand hygiene.

The catheter hub/needless connector should be cleaned with an alcoholic chlorhexidine wipe for 30 seconds using friction and allowed to dry before use (Pratt et al 2007).

Exposure to heparin should be minimised (Bishop et al 2007; Pratt et al 2007). The risks of adverse effects from the use of heparin can be avoided by using sodium chloride 0.9% injection instead of heparin flushes where possible and appropriate (Pratt et al 2007).

Heparin 1-10 units/ml should be used for neonates and paediatric patients (Infusion Nurses Society (INS) 2006).

The concentration of heparin used should be the lowest possible that will maintain patency (RCN 2005).

Solutions and frequency of flushing may be dependent on whether the catheter is open-ended 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 2005; Bishop et al 2007).

Frequency of flushing can vary from daily to weekly (Dougherty and Lister 2008).

Preferably sterile sodium chloride 0.9% should be used to flush and lock catheter lumens that are in frequent use (Pratt et al 2007).

When recommended by the manufacturer, implanted ports or open ended catheters should be flushed and locked with heparin sodium flush solutions (Pratt et al 2007).

If the child is recieving 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).

Ten units per ml of heparin can also be used if the implanted port is accessed weekly eg to obtain a weekly full blood count from an oncology patient.

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 2005; 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 (NMC) 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 2005).

10 ml 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 tp 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 10 ml or larger syringe containing 0.9% sodium chloride (Dougherty and Lister 2008).

To avoid systemic heparinisation when using apheresis/haemodialyisis the high strength heparin should 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 2007).

The priming volumes are printed on the external clamp or catheter for easy reference (GOSH 2007). If the priming volume is not visible the haemodialysis unit keeps a list of priming volumes of haemodialysis/apheresis catheters in current use at GOSH.

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 2005).

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 center 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 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.

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 2005).

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 GOS will have been cut in theatre to fit each individual child, therefore the internal volume of the catheters will be less than the 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 clinician's clinical judgement at the time.

Skin tunnelled CVC:  2.7Fr, 4.2Fr, 6.6Fr  (single lumen)

 
If fluid restriction is a concern, use twice the actual catheter priming volume to calculate flush/lock volume. In practice it would be difficult to administer less than 1ml.

Bard Access Systems (Appendix 3) (Frey 2001; Frey 2007; Bravery 2008).

Skin tunnelled CVC: 9.6Fr (single lumen), 7Fr**, 9Fr, 10Fr and 12Fr (dual lumen)

Actual catheter priming volumes: 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).
 
If fluid restriction is a concern, use twice the actual catheter priming volume to calculate flush/lock volume plus add on devices. 

Bard Access Systems (Appendix 3) (Frey 2001; Frey 2007; Bravery 2008).

Implanted port large

Actual catheter priming volumes: Port=0.6ml, catheter (6.6 Fr)=0.6ml – Total 1.2mls.
 
If fluid restriction is a concern, use twice the actual catheter priming volume to calculate flush/lock volume.
 
*Note: 100 units per ml of heparin sodium is recommended to flush the IP, if the device will not be used for four weeks, to maintain patency. 10 units per ml of heparin sodium can be used after intermittent drug administration or infusion if the needle remains in situ and the device is used at least 12-hourly.

Bard Access Systems (Appendix 3)

Implanted port low profile

 
If fluid restriction is a concern, use twice the actual catheter priming volume to calculate flush/lock volume

*Note: 100 units per ml of heparin sodium is recommended to flush the IP, if the device will not be used for four weeks, to maintain patency. 10 units per ml of heparin sodium can be used after intermittent drug administration or infusion if the needle remains in situ and the device is used at least 12-hourly.

Bard Access Systems (Appendix 3)

PICC - valved: 3Fr, 4Fr (single) and 5Fr (dual)

 
If fluid restriction is a concern, use twice the actual catheter priming volume to calculate flush/lock volume.

Note: To avoid rupturing PICC line always using 10ml syringes or larger when flushing or administering drugs. Always use a pulsating positive pressure flush and flush catheter immediately if blood is visible in the catheter.

Bard Access Systems (Appendix 3) 

PICC open ended

 
If fluid restriction is a concern, use twice the approximate catheter priming volume to calculate flush/lock volume

Note: To avoid rupturing PICC line always using 10ml syringes or larger when flushing or administering drugs. Always use a pulsating positive pressure flush and flush catheter immediately if blood is visible in the catheter.

Bard Access Systems (Appendix 3)

Haemodialysis/apheresis CVCs (long and short term)

*Note: Before using the catheter the indwelling heparin must be aspirated from the catheter and lumen(s) and flushed with 10mls 0.9% sodium chloride. This is to prevent systemic heparinisation and to remove any clots present

Bard Access Systems (Appendix 3)

Short term non tunnelled CVC

 
If fluid restriction is a concern, use twice the approximate catheter priming volume to calculate flush/lock volume.

Refer to GOSH clinical guideline central venous access (temporary) for extracorporeal therapies.

Bard Access Systems (Appendix 3)

Appendices

Appendix 1 - Guidelines, manufacturer's recommendations, clinicians' opinion 

Appendix 2 - Paediatric studies

Appendix 3 - Bard Access Systems

References

Reference 1:
Pratt RJ, Pellowe CM, Wilson JA, Loveday HP, Harper PJ, Jones SR, McDougall C, Wilcox MH (2007) epic2: National evidence-based guidelines for preventing healthcare-associated infections in NHS hospitals in England J Hosp Infect 65 Suppl 1: S1-64.

Reference 2:
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.

Reference 3:
National Patient Safety Agency (2008) Rapid response report NPSA/2008/RRR002. Risks with intravenous heparin flush solutions.

Reference 4:
World Health Organisation (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

Reference 5:
Jacobs BR, Schilling S, Doellman D, Hutchinson N, Rickey M, Nelson S (2004) Central venous catheter occlusion: a prospective, controlled trial examining the impact of a positive-pressure valve device JPEN J Parenter Enteral Nutr 28 (2): 113-8.

Reference 6:
Schilling S, Doellman D, Hutchinson N, Jacobs BR (2006) The impact of needleless connector device design on central venous catheter occlusion in children: a prospective, controlled trial JPEN J Parenter Enteral Nutr 30 (2): 85-90.

Reference 7:
Infusion Nurses Society (2006) Infusion nursing standards of practice. Journal of Infusion Nursing 29: S1-S92.

Reference 8:
Royal College of Nursing (2005) Standards for infusion therapy. London, Royal College of Nursing

Reference 9:
Hadaway L (2006) Heparin locking for central venous catheters. The Journal of the Association for Vascular Access 11: 224-231.

Reference 10:
Dougherty L and Lister S (2008) Vascular access devices: insertion and management Dougherty L and Lister S In: The Royal Marsden Hospital Manual of clinical nursing procedures. Chichester, Wiley-Blackwell

Reference 11:
Nursing and Midwifery Council (2008) Standards for medicines management

Reference 12:
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.

Reference 13:
Great Ormond Street Hospital (2007) Central venous access (temporary) for extracorporeal therapies. Clinical guideline.

Reference 14:
Richardson D K (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.

Reference 15:
Dougherty L (2006) Central venous access devices. Care and management. Oxford, Blackwell Publishing

Reference 16:
UK Medicines Information (2008) Should heparin based flushing solutions be used in preference to saline to maintain the patency of indwelling intravascular catheters and cannulae?

Reference 17:
Bravery K (2008) Paediatric intravenous therapy in practice Dougherty L and Lamb J in Intravenous therapy in nursing practice. Oxford, Blackwell Publishing

Reference 18:
Frey A M (2007) Pediatric intravenous therapy Weinstein S M in Plumer's principles and practice of intravenous therapy. Philadelphia, Lippincott Williams and Wilkins

Reference 19:
Hagle M (2007) Central venous access Weinstein S M in Plumer's principles and practice of intravenous therapy. Phildelphia, Lippincott Williams and Wilkins

Document control information

Lead author(s)
Karen Bravery, Nurse practitioner & IV practice development lead for Infection, Cancer and Immunity, Infection, Cancer and Immunity

Additional authors
Anne Ho, Specialist nurse, intravenous therapy team, Infection Cancer and Immunity
Katherine Berry, Specialist nurse, intravenous therapy team, Infection, Cancer and Immunity

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

Approved by
Clinical Practice Committee

First introduced: October 2001
Date approved: 24 October 2011
Review schedule: Two years
Next review: 24 October 2013
Document version: 3.0
Replaces version: 2.0