Vascular Access Devices: Flushing Technology

Technology of Flushing Vascular Access Devices

• Catheter lumen patency maintenance is an ongoing challenge
• Catheter flushing is the primary nursing intervention used to prevent lumen occlusion from both thrombotic and precipitate causes
• The catheter and all devices attached to it must be regarded as a system
• Each component directly affects the others
• The technology of catheter flushing includes:
  • The flush solution
  • The source of these solutions
  • Syringe design
  • Mechanical pumps
  • Needleless injection systems
  • Catheter design
• Effective catheter flushing is a combination of technique and technology
• Proper understanding of how both technique and technology must work together is essential

Expanding the Purpose of Flushing

• Occlusion is a problem with all types of vascular access devices
• Flushing aims to fill the entire catheter and any add-on devices with fluid to "lock" the system
• Flushing also prevents blood backflow into the lumen.
• Healthcare professionals must consider catheter-flushing technology and its impact on catheter-related bloodstream infections (CR-BSIs)
• Healthcare professionals must assess all the components in the system and how they work together to assess catheter-flushing technology
• The Infusion Nursing Standards of Practice defines 2 purposes of catheter flushing:
  • Maintain catheter patency
  • Prevent contact between incompatible medications or fluids that could produce a precipitate
• Traditionally, 0.9% sodium chloride and heparinized sodium chloride have been used
• Because of the problem associated with CR-BSIs, healthcare professionals may expand the purpose for flushing and locking the catheter
• Flushing also reduces intraluminal biofilm

Biofilm

• Biofilm is a community of microorganisms surrounded by a slime matrix
• The slime matrix protects the organisms from antibiotics, white blood cells, and all other anti-infective mechanisms
• Biofilm develops on virtually all indwelling vascular access devices
• It attaches to both the internal and external catheter surfaces
• It has been found inside needleless injection devices
• Planktonic or free-floating bacteria adhere to the catheter surfaces and begin to form a biofilm at very high flow rates
• Resident flora in the deep layers of the epidermis attach to the outer catheter surface during catheter insertion as it passes through the skin
• Organisms enter the internal catheter lumen during hub manipulations like medication administration, tubing and cap changes, and flushing procedures
• Catheters dwelling for short periods acquire more biofilm on their outer surfaces
• More biofilm accumulates on the internal surface of longer-term devices
• A study of short-term, nontunneled, non-cuffed central venous catheters shows extraluminal and intraluminal pathways as significant sources of CR-BSI
• Using pulse-field gel electrophoresis with 1,263 central venous catheters, 45% CR-BSIs were extraluminally acquired
• 26% were intraluminally acquired
• The mechanism could not be determined in 29%
• Biofilm detaches from the catheter surface by enlargement of cell clusters, detachment, reattachment of single cells/clumps, and rolling motility
• The mechanism by which a biofilm produces a bloodstream infection (BSI) is poorly understood
• Possible mechanisms include detachment of cells/clumps of biofilm, production of endotoxins, and alterations in the patient's immune system
• Interaction between flushing techniques, technology, biofilm development, and subsequent BSI is not well understood, requires careful study
• Each time a catheter is accessed, reduce the introduction of organisms into the lumen
• One method for eradicating biofilm is the use of differing antimicrobial fluids to lock the catheter
• Three fluids have been studied:
  • Minocycline and disodium ethylenediaminetetraacetate (EDTA)
  • Tetra-sodium EDTA
  • Ethanol
• Locking the catheter with a variety of antibiotic solutions treats existing infections to salvage catheters
• Locking the catheter is not recommended for routine prophylaxis against CR-BSIs due to the potential for antibiotic resistance
• EDTA was suggested as a catheter-locking solution ~15 years ago because it has anticoagulant activity and inhibits growth of Staphylococcus and Candida species
• Animal studies using minocycline and disodium EDTA (M-EDTA) found it to be effective at preventing bacteremia, septic phlebitis, and endocarditis.
• In vitro and ex vivo studies demonstrated effectiveness of M-EDTA against fresh and mature biofilm on catheter surfaces
• M-EDTA produced a 9-fold reduction in BSI compared with heparin in a randomized, prospective trial with hemodialysis patients
• A study of implanted ports in pediatric cancer patients demonstrated no infections/thromboses with M-EDTA, as compared with heparin flush (2.23 infections per 1,000 catheter days reported)
• The dosage used in these studies was 3 mg of minocycline and 30 mg of EDTA per milliliter of sterile water
• 2 mL of the solution was used to flush and lock the catheter for 24 hours.
• Minocycline recently withdrawn from the US market, shifting research focus to 40 mg of tetrasodium EDTA per milliliter
• In vitro studies demonstrated significant biofilm reduction when exposed for 21 and 24 hours
• Ethanol use to lock a catheter is in clinical trials evaluating treatment of catheter-related infection
• Broviac catheters in 79 pediatric oncology patients with positive blood cultures/clinical signs of CR-BSI were treated with ethanol locks or antibiotics
• 18 patients were treated 24 times with 2.3 mL of 74% ethanol solution for 20-24 hours in the experimental group
• 13 children received 15 courses of systemic antibiotics in control group
• 67% in ethanol-treated group showed no infectious signs for 4 weeks after treatment, compared to 47% of group receiving antibiotics
• Several brands of polyurethane catheters warn against use of alcohol on or in them
• One in vitro study tested changes in type of polyurethane during exposure to 70% ethanol for up to 9 weeks and reported no changes in mechanical/structural properties
• Other new formulations of polyurethane are more tolerant of alcohol.
• Follow manufacturers' instructions carefully.
• Further research to assess the length of time these novel flush solutions must remain inside the catheter lumen to effectively reduce the biofilm is needed

Flush Solution Containers

• Traditionally, multiple-dose containers have been used for catheter flush solution, including 30-mL vials of sodium chloride and 250-, 500-, or 1,000-mL bags of sodium chloride
• Risks of using multiple-dose containers far outweigh their benefits
• Bacterial contamination of multiple-dose vials is reported to be as high as 23%
• The vials contain bacteriostatic benzyl alcohol, not bacteriocidal
• Gram-negative bacteria are least sensitive to benzyl alcohol, which has no effect on fungi or viruses
• Bacteriostatic sodium chloride should not exceed more than 30 mL in a 24-hour period for adults, and is contraindicated for neonates
• Adult restrictions were derived from an animal study, with data extrapolated to humans
• The FDA imposed neonatal restrictions in the mid-1980s.
• A study in a 1,300-bed hospital collected 227 open multiple-dose vials from 47 nursing units:
  • 77 (34%) with sodium chloride
  • 41 (18%) with heparin
  • No opening date found on 113 (50%) of vials
  • No label of type of medication appeared on 2 of vials
  • 7 vials had no concentration of medication
  • Of 114 dated vials, 15 had been expired for up to 14 days, and 50% had no preservative
  • One vial/spike pin grew Staphylococcus epidermis, common CR-BSI organism
• Multiple uses of preservative-free vials were eliminated because of this study
• Another study demonstrated approximately 8% of syringes prepared by nurses were contaminated at the syringe tip, tip cap, or fluid.
• The rate can be by a lack of environmental control by using a laminar air-flow workbench and touch contamination
• Healthcare-acquired infections have been linked to multiple-dose vials used for catheter flushing
• This includes polymicrobial BSI from Enterobacter cloacae, Pseudomonas aeruginosa, malaria, hepatitis B/C, and human immunodeficiency virus (HIV)
• Potential causes include practices of poor-hygiene and access of the vial with a contaminated syringe
• Use of large-volume fluid containers as a source for catheter-flushing solution has been a major concern for many years
• They are still practiced
• Reported outbreaks include Klebsiella pneumoniae bacteremia in a liver transplant unit, Pseudomonas cepacia bacteremia among oncology clinic patients, and combinations of Enterobacter cloacae, Klebsiella pneumoniae, and Citrobacter freundii in medical and cardiac step-down units
• The Morbidity and Mortality Weekly Report stated in 2003, "Do not use bags or bottles of intravenous solution as a common source of supply for multiple patients."
• Single-dose containers, including vials of preservative-free normal saline and prefilled syringes, are strongly recommended by the Institute for Safe Medication Practices and the Joint Commission
• The INS standards of practice and CDC guidelines emphasize the use of single-dose containers
• The 2006 National Patient Safety Goals from JCAHO require that all medication containers be labeled, including those containing saline and heparin used for catheter flushing
• A single-dose container means single-use
• A vial should not be entered more than once
• A prefilled syringe should be attached only once to the injection site on the catheter system

Syringes

• Smaller syringes generate higher pressures than larger syringes, impacting the risk of catheter damage
• Use of a 5- or 10-mL syringe for catheter flushing is recommended
• Individual hand strength varies by size/musculature
• Force must be applied to move a syringe plunger down the barrel so that fluid can enter the catheter
• Applied force that has resistance in the catheter will lead to intraluminal pressure along with catheter rupture
• Force required to move most prefilled syringe plungers is ~ 3.5 pounds per square inch (PSI)
• Approximated 29 PSI is produced when 3.5 PSI is applied to the plunger of a 3-mL syringe, compared to 11 PSI for a 10-mL syringe
• Excessive force can lead to catheter damage, despite syringe size
• Interaction between the syringe and the fluid flow dynamics within the catheter are important
• With traditional syringes, flushing fluid can compresses the tip on the end of the plunger rod
• Detaching the syringe from the catheter hub removes the nurse's hand from the plunger rod, allowing tip expansion, leading to blood reflux into the catheter lumen
• Use of prefilled syringes to prevent this rebound problem may enhance catheter lumen patency

Mechanical Pumps

• Two types of mechanical pumps:
  • Mechanical pump with a multichamber bag (e.g., Autodose, Tandem Medical, San Diego, CA)
    • Commonly used in homecare
    • The bag contains 4 separate chambers: 1 each for sodium chloride, the drug and diluent, sodium chloride, and heparinized sodium chloride
    • The preattached tubing has a manifold that allows each fluid to run sequentially
    • The bag is placed inside the pump containing a flat spring plate, the tubing is connected to the catheter hub, the pump doors are closed, and the start button is activated to flow fluid from each chamber in the correct sequence
  • Elastomeric balloon pump
    • Can be filled with sodium chloride and connected to the catheter hub to produce a constant flow of sodium chloride at 0.5 mL per hour
    • Intermittent medication is given via a side injection port on the pump tubing

Needleless Injection Systems

• Concern over needlestick injuries led to the development of needleless injection systems (NIS)
• In 1992, the FDA called for the elimination of all needles used to connect multiple intravenous administration sets together
• The Bloodborne Pathogen Standard from OSHA now mandates these devices
• These systems can be divided by the type of fluid movement through them
  • A negative-displacement needleless injection system allows blood to reflux into the catheter lumen when the tubing or syringe is disconnected
  • A positive-pressure flushing technique is required when a negative-displacement device is used
  • A positive-displacement needleless injection system reserves a small amount of fluid to push toward the catheter tip at disconnection of the syringe/tubing, preventing blood from remaining inside the lumen
  • A neutral displacement needleless system will not allow fluid to move in either direction when tubing or a syringe is disconnected
• Negative- and positive-displacement devices are dependent upon flushing technique, so all nurses need to understand the type of device being used.
• Positive-pressure flushing is needed along with a negative-displacement device
• INS defines positive pressure as constant/even force within a catheter lumen that prevents blood reflux via injecting or withdrawing at the catheter hub while injecting.
• Positive-pressure flushing techniques can prevent proper function of a positive-displacement NIS and should not be used with these devices.
• For facilities with policies calling for a clamp on the catheter to keep it closed when not in use and a positive-displacement device is used, the nurse must disconnect, allow time for positive fluid displacement, then close.
• Syringe plunger rod compression and syringe/tubing disconnection cause blood reflux.
• Results of available research cannot overcome syringe compression reflux, as it relates to blood reflux caused by disconnection, even with a positive-displacement NIS will displace blood reflux.
• Catheter lumen length that is affected by blood reflux depends on catheter lumen size
• Smaller lumen diameter catheters will have more length filled with blood, compared to larger lumens which will have a shorter length of reflux
• Blood moving into the catheter lumen will have limited contact only with the heparinized sodium chloride left in the lumen

Needleless Injection Systems and Infection

• CDC guidelines address infection risk with NIS use, stating does not increase CR-BSI incidence when used per manufacturer instructions
• NIS use reduces healthcare workers needlestick injury risk, and subsequent bloodborne diseases transmission
• Newly released data raised potential increased BSI risk related to devices
• Five institutions have documented a BSI increase after changing from a split-septum or blunt-cannula device to a Luer-activated mechanical valve product
• In these same facilities, BSI rates returned to original after changing back to split-septum device
• Even when re-education is done on catheter insertion/maintenance, 2 hospitals that have not changed the NIS product have still reported high rates of BSI
• This problem could be caused by infection-control practices or by characteristics of the device design
• A large teaching facility reports a 4-fold increase in BSI after changing from mech. valve to a positive-displacement mech. valve
• Positive-displacement catheter occlusion was examined with split-septum (151 catheter lumens) and positive-displacement mechanical valve device (161 catheter lumens)
• Peripherally inserted central catheters (PICCs) and tunneled and non-tunneled catheters ranging from 1.9 to 12-Fr included
• Complete occlusions occurred in 11.9% of split-septum group compared to 3.7% of positive-displacement group
• Partial occlusions observed in 3.3% of split-septum group and 8.1% of positive-displacement group
• Catheter infection was reported in 8.8 in split-septum group and 15.5 in positive- displacement group per 1,000 catheter days
• Only significance was for complete occlusions
• In vitro studies found gram-negative bacteria biofilm inside NIS
• Whole blood can enhance biofilm formation and adhesion, although blood aspiration is necessary for catheter patency
• It is unknown optimal interval for frequency of changing NIS
• CDC guidelines advised changing of needleless devices in same interval as IV administration set.
• INS allows changing at least every 7 days, and blood in catheter is appropriate for intermittent medications
• Concern about inside an NIS lead some facilities with blood procedure.
• Color of these devices allows actually inside the for examination available.
• When SASH saline, administer a heparin is hub is 8 connections.
• Home-care infection over days rather fluids source
• Luer activated NIS: requiring was third cannula In patients device per than tap

Catheter Technology

• Catheter brands integral blood system Systems, CA design CA medical state sodium is
• Groshong be catheters catheters' use

Catheter Design Factors

• The should or It needs