Flushing and Locking of Vascular Access Devices Policy

1. Policy Statement

All vascular access devices (VADs) placed or maintained within this organization must be flushed and locked in accordance with evidence-based standards to maintain catheter patency, prevent intraluminal occlusion, reduce catheter-associated bloodstream infection (CABSI) risk, and ensure safe delivery of prescribed therapies. Flushing must be performed before each infusion to confirm patency, after each medication administration to clear the catheter lumen, and prior to locking. Locking must be performed after the final flush each time infusion ceases. All flushing and locking must use single-dose, preservative-appropriate systems, and all antimicrobial lock solutions must be aspirated and must never be flushed into the patient’s bloodstream. Clinicians must not forcibly flush a VAD against resistance, regardless of syringe size.

2. Purpose

• To maintain patency of all VADs through standardized flushing and locking practices that prevent intraluminal occlusion from thrombus formation, drug precipitate, and biofilm accumulation.
• To reduce the risk of catheter-associated bloodstream infection through hygienic single-dose flushing practices and evidence-based solution selection.
• To ensure complete clearance of administered medications from the catheter lumen following each infusion, preventing drug incompatibility reactions and residual drug delivery.
• To establish clear, device-specific, and population-specific requirements for flush and lock solution selection, volume, technique, and frequency.
• To prevent patient harm from prohibited practices including forcible flushing against resistance, use of multi-dose containers, use of sterile water for flushing, and flushing of antimicrobial lock solutions into the circulation.
• To provide reference standards for pharmacy, nursing, and vascular access clinicians regarding antimicrobial lock therapy indications, monitoring, and safety requirements.

3. Scope

This policy applies to:

• All licensed clinical staff authorized to perform VAD flushing and locking within this organization, including registered nurses, licensed practical nurses, advanced practice providers, and vascular access specialists.
• All inpatient, outpatient, emergency, critical care, procedural, home infusion, and ambulatory infusion settings operated by or affiliated with this organization.
• All vascular access device types including short peripheral intravenous catheters (PIVCs), extended dwell PIVCs, midline catheters, peripherally inserted central catheters (PICCs), non-tunneled central venous catheters (CVCs), tunneled cuffed and non-cuffed CVCs, implanted venous ports, peripheral and central arterial catheters, hemodialysis CVADs, and apheresis catheters.
• All patient populations including neonates, pediatric patients, and adults.
• Selection, preparation, administration, and documentation of all VAD flush and lock solutions.

4. Policy Requirements

4.1 Single-Dose System Requirements

4.1.1 Mandatory Single-Dose Systems

4.1.1.1 All VAD flushing and locking must be performed using single-dose systems. Acceptable single-dose systems include:

• Single-dose vials drawn up in individual syringes immediately prior to use.
• Single-use prefilled, commercially manufactured, and labeled flush syringes.

4.1.1.2 Any syringe or needle used to enter or connect to a patient’s intravenous solution container or administration set must be considered contaminated and must be discarded immediately after that use.

4.1.1.3 Intravenous solution containers, including bags and bottles, must never be used as the source for VAD flush solutions.

4.1.2 Commercially Prefilled Flush Syringes

4.1.2.1 Commercially manufactured prefilled flush syringes are the preferred product for VAD flushing when available. Evidence demonstrates that prefilled syringe use is associated with reduced CABSI rates and reduced catheter failure compared to flush syringes drawn from multi-dose or bulk containers.¹²

4.1.2.2 When administering medications that require pre-flush and post-flush, separate, new, unopened prefilled syringes must be used for each flush event. A syringe used to flush before medication administration must not be retained and reused for the post-flush.

4.1.2.3 Prefilled flush syringes must never be used for medication dilution. The following prohibitions apply:

• Prefilled flush syringes have graduation markings calibrated for flush volumes, not medication dosing.
• Prefilled flush syringes must not be relabeled.
• Drawing medication into a prefilled flush syringe risks dose loss from residual flush solution in the dead space, contamination of the medication, and medication errors.

4.1.2.4 Patients may notice taste or odor disturbances during or after flush administration, particularly with CVADs. These sensations are more common with rapid injection. Clinicians must minimize injection rate to reduce this effect and reassure patients that symptoms are transient and resolve without intervention.

4.2 Flush Solution Selection and Volume

4.2.1 Standard Flush Solution

4.2.1.1 Preservative-free 0.9% sodium chloride (normal saline, NS) is the standard flush solution for all VAD types unless contraindicated by the specific clinical situation or device type requirements outlined in this policy.

4.2.1.2 Sterile water must never be used for VAD flushing. Sterile water is hypotonic and will cause hemolysis and cellular damage upon intravascular administration.

4.2.2 Minimum Flush Volume

4.2.2.1 The minimum flush volume for any VAD is two times (2x) the internal priming volume of the complete catheter system, including the catheter itself and all add-on devices (needleless connectors, extension sets, manifolds).

4.2.2.2 Minimum flush volumes by device type, based on typical internal volumes, are listed in Table 1. Larger volumes are required when flushing following:

• Blood sampling or blood component administration.
• Parenteral nutrition (PN) administration.
• Contrast media administration.
• Administration of other viscous, lipid-based, or high-protein solutions.

4.2.3 Bacteriostatic Saline Limitation

4.2.3.1 Bacteriostatic 0.9% sodium chloride (containing benzyl alcohol as preservative) must not exceed 30 mL administered to any patient within any 24-hour period. Exceeding this limit risks benzyl alcohol toxicity.

4.2.4 Preservative Restrictions for Neonates and Infants

4.2.4.1 Only preservative-free solutions must be used for flushing and locking VADs in neonates and infants. Preservative toxicity in this population, including benzyl alcohol toxicity syndrome, is a documented risk with non-preservative-free products.

4.2.5 Medication Incompatibility with Sodium Chloride

4.2.5.1 When the prescribed medication is incompatible with 0.9% sodium chloride, the following sequence must be used:

• Flush with 5% dextrose in water (D5W) to clear the incompatible medication from the catheter lumen.
• Follow immediately with preservative-free 0.9% sodium chloride to clear the dextrose from the catheter lumen.

4.2.5.2 Dextrose must not be allowed to remain in the catheter lumen as the final substance prior to locking. Dextrose residue in the lumen supports biofilm growth and increases CABSI risk.

Table 1: Minimum Flush Volumes by Device Type

4.3 Patency Assessment

4.3.1 Pre-Infusion Patency Confirmation

4.3.1.1 Before each infusion, the VAD must be assessed for patency by flushing and aspiration for blood return. Both the presence of free-flowing blood return and the absence of resistance to flushing must be confirmed.

4.3.1.2 A 10-mL syringe, or a syringe specifically engineered to generate lower injection pressure through a 10-mL diameter barrel, must be used for VAD patency assessment. Smaller syringes generate higher injection pressures at equivalent plunger force and must not be used for patency assessment or troubleshooting of suspected occlusion.

4.3.1.3 Blood return must demonstrate the color and consistency of whole blood. Aspirate that appears clear, discolored, or inconsistent with whole blood is not acceptable confirmation of intravascular placement.

4.3.2 Sluggish or Absent Blood Return

4.3.2.1 When blood return is sluggish or absent, the following assessment steps must be taken before proceeding with infusion:

• Evaluate for external causes: closed clamps, kinked administration sets, dressing-related catheter kinking, body position effects.
• Reposition the patient and/or the extremity and reassess.
• Have the patient perform Valsalva maneuver or raise arms above the head if clinically appropriate.
• Assess alternative patency indicators, including clinical response to medications previously administered through the device, absence of resistance to gentle flush, and absence of extravasation at the insertion site.

4.3.2.2 For peripheral VADs with persistently absent blood return:

• Increase frequency of insertion site assessment.
• Plan transition to a new VAD when clinically feasible.
• Antineoplastic vesicants must not be administered through any peripheral VAD without confirmed free-flowing blood return. Administration of antineoplastic vesicants through peripheral access is contraindicated in the absence of blood return confirmation.

4.3.2.3 For CVADs with absent blood return in patients receiving vasoactive agents or inotropes where cessation of infusion is not immediately possible:

• Evaluate blood return during planned pauses in infusion, including bag changes, blood draws, and tubing changes.
• Increase frequency of insertion site assessment and clinical monitoring for signs of extravasation or catheter malposition.
• Notify the responsible provider and document the assessment, actions taken, and provider notification.

4.3.3 Resistance to Flushing

4.3.3.1 Resistance encountered during flushing must never be overcome by forceful flushing, regardless of syringe size. Forceful flushing against resistance risks catheter fracture, catheter embolism, and intravascular damage.

4.3.3.2 Systematic troubleshooting of flushing resistance must proceed in the following sequence:

• External causes: closed clamps, kinked tubing or catheter, tight dressing compressing catheter.
• Position-dependent occlusion: reposition patient and reassess.
• Internal causes: intraluminal thrombus, drug precipitate, fibrin sheath.

4.3.3.3 When external causes have been excluded and resistance persists, diagnostic evaluation must be obtained. Appropriate modalities may include chest radiograph (for CVAD tip position), color duplex ultrasound (for thrombosis), or fluoroscopy with contrast injection (for fibrin sheath or intraluminal occlusion). Consultation with the responsible provider and/or vascular access team is required.

4.3.3.4 Once patency has been confirmed, clinicians may proceed with medication administration using an appropriately sized syringe for the prescribed medication. Medication must never be transferred from the prescribed syringe to a larger syringe for the purpose of reducing injection pressure; this practice alters medication concentration and constitutes a medication error.

4.4 Flushing Technique

4.4.1 Post-Medication Flush Rate

4.4.1.1 Following intravenous push (IV push) medication administration, the VAD lumen must be flushed at the same rate of injection used for the medication. Flushing at a rate faster than the medication administration rate may result in inadvertent bolus delivery of residual medication from the catheter lumen.

4.4.2 Positive-Pressure Technique

4.4.2.1 For traditional (non-positive-pressure) syringes, a positive-pressure technique must be used to prevent blood reflux into the catheter lumen upon syringe disconnection. The technique requires leaving 0.5 to 1.0 mL of residual saline in the syringe while clamping the catheter (if a clamp is present) and disconnecting the syringe.

4.4.2.2 The specific sequence for flushing, clamping, and disconnecting from a needleless connector must follow the manufacturer’s instructions for use for the specific connector in use. The correct sequence varies by connector type (positive displacement, negative displacement, or neutral) and improper sequencing may result in blood reflux regardless of syringe technique.

4.4.3 Pulsatile Flushing

4.4.3.1 A gentle pulsatile flushing technique—defined as intermittent push-pause delivery of the flush solution in small increments—is the standard technique for VAD flushing. In vitro data suggest that pulsatile delivery may be more effective than continuous delivery in removing fibrin deposits and drug precipitate from catheter lumens.

4.4.3.2 The Centers for Disease Control and Prevention (CDC) recommends a vigorous pulsating technique specifically for CVADs. This recommendation must be implemented with clinical judgment; repeated high-pressure injection may damage vessel endothelium.

4.4.3.3 The current evidence supports a gentle pulsatile technique that balances catheter patency, medication safety, and preservation of vessel endothelium. Forceful, high-pressure pulsatile flushing intended to dislodge occlusions is not endorsed as routine practice.

4.4.4 Multi-Lumen Catheter Post-Sampling Flushing

4.4.4.1 Following blood sampling from any lumen of a multilumen central venous catheter, all lumens of the catheter must be flushed. Blood sampling from one lumen may create intraluminal pressure differentials that cause blood reflux into non-sampled lumens, increasing clot formation and infection risk.

4.5 Locking — Peripheral Intravenous Catheters and Midline Catheters

4.5.1 Locking After Each Use

4.5.1.1 All short PIVCs, extended dwell PIVCs, and midline catheters must be locked immediately after each use, following the completion of the post-administration flush.

4.5.2 Lock Solution Selection

4.5.2.1 For adult patients: preservative-free 0.9% sodium chloride is the standard lock solution for PIVCs and midline catheters. Multiple randomized controlled trials demonstrate equivalent patency outcomes between saline and heparin for peripheral devices in adult patients.

4.5.2.2 For neonatal and pediatric patients: preservative-free 0.9% sodium chloride or heparin 0.5 to 10 units/mL is acceptable for PIVC and midline locking. The evidence comparing saline and heparin for peripheral devices in neonates and pediatric patients remains inconclusive; institutional protocol or prescriber order governs solution selection for these patients.

4.5.3 Maintenance of Unused VADs

4.5.3.1 PIVCs and midline catheters that are not actively in use but are being maintained for potential therapy must be assessed, flushed with the appropriate flush volume, and relocked at a minimum of every 24 hours.

4.5.3.2 PIVCs and midline catheters that are no longer clinically required must be removed promptly. Maintaining unnecessary peripheral access for extended periods without active use is not clinically indicated and increases infection risk.

4.6 Locking — Central Venous Access Devices

4.6.1 Standard Lock Solution Selection

4.6.1.1 CVADs, including non-tunneled CVCs, tunneled CVCs, PICCs, and implanted venous ports, must be locked with preservative-free 0.9% sodium chloride or heparin per provider orders appropriate to the specific device type and needleless connector in use.

4.6.1.2 For adult patients: multiple randomized controlled trials and systematic reviews demonstrate equivalent patency outcomes between heparin and normal saline lock solutions for multilumen CVCs, PICCs, and accessed implanted ports. Either solution is acceptable for adult CVADs when supported by provider order and institutional protocol.

4.6.1.3 For pediatric patients: either heparin or preservative-free normal saline is acceptable for CVAD locking. Insufficient evidence exists to definitively establish the superior antithrombotic lock solution in the pediatric population. Prescriber order and institutional protocol govern selection.

4.6.1.4 For neonates: continuous heparin infusion at 0.5 units/kg/hour is the recommended standard for all CVADs. Umbilical arterial catheters (UACs) require continuous heparin at 0.25 to 1 unit/mL (total daily dose: 25 to 200 units/kg/day).

4.6.2 Lock Volume Calculation

4.6.2.1 The lock volume for all CVADs must be calculated as the internal priming volume of the VAD plus all attached add-on devices, with an additional overfill percentage applied per the following standards, as shown in Table 3:

• Adults and children: internal VAD volume + add-on device volume + 20%.
• Infants and neonates: internal VAD volume + add-on device volume + 10%.

4.6.2.2 Internal catheter volume information must be obtained from the device manufacturer’s instructions for use or institutional catheter volume reference document. Clinicians must not estimate catheter volume without reference to the device-specific data.

4.7 Implanted Venous Ports

4.7.1 Flushing Requirements

4.7.1.1 A minimum of 10 mL of preservative-free 0.9% sodium chloride must be used to flush implanted venous ports in adult patients. Larger volumes are required following blood component administration, parenteral nutrition, lipid emulsion, or contrast media.

4.7.2 Maintenance Flushing Intervals

4.7.2.1 When the port is not accessed for regular infusions, maintenance flushing and locking at intervals of every three months is safe and effective. The following maintenance protocol must be used: 10 mL of preservative-free 0.9% sodium chloride followed by 3 to 5 mL of heparin 100 units/mL.

4.7.2.2 When the port is accessed but not receiving regular infusions, the port must be flushed daily.

4.7.3 Lipid Administration Sequencing

4.7.3.1 To reduce lipid accumulation in the port lumen and prolong device dwell time, parenteral nutrition must be administered after intravenous lipid infusion rather than before. Following lipid infusion, flushing with 10 to 20 mL of preservative-free 0.9% sodium chloride is required before proceeding with parenteral nutrition.

4.8 Special Device Requirements

4.8.1 Hemodialysis Central Venous Catheters

4.8.1.1 Low-concentration citrate (concentration less than 5%) is the recommended lock solution for hemodialysis CVADs to reduce CLABSI risk and prevent catheter dysfunction. This recommendation is based on evidence demonstrating superior CLABSI reduction compared to heparin for hemodialysis catheter locking.

4.8.1.2 Tissue plasminogen activator (tPA) may be used prophylactically once weekly for hemodialysis CVADs to reduce occlusion rates, per provider order and in accordance with the institutional anticoagulation protocol.

4.8.2 Apheresis Catheters

4.8.2.1 High-concentration heparin and sodium citrate are used for locking apheresis catheters to maintain patency between sessions.

4.8.2.2 Clinicians must exercise caution regarding heparin-induced thrombocytopenia (HIT) risk in patients with multiple myeloma undergoing stem cell harvesting. An unusual frequency of HIT (approximately 4%) has been reported in this population with heparin lock use. Alternate lock solutions must be considered and pharmacy consultation obtained for patients in this clinical context.

4.8.3 Peripheral and Central Arterial Catheters

4.8.3.1 Arterial catheters used for hemodynamic monitoring must be maintained with a continuous infusion of either heparin 1 unit/mL or preservative-free 0.9% sodium chloride, per provider orders and institutional protocol.

4.9 Heparin Considerations

4.9.1 Source and Patient Considerations

4.9.1.1 Heparin products are commonly derived from porcine or bovine biological sources. Clinicians must inform patients of the biologic source prior to heparin lock administration and must obtain patient assent.

4.9.1.2 When a patient declines heparin due to religious or cultural considerations and normal saline is clinically appropriate for the device type and patient population, preservative-free 0.9% sodium chloride must be substituted and this substitution must be documented.

4.9.2 Indications for Heparin Replacement

4.9.2.1 Heparin lock solutions must be replaced with an alternative when any of the following conditions are present:

• Suspected or confirmed adverse drug reaction to heparin.
• Development of heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia and thrombosis (HITT).
• Occurrence of spurious laboratory values attributable to heparin contamination from a heparin-locked CVAD (heparin effect on coagulation studies, artificially elevated anti-Xa levels).

4.9.2.2 Pharmacy must be notified whenever heparin is discontinued as a lock solution for a CVAD so that alternative lock therapy can be ordered promptly.

4.10 Antimicrobial Lock Therapy

4.10.1 Indications

4.10.1.1 Antimicrobial lock solutions (antibiotic locks, antiseptic locks, or combinations) are indicated for the following clinical situations:

• Patients with a history of two or more CABSIs in whom the VAD cannot be removed.
• High-risk patient populations at the treating provider’s or infectious disease specialist’s discretion.
• Healthcare facilities with persistently elevated CLABSI rates despite full implementation of standard prevention measures and infection control bundles.²³⁴

4.10.1.2 Antimicrobial lock therapy must not be used as a routine prophylactic measure in place of standard CLABSI prevention practices.

4.10.2 Antibiotic Lock Solutions

4.10.2.1 Antibiotic lock solutions consist of supratherapeutic antibiotic concentrations, alone or in combination with heparin, formulated to achieve high intraluminal antibiotic concentrations to eradicate biofilm-associated organisms.

4.10.2.2 Heparin must be avoided in antibiotic lock solutions when Staphylococcus aureus infection is suspected or confirmed, as heparin has been shown to stimulate biofilm formation in S. aureus.

4.10.2.3 For therapeutic use (treatment of catheter-related bloodstream infection without catheter removal): antibiotic lock therapy must be initiated within 48 to 72 hours of diagnosis, in conjunction with systemic antibiotic therapy, per infectious disease consultation.

4.10.3 Antiseptic Lock Solutions

4.10.3.1 Recognized antiseptic lock solutions include ethanol, sodium bicarbonate, taurolidine, citrate, concentrated sodium chloride, and EDTA, used alone or in combination. Each carries specific efficacy, monitoring, and safety considerations:

• Ethanol: can adversely affect catheter integrity; the risk correlates with ethanol concentration and cumulative exposure duration. Catheter material compatibility must be verified before ethanol lock use.
• Trisodium citrate: monitor for protein precipitation causing lumen occlusion. Concentration must be limited to less than 12% to avoid protein precipitate formation.
• Citrate (all formulations): monitor for systemic anticoagulation and hypocalcemia. Severe hypocalcemia from citrate infusion carries a risk of cardiac arrest; this complication risk requires vigilant monitoring of calcium levels and patient symptoms.

4.10.4 Pharmacy Consultation Requirement

4.10.4.1 Pharmacy consultation is mandatory before initiating any antimicrobial lock solution to ensure:

• Physical compatibility of all solution components.
• Chemical stability throughout the intended dwell period.
• Desired antimicrobial concentration and spectrum for the clinical indication.
• Catheter material compatibility for the specific device in use.

4.10.5 Dwell Time and Administration Frequency

4.10.5.1 Antimicrobial lock solutions may require dwell times of up to 12 hours daily to achieve adequate antimicrobial effect. This dwell requirement limits the utility of antimicrobial lock therapy in patients receiving continuous infusions or frequent intermittent infusions, and must be taken into account in therapy planning.

4.10.6 Mandatory Aspiration — Prohibition of Flushing Lock Solutions

4.10.6.1 All antimicrobial lock solutions must be aspirated from the catheter lumen at the end of the locking period. Flushing antimicrobial lock solutions into the patient’s systemic circulation is absolutely prohibited.

4.10.6.2 Flushing antimicrobial lock solutions into the bloodstream promotes systemic antimicrobial resistance. Gentamicin-resistant bacterial strains arising from gentamicin lock solution use have been reported to increase CABSI rates. This outcome represents direct patient harm from protocol non-compliance.

4.10.6.3 Clinicians must document aspiration of the antimicrobial lock solution prior to each infusion or each subsequent lock application.

Table 2: Lock Solutions by Device Type and Patient Population

Table 3: Lock Volume Calculation by Population

5. Compliance

5.1 Key Performance Indicators

• Central line-associated bloodstream infection (CLABSI) rate per 1,000 central line-days, by unit and device type, benchmarked against national standards (NHSN).
• Peripheral intravenous catheter failure rate per 1,000 peripheral line-days, trended over time.
• Percentage of CVAD care encounters with documented pre-infusion patency assessment including blood return evaluation (target: 100%).
• Incidence of adverse events related to flushing against resistance (catheter fracture, embolism), reported through the adverse event reporting system (target: zero preventable events).
• Compliance with single-dose system requirements, assessed through direct observation audits and supply chain monitoring (target: 100%).
• Incidence of antimicrobial lock solution flushed into systemic circulation rather than aspirated, tracked as a serious safety event (target: zero).
• Staff annual competency completion rate for VAD flushing and locking technique.
• Pharmacy consultation compliance rate prior to antimicrobial lock therapy initiation (target: 100%).

5.2 Enforcement

Adherence to this policy is a condition of clinical practice within this organization. Clinicians who forcibly flush a VAD against resistance, use multi-dose containers or IV bags as flush sources, administer sterile water for VAD flushing, or flush antimicrobial lock solutions into the patient’s bloodstream will be subject to immediate review through the organization’s safety event management process. Repeated non-compliance with single-dose system requirements will be addressed through the performance management process. This policy will be reviewed by the Vascular Access Governance Committee and Pharmacy no less than every two years or when significant new evidence is published or regulatory guidance changes.

6. Exceptions

• Continuous heparin infusion through umbilical arterial catheters and neonatal CVADs per established neonatal intensive care protocols supersedes the single intermittent lock requirement; continuous infusion parameters must be consistent with this policy’s concentration standards.
• Patients enrolled in approved clinical trials investigating alternative flush or lock solutions may deviate from this policy’s solution selection requirements per the approved research protocol, with informed consent documented.
• In acute resource-constrained environments (mass casualty, declared shortage), the Pharmacy and Vascular Access Governance Committee may authorize temporary exceptions to prefilled syringe use, provided single-use vials drawn up immediately prior to administration are substituted. Multi-dose vials remain prohibited in all circumstances.
• The dextrose-incompatibility flush sequence (Section 4.2.5) is the required approach; exceptions may be granted only with Pharmacy consultation confirming an alternative approach that does not leave dextrose in the catheter lumen.

7. Related Documents

• Vascular Access Device Insertion Policy
• Vascular Access Device Site Care and Dressing Change Policy
• Vascular Access Device Securement Policy
• Central Line-Associated Bloodstream Infection Prevention Bundle
• Catheter-Associated Bloodstream Infection Management Policy
• Antimicrobial Stewardship Policy
• Medication Preparation and Administration Policy
• Parenteral Nutrition Administration Policy
• Chemotherapy and Antineoplastic Vesicant Administration Policy
• Hemodialysis Vascular Access Policy
• Vascular Access Therapeutic Apheresis Policy
• Umbilical Catheter Management in Neonates Policy
• Implanted Vascular Access Ports Policy
• Heparin-Induced Thrombocytopenia Recognition and Management Guideline
• Adverse Event Management and Reporting Policy
• Product Management and Device Safety Policy

8. Revision History

References