The SASH method is a four-step flushing and locking sequence designed to keep an implanted port functioning between uses: Saline flush, Administer the medication, Saline flush again, then Heparin lock. Each letter represents a distinct action performed in order, and skipping or rushing any step raises the risk of clotting inside the catheter or introducing infection. Ports are widely used for intermittent central venous access, especially in cancer patients, and proper maintenance directly determines how long a port lasts and how safely it performs.1American Journal of Clinical Oncology. Totally Implantable Venous Access Devices: A Review of Complications and Management Strategies Getting the technique right matters more than most people realize, and a few details that seem minor can make a significant difference.
What Each Step in SASH Actually Does
The first S stands for a saline flush before you give any medication. You push sterile normal saline (0.9% sodium chloride) through the port to confirm it draws back blood and flushes without resistance. This check tells you the catheter tip is patent and properly positioned in the vein. If you cannot aspirate blood or feel resistance when pushing, something is wrong, and you should not proceed with medication.
The A is for administering the medication or infusion itself. This is the therapeutic step, the whole reason the port exists. Whether the patient is receiving chemotherapy, antibiotics, IV fluids, or a blood transfusion, the drug goes in through the accessed port.
The second S is another saline flush after the medication. This clears residual drug from the catheter lumen and the port reservoir. Some medications are irritants or vesicants that can damage the catheter material or the vessel wall if they sit in contact too long. Flushing after administration also prevents incompatible drugs from mixing inside the line if another infusion follows.
The H is the heparin lock, which fills the catheter lumen and port reservoir with a dilute heparin solution. Heparin is an anticoagulant that discourages blood from clotting inside the device while it sits idle between treatments. This final step is what “locking” actually means: you are leaving a small volume of solution inside the port to protect it until the next access.
Why Pulsatile Flushing Matters
During both saline flush steps, how you push the syringe plunger affects how well the catheter gets cleared. A steady, continuous push creates laminar flow inside the catheter, which means fluid moves fastest in the center of the lumen and barely moves along the walls. Deposits of blood, fibrin, or drug residue tend to cling to those walls. Pulsatile flushing, a push-pause-push-pause rhythm, creates brief turbulent bursts that scour the inner walls far more effectively. Fluid dynamics, flushing techniques, and sufficient flushing volumes are all important factors in adequate flushing across catheter types.2PubMed Central. Flushing and Locking of Venous Catheters: Available Evidence and Evidence Deficit
A computational fluid dynamics study examining different push volumes and speeds found that increased infusion volume and decreased infusion time improved how thoroughly saline replaced the fluid inside the catheter. But pushing too fast or too hard can create excessive shear stress on the vessel wall, so there is a practical ceiling.3PubMed Central. Evaluating pulsatile flushing by pushing method and catheter size for educating nurses on peripheral vascular patency: a computational fluid dynamics simulation analysis The general recommendation is to use short, brisk 1-mL boluses in a push-pause pattern rather than one slow, steady depression of the plunger. Most protocols call for a total of 10 mL of normal saline per flush for ports, though institutional guidelines vary.
Choosing the Right Syringe
You will typically see 10-mL prefilled saline syringes used for flushes. The syringe barrel size is not arbitrary. A smaller barrel generates higher pressure per unit of force applied by your thumb. A 1-mL syringe, for example, can produce significantly more internal pressure than a 10-mL syringe with the same thumb force, and that excess pressure risks rupturing or damaging the catheter. Research on syringe barrel volumes confirms that the force characteristics differ across sizes, with smaller barrels amplifying force.4PubMed Central. An analysis of the effect of syringe barrel volume on performance and user perception Most port manufacturers specify a minimum syringe size of 10 mL to stay within safe pressure limits. Using anything smaller risks cracking the catheter, which can cause extravasation of fluid into surrounding tissue. For the heparin lock step, many facilities use prefilled heparin syringes that are already 10 mL; if you are drawing up heparin from a vial into a smaller syringe, transfer it into a 10-mL syringe before injecting into the port.
The Heparin Lock Step in Detail
After the second saline flush, you instill the heparin lock solution. The concentration used most often in practice is 100 units per mL, with a volume ranging from 3 to 5 mL of the heparin solution.5PubMed Central. Dosage of heparin for patency of the totally implanted central venous catheter in cancer patients The goal is to fill the entire catheter lumen and port reservoir so that heparin sits in every space where blood might otherwise pool and clot. Underfilling leaves dead space where clots can form. Overfilling pushes heparin into the bloodstream, which in most cases is clinically insignificant at these low concentrations but is still unnecessary.
The range of heparin concentrations reported across studies is broad, from as low as 10 units per mL to as high as 5,000 units per mL, though concentrations at the extreme high end are uncommon for port maintenance and are more typical of dialysis catheter locks.6PubMed. Heparin versus normal saline locking for prevention of occlusion, catheter-related infections and thrombosis in central venous catheter in adults: Overview of systematic reviews In pediatric oncology, a practice change from 100 units per mL down to 10 units per mL showed no increase in complications: catheter occlusion rates and positive blood culture rates were statistically similar before and after the dose reduction.7PubMed Central. Impact of decreased heparin dose for flush-lock of implanted venous access ports in pediatric oncology patients This suggests there may be room to use lower concentrations than tradition dictates, though you should always follow your facility’s specific protocol.
Maintaining Positive Pressure During Needle Withdrawal
One of the most commonly overlooked details in port care is what happens as you pull the Huber needle out. When the needle exits the port septum, a tiny vacuum can suck blood back into the catheter tip, a phenomenon called reflux. That small volume of blood is enough to seed a clot inside the lumen. An experimental study found that applying positive pressure during needle withdrawal reduced the incidence of reflux by nearly 80%, dropping it from 99% to about 22%.8PubMed. Totally implantable port management: impact of positive pressure during needle withdrawal on catheter tip occlusion (an experimental study) When reflux did occur under positive pressure, the volume of blood drawn back was roughly half what happened without the technique.
A separate observational experiment confirmed that positive pressure during needle withdrawal reduced reflux compared to simply flushing with positive pressure and then withdrawing normally.9Journal of the Association for Vascular Access. Observational Experiment of Catheter Reflux During Huber Needle Withdrawal In Two Countries In practical terms, this means you should still be slowly pushing saline (or the tail end of your heparin lock) as you pull the needle out, rather than clamping the extension tubing first and then withdrawing. Many newer needleless connector systems and pre-slit septum designs claim to maintain positive displacement automatically, but the evidence for manual positive-pressure withdrawal is stronger and costs nothing extra.
Scrubbing the Hub Before Every Access
Aseptic technique during port access is the single most controllable factor in preventing catheter-related bloodstream infections. The needleless connector or hub at the end of the extension set is the main entry point for bacteria after initial port placement. Research has found that a third to nearly half of needleless connectors become contaminated, and compliance with hub disinfection can be as low as 10% in some clinical settings.10PubMed Central. Disinfection of Needleless Connector Hubs: Clinical Evidence Systematic Review Poor compliance with hub disinfection and flushing procedures is a significant risk factor for central line-associated bloodstream infection, or CLABSI.11PubMed Central. Prevention of Catheter-Related Infections and Complications: A Narrative Literature Review of Vascular Care and Maintenance
The standard recommendation is to scrub the hub with 70% alcohol for at least 15 seconds using friction, though some guidelines call for up to 60 seconds. Passive alcohol disinfection caps, which sit on the connector between uses and continuously bathe it in alcohol, have been shown to reduce infection rates by roughly half to as much as 86%.10PubMed Central. Disinfection of Needleless Connector Hubs: Clinical Evidence Systematic Review One study examining chlorhexidine gluconate combined with 70% alcohol for hub disinfection found a 65% reduction in CLABSI events compared to alcohol swabs alone.12Journal of the Association for Vascular Access. The Use of 3.15% Chlorhexidine Gluconate/70% Alcohol Hub Disinfection to Prevent Central Line-Associated Bloodstream Infections in Dialysis Patients If your facility uses disinfection caps, leave them on until you are ready to access the line, then scrub again before connecting your syringe.
Does the Lock Even Need to Be Heparin?
This is one of the more actively debated questions in port maintenance. A growing body of evidence suggests that normal saline alone may be as effective as heparin for locking implanted ports. A study comparing the two directly found that saline was as effective as heparin in maintaining port patency, and eliminating heparin did not increase catheter occlusion rates. The difference in cost between saline and heparin locks was statistically significant, favoring saline.13PubMed. Implanted Port Patency: Comparing Heparin and Normal Saline
This finding matters because heparin, even in small flush doses, carries a real if uncommon risk. Heparin-induced thrombocytopenia, or HIT, is an immune-mediated reaction where the body forms antibodies against heparin-platelet complexes, paradoxically causing dangerous blood clots. A prospective study identified 23 patients who developed HIT from heparin exposure solely through catheter or filter flushes, not from therapeutic heparin doses.14PubMed. Thrombocytopenia following heparin flush For patients with a known history of HIT, heparin locks are contraindicated entirely. Citrate-based locking solutions have emerged as an alternative, and a systematic review and meta-analysis of randomized controlled trials has examined citrate as a potential substitute.15PubMed Central. Citrate as a safe and effective alternative to heparin for catheter locking: a systematic review and meta-analysis of randomized controlled trials
Despite the evidence that saline may suffice for ports specifically, many institutions still default to heparin locks based on long-standing policy. If you are a patient managing your own port care at home or an infusion nurse following facility protocol, the practical advice is straightforward: follow whatever your institution or oncology team prescribes, but know that the shift toward saline-only locks is supported by evidence and is not fringe thinking.
How Often Does a Port Need to Be Flushed?
When a port is not being used for active treatment, it still needs periodic maintenance flushes to prevent the catheter from clotting off. The traditional recommendation has been every four weeks, but several studies have tested longer intervals. A systematic review and meta-analysis concluded that extending the flush interval to eight weeks did not increase the incidence of complications or catheter occlusions.16PubMed. Prolonging the flush-lock interval of totally implantable venous access ports in patients with cancer: A systematic review and meta-analysis The same review noted, however, that data on intervals of three months or longer remained inconclusive at the time.
More recent work has pushed the boundary further. A study specifically examining 12-week maintenance intervals found that extending port flushes to every 12 weeks did not increase the incidence of port-related adverse events and was considered medically safe.17PubMed Central. Is There a Relationship Between Frequency of Port-Care Maintenance and Related Complications in Patients With Cancer? A separate study went further still, reporting that extending the flushing interval to up to four months remained medically safe and drastically reduced costs.18PubMed. Interval between port catheter flushing can be extended to four months For patients who have completed chemotherapy and are keeping their port “just in case,” these longer intervals mean fewer clinic visits, less needle access to the port septum, and lower out-of-pocket costs. Still, the safest approach is to follow whatever schedule your care team recommends and discuss extending intervals if monthly visits are burdensome.
What Happens When a Port Occludes
Even with perfect SASH technique, ports occasionally clot off. The catheter tip sits in a large central vein, and over time, a layer of fibrin and thrombus can coat the catheter. Histological examination of failed catheters has shown thrombus formation both with and without a surrounding protein coating, the so-called fibrin sheath.19PubMed. Thrombus on indwelling central venous catheters: the histopathology of “Fibrin sheaths” A partial occlusion might let you flush in but not draw blood back; a complete occlusion blocks flow in both directions.
The good news is that an occluded port does not automatically mean surgical removal. Thrombolytic agents, drugs that dissolve blood clots, can restore patency in most cases. Alteplase, the most commonly used agent for this purpose, clears about half of obstructed catheters within 30 minutes and achieves roughly 86% overall clearance after up to two doses.20PubMed Central. Thrombolytic therapy for central venous catheter occlusion In one series of 50 occluded ports treated with alteplase using a gentle push-and-pull instillation technique and a 30-minute dwell time, all ports were successfully restored without requiring surgical intervention.21PubMed Central. Efficacy and safety of a single 2 mg dose or 4 mg double dose of alteplase for 50 occluded chest ports using a unique instillation technique A larger study of 165 patients reported a cumulative success rate of about 93%, with initial thrombolysis working in 77% and repeat treatments recovering most of the remainder.22PubMed. Local low-dose thrombolysis for safe and effective treatment of venous port-catheter thrombosis
If your port does not flush or draw back, do not try to force it with a syringe. Forceful flushing can dislodge a clot into the bloodstream or rupture the catheter. Report the problem to your care team so they can attempt a thrombolytic instillation, which is a straightforward bedside procedure in most infusion centers.
Putting It All Together at the Bedside
In real practice, the SASH sequence unfolds in a rhythm that becomes second nature. You scrub the hub, flush with saline using pulsatile boluses, confirm blood return, administer the medication, flush again with saline, then instill the heparin lock while maintaining positive pressure as the needle comes out. Each step protects against a different failure mode: the hub scrub prevents infection, the first flush confirms patency, the second flush clears residual medication, and the heparin lock prevents clotting during the idle period. Ports provide reliable access for blood withdrawal and medication administration with minimal disruption to a patient’s lifestyle, but that reliability depends on consistent, correct maintenance.23PubMed. Venous access ports: indications, implantation technique, follow-up, and complications
A few common mistakes trip people up. Forgetting to aspirate for blood return before the first flush means you might infuse medication into a clotted line without knowing it. Clamping the extension tubing before withdrawing the needle, instead of maintaining positive pressure during withdrawal, invites blood reflux. Using a syringe smaller than 10 mL generates dangerous pressure inside the catheter. Rushing the hub scrub, or skipping it because “I just cleaned it a minute ago,” is the kind of shortcut that occasionally leads to a bloodstream infection. And failing to give the heparin lock its full prescribed volume means the catheter tip sits exposed to blood rather than bathed in anticoagulant.
For patients managing port care at home with a visiting nurse or doing their own flushes between treatment cycles, keeping a written checklist of the SASH steps is not a sign of inexperience. Experienced infusion nurses perform this sequence dozens of times a week and still follow a mental checklist because consistency, not memory, is what keeps a port safe and functioning.