Should a 100 mL saline flush be performed every 30 minutes during hemodialysis when the patient is receiving systemic heparin?

Hemodialysis Saline Flushing with Systemic Heparin

When patients are receiving systemic heparin during hemodialysis, the routine 100 mL saline flush every 30 minutes is unnecessary and should be discontinued. The saline flushing protocol is specifically designed for heparin-free dialysis to prevent circuit clotting, not for patients already receiving anticoagulation 1, 2.

Understanding the Context of Saline Flushing

The intermittent saline flush protocol exists solely as an alternative anticoagulation strategy when heparin cannot be used:

• Heparin-free dialysis protocols were developed for patients with increased bleeding risk, where 100 mL saline flushes every 30 minutes (or every 15 minutes in some protocols) help maintain circuit patency without systemic anticoagulation 1, 2
• When comparing heparin-free methods, continuous saline infusion at 200 mL/hour is actually superior to intermittent 100 mL flushes every 30 minutes, with 76% versus 52% success rates in preventing circuit clotting 1
• The most successful heparin-free protocol combines aggressive circuit priming, maximized blood flow (up to 400 mL/min), and 100 mL saline flushes every 15 minutes, achieving 99% success without anticoagulation 2

Why Saline Flushing Is Contraindicated with Systemic Heparin

Adding saline flushes to systemic heparin provides no additional benefit and creates unnecessary risks:

• Heparin is the standard anticoagulant for maintaining extracorporeal circuit patency during hemodialysis, and when used systemically, it already prevents circuit clotting 3
• Combining both interventions offers no documented advantage in circuit patency 1, 2
• The saline flush protocol was never designed or studied for use alongside systemic heparin—it exists as an alternative when heparin is contraindicated 1, 2

Clinical Algorithm for Anticoagulation During Hemodialysis

If the patient can receive heparin:

• Use standard systemic heparin dosing per your facility protocol 3
• Do NOT add saline flushes 1, 2
• Monitor for bleeding complications and heparin-induced thrombocytopenia 4

If the patient has bleeding risk or heparin contraindication:

• Implement heparin-free protocol with either:
  • Continuous saline infusion at 200 mL/hour (preferred method) 1, OR
  • Intermittent 100 mL saline flushes every 15-30 minutes 1, 2
• Maximize blood flow to 350-400 mL/min 2
• Aggressively prime the circuit to eliminate all air 2
• Use bloodlines without blood-air interface 2

If the patient requires regional anticoagulation:

• Consider regional citrate anticoagulation as an alternative to both systemic heparin and saline-only protocols 3

Common Pitfalls to Avoid

The "heparin flush syndrome" can occur when heparin is inadvertently overused through multiple routes (therapeutic dosing plus flush protocols), leading to serious hemorrhagic complications requiring surgical intervention 4. This historical case report underscores why combining anticoagulation strategies without clear indication is dangerous.

Access-related factors that increase clotting risk in heparin-free dialysis include catheter access (versus fistula), low blood flow rates (<300 mL/min), high arterial line pressures, and need to reverse arterial/venous lines 2. These factors do not justify adding saline flushes when systemic heparin is already being used.