Unfractionated Heparin (Peripheral/Central Line Flush)

How it works

Heparin potentiates antithrombin, accelerating inactivation of thrombin and factor Xa, which prevents fibrin clot formation within the catheter lumen.

Prescribing in practice

• Confirm the correct flush strength is selected and labelled, as inadvertent use of high-strength heparin vials in place of a dilute flush has caused fatal haemorrhage; saline-only locking is now preferred for many lines per local policy.
• Withhold and seek haematology advice in any patient with a history of heparin-induced thrombocytopenia, as even small flush exposures can trigger or perpetuate the reaction.
• Follow local vascular access guidance on flush technique (pulsatile flush, positive-pressure disconnection) and on whether heparin or saline locking is indicated for the specific device.

Monitoring

Routine coagulation monitoring is not required for flush-only use, but observe the catheter for patency, bleeding at the insertion site, and signs of thrombocytopenia with repeated exposure.

Counselling the patient

• Report any bleeding, bruising, or swelling around the line to staff.
• Tell clinicians if you have ever reacted badly to heparin.

Evidence & guidelines

Heparin and saline catheter locking are long-established practice, with current MHRA and NICE-aligned vascular access guidance increasingly favouring saline to reduce dosing errors and heparin-related harm.