Arterial catheters are used in critical care units to continuously monitor blood pressures and to obtain blood samples without performing multiple venipunctures. For decades arterial catheters have been maintained with a pressurized heparinised 0.9% normal saline to prevent thrombus formation. The use of heparin for its pharmacological properties as an anticoagulant. Research evidence indicates that short term arterial lines may be maintained effectively and at a reduced cost by using normal saline instead of heparinised saline.