There is blood in the tube of the indwelling needle, mostly due to blood reflux in the blood vessels, a small amount of it usually has no effect. The indwelling needle, also known as an indwelling cannula needle, is used to minimize vascular damage caused by repeated venepuncture, and can be used for continuous, repeated intermittent infusion therapy, where residual medication is flushed into the blood vessels with a sealing fluid (containing dilute heparin solution) after the infusion is completed. After inappropriate activity, a small amount of blood in the vein may reflux into the indwelling syringe tube, hence the visible presence of blood in the syringe. There is usually no blood clotting in the indwelling needle tube due to the heparin in the sealing fluid, but if there is more blood or localized skin discomfort, it is advisable to consult a physician promptly to have the indwelling needle re-processed or withdrawn.