Fixed-needle syringes

Dead space in syringes

All syringes have something known as "dead space". This corresponds to the small amount of space where fluid remains inside the syringe after the plunger is fully depressed. After use, the dead space contains a small amount of blood due to 2 common practices:

• Before injecting, to ensure that the needle is in the vein, users often pull up on the plunger until blood is seen to enter the syringe;
• After injecting, users often pull up on the plunger before pushing down again, to minimise the amount of product left in the syringe.

As this blood may be infected (HIV or hepatitis C), there is a risk of virus transmission if the syringe is then shared. The amount of blood remaining in the dead space of the syringe is one of the main risk factors for virus transmission. The larger the dead space, the higher the risk of transmission.

The dead space depends on the type of syringe used. The risk of virus transmission is higher with some syringes than with others.

1 ml fixed needle syringes have a low dead space of only 3 µl. The use of these syringes is therefore to be prioritised, especially if there is a risk of sharing.