Aim To compare the flow rates of readily available intravenous infusion devices and to compare the effect of the addition of pressure or a needle-free intravenous connector device.

Methods Several intravenous devices with different characteristics had their flow rates determined under a standard set of conditions. The flow rates were then measured with the addition of a pressure bag to the system and then with a needle-free intravenous connector device. The flow rates and change in flow rates were then analysed.

Results The results showed a general agreement with Poiseuille's law. The needle-free connector slowed the rate of flow by up to 41.4% with the greatest effect on short, wide-bore devices. The addition of pressure had a greater effect on longer devices.

Conclusions Short, wide cannulae should be used when rapid fluid resuscitation is required. Needle-free devices should not be used when rapid fluid resuscitation is needed.