Influence of multi-lumen extensions on fluid flow through intravenous cannulae.

Multi-lumen extensions used to infuse multiple fluids via a single intravenous cannula might increase resistance and so limit the flow that can be achieved. We constructed low-pressure and high-pressure models and compared the effect of two different multi-lumen extensions on flow rate. Both multi-lumen extensions reduced flows by up to 76% (p < 0.001). The effect was greatest with large cannulae and in the high-pressure model, with the longer and narrower extension most impeding flow. Multi-lumen extensions can therefore significantly impede fluid flow, and should be avoided or removed when rapid infusion is required. These effects are less important in paediatric anaesthesia where smaller cannulae are used. Manufacturers should include internal diameter or flow effects on the packaging of these extensions to assist clinicians in making such decisions.