Anaesthesia
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This study compared the predicted effect-site concentration of propofol at loss and recovery of consciousness when using target-controlled infusion devices with the same pharmacokinetic model (Marsh) but a different plasma effect-site equilibration rate constant (ke0 ), the Diprifusor(TM) (ke0 0.26 min(-1) ) and Base Primea™ (ke0 1.21 min(-1) ). We studied 60 female patients undergoing minor gynaecological surgery under general anaesthesia. ⋯ In conclusion, the effect-site concentration of propofol differs depending on the ke0 , despite the use of the same pharmacokinetic model. Therefore, the ke0 should be considered when predicting loss and recovery of consciousness based on the effect-site concentration of propofol.
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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). ⋯ 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.