Rate-controlled analgesia: a laboratory evaluation of a new infusion device

We report an evaluation of the Bard Harvard Mini Infuser, one of a new generation of agent-specific intraoperative infusion pumps which are designed for use by the anaesthetist. This pump permits potent intravenous anaesthetic agents to be used in pharmacokinetically designed dosage regimens. The controls are calibrated directly in kg body weight and micrograms per minute rather than the usual settings of ml of solution per hour. The performance was assessed by measuring the volume delivered over given time intervals and all safety functions were tested at least three times. This device was found to be acceptably safe and accurate. Two points to note are that it must be purged every time before it is connected to the intravenous infusion and if an occlusion is suddenly relieved, the patient can receive an 'accidental bolus' of up to 1.18 ml of drug. The main advantage of this pump is that it uses undiluted drug direct from the ampoule and does not require any calculations or dilutions prior to use. However, this restricts its use to drugs with a concentration of 500 mcg/ml and in effect means that it is suitable mainly for infusion of alfentanil.