Real-Time Blood Propofol Monitoring

Propofol is an intravenous drug used to induce general anaesthesia (unconsciousness or drug induced sleep). It can also be administered by continuous infusion to keep the patient asleep and has substantial benefits for patients compared with the use of anaesthetic gases. These benefits include a carefully controlled, smooth induction of anaesthesia and a rapid, high quality recovery with a very low incidence of nausea. Propofol has less impact on memory, especially in susceptible patients. Patients who have cancer and are anaesthetised with propofol are more likely to be alive 5 years later than those given gaseous anaesthesia. Emerging laboratory evidence is helping to explain this.

There are benefits to the anaesthetist too. Some patients cannot be anaesthetised with a gas whilst equipment or environmental concerns prevent its use in others. The anaesthetist has no worries about the patient awakening during a difficult instrumentation of the airway (during which a gas cannot be delivered).

Propofol infusions are also used extensively to sedate patients (make them calm and sleepy but still responsive) such as those in intensive care units.

During gaseous anaesthesia the gas can be measured in the patient's breath, this shows that it is being delivered to the patient as well offering a measurement of how much is in their system. During intravenous anaesthesia it would be ideal if the amount of propofol in the blood could be monitored and displayed continuously. Such a 'real-time' monitor does not currently exist. Blood propofol concentrations can be measured by sending samples to a laboratory but the delay means that this does not meet the anaesthetist's need for immediate and continuous information.

A real-time blood propofol monitor would increase patient safety by:

* Providing evidence that the drug is being delivered to the patient (and thus a rapid indication of an accidentally disconnected infusion line).

* Indicating how deeply the patient is anaesthetized or sedated

* Refining the dosing calculations built into anaesthetic infusion pumps

* Moving toward personalised anaesthesia by adjusting drug doses to individual patients

This application is being made to support the development of a functioning prototype real-time blood propofol measuring system that works in a laboratory. Required milestones include the invention of a sensor that detects propofol at clinically relevant concentrations, integrating it into a recovery system for use in blood, and linking it to a data display. Further work will be required to produce a clinically useful monitor.