Reaction Time Monitored Patient Maintained Propofol Sedation: a Volunteer Safety Study

Patients receiving conscious sedation for dentistry and endoscopy are usually treated with intermittent bolus doses of intravenous midazolam (administered by the operator-sedationist). The safety of such a regime has been questioned with reports of up to 13 % of patients desaturating to below 80 % in the recovery area following sedation for endoscopy. Mortality occurs in 0.05 % of endoscopy patients (with approximately 60 % of this being due to hypoxaemia). The aim of our work, therefore, is to look at providing sedation that is both safer as well as being efficacious.

The drug propofol, the agent most commonly used to induce general anaesthesia in the UK, is also frequently administered intravenously by anaesthetists in low doses to provide conscious sedation for patients undergoing unpleasant procedures i.e. patients become relaxed, anxiety-free, but maintain verbal contact throughout.

The technique of patient maintained sedation using the drug propofol (the patient can increase the amount of sedation (and propofol) they receive by pressing a demand button attached to a standard infusion device) has been used by anaesthetists and evaluated since 1997.

Several recent studies published and submitted for publication by this research group on patient maintained sedation using the drug propofol have shown this method of sedation to be safe and effective in dental patients (over 120 patients studied and no cases of over sedation). It was also shown that this method, when compared to the established method of sedation in oral surgery (the dentist administering doses of midazolam intravenously), produced both quicker recovery and less anxiety prior to the surgery.

The routine use of propofol traditionally is restricted to anaesthetists, as in much higher doses general anaesthesia is produced with possible loss of airway patency. Currently the safety feature is predominantly that as patients become more sedated they cannot press the patient demand button and hence cannot increase the amount of propofol they are receiving. Also the device ensures that the blood and brain concentrations have equilibrated to within 10% of each other before another successful demand for propofol can be made (usually takes approximately two minutes) and it only allows a maximum calculated brain concentration of 3 micrograms/milliliter of propofol. The device also will start to decrease the calculated brain concentration of propofol if the demand button has not been pressed for six minutes.