The effect of intravenous dexmedetomidine premedication on the dose requirement of propofol to induce loss of consciousness in patients receiving alfentanil.

Dexmedetomidine reduces the dose requirements for opioids and anaesthetic agents. We conducted a single-centre, open-label, noncomparative phase II study of the effect of intravenous dexmedetomidine on the dose requirement of propofol to induce loss of consciousness in 49 ASA I and II patients. The initial dexmedetomidine infusion scheme was reduced twice because of adverse events. Forty patients who received the final infusion scheme were randomly allocated to receive one of five stepped propofol infusions; loss of consciousness was assessed after 21 min. The ED50 for the final infusion rate of propofol to suppress consciousness was 3.45 mg x kg(-1) x h(-1) (95% CL 2.7-4.2): ED95 was 6.68 mg x kg(-1) x h(-1) (95% CL 5.1-19.1), EC50 was 1.69 microg x ml(-1) (95% CL 0.95-2.5) and EC95 was 5.7 microg x ml(-1) (95% CL 3.2 to > 10). Our final dose of dexmedetomidine of 0.63 microg x kg(-1) caused a reduction in the overall concentration and dose of propofol required to produce loss of consciousness, but no significant shift in the dose-response curve compared with other studies.

Patient-controlled sedation during transvaginal oocyte retrieval: an assessment of patient acceptance of patient-controlled sedation using a mixture of propofol and alfentanil.

Patient-controlled sedation (PCS) has been used during many different surgical procedures, both alone and as an adjunct to local or regional anaesthesia. Sedation with an admixture of propofol and alfentanil during transvaginal oocyte retrieval has been used successfully in this unit and this study was performed to assess the degree of patient acceptance of patient-controlled sedation, as other studies have indicated that self-administration of sedation may confer additional benefits on the patient, unrelated to the choice of sedation agent. An admixture of 50 mL propofol 1% with alfentanil 2 mg was loaded into a Graseby 3300 patient-controlled analgesia pump and administered as increments of 0.3 mL with a zero lock-out interval. This method of sedation provided safe and highly satisfactory sedation for this group of patients with 55 of 56 patients indicating that they would opt for this type of sedation again. There was a very low incidence of over-sedation, and this sedation method is likely to produce a relaxed and co-operative patient for a wide variety of surgical procedures.