[1] Univ Aberdeen, Sch Med, Inst Med Sci, Aberdeen AB25, Scotland
[2] Radcliffe Infirm, Nuffield Dept Anaesthet, Oxford OX2 6HE, England
[3] Royal Brompton Hosp, Crit Care Unit, London SW3 6LY, England
[4] Univ Sheffield, Dept Pharmacol, Sheffield, S Yorkshire, England
[5] Papworth Hosp, Dept Cardiothorac Anaesthesia, Cambridge CB3 8RE, England
[6] Hop Lariboisiere, Dept Anesthesiol Reanimat Smur, Paris 10, France
[7] Univ Missouri, Columbia, MO 65212 USA