MRI sedation

increases the apnea rate. Time has moved on and our experience of this technique amounts to 26 infants (wt range 1⁄4 2.8–6.5 kg). We now accept that sedation can be induced with sevoflurane in the majority of cases, but is not reliable enough to justify the time and patience. Instead, our current practice is to induce anesthesia by facemask and conventional breathing system. Within a minute, they are asleep enough to tolerate nasal tubing and will remain asleep provided they are not stimulated. This is not sedation but could be described as ‘minimal anesthesia’ as distinct from ‘conventional anesthesia’. We offer the following definitions. Anesthesia: An unrousable ‘sleep-like’ state induced by drugs in which appreciable depression of vital reflexes is common. • Conventional anesthesia: Intervention is often necessary to support the airway, breathing and circulation. • Minimal anesthesia: ‘Anesthetic’ doses are used to induce an unrousable sleep lasting a few minutes. Thereafter the doses used are so low or ‘sub-anesthetic’ that although the individual remains asleep, • they may be rousable • appreciable effects upon vital reflexes are unlikely, and recovery is rapid. Recently, one of our infants (2.8 kg, and born at 26 weeks gestation) became almost apneic within 30 s of breathing 2% sevoflurane and this case emphasises that anesthetists must manage the technique. One may take the view that all preterm infants should have a tracheal tube and be mechanically ventilated. We do not presume to promote one method over another but we believe that a tracheal tube method is not always without difficulty and may be unnecessary. Michael R. J . Sury Helen Harker Mark L. Thomas Department of Anaesthesia, Great Ormond Street Hospital for Children NHS Trust, London, UK (email: surym@gosh.nhs.uk)