Sevoflurane sedation in infants undergoing MRI: A preliminary report
Department of Anaesthesia, Great Ormond Street Hospital for Children NHS Trust, London WC1N 3JH, UK. Pediatric Anesthesia
(Impact Factor: 1.85).
02/2005; 15(1):16-22. DOI: 10.1111/j.1460-9592.2005.01456.x
Stillness during natural sleep after feeding may not be sufficient for successful magnetic resonance imaging (MRI) in small infants less than 5 kg. Sedation, using an oral agent, is often successful although the timing and depth of sedation is variable. In contrast anesthesia is always effective but is invasive and is associated with postanesthesia apnea and bradycardia in preterm and ex-preterm infants. We are developing an alternative technique involving insufflation of sevoflurane and present our initial experience.
Infants presenting for MRI were sedated by nasal insufflation of sevoflurane carried by 2 l.min(-1) oxygen. We recorded the sevoflurane administered, timing of sedation and scanning, conscious level, oxygen saturations, and recovery profile.
Of the 13 infants studied (median postconceptional age: 46 weeks, range: 40-70 weeks; median weight: 4.4 kg, range: 3.3-6.5 kg), sevoflurane caused sleep and enabled successful imaging in 12. Six infants fell asleep within 10 min and the median maximum sevoflurane vaporizer setting for successful sedation was 4% (range: 4-8%). Before scanning, 10 infants remained easily roused by touch and two became unresponsive; one desaturated to 85% and required repositioning of the head to maintain a clear airway. Immediately after scanning all infants were easily roused by touch.
Sedation by insufflation of sevoflurane in small infants is a simple and practical alternative technique for painless imaging such as MRI; further experience is necessary to determine its limitations.
Available from: ece.rutgers.edu
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ABSTRACT: Rowe and Stone dispose of descriptive terminologies for retinal units as 'essentialist' and argue for a 'neutral' multifactorial system redefined from previous W, X, Y nomenclatures. It is argued here that descriptive terminology need not be either essentialist or undesirable and that the W, X, Y terminology is too confused with false associations to be satisfactory. The synthetic power of the W, X, Y nomenclature was lost with the discovery of concentric W cell receptive fields, the projection of the W cells to the LGN and the suggestion of overlap between X and W conduction velocity groups. It was made methodologically unsound by its employment for the naming of Nissl stained soma classes before the identity of individual somas with the physiological entities can be demonstrated. Although now redefined, the identity of symbols in the several vintages of the W, X, Y system leads to inevitable confusion. The current tripartite division of a multidimensional quality space without cluster analysis is not neutral because it emphasises conduction velocity but represses the diversity of W receptive fields. The concise, apt and memorable descriptive receptive field terminologies are more desirable in that they are operationally based and approximate the unit's transfer function – the parameter most significant to the central nervous system in its information processing task; thus they are more suited for cross species comparison because of a probably bountiful source of functional hypotheses. The lack of taxonomic neutrality in the W, X, Y system has recently been emphasised by its failure to adequately classify rabbit retinal receptive field categories.
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ABSTRACT: The ability of a child to remain sufficiently immobile for painless imaging depends upon their behaviour and the imaging itself. Anaesthesia allows imaging to be optimised but it is expensive, scarce and inappropriate for many situations. Fortunately, sedation and behavioural techniques are sufficiently successful for the majority of scanning, and success rates are high provided that suitable children are selected. Sedation, however, administered by non-anaesthetists, may have catastrophic complications such as airway obstruction. Current UK recommendations demand that any sedation technique has a 'wide margin of safety', but in addition to this, safety is dependent on trained, skillful and experienced staff. Magnetic resonance imaging frightens many children and special planning is necessary for sedation and anaesthesia. When planning an imaging service for children, all the management techniques should be considered in order to achieve maximum efficiency, quality and safety.
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