Conscious sedation

Abstract

CONSCIOUS SEDATION Sir, the paper by Drs Mikhael, Wray and Robb which describes a technique of intravenous conscious sedation using a combination of midazolam, alfentanil and ketamine raises some issues which we feel require further explanation. First, at the time the study was carried out, all published Standards and Guide­ lines advised that intravenous conscious sedation in children ought to be a rare event and recommended that it should be used only after all other options had been exhausted and then, preferably in a hospital setting. Second, the use of any of these drugs for conscious seda­ tion in children was (the position has since changed for midazolam) outwith the product licence and we know of no peer reviewed data regarding the phar­ macological consequences of their use in combination. Given these two points, we must assume that the information pre­ sented in the paper was gathered using a research protocol. If so, was ethical approval sought, and from whom? Did the parents give fully informed con­ sent both for the research and for the use of the unapproved drugs? Were they told about the unpredictable risk of deep sedation (deemed to be equiva­ lent to general anaesthesia by the GDC and therefore unacceptable outside a hospital setting)? Third, Dr Mikhael presented a paper relating to 6,000 children sedated as described above to The Dental Sedation Teachers Group (DSTG) in 2005. Were these the same patients as in the 2007 paper and if so, what part, if any, did Drs Wray and Robb play in the earlier single author study? Our fourth concern relates to the way in which the drugs were administered. Conscious sedation is a state, not a defined entity, and varies from patient to patient. Indeed, the state may vary in the same patient on different treat­ ment occasions. Thus it is not possible to define a specific dose of an intravenous sedative drug. Therefore, all standards and guidelines advocate titration of a single drug to be certain that the state of conscious sedation does not progress to deep sedation or general anaesthesia. However the studies described here relate to three drugs, with a wide range of dosage. When such a mixture of drugs is used how does one determine dosage? In what order and to what end point are the individual drugs given? In addition, there is some confusion in the article by Dr Mikhael over titration versus bolus intravenous injections, and potency ver­ sus length of action of the drugs used. Onset time of the drugs is not mentioned. Although having eschewed titration as ‘theoretically illogical’, because of this confusion the earlier article concludes that ‘titration of midazolam alone or the entire mixture gives an added safety margin against the tendency towards deep sedation’. The first requirement of any tech­ nique of conscious sedation is that there should be a sufficient margin of safety. Although the incidence of both was less that 1%, Mikhael, Wray and Robb reported that there were occasions when verbal responsiveness was lost or oxygen saturation decreased below acceptable levels. Those episodes may have had no consequences, but suggest to us that the technique does not have a sufficient margin of safety for the gen­ eral dental practice setting. We are aware of at least four cases where a multi-drug intravenous technique (given outside a hospital setting) has been associated with significant patient morbidity and view the use of such methods in out­ patient dentistry with some concern. Central nervous system depressants act synergistically, a fact which the authors acknowledge, in regard to increased effi ­ cacy at low doses. This will also reduce the incidence of unwanted effects spe­ cific to each agent, but the potential for cardio-respiratory depression is com­ mon to each, and these effects will also be increased synergistically. Our comments do not mean that we deny that some patients are resistant to the traditional techniques of seda­ tion or that we would wish to obstruct the evaluation of new methods. How­ ever, these must be evaluated in properly designed, formally established research protocols. Crucially, the technique must be defined exactly so that others can try and assess it. The simple statement of the dose range for three very different drugs is insufficient in this regard. L. Strunin, London, T. Wildsmith, Dundee

DOI: 10.1038/sj.bdj.2008.415

Cite this paper

@article{Strunin2008ConsciousS, title={Conscious sedation}, author={Leo Strunin and Thomas F Wildsmith}, journal={BDJ}, year={2008}, volume={204}, pages={541-542} }