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time (time to eye opening) of 810 min is more usual [2]. Secondly, given that dexmedetomidine has an onset of action of < 5 min and peak effect within 15 min [3], we are not surprised that emergence agitation was not significantly more prevalent in Bong et al.’s study, in which the drug was administered 70 min before removal of the laryngeal mask. As their results contrast with a recently published meta-analysis on the pharmacological prevention of emergence agitation in children using a2-agonists [4], do the authors think that an adequate concentration of the drug was present in participants at the time of laryngeal mask removal? Emergence agitation usually occurs within the first 30 min after anaesthesia, with the highest incidence in first 5-15 min [5, 6]. The authors, however, found a high incidence (39%) 20 min after anaesthesia, but did not mention the time of removal of any oral airway. Do they consider that this anomaly could explain why they found no difference in the prevalence of emergence agitation between propofol and dexmedetomidine? Finally, agitation was recorded only after spontaneous eye opening, but no sedation score was used to grade the degree of sedation after surgery. As sedation during emergence has been shown to affect the incidence of emergence agitation [4], how confident are the authors that their results could not be explained merely by varying levels of sedation between groups?
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Correspondence
J. K. Makkar D. Jain K. Jain A. Jafra Post Graduate Institute of Medical Education & Research, Chandigarh, India Email:
[email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthesia correspondence.com.
References 1. Bong CL, Lim E, Allen JC, et al. A comparison of single-dose dexmedetomidine or propofol on the incidence of emergence delirium in children undergoing general anaesthesia for magnetic resonance imaging. Anaesthesia 2015; 70: 393–9. 2. Sethi S, Ghai B, Ram J, Wig J. Postoperative emergence delirium in pediatric patients undergoing cataract surgery – a comparison of desflurane and sevoflurane. Pediatric Anesthesia 2013; 23: 1131–7. 3. Mecca RS. Postoperative Recovery. In: Stoelting RK, Barash PG, Cullen BF, eds. Clinical Anesthesia. Philadelphia: Lippincott Williams and Wilkins, 2006: 1379– 404. 4. Dahmani S, Stany I, Brasher C, et al. Pharmacological prevention of sevoflurane- and desflurane-related emergence agitation in children: a metaanalysis of published studies. British Journal of Anaesthesia 2010; 104: 216–23. 5. Cole JW, Murray DJ, McAllister JD, Hirshberg GE. Emergence behaviour in children: defining the incidence of excitement and agitation following anaesthesia. Pediatric Anesthesia 2002; 12: 442–7. 6. Seo IS, Seong CR, Jung G, Park S, Kim SY, Kim MM. The effect of sub-Tenon lidocaine injection on emergence agitation after general anaesthesia in paediatric strabismus surgery. European Journal of Anaesthesiology 2011; 28: 334–9. doi:10.1111/anae.13116
A reply We thank Dr Makkar and colleagues for their interest in our study [1], comparing the incidence and severity of emergence delirium in children undergoing MRI. The lack of surgical stimulation and absence of pain removes these as potentially confounding variables, allowing for a controlled investigation of emergence delirium, which may explain why our results varied from previous studies [2–4]. An oral airway was inserted after removal of the laryngeal mask with the patient deeply anaesthetised, before sevoflurane was discontinued and the child moved to an adjacent recovery area. Given the proximity of the recovery area to the MRI scanner, this transfer process typically takes 5-10 seconds. We left the child to emerge from anaesthesia undisturbed for up to 30 minutes before attempting stimulation. In practice, given the lack of surgical stimulus and disturbance, the children typically had a spontaneous emergence time of 1520 minutes. The oral airway was left in place until the child gagged or opened his/her eyes. It is conceivable that this could explain the relatively high incidence of emergence delirium 20 minutes after anaesthesia. We are aware that dexmedetomidine has a rapid onset and short duration of action. During the pilot phase of our study, we administered dexmedetomidine 0.3 lg.kg 1 at the end of anaesthesia, just before laryngeal mask removal. While this prevented emergence delirium, it was associated with an unacceptably long emergence time and prolonged stay
© 2015 The Association of Anaesthetists of Great Britain and Ireland
Correspondence
in the PACU, and so was deemed impractical for our study. Instead, we administered dexmedetomidine 0.3 lg.kg 1 after induction of anaesthesia, which has been reported previously to be effective in reducing the incidence of emergence delirium (as measured by a 4-point behaviour scale) in children undergoing lower abdominal surgery with caudal anaesthesia [5]. We found that the incidence of emergence delirium (as measured by the PAED scale) with dexmedetomidine was no different to that with placebo. Although it is quite possible that the plasma concentration of dexmedetomidine in our patients was too low to prevent emergence delirium at the time of laryngeal mask removal, we think that the lack of difference may be more related to the different scale used to measure emergence delirium. We did not measure sedation scores. Our study was designed to assess emergence delirium after MRI. No premedication was given, no surgery was done and no opioid or long-acting drugs were used that could cause prolonged sedation. Comparing different studies on emergence delirium has always been difficult owing to their heterogeneity. Different studies employ different evaluation tools for emergence delirium in varying clinical settings [6]. We are not disputing the fact that propofol and dexmedetomidine have been shown to be useful in preventing emergence delirium in various settings with varying methods, timing and dosage of administration. We can only conclude that in our randomised controlled trial, the administration of propofol
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1 mg.kg 1 at the end of sevoflurane anaesthesia for MRI in children did not make a difference to the incidence or severity of emergence delirium, as measured by the PAED scale, compared with dexmedetomidine 0.3 lg.kg 1 administered on induction of anaesthesia. C. Bong E. Lim J. Allen Y. N. Siow J. Tan KK Women’s and Children’s Hospital, Singapore Email:
[email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthe siacorrespondence.com.
References 1. Bong CL, Lim E, Allen JC, et al. A comparison of single-dose dexmedetomidine or propofol on the incidence of emergence delirium in children undergoing general anaesthesia for magnetic resonance imaging. Anaesthesia 2015; 70: 393–9. 2. Sethi S, Ghai B, Ram J, Wig J. Postoperative emergence delirium in pediatric patients undergoing cataract surgery - a comparison of desflurane and sevoflurane. Pediatric Anesthesia 2013; 23: 1131–7. 3. Guler G, Akin A, Tosun Z, Ors S, Esmaoglu A, Boyaci A. Single-dose dexmedetomidine reduces agitation and provides smooth extubation after pediatric adenotonsillectomy. Pediatric Anesthesia 2005; 15: 762–6. 4. Aouad MT, Yazbeck-Karam VG, Nasr VG, El-Khatib MF, Kanazi GE, Bleik JH. A single dose of propofol at the end of surgery for the prevention of emergence agitation in children undergoing strabismus surgery during sevoflurane anesthesia. Anesthesiology 2007; 107: 733– 8. 5. Ibacache ME, Munoz HR, Brandes V, Morales AL. Single-dose dexmedetomi-
© 2015 The Association of Anaesthetists of Great Britain and Ireland
dine reduces agitation after sevoflurane anesthesia in children. Anesthesia and Analgesia 2004; 98: 60–3. 6. Dahmani S, Stany I, Brasher C, et al. Pharmacological prevention of sevoflurane- and desflurane-related emergence agitation in children: a meta-analysis of published studies. British Journal of Anaesthesia 2010; 104: 216–23. doi:10.1111/anae.13143
Auditing safe sedation practice nationally The SWARM group should be congratulated on the recent article on sedation practice within six acute hospitals [1], which demonstrates that a national audit of sedation practice appears feasible. However, if data from the SWARM group are extrapolated to all UK hospitals, non-anaesthetists administer over two thirds of procedural sedation, which raises the question of how the accurate recording of adverse events might best be achieved. This will undoubtedly involve co-ordinated collaboration between a number of stakeholders, such as occurred in the production of the Academy of Medical Royal Colleges report Safe Sedation Practice for Healthcare Procedures: Standards and Guidance [2], but the potential improvements for patient care should not be underestimated. R. Curtis Royal Derby Hospital, Derby, UK Email:
[email protected] No external funding and no competing interests declared. Previously posted on the Anaesthesia corre885
