If you wish to respond to a paper or other item already published in the BJA, please go to the abstract/full text version of that item and click on the link "E-Letters: Submit a response to the article".
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Further results of sedation for MRI scanning of children
- Oliver R Dearlove, James P Corcoran (4 January 2007)
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Magnetic Resonance Imaging and sedation of children
- Antony STEPHEN LAURENCE (15 December 2006)
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Correspondance
- Pooja Ajit Warty (4 October 2006)
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Dr Sury's response to the points raised by Dr Allen.
- Mike Sury (11 September 2006)
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Paediatric Magnetic Resonance Imaging Under Sedation
- Jonathan G Allen (22 August 2006)
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Melatonin does not override natural alerting mechanisms...
- James M. Howard (21 June 2006)
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Oliver R Dearlove, Consultant Anaesthetist Royal Manchester Children's Hospital, James P Corcoran
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To the Editor of the BJA – 27 Decmber 2006 Dear Sir, We were interested to read the correspondence between Allen and Sury on paediatric sedation in December’s issue of the BJA (1) having reported (2) a series in 1999. Changes in our sedation regime(3) were introduced in 2000, we have since tracked our results for sedation to facilitate MRI scanning in children. In the last five years 2002 to 2006, we have performed 4165 sedations and 478 general anaesthetics for MRI scan, (the general anaesthesia group being a mixture of those who failed sedation and those referred for general anaesthesia directly). Our sedation technique can be summed up as: oral chloral hydrate 100mg/kg to a maximum 2g, with or without rectal paraldehyde 0.3 ml/kg for children weighing < 20kg and oral quinalbarbitone (secobarbital) 10mg/kg – to a maximum 200mg for those weighing >20 kg.(4) We have had five critical incidents compared to Sury’s nil and this may reflect a different population under going sedation for MRI in the North West. Most of these were airway-led as Cote’s original paper (5) predicted. This means that the critical incidents were therefore if not avoidable, then treatable by standard means. Readers may judge if outcomes were adverse. Case A was suffering up to five convulsions a day and convulsed one hour before scan. The scan was cancelled, however nowadays we would go ahead and scan without sedation during the post convulsion period. Case B was a child with mucopolysaccharidosis who was sedated and compromised his airway. His deep sleep was associated with an oxygen requirement. The sedation lasted 90 mins and the child woke up. The scan was not carried out. The child was anaesthetised for a scan four weeks later uneventfully. Case C sedated for scan to investigate stridor, became oversedated and lost his airway. He was anaesthetised without problem a week or so later. The pre-operative visit had revealed no stridor, no intercostals indrawing and nothing to suggest a compromised airway. Anaesthesia later was uneventful. Case D had an MRI scan which showed an empyema. The child’s condition was such that the child went immediately to theatre for decortication. Case E was oxygen dependent before his sedation, maintained adequate saturations on oxygen during the sedation and awoke at a reasonable time later. We did not feel that the child should be discharged on the same day and was kept in overnight. During this time, we had one critical incident in the general anaesthetic group. This was a failure to anaesthetise. Case G was a seven year old child who had mucopolysccaridoosis type 1 and a known complication tricuspid incompetence. Induction of anaesthesia was effected by nitrous oxide, oxygen and sevoflurane. The child started coughing and within two minutes pink sputum poured out of the laryngeal mask. Chest X ray confirmed pulmonary oedema. Lasix 1 mg/kg, and gentle CPAP was carried out and the oedema resolved over one hour. The laryngeal mask was removed and the child admitted overnight for observation. The scan was cancelled. Discussion. Our series is a large one to be reported. Critical incidents are expected in the best run series, Outcome depends on how they are handled. Dr Allen’s and Sury’s correspondence (1) sum up the current tensions in providing a service for sedation of children. Various points arise from it. The demand for sedation in a hospital is huge and there is little interest in anaesthetists who like to anaesthetise rather than sedate or supervise. In order to show safety, it is necessary to perform very large numbers of procedures and audit them as we have done. If ‘safe’ means zero critical incidents then there will be a pressure to under report. ‘Safe’ we think is a situation where` random events are treated by trained personnel in a timely fashion and without an adverse outcome. Dr Sury refers to the use of melatonin, where he further comments (6) ‘in this dose and clinical conditions melatonin did not contribute to sedation of children. The failure rate was 30% in Wassmer’s series (7) and we would rate this as so high as to make it useless in this context. Our failure rate was 478 in 4165 which is 11 %. Sury also says ‘I think it is highly unlikely that there are good data to support the widely held view by anaesthetists that anaesthesia is safer than sedation in children for MRI in children’. And therein lies the nub of the argument, as MRI in children tends to be a standard non painful procedure. Many sedations are performed by nurses under supervision and most anaesthetics are performed by anaesthetists. Of course, we do not know how safe sedation services in the UK are, because workers such as Sury and myself have failed, until now, to report their results. Clearly if we do a lot, we should be reporting our results, and not relying on opinion perhaps from those with less experience. Sury says that he doubts if he could anaesthetise a cohort of 5000 without there being several potentially life threatening cases of laryngospasm. But in his 1999 paper (2), he also had a sedation failure rate of 5%, and I am sure he will say that he doesn’t fail to anaesthetise 5% of his patient in a similar cohort. He does not compare like with like. Quine (8) remains the only paper on the safety of sedation admittedly in endoscopy in a much older age group and this shows a mortality in a very different group of 1 in 2500. We found that there was a group of children for whom it was safer to anaesthetise than sedate and this was the children with mucopolysaccharidosis. Nonetheless the waiting times for scan become quickly unmanageable if too many well children are referred directly for general anaesthesia. Secondly, Malik has reported a series of children who were assessed for stridor under general anaesthesia and then sedated for MRI scanning, (4) who are included in this series. A one-stop shop – guaranteeing a scan after a single visit to Hospital is possible, and general anaesthesia will figure greatly in this system. This is one that Dr Allen describes. We find that one session is suitable for around 150 scans/yr. And so if one needs a thousand scans under sedation, to do it in this fashion would require 10 sessions – or the whole week. It is difficult to scale up a service such as Dr Allen is in charge of, to ten times the volume. Other sedations schemes in use at this hospital are not included in this series, for example the results for sedation for renal biopsy were such that the majority are performed under general anaesthetic now. A sedation service has to be safe, however safety is open to interpretation and the service must also be available. Dr Allen’s series of 200, although admirable, doesn’t show this. The demand for sedation is such that if there is no anaesthetist to provide it or supervise it, the sedation will still go ahead, but provided by someone else without anaesthetic skills. Cote (5) has reported a long series of disasters showing how things can go wrong and how most critical incidents were airway led. Anaesthetists are well placed to treat those incidents which are most likely to occur during sedation, which are airway problems. Safe sedation services provide a challenge for the anaesthetist, a challenge to which we must rise. O. Dearlove FRCA J P Corcoran FRCS FDS,RCS FRCA Conflict – These results were presented by ORD in the Current Concepts in Neurology meeting on 3 Nov 2006 at the Royal College of Anaesthetists, it has to be said, exciting little interest. 1. Allen JG Sedation of Children undergoing magnetic resonance imaging BJA 2006 97 898-9 2.Sury MRJ Hatch DJ Deeley T et al Development of a nurse led sedation service for paediatric magnetic resonance imaging Lancet 1999 353 1667-71 3.Keengwe IN Hegde S Dearlove O et al Structured sedation programme for magnetic resonance imaging examination in children Anaesthesia 1999 54 1069 - 1072 4. Malik TH Bruce IA Kaushik V The role of MRI in the assessment of suspected extrinsic tracheobronchial compression due to vascular anomalies Arch Dis Child 2006 91 52-55 5.Cote CJ Notterman DA Karl HW et al Adverse Sedation Events in Pediatrics A critical Incident Analysis of Contributing Factors Pediatrics 2000 105 805-815 6.Sury M Fairweather K Effects of Melatonin on children undergoing sedation BJA 2006 97 220-5 7.Wassmer E et al, Melatonin as a sedation for diagnostic procedures MRI and EEG Dev Med Child Neurol 2001 43 136 8.Quine MA Bell GD McCloy RF et al A prospective audit of upper gastro-intestinal endoscopy in two regions in England safety, staffing, sedation methods Gut 1995 36 462-7 Conflict of Interest:as script |
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Antony STEPHEN LAURENCE, consultant anaesthetist
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Editor- I read with interest the correspondence between Drs Sury and Allen [1] following the article on Melatonin sedation for MRI [2]. I cannot claim to have looked after quite as many patients as Dr Sury, but over the 12 years of the GA service for MRI in Preston, I personally have successfully sedated well over 1000 children. I do not routinely give any initial oral medication, unless the child has severe development delay and is behavourally challenging. I prefer an intravenous route to start the sedation, using a technique of Propofol bolus followed by Propofol/alfentanil infusion, without any intervention to the airway. The child usually opens the eyes when picked up off the scanner couch as soon as the scan is finished. Indeed, I only use a GA (sevoflurane induction) on the rare occasions when IV access has failed. On no occasion have I had an airway problem with sedation. Like Dr Sury, I also would have expected a number of instances of laryngospasm and problems if all these children had been given a more formal anaesthetic. I admit we have very sick babies only on rare occasions; they are usually already being ventilated, so sedation is not appropriate. I totally support Dr Sury’s opinion that sedation in the MRI scanner should be the province of the anaesthetist if possible; we prohibited anyone but anaesthetists from administering medication in our MRI unit from the outset of the provision in Preston. The MRI scanner is also not a suitable area for unsupervised trainees, either. AS Laurence, Preston, UK Referenes; 1. JG Allen and reply by MRJ Sury. Sedation of children undergoing Magnetic Resonnce Imaging. Br J Anesth 2006; 97: 898-9. 2. Sury MRJ, Fairweather K.The effect of melatonin on sedaion of children undergoing magnetic resonace imaging. Br J Anaesth 2006; 97: 220- 5. Conflict of Interest:None declared |
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Pooja Ajit Warty, Anaesthetist
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Editor- I would like to congratulate the authors for their work on the drug melatonin as a sedative agent for children undergoing magnetic resonance imaging1. Being a naturally secreted hormone melatonin can be expected to create a state of natural sleep, free of anxiety with quick recovery of all faculties including psychomotor skills. Although this drug appears to be an alternative premedication on the horizon there are certain issues about the drug, which I would like to highlight 1) Sedation by melatonin needs a surrounding, which is conducive to stimulate sleep. Creating such an atmosphere could be difficult in a busy MRI/ day surgical suite. 2) It takes approximately 45 minutes for the sedative effect when this drug is administered orally 2, which again may be time and manpower consuming in a day surgical unit. 3) The presence of anxiety is almost universal in the pre-procedure period and may even cause patients to fail to report for the planned procedure. Although melatonin is considered to have an anxiolytic effect the same effect in children has not yet been widely researched upon. 4) Although there have been studies eliciting the sedative effect of melatonin as a premedication2 the authors of this study failed to demonstrate similar effects in children. I feel that further studies are required to assess the correlation of personality of the patients and the response to melatonin, if any. Once this is done it will permit the judicious administration of melatonin as a sedative agent. 1)Sury M, Fairweather K. The effect of melatonin on sedation of children undergoing magnetic resonance imaging. Br J Anaesthesia 2006; 97:220-5. 2)Naguib M, Samarkandi AH. The comparative dose –response effects of melatonin and midazolam for premedication of adult patients: a double blinded, placebo-controlled study. Anesth Analg 200; 91:473-9 Conflict of Interest:None declared |
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Mike Sury
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Quality, defined as how good or bad something is, is a matter of opinion. Many parents prefer sedation delivered by mouth – provided it is successful – because their children dislike both inhalational and intravenous inductions. Neither the time taken for scan readiness nor scanner utilization are quality issues for individual patients; indeed they are both measures of efficiency. Nevertheless I accept that a single visit to gain predictable anaesthesia and perfect imaging is a higher quality experience than difficult or failed sedation (not forgetting that anaesthesia inductions can also be difficult). The safety of a particular technique is largely dependent upon the practitioner. Sedation should be safe enough provided that the judgement and skills of the sedationist are satisfactory. I think that it is highly unlikely that there are good data to support the widely held view by anaesthetists that anaesthesia is safer than sedation for MRI in children. Certainly, in our experience of sedating over 6000 children for MRI, we have not had a serious airway incident whereas I doubt that I could anaesthetise a similar cohort without there being several potentially life threatening cases of laryngospasm. It is important to emphasise that our children were selected – i.e. sedated children are healthier than those selected for anaesthesia. Not withstanding all these thoughts, most hospitals will use anaesthetists for MRI if they have enough of them. Conflict of Interest:None declared |
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Jonathan G Allen, Consultant Anaesthetist Queen Elizabeth Hospital, Kings Lynn
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As a consultant anaesthetist with a regular "paediatric MRI under anaesthesia" list, I read the paper by Sury and Fairweather with great interest. I use a sevoflurane inhalation induction followed by intravenous cannulation. A laryngeal mask airway facilitates spontaneous respiration with sevoflurane and nitrous oxide. Comprehensive anaesthetic monitoring is used throughout. In my experience of over 200 cases, the advantages of this approach over sedation techniques are, I suggest: Single visit to the hospital regardless of child's "cooperation level". No necessity for awake, tearful needles. Predictably rapid time to readiness and scan time - optimal scanner utilisation. Guaranteed completion of high diagnostic quality scans with minimal movement artefact. Safety for unconscious children in a remote setting. I therefore disagree with their concluding paragraph. "Efficiency" is not the sole reason why so many units prefer general anaesthesia. I suspect "quality" is the main consideration. Conflict of Interest:None declared |
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James M. Howard, Biologist independent
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It is my hypothesis that the sleep - consciousness mechanism is controlled by melatonin and DHEA (1985). Melatonin has been demonstrated to be involved in DHEA production and vice versa. When melatonin is high, DHEA is low and sleep occurs and when DHEA is high, consciousness occurs. I suggest this mechanism evolved to produce sleep and consciousness and so sleep is easily interrupted. This may be why melatonin does not induce sleep when individuals are on alert or have ingested stimulants. Evolution selected for a mechanism that is easily disrupted when necessary for survival. Conflict of Interest:None declared |
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