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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E-letters: Electronic letters published:
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Does the results lack validity? I think no (response to Hocking et al)
- Carlos L. Errando (31 August 2008)
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Results may lack validity
- Graham Hocking, Brien Hennessy, William Weightman, Neville M Gibbs (27 August 2008)
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Response to 'Awareness with recall (AWR)- Too light an anaesthesia?'
- Carlos L Errando (31 July 2008)
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Awareness with recall - Too light an anaesthesia?
- Reshma P Ambulkar, Pallavi Kulkarni, Vijaya Patil (31 July 2008)
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Response to Dr. Nielsen regarding 'awareness during anaesthesia'
- Carlos L. Errando (20 July 2008)
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Anaesthetists be'ware... and alarmed
- James Nielsen (15 July 2008)
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Carlos L. Errando Consorcio Hospital General Universitario de Valencia. Valencia. Spain
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I wish to respond to the kind e-letter by Hocking et al[1], regarding our article on awareness with recall (AWR) during general anaesthesia [2].The authors outline methodological problems in our work. I should agree in part, and these are discused in the Discussion part of the work. In addition space constraints in this type of articles (dense articles) preclude the inclusion of some kind of information that can introduce apparent biases that does not exist. Regarding the years of the patients recruitment, and the number of patients involved, we describe in the Methods section the way we do this. To extend the explanation, we blindly recruited patients in the PACU, among 4-8 per day, only the days a participating anaesthetist was free of work. Moreover our PACU was closed by shortness of staff from 1.5 years in between of the time of the work was done. This way the patients were consecutively recruited, but not all patients anaesthetized during these years were entered in the database (20 000 patients per year were under anaesthesia in our hospital). No other previous consideration was taken into account to introduce patients under general anaesthesia. Therefore, as this was previously designed in the Methods we not consider this 'sampling', neither 'sampling bias' was considered possible. Of course the participation of a member of Aspect MS was declared and discussed with the Editors and Reviewers of the manuscript at the start of the submission. At the time the study was performed, BIS was not available to us (and unknown for most of the participating anaesthetists). Dr Sigl participation was in the postretrieval analysis of the data, contribution in the explanation of the findings related with this, and participation in the 'discussion' related with these aspects. No influence in the anaesthetic techniques, neither other that could have influenced AWR is warranted. In fact, the anaesthetist in charge was free of chosing premedication, anaesthetic technique, drugs or doses (see Methods section). The variety of anaesthetic techniques (some of these out of time and more prone to AWR, please read a previous e-letter)can be explained, in part, by the different anaesthesia training of the doctors, and because at that time we had an non-homogeneous way of work at our hopsital. I congratulate the authors by their low incidence of AWR, but, in my opinion, the way (and the time-times)the patients were interviewed together with the definition of AWR are both important. Comparison with the paper by Hennessy et al [3] is not possible because it is an Abstract and no complete information is available from these. Finally, as stated in the Discussion, pag 182 [2] the true figures of AWR quoted in the large (recent) studies [4-8] should be corrected -increased- by a factor of 2-3 provided the definition of AWR was that of ours, or if 'possible' awareness cases had been included. This way, the actual incidence can be in the range we obtained! [1]Hocking G, Hennesy B, Weightman W, Gibbs NM. Results may lack validity. e-letter. Br J Anaesth 2008 [2]Errando CL, et al. Awareness with recall during general anaesthesia: a prospective observational evaluation of 4001 patients. Br J Anaesth 2008; 101: 178-85. [3]Hennesy B, et al. Quality of recovery from anaesthesia: patient satisfaction survey. Anaesth Int Care 2003; 31:695-6. [4]Ranta SOV, et al. Awareness with recall during general anaesthesia: incidence and risk factors. Anesth Analg 1998; 86: 1084-9. [5]Sandin RH, et al. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355: 707-11. [7]Sebel P, et al. The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg 2004; 99: 833-9. [8]Myles PS, et al. Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial. Lancet 2004; 363: 1757-63. Conflict of Interest:None declared |
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Graham Hocking Sir Charles Gairdner Hospital, Perth, Western Australia 6009, Brien Hennessy, William Weightman, Neville M Gibbs
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We were interested to read the paper by Errando et al describing their experience of awareness with recall.[1] While the figure of 1% is undoubtedly concerning, there are multiple methodological problems with their paper, which may influence the results, and limit any conclusions to be drawn from it. We note the audit commenced in 1995 but was not completed until 2001 after recruiting only 4001 patients. Does this reflect that the population was merely a sample and therefore subject to potential sampling bias. Can the authors explain the role that ASPECT Medical Systems had in this project? Was the project actually studying the use of BIS guided anaesthesia, which may have affected the way anaesthesia was delivered over this period? We note the anaesthetic techniques described in their paper contained some with a high likelihood of awareness. As such, the results may lack external validity because their findings may be non-representative. There are also discrepancies in totals within their tabulated data, which have not been adequately explained. We performed an almost identical prospective audit in an Australian tertiary referral hospital in 2001 [2] but found a much lower incidence of awareness. Our figures were in keeping with the established literature discussed in a recent editorial in this journal. [3] A research nurse interviewed every consecutive surgical patient operated on in our institution during a full 12- month period. Data were collected on 5371 patients of whom 4899 received general anaesthesia. Using the same definition as Errando et al, [1] we had two cases of AWR-yes making our incidence of intra-operative awareness 0.04% (95% Confidence Interval 0 – 0.1%). Both cases occurred during balanced general anaesthesia with volatile agents. Since we interviewed consecutive patients in a full 12-month period, our incidence of 0.04% is a true rate of awareness in our institution. The techniques used in our hospital for general anaesthesia during the audit period were balanced anaesthesia (87%) and TIVA (13%). No anaesthetist was using solely O2/N2O for maintenance. Both of these audits were performed during a similar time period over 7 years ago. We can only speculate why the incidences are so different. We suggest the validity of their results be considered in the light of these points. References: 1. Errando CL et al. Awareness with recall during general anaesthesia: a prospective observational evaluation of 4001 patients. Br J Anaesth 2008; 101(2): 178-85 2. Hennessy B, Gibbs N, Long K. Quality of Recovery from anaesthesia: Patient satisfaction survey. Anaesth Int Care 2003; 31: 695-6 3. Sneyd JR, Matthews DM. Memory and awareness during anaesthesia. Br J Anaesth 2008; 100(6): 742-4. Conflict of Interest:None declared |
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Carlos L Errando, Staff anaesthetists Consorcio Hospital General Universitario de Valencia. Valencia. Spain
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Thank you Prof. Ambulkar for your interest in our work. I have previously responded (response to e-letter by Dr Nielsen) to one of the points adressed in your letter. The incidence quoted in the large articles on AWR was, in my opinion, lower than actually was it. The figures published excluded clear awareness cases. Please see the discussion with Dr Nielsen. On the other hand I strongly agree with Prof. Ambulkar in their other statements. The study was prospective and observational. We did not try to control for the anaesthetic conduction of the procedures, and did not indicate to the anaestehists in charge the drugs or doses to be administered. So our numbers of AWR in obstetric anaesthesia and O2-N2O 'technique' of maintenance respond to older and conservative 'theories' of adverse events in this kind of patients. The cases of AWR cumulates (relatively) in a few anaesthetists (data not showed in the article because of space constraints) that are still using such an anaesthetic procedures. If we were requested, we inform at that time these anaesthetists (and all participating colleagues) of the number and characteristics of the cases they have. Since the work was done, we have not detectec AWR cases in obstetrics (most of anaesthetics were now regional). However some cases are still appearing during general anaesthesia, and to our knowledge only 2 anaesthetists (out of more than 50) continued using O2-N2O anaesthesia in some cases. Of course, we -the authors- completely disagree of this very light anaesthetic procedure. Conflict of Interest:None declared |
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Reshma P Ambulkar, Assistant Professor of Anaesthesia Tata Memorial Centre, Mumbai, India, Pallavi Kulkarni, Vijaya Patil
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We read with great interest the article by Erlando & colleagues about awareness with recall during general anaesthesia. It was interesting to note the higher incidence of awareness noted in this study than previously recorded. In previous studies, the incidence of awareness varied from 0.1 to 0.2% in the general population to 0.4% in obstetric and 1% in cardiac surgery 1,3-5. In this study the incidence of awareness was 0.8 – 1% if the high risk patients were excluded. It is alarming to note a 5% incidence of awareness in the MA (mixed anaesthesia group- O2 & N20) group. Authors do acknowledge the varied anaesthetic practices in their hospital. Detailed data available showed 5 cases in the MA group who had awareness. Out of these 3 were emergency caesarean sections but 2 were elective surgeries (middle ear surgery & cauda equina tumour excision). In this group only O2 & N2O were used to maintain anaesthesia , though it has been proven that only O2+ N2O are not adequate for maintaining anaesthesia6. Would it then be justified to use only O2+N2O for maintenance of anaesthesia in such major surgeries? Awareness not only has immediate sequelae but also long term effects leading to post traumatic stress disorder (PTSD). Studies have shown that patients get panic attacks, nightmares even as long as 2 yrs after surgery2. We should take this seriously and strive to minimize such episodes as failure to achieve adequate depth of anaesthesia is the primary cause of awareness. REFERENCES 1. Learning and memory during general anaesthesia. An update. Anaesthesiology 1997; 87, 387-410. 2. Victims of awareness. Acta Anaesthesiol Scand 2002;46, 229-231 3. Awareness under TIVA. Anaesthesia and intensive care. 2002;30,816 4. The B-Aware randomized controlled trial. Lancet 2004; 363, 1757- 1763. 5. Awareness with recall during general anaesthesia. Anaesthesia Analgesia 1998; 86, 1084-1089. 6. Nitrous oxide. Continuing education in anaesthesia, critical care and pain. 2005; 5, 145-148. Conflict of Interest:None declared |
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Carlos L. Errando Servicio de Anestesiología. Consorcio Hospital General Universitario de Valencia. Valencia. Spain
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Thank you very much for your comments. Although our 'crude' incidence of awareness with recall (AWR) during general anaesthesia is definitely high (1%), we prefer to take into account the 'real' incidence of 0,6% in elective procedures. Due to space constraints, our discussion needed to be considerably shortened, so we cannot extensively discuss on this part of our study. However, the 1% figure is not so different of other work published as the definition of AWR can significantly modify the true incidence. As in other aspects of anaesthetic procedures, the patient perception should prevail. An important lesson learned from our work is, as Dr Nielsen notes, that we lose important information and feed-back from our patients. The availability of a recovery room (RR) offers a possibility to catch some of the cases, but this is not always possible. Another important question is whether patients should be informed about AWR in the preoperative visit. If this is done, maybe this would be the time when we should remind the patient or their relatives that if AWR occurs, they might inform his/her anaesthetist after the procedure. In this way, the possible preventive action (on psychological aftereffects, including post-traumatic stress disorder) of the pre-operative interview could work. Conflict of Interest:None declared |
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James Nielsen, Consultant Anaesthetist Concord & Bankstown Hospitals Sydney Australia
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Congratulations to Errando et al on their excellent work surveying the problem of awareness under anaesthesia. Their finding of so high an incidence (1%) in a cohort from which some high-risk patients had been excluded is sobering, especially given the exclusion of cases in which a neuromuscular blocker had been administered in error before induction. One particular strength of the survey is their definition of awareness based on the patient's view. It is too glib to dismiss patient reports as being confused or simply wrong - disproving the patient's account is a Pyrrhic victory when they remain certain of being aware 'under' your anaesthetic! Finally, the fact that nearly 75% of 'aware patients' had not discussed the issue with the responsible anaesthetist highlights our own susceptibility not to be aware of the scope of the problem. Conflict of Interest:None declared |
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