BJA
Correspondence
difficulties with i-gel ventilation and also difficulties with facemask ventilation.1 Therefore, unfortunately, when both standard laryngoscopy and face-mask ventilation fail (cannot intubate, cannot ventilate), there is an increased risk for difficulties with supraglottic airway device insertion and ventilation as well.
Declaration of interest None declared. L. G. Theiler* R. Greif Bern, Switzerland * E-mail: [email protected] 1 Theiler L, Gutzmann M, Kleine-Brueggeney M, Urwyler N, Kaempfen B, Greif R. i-gelTM supraglottic airway in clinical practice: a prospective observational multicentre study. Br J Anaesth 2012; 109: 990– 5
doi:10.1093/bja/aet565
In science, all facts, no matter how trivial or banal, enjoy democratic equality
Declaration of interest None declared. M. Sramek* Ch. Keijzer Amsterdam, The Netherlands * E-mail: [email protected] 1 Theiler L, Gutzmann M, Kleine-Brueggeney M, Urwyler N, Kaempfen B, Greif R. i-gelTM supraglottic airway in clinical practice: a prospective observational multicentre study. Br J Anaesth 2012; 109: 990– 5 2 Keijzer Ch, Buitelaar D, Efthymiou KM, et al. A comparison of postoperative throat and neck complaints after the use of the i-gel and La Premiere disposable laryngeal Mask: a double blinded, randomized, controlled trial. Anesth Analg 2009; 109: 1097– 104
doi:10.1093/bja/aet564
Supraglottic airway devices as intubation aids Reply from the authors Editor—We read with interest the letter by Dr Sramek and Dr Keijzer. We are thankful for this valuable contribution. Dr Sramek correctly points out that the i-gel (and many other supraglottic airway devices) provide an excellent back-up device to fibreoptically intubate a patient with a difficult airway. It is especially noteworthy that an awake technique should remain the gold standard in expected difficult airway management. As we have shown in our study cited by Dr Sramek, there is an overlap of risk factors predicting
Editor—In the alluring and rapidly expanding field of developmental anaesthetic neurotoxicity, facts have been accumulating at a tremendous rate. The overview of recent work in this area provided by Sanders and colleagues,1 covering both laboratory and clinical studies, is therefore a welcome addition to the literature. However, rather than providing a critical and unbiased evaluation of the all-important hypothesis—that a clinically relevant neurotoxic effect of anaesthetics exists—like most other investigators in the field, the authors approach the topic with an implicit assumption that any demonstrable effect must be meaningful. Indeed, already in the introduction, the burden of proof is squarely placed on those questioning the existence of the condition under study when the authors write, ‘these accumulating clinical data cannot exclude a clinically important effect . . . on cognition in later life’. In science, proof of non-existence of anything is notoriously difficult, if not outright impossible. Therefore, one must consider whether current knowledge justifies treating the clinical relevance of anaesthetic neurotoxicity as an established paradigm (and hence the demand to demonstrate its non-existence) as opposed to a hypothesis still awaiting proof. With respect to rodent data, which constitute the bulk of available information, it is worth pointing out that most experiments were conducted using inbred strains. Inbreeding, by reducing genetic variability, may create both susceptibility to injury and limit compensatory potential, adding to the problems of extrapolating from rodent data to the human condition. Therefore, the authors appropriately highlight the importance of studies in animals other than rodents. On this background, the lenience with which the methodological deficiencies of the piglet studies are downplayed is striking: the lack
387
Downloaded from http://bja.oxfordjournals.org/ at Georgetown University on July 11, 2015
The high fibreoptic score using the i-gel was especially noteworthy. In only 2% of the cases, it was not possible to see the vocal cords.2 In our hospital, we have a considerable number of difficult airways due to malignancies in the larynx/ pharynx. Although awake fibreoptic intubation remains the gold standard in many difficult airway patients, we increasingly use the i-gel for ventilation in patients with an interdental gap of ≥3 cm. Once the patient’s lungs are ventilated, we intubate the trachea using a flexible scope through the i-gel. When lubricated properly, an oral tracheal tube (size 7.0) can be effortlessly pushed along the flexible scope through the i-gel in between the vocal cords. Correct positioning is easily achievable using the scope. If desired, the i-gel can be removed while the tracheal tube is held in the correct place using surgical forceps. This method appears to be so successful that it is increasingly being used in our department in the case of an unexpected difficult airway. The main requirements for this technique are the use of an i-gel 4 (or 5) and an interdental gap of at least 3 cm. By using the i-gel for ventilation before tracheal intubation, one limits the number of manipulations in the larynx, thus reducing the development of swelling, hypersalivation, and potential bleeding.
BJA
Declaration of interest None declared.
388
M. Perouansky Wisconsin, USA E-mail: [email protected] 1 Sanders RD, Hassell J, Davidson AJ, Robertson NJ, Ma D. Impact of anaesthetics and surgery on neurodevelopment: an update. Br J Anaesth 2013; 110 (Suppl. 1): i53–72 2 Schubert H, Eiselt M, Walter B, Fritz H, Brodhun M, Bauer R. Isoflurane/ nitrous oxide anesthesia and stress-induced procedures enhance neuroapoptosis in intrauterine growth-restricted piglets. Intensive Care Med 2012; 38: 1205– 14 3 Rizzi S, Ori C, Jevtovic-Todorovic V. Timing versus duration: determinants of anesthesia-induced developmental apoptosis in the young mammalian brain. Ann N Y Acad Sci 2010; 1199: 43– 51 4 Bartels M, Althoff RR, Boomsma DI. Anesthesia and cognitive performance in children: no evidence for a causal relationship. Twin Res Hum Genet 2009; 12: 246–53 5 Colgrove J, Bayer R. Could it happen here? Vaccine risk controversies and the specter of derailment. Health Aff (Millwood) 2005; 24: 729–39 6 Nicoll A, Elliman D, Ross E. MMR vaccination and autism 1998. Br Med J 1998; 316: 715– 6
doi:10.1093/bja/aet566
Use of capnography may cause airway complications in intensive care Editor—It is widely acknowledged that the incidence of serious adverse airway events is higher in the intensive care and emergency department environments. NAP4 revealed that failure to use capnography has been implicated in poor outcomes after adverse airway events on intensive care units (ICUs).1 The use of capnography in UK ICUs is now becoming increasingly common,2 – 9 and follows a number of recommendations both nationally and internationally.10 – 12 We wish to highlight one potential safety implication of the introduction of this unfamiliar equipment to the ICU environment, and report a case where the use of capnography was contributory to the development of an airway emergency. A male patient was admitted to our neuro-intensive care unit. During his ITU stay, continuous waveform capnography was used as per departmental policy, and a tracheostomy placed to facilitate weaning from the ventilator. After the change of position of the patient, the end-tidal CO2 (E′CO2 ) line became entangled on the bedside, and despite the staff member taking care to watch the breathing circuit, the tracheostomy was partially displaced due to traction from the capnography line. The incident was managed as per national guidelines;13 however, the patient still sustained surgical emphysema and bilateral tension pneumothoraces necessitating immediate decompression and intercostal chest drains. The patient recovered from this episode. Upon further investigation of this event, we noted that the capnography line ran separately to the breathing circuit and was located on the monitoring system, rather than the
Downloaded from http://bja.oxfordjournals.org/ at Georgetown University on July 11, 2015
of control in one of them2 (an incomprehensible deficiency for a laboratory study) and the fact that only a single animal per drug condition was used in the other3 are buried rather than highlighted (inclusion of a study with a n¼1 per condition into a ‘systematic’ review is, per se, debatable). In contrast, the gloves are off when it comes to methodological criticisms of clinical studies, especially when the study casts doubt on the existence of a relevant toxic effect: their outcome measures (e.g. developmental milestones, learning achievement, academic performance) are dismissed on the grounds that they are too ‘coarse’, disregarding the possibility that these outcomes might in fact be those that matter in real life—as opposed to achievements on arbitrary behavioural scales for rodents or monkeys. Another ground for summarily dismissing inconvenient clinical studies is ‘small sample size’. For example, doubt is cast on the relevance of the study by Bartels and colleagues4 on the grounds that it included ‘only’ 1143 pairs of monozygotic twins! Small sample size is a valid concern, but the criticism seems to be arbitrary, since the total number of piglets was 42 (39+3 for the two studies cited), and the total number of monkeys enrolled in all seven studies was 91—and of these, only 12 (neither sex- nor otherwise matched) underwent behavioural assessment. In contrast, the unique strength of Bartel and colleagues’ work, that is, comparison of clinically relevant cognitive outcomes between ‘perfectly matched’ (monozygotic twins) populations, is largely ignored. Considering the enormity of the problem that good matching of controls represents, especially for comparing neurocognitive outcomes, this neglect of a unique strength of this study is striking. One might ask whether this sceptical criticism is justified at all—is not it in the public’s interest of ‘safety’ to assume the potential for toxicity? Should not everybody be alert, watchful, and critically cautious? As Sanders and colleagues note, surgery in children is rarely purely elective. However, it is also important to recognize that clinically relevant science is not insulated in an ivory tower of academic objectivity, where hypotheses are vetted thoroughly and dispassionately before carefully crafted experts’ conclusions, objective and reflecting the pinnacle of wisdom, are released to an obediently waiting, disciplined, and responsive public. Experience, especially in England with the pertussis and MMR vaccine scares of decades past, teaches us how scientific (mis)information can lead to irrational behaviour in wide swaths of the population.5 The excess morbidity from the pertussis vaccine panic in Britain has been estimated at 300 000 with 70 deaths.6 If irrationality of behaviour is proportional to the degree of stress, the potential damage from the ‘anaesthesia threat’ in necessary surgeries delayed or avoided is enormous. In summary, the authors have provided a very useful collection of pertinent facts from the existing literature in this field. The reader should be aware of the potential bias in the interpretation of the data.
Correspondence
Correspondence
difficulties with i-gel ventilation and also difficulties with facemask ventilation.1 Therefore, unfortunately, when both standard laryngoscopy and face-mask ventilation fail (cannot intubate, cannot ventilate), there is an increased risk for difficulties with supraglottic airway device insertion and ventilation as well.
Declaration of interest None declared. L. G. Theiler* R. Greif Bern, Switzerland * E-mail: [email protected] 1 Theiler L, Gutzmann M, Kleine-Brueggeney M, Urwyler N, Kaempfen B, Greif R. i-gelTM supraglottic airway in clinical practice: a prospective observational multicentre study. Br J Anaesth 2012; 109: 990– 5
doi:10.1093/bja/aet565
In science, all facts, no matter how trivial or banal, enjoy democratic equality
Declaration of interest None declared. M. Sramek* Ch. Keijzer Amsterdam, The Netherlands * E-mail: [email protected] 1 Theiler L, Gutzmann M, Kleine-Brueggeney M, Urwyler N, Kaempfen B, Greif R. i-gelTM supraglottic airway in clinical practice: a prospective observational multicentre study. Br J Anaesth 2012; 109: 990– 5 2 Keijzer Ch, Buitelaar D, Efthymiou KM, et al. A comparison of postoperative throat and neck complaints after the use of the i-gel and La Premiere disposable laryngeal Mask: a double blinded, randomized, controlled trial. Anesth Analg 2009; 109: 1097– 104
doi:10.1093/bja/aet564
Supraglottic airway devices as intubation aids Reply from the authors Editor—We read with interest the letter by Dr Sramek and Dr Keijzer. We are thankful for this valuable contribution. Dr Sramek correctly points out that the i-gel (and many other supraglottic airway devices) provide an excellent back-up device to fibreoptically intubate a patient with a difficult airway. It is especially noteworthy that an awake technique should remain the gold standard in expected difficult airway management. As we have shown in our study cited by Dr Sramek, there is an overlap of risk factors predicting
Editor—In the alluring and rapidly expanding field of developmental anaesthetic neurotoxicity, facts have been accumulating at a tremendous rate. The overview of recent work in this area provided by Sanders and colleagues,1 covering both laboratory and clinical studies, is therefore a welcome addition to the literature. However, rather than providing a critical and unbiased evaluation of the all-important hypothesis—that a clinically relevant neurotoxic effect of anaesthetics exists—like most other investigators in the field, the authors approach the topic with an implicit assumption that any demonstrable effect must be meaningful. Indeed, already in the introduction, the burden of proof is squarely placed on those questioning the existence of the condition under study when the authors write, ‘these accumulating clinical data cannot exclude a clinically important effect . . . on cognition in later life’. In science, proof of non-existence of anything is notoriously difficult, if not outright impossible. Therefore, one must consider whether current knowledge justifies treating the clinical relevance of anaesthetic neurotoxicity as an established paradigm (and hence the demand to demonstrate its non-existence) as opposed to a hypothesis still awaiting proof. With respect to rodent data, which constitute the bulk of available information, it is worth pointing out that most experiments were conducted using inbred strains. Inbreeding, by reducing genetic variability, may create both susceptibility to injury and limit compensatory potential, adding to the problems of extrapolating from rodent data to the human condition. Therefore, the authors appropriately highlight the importance of studies in animals other than rodents. On this background, the lenience with which the methodological deficiencies of the piglet studies are downplayed is striking: the lack
387
Downloaded from http://bja.oxfordjournals.org/ at Georgetown University on July 11, 2015
The high fibreoptic score using the i-gel was especially noteworthy. In only 2% of the cases, it was not possible to see the vocal cords.2 In our hospital, we have a considerable number of difficult airways due to malignancies in the larynx/ pharynx. Although awake fibreoptic intubation remains the gold standard in many difficult airway patients, we increasingly use the i-gel for ventilation in patients with an interdental gap of ≥3 cm. Once the patient’s lungs are ventilated, we intubate the trachea using a flexible scope through the i-gel. When lubricated properly, an oral tracheal tube (size 7.0) can be effortlessly pushed along the flexible scope through the i-gel in between the vocal cords. Correct positioning is easily achievable using the scope. If desired, the i-gel can be removed while the tracheal tube is held in the correct place using surgical forceps. This method appears to be so successful that it is increasingly being used in our department in the case of an unexpected difficult airway. The main requirements for this technique are the use of an i-gel 4 (or 5) and an interdental gap of at least 3 cm. By using the i-gel for ventilation before tracheal intubation, one limits the number of manipulations in the larynx, thus reducing the development of swelling, hypersalivation, and potential bleeding.
BJA
Declaration of interest None declared.
388
M. Perouansky Wisconsin, USA E-mail: [email protected] 1 Sanders RD, Hassell J, Davidson AJ, Robertson NJ, Ma D. Impact of anaesthetics and surgery on neurodevelopment: an update. Br J Anaesth 2013; 110 (Suppl. 1): i53–72 2 Schubert H, Eiselt M, Walter B, Fritz H, Brodhun M, Bauer R. Isoflurane/ nitrous oxide anesthesia and stress-induced procedures enhance neuroapoptosis in intrauterine growth-restricted piglets. Intensive Care Med 2012; 38: 1205– 14 3 Rizzi S, Ori C, Jevtovic-Todorovic V. Timing versus duration: determinants of anesthesia-induced developmental apoptosis in the young mammalian brain. Ann N Y Acad Sci 2010; 1199: 43– 51 4 Bartels M, Althoff RR, Boomsma DI. Anesthesia and cognitive performance in children: no evidence for a causal relationship. Twin Res Hum Genet 2009; 12: 246–53 5 Colgrove J, Bayer R. Could it happen here? Vaccine risk controversies and the specter of derailment. Health Aff (Millwood) 2005; 24: 729–39 6 Nicoll A, Elliman D, Ross E. MMR vaccination and autism 1998. Br Med J 1998; 316: 715– 6
doi:10.1093/bja/aet566
Use of capnography may cause airway complications in intensive care Editor—It is widely acknowledged that the incidence of serious adverse airway events is higher in the intensive care and emergency department environments. NAP4 revealed that failure to use capnography has been implicated in poor outcomes after adverse airway events on intensive care units (ICUs).1 The use of capnography in UK ICUs is now becoming increasingly common,2 – 9 and follows a number of recommendations both nationally and internationally.10 – 12 We wish to highlight one potential safety implication of the introduction of this unfamiliar equipment to the ICU environment, and report a case where the use of capnography was contributory to the development of an airway emergency. A male patient was admitted to our neuro-intensive care unit. During his ITU stay, continuous waveform capnography was used as per departmental policy, and a tracheostomy placed to facilitate weaning from the ventilator. After the change of position of the patient, the end-tidal CO2 (E′CO2 ) line became entangled on the bedside, and despite the staff member taking care to watch the breathing circuit, the tracheostomy was partially displaced due to traction from the capnography line. The incident was managed as per national guidelines;13 however, the patient still sustained surgical emphysema and bilateral tension pneumothoraces necessitating immediate decompression and intercostal chest drains. The patient recovered from this episode. Upon further investigation of this event, we noted that the capnography line ran separately to the breathing circuit and was located on the monitoring system, rather than the
Downloaded from http://bja.oxfordjournals.org/ at Georgetown University on July 11, 2015
of control in one of them2 (an incomprehensible deficiency for a laboratory study) and the fact that only a single animal per drug condition was used in the other3 are buried rather than highlighted (inclusion of a study with a n¼1 per condition into a ‘systematic’ review is, per se, debatable). In contrast, the gloves are off when it comes to methodological criticisms of clinical studies, especially when the study casts doubt on the existence of a relevant toxic effect: their outcome measures (e.g. developmental milestones, learning achievement, academic performance) are dismissed on the grounds that they are too ‘coarse’, disregarding the possibility that these outcomes might in fact be those that matter in real life—as opposed to achievements on arbitrary behavioural scales for rodents or monkeys. Another ground for summarily dismissing inconvenient clinical studies is ‘small sample size’. For example, doubt is cast on the relevance of the study by Bartels and colleagues4 on the grounds that it included ‘only’ 1143 pairs of monozygotic twins! Small sample size is a valid concern, but the criticism seems to be arbitrary, since the total number of piglets was 42 (39+3 for the two studies cited), and the total number of monkeys enrolled in all seven studies was 91—and of these, only 12 (neither sex- nor otherwise matched) underwent behavioural assessment. In contrast, the unique strength of Bartel and colleagues’ work, that is, comparison of clinically relevant cognitive outcomes between ‘perfectly matched’ (monozygotic twins) populations, is largely ignored. Considering the enormity of the problem that good matching of controls represents, especially for comparing neurocognitive outcomes, this neglect of a unique strength of this study is striking. One might ask whether this sceptical criticism is justified at all—is not it in the public’s interest of ‘safety’ to assume the potential for toxicity? Should not everybody be alert, watchful, and critically cautious? As Sanders and colleagues note, surgery in children is rarely purely elective. However, it is also important to recognize that clinically relevant science is not insulated in an ivory tower of academic objectivity, where hypotheses are vetted thoroughly and dispassionately before carefully crafted experts’ conclusions, objective and reflecting the pinnacle of wisdom, are released to an obediently waiting, disciplined, and responsive public. Experience, especially in England with the pertussis and MMR vaccine scares of decades past, teaches us how scientific (mis)information can lead to irrational behaviour in wide swaths of the population.5 The excess morbidity from the pertussis vaccine panic in Britain has been estimated at 300 000 with 70 deaths.6 If irrationality of behaviour is proportional to the degree of stress, the potential damage from the ‘anaesthesia threat’ in necessary surgeries delayed or avoided is enormous. In summary, the authors have provided a very useful collection of pertinent facts from the existing literature in this field. The reader should be aware of the potential bias in the interpretation of the data.
Correspondence
