Supraglottic airway versus tracheal intubation and the risk of postoperative pulmonary complications

Abstract

It is nearly 40 yr since Dr Archie Brain first described his prototype of the laryngeal mask airway (LMA) in the British Journal of Anaesthesia.1Brain A.I.J. The laryngeal mask – a new concept in airway management.Br J Anaesth. 1983; 55: 801-805Abstract Full Text PDF PubMed Scopus (742) Google Scholar The introduction of the LMA as the first supraglottic airway (SGA) must surely be the outstanding development in anaesthesia for a generation. His new airway was designed for use during both spontaneous and positive pressure ventilation. Brain acknowledged that obtaining a good seal of the airway when inflation pressures were applied was of importance and that improvements would need to be made to the prototype by developing a range of sizes to improve the airway seal.1Brain A.I.J. The laryngeal mask – a new concept in airway management.Br J Anaesth. 1983; 55: 801-805Abstract Full Text PDF PubMed Scopus (742) Google Scholar Subsequently, a variety of changes have updated the prototype: for instance, an even larger size 5 was introduced, a drainage tube for clearance of gastric contents was incorporated into the structure, a change in shape was made for the intubating laryngeal mask (ILMA), and different materials were used to produce a disposable LMA. As with any new development, anaesthetists adapted their practice accordingly, introducing their own minor modifications to their anaesthetic technique when using an LMA. By 2001, concern was being expressed about the use of an LMA during abdominal surgery when neuromuscular blocking agents (NMBAs) were also given because of the risk of pulmonary aspiration of stomach contents.2Sidaras G. Hunter J.M. Editorial III: is it safe to artificially ventilate a paralysed patient through the laryngeal mask? The jury is still out.Br J Anaesth. 2001; 86: 749-753Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar However, in a meta-analysis of 547 publications in 1995, Brimacombe and Berry3Brimacombe J.R. Berry A. The incidence of aspiration associated with the laryngeal mask airway – a meta-analysis of published literature.J Clin Anesth. 1995; 7: 297-305Crossref PubMed Scopus (269) Google Scholar had found an incidence of pulmonary aspiration of only 0.02% when an LMA had been used during all types of surgical procedure. Certainly by 1996, artificial ventilation was being used in 44% of cases when an LMA was in place in the UK, but it is unclear how many of the 5236 patients reported by Verghese and Brimacombe,4Verghese C. Brimacombe J.R. Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage.Anesth Analg. 1996; 82: 129-133PubMed Google Scholar or in the Brimacombe and Berry3Brimacombe J.R. Berry A. The incidence of aspiration associated with the laryngeal mask airway – a meta-analysis of published literature.J Clin Anesth. 1995; 7: 297-305Crossref PubMed Scopus (269) Google Scholar report, had received an NMBA. There were only 44 critical incidents in the Verghese and Brimacombe4Verghese C. Brimacombe J.R. Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage.Anesth Analg. 1996; 82: 129-133PubMed Google Scholar report of which 18 were related to the airway. Regurgitation occurred in four patients and vomiting in two, but there was only one case of proved pulmonary aspiration of stomach contents. However, anecdotal reports continued to occur of aspiration of gastric contents even in non-obese patients undergoing upper abdominal surgery using an LMA and NMBA.5Griffin R.M. Hatcher I.S. Aspiration pneumonia and the laryngeal mask airway.Anaesthesia. 1990; 45: 1039-1040Crossref PubMed Scopus (85) Google Scholar Into the 21st century the practice of using NMBAs with an LMA became increasingly popular in the UK, even though some of us had expressed misgivings.2Sidaras G. Hunter J.M. Editorial III: is it safe to artificially ventilate a paralysed patient through the laryngeal mask? The jury is still out.Br J Anaesth. 2001; 86: 749-753Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar The 4th National Audit Project (NAP4) of the Royal College of Anaesthetists on major airway complications during anaesthesia in the UK in 20116Cook T.M. Woodall N. Frerk C. on behalf of the fourth national Audit ProjectMajor complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: Anaesthesia.Br J Anaesth. 2011; 106: 617-631Abstract Full Text Full Text PDF PubMed Scopus (1046) Google Scholar found an incidence of only 1 in 22 000 adverse airway events during anaesthesia with a resulting mortality of 1 in 180 000 cases. The rates of death or brain damage varied little between the airway devices used, although the numbers were too small to usefully discriminate. Aspiration of gastric contents had occurred in only 23 cases during anaesthesia. Planned airway management had been an LMA in 13, i-gel in one, tracheal tube in eight, and no airway in one patient. No details were provided on the use of NMBAs in the affected patients nor did the audit capture events deemed less catastrophic. Clinical practice in the USA with respect to SGAs varies, but is generally more conservative than in Europe. In the USA, SGAs are used less frequently for patients in the non-supine position, for prolonged surgery, or during laparoscopy. In this issue of the British Journal of Anaesthesia, Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar report a very large retrospective study of 59 991 adult patients in the USA on the risk of unplanned tracheal intubation in the PACU after the use of an SGA (48.9% of patients) compared with use of a tracheal tube during anaesthesia (51.1%). In every case, use of an SGA or tracheal tube was considered feasible. As this study included patients from 2008–18, the majority of the patients in the SGA group received a classic first-generation LMA. Use of an SGA increased over time with more frequent use in the later years of the study. The use of a tracheal tube was associated with a slightly higher risk of emergent tracheal reintubation than when an SGA had been used (adjusted absolute risk difference [ARD] 0.8%), and a higher risk of immediate postoperative hypoxaemia (ARD 3.9%) as measured by pulse oximetry. The incidence of postoperative pneumonia was greater in the tracheal tube than the SGA group for the length of hospital stay, but the potential causes of the pneumonia were not investigated. No attempt was made to rule out the possibility of residual neuromuscular block being a potential cause of the respiratory complications. As the use of NMBAs was more common in the tracheal intubation group, Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar concluded that the difference in these findings between the tracheal intubation and SGA groups was mediated by the use of NMBAs. The findings were not affected by the type of surgery or patient comorbidity. Use of opioid analgesics, succinylcholine, or reversal agents did not affect the findings. The number of affected patients was relatively low: only 69 patients in the SGA group and 367 patients in the tracheal tube group required postoperative intubation. Of particular interest is that this effect was modified by use of NMBAs. Use of an NMBA in patients in whom an SGA had been used during general anaesthesia (only 459 of the 27 398 patients) led to a reduction in the preventative effects of SGA use on the need for emergent tracheal intubation. If the patient had received an NMBA and an SGA, the risk was actually higher than in the tracheal tube plus NMBA group (adjusted odds ratio 3.65), However, the risk increased whichever airway was used. The limitations of large retrospective studies are well recognised.8Bartels K. Hunter J.M. Neostigmine versus sugammadex: the tide may be turning, but we still need to navigate the winds.Br J Anaesth. 2020; 124: 504-507Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar However, Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar made exhaustive statistical efforts to account for known confounding. Sceptics may suggest that it is impossible to identify subtle variations in clinical judgement. What actually makes anaesthetists decide on the use of an SGA rather than a tracheal tube at the beginning of anaesthesia, when use of either is feasible? Inevitably, unidentified confounders would have influenced these findings. Similarly, it is much easier to obtain accurate and reproducible measurements of SpO2 in a patient after LMA removal whilst still anaesthetised than in a restless patient who has just been extubated after reversal of neuromuscular block. Use of an NMBA may also be an indicator of the need for positive pressure ventilation as opposed to spontaneous ventilation with or without pressure support: this was taken into account in part by Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar with respect to the surgical procedure. Positive pressure ventilation itself can lead to postoperative diaphragmatic dysfunction that may have influenced the results.9Sasaki N. Meyer M.J. Eikermann M. Postoperative respiratory muscle dysfunction: pathophysiology and preventative strategies.Anesthesiology. 2013; 118: 961-978Crossref PubMed Scopus (70) Google Scholar Different ventilation strategies such as the mode of ventilation (pressure or volume) and degree of PEEP, and use of protective ventilation together with recruitment manoeuvres can also have differing effects on postoperative pulmonary complications.10Bagchi A. Rudolph M.I. Ng P.Y. et al.The association of postoperative pulmonary complications in 109,360 patients with pressure-controlled or volume-controlled ventilation.Anaesthesia. 2017; 72: 1334-1343Crossref PubMed Scopus (31) Google Scholar,11Miskovic A. Lumb A.B. Postoperative pulmonary complications.Br J Anaesth. 2017; 118: 317-334Abstract Full Text Full Text PDF PubMed Scopus (237) Google Scholar Nevertheless, the findings reported by Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar are important as they could affect clinical practice directly. Ideally, findings of such clinical relevance would be substantiated by a prospective randomised cohort study, but the challenges of such are formidable. It would need to be a multicentre controlled study of many thousands of patients and funding issues could be anticipated. If such a study were funded by the medical device industry, it would be difficult to avoid conflicts of interest. Quantitative neuromuscular monitoring perioperatively would be essential with a standardised approach to reversal to rule out residual neuromuscular block as the cause of the pulmonary complications, and use of only one type of SGA would have to be considered. Finally, a recognised definition of postoperative pulmonary complications would need to be applied.8Bartels K. Hunter J.M. Neostigmine versus sugammadex: the tide may be turning, but we still need to navigate the winds.Br J Anaesth. 2020; 124: 504-507Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar Use of NMBAs during anaesthesia has been repeatedly shown to increase the risk of both immediate and longer term postoperative pulmonary complications in the days after surgery. In a prospective observational study in Europe (POPULAR), Kirmeier and colleagues12Kirmeier W. Eriksson L.I. Lewald H. et al.Post-anaesthesia pulmonary complications after use of muscle relaxants (POPULAR): a multicentre, prospective observational study.Lancet Respir Med. 2019; 7: 129-140Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar reported that use of NMBAs perioperatively was associated with an increased risk of postoperative pulmonary complications (odds ratio=1.86) and that use of a reversal agent, neuromuscular monitoring, or both did not decrease that risk. The odds ratio of 1.86 is not as strong as the effect of the surgical procedure or the patient's preoperative condition on outcome, but is nevertheless significant. These findings substantiated the results of retrospective studies from the USA,13Grosse-Sundrup M. Henneman J.P. Sandberg W.S. et al.Intermediate acting non-depolarizing neuromuscular blocking agents and risk of postoperative respiratory complications: prospective propensity score matched cohort study.BMJ. 2012; 345: e6329Crossref PubMed Scopus (170) Google Scholar,14Bulka C.M. Terekhov M.A. Martin B.J. Dmochowski R.R. Hayes R.M. Ehrenfeld J.M. Non-depolarizing neuromuscular blocking agents, reversal, and risk of postoperative pneumonia.Anesthesiology. 2016; 125: 647-655Crossref PubMed Scopus (82) Google Scholar and the study by Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar lends further support to these earlier findings. Although use of an NMBA reduces the trauma of tracheal intubation,15Lundstrom L.H. Duez C.H.V. Norskov A.K. et al.Effects of avoidance or use of neuromuscular blocking agents on outcomes in tracheal intubation: a Cochrane systematic review.Br J Anaesth. 2018; 120: 1381-1393Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar insertion of a tracheal tube is more traumatic to the pharynx and larynx than insertion of an SGA.16Park S.K. Ko G. Choi G.J. Ahn E.J. Kang H. Comparison between supraglottic airway devices and endotracheal tubes in patients undergoing laparoscopic surgery. A systematic review and meta-analysis.Medicine. 2016; 95 (Baltimore): e4598Crossref PubMed Scopus (21) Google Scholar However, data from NAP46Cook T.M. Woodall N. Frerk C. on behalf of the fourth national Audit ProjectMajor complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: Anaesthesia.Br J Anaesth. 2011; 106: 617-631Abstract Full Text Full Text PDF PubMed Scopus (1046) Google Scholar would suggest that in clinical practice neither device is a cause for major concern in this respect. Importantly, Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar found that even without the use of an NMBA, tracheal intubation was associated with harm, but the causes were not clear. Observation of gastric aspiration is an important outcome, but micro-aspiration may be more frequent and more relevant than we acknowledge during airway management, and is difficult to detect reliably in clinical studies. Use of cricoid pressure will not necessarily reduce this risk.17Birenbaum A. Hajage D. Riou B. Effect of cricoid pressure compared with a sham procedure in the rapid sequence induction of anesthesia.JAMA Surg. 2019; 154: 9-17Crossref PubMed Scopus (55) Google Scholar It remains plausible that micro-aspiration is more frequent around an SGA than a tracheal tube, but these effects may be mitigated by a higher rate of vocal cord dysfunction after tracheal extubation compared with SGA removal.18Radu A.D. Miled F. Marret E. Vigneau A. Bonnet F. Pharyngo-laryngeal discomfort after breast surgery: comparison between orotracheal intubation and laryngeal mask.Breast. 2008; 17: 407-411Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar As laryngeal morbidity is reduced with use of an SGA compared with tracheal intubation,19Hohlrieder M. Brimacombe J. von Goedecke A. Keller C. Postoperative nausea, vomiting, airway morbidity, and analgesia requirements are lower for the ProSeal laryngeal mask airway than the tracheal tube in females undergoing breast and gynaecological surgery.Br J Anaesth. 2007; 99: 576-580Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar the protective functions of the larynx may serve to reduce postoperative pulmonary complications with the use of an SGA, especially if no NMBA has been given. The well-recognised residual effects of NMBAs on pharyngeal and laryngeal muscles at the end of anaesthesia11Miskovic A. Lumb A.B. Postoperative pulmonary complications.Br J Anaesth. 2017; 118: 317-334Abstract Full Text Full Text PDF PubMed Scopus (237) Google Scholar may be another factor in the reduced benefits of using an SGA together with an NMBA. In the report by Hammer and colleagues,7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar the study population primarily utilised a first-generation LMA, although practice was changing in this respect over the course of their study. However, when they repeated their analysis using only data from the final 5 yr of their study, when use of various second-generation SGAs was becoming commonplace, their findings were unchanged. Evidence and guidance from translational models and expert opinion suggests that use of a second-generation SGA such as the ProSeal rather than an LMA may reduce the risk of pulmonary aspiration.20Keller C. Brimacombe J. Kleinsasser A. Loeckinger A. Does the ProSeal laryngeal mask airway prevent aspiration of regurgitated fluid?.Anesth Analg. 2000; 91: 1017-1020Crossref PubMed Scopus (166) Google Scholar,21Cook T.M. Kelly F.E. Time to abandon the “vintage” laryngeal mask airway and adopt second-generation supraglottic airway devices as first choice.Br J Anaesth. 2015; 115: 497-499Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar However, evidence supporting use of second-generation SGAs is more robust for outcomes related to improved placement success and pharyngeal seal than the risk of aspiration,22de Montblanc J. Ruscio L. Mazoit J.X. Benhamou D. A systematic review and meta-analysis of the i-gel vs laryngeal mask airway in adults.Anaesthesia. 2014; 69: 1151-1162Crossref PubMed Scopus (40) Google Scholar, 23Cook T.M. Lee G. Nolan J.P. The proseal laryngeal mask airway: a review of the literature.Can J Anesth. 2005; 52: 739-760Crossref PubMed Scopus (201) Google Scholar, 24Maitra S. Khanna P. Baidya D.K. Comparison of laryngeal mask airway Supreme and laryngeal mask airway Pro-Seal for controlled ventilation during general anaesthesia in adult patients: systematic review with meta-analysis.Eur J Anaesth. 2014; 31: 266-273Crossref PubMed Scopus (36) Google Scholar although these factors may be inter-related. It remains possible that patients in the SGA group in the study by Hammer and colleagues,7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar who received an NMBA, simply had a poor airway seal and the NMBA had been used to improve ventilatory parameters. Hence, drawing the conclusion from this study that NMBA use with an SGA may be harmful could be premature. A difficult seal of the SGA may be the risk exposure of interest in future studies of pulmonary outcomes. It is also possible that the requirement for NMBA use is reduced with the use of second-generation SGAs that provide a better seal. Comparative studies of different SGA designs have generally demonstrated similar seal pressures,25Teoh W.H.L. Lee K.M. Suhitharan T. Yahaya Z. Teo M.M. Sia A.T.H. Comparison of the LMA Supreme vs the i-gelTM in paralysed patients undergoing gynaecological laparoscopic surgery with controlled ventilation.Anaesthesia. 2010; 65: 1173-1179Crossref PubMed Scopus (93) Google Scholar, 26Theiler L.G. Kleine-Brueggeney M. Kaiser D. et al.Crossover comparison of the Laryngeal Mask SupremeTM and the i-gelTM in simulated difficult airway scenario in anesthetized patients.Anesthesiology. 2009; 11: 55-62Crossref Scopus (123) Google Scholar, 27Joly N. Poulin L.-P. Tanoubi I. Drolet P. Donati F. St-Pierre P. Randomized prospective trial comparing two supraglottic airway devices: i-gelTM and LMA-SupremeTM in paralyzed patients.Can J Anaesth. 2014; 61: 794-800Crossref PubMed Scopus (17) Google Scholar but comparative evaluation of aspiration risk remains too difficult to conduct in most clinical trial designs. As such, recommendations for use of specific second-generation SGAs tend to be guided by the experience and preference of the anaesthesiologist, but the class as a whole may improve sealing pressures and reduce the requirement for NMBAs. Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar should be congratulated for applying the most rigorous standards of observational research to their cohort to help answer a question, exploring variables associated with their findings, and offering conclusions based on study limitations. Their findings indicate the need for a prospective study, preferably using only one type of second-generation SGA. There may well be variation between different second-generation SGAs in this respect which also needs to be determined. The findings should motivate clinicians once again to consider critically the need for positive pressure ventilation when the surgery itself does not indicate it and importantly, whether NMBAs are really required. Similar messages arose from the POPULAR study.12Kirmeier W. Eriksson L.I. Lewald H. et al.Post-anaesthesia pulmonary complications after use of muscle relaxants (POPULAR): a multicentre, prospective observational study.Lancet Respir Med. 2019; 7: 129-140Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar Kirmeier and colleagues12Kirmeier W. Eriksson L.I. Lewald H. et al.Post-anaesthesia pulmonary complications after use of muscle relaxants (POPULAR): a multicentre, prospective observational study.Lancet Respir Med. 2019; 7: 129-140Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar stressed that their findings suggest the potential benefits of NMBAs must always be balanced against the increased risk of postoperative pulmonary complications after using these drugs. SGAs are less traumatic to the larynx than laryngoscopy with tracheal intubation, so the preserved functions of the larynx may have influenced the findings of Hammer and colleagues.7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar We suggest that anaesthesiologists should focus increasingly on the avoidance of NMBAs whenever possible, and we advise caution in the use of an SGA with an NMBA. The selection of an SGA suitable for optimal seal in the individualised patient, based on the experience of the anaesthesiologist, may serve to reduce the need for NMBAs. The findings of Hammer and colleagues7Hammer M. Santer P. Schaefer M. et al.Supraglottic airways vs. endotracheal intubation and the risk of emergent postoperative intubation: a retrospective cohort study in adult patients undergoing general anaesthesia.Br J Anaesth. 2021; https://doi.org/10.1016/j.bja.2020.10.040Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar provide us all with food for thought. Both authors contributed equally to the writing of this manuscript. JMH was editor-in-chief of the British Journal of Anaesthesia from 1997 to 2005, and chair of the British Journal of Anaesthesia Board from 2006 to 2012. MA is a member of the associate editorial board of the British Journal of Anaesthesia, senior editor of Anesthesia and Analgesia, and editor-in-chief of the Journal of Head and Neck Anesthesia. Supraglottic airway device versus tracheal intubation and the risk of emergent postoperative intubation after general anaesthesia in adults: a retrospective cohort studyBritish Journal of AnaesthesiaVol. 126Issue 3PreviewWe examined the association between emergent postoperative tracheal intubation and the use of supraglottic airway devices (SGAs) vs tracheal tubes. Full-Text PDF