Patient safety

Selected bibliography supporting the ten essential objectives for safe surgery

3. The team will recognize and effectively prepare for life-threatening loss of airway or respiratory function.

(1993). "Practise Guidelines for Management of the Difficult Airway. A Report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway." Anesthesiology 78: 597-602.

Cormack, R. S. and J. Lehane (1984). "Difficult tracheal intubation in obstetrics." Anaesthesia 39(11): 1105-11.

  • Difficult intubation has been classified into four grades, according to the view obtainable at laryngoscopy. Frequency analysis suggests that, in obstetrics, the main cause of trouble is grade 3, in which the epiglottis can be seen, but not the cords. This group is fairly rare so that a proportion of anaesthetists will not meet the problem in their first few years and may thus be unprepared for it in obstetrics. However the problem can be simulated in routine anaesthesia, so that a drill for managing it can be practised. Laryngoscopy is carried out as usual, then the blade is lowered so that the epiglottis descends and hides the cords. Intubation has to be done blind, using the Macintosh method. This can be helpful as part of the training before starting in the maternity department, supplementing the Aberdeen drill.

Crosby, E. T., R. M. Cooper, et al. (1998). "The unanticipated difficult airway with recommendations for management." Can J Anaesth 45(8): 757-76.

  • PURPOSE: To review the current literature and generate recommendations on the role of newer technology in the management of the unanticipated difficult airway.
  • METHODS: A literature search using key words and filters of English language and English abstracted publications from 1990-96 contained in the Medline, Current Contents and Biological Abstracts databases was carried out. The literature was reviewed and condensed and a series of evidence-based recommendations were evolved.
  • CONCLUSIONS: The unanticipated difficult airway occurs with a low but consistent incidence in anaesthesia practice. Difficult direct laryngoscopy occurs in 1.5-8.5% of general anaesthetics and difficult intubation occurs with a similar incidence. Failed intubation occurs in 0.13-0.3% general anaesthetics. Current techniques for predicting difficulty with laryngoscopy and intubation are sensitive, non-specific and have a low positive predictive value. Assessment techniques which utilize multiple characteristics to derive a risk factor tend to be more accurate predictors. Devices such as the laryngeal mask, lighted stylet and rigid fibreoptic laryngoscopes, in the setting of unanticipated difficult airway, are effective in establishing a patient airway, may reduce morbidity and are occasionally lifesaving. Evidence supports their use in this setting as either alternatives to facemask and bag ventilation, when it is inadequate to support oxygenation, or to the direct laryngoscope, when tracheal intubation has failed. Specifically, the laryngeal mask and Combitube have proved to be effective in establishing and maintaining a patent airway in "cannot ventilate" situations. The lighted stylet and Bullard (rigid) fibreoptic scope are effective in many instances where the direct laryngoscope has failed to facilitate tracheal intubation. The data also support integration of these devices into strategies to manage difficult airway as the new standard of care. Training programmes should ensure graduate physicians are trained in the use of these alternatives. Continuing medical education courses should allow physicians in practice the opportunity to train with these alternative devices.

Mallampati, S., S. Gatt, et al. (1985). "A clinical sign to predict difficult tracheal intubation: a prospective study." Can Anaesth Soc J 32: 429-434.

Murphy, M. and D. J. Doyle (2008). Airway evaluation. Management of the Difficult and Failed Airway. O. Hung and M. Murphy. New York, McGraw Hill: 3-15.

Paix, A. D., J. A. Williamson, et al. (2005). "Crisis management during anaesthesia: difficult intubation." Qual Saf Health Care 14(3): e5.

  • BACKGROUND: Anaesthetists may experience difficulty with intubation unexpectedly which may be associated with difficulty in ventilating the patient. If not well managed, there may be serious consequences for the patient. A simple structured approach to this problem was developed to assist the anaesthetist in this difficult situation.
  • OBJECTIVES: To examine the role of a specific sub-algorithm for the management of difficult intubation.
  • METHODS: The potential performance of a structured approach developed by review of the literature and analysis of each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved.
  • RESULTS: There were 147 reports of difficult intubation capable of analysis among the first 4000 incidents reported to AIMS. The difficulty was unexpected in 52% of cases; major physiological changes occurred in 37% of these cases. Saturation fell below 90% in 22% of cases, oesophageal intubation was reported in 19%, and an emergency transtracheal airway was required in 4% of cases. Obesity and limited neck mobility and mouth opening were the most common anatomical contributing factors.
  • CONCLUSION: The data confirm previously reported failures to predict difficult intubation with existing preoperative clinical tests and suggest an ongoing need to teach a pre-learned strategy to deal with difficult intubation and any associated problem with ventilation. An easy-to-follow structured approach to these problems is outlined. It is recommended that skilled assistance be obtained (preferably another anaesthetist) when difficulty is expected or the patient's cardiorespiratory reserve is low. Patients should be assessed postoperatively to exclude any sequelae and to inform them of the difficulties encountered. These should be clearly documented and appropriate steps taken to warn future anaesthetists.

Samsoon, G. and J. Young (1987). "Difficult tracheal intubation: a retrospective study. ." Anaesthesia 42: 487-490.

Shiga, T., Z. Wajima, et al. (2005). "Predicting difficult intubation in apparently normal patients: a meta-analysis of bedside screening test performance." Anesthesiology 103(2): 429-37.

  • The objective of this study was to systematically determine the diagnostic accuracy of bedside tests for predicting difficult intubation in patients with no airway pathology. Thirty-five studies (50,760 patients) were selected from electronic databases. The overall incidence of difficult intubation was 5.8% (95% confidence interval, 4.5-7.5%). Screening tests included the Mallampati oropharyngeal classification, thyromental distance, sternomental distance, mouth opening, and Wilson risk score. Each test yielded poor to moderate sensitivity (20-62%) and moderate to fair specificity (82-97%). The most useful bedside test for prediction was found to be a combination of the Mallampati classification and thyromental distance (positive likelihood ratio, 9.9; 95% confidence interval, 3.1-31.9). Currently available screening tests for difficult intubation have only poor to moderate discriminative power when used alone. Combinations of tests add some incremental diagnostic value in comparison to the value of each test alone. The clinical value of bedside screening tests for predicting difficult intubation remains limited.