‘Herculean’ Study of Airway Complications

Airway management experts are hailing a large-scale review of airway-related complications in the United Kingdom as “herculean,” saying it yields important insights into the nature of airway management complications. Based on the results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (NAP4), up to 75% of the 184 serious airway complications reported could have been averted if better airway management practices were used (Br J Anaesth 2011;106:617-631).
“The amount of information here is a treasure trove,” said Richard Cooper, MD, professor in the Department of Anesthesia at the University of Toronto, in Canada, and president-elect of the Society for Airway Management.
Lead investigator Tim Cook, MBBS, and his team analyzed data from a United Kingdom national registry that included 2.9 million general anesthesia procedures conducted between September 2008 and September 2009. The data included 184 serious airway complications that led to death, brain damage, emergency airway surgery, unanticipated admission to the intensive care unit (ICU) or prolonged ICU stay.
Two panels, each including at least five physicians from a range of clinical specialties, reviewed each complication and determined the precipitating factors, severity of the event and quality of airway management.
Of the complications, 133 occurred during anesthesia; 36 occurred in the ICU; and 15 events took place in an emergency department. Sixteen cases of anesthesia-related airway complications resulted in death; three led to brain damage; six were associated with a partial recovery; and 106 ended with complete recovery. Two patients with anesthesia-related airway complications died from complications not related to the airway.
Dr. Cook, consultant in the Department of Anaesthesia at Royal United Hospital, in Bath, England, said that approximately 40% of anesthesia-related airway complications developed in patients with acute or chronic head, neck or tracheal disease, and 70% of those occurred in patients with obstructive lesions.
Perhaps the most striking finding was that the quality of airway management was rated “good” in just 18% (24) of the 133 anesthesia-related airway complications (Table). “While bad things happen despite good care, in the NAP4 study too frequently did bad outcomes result from poor care,” Dr. Cooper said.
The findings point to a need for better airway management in obese patients. Specifically, 40% (53 of 133) of individuals with anesthesia-related airway complications had a body mass index more than 30 kg/m2. In this patient subpopulation, the investigators judged that airway management quality was “good” in 12 patients, “mixed” in 23 cases and “poor” in 15 cases; the quality of airway management was unclear in the remaining three cases.
“With obesity rates in the United States being considerably higher than in the U.K., this finding would be of particular interest to American physicians,” Dr. Cook told Anesthesiology News.
Contrasting Findings
Dr. Cooper said the nearest equivalent study in the United States to NAP4 was the retrospective analysis in 2005 of malpractice claims associated with difficult airway cases in the American Society of Anesthesiologists (ASA) Closed Claims Project (Anesthesiology 2005;103:33-39). The analysis included 179 claims filed with 35 insurance companies between 1985 and 1999.
One key difference between NAP4 and the 2005 closed claims analysis, according to Dr. Cooper, is the high level of enrollment in the U.K. National Health Service, which yields an estimate of the overall incidence of anesthesia-related airway complications of about one in every 22,000 general anesthesia procedures. By contrast, because there is no national health care registry in the United States, it is unclear whether the number of complications in the American setting matches the U.K. rate.
“All complications do not result in litigation, and thus may go undetected by the closed claims analysis,” Dr. Cooper said. “Furthermore, closed claims take years to run their course, and thus we may awaken to trends long after they have been addressed. So, the NAP4 findings need to be taken very seriously.”
One contrasting finding between the two countries’ analyses was that in the NAP4 study, 50% of airway-related deaths resulted from aspiration, Dr. Cooper said. “This is between three and five times higher than reported by the closed claims analysis.”
Carin Hagberg, MD, professor and chair of anesthesiology at the University of Texas Medical School at Houston, and executive director of the Society for Airway Management, said that claims in the Closed Claims Project were more likely to result from airway injury and pneumothorax. She said she was particularly struck by the 70% of airway-related deaths in the U.K. study that occurred in the ICU that were at least partly caused by failure to use capnography in ventilated patients.
“The researchers noted that increasing use of capnography in ICU patients is the single change with the greatest potential to prevent deaths such as those reported to NAP4,” Dr. Hagberg told Anesthesiology News. “Perhaps we should follow suit with the Association of Anaesthetists of Great Britain and Ireland, which recently published a statement urging that continuous capnography be used in all patients whose airways are being maintained.” (To access the guidelines, go to www.aagbi.org.)
Some of the findings of NAP4 are likely not applicable to the U.S. health care setting, Dr. Cooper said. For example, 56% of all general anesthesia procedures in NAP4 involved use of supraglottic airway devices, compared with 38% and 5.3% of procedures in which tracheal tubes and face masks, respectively, were used. “Supraglottic airway devices are likely used more often in the U.K., and thus there may be differences in the incidence of complications related to these devices,” he said.
Dr. Cooper also noted that in NAP4, 81% of adult patients with anticipated difficult airways received IV induction, whereas only 10% underwent awake bronchoscopic intubation. “This is a significant departure from the recommendations of the ASA algorithm for the management of the difficult airway.”
Still, although differences may exist between NAP4 and the ASA Closed Claims Project—and indeed between American and British airway management practices, in general—these should not detract from the take-home message of both analyses, Dr. Hagberg said. “At both individual and institutional levels, we need to become better educated, better skilled and better able to face the inevitable challenges of our practice,” she said.
The complete NAP4 report, as well as presentations and podcasts, can be found online at www.rcoa.ac.uk/index.asp?PageID=1089.