T. M. Cook

Major 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 2: intensive care and emergency departments

BACKGROUND The Fourth National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society (NAP4) was designed to identify and study serious airway complications occurring during anaesthesia, in intensive care unit (ICU) and the emergency department (ED). METHODS Reports of major complications of airway management (death, brain damage, emergency surgical airway, unanticipated ICU admission, prolonged ICU stay) were collected from all National Health Service hospitals over a period of 1 yr. An expert panel reviewed inclusion criteria, outcome, and airway management. RESULTS A total of 184 events met inclusion criteria: 36 in ICU and 15 in the ED. In ICU, 61% of events led to death or persistent neurological injury, and 31% in the ED. Airway events in ICU and the ED were more likely than those during anaesthesia to occur out-of-hours, be managed by doctors with less anaesthetic experience and lead to permanent harm. Failure to use capnography contributed to 74% of cases of death or persistent neurological injury. CONCLUSIONS At least one in four major airway events in a hospital are likely to occur in ICU or the ED. The outcome of these events is particularly adverse. Analysis of the cases has identified repeated gaps in care that include: poor identification of at-risk patients, poor or incomplete planning, inadequate provision of skilled staff and equipment to manage these events successfully, delayed recognition of events, and failed rescue due to lack of or failure of interpretation of capnography. The project findings suggest avoidable deaths due to airway complications occur in ICU and the ED.

The proseal™laryngeal mask airway: a review of the literature

PurposeTo analyze and summarize the published literature relating to the ProSeal LMA (PLMA): a modification of the ‘classic LMA’ (cLMA) with an esophageal drain tube (DT), designed to improve controlled ventilation, airway protection and diagnosis of misplacement.SourceArticles identified through Medline and EMBASE searches using keywords ‘Proseal’, ‘ProSeal’ and ‘PLMA’. Hand searches of these articles and major anesthetic journals from January 1998 to March 2005.Principal findingsSearches identified 59 randomized controlled trials or clinical studies and 79 other publications. Compared to the cLMA, PLMA insertion takes a few seconds longer. First attempt insertion success for the PLMA is lower, but overall success is equivalent. Airway seal is improved by 50%. The DT enables early diagnosis of mask misplacement, allows gastric drainage, reduces gastric inflation and may vent regurgitated stomach contents. Evidence suggests, but does not prove, that the correctly placed PLMA reduces aspiration risk compared with the cLMA. PLMA use is associated with less coughing and less hemodynamic disturbance than use of a tracheal tube (TT). Comparative trials of the PLMA with other supraglottic airways favour the PLMA. Clinicians have extended the use of the PLMA inside and outside the operating theatre including use for difficult airway management and airway rescue.ConclusionsThe PLMA has similar insertion characteristics and complications to other laryngeal masks. The DT enables rapid diagnosis of misplacement. The PLMA offers significant benefits over both the cLMA and TT in some clinical circumstances. These and clinical experience with the PLMA are discussed.RésuméObjectifAnalyser et résumer les publications sur le ML ProSeal (MLP): une modification du «ML classique» (MLc), muni ďun tube de drainage œsophagien (TD), conçu pour améliorer la ventilation contrôlée, la protection des voies aériennes et le diagnostic dďune malposition.SourceArticles trouvés dans les bases Medline et EMBASE à partir des mots clés «Proseal», «ProSeal» et «PLMA». Des recherches manuelles de ces articles et des principaux journaux dďanesthésie publiés de janvier 1998 à mars 2005.Constatations principalesNos recherches ont permis de découvrir 59 essais contrôlés et randomisés ou études cliniques et 79 autres publications. Ľinsertion du MLP, comparée à celle du MLc, prend quelques secondes de plus. Le taux ďinsertion réussie au premier essai avec le MLP est plus faible, mais le taux global est équivalent. Ľétanchéité de ďintubation est améliorée de 50 %. Le TD permet le diagnostic précoce ďune malposition du masque, assure le drainage gastrique, réduit le gonflement gastrique et permet de dégager les régurgitations de ľestomac. Il y a des indices, non des preuves, que le MLP bien placé, comparé au MLc, réduise le risque ďaspiration. Ľusage du MLP est associé à moins de toux et de perturbations hémodynamiques que ľusage du tube endotrachéal (TE). Des essais comparatifs du MLP et ďautres canules oropharyngées favorisent le MLP. Les cliniciens ont étendu ľusage du MLP à ľintérieur et à ľextérieur de la salle ďopération, entre autres pour ľintubation difficile ou le contrôle urgent des voies respiratoires.ConclusionLe MLP présente des caractéristiques ďinsertion et des complications semblables à celles ďautres masques laryngés. Le TD permet le diagnostic rapide ďune malposition. Le MLP offre des avantages significatifs par rapport au MLc et au TE dans certains contextes cliniques.

5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: summary of main findings and risk factors

We present the main findings of the 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia (AAGA). Incidences were estimated using reports of accidental awareness as the numerator, and a parallel national anaesthetic activity survey to provide denominator data. The incidence of certain/probable and possible accidental awareness cases was ~1:19,600 anaesthetics (95% confidence interval 1:16,700-23,450). However, there was considerable variation across subtypes of techniques or subspecialities. The incidence with neuromuscular block (NMB) was ~1:8200 (1:7030-9700), and without, it was ~1:135,900 (1:78,600-299,000). The cases of AAGA reported to NAP5 were overwhelmingly cases of unintended awareness during NMB. The incidence of accidental awareness during Caesarean section was ~1:670 (1:380-1300). Two-thirds (82, 66%) of cases of accidental awareness experiences arose in the dynamic phases of anaesthesia, namely induction of and emergence from anaesthesia. During induction of anaesthesia, contributory factors included: use of thiopental, rapid sequence induction, obesity, difficult airway management, NMB, and interruptions of anaesthetic delivery during movement from anaesthetic room to theatre. During emergence from anaesthesia, residual paralysis was perceived by patients as accidental awareness, and commonly related to a failure to ensure full return of motor capacity. One-third (43, 33%) of accidental awareness events arose during the maintenance phase of anaesthesia, mostly due to problems at induction or towards the end of anaesthesia. Factors increasing the risk of accidental awareness included: female sex, age (younger adults, but not children), obesity, anaesthetist seniority (junior trainees), previous awareness, out-of-hours operating, emergencies, type of surgery (obstetric, cardiac, thoracic), and use of NMB. The following factors were not risk factors for accidental awareness: ASA physical status, race, and use or omission of nitrous oxide. We recommend that an anaesthetic checklist, to be an integral part of the World Health Organization Safer Surgery checklist, is introduced as an aid to preventing accidental awareness. This paper is a shortened version describing the main findings from NAP5--the full report can be found at http://www.nationalauditprojects.org.uk/NAP5_home.

Complications and failure of airway management

Airway management complications causing temporary patient harm are common, but serious injury is rare. Because most airways are easy, most complications occur in easy airways: these complications can and do lead to harm and death. Because these events are rare, most of our learning comes from large litigation and critical incident databases that help identify patterns and areas where care can be improved: but both have limitations. The recent 4th National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society provides important detailed information and our best estimates of the incidence of major airway complications. A significant proportion of airway complications occur in Intensive Care Units and Emergency Departments, and these more frequently cause patient harm/death and are associated with suboptimal care. Hypoxia is the commonest cause of airway-related deaths. Obesity markedly increases risk of airway complications. Pulmonary aspiration remains the leading cause of airway-related anaesthetic deaths, most cases having identifiable risk factors. Unrecognized oesophageal intubation is not of only historical interest and is entirely avoidable. All airway management techniques fail and prediction scores are rather poor, so many failures are unanticipated. Avoidance of airway complications requires institutional and individual preparedness, careful assessment, good planning and judgement, good communication and teamwork, knowledge and use of a range of techniques and devices, and a willingness to stop performing techniques when they are failing. Analysis of major airway complications identifies areas where practice is suboptimal; research to improve understanding, prevention, and management of such complications remains an anaesthetic priority.

A quantitative review and meta-analysis of performance of non-standard laryngoscopes and rigid fibreoptic intubation aids

This quantitative review summarises studies of rigid fibreoptic laryngoscopy systems. In 6622 ‘normal’ patients only the Bonfils and CTrach had homogenous data and first time intubation success rates above 90%. In 1110 patients predicted or known to be difficult to intubate only the Bonfils, CTrach and Glidescope had homogenous data and first‐time success rates above 90%. In comparative studies with the Macintosh‐3 blade, no device had homogenous data in more than one study. Many devices had higher summed performances, but due to data heterogeneity, interpretation is very difficult, if worthwhile at all. The currently available data do not provide strong evidence that these devices should supersede standard direct laryngoscopy for routine or difficult intubation. Further research needs to be of high quality, studying relevant patients to create such evidence. Multicentre collaborations are likely to be needed studying known difficult patients or creating databases reporting the success/failure rate of these devices.

A new practical classification of laryngeal view

A new practical classification of laryngeal view at laryngoscopy is presented and evaluated. The best laryngeal view obtained with or without anterior laryngeal pressure is recorded. The laryngeal view is easy (E)when the laryngeal inlet is visible. The view is restricted (R) when the posterior glottic structures (posterior commissure or arytenoids) are visible or the epiglottis is visible and can be lifted; this includes some grade 2 and some grade 3 views as classified by Cormack and Lehane. A difficult (D) view is present when the epiglottis cannot be lifted or when no laryngeal structures are visible. Five hundred patients were studied. Laryngoscopy, with the patient anaesthetised and paralysed, was performed with a Macintosh laryngoscope. If the vocal cords were not visible, a gum elastic bougie was used to aid intubation. Other aids were used only if this did not allow intubation. Each laryngeal view was graded according to the new classification and that of Cormack and Lehane. Intubation was timed and the equipment needed to facilitate intubation was recorded. The new classification stratified increasing difficulty with intubation (time for intubation longer and increasingly complex methods needed) better than the Cormack and Lehane classification. The new classification is as sensitive and more specific than the Cormack and Lehane classification in predicting difficult intubation. It is also more sensitive and more specific in predicting easy intubation.

Combined spinal-epidural techniques

The combined spinal–epidural technique has been used increasingly over the last decade. Combined spinal–epidural may achieve rapid onset, profound regional blockade with the facility to modify or prolong the block. A variety of techniques and devices have been proposed. The technique cannot be considered simply as an isolated spinal block followed by an isolated epidural block as combining the techniques may alter each block. This review concentrates on technical and procedural aspects of combined spinal–epidural. Needle‐through‐needle, separate‐needle and combined‐needle techniques are described and modifications discussed. Failure rates and causes are reviewed. The problems of performing a spinal block before epidural blockade (potential for unrecognised placement of an epidural catheter, inability to detect paraesthesia during epidural placement, difficulty in testing the epidural, delay in positioning the patient) are described and evaluated. Problems of performing spinal block after epidural blockade (risk of catheter or spinal needle damage) are considered. Mechanisms of modification of spinal blockade by subsequent epidural drug administration are discussed. The review considers choice of technique, needle type, patient positioning and paramedian vs. midline approach. Finally, complications associated with combined spinal–epidural are reviewed.

Litigation related to anaesthesia: an analysis of claims against the NHS in England 1995-2007.

The distribution of medico‐legal claims in English anaesthetic practice is unreported. We studied National Health Service Litigation Authority claims related to anaesthesia since 1995. All claims were reviewed by three clinicians and variously categorised, including by type of incident, claimed outcome and cost. Anaesthesia‐related claims account for 2.5% of all claims and 2.4% of the value of all claims. Of 841 relevant claims 366 (44%) were related to regional anaesthesia, 245 (29%) obstetric anaesthesia, 164 (20%) inadequate anaesthesia, 95 (11%) dental damage, 71 (8%) airway (excluding dental damage), 63 (7%) drug related (excluding allergy), 31 (4%) drug allergy related, 31 (4%) positioning, 29 (3%) respiratory, 26 (3%) consent, 21 (2%) central venous cannulation and 18 (2%) peripheral venous cannulation. Defining which cases are, from a medico‐legal viewpoint, ‘high risk’ is uncertain, but the clinical categories with the largest number of claims were regional anaesthesia, obstetric anaesthesia, inadequate anaesthesia, dental damage and airway, those with the highest overall cost were regional anaesthesia, obstetric anaesthesia, and airway and those with the highest mean cost per closed claim were respiratory, central venous cannulation and drug error excluding allergy. The data currently available have limitations but offer useful information. A closed claims analysis similar to that in the USA would improve the clinical usefulness of analysis.

Evaluation of four manikins as simulators for teaching airway management procedures specified in the Difficult Airway Society guidelines, and other advanced airway skills*

Ten volunteers evaluated the performance of four currently available manikins: Airway Management TrainerTM, Airway TrainerTM, Airsim™ and Bill 1™ as simulators for the 16 procedures described in the Difficult Airway Society Guidelines (DAS techniques) and eight other advanced airway techniques (non‐DAS techniques), by scoring and ranking each manikin and procedure. Manikin performance was unequal (p < 0.0001 for both SCORE and RANK data for both DAS and non‐DAS techniques). Post hoc analysis ranked the manikins for DAS techniques as: 1st Laerdal, 2nd Trucorp, 3rd equal VBM and Ambu. For non‐DAS techniques, the ranking was: 1st equal Laerdal and Trucorp, 3rd equal VBM and Ambu. The power to discriminate for individual procedures was considerably lower but for 15 of 16 DAS techniques and 6 of 8 non‐DAS techniques, manikin performance differed significantly. Post hoc tests showed significant performance differences between individual manikins for 10 DAS procedures, with the Laerdal manikin performing best.

Litigation related to airway and respiratory complications of anaesthesia: an analysis of claims against the NHS in England 1995–2007

Claims notified to the NHS Litigation Authority in England between 1995 and 2007 and filed under anaesthesia were analysed to explore patterns of injury and cost related to airway or respiratory events. Of 841 interpretable claims the final dataset contained 96 claims of dental damage, 67 airway‐related claims and 24 respiratory claims. Claims of dental damage contributed a numerically important (11%), but financially modest (0.5%) proportion of claims. These claims predominantly described injury during tracheal intubation or extubation; a minority associated with electroconvulsive therapy led to substantial cost per claim. The total cost of (non‐dental) airway claims was £4.9 million (84% closed, median cost £30 000) and that of respiratory claims was £3.3 million (81% closed, median £27 000). Airway and respiratory claims account for 12% of anaesthesia‐related claims, 53% of deaths, 27% of cost and ten of the 50 most expensive claims in the dataset. Airway claims most frequently described events at induction of anaesthesia, involved airway management with a tracheal tube and typically led to hypoxia and patient death or brain injury. Airway trauma accounted for one third of airway claims and these included deaths from mediastinal injury at intubation. Pulmonary aspiration and tube misplacement, including oesophageal intubation, led to several claims. Among respiratory claims, ventilation problems, combined with hypoxia, were an important source of claims. Although limited clinical details hamper analysis, the data suggest that most airway and respiratory‐related claims arise from sentinel events. The absence of clinical detail and denominators limit opportunities to learn from such events; much more could be learnt from a closed claim or sentinel event analysis scheme.