Prediction and Outcomes of Impossible Mask Ventilation

Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
Anesthesiology (Impact Factor: 5.88). 04/2009; 110(4):891-7. DOI: 10.1097/ALN.0b013e31819b5b87
Source: PubMed


There are no existing data regarding risk factors for impossible mask ventilation and limited data regarding its incidence. The authors sought to determine the incidence, predictors, and outcomes associated with impossible mask ventilation.
The authors performed an observational study over a 4-yr period. For each adult patient undergoing a general anesthetic, preoperative patient characteristics, detailed airway physical exam, and airway outcome data were collected. The primary outcome was impossible mask ventilation defined as the inability to exchange air during bag-mask ventilation attempts, despite multiple providers, airway adjuvants, or neuromuscular blockade. Secondary outcomes included the final, definitive airway management technique and direct laryngoscopy view. The incidence of impossible mask ventilation was calculated. Independent (P < 0.05) predictors of impossible mask ventilation were identified by performing a logistic regression full model fit.
Over a 4-yr period from 2004 to 2008, 53,041 attempts at mask ventilation were recorded. A total of 77 cases of impossible mask ventilation (0.15%) were observed. Neck radiation changes, male sex, sleep apnea, Mallampati III or IV, and presence of beard were identified as independent predictors. The receiver-operating-characteristic area under the curve for this model was 0.80 +/- 0.03. Nineteen impossible mask ventilation patients (25%) also demonstrated difficult intubation, with 15 being intubated successfully. Twelve patients required an alternative intubation technique, including two surgical airways and two patients who were awakened and underwent successful fiberoptic intubation.
Impossible mask ventilation is an infrequent airway event that is associated with difficult intubation. Neck radiation changes represent the most significant clinical predictor of impossible mask ventilation in the patient dataset.

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    • "Neuromuscular blockade with rocuronium facilitated mask ventilation significantly compared with saline; in all 42 patients with rocuronium, ventilation was possible by mask [26]. In an observational study of 53041 patients in whom mask ventilation was attempted, it was impossible in 77 (0.15%); 73 patients had received a neuromuscular blocking drug during management of the airway and neuromuscular blockade did not improve matters [27]. Changes caused by radiotherapy of the neck were the most important risk factor for impossible mask ventilation [27]. "
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    ABSTRACT: BackgroundTracheal intubation without muscle relaxants is usually performed with remifentanil and propofol or sevoflurane. Remifentanil 1.0 to 4.0 μg·kg-1 and propofol 2.0-3.0 mg·kg-1 or sevoflurane up to 8.0 Vol% provide acceptable, i.e. excellent or good intubating conditions. We hypothesized that sevoflurane 1.0 MAC would provide acceptable intubating conditions when combined with propofol and remifentanil.MethodsEighty-three patients to be intubated were randomised to two groups. The SEVO group received propofol 1.5 mg kg-1, remifentanil 0.30 μg kg min-1 and sevoflurane 1.0 MAC; the MR group received the same doses of propofol and remifentanil plus rocuronium 0.45 mg kg-1. We evaluated intubation and extubation conditions, mean arterial pressure (MAP), heart rate (HR) and bispectral index (BIS). The vocal cords were examined for injury by videolaryngoscopy before and 24 hours after surgery.ResultsAcceptable intubating conditions were seen more frequently with rocuronium than with sevoflurane: 97% versus 82%; p = 0.03; the subscore for vocal cords was comparable: 100% versus 98%. MAP before intubation decreased significantly compared with the MAP at baseline to the same extent in both groups; ephedrine IV was given in 15 (SEVO) versus 16 (MR) patients; p = 0.93. BIS at tracheal intubation was 27 (13-65) in the SEVO group, 29 (14-62) in the MR group; p = 0.07. Vocal cord injuries (oedema, haematoma) were similar: 4 patients in each group.ConclusionsOverall intubating conditions were better when rocuronium was used; the subscore for vocal cords was comparable. The incidence of side effects was the same in the two groups.Trial registrationClinicalTrials.Gov: NCT 01591031.
    BMC Anesthesiology 05/2014; 14:39. DOI:10.1186/1471-2253-14-39 · 1.38 Impact Factor
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    • "In the present study, deficiencies in pre-printed documentation of airway elements in the anaesthesia records were observed; for example, for mask ventilation and the number of intubation attempts. These clinically important variables have previously been associated with difficult airway; [26] therefore, routinely documenting this is suggested. Furthermore, inadequate preoperative airway documentation has been shown to increase adverse airway events during anaesthesia [27] and standardised documentation of airway variables in anaesthesia records have been identified as important for patient safety [28,29]. "
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    ABSTRACT: In Sweden, airway guidelines aimed toward improving patient safety have been recommended by the Swedish Society of Anaesthesia and Intensive Care Medicine. Adherence to evidence-based airway guidelines is known to be generally poor in Sweden. The aim of this study was to determine whether airway guidelines are present in Swedish anaesthesia departments. A nationwide postal questionnaire inquiring about the presence of airway guidelines was sent out to directors of Swedish anaesthesia departments (n = 74). The structured questionnaire was based on a review of the Swedish Society of Anaesthesia and Intensive Care voluntary recommendations of guidelines for airway management. Mean, standard deviation, minimum/maximum, percentage (%) and number of general anaesthesia performed per year as frequency (n), were used to describe, each hospital type (university, county, private). For comparison between hospitals type and available written airway guidelines were cross tabulation used and analysed using Pearson's Chi-Square tests. A p- value of less than 0 .05 was judged significant. In total 68 directors who were responsible for the anaesthesia departments returned the questionnaire, which give a response rate of 92% (n 68 of 74). The presence of guidelines showing an airway algorithm was reported by 68% of the departments; 52% reported having a written patient information card in case of a difficult airway and guidelines for difficult airways, respectively; 43% reported the presence of guidelines for preoperative assessment; 31% had guidelines for Rapid Sequence Intubation; 26% reported criteria for performing an awake intubation; and 21% reported guidelines for awake fibre-optic intubation. A prescription for the registered nurse anaesthetist for performing tracheal intubation was reported by 24%. The most frequently pre-printed preoperative elements in the anaesthesia record form were dental status and head and neck mobility. Despite recommendations from the national anaesthesia society, the presence of airway guidelines in Swedish anaesthesia departments is low. From the perspective of safety for both patients and the anaesthesia staff, airway management guidelines should be considered a higher priority.
    BMC Anesthesiology 04/2014; 14(1):25. DOI:10.1186/1471-2253-14-25 · 1.38 Impact Factor
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    • "During the DIFFICAIR trial, an internet page in the DAD will enable pre-operative registration of risk factors comprised in the SARI model. Kheterpal et al. described several risk factors associated with DMV [11,12]. Predictors for DMV will be a part of the data assessed and recorded in DAD in addition to the SARI score. "
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    ABSTRACT: Pre-operative airway assessment in Denmark is based on a non-specific clinical assessment. Systematic, evidence-based and consistent airway assessment may reduce the incidence of unanticipated difficult airway management. By assessing multiple predictors for difficult airway management, the predictive value of the assessment increases. The Simplified Airway Risk Index (SARI) is a multivariate risk score for predicting difficult intubation.This study aims to compare the use of the SARI with a non-specified clinical airway assessment on predicting difficult intubation. Further, to compare the examination and registration of predictors for difficult mask ventilation with a non-specified clinical airway assessment on prediction of difficult mask ventilation.Method/Design: We cluster-randomized 28 Danish departments of anaesthesia to airway assessment either by the SARI or by usual non-specific assessment. Data from patients' pre-operative airway assessment are registered in the Danish Anaesthesia Database. Objective scores for intubation and mask ventilation grade the severity of airway managements. The accuracy of predicting difficult intubation and mask ventilation is measured for each group. The primary outcome measure is the fraction of unanticipated difficult and easy intubation.The fraction of unanticipated difficult intubation in Denmark is 1.87%. With a stratified randomization, type 1 error risk of 5% and a power of 80%, 30 departments are required to detect or reject a 30% relative risk reduction equalling a number needed to treat of 180. Sample size estimation is adjusted for the study design and based on standards for randomization on cluster-level. With an average cluster size of 2,500 patients, 70,000 patients will be enrolled over a 1-year trial period. The database is programmed so that registration of the SARI and predictors for difficult mask ventilation are mandatory for the intervention group but invisible to controls. It is innovative to use a national clinical database as the basis for a randomized clinical trial. The method can serve as a precedent for implementation of evidence-based recommendations and database registration.The trial will forward understanding of how to predict and reduce unanticipated difficult airways and how to produce evidence-based recommendations for airway assessment and clinical database development.Trial registration: (NCT01718561).
    Trials 10/2013; 14(1):347. DOI:10.1186/1745-6215-14-347 · 1.73 Impact Factor
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