The laryngeal mask airway

A new form of airway has recently been described, which is introduced blindly into the hypopharynx to form a seal around the larynx, so permitting spontaneous or positive pressure ventilation without penetration of the larynx or oesophagus. The further development of this new airway is described and the results of 18 months' clinical experience are presented. The airway was used successfully in 118 patients, 17 of whom received controlled ventilation of their lungs. It was used in place of the facemask in routine anaesthesia, and was of particular value in ophthalmic, dental and ear, nose and throat procedures and where difficulties with the airway were expected. The incidence of sore throat and other problems was low. Experience of more than 500 cases suggests that the laryngeal mask airway may have a valuable r?le to play in all types of inhalational anaesthesia, while its proven value in some cases of difficult intubation indicates that it may contribute significantly to the safety of general anaesthesia.     

The proseal laryngeal mask airway in prone patients: a retrospective audit of 245 patients

The use of the classic laryngeal mask airway (classic LMA) in the prone position is controversial, but the ProSeal laryngeal mask airway (ProSeal LMA) may be more suitable as it forms a better seal and provides access to the stomach. In the following retrospective audit, we describe our experience with the insertion of and maintenance of anaesthesia with, the ProSeal LMA in 245 healthy adults in the prone position by experienced users. The technique involved (1) the patient adopting the prone position with the head to the side and the table tilted laterally; (2) pre-oxygenation to end-tidal oxygen >90%; (3) induction of anaesthesia with midazolam/alfentanil/propofol; (4) facemask ventilation (5) a single attempt at digital insertion and if unsuccessful a single attempt at laryngoscope-guided, gum elastic bougie-guided insertion; (6) gastric tube insertion; (7) maintenance of anaesthesia with sevoflurane/O/N2O; (8) volume controlled ventilation at 8-12 ml/kg; (9) emergence from anaesthesia in the supine position; and (10) removal ofthe ProSeal LMA when awake. Facemask ventilation was always successful. ProSealLMA insertion was successful in all patients: 237 with digital insertion and eight with bougie-guided insertion. Ventilation was successful in all patients. Gastric tube insertion was successful in all patients. Correctable partial airway obstruction occurred in three patients, but there was no hypoxia, hypercapnoea, displacement, regurgitation, gastric insufflation or airway reflex activation. Our findings suggest that the insertion of and maintenance of anaesthesia with the ProSeal LMA is feasible in the prone position by experienced users.     

Supraglottic airways in difficult airway management: successes, failures, use and misuse

Supraglottic airway devices (SAD) play an important role in the management of patients with difficult airways. Unlike other alternatives to standard tracheal intubation, e.g. videolaryngoscopy or intubation stylets, they enable ventilation even in patients with difficult facemask ventilation and simultaneous use as a conduit for tracheal intubation. Insertion is usually atraumatic, their use is familiar from elective anaesthesia, and compared with tracheal intubation is easier to learn for users with limited experienced in airway management. Use of SADs during difficult airway management is widely recommended in many guidelines for the operating room and in the pre-hospital setting. Despite numerous studies comparing different SADs in manikins, there are few randomised controlled trials comparing different SADs in patients with difficult airways. Therefore, most safety data come from extended use rather than high quality evidence and claims of efficacy and particularly safety must be interpreted cautiously.     

A new risk of facemask ventilation: entrained esophageal air

Facemask ventilation has been associated with the development of postoperative nausea and vomiting, increasing the risk of tracheal aspiration; development of gastric distension that further impairs alveolar ventilation; perforation of gastric and duodenal ulcers; development of pneumothorax; extrabronchial air dissection; and development of cardiac dysrhythmias, including bradycardia from indirect vagal nerve stimulation. An unusual complication that occurred during prolonged facemask ventilation is presented: development of a pseudo-obstruction of the intrathoracic airway due to the presence of entrained esophageal air.     

Supraglottic airway devices in difficult airway management: a retrospective cohort study of 658,104 general anaesthetics registered in the Danish Anaesthesia Database

Indications for using supraglottic airway devices have widened over time and they now hold a prominent role in guidelines for difficult airway management. We aimed to describe the use of supraglottic airway devices in difficult airway management. We included adult patients undergoing general anaesthesia registered in the Danish Anaesthesia Database from 2008 to 2012 whose airway management had been recorded as difficult, defined as: ≥ 3 tracheal intubation attempts; failed tracheal intubation; or difficult facemask ventilation. In the Danish Anaesthesia Database, a separate difficult airway management module requires the technique used in each successive airway management attempt to be recorded. The primary aim of the study was to describe the use of supraglottic airway devices in cases of difficult airway management. Secondary aims were to examine success rates of supraglottic airway devices in difficult airway management cases, and specifically in the cases of ‘cannot intubate, cannot facemask ventilate’. Difficult airway management occurred in 4898 (0.74% (95%CI 0.72–0.76%)) of 658,104 records of general anaesthesia. Supraglottic airway devices were used or use was attempted in 607 cases of difficult airway management (12.4% (95%CI 11.5–13.3%)), and were successful in 395 (65.1% (95%CI 61.2–68.8%)) cases. In ‘cannot intubate, cannot facemask ventilate’ situations, supraglottic airway devices were used in 86 (18.9% (95%CI 15.6–22.8%)) of 455 records and were successful in 54 (62.8% (95%CI 52.2–72.3%)) cases. We found that supraglottic airway devices are not widely used in the management of the difficult airway despite their prominent role in difficult airway management guidelines.     

LMA Supreme™ Versus Facemask Ventilation Performed by Novices: A Comparative Study in Morbidly Obese Patients Showing Difficult Ventilation Predictors

Background

We designed a study to compare ventilation characteristics performed in morbidly obese patients by medical students via the facemask to that via the LMA Supreme®.

Methods

This prospective, randomized, crossover study included 31 ASA I–III morbidly patients showing difficult mask ventilation predictors. After induction of anesthesia, ten medical students with no previous clinical experience in airway management, clinically educated to facemask ventilation maneuvers, and theoretically educated to laryngeal mask use were supervised by a senior anesthesiologist during performance of 60 s facemask and LMA Supreme® ventilation in a randomly assigned order. Ventilation quality and difficulty were measured using an original score calculated as the sum of seven indicators (0?=?no ventilation and complications, 12?=?optimal and safe ventilation) and a visual analog scale (VAS; 0?=?no difficult–100?=?impossible), respectively. Values are presented as means (standard deviation) or medians [extremes].

Results

Mean age and body mass index of the patients were 39 years (12 years) and 44 kg m^?2 (7 kg m^?2), respectively. One patient was excluded because of ventilation difficulty experienced by the senior anesthesiologist. Medical students successfully established ventilation with the LMA Supreme® in all the 30 patients after a delay of 21 s (9 s) compared to 34 s (14 s) with the facemask (P?P?Conclusions We showed that the LMA Supreme? placed in novice hands systematically promoted easier ventilation of better quality than the facemask in morbidly obese patients showing difficult mask ventilation predictors. Our data suggest that the LMA Supreme? could be considered as a standard airway management tool for both elective and rescue airway management of morbidly obese patients.     

Airway management during gynaecological laparoscopy — is it safe to use the laryngeal mask airway?

The safety of anaesthesia for gynaecological laparoscopy probably depends largely on short operative time, close intraoperative monitoring and the experience of both anaesthetist and surgeon. However, there is debate over the most suitable mode of ventilation and form of airway management. It is argued that hypoventilation and the risk of regurgitation make intubation and ventilation mandatory, and yet spontaneous ventilation with a facemask appears to be a safe technique with reduced minor morbidity. The laryngeal mask airway (LMA) has added a new dimension to the debate since it offers potential advantages over both the tracheal tube and the facemask. The aim of this review is to analyse the physiological and clinical evidence supporting the mode of ventilation and airway management during gynaecological laparoscopy and to discuss these issues in the context of the LMA. We conclude that the physiological and clinical data available to determine the suitability of the LMA is inadequate. Further proof is required before widespread adoption of these techniques. It is possible that advances in LMA design may extend the suitability of the LMA for gynaecological laparoscopy.     

A systematic review (meta-analysis) of the accuracy of the Mallampati tests to predict the difficult airway

The original and modified Mallampati tests are commonly used to predict the difficult airway, but there is controversy regarding their accuracy. We searched MEDLINE and other databases for prospective studies of patients undergoing general anesthesia in which the results of a preoperative Mallampati test were compared with the subsequent rate of difficult airway (difficult laryngoscopy, difficult intubation, or difficult ventilation as reference tests). Forty-two studies enrolling 34,513 patients were included. The definitions of the reference tests varied widely. For predicting difficult laryngoscopy, both versions of the Mallampati test had good accuracy (area under the summary receiver operating characteristic (sROC) curve = 0.89 +/- 0.05 and 0.78 +/- 0.05, respectively). For predicting difficult intubation, the modified Mallampati test had good accuracy (area under the sROC curve = 0.83 +/- 0.03) whereas the original Mallampati test was poor (area under the sROC curve = 0.58 +/- 0.12). The Mallampati tests were poor at identifying difficult mask ventilation. Publication bias was not detected. Used alone, the Mallampati tests have limited accuracy for predicting the difficult airway and thus are not useful screening tests.     

Aerosol precautions and airway complications: a national prospective multicentre cohort study

The perceived risk of transmission of aerosolised viral particles from patients to airway practitioners during the COVID-19 pandemic led to the widespread use of aerosol precautions, including personal protective equipment and modifications to anaesthetic technique. The risk of these aerosol precautions on peri-operative airway complications has not been assessed outside of simulation studies. This prospective, national, multicentre cohort study aimed to quantify this risk. Adult patients undergoing general anaesthesia for elective or emergency procedures over a 96-hour period were included. Data collected included use of aerosol precautions by the airway practitioner, airway complications and potential confounding variables. Mixed-effects logistic regression was used to assess the risk of individual aerosol precautions on overall and specific airway complications. Data from 5905 patients from 70 hospital sites were included. The rate of airway complications was 10.0% (95%CI 9.2–10.8%). Use of filtering facepiece class 2 or class 3 respirators was associated with an increased risk of airway complications (odds ratio 1.38, 95%CI 1.04–1.83), predominantly due to an association with difficult facemask ventilation (odds ratio 1.68, 95%CI 1.09–2.61) and desaturation on pulse oximetry (odds ratio 2.39, 95%CI 1.26–4.54). Use of goggles, powered air-purifying respirators, long-sleeved gowns, double gloves and videolaryngoscopy were not associated with any alteration in the risk of airway complications. Overall, the use of filtering facepiece class 2 or class 3 respirators was associated with an increased risk of airway complications, but most aerosol precautions used during the COVID-19 pandemic were not.     

Archie Brain: celebrating 30 years of development in laryngeal mask airways

The practice of anaesthesia was revolutionised by the ideas of Archie Brain. The routine use of a facemask to manage the airway was not a hands‐free technique, despite the development of various harnesses, and made adequate record‐keeping difficult. The tracheal tube was associated with some morbidity, which some felt was unsuitable for day surgery. Brain developed an airway management device that was less stressful to the patient than tracheal intubation, and was, however, as safe as using a facemask and airway. Brain also hoped his device would function for cases where mask ventilation was particularly difficult and thus give anaesthetists a safer alternative to a complex intubation, especially in emergency scenarios.     

Use of continuous positive airway pressure during spinal anaesthesia in a patient with severe chronic obstructive pulmonary disease

We report the case of a patient with severe chronic obstructive pulmonary disease who underwent local resection of a carcinoma of the rectum under spinal anaesthesia. Although the patient was keen to avoid general anaesthesia and to have the operation under a spinal anaesthetic, pre-operative assessment showed that he could not lie flat. As the surgical procedure required the patient to be in the lithotomy position, ideally with a head-down tilt, it was hoped that continuous positive airway pressure with a facemask during spinal anaesthesia might help him to tolerate the position comfortably. Continuous positive airway pressure at 7.5 cmH(2)O was successfully used to facilitate breathing during surgery under spinal anaesthesia. A combination of regional anaesthesia and continuous positive airway pressure via a facemask is easy to use and may be a useful option in the management of these challenging patients.     

A simple model to predict coronary disease in patients undergoing operation for mitral regurgitation

BACKGROUND: Coexistent coronary disease can be identified in a third of patients with mitral valve disease. This study aims to evaluate candidate selection strategy using risk factor identification and logistic regression and to develop an additive model for the prediction of coexistent coronary disease. METHODS: The sample is a consecutive series of patients who had mitral repair from 1987 to 1999. Sensitivities and specificities were calculated for each risk factor. Variables for prediction of coronary disease were entered into a univariate analysis, and predictors were entered into a forward and backward stepwise multivariate logistic regression model to form a predictive score. An additive model was derived from transformation of the logistic model. Receiver operating characteristic curves were used to compare discrimination and precision quantified by the Hosmer-Lemeshow statistic. RESULTS: The American Heart Association and American College of Cardiology risk factor identification selection criteria for the 359 patients who had screening coronary angiography yielded 100% sensitivity and 1% specificity. Risk prediction with our logistic model produced a receiver operating characteristic curve area of 0.91 and Hosmer-Lemeshow score of 3.4 (p = 0.9). Similar discriminating ability for our patients was achieved by the Cleveland Clinic logistic model (receiver operator characteristic curve area of 0.79; Hosmer-Lemeshow score of 12; p = 0.1). Our five-item additive model produced receiver operating characteristic curve area of 0.91 and Hosmer-Lemeshow score of 3.81 (p = 0.80). CONCLUSIONS: Simple risk factor identification has excellent sensitivity but is limited by specificity. Logistic regression modeling is an accurate risk prediction method but is difficult to apply at the bedside. Simplicity and accuracy may be achieved by the logistic regression-derived simple additive model.     

Facemask ventilation and vocal cord angle following neuromuscular blockade: a prospective observational study#

Numerous studies support the idea that neuromuscular blockade facilitates facemask ventilation after induction of anaesthesia. Although improved airway patency or pulmonary compliance and a resolution of laryngospasm have been suggested as possible causes, the exact mechanism remains unclear. We aimed to assess whether neuromuscular blockade improves facemask ventilation and to clarify whether this phenomenon is associated with the vocal cord angle. This prospective observational study included patients aged between 20 and 65 years scheduled for elective surgery under general anaesthesia. After induction of anaesthesia, patients' lungs were ventilated with pressure-controlled ventilation using a facemask. During facemask ventilation, a flexible bronchoscope was inserted through a self-sealing diaphragm at the elbow connector attached to the facemask and breathing circuit and positioned to allow a continuous view of the vocal cords. The mean tidal volume and vocal cord angle were measured before and after administration of neuromuscular blocking drugs. Of 108 patients, 100 completed the study. Mean (SD) tidal volume ((11.0 (3.9) ml.kg^-1 vs. 13.6 (2.6) ml.kg^-1; p < 0.001) and mean (SD) vocal cord angle (17° (10°) vs. 26° (5°); p < 0.001) increased significantly after neuromuscular blockade. The proportional increase in mean tidal volume after neuromuscular blockade was positively correlated with vocal cord angle (Spearman's ρ = 0.803; p < 0.001). In conclusion, neuromuscular blockade facilitated facemask ventilation, and the improvement was correlated with further opening of the vocal cords.     

Extraglottische Atemwegshilfen auf der Intensivstation

Extraglottic airway devices (EGA) are not only used in routine anaesthesia practice, they also have a distinct value for in-hospital and out-of-hospital difficult airway management. In the environment of the intensive care unit (ICU) EGA are not used on a regular basis. However, expertise and knowledge regarding EGA coming from the operating theatre or the out-of-hospital setting may also be of value for the ICU setting. This review presents the potential indications for EGA on the ICU for the management of difficult airway situations as well as during percutaneous tracheotomy. Furthermore, the possible advantages of EGA during postoperative recovery from anaesthesia as well as termination of controlled ventilation for intensive care patients are discussed.     

Optimising the unprotected airway with a prototype Jaw-Thrust-Device – a prospective randomised cross-over study

Despite being a standard procedure during induction of anaesthesia, facemask ventilation can be a major challenge especially for inexperienced anaesthetists. We manufactured a Jaw-Thrust-Device designed to keep the patient's jaws in an optimised position, and thus to maintain the airway in a permanently patent state. Using a cross over design, we compared the influence of using the Esmarch manoeuvre (bimanual jaw-thrust), a nasopharyngeal airway, an oropharyngeal airway, or the Jaw-Thrust-Device on airway physiology in 50 healthy adults with body mass index < 35 kg.m⁻², undergoing standard facemask ventilation for routine induction of anaesthesia. The main study endpoints were expiratory tidal volumes, airway resistances, and gas flow rates. The Jaw-Thrust-Device was more effective in increasing expiratory tidal volumes and peak inspiratory flow than a standard Esmarch manoeuvre, and was more effective than both nasopharyngeal and oropharyngeal airways in decreasing airway resistance.     

Preoperative assessment for difficult intubation in general and ENT surgery: predictive value of a clinical multivariate risk index

Several clinical multifactorial indexes have been described for predicting difficult laryngoscopy or intubation, or both, mostly in general surgery, and less frequently in ENT surgery. The objective of this study was to develop and validate a single clinical index for prediction of difficulty in tracheal intubation in both ENT and general surgery. We studied a population of 1200 consecutive ENT and general surgical patients. Clinical criteria were tested using univariate and multivariate analysis. Difficult intubation was defined as requiring unusual techniques. Logistic regression identified seven criteria as independent predictors of difficult tracheal intubation; previous history of difficult intubation; pathologies associated with difficult intubation; clinical symptoms of pathological airway; inter-incisor gap and mandible luxation; thyromental distance; head and neck movement; and Mallampati's modified test. Point values were assigned to each of these factors in proportion to regression coefficients representing the relative weight of each predictive intubation difficulty factor, the sum comprising the score. The best predictive threshold was chosen using a receiver operating characteristic curve. We then prospectively studied and validated the score in a population of 1090 consecutive ENT and general surgery patients. The sensitivity and specificity of the predictions were 94% and 96% in general surgery, 90% and 93% in non- cancer ENT surgery, and 92% and 66% in ENT cancer surgery, respectively.      

急性结石性胆囊炎腹腔镜胆囊切除术术前评分模型的建立

目的:建立急性结石性胆囊炎腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)术前评分模型,预测手术难度。方法:回顾分析2014年6月至2016年6月324例急性结石性胆囊炎患者行LC的临床资料,并根据手术时间分为容易组与困难组。应用χ~2检验对两组指标进行单因素分析;再将P<0.01的指标纳入多因素Logistic回归分析。采用多因素分析有统计学意义(P<0.05)的指标构建LC术前评分模型,并应用ROC曲线评价此模型的性能。结果:单因素分析表明,性别、胆囊炎发作时间、凝血酶原时间、中性粒细胞绝对计数、纤维蛋白原、碱性磷酸酶及胆囊壁厚度对手术时间具有影响;多因素分析表明,性别、胆囊炎发作时间、中性粒细胞绝对计数、碱性磷酸酶、纤维蛋白原及胆囊壁厚度是影响手术时间的独立危险因素。LC术前评分模型的曲线下面积为0.784。以5分为手术是否困难的临界值,其特异度为72.7,敏感度为80.6。结论:LC术前评分模型对预测LC手术难度具有较好的预测能力,可为选择合适的手术方式提供临床指导。     

The effect of a cervical collar on the tidal volume of anaesthetised adult patients

Semi-rigid cervical collars may be used to assist the stabilisation of the cervical spine during transport in patients suffering from major trauma. We have attempted to evaluate the effect of one such collar on airway patency in the presence of depressed airway reflexes. Thirty-eight patients undergoing anaesthesia via facemask with spontaneous ventilation were studied. Tidal volume was measured with the airway in three different positions, both with and without a collar. The collar made no statistically significant difference to tidal volume in any position. Changing support of the airway increased tidal volume both with and without the collar. Patients fitted with an incorrectly sized collar may develop upper airway obstruction in the presence of impaired consciousness. Experience should be gained in the correct fitting of semi-rigid collars.     

Respiratory complications associated with tracheal intubation and extubation

We conducted a prospective survey on the incidence of respiratory complications associated with tracheal intubation and extubation in 1005 patients who underwent elective general anaesthesia over a 4-month period. During induction of anaesthesia, respiratory complications occurred in 46 patients (4.6%; 95% confidence limits (CL): 3.3, 5.9%). The common complications were coughing (1.5%) and difficult ventilation through a facemask (1.4%). Tracheal intubation was difficult in eight patients (0.8%). Complications occurred immediately after tracheal extubation in 127 patients (12.6%; 95% CL: 10.6, 14.7) and in the recovery room in 95 patients (9.5%; 95% CL: 7.6, 11.3%). The common complications immediately after extubation were coughing (6.6%) and oxygen desaturation (SaO2 < 90%) (2.4%), and in the recovery room, airway obstruction (3.8%) and coughing (3.1%). The incidence of complications was significantly higher immediately after tracheal extubation than during induction of anaesthesia (P << 0.001). Even when all incidents of coughing that occurred after tracheal extubation were disregarded as a complication, the overall incidence was still higher immediately after extubation (7.4%) than during induction of anaesthesia (P < 0.01). We conclude that the incidence of respiratory complications associated with tracheal extubation may be higher than that during tracheal intubation.      

Potential roles of preoperative upper airway radiographs in planning of perioperative airway management

Majority of severe anesthetic complications result from airway difficulties. Among the airway difficulties, difficult mask ventilation is a key critical condition in the currently proposed difficult airway algorithms, and is probably the most life-threatening event. Presence of severe obstructive sleep apnea may indicate potential difficulty in mask ventilation during anesthesia induction. Lateral neck radiographs for patients with suspected airway difficulties may provide useful information for identification of potential patients with difficult mask ventilation. Among the parameters measured by the radiographs, I recommend anesthesiologists to measure distance between the hyoid bone and mandibular plane, which possibly reflects anatomical balance of the upper airway maintenance.