Implementing human factors in anaesthesia: guidance for clinicians, departments and hospitals: Guidelines from the Difficult Airway Society and the Association of Anaesthetists: Guidelines from the Difficult Airway Society and the Association of Anaesthetists.

Human factors is an evidence-based scientific discipline used in safety critical industries to improve safety and worker well-being. The implementation of human factors strategies in anaesthesia has the potential to reduce the reliance on exceptional personal and team performance to provide safe and high-quality patient care. To encourage the adoption of human factors science in anaesthesia, the Difficult Airway Society and the Association of Anaesthetists established a Working Party, including anaesthetists and operating theatre team members with human factors expertise and/or interest, plus a human factors scientist, an industrial psychologist and an experimental psychologist/implementation scientist. A three-stage Delphi process was used to formulate a set of 12 recommendations: these are described using a 'hierarchy of controls' model and classified into design, barriers, mitigations and education and training strategies. Although most anaesthetic knowledge of human factors concerns non-technical skills, such as teamwork and communication, human factors is a broad-based scientific discipline with many other additional aspects that are just as important. Indeed, the human factors strategies most likely to have the greatest impact are those related to the design of safe working environments, equipment and systems. While our recommendations are primarily provided for anaesthetists and the teams they work with, there are likely to be lessons for others working in healthcare beyond the speciality of anaesthesia.

Human factors in anaesthesia: a narrative review.

Healthcare relies on high levels of human performance, as described by the 'human as the hero' concept. However, human performance varies and is recognised to fall in high-pressure situations, meaning that it is not a reliable method of ensuring safety. Other safety-critical industries embed human factors principles into all aspects of their organisations to improve safety and reduce reliance on exceptional human performance; there is potential to do the same in anaesthesia. Human factors is a broad-based scientific discipline which aims to make it as easy as possible for workers to do things correctly. The human factors strategies most likely to be effective are those which 'design out' the chance of an error or adverse event occurring. When errors or adverse events do happen, barriers are in place to trap them and reduce the risk of progression to patient and/or worker harm. If errors or adverse events are not trapped by these barriers, mitigations are in place to minimise the consequences. Non-technical skills form an important part of human factors barriers and mitigation strategies and include: situation awareness; decision-making; task management; and team working. Human factors principles are not a substitute for proper investment and appropriate staffing levels. Although applying human factors science has the potential to save money in the long term, its proper implementation may require investment before reward can be reaped. This narrative review describes what is known about human factors in anaesthesia to date.

A randomised crossover trial comparing the i-gel supraglottic airway and classic laryngeal mask airway.

In a randomised cross-over study, we compared the performance of the single use i-gel supraglottic airway and reusable classic laryngeal mask airway (cLMA) in 50 healthy anaesthetised patients who were breathing spontaneously. Primary outcome was successful insertion at first attempt. Secondary outcomes included overall insertion success rate, ease of insertion, leak pressure and fibreoptic position. Success rate for insertion at the first attempt was significantly different (54% with i-gel vs 86% with cLMA; p = 0.001). Overall success after two attempts (when the anaesthetist was allowed to change the size of the device) improved to 84% with i-gel vs 92% with cLMA; p = 0.22. In 14 patients, the i-gel when used first needed to be replaced with a larger size. Leak pressure was higher for the i-gel (median [IQR] 20 [14-24] cm H(2)O than the cLMA 17 [12-22] cm H(2)O; p = 0.023). The fibreoptic view through the device was significantly better with the i-gel than the cLMA, which was statistically significant (p = 0.03). We conclude that, with its current sizing recommendations, the i-gel is not an acceptable alternative to cLMA. However because of the significantly improved success rate after a larger sized i-gel was used, we recommend the manufacturer to review the sizing guidelines to improve the success rate.

Subglottic stenosis in pregnancy.

Subglottic stenosis (SGS) in pregnancy is rare but may cause a potentially life-threatening delivery and is a challenge to the anaesthetist and the obstetrician. Clinical signs of SGS may not be obvious and the diagnosis can be difficult. Patients usually present with shortness of breath rather than stridor. Many patients have been wrongly diagnosed with asthma and recurrent bronchitis before subsequent discovery of a SGS. Early diagnosis of SGS and multidisciplinary input is important in managing these patients. We present a case of a pregnant woman with a history of Wegener's granulomatosis and the successful multidisciplinary management of her SGS.

Use of the laryngeal mask for closed circuit anesthesia.

We examined whether the laryngeal mask could be used effectively in 70 patients breathings spontaneously during closed-circuit anesthesia. After administration of oxygen 101.min-1, anesthesia was induced and the laryngeal mask inserted. After 6 min of denitrogenation (3.51.min-1 nitrous oxide and 1.51.min-1 oxygen), the fresh-gas flow was decreased to the minimum required to maintain refilling of a ventilator bellows (Carden Ventmasta); nitrous oxide was turned off. A vaporiser outside the breathing system was set either by observing an end-tidal agent monitor or at 3-5 times greater than the required end-tidal concentration. The total fresh gas flow, hemodynamics and respiratory variables were monitored. Several types of operations were performed and lasted 9-126 min (mean 37 min). The average total fresh gas flow during the closed circuit period was 340 ml.min-1 (range 200-500 ml.min-1). Blood pressure, heart rate and respiration were stable throughout anesthesia and there were no major side effects attributable to the technique. We believe that closed-circuit anesthesia in patients breathing spontaneously through the laryngeal mask, as described here, can be used safely, conveniently and effectively. This technique is suitable for surgical operations of short duration.

Evaluation of the Basic Airway Model, a novel mask ventilation training manikin.

The Basic Airway Model is an airway manikin designed for training in mask ventilation. We investigated the ability of the Basic Airway Model to provide varying levels of difficulty for mask ventilation. Volunteers with three levels of experience (novice, intermediate and expert) attempted to ventilate the manikin at three levels of difficulty: easy, intermediate and difficult. The distribution of frequencies of successful ventilation by different groups at the three levels of difficulty were statistically significant (p < 0.0001). The median (IQR (range)) degree of difficulty was 3 (2-5 (1-7)), 4 (3-5.3 (2-7)) and 6 (5-7 (3-9)) for easy, intermediate and difficult settings, respectively. We conclude that the Basic Airway Model can provide different levels of difficulty for mask ventilation training.

Comparison of face masks in the bag-mask ventilation of a manikin.

BACKGROUND AND OBJECTIVE: We conducted a study investigating the effectiveness of four face mask designs in the bag-mask ventilation of a special manikin adapted to simulate a difficult airway. METHODS: Forty-eight anaesthetists volunteered to bag-mask ventilate the manikin for 3 min with four different face masks. The primary outcome of the study was to calculate mean percentage leak from the face masks over 3 min. Anaesthetists were also asked to rate the face masks using a visual analogue score. RESULTS: The single-use scented intersurgical face mask had the lowest mean leak (20%). This was significantly lower than the mean leak from the single-use, cushioned 7,000 series Air Safety Ltd. face mask (24%) and the reusable silicone Laerdal face mask (27%) but not significantly lower than the mean leak from the reusable anatomical intersurgical face mask (23%). CONCLUSIONS: There was a large variation in both performance and satisfaction between anaesthetists with each design. This highlights the importance of having a variety of face masks available for emergency use.

A comparison of direct laryngoscopy and jaw thrust to aid fibreoptic intubation.

We compared two manoeuvres, jaw thrust and laryngoscopy, to open the airway during fibreoptic intubation in 50 patients after induction of anaesthesia in a crossover study. Patients were randomly allocated to receive either jaw thrust or conventional Macintosh laryngoscopy first. Airway clearance was assessed at both the soft palate and the epiglottis. Direct laryngoscopy provided significantly better airway clearance at the level of the soft palate than jaw thrust (44 (88%) vs 31 (62%), respectively; p = 0.002). At the level of the larynx, airway clearance was equally good in both groups (45 (90%) vs 46 (92%), respectively; p = 0.56). The times to view the larynx (median (interquartile range [range]) 4 (3-5 [2-35]) s vs 3 (3-4 [2-8]) s, respectively) and intubation time (20 (17-23 [11-83]) s vs 18 (15-20 [11-28]) s, respectively) were also similar.

Thyroplasty under general anesthesia using a laryngeal mask airway and fibreoptic bronchoscope.

PURPOSE: To report the management of a patient, with unilateral vocal cord paralysis, undergoing thyroplasty, under general anesthesia. CLINICAL FEATURES: A 25-yr-old man developed hoarseness and occasional episodes of pulmonary aspiration, caused by unilateral vocal cord paralysis. He was scheduled for thyroplasty, in an attempt to ease phonation and to decrease or prevent further episodes of pulmonary aspiration. He refused local anesthesia with sedation and it was therefore decided to attempt the procedure under general anesthesia. The paralysed vocal cord was displaced inwards by a wedge inserted through a window in the thyroid cartilage. We assessed the ideal position of the wedge by using a fibreoptic bronchoscope and laryngeal mask airway during general anesthesia, instead of phonation. CONCLUSION: We describe the successful use of a general anesthetic for a thyroplasty, a procedure normally done under local anesthesia with or without sedation, in a patient who was keen to have surgery, but who refused local anesthesia with sedation.

Topical ibuprofen for skin analgesia prior to venepuncture.

The analgesic effect of topical ibuprofen was investigated in ten volunteers. There were no significant differences in visual analogue scale pain scores for pinprick after 15 and 60 min of application of ibuprofen, placebo and EMLA cream. Comparison of visual analogue scale scores for venous cannulation after similar durations of ibuprofen and EMLA creams found significantly (p < 0.014) lower scores for EMLA at 60 min. We do not consider ibuprofen cream to be clinically useful for venous cannulation.

Effects of magnesium sulphate on suxamethonium-induced complications during rapid-sequence induction of anaesthesia.

Twenty patients were studied in a double-blind manner to investigate whether magnesium sulphate, when given during a rapid-sequence induction of anaesthesia, lessens the side effects caused by suxamethonium. Patients were randomly allocated to two groups; equal volumes of either magnesium sulphate (40 mg.kg-1) or saline were given during rapid-sequence induction of anaesthesia, after thiopentone but before the administration of suxamethonium (1.5 mg.kg-1). The changes in the serum potassium concentration, the degree of muscle fasciculations and the presence of postoperative myalgia were recorded. The mean serum potassium concentration increased by 0.08 mmol.l-1 in the magnesium group and by 0.1 mmol.l-1 in the control group at 2 min after injection of suxamethonium; in neither group was there a significant increase from baseline values. The systolic blood pressure and heart rate increased in both groups after tracheal intubation. The incidence of fasciculations was significantly lower in the magnesium group. Magnesium did not clinically prolong muscle relaxation. There was no difference between the groups in the incidence of myalgia after surgery (one patient in each group). Since no significant increase in the serum potassium concentration was demonstrated, no assessment could be made of the effect of magnesium sulphate on the serum potassium concentration after administration of suxamethonium.

An evaluation of the modified Airway Management Device.

We evaluated the modified Airway Management Device (AMDTM) in 60 spontaneously breathing anaesthetised patients. The insertion and removal of the device was very easy and atraumatic. The airway was secured on the first attempt in 41 patients (70%; 95% CI 57-80%). The most important problem was loss of airway, which occurred in 11 patients (19%; 11-30%) during maintenance of anaesthesia. The AMD was dislodged during maintenance in one patient. There was a loss of the airway in 12 patients (20%; 12-31%); in 10, it was maintained with simple airway manoeuvres or a laryngeal mask airway and tracheal intubation was required in two patients. Ten of these patients were male and two were female; the failure rate was 33% (12-31%) among the male patients and 6% (2-22%) among the female patients. The cuff volumes ranged from 4 ml to 80 ml and cuff pressures from 6 cm H2O to 92 cm H2O. Blood was seen on removal in three patients (6%; 2-16%) and nine patients (18%; 10-30%) experienced sore throat after removal of the device.