Comparison of the reinforced laryngeal mask airway and tracheal intubation for nasal surgery

Airway maintenance and protection during anaesthesia and recovery provided by the reinforced laryngeal mask airway was compared with the sequential use of a tracheal tube followed by the Guedel airway in 66 patients having anaesthesia for nasal surgery. One patient was withdrawn from the laryngeal mask group because the airway was difficult to position. All patients had an oropharyngeal pack inserted and Moffett's solution instilled into the nasal cavities. At the end of surgery the nasal cavities were packed. During operation airway maintenance was good and airway protection was equally effective in both groups. Contamination of the lower airway occurred in only five patients. During recovery from anaesthesia the laryngeal mask and Guedel airway were well tolerated by most patients, but only the mask laryngeal provided an unobstructed airway in all patients. The laryngeal mask protects the larynx from contamination during and after operation until the return of the patient's own protective reflexes.     

Anaesthetic management in asthma

Anaesthetic management in asthmatic patients has been focused on avoiding bronchoconstriction and inducing bronchodilation. However, the definition of asthma has changed over the past decade. Asthma has been defined as a clinical syndrome characterized by an inflammatory process that extends beyond the central airways to the distal airways and lung parenchyma. With this concept in mind, and knowing that asthma is a common disorder with increasing prevalence rates and severity worldwide, a rational choice of anaesthetic agents and procedures is mandatory. Thus, we pursued an update on the pharmacologic and technical anaesthetic approach for the asthmatic patient. When feasible, regional anaesthesia should be preferred because it reduces airway irritation and postoperative complications. If general anaesthesia is unavoidable, a laryngeal mask airway is safer than endotracheal intubation. Lidocaine inhalation, alone or combined with albuterol, minimizes histamine-induced bronchoconstriction. Propofol and ketamine inhibit bronchoconstriction, decreasing the risk of bronchospasm during anaesthesia induction. Propofol yields central airway dilation and is more reliable than etomidate or thiopental. Halothane, enflurane, and isoflurane are potent bronchodilators and can be helpful even in status asthmaticus. Sevoflurane has shown controversial results in asthmatic patients. Vecuronium, rocuronium, cisatracurium, and pancuronium do not induce bronchospasm, while atracurium and mivacurium can dose-dependently release histamine and should be cautiously administered in those patients. Further knowledge about the sites of action of anaesthetic agents in the lung, allied with our understanding of asthma pathophysiology, will establish the best anaesthetic approach for people with asthma.     

Thyroplasty under total intravenous anaesthesia with intermittent positive pressure ventilation

BACKGROUND AND OBJECTIVES: Medialization thyroplasty is a surgical technique for improving voice quality, cough effort and laryngeal competence in patients with unilateral vocal fold paralysis. Precision surgery is enabled by operating under total intravenous anaesthesia with controlled ventilation and by using a laryngoscopic video-assisted technique. The anaesthetic challenge is to manage the shared airway with the surgeon, provide a stable operative field and ensure patient safety throughout the procedure. The objective of this case series was to evaluate the use of a modified general anaesthetic technique using the laryngeal mask airway, total intravenous anaesthesia with controlled ventilation. METHODS AND RESULTS: In all, 29 patients underwent medialization thyroplasty using a disposable laryngeal mask airway, total intravenous anaesthesia and controlled ventilation. Standard anaesthetic monitoring including capnography was used intraoperatively. Total intravenous anaesthesia was achieved using effect site target-controlled infusions of propofol and remifentanil. CONCLUSIONS: The technique proved safe with stable haemodynamic observations and only two minor complications. It also provided the surgeon with stable view of the vocal folds in order to perform this precision surgery under an operating microscope.     

Removal of the laryngeal mask airway: factors affecting the incidence of post-operative adverse respiratory events in 300 patients

The purpose of this study is to compare the incidence of undesirable respiratory events when the laryngeal mask airway is either removed from patients who are fully awake or from patients who are deeply anaesthetized. Three-hundred patients aged 1.5-81 years were randomly assigned to have their laryngeal mask airway removed either when deeply anaesthetized or after airway reflexes had returned. The occurrence of adverse respiratory events (coughing, oxygen desaturation and airway obstruction) was recorded. Airway obstruction after laryngeal mask airway removal was evident in 20% of patients in the deep anaesthesia group and in 8% of patients in the awake group (P = 0.007). In spite of this finding, oxygen desaturation in children of less than 6 years of age (SaO2 < 96%) occurred most frequently after awake removal (31.3%) compared with deep anaesthesia removal (4.5%) (P = 0.023).     

The reinforced laryngeal mask in paediatric outpatient dental surgery

One hundred and twenty ASA I and II grade children aged 2-9 years scheduled for outpatient dental extractions under general anaesthesia were studied. They were allocated randomly to one of three groups for airway management: group R had anaesthesia with a reinforced laryngeal mask airway, group L with a standard laryngeal mask airway and group N with a nasal mask. Anaesthesia was induced in all children using halothane in 50% nitrous oxide with oxygen and maintained on halothane in 67% nitrous oxide with oxygen. An Ayre's T-piece with Jackson-Rees modification was used. The incidence of airway obstruction was significantly lower and surgical access significantly better with the reinforced laryngeal mask airway when compared with the standard laryngeal mask airway. However, the reinforced laryngeal mask airway was significantly more difficult to insert when compared with the standard laryngeal mask airway. On comparing the reinforced laryngeal mask airway with the nasal mask, there were significantly fewer episodes of airway obstruction, better oxygen saturation, less increase in heart rate and fewer arrhythmias in the reinforced laryngeal mask airway group. Total time for the procedures was the same for all three groups. Thus, the reinforced laryngeal mask airway was found to be a favourable alternative to the standard laryngeal mask airway and nasal mask for paediatric outpatient dental extractions.     

An evaluation of the laryngeal mask airway during routine paediatric anaesthesia

During a six week period, all anaesthetists at the Royal Hospital for Sick Children, Glasgow were asked to complete a questionnaire whenever a laryngeal mask airway (LMA) was used. Seniority of anaesthetist, age of patient, anaesthetic technique, technique of LMA insertion, ease of LMA insertion, and any problems encountered either during LMA insertion, or during induction, maintenance, and recovery from anaesthesia were documented. Complete data were obtained from 211 patients aged 5 weeks to 15 years. Ninety-six children were anaesthetized by consultant paediatric anaesthetists, and 115 by trainees. LMA insertion was successful at the first attempt in 86% of all cases, achieved with some difficulty in 11% of cases, and failed or its use was abandoned in 6 cases (3%). Difficulties other than with LMA placement per se occurred in 11% of cases during induction of anaesthesia. Seniority of anaesthetist and choice of anaesthetic agent influenced neither the success rate of insertion nor the frequency of other difficulties encountered during induction of anaesthesia. Significantly fewer problems were encountered at LMA removal if this was done during deep anaesthesia compared with removal when protective reflexes were present (P < 0.05).     

Tracheal intubation through the intubating laryngeal mask in patients with unstable necks

BACKGROUND: In patients with unstable necks, the neck should be stabilized during induction of anaesthesia, but this may make tracheal intubation difficult. Awake intubation may produce straining, which could be detrimental to the unstable neck. METHODS: We studied 20 patients with unstable necks to examine the efficacy of insertion of the intubating laryngeal mask under conscious sedation (to minimize the possibility of losing a patent airway and to facilitate fibrescope-aided intubation) followed by tracheal intubation through the laryngeal mask after induction of anaesthesia (to reduce stress response to intubation). After the patient had been sedated with midazolam (up to 5 mg) and fentanyl (up to 100 microg), the intubating laryngeal mask was inserted. General anaesthesia was then induced with sevoflurane and tracheal intubation attempted. RESULTS: In all patients, tracheal intubation through the laryngeal mask succeeded without airway obstruction. Neither insertion of the mask under conscious sedation nor tracheal intubation after induction of anaesthesia caused straining, and only two patients moved upper extremities at intubation. Insertion of the laryngeal mask did not significantly alter blood pressure or heart rate. Tracheal intubation significantly increased blood pressure and heart rate, but the increase was considered to be small. CONCLUSIONS: In the patient with an unstable neck with a low risk of pulmonary aspiration, insertion of the intubating laryngeal mask while the patient is sedated may minimize difficulty in obtaining a patent airway before tracheal intubation and may facilitate a fibrescope-aided tracheal intubation; subsequent induction of anaesthesia before tracheal intubation may minimize stress response to intubation.     

Airway protection by the laryngeal mask

Methylene blue was placed in the pharynx of 64 patients undergoing anaesthesia with the laryngeal mask. No leak of dye into the larynx was detected on fibreoptic inspection of the inside of the mask in any subject. The use of the laryngeal mask as a means of protecting the airway during procedures such as minor nasal operations is therefore supported.     

Midazolam reduces the dose of propofol required for induction of anaesthesia and laryngeal mask airway insertion

BACKGROUND AND OBJECTIVE: Insertion of the laryngeal mask airway in the anaesthetized patient can sometimes be difficult and propofol has been advocated as the anaesthetic induction agent of choice because of its depressant effect on laryngeal reflexes compared with other intravenous anaesthetics. However, when used as the sole induction agent, relatively large doses of propofol are required to achieve successful laryngeal mask insertion. This has cost implications and may produce unwanted cardiorespiratory depression. METHODS: One hundred and forty-two patients were randomized to receive either: fentanyl 1 microg kg(-1) and lidocaine 1.5 mg kg(-1) (group 1), or fentanyl 1 microg kg(-1) and midazolam 0.04 mg kg(-1) (group 2), or fentanyl 1 microg kg(-1), midazolam 0.04 mg kg(-1) and lidocaine 1.5 mg kg(-1) (group 3) or fentanyl 1 microg kg(-1) (group 4) 2 min before induction of anaesthesia. Anaesthesia was established with propofol infused at 33.3 mg min(-1). RESULTS: Patients who were given midazolam required significantly less propofol to achieve satisfactory laryngeal mask insertion, median propofol doses: group 1, 1.63 mg kg(-1); group 2, 1.16 mg kg(-1); group 3, 1.01 mg kg(-1); group 4, 1.9 mg kg(-1), P < 0.0001 (analysis of variance). Patients given midazolam reported less pain on injection with propofol 13% and 3% groups (2 and 3) compared with 37.5% and 77% (groups 1 and 4) P = 0.002 (chi(2)). CONCLUSIONS: Midazolam reduces the dose of propofol required for induction of anaesthesia and successful insertion of the laryngeal mask airway. There was no clinical benefit to be gained from the addition of lidocaine.     

The laryngeal mask airway: its features,effects and role

The laryngeal mask airway was designed as a new concept in airway management and has been gaining a firm position in anaesthetic practice. Numerous articles and letters about the device have been published in the last decade, but few large controlled trials have been performed. Despite widespread use, the definitive role of the laryngeal mask has yet to be established. In some situations, such as after failed tracheal intubation or in anaesthesia for patients undergoing laparoscopic or oral surgery, its use is controversial. There are a number of unresolved issues, for example the effect of the laryngeal mask on regurgitation and whether or not cricoid pressure prevents placement of the mask. We review the techniques of insertion, details of misplacement, and complications associated with the use of the laryngeal mask. We discuss the features and physiological effects of the device, including the changes in intra-cuff pressure during anaesthesia and effects on blood pressure, heart rate and intra-ocular pressure. We then attempt to clarify the role of the laryngeal mask in airway management during anaesthesia, based on the current knowledge, by discussing the advantages and disadvantages as well as the indications and contraindications of its use. Lastly we describe the use of the laryngeal mask in circumstances other than airway maintenance during anaesthesia: fibreoptic bronchoscopy, tracheal intubation through the mask and its use in cardiopulmonary resuscitation.     

A randomised trial comparing the laryngeal mask airway Supreme™ with the laryngeal mask airway Unique™ in children

We conducted a randomised controlled trial comparing the laryngeal mask airway Supreme^? with the laryngeal mask airway Unique^? in children. Fifty children presenting for elective surgery were randomly assigned to receive either the laryngeal mask airway Supreme or laryngeal mask airway Unique. The outcomes measured were airway leak pressure, ease and time for insertion, insertion success rate, fibreoptic examination, incidence of gastric insufflation, ease of gastric tube placement through the laryngeal mask airway Supreme, quality of airway during anaesthetic maintenance and complications. Median (IQR [range]) time to successful device placement was shorter with the laryngeal mask airway Unique, 14.5 [13.5–16.3 (10.0–23.6)] s than with the laryngeal mask airway Supreme, 17.4 [14.8–19.8 (11.5–29.2)] s; p = 0.007. Median (IQR [range]) airway leak pressures for the laryngeal mask airway Supreme and laryngeal mask airway Unique were 20 [16–21 (12–22)] cmH₂O and 15 [14–18 (10–24)] cmH₂O, respectively (p = 0.001). The incidence of gastric insufflation was lower with the laryngeal mask airway Supreme (zero vs six patients), p = 0.01. In conclusion, the laryngeal mask airway Supreme performed as well as the laryngeal mask airway Unique and is a useful alternative for airway maintenance, particularly in children who require evacuation of gastric contents during anaesthesia.     

General anaesthesia for dentistry

Dental anaesthesia developed down a different pathway from the rest of anaesthesia. Techniques such as nasal mask anaesthesia in the sitting position were specific to dental surgery, which took place largely outside hospital in dental clinics. Now dental anaesthesia is confined to locations within the aegis of a hospital and anaesthetic techniques are similar to those in other surgical specialties. Dental surgery consists of extractions and conservation. Short procedures for the extraction of teeth may still be carried out using a nasal mask, but more difficult extractions and conservation procedures are best done with a laryngeal mask or endotracheal tube. Close liaison with the dental surgeon is imperative in the planning of the anaesthetic technique. The anaesthetist must support the jaw and head in order to provide counter-pressure to help the dentist and to prevent excessive movement of the neck. Patients needing general anaesthesia include children, those with allergy to local anaesthetics, and adults with special needs who may need premedication to enable induction to take place. During the recovery phase, the airway has to be watched carefully as the potential for obstruction is great and deaths have occurred. Paracetamol is a useful analgesic for extraction of deciduous teeth, and non-steroidal analgesics are used for pain control after extraction of permanent teeth, which is more painful. In addition, local anaesthetic injections are helpful in older children.     

Sevoflurane: a comparison between vital capacity and tidal breathing techniques for the induction of anaesthesia and laryngeal mask airway placement

Sixty unpremedicated adult day-case patients were randomly assigned to either vital capacity or tidal breathing inhalational induction techniques. End points assessed included loss of eyelash reflex, time to drop a weighted syringe, time to jaw relaxation and time to the end of laryngeal mask airway insertion. Complications occurring during the induction of anaesthesia were recorded. The data show that there is no statistical or clinical difference between the two induction techniques. Patient acceptance of both techniques was similarly high. When the time taken to prime the anaesthetic breathing system is taken into consideration, the vital capacity technique is more expensive for induction of anaesthesia. These results therefore question the need for the vital capacity induction technique with sevoflurane 8%.     

Laryngeal mask and anaesthetic waste gas exposure

In recent years there has been a growing awareness of the possible hazards caused by anaesthetic gases in operating theatres. The laryngeal mask airway provides an alternative both to tracheal intubation and the face mask although the implications for operating theatre contamination have not been quantified. This paper describes the incidence and magnitude of exposure of theatre personnel to waste anaesthetic gases during laryngeal mask airway anaesthesia. The leakage of anaesthetic gases to the anaesthetist's breathing zone was monitored using a Bruel & Kjaer Multi Gas Monitor, Type 1302 during 50 general anaesthetics employing either spontaneous (n = 24) or controlled (n = 26) ventilation. All patients were anaesthetised with propofol, alfentanil and nitrous oxide. There was no statistically significant association between the amount of anaesthetic gas leakage and ventilation method. The laryngeal mask airway meets occupational safety requirements on nitrous oxide concentrations in the operating theatre environment.     

Minimal-flow anaesthesia with controlled ventilation: comparison between laryngeal mask airway and endotracheal tube.

BACKGROUND AND OBJECTIVE: Minimal- and low-flow anaesthesia (fresh gas flow below 1 L min(-1)) provide many advantages, including reduced cost, conservation of body heat and airway humidity. An airtight seal is essential between the airway device and the airway of the patient. Therefore, we investigated whether the airtight seal created by a laryngeal mask airway allows controlled ventilation of the lungs when the fresh gas flow is reduced to 0.5 L min(-1) and compared this with an endotracheal tube. METHODS: In a prospective clinical study, 207 patients were managed using a laryngeal mask or an endotracheal tube. After intravenous induction of anaesthesia and 15 min of high fresh gas flow, the flow was reduced to 0.5 L min(-1). The breathing system was monitored for airway leaks, and the patients were assessed for complications after airway removal and postoperative discomfort. RESULTS: Both the laryngeal mask and endotracheal tube allowed fresh gas flow reduction to 0.5 L min(-1) in 84.7% and 98.3% of cases respectively (small leaks: 12% laryngeal mask, 1.7% endotracheal tube). Three patients with the laryngeal mask (3.3%) had airway leaks that were too large to permit any reduction in the fresh gas flow. CONCLUSIONS: The use of the laryngeal mask airway was more likely to be associated with a gas leak than use of an endotracheal tube; however, if modern anaesthesia machines and monitors are used, in 96.7% of the patients managed with a laryngeal mask a reduction in the fresh gas flow to 0.5 L min(-1) was possible. The incidence of coughing and postoperative complaints (sore throat, swallowing problems) was higher after use of an endotracheal tube.     

Comparison of the GlideScope video laryngoscope vs. the intubating laryngeal mask for females with normal airways

BACKGROUND AND OBJECTIVE: In this randomized clinical study, we compared the intubation success rates of the intubating laryngeal mask airway with the GlideScope in patients with normal airways. The primary hypothesis was that the intubating laryngeal mask airway was equally effective as the GlideScope in terms of successful intubation times. METHODS: Sixty ASA I and II adult patients undergoing elective gynaecological surgery were randomly allocated into either the intubating laryngeal mask airway group or the GlideScope group. After a standard anaesthetic intravenous induction, orotracheal intubation was performed. Time taken for successful tracheal intubation, ease of device insertion, difficulty of tracheal intubation, manoeuvres needed to aid tracheal intubation, number of intubation attempts, haemodynamic changes every 2.5 min interval for 5 min and complications during tracheal intubation were recorded. RESULTS: Time to successful intubation was longer (mean 68.4 s +/- 23.5 vs. 35.7 s +/- 10.7; P < 0.05), mean difficulty score was higher (mean 16.7 +/- 16.3 vs. 7.3 +/- 13.1; P < 0.05) and more intubation attempts were required in the intubating laryngeal mask airway group. CONCLUSION: The GlideScope improved intubation time and difficulty score for tracheal intubation when compared with the intubating laryngeal mask airway in our patients. Blind intubation through the intubating laryngeal mask airway offers no advantages over the GlideScope in patients with normal airways. Despite its limitations, the intubating laryngeal mask airway is a valuable adjunct, especially in cases of difficult airway management when it can provide ventilation in between intubation attempts.     

Tracheal tubes for maxillofacial and dental surgery

Maxillofacial and dental surgery have developed with anaesthesia. This is because of the mutual understanding that is necessary for safe and successful surgery on the ‘shared airway’. The choice of airway management technique is influenced by patient factors, surgical requirements and anaesthetic preferences. Good communication between surgeon and anaesthetist is imperative for the safety of the patient and the smooth running of the surgery. The anaesthetic considerations include: dealing with the difficult airway; the risk of obstruction, transection, disconnection or removal of the airway intraoperatively; the risk of soiling of the airway due to bleeding and surgical debris such as tooth or bone fragments; and the potential for airway compromise postoperatively. A cuffed tracheal tube with a throat pack provides the highest level of airway protection in shared airway surgery, but may not always be the most suitable technique. A north polar nasal tube provides a secure airway and excellent surgical access for surgery on the jaws, teeth, oral cavity and neck; it also allows intermaxillary fixation (wiring of the jaws) and assessment of dental occlusion. South facing preformed oral (RAE) tubes are suitable for procedures involving the nose, upper mid face and forehead. Submental intubation provides an alternative to oral and nasal tracheal intubation and is useful in selected procedures. The laryngeal mask airway (LMA) has an important role intraoperatively and provides smooth emergence from anaesthesia. Transtracheal catheter and jet ventilation is seldom used in maxillofacial anaesthesia, but is an important rescue technique. An elective tracheostomy should be considered if significant postoperative airway compromise is anticipated and may occasionally be necessary under local anaesthesia before induction. It requires surgical expertise and carries a high incidence of morbidity. This article discusses how to select appropriate tracheal tubes for maxillofacial and dental surgery.     

Randomised double-blind comparison of fentanyl, mivacurium or placebo to facilitate laryngeal mask airway insertion

In a double-blind randomised study, we compared conditions during insertion of the laryngeal mask airway in 150 patients who received either fentanyl 1 microg.kg-1, mivacurium 0.04 mg.kg-1 or normal saline, before induction of anaesthesia with propofol 2 mg.kg-1. Insertion conditions, including mouth opening, swallowing, gagging or coughing, head or limb movement and ease of insertion, were each graded using a three-point scale. The median (interquartile range) summed insertion scores were more favourable with the use of fentanyl [8.0 (7.0-9.0)] and mivacurium [7.5 (6.8-8.3)] than with normal saline [9.0 (7.8-10.3); p < 0.01]. Fentanyl and mivacurium decreased swallowing and head or limb movement, and mivacurium improved mouth opening. Insertion conditions were similar between fentanyl and mivacurium, while both prolonged apnoea. Fentanyl and mivacurium are equally effective in facilitating insertion of the laryngeal mask airway following anaesthetic induction with propofol.     

The pressor response and laryngeal mask insertion

The pressor response associated with laryngoscopy and tracheal intubation may be harmful to certain patients. The laryngeal mask airway avoids the need for laryngoscopy and allows positive pressure ventilation of the lungs in appropriate patients. This study compared the pressor response of tracheal intubation with that of mask insertion in two groups of 24 and 23 healthy patients respectively. All patients were anaesthetised with thiopentone, nitrous oxide, enflurane and paralysed with atracurium. We have shown a similar, but attenuated pattern of response associated with mask insertion in comparison with laryngoscopy and intubation; significant differences between the groups were evident in arterial diastolic blood pressure immediately after insertion and again 2 minutes later. Use of the laryngeal mask may therefore offer some limited advantages over tracheal intubation in the anaesthetic management of patients where the avoidance of the pressor response is of particular concern.     

A comparison of laryngeal mask airway with tracheal tube for intra-ocular ophthalmic surgery

The use of the laryngeal mask was compared with tracheal intubation in 30 patients who underwent intra-ocular ophthalmic surgery and who received intravenous anaesthesia with propofol. Changes in intra-ocular pressure, heart rate and mean arterial pressure after the insertion of the laryngeal mask airway or the tracheal tube were not significantly different. However, at the end of the procedure, a significantly higher percentage of patients with a tracheal tube coughed, reacted to head movement and suffered breath-holding. In addition, significantly more patients in this group complained of a sore throat (p less than 0.05). During intravenous propofol anaesthesia, the laryngeal mask airway does not offer any advantage over tracheal intubation in the control of intra-ocular pressure for intra-ocular ophthalmic surgery. However, there were fewer complications immediately following surgery in the laryngeal mask group.