The laryngeal mask airway: clinical appraisal in 250 patients

A new maneuver for classical laryngeal mask airway insertion: Prospective randomized study

Background/Aim: Laryngeal mask airway (LMA) has been frequently used for airway management. But the satisfaction of the insertion and trauma at insertion remain problems. We present a new insertion maneuver for classical LMA (cLMA) with a partially inflated cuff and examine its success and complication rate. Methods: In 4 months, 158 patients who were classified as ASA I–III and older than 18 years old and were planned for LMA were included in this study consecutively (according to the study design, one patient was excluded during the study). Emergency cases, patients with any contraindications with LMA, patients who were expected to undergo surgery for more than 2 h, patients with preoperative respiratory tract infection or sore throat, patients undergoing oral or nasal surgery, and patients with aspirated oropharyngeal secretions after removal of LMA was excluded from the study. Age, gender, height, weight, ASA scores, comorbidities, and the duration of anesthesia and surgery of the patients were recorded. One-hundred-fifty-seven consecutive patients were randomized into two groups by a coin toss [control group (group C) and study group (group S)]. The groups were compared in terms of LMA insertion success, the number of insertion attempts, the presence of blood on the LMA or in secretions, and postoperative sore throat. Classical Laryngeal Mask Airway was inserted with Brain’s standard technique in group C and with the new technique in group S. In the new technique, the head and neck of the patient were supported in a straight position, the mouth was opened, cLMA was held with a dominant hand from the tube part and inserted until the tip touches to the oropharynx. The index finger of the non-dominant hand was inserted into the mouth to pass by the cLMA and reach the tip of the cLMA. The tip of cLMA was directed to the caudal by the index finger. Then, cLMA was inserted by the guidance of the index finger until it reached the triangular base of the oropharynx. Results: There was no statistically significant difference in terms of demographic data and placement success; placement success was better in the study group (100% versus 98.6% and P = 0.45). Similarly, the count of attempts was better in the study group. The mean attempt number was 1.11 in group S and 1.28 in group C (P = 0.02). Also, blood on LMA was seen to be more common in group C (P = 0.04). There were no statistical differences in sore throat, but it was less seen in group S. Conclusion: The new maneuver was better than the standard technique and easy to use in daily practice.

Randomized Evaluation of the Single-use SoftSeal™ and the Re-useable LMA Classic™ Laryngeal Mask

A number of laryngeal masks are available, including both re-usable and single-use masks. Single-use laryngeal masks may decrease the risk of transmitting prion infections. We performed a single-blind randomized trial in 200 spontaneously breathing female patients under general anaesthesia with nitrous oxide, to compare a new single-use laryngeal mask, the SoftSeal™ (Portex Ltd, U.K.), with a re-usable laryngeal mask, the LMA Classic™ (Laryngeal Mask Company Ltd., Cyprus). The primary outcome was successful insertion at the first attempt. Size 4 single-use (n=99) or re-usable (n=100) laryngeal masks, inserted by experienced anaesthetists, were equivalent for successful placement at the first attempt (90% versus 91% respectively). The single-use mask was less easy to insert (47% difficult versus 9%, P<0.001). Clinical and anatomical tests of position and function were similar. The cuff pressure of the re-usable mask increased significantly compared with the single-use mask (median +10 cm versus –2 cm H 2 O, P<0.001). Forty per cent of patients allocated the single-use mask and 20% of those allocated the re-usable mask experienced sore throat at 24 hours postoperatively (P<0.05). An estimation of cost per patient use was greater for the re-usable mask.

We conclude that the SoftSeal™ single-use laryngeal mask and the LMA Classic™ re-usable laryngeal mask airway are of similar clinical utility in terms of successful insertion and airway maintenance. The re-usable laryngeal mask was easier to insert and associated with less postoperative sore throat, but costs were higher.

An Evaluation of the Modified Airway Management Device

This is a preliminary report on the use of the modified Airway Management Device in 50 spontaneously breathing patients undergoing elective day care surgery.

We were successful in establishing a clear airway in all 50 patients, 46 of these patients had a patent airway on the first attempt. All patients were successfully managed with the Airway Management Device throughout the surgery.

Partial airway obstruction during maintenance of anaesthesia occurred in three cases requiring only minor manipulations. Our result showed that the Airway Management Device may be used as an alternative airway management in anaesthesia.

Impact of airway management strategies on magnetic resonance image quality

BACKGROUND

Use of general anaesthesia or deep sedation during magnetic resonance imaging (MRI) studies leads to pharyngeal muscle relaxation, often resulting in snoring and subsequent vibrations with head micromotion. Given that MRI is very susceptible to motion, this causes artifacts and image quality degradation. The purpose of our study was to determine the effectiveness of different airway management techniques in overcoming micromotion-induced MRI artifacts.

METHODS

After obtaining institutional review board approval, we conducted a retrospective study on the image quality of central nervous system MRI studies in nine patients who had serial MRIs under general anaesthesia. All data were obtained from electronic records. We evaluated the following airway techniques: use of no airway device (NAD); oral, nasal, or supraglottic airway (SGA); or tracheal tube. To assess MRI quality, we developed a scoring system with a combined score ranging from 6 to 30. We used the linear mixed model to account for patient-dependent confounders.

RESULTS

We assessed 85 MRI studies from nine patients: 48 NAD, 27 SGA, four oral, four nasal, and two tracheal tube. Arithmetical mean combined scores were 21.6, 27.6, 20.3, 15.3, and 29.5, respectively. The estimated mean combined scores for the NAD and SGA cohorts were 22.0 and 27.3, respectively, showing that SGA use improved the combined score by 5.3 (P<0.0001).

CONCLUSIONS

The use of an SGA during MRI studies under general anaesthesia or deep sedation significantly improves image quality.

[Comparison of three different insertion techniques with LMA-Unique™ in adults: results of a randomized trial]

BACKGROUND

The triple airway maneuver insertion technique allowed faster insertion of the LMA. This study compared three different insertion techniques of the laryngeal mask airway-Unique™.

METHODS

One hundred and eighty ASA I-II patients aged 18-65 years were included into the study. Patients were randomly allocated to the standard, rotational and triple airway maneuver (triple) group. In the standard group (n=60), the LMA (Laryngeal Mask Airway) was inserted with digital intraoral manipulation. In the triple group (n=60), the LMA was inserted with triple airway maneuver (mouth opening, head extension and jaw thrust). In the rotational group (n=60), LMA was inserted back-to-front, like a Guedel airway. Successful insertion at first attempt, time for successful insertion, fiber optic assessment, airway morbidity and hemodynamic responses were assessed.

RESULTS

Successful insertion at the first attempt was 88.3% for the standard, 78.3% for the rotational and 88.3% for the triple group. Overall success rate (defined as successful insertion at first and second attempt) was 93% for the standard, 90% for the rotational and 95% for the triple group. Time for successful insertion was significantly shorter in the triple group (mean [range] 8.63 [5-19]s) compared with the standard (11.78 [6-24]s) and rotational group (11.57 [5-31]s). Fiber optic assessment, airway morbidity and hemodynamic responses were similar in all groups.

CONCLUSIONS

Rotational and triple airway maneuver insertion techniques are acceptable alternatives. Triple airway maneuver technique shows higher overall success rates and allows shorter insertion time for LMA insertion and should therefore be kept in mind for emergent situations.

An Airway Management Device: The Laryngeal Mask Airway—A Review

The laryngeal mask airway (LMA) is an airway management device that has become an accepted part of anesthetic practice in both pediatric and adults surgical patients. It is inserted without the use of a laryngoscope or muscle relaxants into the hypopharynx forming a low pressure seal around the glottis. The LMA provides a better airway than a face mask with or without an oral airway. Insertion techniques are quickly learned and are described in this review. Since the LMA forms a less secure seal than an endotracheal tube (ETT), several important limitations and contraindications exist. This includes patients at high risk for regurgitation of gastric contents into the lungs causing pulmonary aspiration and patients requiring high ventilatory pressures or prolonged ventilation. These contraindications have limited its introduction and utilization in the intensive care unit (ICU). The LMA is a helpful tool in the management of both the expected and unexpected difficult airway, where it may serve both as an emergency airway and as a conduit to intubation of the trachea with an ETT over a fiberoptic bronchoscope (FOB) or gum elastic bougie. A lifesaving airway has been provided by the LMA where no other means of achieving ventilation were possible in patients, including neonates, trauma victims, woman undergoing cesarean section, and in the setting of cardiac arrest. There are very few reported uses of the LMA in the ICU. We believe that familiarity with the LMA's design, use, and limitations by critical care practitioners will increase its use in emergency airway management and in the ICU. The LMA may prove to be the first of a new generation of airway devices placed into the hypopharynx to provide an alternative to the endotracheal tube and mask airway.

Pressure vs. volume control ventilation: effects on gastric insufflation with size-1 LMA

BACKGROUND

In this randomized prospective study, peak airway pressure (PAP) and gastric insufflation were compared between volume control ventilation (VCV) and pressure control ventilation (PCV) using size-1 laryngeal mask airway (LMA) in babies weighing 2.5-5 kg.

METHODS

Forty ASA I and II children, weighing 2.5-5 kg, undergoing elective infraumbilical surgeries (duration < 60 min) were randomized to two groups of 20 each to receive either PCV or VCV. Patients at risk of aspiration, difficult airway and upper respiratory tract infection, and poor lung compliance were excluded. Anesthesia technique included sevoflurane/O(2)/N(2)O without neuromuscular blockade. PAP in PCV and tidal volume in VCV modes were changed to achieve adequate ventilation (P(E)CO(2) of 5-5.4 kPa). PAP was maintained below 20 cm H(2)O. Chi-squared test, Mann-Whitney U-test and Wilcoxon W-test were applied; P < 0.05 was considered significant.

RESULTS

Mean PAP (cm H(2)O) was 12.2 ± 1.09 in PCV and 13.60 ± 0.94 in VCV groups (P = 0.000). The confidence interval of mean difference of PAP varied from 0.79 to 2.10. Significant increases in abdominal circumference were observed in both groups: PCV: 0.94 ± 1.04 cm and VCV: 2.2 ± 1.3 cm; (P = 0.000). The SpO(2) and hemodynamic variables did not differ between the groups. One patient in VCV group (with PAP = 14 cm H(2)O) could not be ventilated to the target P(E)CO(2), and the LMA had to be replaced with tracheal tube.

CONCLUSION

In conclusion, PCV should be the preferred mode to provide positive pressure ventilatio (PPV), when using the size-1 cLMA in babies weighing 2.5-5 kg, in view of less gastric insufflation associated with it for surgeries of brief duration. More studies are required to validate the clinical significance of these two modes of ventilation in longer procedures, in this subpopulation.

Comparison of Laryngeal Mask with Endotracheal Tube for Anesthesia in Endoscopic Sinus Surgery

Background

The purpose of this study was to compare surgical conditions, including the amount of intraoperative bleeding as well as intraoperative blood pressure, during functional endoscopic sinus surgery (FESS) using flexible reinforced laryngeal mask airway (FRLMA) versus endotracheal tube (ETT) in maintaining controlled hypotension anesthesia induced by propofol-remifentanil total i.v. anesthesia (TIVA).

Methods

Sixty normotensive American Society of Anesthesiologists I—II adult patients undergoing FESS under controlled hypotension anesthesia caused by propofol-remifentanil-TIVA were randomly assigned into two groups: group I, FRLMA; group II, ETT. Hemorrhage was measured and the visibility of the operative field was evaluated according to a six-point scale.

Results

Controlled hypotension was achieved within a shorter period using laryngeal mask using lower rates of remifentanil infusion and lower total dose of remifentanil.

Conclusion

In summary, our results indicate that airway management using FRLMA during controlled hypotension anesthesia provided better surgical conditions in terms of quality of operative field and blood loss and allowed for convenient induced hypotension with low doses of remifentanil during TIVA in patients undergoing FESS.

The difficult airway in adult critical care

INTRODUCTION

The difficult airway is a common problem in adult critical care patients. However, the challenge is not just the establishment of a safe airway, but also maintaining that safety over days, weeks, or longer.

AIMS

This review considers the management of the difficult airway in the adult critical care environment. Central themes are the recognition of the potentially difficult airway and the necessary preparation for (and management of) difficult intubation and extubation. Problems associated with tracheostomy tubes and tube displacement are also discussed.

RESULTS

All patients in critical care should initially be viewed as having a potentially difficult airway. They also have less physiological reserve than patients undergoing airway interventions in association with elective surgery. Making the critical care environment as conducive to difficult airway management as the operating room requires planning and teamwork. Extubation of the difficult airway should always be viewed as a potentially difficult reintubation. Tube displacement or obstruction should be strongly suspected in situations of new-onset difficult ventilation.

CONCLUSIONS

Critical care physicians are presented with a significant number of difficult airway problems both during the insertion and removal of the airway. Critical care physicians need to be familiar with the difficult airway algorithms and have skill with relevant airway adjuncts.

The changing pattern of anesthesia, 1954-2004: a review based on the content of theCanadian Journal of Anesthesia in its first half-century

PURPOSE

In order to review changes and progress in anesthesiology in the second half of the 20th century, and to recognize the first half-century of the Journal's existence.

SOURCE

The content of the Journal from its inauguration in 1954 through 2004 was reviewed.

RESULTS

Although the data base is that of the Canadian Journal, many of the contributions were from other countries, and for this reason the findings will have relevance both in Canada and elsewhere. The review suggests that anesthesiology evolved in two phases in this period: from 1954 to 1978 and from 1979 to 2004. The first was characterized by the introduction of new drugs and adaptation to new surgical techniques; the second, by a greater emphasis on clinical excellence, outcome, quality patient care both in the operating room and elsewhere in the hospital, and research.

CONCLUSIONS

Although profound advances in knowledge, techniques, and relationships, have shaped the pattern and practice of anesthesiology in this half-century, the basic concerns of anesthesiologists relating to the practice of anesthesia and to their patients remained unchanged. At the same time, the many advances that have shaped anesthesiology in this half-century have extended the understanding of the phenomenon of anesthesia and enhanced the quality of patient care, which gives rise to the hope that anesthesiologists will continue to fully achieve these twin goals in the next half-century.

Evaluation of laryngeal mask as an alternative to endotracheal intubation in cats anesthetized under spontaneous or controlled ventilation

OBJECTIVE

To compare the cardiorespiratory effects and incidence of gastroesophageal reflux with the use of a laryngeal mask airway (LMA) or endotracheal tube (ET) in anesthetized cats during spontaneous (SV) or controlled ventilation (CV).

STUDY DESIGN

Prospective randomized experimental trial.

ANIMALS

Thirty-two adult crossbred cats, weighing 2.7 +/- 0.4 kg.

METHODS

The cats were sedated with intramuscular (IM) methotrimeprazine (0.5 mg kg(-1)) and buprenorphine (0.005 mg kg(-1)), followed 30 minutes later by induction of anesthesia with intravenous (IV) thiopental (12.5-20 mg kg(-1)). An ET was used in 16 cats and an LMA in the remaining 16 animals. Anesthesia was maintained with 0.5 minimum alveolar concentration (0.6%) of halothane in oxygen using a Mapleson D breathing system. Cats in both groups were further divided into two equal groups (n = 8), undergoing either SV or CV. Neuromuscular blockade with pancuronium (0.06 mg kg(-1)) was used to facilitate CV. Heart and respiratory rates, direct arterial blood pressure, capnometry (PE'CO2) and arterial blood gases were measured. Gastric reflux and possible aspiration was investigated by intragastric administration of 5 mL of radiographic contrast immediately after induction of anesthesia. Cervical and thoracic radiographs were taken at the end of anesthesia. Data were analyzed using anova followed by Student-Newman-Keuls, Kruskal-Wallis or Friedman test where appropriate.

RESULTS

Values for PaCO2 and PE'CO2 were higher in spontaneously breathing cats with the LMA when compared with other groups. Values of PaO2 and hemoglobin oxygen saturation did not differ between groups. Gastroesophageal reflux occurred in four of eight and two of eight cats undergoing CV with ET or LMA, respectively. There was no tracheal or pulmonary aspiration in any cases.

CONCLUSIONS AND CLINICAL RELEVANCE

The use of an LMA may be used as an alternative to endotracheal intubation in anesthetized cats. Although aspiration was not observed, gastric reflux may occur in mechanically ventilated animals.

The New Perilaryngeal Airway (CobraPLA™) Is as Efficient as the Laryngeal Mask Airway (LMA™) but Provides Better Airway Sealing Pressures

The Laryngeal Mask Airway (LMA) is a frequently used efficient airway device, yet it sometimes seals poorly, thus reducing the efficacy of positive-pressure ventilation. The Perilaryngeal Airway (CobraPLA) is a novel airway device with a larger pharyngeal cuff (when inflated). We tested the hypothesis that the CobraPLA was superior to the LMA with regard to insertion time and airway sealing pressure and comparable to the LMA in airway adequacy and recovery characteristics. After midazolam and fentanyl administration, 81 ASA physical status I-II outpatients having elective surgery were randomized to receive an LMA or CobraPLA. Anesthesia was induced with propofol (2.5 mg/kg IV), and the airway was inserted. We measured 1) insertion time; 2) adequacy of the airway (no leak at 15-cm-H2O peak pressure or tidal volume of 5 mL/kg); 3) airway sealing pressure; 4) number of repositioning attempts; and 5) sealing quality (no leak at tidal volume of 8 mL/kg). At the end of surgery, gastric insufflation, postoperative sore throat, dysphonia, and dysphagia were evaluated. Data were compared with unpaired Student's t-tests, chi2 tests, or Fisher's exact tests; P < 0.05 was significant. Patient characteristics, insertion times, airway adequacy, number of repositioning attempts, and recovery were similar in each group. Airway sealing pressure was significantly greater with CobraPLA (23 +/- 6 cm H2O) than LMA (18 +/- 5 cm H2O, P < 0.001). The CobraPLA has insertion characteristics similar to the LMA but better airway sealing capabilities.

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.

LMA-Classic and LMA-ProSeal are effective alternatives to endotracheal intubation for gynecologic laparoscopy

PURPOSE

To compare the laryngeal mask airways (LMA), LMA-Classic(TM) (LMA-C) and LMA-ProSeal(TM) (PLMA) with the endotracheal tube (ETT) with respect to pulmonary ventilation and gastric distension during gynecologic laparoscopy.

METHODS

We stratified 209 women, aged > or = 18 yr, ASA physical status I-III, by body mass index as non-obese (< or = 30 kg x m(-2)) or obese (> 30 kg x m(-2)) and randomized them to LMA-C/PLMA or ETT groups for airway management. Anesthesia was induced with propofol, fentanyl and succinylcholine or rocuronium. In the LMA-C/PLMA group we used a size 4 LMA-C in non-obese patients and size 4 or 5 PLMA in obese patients. In the ETT group we used a cuffed 7.0 mm ETT in all patients. Anesthesia was maintained with isoflurane in nitrous oxide and 30-50% oxygen, fentanyl and neuromuscular blockade with mechanical ventilation (tidal volume 10 mL x kg(-1)). The staff surgeon, blinded to the type of airway, scored stomach size on an ordinal scale 0-10 at initial insertion of the laparoscope and immediately before the conclusion of the surgical procedure.

RESULTS

There were no crossovers and no statistically significant differences between LMA-C/PLMA and ETT groups for SpO(2,) P(ET)CO(2) or airway pressure before or during peritoneal insufflation in short (< or = 15 min) or long (> 15 min) periods of peritoneal inflation. Differences between groups with respect to stomach size changes during surgery were not statistically significant.

CONCLUSION

A correctly placed LMA-C or PLMA is as effective as an ETT for positive pressure ventilation without clinically important gastric distension in non-obese and obese patients.

The LMA-ProSeal is an effective alternative to tracheal intubation for laparoscopic cholecystectomy

PURPOSE

To compare LMA-ProSeal (LMA-PS) with endotracheal tube (ETT) with respect to pulmonary ventilation and gastric distension during laparoscopic cholecystectomy.

METHODS

We randomized 109 ASA I-III adults to LMA-PS or ETT after stratifying them as non-obese or obese (body mass index > 30 kg x m-2). After preoxygenation, anesthesia was induced with propofol, fentanyl and rocuronium. An LMA-PS (women #4, men #5) or ETT (women 7 mm, men 8 mm) was inserted and the cuff inflated. A #14 gastric tube was passed into the stomach in every patient and connected to continuous suction. Anesthesia was maintained with nitrous oxide, oxygen and isoflurane. Ventilation was set at 10 mL x kg-1 and 10 breaths x min-1. The surgeon, blinded to the airway device, scored stomach size on an ordinal scale of 0-10 at insertion of the laparoscope and upon decompression of the pneumoperitoneum.

RESULTS

There were no statistically significant differences in SpO2 or P(ET)CO2 between the two groups before or during peritoneal insufflation in either non-obese or obese patients. Median (range) airway pressure at which oropharyngeal leak occurred during a leak test with LMA-PS was 34 (18-45) cm water. Change in gastric distension during surgery was similar in both groups. Four of 16 obese LMA-PS patients crossed over to ETT because of respiratory obstruction or airway leak.

CONCLUSIONS

A correctly seated LMA-PS or ETT provided equally effective pulmonary ventilation without clinically significant gastric distension in all non-obese patients. Further studies are required to determine the acceptability of the LMA-PS for laparoscopic cholecystectomy in obese patients.

An evaluation of the Airway Management Device

We have evaluated the Airway Management Device (AMD) in 105 anaesthetised patients. We were successful in establishing a clear airway on the first attempt on 69 occasions and unable to establish a patent airway at all in 10 patients. Airway obstruction requiring removal of the device occurred during maintenance of anaesthesia in a further two cases and during emergence in three. Loss of the airway during anaesthesia occurred in eight of 95 patients and could be reversed by manipulation of the airway in six cases. Overall, a mean of 0.56 manipulations per patient were required to establish an airway and a further 0.42 per patient were required during maintenance of anaesthesia. In the 95 patients in whom an airway was established, assisted ventilation was satisfactory in 93, with a leak pressure above 20 cmH2O in 65. Intracuff pressure was measured in 12 cases and was above 100 cmH2O in eight. Minor complications occurred in 12 patients. Blood was visible on removal of the device in six cases.

The laryngeal mask airway: a comprehensive review for the Emergency Physician

The Laryngeal Mask Airway (LMA) was developed in the 1980s, but has only recently begun to be used in Emergency Medicine. The LMA affords effective assisted ventilation without requiring endotracheal intubation or visualization of the glottis. In doing so, it is more efficacious than a bag-valve-mask apparatus, although the risk of aspiration of gastric contents persists, particularly if the device is not properly placed. The LMA also has significant potential utility in management of the difficult airway. Most reported clinical experience with the LMA has come from the operating room. This article provides an overview of the extensive potential utility of the LMA in the Emergency Department and prehospital settings as well as a comprehensive review of the pertinent advantages, disadvantages, and complications associated with its use.

The oesophageal-tracheal Combitube Small Adult

Airway management during gynaecological laparoscopy is complicated by intraperitoneal carbon dioxide inflation, Trendelenburg tilt, increasing airway pressures and pulmonary aspiration risk. We investigated whether the oesophageal-tracheal Combitube 37 Fr SA is a suitable airway during laparoscopy. One hundred patients were randomly allocated to receive either the Combitube SA (n = 49) or tracheal intubation (n = 51). Oesophageal placement of the Combitube was successful at the first attempt [16 (3) s]. Peak airway pressures were 25 (5) cmH2O. An airtight seal was obtained using air volumes of 55 (13) ml (oropharyngeal balloon) and 10 (1) ml (oesophageal cuff). Significant correlations were observed between patient's height and weight and the balloon volumes necessary to produce a seal. Similar findings were recorded for the control group, with tracheal intubation being difficult in three patients. The Combitube SA provided a patent airway during laparoscopy. Non-traumatic insertion was possible and an airtight seal was provided at airway pressures of up to 30 cmH2O.

Recurrent laryngeal nerve injury caused by a laryngeal mask airway

Although there have been few reports of serious complications with the laryngeal mask airway, we record a case of permanent unilateral vocal cord paralysis following the use of a laryngeal mask airway and review the literature describing injuries, not only to the recurrent laryngeal nerves but also to the hypoglossal and lingual nerves.

Anesthesia for intranasal surgery: a comparison between tracheal intubation and the flexible reinforced laryngeal mask airway

The purpose of the study was to assess the suitability and safety of the flexible reinforced laryngeal mask airway (FRLMA) for intranasal surgery (INS) anesthesia. A secondary objective was to compare the incidence of complications of removal of the FRLMA with tracheal extubation in awake and anesthetized patients. One hundred fourteen ASA physical status I and II patients requiring INS were randomly assigned into three groups: Group I = FRLMA, Group II = endotracheal tube (ET) extubated awake, and Group II = ET extubated deeply anesthetized. In Group I, the incidence of coughing and oxyhemoglobin desaturation at removal was significantly reduced compared with that in Groups II and III (P < 0.05). There were no episodes of postremoval laryngospasm in Group I; in Group III, the incidence was 19% (P < 0.05), whereas in Group II, it was 6% (not significantly different). The number of patients with oxyhemoglobin desaturation < or = 92% on admission to the postanesthesia care unit was 0% in Group I, 26% in Group II (P < 0.05), and 16% in Group III (not significantly different). At bronchoscopy, the incidence of blood visible in the airway was low and similar among the three groups (3%, 6%, and 3%, respectively). There were no significant differences in the incidence of airway complications between Groups II and III.

IMPLICATIONS

We compared airway management for intranasal surgery anesthesia using a new device, the flexible reinforced laryngeal mask airway, with the current standard of tracheal intubation. The study demonstrates that the flexible reinforced laryngeal mask airway can provide a safe, protected airway with a smoother emergence from anesthesia than tracheal intubation.

The intubating laryngeal mask. Clinical appraisal of ventilation and blind tracheal intubation in 110 patients

This study assesses the efficacy of the intubating laryngeal mask as a ventilation device and blind intubation guide. Following induction of anaesthesia with propofol, the device was successfully inserted at the first attempt in 110/110 (100%) patients. Placement took less than 10 s in all patients. Size selection was based on nose-chin distance. Adequate ventilation was achieved in 104/110 (95%) patients. Blind tracheal intubation using an 8-mm internal diameter straight silicone cuffed tracheal tube was attempted 3 min after the administration of vecuronium. Passage of a lighted stylet through the intubating laryngeal mask was used to determine the position of the intubating laryngeal mask cuff before blind intubation. If resistance was felt during intubation, a sequence of adjusting manoeuvres was used, based on the depth at which resistance occurred. Tracheal intubation was possible in 104/104 (100%) patients. In 42 (40%) patients, no resistance was encountered and the trachea was intubated at the first attempt. Sixty-two (60%) patients required one adjusting manoeuvre. The mean (range) time taken to successful intubation, i.e. the time from disconnection of the intubating laryngeal mask from the breathing system to successful tracheal intubation, was 79 (12-315) s. Six patients with potential or known intubation problems were included in the study. The tracheas of all six patients were successfully intubated. We conclude that the intubating laryngeal mask is an effective ventilation device and intubation guide with potential for use in patients who may present difficulty in tracheal intubation.

The cuffed oropharyngeal airway for spontaneous ventilation anaesthesia. Clinical appraisal in 100 patients

The cuffed oropharyngeal airway is a modified Guedel airway with a distal inflatable cuff and a proximal connector for attachment to an anaesthesia circuit. The purpose of this study was to evaluate this device for spontaneous ventilation anaesthesia in 100 adult patients. Anaesthesia was induced with fentanyl and propofol and maintained with nitrous oxide and isoflurane in oxygen. The device was inserted when anaesthetic depth was judged to be adequate. Adverse airway events and interventions (i.e., manoeuvres performed in order to provide a clear airway) were analysed from video recordings and detailed notes. The position of the device was assessed fibreoptically during spontaneous ventilation. The device provided a clear airway in 98% of patients during manually assisted ventilation, in 100% during spontaneous ventilation and in 100% during emergence. However, 91% of patients required at least one airway intervention at some time. Jaw life was required for 33% of the time during manually assisted ventilation and 21% of the time during spontaneous ventilation. Most interventions occurred during the first 3 min of either manually assisted or spontaneous ventilation. The incidence of adverse airway events during manually assisted ventilation was 8%, during spontaneous ventilation was 5% and during emergence was 5%. Oxygen saturation briefly fell to between 87 and 89% on six occasions. On fibreoptic assessment, the vocal cords were visible in 29% of patients on fibreoptic assessment and the epiglottis was visible in 90%. Mild sore throat occurred in 4% of patient. We conclude that the cuffed oropharyngeal airway is suitable for spontaneous ventilation anaesthesia and has a low complication rate but that most patients require one or more interventions to provide a clear airway.

Laryngeal mask airway position and the risk of gastric insufflation

A potential risk of the laryngeal mask airway (LMA) is an incomplete mask seal causing gastric insufflation or oropharyngeal air leakage. The objective of the present study was to assess the incidence of LMA malpositions by fiberoptic laryngoscopy, and to determine their influence on gastric insufflation and oropharyngeal air leakage. One hundred eight patients were studied after the induction of anesthesia, before any surgical manipulations. After clinically satisfactory LMA placement, tidal volumes were increased stepwise until air entered the stomach, airway pressure exceeded 40 cm H2O, or air leakage from the mask seal prevented further increases in tidal volume. LMA position in relation to the laryngeal entrance was verified using a flexible bronchoscope. The overall incidence of LMA malpositions was 40% (43 of 108). Gastric air insufflation occurred in 19% (21 of 108), and in 90% (19 of 21) of these patients, the LMA was malpositioned. Oropharyngeal air leakage occurred in 42%, and was independent of LMA position. We conclude that clinically unrecognized LMA malposition is a significant risk factor for gastric air insufflation.

IMPLICATIONS

Routine placement of laryngeal mask airways does not require laryngoscopy. In our study, fiberoptic verification of mask position revealed suboptimal placement in 40% of cases. Such malpositioning considerably increased the risk of gastric air insufflation.

Gas leak and gastric insufflation during controlled ventilation: face mask versus laryngeal mask airway

PURPOSE

To compare two airway management techniques, face mask (FM) with oropharyngeal airway and laryngeal mask airway (LMA), with respect to the effectiveness of positive pressure ventilation and airway maintenance.

METHODS

After induction of anaesthesia, two airway management techniques (FM or LMA) and three peak pressures (20, 25 and 30 cm H2O) were randomly applied during controlled ventilation in 60 patients. Data collected included inspiratory and expiratory volumes and presence of gastro-oesophageal insufflation. Leak was calculated by subtracting the expiratory from the inspiratory volume, expressed as a fraction of the inspiratory volume.

RESULTS

Expiratory volumes (mean +/- SD) at 20, 25 and 30 cm H2O for LMA ventilation were 893 +/- 260, 986 +/- 276 and 1006 +/- 262 respectively, and for FM ventilation 964 +/- 264, 1100 +/- 268 and 1116 +/- 261. Leak fractions at 20, 25 and 30 cm H2O for LMA ventilation were 0.21 +/- 0.15, 0.24 +/- 0.18 and 0.26 +/- 0.18 respectively, and for FM ventilation 0.14 +/- 0.09, 0.14 +/- 0.09 and 0.12 +/- 0.08. The frequency of gastro-oesophageal insufflation was 1.6%, 5% and 5% for the LMA and 5%, 15% and 26.6% for the FM for ventilation pressures of 20, 25 and 30 cm H2O respectively which was greater with LMA use.

CONCLUSION

Ventilation was adequate in all patients using both techniques. Leak was pressure dependent and greater with LMA use. Most of the leak was vented to the atmosphere via the pharynx. Gastro-oesophageal insufflation was more frequent with ventilation using the face mask. LMA use with positive pressure ventilation would appear to be a better airway management method than the face mask.

The laryngeal mask airway reduces blood flow in the common carotid artery bulb

PURPOSE

The introduction of the laryngeal mask airway (LMA) has had a major impact on anaesthetic practice in the last ten years. Previous authors have demonstrated pressures equivalent to mean arterial blood pressure within the cuff of the LMA. This study examined the effects of cuff inflation on the cross sectional area, flow and velocity of blood flow at the level of the carotid sinus.

METHODS

Seventeen patients scheduled to have LMAs inserted as part of routine anaesthetic management were recruited into the study. Measurements of the common carotid artery bulb area, peak velocity and blood flow were performed upon LMA cuff inflation and deflation using a 5 MHz pulse wave Doppler probe.

RESULTS

Deflation of the cuff resulted in an increase in the cross sectional area (from 0.58 +/- 0.05 to 0.64 +/- 0.04 cm2; P < 0.005), an increase in blood flow (from 65.6 +/- 5.6 to 73.9 +/- 5.6 cm3.sec-1; P < 0.05) and a slight but non significant increase in velocity of blood flow.

CONCLUSION

This study demonstrates that inflation of the cuff on the LMA results in a decrease in carotid bulb cross sectional area which results in a decrease in blood flow.

Laryngeal mask airway facilitated fibreoptic bronchoscopy in infants

PURPOSE

To assess the efficacy of the laryngeal mask airway (LMA) for fibreoptic bronchoscopy (FOB) and bronchoalveolar lavage (BAL) in infants.

METHODS

Observations were made in 19 consecutive infants undergoing FOB under general anaesthesia (GA) plus topical local anaesthesia. Anaesthesia was induced with N2O, O2, and halothane or sevoflurane except in two patients who received propofol and one who received thiopentone. Anaesthesia was maintained with oxygen and either sevoflurane, halothane, desflurane, or propofol infusion. No neuromuscular blockers were used. Size #1 or #2 LMAs were used through which a 3.5 mm fibreoptic bronchoscope was introduced. ECG, noninvasive blood pressure, pulse oximetry and, PETCO2 were measured. Intra- and post-procedural complications were recorded.

RESULTS

Mean age was 6 months; mean weight was 6.6 kg. Chronic wheezing was the indication for FOB in eight patients. Minor complications occurred in five patients: difficult LMA placement in one patient required changing size from #2 to #1; two patients had laryngospasm and bronchospasm that resolved with deepened anaesthesia and nebulised bronchodilator; one patient had transient arterial O2 desaturation, responding to increased FIO2, and one patient required tracheal intubation because ventilation via LMA became inadequate.

CONCLUSION

The minor complications observed were similar to other series and did not result in morbidity or mortality. We feel that GA via LMA facilitates safe FOB in infants. It affords excellent airway management, a quiet patient, and passage of a large fibreoptic bronchoscope for better imaging and suction channel required for BAL.

The laryngeal mask airway: a comparison between two insertion techniques

The purpose of the study was to compare the ease of insertion of the laryngeal mask airway using the standard uninflated approach or with a fully inflated cuff. Two hundred consecutive patients undergoing anesthesia using a laryngeal mask airway were randomized to have the laryngeal mask inserted using either method. Successful insertion was judged primarily by the clinical function of the airway. The number of insertion attempts to achieve a satisfactory airway and whether an alternative technique was required for success were recorded. On removal of the laryngeal mask, a blind observer noted the presence or absence of blood. Just before leaving the recovery room, each patient was asked whether they had a sore throat. Insertion technique made no difference with regard to first attempt success. However, the presence of blood on the removed masks (P < 0.01) and sore throat (P < 0.01) were less frequent in the inflated cuff group. We conclude that the inflated cuff insertion technique is an acceptable alternative to the standard approach and has the advantage of reducing the incidence of minor pharyngeal mucosal trauma, as evidenced by mucosal bleeding and sore throat.

IMPLICATIONS

Insertion of the laryngeal mask airway with the cuff fully inflated is equally successful to the standard uninflated approach in experienced hands. The inflated technique was associated with less minor pharyngeal mucosal trauma and, consequently, a lower incidence of postoperative sore throat. This implies that the inflated technique would be acceptable to the general population of laryngeal mask users.

Respiratory mechanics, gastric insufflation pressure, and air leakage of the laryngeal mask airway

A potential risk of the laryngeal mask airway (LMA) is incomplete mask seal, which causes air leakage or insufflation of air into the stomach. The objective of the present study was to assess respiratory mechanics, quantify air leakage, and measure gastric air insufflation in patients ventilated via the LMA. Thirty patients were studied after induction of anesthesia but prior to any surgical manipulations. After the insertion of the LMA, patients were ventilated with increasing tidal volumes until one of the three following end points were reached: 1) gastric air insufflation, 2) airway pressure > 40 cm H2O, or 3) limitation of further increase in tidal volume by air leakage. The following variables were determined:inspired volume (VI), expired volume (VE), maximum inspiratory pressure (Pmax), airway pressure at gastric inflation (Pinfl), respiratory time constant (RC), compliance (C), resistance (R), and leakage fraction (FL). Respiratory mechanics were in the physiological range. Gastric insufflation occurred in 27% of the patients at inspiratory pressures between 19 and 33 cm H2O. Air leakage of more than 10% was evident at inspiratory pressures between 25 and 34 cm H2O. The end point of 40 cm H2O airway pressure was reached in only three patients. We conclude that the LMA is not better in preventing airway pressure transmission to the esophagus than a conventional face mask. However, a high FL is associated with reduced gastric air insufflation.

Laryngeal mask airway in severe cervical ankylosis

PURPOSE

We present a case of the successful use of a laryngeal airway (LMA) to ventilate the lungs of a patient with severe ankylosing spondylitis for surgery requiring intense muscular relaxation. The use of an LMA in such circumstances is controversial.

CLINICAL FEATURES

The patient was a 61-yr-old man with severe emphysema, a cervical spine fixed in marked anterior flexion, and reduced mouth opening (35 mm). The patient refused an awake tracheal intubation because of a previous distressing experience with a fibreoptic awake nasal intubation and an 11 day SICU stay with controlled ventilation via an endotracheal tube. Attempts at spinal blocks had failed in the past. After administration of thiopentone and succinylcholine a #4 LMA was inserted and the lungs were safely ventilated for a 10 min reduction of a dislocated femoral head.

CONCLUSION

The present view that severe ankylosing spondylitis is a contraindication to the use of an LMA may need revision in view of this and other reports of successful airway management in patients with that disease.

Laryngo-pharyngeal complaints following laryngeal mask airway and endotracheal intubation

STUDY OBJECTIVE

To investigate the incidence and severity of laryngo-pharyngeal complaints following anesthesia with the use of a laryngeal mask airway (LMA) compared with endotracheal intubation in adults.

DESIGN

Prospective study with randomized patient selection.

SETTING

University medical center.

PATIENTS

202 adult ASA physical status I, II, and III patients scheduled for elective surgery of either an extremity or breast, or a transurethral resection.

INTERVENTIONS

Following intravenous induction of anesthesia, a standard LMA size #3, #4, or #5 corresponding to the patient's body weight, was inserted in 103 patients; 99 patients were intubated with a polyvinylchloride endotracheal tube [7.5 mm inner diameter (ID) in women and 8.0 mm ID in men]. Cuff pressures in the LMA group were initially reduced to a minimum pressure at which an air-tight seal between the LMA and the laryngeal inlet was provided at a positive pressure of 20 cm H2O during manual bag ventilation. Cuffs of endotracheal tubes were inflated and controlled to a volume needed to prevent gas leak at 35 cm H2O pressure.

MEASUREMENTS AND MAIN RESULTS

Cuff pressures were continuously monitored in both groups. Patients assessed their laryngo-pharyngeal complaints on a 101-point numerical rating scale on the evening after surgery and the following two days. No difference was found in the incidence and severity of sore throat on the evening following surgery or on the two following days. Dysphonia was more frequent following intubation than following LMA insertion on the day of surgery (46.8% vs. 25.3%) and on the first postoperative day (28.1% vs. 11.6%) (p < 0.05). However, the incidence of dysphonia increased with the duration of anesthesia in LMA patients but not in intubated patients. The incidence of dysphagia was significantly higher following LMA insertion compared with endotracheal intubation on the day of surgery (23.8% vs. 12.5%), and on the first postoperative day (22.3% vs. 10.4%). The severity of the individual complaints of minor laryngo-pharyngeal morbidity was comparable between groups. The type of airway management during anesthesia did not affect patient satisfaction with the anesthesia received.

CONCLUSIONS

There is a distinct pattern of laryngo-pharyngeal complaints following the use of the LMA and endotracheal intubation. With regard to minor laryngo-pharyngeal morbidity, the advantage of the LMA to endotracheal intubation is questionable.

Use of the laryngeal mask airway in oral and maxillofacial surgery

PURPOSE

General anesthesia for the nonintubated oral and maxillofacial surgical patient presents unique anesthetic conditions. The primary concern is the maintenance of an unobstructed airway and protection against aspiration, while minimizing both interference and interruption of the surgical procedure. The laryngeal mask airway is an alternative to the nasal hood for such airway management. The purpose of this article is to inform the oral and maxillofacial surgeon of the clinical relevant information pertaining to the use of the laryngeal mask airway in oral and maxillofacial surgery. Experience with clinical use is discussed.

Cricoid pressure impedes positioning and ventilation through the laryngeal mask airway

PURPOSE

To assess the effect of cricoid pressure on the positioning of and ventilation through the laryngeal mask airway (LMA).

METHODS

In a double-blind, randomized design, the LMA was inserted with (CP[+] group, n = 20) or without double-handed cricoid pressure (CP[-] group, n = 20). Ventilation through the LMA was assessed by measuring expiratory tidal volume and judged as adequate when a mean expiratory tidal volume of > or = 10 ml.kg-1 could be obtained. The LMA position was examined by fibreoscopy. The position of the mask relative to the cricoid cartilage and the cervical spine was radiologically examined (n = 10 in each group).

RESULTS

Ventilation was adequate in all patients in the CP[-] group but in only five patients (25%) of the CP[+] group (P < 0.001). The glottis was visible fibreoptically below the mask aperture in all patients in the CP[-] group, but in only three patients in the CP[+] group (P < 0.001). Fibreoscopy showed that the mask was not inserted far enough in the remaining 17 patients of the CP[+] group. The reason for unsuccessful ventilation in the CP[+] group was excessive gas leakage (n = 2) and/or partial or complete airway obstruction (n = 13), which was noted fibreoptically. The radiographs showed that the tip of the mask in the CP[-] group was located below the level of the cricoid cartilage (C6 or C7 vertebra). The mask tip in the CP[+] group was above this level (C4 or C5 vertebra) (P < 0.01).

CONCLUSION

Cricoid pressure impedes positioning of and ventilation through the LMA.

Laryngeal mask insertion with a laryngoscope in paediatric patients

PURPOSE

To assess epiglottic position after laryngeal mask airway (LMA) insertion with or without the use of a laryngoscope.

METHODS

A double-blind randomized study. In 48 children an LMA (#2 for 6-20 kg, #2.5 for 20-30 kg) was inserted either blindly or with the help of a laryngoscope and its position assessed using fibreoptic endoscopy.

RESULTS

An unobstructed view of the glottis, as assessed by fibrescope, was observed in 10 of 25 patients in the laryngoscope group, but only in 1 of 22 patients in the blind insertion group (P = 0.005).

CONCLUSION

This technique offers an alternative when the standard technique has failed, or when LMA insertion precedes bronchoscopy or intubation via the laryngeal mask.

The effect of laryngeal mask cuff pressure on postoperative sore throat incidence

STUDY OBJECTIVE

To study the effect of laryngeal mask airway (LMA) cuff pressure on the incidence of postoperative sore throat.

DESIGN

Prospective, randomized, observational study.

SETTING

Operating room of a university hospital.

PATIENTS

200 consecutive adult patients requiring anesthesia for gynecologic procedures.

INTERVENTIONS

Anesthesia was induced with thiopental 3-5 mg/kg, fentanyl 2 micrograms/kg, vecuronium bromide 0.05mg/kg, and enflurane 0.8% to 2% and maintained with nitrous oxide and oxygen (65%/35%) and enflurane.

MEASUREMENTS AND MAIN RESULTS

In Group 1, cuff pressure measurement was continuously performed until the end of the operation. In Group 2, 5 minutes after induction of anesthesia and 2 minutes after insertion of the LMA, cuff pressure was also continuously observed and reduced to the minimal pressure required for airtightness. In the recovery room, after the operation, patients were questioned for postoperative sore throat 4, 8, and 24 hours after the operation following a scoring protocol (score 0 = no complaints, score 1 = minimal sore throat, score 2 = moderate sore throat, score 3 = severe sore throat: "never a LMA again". Continuous monitoring of cuff pressure revealed a steady increase of pressure (during the first 60 minutes increases of 43 cm H2O) in Group 1. In Group 2, after release of air, cuff pressures were significantly lower through the entire operation when compared with Group 1. In Group 1, 8 patients claimed to have a sore throat (Score 1, n = 4; Score 2, n = 3; Score 3, n = 1). In Group 2, no patient complained of sore throat.

CONCLUSIONS

A significant increase in cuff pressure is seen during the first 60 minutes. Three minutes after insertion of the laryngeal mask, cuff pressure can significantly be reduced without any major gas leakage. Postoperative sore throat can be reduced when cuff pressure is continuously monitored and kept on low-pressure values.