Appropriate size of laryngeal mask

Airway Complications during and after General Anesthesia: A Comparison, Systematic Review and Meta-Analysis of Using Flexible Laryngeal Mask Airways and Endotracheal Tubes

OBJECTIVE

Flexible laryngeal mask airways (FLMAs) have been widely used in thyroidectomy as well as cleft palate, nasal, upper chest, head and neck oncoplastic surgeries. This systematic review aims to compare the incidence of airway complications that occur during and after general anesthesia when using the FLMA and endotracheal intubation (ETT). We performed a quantitative meta-analysis of the results of randomized trials.

METHODS

A comprehensive search of the PubMed, Embase and Cochrane Library databases was conducted using the key words "flexible laryngeal mask airway" and "endotracheal intubation". Only prospective randomized controlled trials (RCTs) that compared the FLMA and ETT were included. The relative risks (RRs) and the corresponding 95% confidence intervals (95% CIs) were calculated using a quality effects model in MetaXL 1.3 software to analyze the outcome data.

RESULTS

Ten RCTs were included in this meta-analysis. There were no significant differences between the FLMA and ETT groups in the incidence of difficulty in positioning the airway [RR = 1.75, 95% CI = (0.70-4.40)]; the occurrence of sore throat at one hour and 24 hours postoperative [RR = 0.90, 95% CI = (0.13-6.18) and RR = 0.95, 95% CI = (0.81-1.13), respectively]; laryngospasms [RR = 0.58, 95% CI = (0.27-1.23)]; airway displacement [RR = 2.88, 95% CI = (0.58-14.33)]; aspiration [RR = 0.76, 95% CI = (0.06-8.88)]; or laryngotracheal soiling [RR = 0.34, 95% CI = (0.10-1.06)]. Patients treated with the FLMA had a lower incidence of hoarseness [RR = 0.31, 95% CI = (0.15-0.62)]; coughing [RR = 0.28, 95% CI = (0.15-0.51)] during recovery in the postanesthesia care unit (PACU); and oxygen desaturation [RR = 0.43, 95% CI = (0.26-0.72)] than did patients treated with ETT. However, the incidence of partial upper airway obstruction in FLMA patients was significantly greater than it was for ETT patients [RR = 4.01, 95% CI = (1.44-11.18)].

CONCLUSION

This systematic review showed that the FLMA has some advantages over ETT because it results in a lower incidence of hoarseness, coughing and oxygen desaturation. There were no statistically significant differences in the difficulty of intubation or in the occurrence of laryngospasms, postoperative sore throat, airway displacement, aspiration or laryngotracheal soiling. However, there was a higher incidence of partial upper airway obstruction in the FLMA than in the ETT group. We conclude that the FLMA has some advantages over ETT, but surgeons and anesthesiologists should be cautious when applying the mouth gag, moving the head and neck, or performing oropharyngeal procedures to avoid partial upper airway obstruction and airway displacement. The FLMA should not be used on patients at high risk for aspiration.

Multicentre validation of manufacturers' weight-based recommendations for laryngeal mask airway size choice in anaesthetic practice: A retrospective analysis of 20,893 cases

BACKGROUND

Manufacturers' weight-based recommendations for laryngeal mask airway (LMA) sizes are not scientifically founded and have never been validated clinically.

OBJECTIVE

The validation of manufacturers' weight-based recommendations in clinical practice and whether other patient variables such as sex and age may influence LMA size choice.

DESIGN

A retrospective study.

SETTING

Four Israeli hospitals (two tertiary and two secondary hospitals).

METHODS

Data on LMA use were retrieved from the Anaesthesia Information Management System (AIMS). Multinomial logistic regression analysis including weight, sex and age amongst adults, adolescents and children was used to identify predictors of LMA size used (development data set). Concordance between the size of LMA used and that predicted according to the model and the manufacturers' recommendations was assessed (validation data set).

RESULTS

LMA insertions were analysed in 13,743 (65.8%) adults, 1807 (8.6%) adolescents and 5343 (25.6%) children. Suitability of manufacturers' recommendations was higher in children [4075/5343 (76.3%)] than adults [5200/13743 (37.8%)] or adolescents [885/1807 (49.0%); P < 0.001 for children vs. adults or adolescents]. Sex influenced LMA size in adults and adolescents, but not in children. Age had no influence. Amongst adults and adolescents, LMA size was better predicted by the regression model than by manufacturers' recommendations [adults: anaesthetists/model 61.7%, 95% confidence interval (95% CI) 60.1 to 63.2, anaesthetists/manufacturer 38.4%, 95% CI 36.0 to 39.0, P < 0.001; adolescents: anaesthetists/model 68.1%, 95% CI 64.1 to 72.0, anaesthetists/manufacturer 46.9%, 95% CI 42.7 to 51.1, P < 0.001]. In children, the regression model and manufacturers' weight-based recommendations performed equally (anaesthetists/model 78.0%, 95% CI 75.9 to 80.0, anaesthetists/manufacturer 75.7%, 95% CI 73.6 to 7.8, P = 0.126).

CONCLUSION

Manufacturers' weight-based recommendations for LMA size reflect clinical practice in children, but not in adults and adolescents. In these age groups, choice of LMA size is influenced by sex and weight, although with wider ranges than those recommended by manufacturers.

Laryngeal mask airways and use of a Boyle-Davis gag in ENT surgery: is there a learning curve? A prospective analysis

OBJECTIVES

The objective was to identify whether the experience of the operating surgeon was relevant to the frequency of the laryngeal mask airway (LMA) airway obstruction or change to an endotracheal tube during ear, nose, and throat surgery.

METHODS

Data were prospectively collected for 186 patients undergoing a procedure with the use of a Boyle-Davis gag and LMA over 12 months in a district-general hospital in the United Kingdom. patient demographics (age, mallampati grade), grade of surgeon, grade of anesthetist, LMA size inserted, and any intraoperative adjustments needed were recorded.

RESULTS

There was an overall intraoperative airway intervention rate of 21%. The experience of the surgeon affected the rate of intraoperative airway interventions encountered, reflected by the significantly lower rate of airway complications (ie, 10%) seen when associate specialists perform these types of procedures compared to other grades of surgeon (Fisher's exact test 2-tailed P value = .04). A significant complication rate of 50% was seen with core surgical trainees compared to other grades of surgeon (Fisher's exact test 2-tailed P value = .002).

CONCLUSIONS

The results of this study suggest there may be a learning curve for otolaryngology trainees when using a LMA. However, larger studies and further subanalyses are essential before further conclusions can be made.

Sex-based ProSeal laryngeal mask airway size selection: a randomized crossover study of anesthetized, paralyzed male and female adult patients

We compared the Size 4 and 5 ProSeal laryngeal mask airway (PLMA) in men and the Size 3 and 4, and 4 and 5 PLMA in women in terms of 1) ease of insertion, 2) oropharyngeal leak pressure (OLP), 3) ease of ventilation at a tidal volume of 10 mL/kg, 4) gas exchange, 5) location of gas leak, 6) anatomic position of the airway and drain tube, and 7) mucosal injury. Thirty male and 60 female (ASA physical status I-II; 18-80 yr old) anesthetized, paralyzed patients were studied in a crossover fashion in three equal-sized groups. PLMA insertion was performed by a single experienced operator by using digital manipulation. In male patients comparing the Size 4 and 5, OLP was higher (P = 0.0002) and leak fraction lower (P = 0.03) for the Size 5, but the number of insertion attempts, insertion time, mucosal injury, anatomic position, gas exchange, and location of gas leak were similar. In female patients comparing the Size 4 and 5 PLMA, OLP was higher for the Size 5 (P < 0.0001), but the number of insertion attempts was fewer (P = 0.02), insertion time was quicker (P = 0.02), and there was less mucosal injury (P = 0.01) with the Size 4. There were no differences in anatomic position, gas exchange, or location of gas leak. In female patients comparing the Size 3 and 4 PLMA, OLP was higher (P = 0.0005) and leak fraction was lower (P = 0.03) for the Size 4, but the number of insertion attempts, insertion time, mucosal injury, anatomic position, gas exchange, and location of gas leak were similar. There were no episodes of failed oxygenation, failed ventilation, or gastric insufflation. We conclude that if size is selected by sex, the Size 4 PLMA is preferable for women and the Size 5 PLMA for men.

IMPLICATIONS

When sex is used to select the appropriate size of the ProSeal laryngeal mask airway, the Size 4 ProSeal is preferable for women and the Size 5 ProSeal for men.