Laryngeal Mask Airway Position Research Articles

Comparison of two techniques of laryngeal mask airway insertion – is reverse technique better than standard?

Background: Standard technique of Laryngeal Mask Airway (LMA) insertion has been routinely and successfully employed in adults. This technique has failed in certain instances prompting evaluation of alternative techniques. ‘Reverse technique’ is one which is studied and employed successfully in paediatric population. However, this has not been widely studied in adults. Materials and methods: In this randomised, prospective, single blinded study, we compared the standard technique and reverse technique of LMA insertion with respect to success rate, time taken for successful insertion, confirming the final position of LMA by performing a fibreoptic evaluation of the glottic view and incidence of postoperative sore throat in 60 adult patients undergoing surgery under general anaesthesia. Statistical analysis used: Using SPSS 11.5TM software, Independent samples’ test and Chi-square test was applied to the results where appropriate. A p value of < 0.05 was considered as statistically significant. Results: LMA insertion was successful in all patients using standard technique and all but one patient using reverse technique. Insertion was complete with in 30 seconds with the longest being 24.08 seconds in reverse technique group. Grade 1 or 2 glottic view on fibrescopy was obtained in 90.3% patients in the standard technique group as against 100% patients in reverse technique group. There was no significant difference in immediate or delayed incidence of sore throat. Conclusions: Reverse technique of LMA insertion has a comparable success rate with the standard technique in adult patients undergoing general anaesthesia.

The place of ultrasonography in confirming the position of the laryngeal mask airway in pediatric patients: an observational study

Background and objectivesLaryngeal mask airways are increasingly used as supraglottic devices during general anesthesia. Ultrasonography can provide a dynamic image simultaneous to placing the supraglottic airway device. In the current study, the incidence of suboptimal laryngeal mask airway position and replacement in children was evaluated using simultaneous ultrasonographic imaging. MethodsA prospective observational study was conducted on 82 patients aged 3–15 years with American Society of Anesthesiologists (ASA) physical status I or II. Patients under general anesthesia and with airway provided by a laryngeal mask airway were included. The position of the laryngeal mask airway was evaluated by ultrasonography on two planes. According to our scoring system, Grade I and Grade II were determined to indicate acceptable placement, while Grade III was determined to indicate unacceptable placement. Suboptimal laryngeal mask airway placement rates and the requirement of replacement were determined. Laryngeal mask airway placement optimized by ultrasonography was evaluated with both leak tests and a fiberoptic laryngoscope. ResultsThe average age of the patients was 6.27 ± 4.66 years. After evaluation with ultrasonography, 65 (79.3%) of the laryngeal mask airways were found to be optimally positioned, while the position of 13 (15.9%) had to be corrected, and 4 (4.9%) had to be replaced. There was a moderate positive correlation between the ultrasonographic evaluation and leak test evaluation (p < 0.001; r = 0.628). Relocation of the laryngeal mask airway was determined to be an independent risk factor affecting the development of complications (OR = 2.961; p = 0.046; 95% Cl 2.850–30.745). ConclusionThe use of ultrasonography to verify and relocate laryngeal mask airway placement is noninvasive and effective.

Effect of diffusion of anaesthetic gases on fibre-optic view change of laryngeal mask airway and post-operative laryngo-pharyngeal morbidity in children - A randomised controlled trial.

Background and Aims:The diffusion of nitrous oxide (N2O) into the air-filled cuff of the classic laryngeal mask airway (LMA) may lead to an increase in cuff pressure (CP) and displacement of LMA affecting its performance. This study was conducted to evaluate the change in optimal position of LMA by fibre-optic bronchoscope, the changes in cuff pressure and oropharyngeal leak pressure (OLP), and post-operative laryngo-pharyngeal morbidity during N2O–oxygen (O2) anaesthesia in children.Methods:After ethics committee approval and written informed consent, 84 children, aged 2 to 8 years undergoing lower abdominal surgery using LMA were included. Anaesthesia was induced with sevoflurane and maintained with either 33% O2 in air (Group 1) or with 33% O2 in 67% N2O (Group 2) along with sevoflurane. The position of LMA using fibre-optic bronchoscope, CP and OLP were recorded at 30, 60 and 90 minutes and at the end of surgery. The incidence of post-operative sore throat, hoarseness of voice and dysphagia was assessed for 24 hours.Results:A mild (Grade 1) change in fibre-optic position of LMA was observed in 6 out of 42 children maintained with N2O–O2 anaesthesia. The cuff pressure was higher than baseline in group 2 at all three time points with the maximum at 90 minutes (93.23 ± 14.86 cm H2O vs. 39.78 ± 7.75 cm H2O; P < 0.05). The OLP was comparable between the groups during the initial 60 minutes and then increased in group 2. The incidence of post-operative sore throat was significantly higher in group 2 (P = 0.008).Conclusion:The diffusion of anaesthetic gases into the air-filled cuff does not change the fibre-optic position of the LMA significantly but increases the cuff pressure and incidence of post-operative laryngo-pharyngeal complications in children.

Comparison of the clinical performance of the flexible laryngeal mask airway in pediatric patients under general anesthesia with or without a muscle relaxant: study protocol for a randomized controlled trial

BackgroundThe insertion of a laryngeal mask airway (LMA) is difficult in children due to the unique features of their airways. Muscle relaxants have been reported to facilitate LMA insertion in adults; however, there is a lack of evidence supporting this in children. This trial is designed to assess the feasibility of LMA insertion with and without the use of muscle relaxants in pediatric patients under general anesthesia.Methods/designThis is a prospective, double-blind, single-center, parallel-arm, non-inferiority, randomized controlled trial to be conducted with participants aged 2–7 years who are undergoing elective ophthalmic surgery under general anesthesia. Participants are randomly assigned to one of two groups based on whether muscle relaxants are used (MR group, n = 64) or not used (Saline group, n = 64) prior to LMA insertion. The primary outcome is the oropharyngeal leak pressure (OLP) at a fixed gas flow of 3 L/min. The secondary outcomes are intubation time for successful insertion, ease of insertion and mask bagging, intubation attempt for successful insertion, successful insertion rate on the first attempt, fiberoptic view of the LMA position, postoperative complications, and changes in hemodynamic and ventilatory parameters.DiscussionWe will compare the OLPs to determine whether the muscle relaxant provides better conditions for the manipulation of the LMA. This is the first randomized controlled trial to investigate whether muscle relaxants are beneficial to the clinical performance of LMA insertion in pediatric patients under general anesthesia. This trial will be a resource for improving the process and safety of pediatric LMA insertion under general anesthesia.Trial registrationClinicalTrials.gov, NCT03487003. Registered on 18 April 2018.

Comparison of a new visual stylet (Discopo)–guided laryngeal mask airway placement vs conventional blind technique: a prospective randomized study

Study ObjectiveTo compare the ease of laryngeal mask airway (LMA) insertion and fiberoptic view of LMA after placement using the Discopo visual stylet–guided insertion and conventional blind technique. DesignProspective, randomized controlled study. SettingOperating room in a university hospital. PatientsOne hundred adult patients scheduled for elective surgery under LMA general anesthesia were enrolled. InterventionsPatients were randomly allocated to 2 groups: GLMA group using a visual stylet–guided technique (n=50) and BLMA group using standard blind technique (n=50). Correct placement of the LMA was confirmed using clinical test along with fiberoptic assessment. MeasurementsUnblinded data were collected about the insertion time, the first attempt success rate, the LMA position adjustment rate, fiberoptic view of LMA anatomical position, hemodynamic responses, and the adverse insertion responses (bucking, breathholding, and laryngospasm). Blinded data were recorded about postoperative airway morbidity (visible blood staining on LMA at removal, sore throat, and hoarseness). Main resultsInsertion was more frequently successful at the first attempt in GLMA than that in BLMA group (100% vs 92%; P=.041). The time taken for establishing effective airway was shorter in GLMA than that in BLMA (54.8 vs 62.9 seconds; P=.001). The patients in BLMA group required more readjustment and reinsertion than those in GLMA group (38% vs 0%; P=.000). The fiberoptic view was significantly better in GLMA group (P<.001). No difference between the 2 groups existed regarding hemodynamic stress responses, incidences of adverse insertion responses, and postoperative airway morbidity. ConclusionsBy direct visualizing the whole process of LMA insertion, the Discopo visual stylet increases the success rate and accuracy rate of LMA placement without increasing hemodynamic stress response or incidences of adverse events.

Comparison of the Supreme and the ProSeal laryngeal mask airway in patients undergoing laparoscopic cholecystectomy: A randomized controlled trial

ObjectiveThe single-use LMA Supreme (Teleflex, Inc., Wayne, PA, USA) and the LMA ProSeal (Teleflex, Inc., Wayne, PA, USA) laryngeal mask airway (LMA) have similar characteristics. To date, studies have not achieved a consensus regarding the oropharyngeal leak pressure (OLP) of the LMA Supreme and LMA ProSeal, and there is little information on their efficacy in laparoscopic cholecystectomy. This study compared the safety and efficacy of the LMA Supreme and LMA ProSeal devices in patients undergoing laparoscopic cholecystectomy. MethodEighty-four eligible consenting patients were randomly allocated to the LMA Supreme group or the LMA ProSeal group. Both groups received the standard anesthesia technique. The Supreme or ProSeal LMA was inserted, the cuff was inflated to 60 cmH2O, and the LMA position was confirmed. Anesthesia was maintained using propofol and 50% oxygen in air. A gastric tube was inserted through the drain tube of the LMA to deflate the stomach, and the first attempt success rate and insertion time were recorded. During surgery, the intra-abdominal pressure was maintained at 12 mmHg. The fiberoptic view of the larynx was determined by passing a flexible fiberoptic bronchoscope. The OLPs, success rate, insertion time, hemodynamic and respiratory parameters, and complications were recorded at different time points. ResultsThe mean OLP was significantly lower in the LMA Supreme group than in the LMA ProSeal group (24.9 ± 5.3 cmH2O vs. 28.4 ± 5.8 cmH2O; p < 0.01). The first attempt success rate and ease of insertion grading for LMA were higher in the Supreme group. The insertion time was lower in the Supreme group than in the ProSeal group (p < 0.01). The fiberoptic view was better with the ProSeal LMA. The hemodynamic and ventilatory parameters and postoperative sore throat were comparable in both groups. ConclusionThe LMA ProSeal has a higher OLP than the LMA Supreme. The success rate of first attempt insertion and ease of insertion were better for the LMA Supreme group and the insertion time was lower in the LMA Supreme group. The Supreme and ProSeal LMAs were both effective for positive pressure ventilation in laparoscopic cholecystectomy.

Ultrasound guided positioning of laryngeal mask airway in children

Objective To evaluate the efficacy of ultrasound-guided laryngeal mask airway (LMA) in children. Methods ASA Ⅰ and Ⅱ children (aged 1 to 6 years) scheduled for orthopedic surgery of limbs were recruited in this study. A LMA was inserted after induction of general anesthesia. After mechanical ventilation for 5 minutes, the air-filled cuff was deflated and then inflated with saline. Ultrasonography was then performed by a high frequency linear-array transducer to confirm the correct placement of the LMA. Results The LMA can be easily recognized on the transverse view of the thyroid cartilage notch, appearing as a circle around the glottis, which was called the dumbbell sign. On the sagittal view of the thyroid cartilage, the LMA has an archlike appearance which ended below the thyroid cartilage. Oblique scan over the cricoid cartilage shows the tip of LMA is located at the upper portion of the esophagus. Conclusions Filling the LMA cuff with saline instead of air allows better LMA visualization by ultrasound. This method enhances correct positioning of the LMA, which is crucial to ensure safe ventilation. Key words: Ultrasonography; Laryngeal masks; Position

Application of Minimum Effective Cuff Inflating Volume for Laryngeal Mask Airway and its Impact on Postoperative Pharyngeal Complications.

Background:High intracuff pressure can cause severe pharyngeal complications including sore throat or hoarseness after laryngeal mask airway (LMA) removal postoperatively. Though the application of minimum effective cuff inflating volume is suggested to maintain airway sealing and adequacy of ventilation for patients receiving general anesthesia with LMA at lower level of the intracuff pressure, it is currently not a standard care in most of the anesthetic departments. In this study, the minimum effective cuff inflating volume was determined for classic LMA Well Lead™ (Well Lead Medical Co., Ltd., China) and its impact on postoperative pharyngeal complications was also explored.Methods:Patients with American Society of Anesthesiologists physical status (I–III) undergoing the short-duration urological surgery were recruited in this trial. First, the minimum effective cuff inflating volume was determined for size 4 or 5 LMA Well LeadTM in the study 1. Immediately following placement and confirmation of ideal LMA position, the cuff was inflated with 5, 7, 10 ml of air and up to 30 ml at 5 ml increment. The intracuff pressure, oropharyngeal leak pressure (OLP), and inspiratory peak airway pressure under positive pressure ventilation at the corresponding cuff volume as indicated above were recorded. Second, the enrolled patients were randomly allocated into minimum effective cuff inflating volume group (MC) and routine care (RC) group in the study 2. The minimum effective cuff inflating volume was applied and maintained in MC group, whereas the cuff volume was inflated with half of the maximum cuff inflating volume recommended by manufacturer in RC group throughout the surgical procedure and stay in postanesthesia care unit prior to LMA removal. The incidence of pharyngeal complications at 0, 2, 24, and 48 h after removal of LMA and other intra-operative adverse events were also documented.Results:The intracuff pressure varied with the cuff inflating volume in a positive linear correlation manner (Y = 11.68X − 42.1, r2 = 0.9191) under the range of 5–30 ml for size 4 LMA. In similar with size 4 LMA, the data were also showed the linear relationship between the intracuff pressure and the cuff inflating volume (Y = 7.39X − 10.9, r2 = 0.8855) for size 5 LMA. The minimal effective cuff inflating volume for size 4 or 5 LMA was 7–9 ml in combination of considering OLP needed to maintain airway sealing during intermittently positive pressure ventilation. The intracuff pressure in MC group was lower compared with RC group (63.0 ± 3.7 vs. 126.4 ± 24.0 cmH2O for size 4 LMA; 55.6 ± 2.4 vs. 138.5± 26.8 cmH2O for size 5 LMA; P < 0.0001). The incidence of pharyngeal adverse events was lower in MC group versus the RC group at 2, 24 h after LMA removal.Conclusions:The relationship between the cuff inflating volume and the intracuff pressure for size 4 or 5 LMA Well Lead™ is in a linear correlation manner at the range of 5–30 ml. The minimal cuff inflating volume is adequate for satisfactory airway sealing and consequently associated with lower incidence of postoperative pharyngeal complications for LMA Well Lead.™

Efficacy of Ambu AuraOnce laryngeal mask airway in Chinese patients undergoing general anesthesia

Objective To evaluate the efficacy of Ambu AuraOnce laryngeal mask airway (LMA) in Chinese patients undergoing general anesthesia. Methods Fifty-six female patients, aged 20-64 yr, weighing 45-75 kg, of American Society of Anesthesiology physical statusⅠor Ⅱ (MallampatiⅠ-Ⅲ), scheduled for elective breast surgery under general anesthesia, were equally and randomly divided into either Ambu AuraOnce LMA group (group A) or LMA Supreme group (group S) using a random number table. After induction of anesthesia, Ambu AuraOnce LMA was inserted in group A, and LMA Supreme was placed in group S. After successful placement of LMA, correct position was confirmed by fiberoptic laryngoscopy. Intermittent positive pressure ventilation was performed during surgery to maintain pulse oxygen saturation > 95% and partial pressure of end-tidal CO2 at 30-45 mmHg. The success rate, insertion time, extubation time, airway sealing pressure, peak airway pressure and occurrence of air leakage of LMA were recorded. After removal of the LMA, the blood stains on the LMA were checked, and the occurrence of hypoxemia, regurgitation, nausea, vomiting and bucking was recorded. The occurrence of sore throat, hoarseness and dysphagia was also recorded within 24 h after surgery. Results There were no significant differences in terms of insertion time, overall success rate, success rate at first attempt, removal of LMA time, airway sealing pressure, and incidence of air leakage of LMA, hypoxemia, blood stains on the LMA, sore throat, hoarseness and dysphagia between the two groups. The rate for correct position of LMA confirmed by fiberoptic laryngoscopy was significantly higher in group A than in group S. Conclusion Ambu AuraOnce LMA can safely and effectively be applied for airway management in Chinese patients undergoing general anesthesia. Key words: Laryngeal masks; Respiration, artificial; Anesthesia, general

An ultrasound evaluation of laryngeal mask airway position in pediatric patients: an observational study.

In children, the laryngeal mask airway (LMA) is frequently displaced within the hypopharynx, resulting in repositioning of the device. When the tip of the LMA is placed in the esophageal inlet, the arytenoids are moved ventrally. When the LMA is rotated or deviated, the ventral movement of the arytenoids may result in asymmetric elevation of an arytenoid cartilage, which can be detected with ultrasound (US). In this study, we sought to estimate the incidence of LMA malposition detected with US in pediatric patients. The primary end point was to compare the incidence of LMA malposition between US and fiber optic bronchoscopy (FOB). The secondary end points were to find the interrelationship between US-detected and FOB-detected malposition of the LMA and to locate the diagnostic performance of US in detecting LMA malposition. In this observational study, 100 consecutive children were included. After anesthetic induction, US evaluation was performed before and after LMA insertion to obtain the glottic image on the anterior neck. FOB was performed to assess LMA position (FOB LMA grade and LMA rotation grade). With a post-LMA US image, the symmetry of the arytenoid cartilages was evaluated. Asymmetrical elevation of an arytenoid cartilage in reference to the glottic midline and the opposite arytenoid cartilage was graded as 0 to 3 (US arytenoid grade). The interrelationships between US arytenoid grade and FOB LMA grade or LMA rotation grade were assessed. The incidence of asymmetrical elevation of an arytenoid was 50% (95% confidence interval [CI], 40%-60%). On FOB, the incidence of LMA malposition was 78% (95% CI, 69%-86%), and that of LMA rotation was 43% (95% CI, 33%-53%). The incidence of LMA malposition was higher with FOB (P < 0.0001), but the incidence of rotation was similar (P = 0.395). US arytenoid grade did not correlate with FOB LMA grade (P = 0.611) but showed a significant correlation with LMA rotation grade (P < 0.0001; 95% CI, 60%-83%). To detect a rotated LMA, US had a sensitivity of 93% (95% CI, 81%-98%) and a specificity of 82% (95% CI, 70%-91%). The positive and negative predictive values were 80% (95% CI, 66%-90%) and 94% (95% CI, 83%-99%), respectively. The accuracy was 87% (95% CI, 79%-93%). Although US could not detect the suboptimal depth of an LMA, US has promise of being an accurate tool in detecting a rotated LMA.

Fiberoptic assessment of the Laryngeal Mask Airway (Laryseal) position after one hour of positive pressure ventilation: an observational study

Study ObjectivesTo determine, by fiberoptic endoscope, malpositioning of the Laryngeal Mask Airway (LMA) and other extraglottic devices. DesignProspective study. SettingUniversity-affiliated medical center. Patients60 adult, ASA physical status 1 and 2 patients, aged 20 - 60 years, scheduled to undergo ophthalmic procedures with general anesthesia during controlled ventilation via LMA (Laryseal). MeasurementsAdequacy of ventilation was determined by the absence of audible leak and appropriate capnograph trace. Fiberoptic assessment and imaging of LMA position were done after proper insertion of the LMA and after one hour of positive pressure ventilation (PPV). Assessment included position of the epiglottis, glottis, and cuff. Main ResultsThe epiglottis was visible in 50 patients (83.3%). Vocal cords were visible in 58 patients at the time of insertion, and in 52 patients after one hour of PPV (P = 0.047). The arytenoids were herniating through the mask aperture after one hour of PPV (P = 0.0132). The cuff position was less optimal after one hour of controlled ventilation (P = 0.032). ConclusionLMA position may change spontaneously with time during PPV, especially when the LMA position is not optimum at the time of insertion. The LMA should be adequately inserted with all possible measures in cases with general anesthesia and PPV. Fiberoptic assessment of LMA position intraoperatively may be advantageous.

WITHDRAWN: Fiber-optic evaluation of laryngeal mask airway position during controlled mechanical ventilation: Time effect

WITHDRAWN: Fiber-optic evaluation of laryngeal mask airway position during controlled mechanical ventilation: Time effect

Comparison of postoperative complication between Laryngeal Mask Airway and endotracheal tube during low-flow anesthesia with controlled ventilation

To compare the postoperative complications between Laryngeal Mask Airway (LMA) and endotracheal tube (ETT) during low-flow anesthesia with controlled ventilation. Eighty adult Patients with ASA class I or II were randomly allocated into two forty-patient groups (ETT or LMA). Cuff pressure was monitored during anesthesia. After high uptake period, fresh gas flow (FGF) was decreased to 1 lit/min and isoflurane set to 1%. Monitoring during anesthesia included non-invasive blood pressure, ECG, ETCO2 and pulse oximetry. System leakage (>100 ml/min), rebreathing and any attempt to increase FGF to overcome the leak were monitored during anesthesia. Later, patients were extubated and transferred to Post Anesthesia Care Unit (PACU). In PACU, the incidence of sore throat, cough, difficulty in swallowing and shivering was monitored for all patients. Leakage was observed in two and three cases in ETT and LMA groups respectively (P>0.05). Postoperative cough, sore throat and difficulty in swallowing were significantly less in LMA than ETT group. No significant difference was observed regarding ETCo2 values between 2 groups. If careful measures regarding insertion techniques, correct LMA position and routine monitoring of LMA cuff pressure are taken, LMA can be used as a safe alternative with lower incidence of post operation complication compared with ETT during low-flow controlled anesthesia with modern anesthetic machines.

Modified technique in securing the LMA in multiple extractions

AbstractAims:  We have developed a technique to secure the LMA without obstructing the surgical field and have minimal interference with airway maintenance. Nasal endo‐tracheal tube is the gold standard for airway maintenance; however, it can slow turnover time due to it requiring a longer recovery time compared with the laryngeal mask airway (LMA). The LMA position often obscures the surgical field in these cases often necessitating repositioning intra‐operatively. This can adversely affect airway patency.Materials and methods:  We audited two different techniques of securing LMAs (north‐facing with our modification vs. south‐facing conventional taped to the lower lip/chin) in a total of 223 patients undergoing bilateral extractions. A questionnaire for surgeons and anaesthetists was used to assess their suitability and complications occurred noting particularly obstructions caused to the LMA, cause for obstruction, management taken to correct obstruction.Results:  We found the risk of partial or total obstruction of the airway during surgical extractions with a conventionally placed LMA to be around 36% compared with 19% with a retromolar positioned flexi‐LMA during our study.Conclusion:  The retro‐molar positioned LMA not only increased operating space but showed a reduced number of obstructions caused to the LMA.

A randomised crossover trial comparing a single‐use polyvinyl chloride laryngeal mask airway with a single‐use silicone laryngeal mask airway

We compared insertion rates of single-use polyvinyl chloride laryngeal mask airways (LMAs) vs single-use silicone LMAs in 72 anaesthetised patients. Both airways were produced by Flexicare Medical. Laryngeal mask airway insertion was successful on the first attempt in 68/72 (94%) polyvinyl chloride LMAs vs 64/72 (89%) silicone LMAs (p = 0.39). Overall insertion rates were 72/72 (100%) for the polyvinyl chloride LMAs and 71/72 (99%) for the silicone LMAs (p = 1.0). Mean (SD) insertion times were similar for polyvinyl chloride and silicone LMAs: 24.3 (5.1)s vs 24.8 (7.8)s (p = 0.64). Laryngeal mask airway position, as assessed using a fibrescope, was not different (p = 0.077). The median (IQR [range]) leak pressure was 16 (12-20 [6-30]) cmH(2) O for the polyvinyl LMA and 18 (13-22 [6-30]) cmH(2) O or the silicone LMA (p = 0.037). In conclusion, we did not find any important differences between polyvinyl chloride and silicone laryngeal mask airways.

Fiber‐optic assessment of LMA position in children: a randomized crossover comparison of two techniques

This crossover study compared fiber-optic assessment of laryngeal mask airway (LMA) position in children using two LMA insertion techniques, i.e., standard and rotational. Seventy-eight ASA I children, aged 2.5 months to 10 years, undergoing elective cataract surgery were included in this study. LMA was inserted in random order using either standard or rotational technique, removed, and thereafter crossed over to alternate technique. Positioning of LMA was assessed using fiber-optic bronchoscope with each technique. Change in the incidence of fiber-optic assessment grades 1 and 2 between two insertion techniques was measured as the primary outcome. Secondary outcome measures studied were first-attempt success rate, overall success rate, time for successful insertion, visual analogue scale for placement, complications, and maneuvers used to relieve airway obstruction. Incidence of fiber-optic grades 1 and 2 was 61.5% with standard technique and increased to 92.3% with rotational technique (P < 0.001, McNemar's test) (RR 3.0, 95% CI 2.2-4.2). Median (IQR) fiber-optic grading was significantly better with rotational technique [2 (1-2)] as compared to standard technique [2 (2-3)], (P < 0.001, Wilcoxon signed rank test). First-attempt success rate was significantly higher (96.2%) with rotational technique compared with standard technique (80.7%) (P = 0.04, McNemar's test). Overall success rate (i.e., successful insertion with two attempts) was 100% with rotational technique compared with 89.7% with standard technique (P = 0.003, Fischer's exact test). Time for successful insertion and incidence of complications were significantly lesser with rotational technique. Rotational technique of LMA insertion in children is associated with better seating of LMA (as observed on fiber-optic assessment) compared with the standard technique. Also, it is associated with higher success rate and lower incidence of complications.

Optimal Degree of Mouth Opening for Laryngeal Mask Airway Function During Oral Surgery

This study was performed to determine the optimal degree of mouth opening in anesthetized patients requiring laryngeal mask airway (LMA) during oral surgery. A single, experienced LMA user inserted the LMA in 15 patients who were scheduled for elective oral surgery. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were sequentially documented in 5 mouth conditions-opening of 1.4 (neutral position), 2, 3, 4, and 5 cm-and any resulting ventilatory difficulties were recorded. Oropharyngeal leak pressure with the mouth open 4 cm (21.8 ± 3.2 cm H(2)O, P = .025) and 5 cm (27.3 ± 7.2 cm H(2)O, P < .001) was significantly higher than in the neutral position (18.1 ± 1.5 cm H(2)O), as was intracuff pressure (neutral position, 60.0 ± 0 cm H(2)O; 4 cm, 72.6 ± 5.1 cm H(2)O [P < .001]; and 5 cm, 86.9 ± 14.4 cm H(2)O [P < .001]). LMA position, observed by fiberoptic bronchoscopy, was unchanged by mouth opening, being similar in the 5 mouth conditions (P = .999). In addition, ventilation difficulties (abnormal capnograph curves or inadequate tidal volume) occurred in 2 of 15 patients (13%) and 7 of 15 patients (53%) (P < .001) with the mouth opening of 4 and 5 cm, respectively. This study showed that a mouth opening over 4 cm led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution, because gastric insufflation, sore throat, and ventilation difficulties may occur. A mouth opening of 3 cm achieves acceptable airway conditions for anesthetized patients requiring LMA.

The Influence of Mouth Opening on Oropharyngeal Leak Pressure, Intracuff Pressure, and Cuff Position With the Laryngeal Mask Airway

The aim of this study was to investigate the influence of mouth opening on oropharyngeal leak pressure, intracuff pressure, and cuff position of the laryngeal mask airway (LMA). Fifteen patients who were scheduled for elective oral surgery were recruited into this study. A single, experienced LMA user inserted the LMA according to the manufacturer's recommended technique. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were documented under 3 mouth conditions: neutral position (1.4-cm distance between upper and lower incisors), mouth open (5- to 6-cm distance between upper and lower incisors), and return to the neutral position. Any ventilation difficulties under the 3 mouth conditions were recorded. Oropharyngeal leak pressure with the mouth open was higher than in the neutral position (P < .001). Compared with the neutral position, intracuff pressure was also higher with the mouth open (P < .001). Both measurement values returned to control levels when the neutral position was once again assumed. The LMA position observed by fiberoptic bronchoscopy was unchanged by mouth opening and was similar in the 3 mouth conditions (P = .998). Although ventilatory difficulties occurred after mouth opening in 8 of 15 patients (P < .001), it did not occur when the neutral position was reassumed. This study showed that mouth opening led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution because gastric insufflation, sore throat, and ventilation difficulties may occur.

Transient isolated lingual nerve neuropraxia associated with general anaesthesia and laryngeal mask use: two case reports and a review of the literature

Transient, isolated lingual nerve neuropraxia is a rare complication following general anaesthesia. Reports implicate airway manipulation and we describe two new cases associated with laryngeal mask airway (LMA) and review the related English language literature. Unilateral numbness and loss of taste on the anterior tongue were the characteristic symptoms. Collation of literature data (median and range) with that from the new cases showed: patient age was 38 (20-61) years and female to male ratio was 1.2:1. Surgery time was 62.5 (20-150) min and symptom duration was 28 (7-120) days. Lingual neuropraxias reported have been transient and patients can be advised, despite disturbing symptoms, that recovery is anticipated in about 1 month. Lingual neuropraxia reports are becoming more frequent, perhaps associated with increasing LMA use. Research is recommended as modification to LMA cuff volume, pressure and/or position within the oral cavity might ameliorate the entity.

Guidelines and criteria for the placement of laryngeal mask airways in dogs

ObjectiveTo evaluate the criteria for the insertion and correct placement of the laryngeal mask airway (LMA) in dogs. Study designProspective descriptive clinical study. AnimalsThirty healthy dogs (ASA I or II) of different breeds, age 0.33–7.0 years (2.8 ± 2.1; mean ± SD), weight 2.2–59.0 kg (23.9 ± 14.4), anaesthetized for elective surgery.Materials and methods The dogs were sedated with intravenous (IV) medetomidine (10 μg kg−1) and butorphanol (0.2 mg kg−1). If considered necessary, IV propofol (1 mg kg−1 over 30 seconds) was administered until the LMA was inserted and positioned correctly. The position of the LMA was evaluated using predefined criteria for its insertion and inflation of the cuff, together with the ability to ventilate the dogs through the LMA. ResultsThe criteria for insertion, inflation and ventilation which indicated a clinically optimal position of the LMA and its seal around the larynx were met in 19 dogs (63.3%). The dogs could be manually ventilated with inspiratory peak pressures of 10 cm H2O without capnographic or audible evidence of leakage. In 11 dogs (36.7%), the LMA was positioned suboptimally with leakage during manual ventilation with inspiratory peak pressures not exceeding 10 cmH2O. There was no evidence of breed-related differences in LMA placement and position. Conclusions and clinical relevanceThe technique for the insertion of the LMA using predefined criteria to evaluate a correct positioning and a seal led to a successful placement in dogs of both brachycephalic and nonbrachycephalic breeds. The LMA, in most of the dogs, was easily placed, well tolerated and offered a useful less invasive means of securing the upper airway.