A prospective study was conducted to determine the rate of skill acquisition with the laryngeal mask airway in pediatric anesthesiology practice. The aim of the study was to provide information about the amount of supervised training required before satisfactory levels of skill were achieved.
Eight anesthesia residents in their third year of training with no prior experience using the laryngeal mask airway were observed using the device in 75 pediatric patients each (600 patients in total). Residents were given standardized guidelines for laryngeal mask airway usage in accordance with the manufacturer's recommendations and followed a predetermined protocol for anesthetic management. Induction was achieved with propofol followed by either a propofol infusion or isoflurane and either controlled or spontaneous ventilation as clinically indicated. Predefined major and minor problems were documented during the induction, maintenance, and recovery phases of anesthesia by a randomly selected supervising consultant trained in the study protocol and problem definitions.
The total number of problems was 189 occurring in 121 children. Fifty-five children had one problem, sixty-four children had two problems, and two children had three problems. Of the problems, 77 were major and 112 were minor. The problem rate per patient for overall, major, and minor problems was 31.5%, 12.8%, and 18.7%, respectively. The problem rate comparing the first to last epochs of 15 uses decreased from 62% to 2% for overall problems, 23% to 2% for major problems, and 39 to 1% for minor problems. The residents with the most problems in the final epoch had problem rates of less than 10% after 60 uses. There was a significant decrease in the overall problem rate for induction, maintenance, and recovery (P < 0.05). The major problem rate decreased significantly for induction and maintenance (p < 0.05), but not for recovery. The minor problem rate decreased significantly for induction and recovery (P < 0.05).
This study confirms that there is a rapid improvement in laryngeal mask airway skills when the standard recommended technique is employed and that a low problem rate can be achieved within 75 uses. Pediatric anesthesiologists with problem rates greater than 10% should determine if they are using the device suboptimally.
Key words: Anesthesia: pediatric. Equipment: laryngeal mask airway.
THE laryngeal mask airway (LMA) is gaining widespread popularity in the United States as a general purpose airway and has been the subject of several comprehensive reviews. [1-3]Although correct insertion of the LMA and ventilation of the lungs can be readily achieved with minimal training, as illustrated by controlled studies of nonanesthesiologists, [4,6]optimal use in anesthesia requires the acquisition of a wide range of new skills. Brain has suggested that LMA skills increase with progressive practical experience, but there are only limited [8,9]or coincidental [10-13]data supporting this concept. No study has specifically assessed skill acquisition in resident anesthesiologists in pediatric anesthesiology practice. Such information might indicate the length of supervised training required before satisfactory levels of skill are achieved.
The aim of this study was to assess the frequency of problems occurring during the first 75 LMA uses in third-year anesthesia residents with no prior experience using the LMA.
Hospital ethics committee approval was obtained for the project. Ten anesthesiology residents participated in a prospective study of skill acquisition in 75 consecutive pediatric patients each during a 3-month rotation through a pediatric department. All residents were in their third year of anesthesiology training and had never used the LMA either in children or adults. Before the study, all residents were individually instructed in LMA usage by one of the authors. Instructions were standardized and included a videotape and manual. This was followed by a demonstration of LMA usage in pediatric patients, which involved all techniques included in the study protocol. There was no specific ongoing instruction during the study period. Residents were interviewed at the end of each procedure by the supervising consultant if any problems had occurred.
All patients in whom the LMA was being used by the resident were included in the study. The decision to use the LMA in each patient was made by the supervising consultant as was the mode of its use. These decisions were based on the requirements of individual patients and the preference of the supervising consultant within the confines of the study protocol. The LMA was not used in patients at risk for aspiration or in patients in whom inspiratory pressures greater than 15 cm H2O were anticipated or for oropharyngeal surgery.
Anesthetic management was standardized according to the following protocol. Standard monitoring was begun before induction and included a electrocardiography, pulse oximetry, capnography, and noninvasive blood pressure monitoring. The size of LMA was selected according to manufacturer's instructions and was lubricated on its posterior surface with water-based KY jelly (Johnson & Johnson, Maidenhead, UK). All patients were nonpremedicated, preoxygenated, and anesthesia was induced with 3 mg/kg propofol given over 1 min. The LMA was inserted using the standard recommended technique with the cuff fully deflated when the jaw was relaxed and the lash reflex was absent. Rolled gauze swabs were used as bite guards and the LMA was secured according to manufacturer instructions. The LMA was then connected to the anesthetic breathing system and successful placement was judged by observation of chest wall movement, auscultation of the chest and neck, and capnography. Three attempts with the standard technique were allowed followed by a single attempt with an alternative technique (Guedel's technique) before insertion was considered a failure. Guedel's technique involves insertion of the LMA with the cuff fully deflated, but back-to-front, like a Guedel airway, and then rotated through 180% as it is pushed into the hypopharynx. Between attempts, patients' lungs could be ventilated with the face mask. After successful placement, leak pressure was assessed. If there was an audible leak with airway pressures < 8 cm H sub 2 O a larger size LMA was inserted. Anesthesia was maintained with either propofol 10 mg *symbol* kg sup -1 *symbol* h sup -1 reducing after 15 min to 5 mg *symbol* kg sup -1 *symbol* h sup -1 or isoflurane 0.5-1.0%. A nondepolarizing muscle relaxant, either vecuronium (0.1 mg/kg) or atracurium (0.6 mg/kg), was given after LMA insertion and additional boluses given as clinically indicated after successful LMA insertion in patients undergoing intermittent positive pressure ventilation. Patients given nondepolarizing muscle relaxants were monitored with a peripheral nerve stimulator. The choice of maintenance agent and ventilation mode was made by the supervising consultant according to clinical requirements. At the end of the procedure, any residual neuromuscular blockade was reversed with 0.05 mg/kg neostigmine and 0.02 mg/kg atropine and the anesthetic agents were discontinued. Patients were not moved or disturbed during recovery. The LMA was removed in the operating room when the patient was fully awake, then the patient was transferred to recovery. Scoring of the position of the LMA using a fiberoptic bronchoscope was not possible during the study.
Predefined major and minor problems occurring during induction, maintenance, and recovery were documented by the consultant supervising the case. Induction was defined as the start of injection of propofol until commencement of surgery. Maintenance was the time during which surgery was being performed. Recovery was the time from completion of surgery until the LMA was removed and the patient left the postanesthesia care unit. The supervising consultants were instructed in the study protocol and problem definitions before the start of the study. One of the authors ensured that these values and criteria were adhered to throughout the study by constant instruction and supervision. Supervising consultants were selected at random for each resident list and were generally unaware of the progress of each resident within the study protocol. The supervising consultant did not intervene with patient management unless a major problem had occurred. All supervising consultants were experienced in the use of the LMA (> 200 uses).
Major problems were defined as: complete airway obstruction (no air entry possible for 30 s); bronchospasm/laryngospasm; hemoglobin oxygen desaturation (SpO2< 90%); failure to insert/function within four attempts; aspiration/regurgitation/vomiting; major trauma (macroscopic tissue damage, overt bleeding/structural damage); complete displacement of the LMA from the pharynx (LMA displaced and bowl completely in oral cavity); LMA technique abandoned due to inadequate function after successful placement; gastric distension (visible increase in abdominal girth with air entry into the stomach detected at stethoscopy). Minor problems were defined as: partial airway obstruction (some air entry possible within 30 s); coughing/gagging/retching; difficulty with insertion/function (success at third or fourth attempt); partial displacement of LMA from pharynx (LMA displaced and bowl partly in oral cavity); minor trauma (microscopic tissue damage, blood staining/patient spontaneously complaining of sore throat in recovery); persistent leaks (persistent peak airway pressure without leak < 8 cm H2O after insertion of larger size). The first major problem, if any, was documented for each of the three phases of anesthesia for each patient. When a major problem did not occur the first minor problem was documented for each of the three phases of anesthesia for each patient. Thus, a maximum of three problems were allowed per patient, one for each phase of anesthesia.
The data were divided into epochs of 15 uses and the average problem rate per patient (expressed as a percentage) was determined for each epoch. The maximum problem rate per patient was 300% because each patient could have a maximum of three problems (one for each phase of anesthesia). Statistical evaluation was with chi squared test and Kendall's rank correlation. Significance was taken as P < 0.05.
Two residents failed to complete the study during their 3-month term and their data have been excluded. A total of 600 patients managed by eight residents was therefore included in the final analysis.
All patients were ASA physical status 1-3. Mean age was 6.5 yr (SD, 4.8 yr; range, 1 month-17 yr) and weight was 28.7 kg (SD, 16.7; range, 3-72). The mean length of procedures was 40 (range, 12-220) min and the type of surgery performed was general (40%), urology (17%), plastic (15%), semielective trauma (26%), and ear, nose, and throat (2%). Residents had a similar spectrum of exposure to the subspecialties. One hundred ninety (32%) patients breathed spontaneously and four hundred ten (68%) received intermittent positive pressure ventilation. Three hundred eleven (51.8%) patients received isoflurane and two hundred eighty-nine (48.2%) received propofol for maintenance. Of the 190 patients breathing spontaneously, 150 (78.9%) were given propofol and 40 (21.1%) were given isoflurane for maintenance. Of the 410 (60.7%) patients receiving intermittent positive pressure ventilation, 249 were given propofol and 161 (39.3%) were given isoflurane for maintenance. There were no demographic differences between the intermittent positive pressure ventilation and spontaneous ventilation groups, or the propofol and isoflurane groups. There were no significant differences in the spectrum of anesthetic techniques or length of procedures or type of surgery among the various epochs.
The total number of problems was 189 and these occurred in 121 children. Fifty-five children had one problem, sixty-four had two problems, and two children had three problems. Of the problems, 77 were major and 112 were minor. The problem rate per patient for overall, major, and minor problems per patient was 31.5, 12.8, and 18.7%, respectively. The major and minor problems for induction, maintenance, and recovery are listed in Table 1and Table 2. One hundred six problems occurred during induction, forty-four during maintenance, and thirty-nine during recovery. There was a significantly greater number of problems at induction compared with either the maintenance (chi squared = 29.3, P < 0.001) or the recovery (chi squared = 35.2, P < 0.001) phases of anesthesia.
The problem rate per patient comparing the first to last epoch decreased from 62% to 2% for overall problems (tau = 1.0, P < 0.05), 23% to 2% for major problems (tau = 1.0, P < 0.05) and 39% to 1% for minor problems (tau = 1.0, P < 0.05; Table 3). When the data were analyzed in terms of the phase of anesthesia, there was a significant decrease in the overall problem rate for induction, maintenance, and recovery (tau = 1.0, P < 0.05; Figure 1). The major problem rate decreased significantly for induction (tau = 1.0, P < 0.05) and maintenance (tau = 1.0, P < 0.05), but not for recovery (tau = 0.8, P < 0.1). The minor problem rate decreased significantly for induction (tau = 1.0, P < 0.05) and recovery (tau = 0.9, P < 0.05), but only two problems occurred during maintenance.
In all patients in whom the LMA technique was unsuccessful, the lungs were ventilated via a face mask after which the trachea was intubated. There were no instances in which the need for intubation was considered extremely urgent. No major morbidity resulted from the use of the LMA. One episode of vomiting occurred on induction of anesthesia, but no patient aspirated.
Progressive acquisition of skills has been demonstrated with the use of unfamiliar anesthetic equipment, such as the Belscope laryngoscope, during assessment of intubating skills of medical students, for intubation in the left lateral position and for fiberoptic intubation. Coincidental data from early LMA studies hinted that there was a rapid increase in skill. [10-12]More recently, Reinhart and Simmons have shown that respiratory therapists and paramedics acquire skills more rapidly with the LMA than the tracheal tube and Brimacombe has shown that skill acquisition continues to occur for up to 1,500 uses of the LMA in adults. .
The current study has shown that skills are rapidly acquired with LMA usage in pediatric anesthetic practice and that the average problem rate per patient can be reduced from 62% to 2% within 75 uses. Although the rate of skill acquisition varies among trainees, even the residents with the most problems in the final epoch had problem rates of less than 10%. Essential skills for LMA usage include appropriate patient selection, sensible insertion and fixation techniques, a different approach to ventilation, a readjustment of the preconceived sense of anesthetic requirement and a wide variety of new problem-solving strategies. Several factors will probably affect the rate at which LMA skills are acquired including the background level of anesthesiology skills, the quality and extent of training with the LMA, and the insertion technique chosen. The standard technique has been shown to offer better results in adults than some common alternatives, but success has also been reported for placement with the cuff partially inflated in children. Currently, there are insufficient data to know which is the optimal technique and it is possible that this will vary in different clinical circumstances.
In conclusion, our study suggests that there is a rapid improvement in LMA skills in pediatric anesthesia practice where the standard technique is employed and that a low problem rate can be achieved within 75 uses. Pediatric anesthesiologists with problem rates greater than 10% should determine if they are using the device suboptimally.