Comparison of i-gel™ supraglottic device with classic laryngeal mask airway in anesthetized paralyzed children undergoing elective surgery

Abstract

Context:

The newest variation of the i-gel supraglottic airway is a pediatric version.

Aims:

This study was designed to investigate the usefulness of the size 2 i-gel compared with the classic laryngeal mask airway (cLMA) of the same size in anesthetized, paralyzed children.

Settings and Design:

A prospective, randomized, single-blinded study was conducted in tertiary care teaching hospital.

Subject and Methods:

Sixty ASA grade I–II patients undergoing lower abdominal, inguinal, and orthopedic surgery were included in this prospective study. The patients were randomly assigned to i-gel and cLMA groups (30 patients in each group). Size 2 supraglottic airway was inserted according to the assigned group. We assessed ease of insertion, hemodynamic data, oropharyngeal sealing pressure, and postoperative complications.

Statistical Analysis Used:

Parametric data were analyzed with the unpaired t-test and non-parametric data were analyzed with the Chi-square test. Unless otherwise stated, data are presented as mean (SD). Significance was taken as P < 0.05.

Results:

There were no differences in the demographic and hemodynamic data among the two groups. The airway leak pressure of the i-gel group (26.1 ± 2.4 cm H₂O) was significantly higher than that of the cLMA group (22.64 ± 2.2 cm H₂O). The success rates for first attempt of insertion were similar among the two devices. There were no differences in the incidence of postoperative airway morbidity among the two groups.

Conclusions:

Hemodynamic parameters, ease of insertion, and postoperative complications were comparable between the i-gel and cLMA groups, but airway sealing pressure was significantly higher in i-gel group.

INTRODUCTION

Various types of supraglottic devices have been successfully used for securing and maintaining a patent airway in routine and emergency surgeries in children. Laryngeal mask airway (LMA) with an inflatable cuff has been the most common device used in the last decade. Different modifications of LMA like ProSeal, Unique, Supreme, and iLMA have been used in clinical practice and discussed in the literature. The i-gel is a relatively new and unique supraglottic airway with a noninflatable cuff made of a soft gel-like medical grade thermoplastic elastomer. It has been used in adult patients and found comparable to LMA.[1,2,3] Pediatric i-gel is now available in four different sizes – 1, 1.5, 2, and 2.5 – on the basis of body weight. There are very few studies comparing the size 2 i-gel with classic LMA (cLMA) of the same size to assess their performance in anesthetized and artificially ventilated children.

In this study, we have compared size 2 i-gel (Intersurgical Inc., Berkshire, UK) with cLMA (LMA Classic; Laryngeal Mask Company Ltd. Henley-on-Thames, UK.) for ease of insertion, oropharyngeal sealing pressures (OSPs), and air leak. Hemodynamic effects and any postoperative complications because of insertion of the device were noted.

SUBJECTS AND METHODS

After getting approval from the Hospital Ethics Committee, 60 patients were studied. A randomized prospective study was planned to compare size 2 i-gel with cLMA of the same size.

The children included in the study were 1-6 years of age, ASA physical status I–II, weighing 10-20 kg, and were posted for elective surgeries of less than 1 h duration in the supine position including lower abdominal (e.g., colostomy closure), inguinal (e.g., herniotomy, circumcision), and orthopedic procedures (e.g., upper and lower limb surgeries). The following were excluded from the study: (i) patients with upper respiratory tract symptoms, (ii) those at risk of gastroesophageal regurgitation, and (iii) those with airway related conditions such a trismus, limited mouth opening, trauma, or mass. Sixty patients were equally randomized to one of the two groups (i-gel and cLMA) of 30 each for airway management, using a computer-generated randomization program.

Written informed consent was taken from the parents prior to intervention and a standardized protocol for anesthesia was maintained for all cases. All the children were kept nil per mouth as per standard guidelines. They were premedicated with 0.3 mg/kg of midazolam syrup 1 h prior to induction of anesthesia. Induction of anesthesia included sevoflurane in oxygen with standard monitors placed. Anesthesia was maintained with 1-2% sevoflurane and 60% nitrous oxide in oxygen.

Once an adequate depth of anesthesia was achieved, the supraglottic device was inserted by the standard technique recommended by the manufacturer (single-finger technique for cLMA). We considered easy up-and-down movement of the lower jaw, no reaction to pressure applied to both angles of the mandible, and end-tidal sevoflurane concentration (EtSev) of 2.5% to indicate the adequate depth of anesthesia for insertion of the device. The technique for placement of i-gel is reviewed on the website. Each device was inserted by an experienced anesthesiologist who had performed at least 50 size 2 cLMA and 20 size 2 i-gel placements.

The ease of insertion was graded as very easy, easy, or difficult by the attending anesthesiologist. The device was inserted with “sniffing” position. The following manoeuvres were included: (i) chin lift, (ii) jaw thrust, (iii) head extension, and (iv) neck flexion. If the device could be inserted without any manipulation, it was graded as “very easy.” If there was only one manipulation required, it was called “easy” and any difficulty more than that was graded as “difficult.” The number of attempts was noted, and it was considered a failure if the insertion was not successful in three attempts. The patient was then excluded from the study, and either a different size of the same device was inserted or the child was intubated with an endotracheal tube.

The device was fixed from maxilla to maxilla, and the cuff was inflated in the cLMA group using a cuff pressure monitor (Mallinckrodt Medical, Hennef, Germany) to achieve a pressure of 60 cm H₂O. This pressure was maintained throughout the surgery by continuous cuff pressure monitoring. A lubricated gastric tube was passed through the gastric channel in the i-gel group. The device was connected to a closed circle breathing system (Fabius^® plus anesthesia work station, Draeger, Germany) and an effective airway was defined by a square wave capnograph trace, normal chest movements, stable oxygen saturation (SpO₂) not less than 95%, and bilateral auscultation of the chest.

At the end of the surgery, anesthetic agents were discontinued and the device was removed after the child was awake. Any blood staining of the device or tongue–lip–dental trauma was documented immediately in the post-anesthesia care unit and 24 h later. The parents were also asked about sore throat, hoarse cry, or any other discomfort in the child's throat.

Monitoring devices (IntelliVue MP40™, Phillips) were attached to the patient including pulse oximeter and for measurement of non-invasive blood pressure. The following parameters were measured.

1. Hemodynamic parameters (heart rate and non-invasive blood pressure).

2. The OSP by closing the expiratory valve of the circle system at a fixed gas flow of 3 l/min, observing the airway pressure at which equilibrium was reached. At this point, gas leakage was heard at the mouth, at the epigastrium (epigastric auscultation) or coming out of the drainage tube (i-gel group). Manometric stability test was supposed to be the most reliable test.

3. Number of insertion attempts and ease of insertion.

4. Incidence of airway complications by these supraglottic devices:

   • Presence of blood on LMA
   • Tongue–lip–dental trauma
   • Sore throat, hoarse cry

Statistical analysis was done using SPSS software version 17.0 (SPSS Inc., Chicago, IL, USA). Sample size was based on a crossover pilot study of 10 patients and was selected to detect a projected difference of 30% between the groups for airway sealing pressure for a type 1 error 0.05 and a power of 0.8. The demographic data (age, weight, and height), the OSP, and hemodynamic data were analyzed by unpaired t-test. The insertion characteristics and complications were analyzed with Chi-square test. Unless otherwise stated, data are presented as mean (SD). A “P value” of <0.05 was considered statistically significant.

RESULTS

There was no significant difference in demographic data in the two groups [Table 1]. There were no failures in insertion of the airway in any group. The number of attempts of insertion was comparable and is shown in Table 2. Ease of insertion was similar in the i-gel and cLMA groups (no “difficult” insertion) [Table 2]. The mean arterial pressure (MAP), heart rate (HR), and SpO₂ were comparable in all patients.

Table 1.

Patient characteristics

Table 2.

Comparison in the two groups: i-gel, and LMA classic

There was neither desaturation nor any significant change in MAP and HR before and after insertion of airway in any case, as shown in Table 3. There was no laryngospasm in any patient.

Table 3.

Hemodynamic parameters

The OSP was 26.1 ± 2.4 and 22.64 ± 2.2 cm H₂O for the i-gel and cLMA groups, respectively, and the OSP was significantly higher in the i-gel group (P < 0.05).

Blood staining was observed in two cases in the cLMA group and in one case in the i-gel group. There was no incidence of sore throat or hoarse cry in any of the two groups.

DISCUSSION

The i-gel is a new single-use, noninflatable supraglottic airway for use in anesthesia during spontaneous or intermittent positive pressure ventilation.[4] The i-gel airway is an anatomically designed mask made of a gel-like thermoplastic elastomer with a soft durometer and gel-like feel.[5] The pediatric i-gel is a new smaller model of the well-known i-gel used in adult patients. It has a channel for gastric catheter placement, except for size 1. The soft, noninflatable cuff fits snugly onto the perilaryngeal framework, mirroring the shape of the epiglottis, aryepiglottic folds, piriform fossae, perithyroid, peri-cricoid, posterior cartilages and spaces. So, each structure receives an impression fit, thus supporting the seal by enveloping the laryngeal inlet. The seal created is sufficient for both spontaneously breathing as well as paralyzed patients. Studies in adults have been promising, showing an easy insertion, high airway leak pressures, and low complication rates with few postoperative complaints.[6,7,8,9,10]

In this study, we found that insertion of the i-gel was successful in the first attempt in 28 of 30 patients and comparable to 27 of 30 in cLMA group. A global study involving 50 children undergoing ventilation using the i-gel pediatric device was carried out over 2 months. In that study the success rate for inserting the device was 80% in the first attempt and 100% after two attempts.[11,12] Other studies of using the pediatric i-gel[13] and LMAs[14,15] have shown similar results. The ease of insertion was graded as “easy” or “very easy” in all the cases in the i-gel and the cLMA groups.

In our study, we found significant difference in OSP between cLMA and i-gel. Similar result had been observed in a study where average OSP in i-gel was found to be 24 cm H₂O, compared to 18-21 cm H₂O in cLMA.[16] On the other hand, Lee et al.[17] found no significant difference between i-gel and cLMA in children. Janakiraman et al.[18] measured OSP 17 cm H₂O and 20 cm H₂O in cLMA and i-gel group, respectively. The result of our study was further substantiated by the observation of the study by Goyal et al.[19] In this study, the authors found that OSP in the i-gel group (26 ± 2.63 cm H₂O) was significantly higher than in the cLMA group (22 ± 2.3 cm H₂O).

The incidence of complications (airway trauma and sore throat) was very low in all cases except for blood staining in a few children in the cLMA group, which was neither clinically important nor statistically significant. Other studies have also reported similar incidence.[13,14] Though i-gel inserts less pressure on perilaryngeal tissue because of its noninflatable cuff, the incidence of sore throat was comparable in all three groups. This observation of our study is supported by the study of Wong et al.[20] where they stated that sore throat could be minimal even with supraglottic devices with inflatable cuff, if the intracuff pressure remains less than 60 cm H₂O.

From our study, we conclude that size 2 i-gel is comparable to cLMA of the same size in terms of hemodynamic parameters, ease of insertion, and postoperative complications. OSP is the only parameter which is significantly higher in the i-gel group. Size 2 i-gel is equally safe, efficient, and cost effective in children, compared to other prototypical pediatric supraglottic airway devices. It has an added advantage of gastric channel which is found only in ProSeal LMA and LMA supreme™. Therefore, i-gel should be more frequently used in children in both elective surgeries and in procedures requiring anesthesia outside the operating room.