After approval from the Hospital Ethics Committee, 90 patients were studied. A randomized prospective study was planned to compare size 2 i-gel (Intersurgical Ltd., Wokingham, Berkshire, UK) with PLMA and 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 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. Ninety patients were equally randomized to one of the three groups (i-gel, PLMA 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 (introducer for PLMA, 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 Web site. Each device was inserted by an experienced anesthesiologist who had performed at least 50 size 2 cLMA or PLMA 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 PLMA and cLMA groups using a cuff pressure monitor (Mallinckrodt Medical, 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 and PLMA groups. 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 anaesthesia 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 Medical System, Eindhoven, Netherlands) were attached to the patient, including pulse oxymeter and noninvasive blood pressure. The following parameters were measured:
- Hemodynamic parameters (heart rate and noninvasive blood pressure).
- 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 (ProSeal and i-gel group). Manometric stability test was supposed to be the most reliable test.
- Number of insertion attempts and ease of insertion.
- Number of insertion attempts of gastric tube (ProSeal and i-gel groups).
- Incidence of airway complications by these supraglottic devices:
- Presence of blood on LMA
- Tongue-lip-dental trauma
- Sore throat, hoarse cry.
Statistical analysis was performed 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) were analyzed by ANOVA. The OSP and hemodynamic data were also compared using ANOVA. The insertion characteristics and complications were analyzed with chi-square test. Fisher's exact test was used to analyze the insertion attempts of gastric tube. Unless otherwise stated, data are presented as mean (SD). A P<0.05 was considered statistically significant.