TITLE: Comparison of i–gel™ and laryngeal mask airway in anesthetized paralyzed patients

  ABSTRACT.BACKGROUND:
The i-gelTM is a new device introduced recently. It differs from other supraglottic airway devices. It has a non-inflatable, gel-made cuff. Previously used devices, have some disadvantages which are claimed to be absent in i-gelTM. In this study we aimed to compare the performance of the laryngeal mask airway (LMA)-ClassicTM and i-gelTM during anesthesia in paralyzed patients.

ABSTRACT.MATERIALS AND METHODS:
A total of 64 anaesthetized patients with paralysis were enrolled in a single-blind, randomized control trial to be intubated with one of the devices. We compared the device insertion parameters, some ventilatory parameters, and adverse effects after device insertion.

ABSTRACT.RESULTS:
Vital signs were not significantly different between groups. Regarding duration of insertion attempts, the difference between groups was significant (P < 0.05); while the number of insertion attempts was insignificant (P = 0.265). There was no significant difference between both groups regarding postoperative complications (cough, sore throat, and blood on the cuff) (P > 0.05). Airway leak was assessed in both groups and data showed no significant difference (P = 0.662). Additionally, end-tidal CO2 change regarding the baseline value was significantly different after 10 and 15 min of anesthesia (P < 0.05).

ABSTRACT.CONCLUSIONS:
Successful insertion time was shorter significantly for i-gelTM. As i-gelTM has easy application, it is advantageous to be used during cardiopulmonary resuscitation by non-anesthetists in which time is very important. We concluded that i-gelTM can be an alternative to LMA-ClassicTM for controlled ventilation during anesthesia as it is easier to be placed.

BODY.INTRODUCTION:
Secure airway management in anesthesia is critical for appropriate treatment of respiratory complications and successful operation.[1] Successful transition of these devices through anatomical elements and their proper placement is vital.[2] Unsuccessful attempts for device insertion hurt anatomical elements including vocal cords and cricoid ring.[345] Approximately 15.5% attempts for device insertions are unsuccessful and 2% of respiratory events are due to inappropriate airway management.[67] Death or brain damage occurs in 85% of cases with failed tracheal intubation.[3]  Since 1988 laryngeal mask airway (LMA)-ClassicTM has been available and now it is popular and commonly used for airway management.[8] Eighty-nine percent successful intubation in patients is reported by LMA. Nevertheless, LMA is assumed one of the best devices for ventilation.[9] LMA-ClassicTM generally prepares a suitable airway. Nevertheless, its simple use is limited by factors including more than one attempt for device insertion, probability of stomach content aspiration, and air leakage especially during positive pressure ventilation.[10] Reasons mentioned above made scientists to invent a new device in order for airway management.[11]  i-gelTM (Intersurgical Ltd, Wokingham, UK) is a new single-use supraglottic airway device composed of non-inflatable, soft, gel-like mask.[12] This device isolates oropharyngeal opening from the laryngeal area.[101314] It consistently brings proper positioning for supraglottic ventilation and overcomes many disadvantages of LMA.[10] The i-gel has other useful characteristics; including a gastric channel and an epiglottic ridge. To reduce the risk of axial rotation, it has ridged flattened stem, which helps easier insertion as well.[14]  There are not enough studies on i-gel efficiency and superiority to LMA. We aimed to compare the efficiency and ease of insertion of i-gelTM and LMA-ClassicTM in paralyzed patients during anesthesia.

BODY.MATERIALS AND METHODS:
We designed a single-blind, randomized clinical trial which has been carried out from October 2009 to March 2010 in an educational hospital. After institutional review board and ethics committee approval (National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University), written informed consent was obtained from all subjects. We prospectively studied 64 patients who needed anesthesia for elective surgeries in which the operation took less than 2 h. We excluded patients with: Body Mass Index (BMI) >35; urgent surgery requirements; surgery in a non-supine position or oral or nasal surgery; preoperative sore throat; and history of stomach regurgitation, heart burn, ileums, respiratory and cardiac diseases, which can result in lung capacity reduction or increased airway resistance, laryngeal or pharyngeal malformation or pathologies, cervical vertebral disorders which prevents freely head movements, airway obstructions in pharyngeal area, unsuitable conditions for surgery by application of a laryngeal mask and class of III-V physical status as American Society of Anesthesiologists instituted. Using computer-generated tables of random numbers, patients were allocated into two groups: LMA-ClassicTM and i-gelTM.  Patients' demographic data and clinical conditions obtained by means of examinations and interview and entered in standard forms. Successful insertion time, number of tries for device insertion, reaching reasonable airway, air leakage, O2 saturation, end tidal CO2, peak airway pressure (PAP), plateau pressure (Pplateau), tidal volume expiratory (TVe), and in situ device duration were filled in the forms. Devices were inserted for orthopedics surgeries with above-mentioned criteria. Patients were blind to the type of the device applied. However, they were signed the consent to be intubated by one of the mentioned devices. The LMA-ClassicTM masks were routinely used in studied hospital and i-gelTM was the new one which was not used until our study was carried out. All insertions in both groups were carried out by the same anesthesiologist to prevent bias.  During the operation we measured some vital parameters including heart rate, electrocardiogram, arterial blood pressure (noninvasive), peripheral oxygen saturation (pulse oximetry), respiratory rate, capnography, and tidal volume.  Before procedure, the anesthesia machine was assessed regarding to leakage. The tip of the laryngeal mask and its posterior part was lubricated with a lubricant containing 2% lidocaine. Before insertion, the cuff was inflated to the pressure less than 44 mmHg which is recommended by manufacturer and previous reports to decrease the incidence of postoperative pharyngolaryngeal complications.[15161718]  For i-gelTM we lubricated the front, back, and sides of the non-inflatable cuff, as manufacturer instruction mentioned, with the same lubricant. For both the devices; sizes 3, 4, and 5 were used.  Anesthesia method was the same in all patients. Induction of anesthesia was started in supine posture using a standard pillow. Midazolam 25 μg/kg and fentanyl 1-1.5 μg/kg were prescribed as premedication and anesthesia induced by 3-5 mg/kg thiopental and atracurium 0.4 mg/kg (as a muscle relaxant). Manual preoxygenation for 3-5 min carried out before airway management. Anesthesia apparatus settings were tidal volume 8-10 cc/kg and 10-12 breaths/min for all patients. For anesthesia maintenance, propofol 50-75 μg/kg/min, N2O 50%, and atracurium 10 mg repeated each 20 min.  The attempts for laryngeal mask insertion was started after completion of anesthesia and observing loss of lash reflex and the jaw relaxation, like routine intubations.[19] The lubricated device were entered patient's mouth in 'sniffing the morning air' position. Then it directed and glided downwards and backwards. When a certain resistance was felt, it was considered as a complete insertion procedure and the device was connected to ventilation circuit.  Insertion easiness of the devices was categorized as: 1) First attempt insertion easily with no resistance, 2) first attempt insertion easily with little resistance, 3) difficult insertion and successful at the second attempt, and 4) unsuccessful attempts.  Before spontaneous breathing resumption, ventilation was performed manually. After fixing the laryngeal mask, the seal of the larynx area by the LMA-ClassicTM and i-gelTM was checked for any air leakage. The expiratory valve was closed at a gas flow of 3 L/min and airway pressure at which the gas leakage felt was recorded.[1320] Oropharyngeal leak pressure was measured with the flow rate of 3 L/min.  The achievement of proper placement was confirmed by chest movement bilaterally and symmetrically, square waveform on capnograph and normal SpO2 (>95%) and finally with a fiberoptic bronchoscopy assessment. The device was fixed to the mouth using adhesive tape.[13] In the case of ineffective airway, we did manipulations (e.g., chin lift, changing size of the device, etc).  We considered occurrences of any regurgitation or aspiration and laryngeal spasm or other any unwanted events.  At the end of surgery, nitrous oxide and propofol were discontinued. When the patients' reflexes had returned to normal, the LMA-ClassicTM and i-gelTM were removed regarding factors that can provoke laryngeal spasms like secretions.[21] On device removal, the presence of blood was noticed. We inspected the patient to prevent any injury to the lips, teeth, or tongue during recovery from anesthesia. Prospective evaluations including cough, feeling of sore throat at 2 and 24 h after surgery were done.

BODY.MATERIALS AND METHODS.STATISTICAL ANALYSIS:
In a preliminary study, the incidence of at least one side effect was estimated 90% in LMA-ClassicTM and 60% in i-gelTM groups; and the required sample size was calculated for power = 80% and α =0.05 and difference between two groups (d = 30%) based on our preliminary study as 32 patient in each group. The quantitative variables were described as mean ± standard deviation (SD); and the qualitative variables were demonstrated as n (%). For comparison of variables between two groups, Student's t-test was used for quantitative variables and nonparametric Mann-Whitney test, if it was necessary. Also for comparing the qualitative variables between two groups, the Chi-square and Fisher's exact tests were used. All of the hypothesis tests were two-tailed and the significance level was 0.05 for all statistical tests.

BODY.RESULTS:
Our screening resulted in 64 patients, 33 (51.6%) male and 31 (48.4%) female, who were eligible to participate in the study. Patients were assigned randomly into groups of LMA-ClassicTM and i-gelTM (n = 32). The mean age of patients in LMA-ClassicTM group was 65.6 ± 12.9; and for patients in i-gelTM group was 60.7 ± 12.1 (P = 0.127). Comparing sex ratio between two groups did not show any significant difference (P = 0.080) [Table 1].   Table 1 Comparing LMA with i-Gel   There was no statistically significant difference in BMI between groups (P > 0.05) [Table 1].  Mean operation time was 42-55 min and mean anesthesia time was 43-112 min.  Vital signs did not differ significantly throughout the study regarding the device type and all cases had acceptable chest wall movement. There was no statistically significant difference regarding heart rate and systolic and diastolic blood pressure.  The difference between both groups regarding insertion time was statistically significant (P < 0.05) (14.93 ± 4.6 s in i-gelTM vs 27.1 ± 16.7 s in LMA-ClassicTM) [Figure 1]. Whereas, the frequency of trials had the mean of 1.3 ± 0.6 and 1.6 ± 1.3, respectively in LMA-ClassicTM and i-gelTM groups (P = 0.265). Moreover, the number of displacement for adequate ventilation was not significantly different between LMA-ClassicTM and i-gelTM groups (1.4 ± 1.1 vs 1.2 ± 1.4; P = 0.270). Frequency of gastric reflux was significantly higher with LMA-ClassicTM (P < 0.05). Airway leak was assessed in both groups and data showed no significant difference (P = 0.662).  Figure 1Comparison of insertion time between i-gel and laryngeal mask airway (LMA)  Furthermore, different side effects were compared between mentioned groups. Twenty-six (81.2%) out of LMA-ClassicTM patients and 19 (59.4%) out of i-gelTM patients had at least one side effect after surgery (P = 0.055); from which three (9.4%) and two (6.2%) had blood on cuff (P > 0.999); and five (15.6%) and four (12.5%) had postoperative cough (P > 0.999) in LMA-ClassicTM and i-gelTM group, respectively [Figure 2]. Mean of postoperative sore throat regarding visual analog scale (VAS) index in recovery in i-gelTM and LMA-ClassicTM groups were 1.1 ± 1.1 and 1.1 ± 1.3, respectively (P = 0.788); and it did not show any significant difference at 24 h after surgery (0.2 ± 0.5 for LMA-ClassicTM and 0.1 ± 0.5 for i-gelTM group; P = 0.665). Also, the mean of odynophagia on first swallowing (VAS) was 2.1 ± 2.7 and 1.1 ± 1.3 in two groups (P = 0.268), respectively.  Figure 2Comparison of frequency of postoperative complications including bloody cuff, cough, and sore throat between i-gel and LMA  The difference of O2 saturation and end-tidal CO2 at 1, 5, 10, and 15 min, with the baseline values (measured at 1 min before securing the airway) were calculated for each patient. The comparison of O2 saturation between LMA-ClassicTM and i-gelTM groups did not show any significant difference, as well (all P > 0.05). Nevertheless, the change of end-tidal CO2 from the baseline was different between two groups at 10 and 15 min after insertion; as the means of differences were 0.6 ± 2.7 and 0.9 ± 2.7 units less than baseline value, at 10 and 15 min, respectively in LMA-ClassicTM group; and 1.4 ± 3.8 and 0.8 ± 4.4 units in i-gelTM group.  Accordingly, TVe, PAP, and Pplateau were compared at 3, 5, 10, 15, 30, and 50 min after insertion, between LMA-ClassicTM and i-gelTM groups. Comparisons did not show any statistically significant differences.

BODY.DISCUSSION:
In this clinical trial study, we compared advantages and disadvantages of two supraglottic airway, the i-gel and LMA. We concluded that both devices provide an acceptable airway with preservation of hemodynamics and oxygen saturation. They have similar clinical performances in anesthetized paralyzed patients. In our study, patients showed no significant differences in age and sex between i-gelTM and LMA-ClassicTM. The sizes of insertion devices were not different significantly in groups.  Postoperative complications are one of the important parameters for comparing supraglottic devices. Postoperative complications and their severity including cough, sore throat, and blood on cuff (airway trauma) were the same in comparison. Against our results, minor complications reported for i-gelTM. However, consistent with our results, Richez et al.,[22] found no significant gastrointestinal complication for i-gelTM. i-gelTM comparably protects against aspiration better than LMA-ClassicTM.  Considering the hemodynamic parameters, no statistically significant difference was reported regarding heart rate and systolic and diastolic arterial blood pressure during the ventilation period. Atef et al.,[12] reported acceptable hemodynamic stability with both devices, which is in accordance with our results.  Acott[23] used i-gelTM as an airway device in general anesthesia and assessed the performance of the device. In agreement with our findings, they reported that a single attempt was required for insertion in most of the patients. All the insertion times of their study were less than 10 s, our times were more than 10 s, though.  i-gelTM has advantages and disadvantages over other supraglottic airways. It may be recommended for applying by non-anesthetists during cardiopulmonary resuscitation. It does not have inflatable cuff and this makes it easier to use. It has a drain tube which prepares access to the gastrointestinal tract and reduces the risk of reflux and regurgitation.[24]  In accordance with our study, Levitan and Cook imply that there were no statistical difference between i-gelTM and LMA-ClassicTM. In addition, Shin et al., found no difference in leak pressure between i-gelTM and LMA-ClassicTM which is similar to our findings.[25] This indicates that i-gelTM does not prepare better seal and fits as well as LMA-ClassicTM on supraglottic opening.  Objective indexes showed no differences in i-gelTM and LMA-ClassicTM groups except end-tidal CO2 which showed significant difference from baseline and 10 and 15 min after insertion. These findings suggest weaker ventilation prepared by i-gelTM in comparison with LMA-ClassicTM.  There are some limitations for our study. Initially, we studied only low risk patients (American Society of Anesthesiologists (ASA) I and II) with normal airways and low BMI. Next point is, like other studies, this investigation was carried out with low sample size.

BODY.CONCLUSION:
Both LMA-ClassicTM and i-gelTM do not alter hemodynamic status of the patients significantly. The insertion attempts and leak pressure were not significantly different in i-gelTM and LMA-ClassicTM groups. Our study suggested that although, i-gelTM prepares lower ventilation, it is a suitable device for insertion of patients who need general anesthesia. Easy application and low price of the device could introduce i-gel as a proper replacement of LMA. However, further investigations are needed to determine pros and cons of i-gelTM and to evaluate the applicability of the device.

Question: Compared to Laryngeal mask airway what was the result of i–gelTM on Airway leak?
Evidence: Frequency of gastric reflux was significantly higher with LMA-ClassicTM (P < 0.05).
Answer: no significant difference