Anaesthesia 2014, 69, 362–367
doi:10.1111/anae.12592
Original Article A randomised comparison of the i-gelTM and the Laryngeal Mask Airway ClassicTM in infants M.-S. Kim,1 J.-T. Oh,2 J. Y. Min,3 K.-H. Lee4 and J.-R. Lee5 1 Clinical Assistant Professor, 3 Fellow, 4 Resident, 5 Assistant Professor, Department of Anaesthesiology and Pain Medicine, Anaesthesia and Pain Research Institute, 2 Professor, Department of Paediatric Surgery, Severance Children’s Hospital, Yonsei University College of Medicine, Seoul, Korea
Summary We performed a randomised comparison of the i-gelTM and the Laryngeal Mask Airway (LMA) ClassicTM in children aged less than a year who were undergoing general anaesthesia for elective surgery. Fifty-four infants were randomly allocated to either the i-gel or the LMA Classic. We measured performance characteristics, fibreoptic views through the device and complications. Success rate at first insertion attempt was 100% (27/27) in the i-gel group compared with 88% (23/26) in the LMA Classic group. Insertion of the device was considered easy in 26/27 (96%) patients in the i-gel group compared with 18/26 (69%) patients in the LMA Classic group (p = 0.009). There were no differences between the groups in insertion times, fibreoptic views through the device, airway leak pressures or complications. We conclude that the i-gel was considered easier to insert than the LMA Classic in infants. .................................................................................................................................................................
Correspondence to: J.-R. Lee Email: [email protected] Accepted: 22 December 2013
Introduction The laryngeal mask airway (LMA) ClassicTM (Laryngeal Mask Company Ltd, Henley-on-Thames, UK) was introduced into clinical practice as a first-generation supraglottic airway device in 1983 [1]. Since then, it has gained popularity for airway management in both anaesthesia and resuscitation due to its ease of use [1–3]. However, insertion of the LMA Classic is not always easy in children due to differences in airway anatomy compared with adults [2] and more complications are related to its use in younger children compared with adults [4, 5]. The i-gelTM (Intersurgical Ltd, Workingham, UK) is a disposable supraglottic airway device with a noninflatable cuff made of thermoplastic elastomer gel that eliminates the need for cuff inflation and therefore 362
prevents potential complications related to high intracuff pressures. In addition, it has a symmetrical, widened, elliptical and laterally flattened stem which may result in easier insertion and improved stabilisation during maintenance of anaesthesia [6, 7]. These features of the i-gel may be particularly beneficial in children. Previous studies in children have demonstrated that the i-gel is easy to insert with a high first attempt insertion success rate, a quick insertion time and favourable fibreoptic views of the glottis through the device. However, these studies included children of wide age range as well as different sized devices [6, 7]. There is little evidence available regarding the use of supraglottic airway devices in children less than a year old and we decided to compare the i-gel with the LMA Classic in infants undergoing general anaesthesia. © 2014 The Association of Anaesthetists of Great Britain and Ireland
Kim et al. | i-gel vs LMA Classic in infants
Methods This study was approved by the Local Research Ethics Committee and written informed consent was obtained from the parents or legal guardians of all the patients. Children less than 12 months of age, weighing less than 10 kg, of ASA physical status 1 or 2 who were scheduled for elective surgery were enrolled in the study. Exclusion criteria included a history of pre-maturity, congenital airway abnormalities, clinically significant upper respiratory tract infections or increased risk of aspiration. No premedication was administered but local anaesthetic cream had been applied to the skin of the hands and antecubital fossae. On arrival in the anaesthetic room the patients were positioned supine and a small roll was placed underneath the neck. Monitoring, in the form of pulse oximetry, electrocardiography and non-invasive blood pressure was attached. An intravenous cannula was inserted and anaesthesia was induced with propofol 2 mg.kg 1 combined with sevoflurane 3– 4% in a 50:50 mixture of oxygen and air. No neuromuscular blocking agents were administered. Adequate anaesthetic depth for insertion of the supraglottic airway device was confirmed by absence of movement in response to a jaw thrust [8]. Patients were randomly allocated to either the i-gel or the LMA Classic using a random number sequence created by an internet website (http://www. random.org/). The random sequence was kept in sealed, opaque envelopes that were opened by an observer just before induction of anaesthesia. The size of each device was selected in accordance with the manufacturer’s guidelines (size 1 for children less than 5 kg in weight and size 1.5 for those weighing between 5 and 10 kg). When inserting the LMA Classic, the cuff was partially inflated in order to reduce insertion time and improve success rate [1, 2, 9]. All devices were inserted by anaesthetists with paediatric experience who had inserted each device on at least 100 occasions. Both devices were inserted according to the manufacturers’ instructions and successful insertion was defined as the observation of symmetrical chest wall movement and a square-wave capnograph trace. Following two failed insertion attempts, the anaesthetist controlled the airway according to his/her own
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Anaesthesia 2014, 69, 362–367
preference and the patient was withdrawn from the study. Insertion time was defined as the time from when the device was picked up until appearance of the first wave on the capnograph trace. Ease of insertion was evaluated using a subjective grading score between 1 and 4 (1, no resistance; 2, mild resistance; 3, moderate resistance; 4, inability to insert the device) [6]. Manipulations required to improve the position of the device, such as changing insertion depth, performing a jaw thrust manoeuvre or extension/flexion of the head were recorded. After insertion of the device, mechanical ventilation of the lungs was commenced and the intracuff pressure of the LMA Classic was set at 40 cmH2O and monitored using a cuff pressure manometer (Mallinckrodt Medical, Athlone, Ireland) [10]. Airway leak pressure was determined by setting the adjustable pressure-limiting (APL) valve to 30 cmH2O and the fresh gas flow rate to 3 l.min 1. Oropharyngeal leak pressure was defined as the point at which equilibrium was attained [6, 9]. When measuring oropharyngeal leak pressure, auscultation over the epigastrium was performed to detect the presence or absence of gastric insufflation. Leak volume was defined as the difference between the inspiratory and expiratory tidal volume and obtained from spirometry on a PrimusTM anaesthetic workstation (Dr€ager, L€ ubeck, Germany). Leakage fraction was the leak volume divided by the inspiratory tidal volume. Five measurements were performed and the average was recorded. Peak inspiratory pressures were also noted. The anatomical position of the device in relation to the glottis was assessed by inserting a fibreoptic bronchoscope (Olympus Optical Co., Tokyo, Japan) through the device. The image was graded using a scale between 1 and 4 (1, vocal cords not visible; 2, vocal cords and anterior epiglottis visible; 3, vocal cords and posterior epiglottis visible; 4, vocal cords visible) [6]. After completion of surgery the patient was transferred to the recovery area and the supraglottic airway device was removed when the patient regained consciousness. Sample size calculation was based on oropharyngeal leak pressure as the primary outcome. Previous studies have demonstrated that the standard deviation of
363
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airway leak pressure of the i-gel and the LMA Classic in children is approximately 6 cmH2O [11, 12]. Assuming a 5% two-tailed significance level (a = 0.05) and power of 80% (b = 0.20), a sample size of 23 patients in each group would be required to detect a difference of 5 cmH2O between the i-gel group and the LMA Classic group.[12] Twenty-seven children in each group were included to allow for a 10% dropout rate. The Kolmogorov–Smirnov test was used to determine the distribution of all continuous variables. Student’s t-test was used for normally distributed data and Mann– Whitney U-test for continuous variables not normally distributed. Chi-squared test or Fisher’s exact test was used to analyse frequency variables and ordinal variables were analysed using the Mann–Whitney U-test. Data were analysed using SPSS version 18 software (SPSS Inc., Chicago, IL, USA) and a p value of < 0.05 was considered statistically significant.
Results Out of the 55 patients eligible for inclusion in the study, 54 patients were enrolled and one was not studied due to refusal of informed consent. One of the patients who was initially included in the study was withdrawn from the LMA Classic group due to the
Kim et al. | i-gel vs LMA Classic in infants
presence of excessive secretions at induction of anaesthesia and 53 patients completed the study (Fig. 1). The baseline characteristics of patients included in the study are shown in Table 1. Device insertion characteristics are shown in Table 2. Both devices were placed successfully in all patients, although it took two attempts to place the LMA Classic in three patients. In one patient, weighing 5.7 kg, the first attempt with a size-1.5 LMA Classic failed and the second attempt using a size-1 LMA Classic succeeded. Median insertion time for the i-gel group was the same as for the LMA Classic group, but insertion of the i-gel was considered significantly easier compared with the LMA Classic (p = 0.009). Manipulation of the device was required less often in the i-gel group compared with the LMA Classic group but this did not reach statistical significance; most manipulations consisted of slight withdrawal of the device following insertion. Good fibreoptic views were obtained through the i-gel in 63% of patients compared with 42% of patients in the LMA Classic group. There was no significant difference in airway leak pressures between the groups and gastric insufflation was similar with both devices. There were no statistically significant differences in ventilation parameters (Table 3).
Figure 1 CONSORT flow diagram to illustrate the study design. 364
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Kim et al. | i-gel vs LMA Classic in infants
Anaesthesia 2014, 69, 362–367
Table 1 Baseline characterisitics of the patients undergoing anaesthesia with the i-gel or LMA Classic. Values are median (IQR [range]), number (proportion) or mean (SD).
Age; months Male:female Weight; kg Height; cm
Device size 1 1.5 Operation time; min Anaesthesia time; min
Table 3 Device performance and ventilatory parameters in patients undergoing anaesthesia with the i-gel or LMA Classic. Values are median (IQR [range]) or number (proportion).
i-gel (n = 27)
LMA Classic (n = 26)
3.0 (1.6–8.0 [1.2–11.0]) 20:7 5.7 (4.5–8.7 [3.4–9.9]) 58.0 (53.4–71.5 [48.6–74.9])
2.9 (2.0–7.3 [1.0–11]) 22:4 5.7 (4.9–7.5 [3.7–9.5]) 59.7 (55.0–62.6 [50.5–77.3])
Airway leak pressure; cmH2O Number of gastric insufflations Peak inspiratory pressure; cmH2O Leak volume; ml
13 (48%) 14 (52%) 43.8 (22.6) 72.7 (22.4)
9 (35%) 17 (65%) 41.6 (17.6) 73.8 (19.1)
Leak fraction; %
Table 2 Insertion characteristics in patients undergoing anaesthesia with the i-gel or LMA Classic. Values are number (proportion) or median (IQR [range]). i-gel group (n = 27) Successful 27 (100%) insertion of device at first attempt Ease of device insertion* 1 26 (96%) 2 1 (4%) 3 0 4 0 Insertion 15 (13–16 time; s [9–22]) Number of 0 manipulations required Fibreoptic view through device† 1 2 (7%) 2 8 (30%) 3 12 (44%) 4 5 (19%)
LMA Classic group (n = 26)
p value
23 (88%)
NS
i-gel (n = 27)
LMA Classic (n = 26)
25 (21–28 [17–30]) 8 (30%)
26 (22–30 [18–30]) 7 (27%)
15 (13–17 [8–25]) 2.1 (0.3–4.0 [0.0–7.6]) 4.0 (0.3–6.4 [0.0–13.7])
15 (13–17 [7–30]) 0.6 (0.0–2.4 [0.0–7.8]) 1.2 (0.0–4.2 [0.0–11.0])
p value NS NS NS NS
NS
(two in the i-gel group and one in the LMA Classic group) during emergence from anaesthesia. No airway obstruction episodes resulted in hypoxia and they were all resolved by the anaesthetist without requiring invasive airway management. There were no devices with blood staining or obvious trauma to the upper airway following removal of the device.
Discussion 18 (69%) 5 (19%) 3 (12%) 0 17 (12–18 [9–69]) 4 (15%)
2 13 3 8
(8%) (50%) (12%) (30%)
0.009
NS NS
NS
*Ease of insertion was graded as 1: no resistance, 2: mild resistance, 3: moderate resistance, 4: inability to place the device. †Fibreoptic view was graded as 1: vocal cords not visible; 2: vocal cords with anterior epiglottis visible; 3: vocal cords with posterior epiglottis visible; 4: vocal cords visible.
Airway obstruction occurred in two patients (one in the i-gel group and one in the LMA Classic group) during the intra-operative period and in three patients © 2014 The Association of Anaesthetists of Great Britain and Ireland
Although the i-gel has been extensively studied in older children and adults and is generally regarded as a viable alternative to the LMA Classic, the devices have not been previously compared in children less than one year old. In very young children, the risk of adverse respiratory events is higher during general anaesthesia because the physiology of infants differs significantly from that of adults [13]. In addition, anatomical differences compared with adults may lead to difficulties with device insertion in this young age group. In this study, which only included children less than a year old, there was a higher first attempt insertion success rate with the i-gel than the LMA Classic. Although this did not reach statistical significance, the operators found that that the i-gel could be inserted more easily, and required less subsequent manipulation, compared with the LMA Classic. The first observational study of the paediatric i-gel by Beylacq et al. [11] demonstrated that the i-gel could be inserted very easily in most cases (90%) and no experience was required to obtain a high first attempt 365
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success rate. Recent paediatric resuscitation simulation scenarios revealed that all participants, whatever their level of experience with paediatric airway care, could place the i-gel successfully at first attempt [14]. In a previous study comparing the i-gel with the LMA Classic in children, the i-gel was inserted more quickly than the LMA Classic, which was inserted using Brain’s technique and a fully deflated cuff [6]. In our study, the LMA Classic was inserted with a partially inflated cuff which we anticipated would result in easier insertion and reduced cuff inflation times after insertion. In addition, experienced anaesthetists, rather than novices, participated in our study. As a result, median insertion times for the two devices were similar, at approximately 16 s. Schunk et al. [14] found that insertion time for the i-gel was significantly shorter than for the LMA Unique (even with a partially inflated cuff) in all professional groups, including inexperienced physicians and paramedics. Based on these results, it is reasonable to assume that the i-gel can be inserted more easily and quickly, with higher success rates at first insertion attempt, regardless of experience. Given these features, the i-gel could be a valuable tool for airway management in infants, who have limited oxygen reserves during periods of apnoea [13]. Oropharyngeal leak pressure is defined as the airway pressure at which air leaks into the mouth or enters the stomach [15]. This feature is the most common primary outcome used to evaluate the safety and efficacy of supraglottic airway devices because high pressures generally indicate that adequate ventilation can be achieved without air leakage during positive pressure ventilation at high inspiratory pressures [16]. In infants, the use of a supraglottic airway device with a high oropharyngeal leak pressure is beneficial because high inspiratory pressure is required during positive pressure ventilation due to reduced lung compliance and increased airway resistance [5, 13]. In our study, oropharyngeal leak pressures were similar in both the i-gel group and the LMA Classic group and agreed with those reported in previous studies [6, 15]. The LMA Classic necessitates the use of a cuff pressure manometer in order to maintain appropriate intracuff pressure for optimum airway sealing, whereas the i-gel does not require cuff inflation or cuff pressure adjustments [9, 17]. This suggests that the i-gel 366
Kim et al. | i-gel vs LMA Classic in infants
may be more useful in clinical situations when cuff pressure manometers are not available. Fibreoptic views are frequently used to assess the anatomical position of supraglottic airway devices following insertion and to make comparisons between devices [5, 6]. In the present study, the i-gel resulted in improved views of the vocal cords (a score of 3 or 4) compared with the LMA Classic, although the differences did not reach statistical significance. Lee et al. found that the i-gel resulted in a significantly better fibreoptic view compared with the LMA Classic [6]. However, a poor view of the glottis does not necessarily mean that the airway is obstructed or that there is a lower oropharyngeal leak pressure [15, 18]. Nevertheless, airway obstruction due to a down-folded epiglottis may result in an increase in inspiratory pressure during positive pressure ventilation when small supraglottic airway devices are in situ [5], and an improved view such as that obtained with the i-gel ensures airway patency with adequate ventilation and indicates that there is an unobstructed conduit for tracheal tube insertion through the device, if required [6, 15]. Another issue related to supraglottic airway devices in infants is delayed airway obstruction. Previous studies demonstrated that this occurred more frequently in infants and was related to movement of the device intra-operatively [4]. In our study, anaesthesia was maintained at a deep level in order to avoid unnecessary movement of the patient, and thus delayed airway obstruction was infrequent. In clinical situations, where the patient is more likely to move, the i-gel may prove a better choice than the LMA Classic due to its buccal cavity stabiliser which has been designed to reduce device movement [15]. Our study has several limitations. First, the number of patients, particularly those receiving the size-1 LMA Classic, was relatively small. Tracheal intubation is usually preferred in small babies due to the potential for complications associated with supraglottic airway devices [15] and so recruiting large numbers of patients for our study was not possible. Second, we could not assess postoperative complications such as sore throat or dysphagia because infants are unable to report complications. However, complications have been shown to be relatively uncommon in previous studies in older children and were not likely to be an © 2014 The Association of Anaesthetists of Great Britain and Ireland
Kim et al. | i-gel vs LMA Classic in infants
issue in our study [6]. Third, all the anaesthetists were experienced in insertion of both devices and it was not feasible to include novice participants. In conclusion, the i-gel was easier to insert than the LMA Classic in infants requiring general anaesthesia and it may be the supraglottic airway device of choice for this group of patients. Further studies comparing the i-gel with other supraglottic devices should be performed in order to determine the best supraglottic airway device for children less than a year old.
Competing interests No external funding and no competing interests declared.
References 1. O’Neill B, Templeton JJ, Caramico L, Schreiner MS. The laryngeal mask airway in pediatric patients: factors affecting ease of use during insertion and emergence. Anesthesia and Analgesia 1994; 78: 659–62. 2. Ghai B, Wig J. Comparison of different techniques of laryngeal mask placement in children. Current Opinion in Anesthesiology 2009; 22: 400–4. 3. Chen L, Hsiao AL. Randomized trial of endotracheal tube versus laryngeal mask airway in simulated prehospital pediatric arrest. Pediatrics 2008; 122: e294–7. 4. Mizushima A, Wardall GJ, Simpson DL. The laryngeal mask airway in infants. Anaesthesia 1992; 47: 849–51. 5. Park C, Bahk JH, Ahn WS, Do SH, Lee KH. The laryngeal mask airway in infants and children. Canadian Journal of Anesthesia 2001; 48: 413–7. 6. Lee JR, Kim MS, Kim JT, et al. A randomised trial comparing the i-gel(TM) with the LMA Classic (TM) in children. Anaesthesia 2012; 67: 606–11. 7. Beringer RM, Kelly F, Cook TM, et al. A cohort evaluation of the paediatric i-gel(TM) airway during anaesthesia in 120 children. Anaesthesia 2011; 66: 1121–6.
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Anaesthesia 2014, 69, 362–367 8. Drage MP, Nunez J, Vaughan RS, Asai T. Jaw thrusting as a clinical test to assess the adequate depth of anaesthesia for insertion of the laryngeal mask. Anaesthesia 1996; 51: 1167– 70. 9. Kim MS, Bai SJ, Oh JT, Youm SM, Lee JR. Comparison of 2 cuff inflation methods before insertion of laryngeal mask airway for safe use without cuff manometer in children. American Journal of Emergency Medicine 2013; 31: 346–52. 10. Hockings L, Heaney M, Chambers NA, Erb TO, von UngernSternberg BS. Reduced air leakage by adjusting the cuff pressure in pediatric laryngeal mask airways during spontaneous ventilation. Pediatric Anesthesia 2010; 20: 313–7. 11. Beylacq L, Bordes M, Semjen F, Cros AM. The i-gel, a singleuse supraglottic airway device with a non-inflatable cuff and an esophageal vent: an observational study in children. Acta Anaesthesiologica Scandinavica 2009; 53: 376–9. 12. Micaglio M, Bonato R, De Nardin M, et al. Prospective, randomized comparison of ProSeal and Classic laryngeal mask airways in anaesthetized neonates and infants. British Journal of Anaesthesia 2009; 103: 263–7. 13. McNiece WL, Dierdorf SF. The pediatric airway. Seminars in Pediatric Surgery 2004; 13: 152–65. 14. Schunk D, Ritzka M, Graf B, Trabold B. A comparison of three supraglottic airway devices used by healthcare professionals during paediatric resuscitation simulation. Emergency Medicine Journal 2013; 30: 754–7. 15. Hughes C, Place K, Berg S, Mason D. A clinical evaluation of the i-gel supraglottic airway device in children. Pediatric Anesthesia 2012; 22: 765–71. 16. Teoh WH, Lee KM, Suhitharan T, Yahaya Z, Teo MM, Sia AT. Comparison of the LMA Supreme vs the i-gel in paralysed patients undergoing gynaecological laparoscopic surgery with controlled ventilation. Anaesthesia 2010; 65: 1173–9. 17. Licina A, Chambers NA, Hullett B, Erb TO, von Ungern-Sternberg BS. Lower cuff pressures improve the seal of pediatric laryngeal mask airways. Pediatric Anesthesia 2008; 18: 952– 6. 18. Inagawa G, Okuda K, Miwa T, Hiroki K. Higher airway seal does not imply adequate positioning of laryngeal mask airways in paediatric patients. Pediatric Anesthesia 2002; 12: 322–6.
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doi:10.1111/anae.12592
Original Article A randomised comparison of the i-gelTM and the Laryngeal Mask Airway ClassicTM in infants M.-S. Kim,1 J.-T. Oh,2 J. Y. Min,3 K.-H. Lee4 and J.-R. Lee5 1 Clinical Assistant Professor, 3 Fellow, 4 Resident, 5 Assistant Professor, Department of Anaesthesiology and Pain Medicine, Anaesthesia and Pain Research Institute, 2 Professor, Department of Paediatric Surgery, Severance Children’s Hospital, Yonsei University College of Medicine, Seoul, Korea
Summary We performed a randomised comparison of the i-gelTM and the Laryngeal Mask Airway (LMA) ClassicTM in children aged less than a year who were undergoing general anaesthesia for elective surgery. Fifty-four infants were randomly allocated to either the i-gel or the LMA Classic. We measured performance characteristics, fibreoptic views through the device and complications. Success rate at first insertion attempt was 100% (27/27) in the i-gel group compared with 88% (23/26) in the LMA Classic group. Insertion of the device was considered easy in 26/27 (96%) patients in the i-gel group compared with 18/26 (69%) patients in the LMA Classic group (p = 0.009). There were no differences between the groups in insertion times, fibreoptic views through the device, airway leak pressures or complications. We conclude that the i-gel was considered easier to insert than the LMA Classic in infants. .................................................................................................................................................................
Correspondence to: J.-R. Lee Email: [email protected] Accepted: 22 December 2013
Introduction The laryngeal mask airway (LMA) ClassicTM (Laryngeal Mask Company Ltd, Henley-on-Thames, UK) was introduced into clinical practice as a first-generation supraglottic airway device in 1983 [1]. Since then, it has gained popularity for airway management in both anaesthesia and resuscitation due to its ease of use [1–3]. However, insertion of the LMA Classic is not always easy in children due to differences in airway anatomy compared with adults [2] and more complications are related to its use in younger children compared with adults [4, 5]. The i-gelTM (Intersurgical Ltd, Workingham, UK) is a disposable supraglottic airway device with a noninflatable cuff made of thermoplastic elastomer gel that eliminates the need for cuff inflation and therefore 362
prevents potential complications related to high intracuff pressures. In addition, it has a symmetrical, widened, elliptical and laterally flattened stem which may result in easier insertion and improved stabilisation during maintenance of anaesthesia [6, 7]. These features of the i-gel may be particularly beneficial in children. Previous studies in children have demonstrated that the i-gel is easy to insert with a high first attempt insertion success rate, a quick insertion time and favourable fibreoptic views of the glottis through the device. However, these studies included children of wide age range as well as different sized devices [6, 7]. There is little evidence available regarding the use of supraglottic airway devices in children less than a year old and we decided to compare the i-gel with the LMA Classic in infants undergoing general anaesthesia. © 2014 The Association of Anaesthetists of Great Britain and Ireland
Kim et al. | i-gel vs LMA Classic in infants
Methods This study was approved by the Local Research Ethics Committee and written informed consent was obtained from the parents or legal guardians of all the patients. Children less than 12 months of age, weighing less than 10 kg, of ASA physical status 1 or 2 who were scheduled for elective surgery were enrolled in the study. Exclusion criteria included a history of pre-maturity, congenital airway abnormalities, clinically significant upper respiratory tract infections or increased risk of aspiration. No premedication was administered but local anaesthetic cream had been applied to the skin of the hands and antecubital fossae. On arrival in the anaesthetic room the patients were positioned supine and a small roll was placed underneath the neck. Monitoring, in the form of pulse oximetry, electrocardiography and non-invasive blood pressure was attached. An intravenous cannula was inserted and anaesthesia was induced with propofol 2 mg.kg 1 combined with sevoflurane 3– 4% in a 50:50 mixture of oxygen and air. No neuromuscular blocking agents were administered. Adequate anaesthetic depth for insertion of the supraglottic airway device was confirmed by absence of movement in response to a jaw thrust [8]. Patients were randomly allocated to either the i-gel or the LMA Classic using a random number sequence created by an internet website (http://www. random.org/). The random sequence was kept in sealed, opaque envelopes that were opened by an observer just before induction of anaesthesia. The size of each device was selected in accordance with the manufacturer’s guidelines (size 1 for children less than 5 kg in weight and size 1.5 for those weighing between 5 and 10 kg). When inserting the LMA Classic, the cuff was partially inflated in order to reduce insertion time and improve success rate [1, 2, 9]. All devices were inserted by anaesthetists with paediatric experience who had inserted each device on at least 100 occasions. Both devices were inserted according to the manufacturers’ instructions and successful insertion was defined as the observation of symmetrical chest wall movement and a square-wave capnograph trace. Following two failed insertion attempts, the anaesthetist controlled the airway according to his/her own
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Anaesthesia 2014, 69, 362–367
preference and the patient was withdrawn from the study. Insertion time was defined as the time from when the device was picked up until appearance of the first wave on the capnograph trace. Ease of insertion was evaluated using a subjective grading score between 1 and 4 (1, no resistance; 2, mild resistance; 3, moderate resistance; 4, inability to insert the device) [6]. Manipulations required to improve the position of the device, such as changing insertion depth, performing a jaw thrust manoeuvre or extension/flexion of the head were recorded. After insertion of the device, mechanical ventilation of the lungs was commenced and the intracuff pressure of the LMA Classic was set at 40 cmH2O and monitored using a cuff pressure manometer (Mallinckrodt Medical, Athlone, Ireland) [10]. Airway leak pressure was determined by setting the adjustable pressure-limiting (APL) valve to 30 cmH2O and the fresh gas flow rate to 3 l.min 1. Oropharyngeal leak pressure was defined as the point at which equilibrium was attained [6, 9]. When measuring oropharyngeal leak pressure, auscultation over the epigastrium was performed to detect the presence or absence of gastric insufflation. Leak volume was defined as the difference between the inspiratory and expiratory tidal volume and obtained from spirometry on a PrimusTM anaesthetic workstation (Dr€ager, L€ ubeck, Germany). Leakage fraction was the leak volume divided by the inspiratory tidal volume. Five measurements were performed and the average was recorded. Peak inspiratory pressures were also noted. The anatomical position of the device in relation to the glottis was assessed by inserting a fibreoptic bronchoscope (Olympus Optical Co., Tokyo, Japan) through the device. The image was graded using a scale between 1 and 4 (1, vocal cords not visible; 2, vocal cords and anterior epiglottis visible; 3, vocal cords and posterior epiglottis visible; 4, vocal cords visible) [6]. After completion of surgery the patient was transferred to the recovery area and the supraglottic airway device was removed when the patient regained consciousness. Sample size calculation was based on oropharyngeal leak pressure as the primary outcome. Previous studies have demonstrated that the standard deviation of
363
Anaesthesia 2014, 69, 362–367
airway leak pressure of the i-gel and the LMA Classic in children is approximately 6 cmH2O [11, 12]. Assuming a 5% two-tailed significance level (a = 0.05) and power of 80% (b = 0.20), a sample size of 23 patients in each group would be required to detect a difference of 5 cmH2O between the i-gel group and the LMA Classic group.[12] Twenty-seven children in each group were included to allow for a 10% dropout rate. The Kolmogorov–Smirnov test was used to determine the distribution of all continuous variables. Student’s t-test was used for normally distributed data and Mann– Whitney U-test for continuous variables not normally distributed. Chi-squared test or Fisher’s exact test was used to analyse frequency variables and ordinal variables were analysed using the Mann–Whitney U-test. Data were analysed using SPSS version 18 software (SPSS Inc., Chicago, IL, USA) and a p value of < 0.05 was considered statistically significant.
Results Out of the 55 patients eligible for inclusion in the study, 54 patients were enrolled and one was not studied due to refusal of informed consent. One of the patients who was initially included in the study was withdrawn from the LMA Classic group due to the
Kim et al. | i-gel vs LMA Classic in infants
presence of excessive secretions at induction of anaesthesia and 53 patients completed the study (Fig. 1). The baseline characteristics of patients included in the study are shown in Table 1. Device insertion characteristics are shown in Table 2. Both devices were placed successfully in all patients, although it took two attempts to place the LMA Classic in three patients. In one patient, weighing 5.7 kg, the first attempt with a size-1.5 LMA Classic failed and the second attempt using a size-1 LMA Classic succeeded. Median insertion time for the i-gel group was the same as for the LMA Classic group, but insertion of the i-gel was considered significantly easier compared with the LMA Classic (p = 0.009). Manipulation of the device was required less often in the i-gel group compared with the LMA Classic group but this did not reach statistical significance; most manipulations consisted of slight withdrawal of the device following insertion. Good fibreoptic views were obtained through the i-gel in 63% of patients compared with 42% of patients in the LMA Classic group. There was no significant difference in airway leak pressures between the groups and gastric insufflation was similar with both devices. There were no statistically significant differences in ventilation parameters (Table 3).
Figure 1 CONSORT flow diagram to illustrate the study design. 364
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Kim et al. | i-gel vs LMA Classic in infants
Anaesthesia 2014, 69, 362–367
Table 1 Baseline characterisitics of the patients undergoing anaesthesia with the i-gel or LMA Classic. Values are median (IQR [range]), number (proportion) or mean (SD).
Age; months Male:female Weight; kg Height; cm
Device size 1 1.5 Operation time; min Anaesthesia time; min
Table 3 Device performance and ventilatory parameters in patients undergoing anaesthesia with the i-gel or LMA Classic. Values are median (IQR [range]) or number (proportion).
i-gel (n = 27)
LMA Classic (n = 26)
3.0 (1.6–8.0 [1.2–11.0]) 20:7 5.7 (4.5–8.7 [3.4–9.9]) 58.0 (53.4–71.5 [48.6–74.9])
2.9 (2.0–7.3 [1.0–11]) 22:4 5.7 (4.9–7.5 [3.7–9.5]) 59.7 (55.0–62.6 [50.5–77.3])
Airway leak pressure; cmH2O Number of gastric insufflations Peak inspiratory pressure; cmH2O Leak volume; ml
13 (48%) 14 (52%) 43.8 (22.6) 72.7 (22.4)
9 (35%) 17 (65%) 41.6 (17.6) 73.8 (19.1)
Leak fraction; %
Table 2 Insertion characteristics in patients undergoing anaesthesia with the i-gel or LMA Classic. Values are number (proportion) or median (IQR [range]). i-gel group (n = 27) Successful 27 (100%) insertion of device at first attempt Ease of device insertion* 1 26 (96%) 2 1 (4%) 3 0 4 0 Insertion 15 (13–16 time; s [9–22]) Number of 0 manipulations required Fibreoptic view through device† 1 2 (7%) 2 8 (30%) 3 12 (44%) 4 5 (19%)
LMA Classic group (n = 26)
p value
23 (88%)
NS
i-gel (n = 27)
LMA Classic (n = 26)
25 (21–28 [17–30]) 8 (30%)
26 (22–30 [18–30]) 7 (27%)
15 (13–17 [8–25]) 2.1 (0.3–4.0 [0.0–7.6]) 4.0 (0.3–6.4 [0.0–13.7])
15 (13–17 [7–30]) 0.6 (0.0–2.4 [0.0–7.8]) 1.2 (0.0–4.2 [0.0–11.0])
p value NS NS NS NS
NS
(two in the i-gel group and one in the LMA Classic group) during emergence from anaesthesia. No airway obstruction episodes resulted in hypoxia and they were all resolved by the anaesthetist without requiring invasive airway management. There were no devices with blood staining or obvious trauma to the upper airway following removal of the device.
Discussion 18 (69%) 5 (19%) 3 (12%) 0 17 (12–18 [9–69]) 4 (15%)
2 13 3 8
(8%) (50%) (12%) (30%)
0.009
NS NS
NS
*Ease of insertion was graded as 1: no resistance, 2: mild resistance, 3: moderate resistance, 4: inability to place the device. †Fibreoptic view was graded as 1: vocal cords not visible; 2: vocal cords with anterior epiglottis visible; 3: vocal cords with posterior epiglottis visible; 4: vocal cords visible.
Airway obstruction occurred in two patients (one in the i-gel group and one in the LMA Classic group) during the intra-operative period and in three patients © 2014 The Association of Anaesthetists of Great Britain and Ireland
Although the i-gel has been extensively studied in older children and adults and is generally regarded as a viable alternative to the LMA Classic, the devices have not been previously compared in children less than one year old. In very young children, the risk of adverse respiratory events is higher during general anaesthesia because the physiology of infants differs significantly from that of adults [13]. In addition, anatomical differences compared with adults may lead to difficulties with device insertion in this young age group. In this study, which only included children less than a year old, there was a higher first attempt insertion success rate with the i-gel than the LMA Classic. Although this did not reach statistical significance, the operators found that that the i-gel could be inserted more easily, and required less subsequent manipulation, compared with the LMA Classic. The first observational study of the paediatric i-gel by Beylacq et al. [11] demonstrated that the i-gel could be inserted very easily in most cases (90%) and no experience was required to obtain a high first attempt 365
Anaesthesia 2014, 69, 362–367
success rate. Recent paediatric resuscitation simulation scenarios revealed that all participants, whatever their level of experience with paediatric airway care, could place the i-gel successfully at first attempt [14]. In a previous study comparing the i-gel with the LMA Classic in children, the i-gel was inserted more quickly than the LMA Classic, which was inserted using Brain’s technique and a fully deflated cuff [6]. In our study, the LMA Classic was inserted with a partially inflated cuff which we anticipated would result in easier insertion and reduced cuff inflation times after insertion. In addition, experienced anaesthetists, rather than novices, participated in our study. As a result, median insertion times for the two devices were similar, at approximately 16 s. Schunk et al. [14] found that insertion time for the i-gel was significantly shorter than for the LMA Unique (even with a partially inflated cuff) in all professional groups, including inexperienced physicians and paramedics. Based on these results, it is reasonable to assume that the i-gel can be inserted more easily and quickly, with higher success rates at first insertion attempt, regardless of experience. Given these features, the i-gel could be a valuable tool for airway management in infants, who have limited oxygen reserves during periods of apnoea [13]. Oropharyngeal leak pressure is defined as the airway pressure at which air leaks into the mouth or enters the stomach [15]. This feature is the most common primary outcome used to evaluate the safety and efficacy of supraglottic airway devices because high pressures generally indicate that adequate ventilation can be achieved without air leakage during positive pressure ventilation at high inspiratory pressures [16]. In infants, the use of a supraglottic airway device with a high oropharyngeal leak pressure is beneficial because high inspiratory pressure is required during positive pressure ventilation due to reduced lung compliance and increased airway resistance [5, 13]. In our study, oropharyngeal leak pressures were similar in both the i-gel group and the LMA Classic group and agreed with those reported in previous studies [6, 15]. The LMA Classic necessitates the use of a cuff pressure manometer in order to maintain appropriate intracuff pressure for optimum airway sealing, whereas the i-gel does not require cuff inflation or cuff pressure adjustments [9, 17]. This suggests that the i-gel 366
Kim et al. | i-gel vs LMA Classic in infants
may be more useful in clinical situations when cuff pressure manometers are not available. Fibreoptic views are frequently used to assess the anatomical position of supraglottic airway devices following insertion and to make comparisons between devices [5, 6]. In the present study, the i-gel resulted in improved views of the vocal cords (a score of 3 or 4) compared with the LMA Classic, although the differences did not reach statistical significance. Lee et al. found that the i-gel resulted in a significantly better fibreoptic view compared with the LMA Classic [6]. However, a poor view of the glottis does not necessarily mean that the airway is obstructed or that there is a lower oropharyngeal leak pressure [15, 18]. Nevertheless, airway obstruction due to a down-folded epiglottis may result in an increase in inspiratory pressure during positive pressure ventilation when small supraglottic airway devices are in situ [5], and an improved view such as that obtained with the i-gel ensures airway patency with adequate ventilation and indicates that there is an unobstructed conduit for tracheal tube insertion through the device, if required [6, 15]. Another issue related to supraglottic airway devices in infants is delayed airway obstruction. Previous studies demonstrated that this occurred more frequently in infants and was related to movement of the device intra-operatively [4]. In our study, anaesthesia was maintained at a deep level in order to avoid unnecessary movement of the patient, and thus delayed airway obstruction was infrequent. In clinical situations, where the patient is more likely to move, the i-gel may prove a better choice than the LMA Classic due to its buccal cavity stabiliser which has been designed to reduce device movement [15]. Our study has several limitations. First, the number of patients, particularly those receiving the size-1 LMA Classic, was relatively small. Tracheal intubation is usually preferred in small babies due to the potential for complications associated with supraglottic airway devices [15] and so recruiting large numbers of patients for our study was not possible. Second, we could not assess postoperative complications such as sore throat or dysphagia because infants are unable to report complications. However, complications have been shown to be relatively uncommon in previous studies in older children and were not likely to be an © 2014 The Association of Anaesthetists of Great Britain and Ireland
Kim et al. | i-gel vs LMA Classic in infants
issue in our study [6]. Third, all the anaesthetists were experienced in insertion of both devices and it was not feasible to include novice participants. In conclusion, the i-gel was easier to insert than the LMA Classic in infants requiring general anaesthesia and it may be the supraglottic airway device of choice for this group of patients. Further studies comparing the i-gel with other supraglottic devices should be performed in order to determine the best supraglottic airway device for children less than a year old.
Competing interests No external funding and no competing interests declared.
References 1. O’Neill B, Templeton JJ, Caramico L, Schreiner MS. The laryngeal mask airway in pediatric patients: factors affecting ease of use during insertion and emergence. Anesthesia and Analgesia 1994; 78: 659–62. 2. Ghai B, Wig J. Comparison of different techniques of laryngeal mask placement in children. Current Opinion in Anesthesiology 2009; 22: 400–4. 3. Chen L, Hsiao AL. Randomized trial of endotracheal tube versus laryngeal mask airway in simulated prehospital pediatric arrest. Pediatrics 2008; 122: e294–7. 4. Mizushima A, Wardall GJ, Simpson DL. The laryngeal mask airway in infants. Anaesthesia 1992; 47: 849–51. 5. Park C, Bahk JH, Ahn WS, Do SH, Lee KH. The laryngeal mask airway in infants and children. Canadian Journal of Anesthesia 2001; 48: 413–7. 6. Lee JR, Kim MS, Kim JT, et al. A randomised trial comparing the i-gel(TM) with the LMA Classic (TM) in children. Anaesthesia 2012; 67: 606–11. 7. Beringer RM, Kelly F, Cook TM, et al. A cohort evaluation of the paediatric i-gel(TM) airway during anaesthesia in 120 children. Anaesthesia 2011; 66: 1121–6.
© 2014 The Association of Anaesthetists of Great Britain and Ireland
Anaesthesia 2014, 69, 362–367 8. Drage MP, Nunez J, Vaughan RS, Asai T. Jaw thrusting as a clinical test to assess the adequate depth of anaesthesia for insertion of the laryngeal mask. Anaesthesia 1996; 51: 1167– 70. 9. Kim MS, Bai SJ, Oh JT, Youm SM, Lee JR. Comparison of 2 cuff inflation methods before insertion of laryngeal mask airway for safe use without cuff manometer in children. American Journal of Emergency Medicine 2013; 31: 346–52. 10. Hockings L, Heaney M, Chambers NA, Erb TO, von UngernSternberg BS. Reduced air leakage by adjusting the cuff pressure in pediatric laryngeal mask airways during spontaneous ventilation. Pediatric Anesthesia 2010; 20: 313–7. 11. Beylacq L, Bordes M, Semjen F, Cros AM. The i-gel, a singleuse supraglottic airway device with a non-inflatable cuff and an esophageal vent: an observational study in children. Acta Anaesthesiologica Scandinavica 2009; 53: 376–9. 12. Micaglio M, Bonato R, De Nardin M, et al. Prospective, randomized comparison of ProSeal and Classic laryngeal mask airways in anaesthetized neonates and infants. British Journal of Anaesthesia 2009; 103: 263–7. 13. McNiece WL, Dierdorf SF. The pediatric airway. Seminars in Pediatric Surgery 2004; 13: 152–65. 14. Schunk D, Ritzka M, Graf B, Trabold B. A comparison of three supraglottic airway devices used by healthcare professionals during paediatric resuscitation simulation. Emergency Medicine Journal 2013; 30: 754–7. 15. Hughes C, Place K, Berg S, Mason D. A clinical evaluation of the i-gel supraglottic airway device in children. Pediatric Anesthesia 2012; 22: 765–71. 16. Teoh WH, Lee KM, Suhitharan T, Yahaya Z, Teo MM, Sia AT. Comparison of the LMA Supreme vs the i-gel in paralysed patients undergoing gynaecological laparoscopic surgery with controlled ventilation. Anaesthesia 2010; 65: 1173–9. 17. Licina A, Chambers NA, Hullett B, Erb TO, von Ungern-Sternberg BS. Lower cuff pressures improve the seal of pediatric laryngeal mask airways. Pediatric Anesthesia 2008; 18: 952– 6. 18. Inagawa G, Okuda K, Miwa T, Hiroki K. Higher airway seal does not imply adequate positioning of laryngeal mask airways in paediatric patients. Pediatric Anesthesia 2002; 12: 322–6.
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