Anaesthesia 2015, 70, 613–622
doi:10.1111/anae.13035
Review Article Comparison of streamlined liner of the pharynx airway (SLIPATM) and laryngeal mask airway: a systematic review and meta-analysis G. J. Choi,1 H. Kang,2 C. W. Baek,3 Y. H. Jung,3 Y. C. Woo,3 S. H. Kim4 and J. G. Kim5 1 Clinical Assistant Professor, 2 Associate Professor, 3 Professor, Department of Anaesthesiology and Pain Medicine, 4 Assistant Professor, 5 Professor, Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea
Summary We performed a systematic review to compare the efficacy and safety of the streamlined liner of the pharynx airway and laryngeal mask airway used in adults during general anaesthesia. We included 14 studies with studies with 1273 patients in total. There was no evidence of a difference between the two devices in insertion success rate on the first attempt (13 studies, 1143 patients), insertion time (seven studies, 576 patients), ease of insertion (five studies, 466 patients), oropharyngeal leak pressure (eight studies, 771 patients) and the quality of the fibreoptic view of the larynx through the device (three studies, 281 patients). The relative risk (95% CI) of bloodstaining of the device (nine studies, 859 patients) was 2.09 (1.46–3.00) for the streamlined liner of the pharynx airway compared with the laryngeal mask airway. Other adverse events were comparable. Subgroup analysis suggested that the insertion by novice users might be faster and more successful with the streamlined liner of the pharynx airway than the laryngeal mask airway; however, this was from only two studies and 186 patients. The method of size selection of the streamlined liner of the pharynx airway device might also affect the speed of insertion: choosing according to the width of the patient’s thyroid cartilage, rather than height, may produce better results. .................................................................................................................................................................
Correspondence to: H. Kang Email: [email protected] Accepted: 13 January 2015
Introduction Supraglottic airway devices have been widely used as alternatives to tracheal intubation during general anaesthesia because of the convenience of insertion and the feasibility of effective positive pressure ventilation [1]. Since the introduction of the classic laryngeal mask airway (LMA) in the late 1980s, various types of LMA have been developed for clinical use with successful results in terms of efficacy and safety [1, 2]. The streamlined liner of the pharynx airway (SLIPATM) is a relatively new, non-cuffed, pharynxshaped disposable supraglottic airway device made of © 2015 The Association of Anaesthetists of Great Britain and Ireland
soft plastic [3]. Several studies have compared the SLIPA with various types of LMA with regard to clinical performance, but the results have been inconsistent. The purpose of this systematic review was to compare the effectiveness and safety of the SLIPA with various types of LMA when used in adults under general anaesthesia.
Methods We developed the protocol for this review and registered with PROSPERO (registration number: CRD42014007139; www.crd.york.ac.uk/PROSPERO), 613
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although we had already commenced data extraction at the time of registration. A systematic review of the literature for studies comparing SLIPA to LMAs in adults undergoing general anaesthesia was conducted according to the protocol recommended by the Cochrane Collaboration [4]. Two authors (SHK and JGK) independently conducted database searches using Embase, MEDLINE, the Cochrane Central Register of Controlled Trials (CENTRAL) and Google Scholar in November 2013; this was updated in October 2014. We also searched for registered trials in the clinical trial registries listed in the Appendix. The search terms included ‘laryngeal mask’, ‘laryngeal mask airway’, ‘LMA’, ‘streamlined liner of the pharynx airway’ and ‘SLIPA’. The reference lists of all identified reports were also searched manually. Randomised controlled trials (including studies with a crossover design) comparing the SLIPA to LMAs in adult patients undergoing general anaesthesia were included. Only peer-reviewed studies were included. There was no limit with respect to the language in which the article was written or the type of LMA used. Two authors (GJC and HK) independently selected eligible studies, and they discussed any differences in opinion to arrive at a consensus as to whether a study should be included or excluded. Disagreement over inclusion or exclusion was settled by discussion with two senior authors (CWB and YHJ). We treated all LMAs, including the classic LMA, ProSealâ LMA, and SoftSealâ LMA, as a single group (LMA group). If the type of LMA was not specified, we assumed that a classic LMA had been used. If studies compared the SLIPA with more than two airway devices including the LMA, only data for the SLIPA and LMA were extracted for analysis. For crossover studies, we included only data for the first period to avoid the possibility of carry-over bias [4]. To deal with missing data, we included dropouts in this analysis on an intention-to-treat basis for dichotomous data [4]. Where participants had been excluded from the trial before the study endpoint, we assumed that they experienced a negative outcome by the end of the trial. We examined the validity of this decision in the sensitivity analyses by applying worst- or best-case scenarios. For continuous data, we extracted data as reported by the authors [4]. We considered device users as 614
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‘novice’ when they had used each type of SLIPA and LMA fewer than five times; otherwise, users were regarded as ‘experienced’. When studies reported outcomes at various time points after anaesthesia, we extracted the data collected in the post-anaesthesia care unit. If the mean and standard deviation were not reported, we attempted to contact the corresponding author to obtain the data, or calculated them based on the methods described in the Cochrane Handbook [4]. Two authors (GJC and YCW) independently extracted the following data: name of the first author; year of publication; whether the trial was registered; type of LMA; number of participants; baseline data (age, weight, and height); methods of selecting the size of device; expertise of device user; type of surgery; use of a neuromuscular blocking drug; rate of insertion success on the first attempt; insertion time; ease of insertion; oropharyngeal leak pressure; fibreoptic view; and complications, assessed both during and after anaesthesia. We also recorded information about study sponsorship or competing interests. The quality of eligible studies was assessed independently by two authors (HK and YCW) using the ‘risk of bias’ tool provided with Review Manager software (version 5.3, The Cochrane Collaboration, Oxford, UK). Quality was evaluated based on the following eight potential sources of bias: random sequence generation; allocation concealment; blinding of the participants; blinding of the outcome assessors during anaesthesia; blinding of the outcome assessors after anaesthesia; incomplete outcome data; selective reporting; and other bias. Each of these domains was graded as ‘high’, ‘low’ or ‘unclear’, to reflect a high risk of bias, low risk of bias and uncertainty of bias, respectively. We computed the pooled relative risk (RR) with corresponding 95% CI for dichotomous data, and weighted mean difference (WMD) or standardised mean difference (SMD) with 95% CI for continuous data. We used the chi-squared test for homogeneity and the I2 test for heterogeneity. We regarded a level of 10% significance (p < 0.10) in the chi-squared statistic or an I2 greater than 50% as considerable heterogeneity, and we then used the Mantel-Haenszel random-effects model. Otherwise, we applied the Mantel–Haenszel fixed-effects model [4, 5]. We carried out subgroup analyses based on: the expertise of the device © 2015 The Association of Anaesthetists of Great Britain and Ireland
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user; the method of SLIPA size selection; the type of LMA; the type of surgery; and the use of neuromuscular blocking drugs. We also conducted sensitivity analyses to evaluate the influence of individual studies from analyses with a heterogeneity of I2 greater than 50% on the overall effect estimate, by excluding one such study at a time from the analysis. We also performed sensitivity analyses based on sponsorship or declared conflicts of interest. Funnel plots were drawn as a measure of publication bias across studies and were assessed visually for symmetry. We also estimated publication bias using Egger’s linear regression test [4]. If the funnel plot was asymmetrical or the p value was < 0.10 on Egger’s test, the presence of a publication bias was considered, and ‘trim and fill’ analysis was performed. We performed all analyses using Review Manager and Comprehensive meta-analysis software (version 2.0, Biostat, Englewood, NJ, USA).
Results The review is reported according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement [6]. The study flow diagram is shown in Fig. 1. One record was excluded as it was a
Records identified through database searching (n– = 290)
conference abstract reporting the same trial as another, full, publication. One study was a thesis identified through hand searching [7], included after discussion with the senior authors (CWB and YHJ), as, although not published, it was a peer-reviewed study. Of the fourteen included randomised controlled trials [3, 7–19], one study was a randomised crossover study [11]. Two studies had been prospectively registered [8, 19]. The SLIPA was compared with the classic LMA in seven studies [7, 12–14, 16–18], with the ProSeal LMA in six [3, 8–10, 15, 19], and with the SoftSeal LMA in one [11]. Three studies compared the SLIPA with two other types of airway device [13, 15, 18], namely: with the classic LMA and the i-gelTM [13]; with the classic LMA and a tracheal tube [18]; and with the ProSeal LMA and a tracheal tube [15]. Selection of the size of SLIPA was based on patients’ height in four studies [9–12] and thyroid cartilage width in eight [3, 7, 8, 15–19]. In two studies [11, 16], novice users inserted the devices: these were either medical students [11] or residents in the department of anaesthesiology [16]. Experienced anaesthesiologists inserted the device in ten studies [7–10, 12–15, 17, 19], one of which presented the detail of experience in response to a later letter to the editor of the journal [20]. Two studies did not
Records identified in clinical trial registries (n = 7)
Records identified through hand searching (n = 2)
174 records after removal of duplicates (n = 125)
Records excluded (n = 157)
Excluded (n = 3) Full-text articles assessed for eligibility (n = 17)
Studies included in meta-analysis (n = 14)
Irrelevant outcome (n = 1) Correspondence (n = 1) Duplicate (conference proceeding) (n = 1)
Figure 1 Flow diagram showing the number of abstracts and articles identified and evaluated during the review process. © 2015 The Association of Anaesthetists of Great Britain and Ireland
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mention operator experience [3, 18]. Twelve reports were written in English [3, 8–17, 19], one was in Korean [7] and one was in Chinese [18]. Devices were provided free of charge in five studies [3, 11, 13, 15, 17]. The author of two of these studies was the inventor of the SLIPA [3, 15]; the other studies reported that there was no competing interest [11, 13, 17]. The study characteristics are summarised in Table 1. All studies mentioned randomisation [3, 7–19], but only ten studies described the method used for sequence generation [3, 8, 10–13, 15–17, 19]. Eight studies reported allocation concealment [8, 10, 11, 13, 15–17, 19]. Blinding of outcome assessment was reported in one study during anaesthesia [19] and seven studies after anaesthesia [3, 8, 10, 11, 14, 17, 19]. Eight studies reported incomplete outcome data [3, 8– 11, 16, 17, 19]. Table 2 summarises the risks of bias for each domain. Sensitivity analyses for heterogeneous outcomes did not show any change in significance of results. We also conducted sensitivity analyses to evaluate the influence of conflict of interest or sponsorship on all outcomes: firstly by excluding the two studies reported by the inventor of the SLIPA [3, 15]; and secondly by excluding the five studies in which airway devices had been provided free of charge [3, 11, 13, 15, 17]. These exclusions did not affect the overall results. A funnel plot was applied for every comparison; all displayed a symmetrical appearance. The results of Egger’s test indicated that publication bias was unlikely for the primary outcomes: rate of insertion success on the first attempt (p = 0.21); insertion time (p = 0.19); ease of insertion (p = 0.08); oropharyngeal leak pressure (p = 0.25); fibreoptic view of the larynx (p = 0.34). On the assumption that ease of insertion showed publication bias, we performed trim and fill analysis to evaluate the influence of publication bias. However, the results from these tests suggested that publication bias was unlikely. All studies (1143 patients) investigated the insertion success rate on the first attempt [3, 7–18]; none reported a significant difference between the groups (RR 1.01, 95% CI 0.97–1.05, p = 0.26, I2 = 19%). We performed a subgroup analysis for expertise of device users. The RR (95% CI) of insertion success on the first attempt was significantly higher in the SLIPA 616
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group when novice users (two studies, 186 patients) inserted the devices, at 1.18 (1.02–1.36), p = 0.56, while it was similar when experienced users (nine studies, 777 patients) inserted the devices, at 0.98 (0.94– 1.02) (Fig. 2). We also conducted subgroup analyses for the method of SLIPA size selection, type of LMA, and use of neuromuscular blocking drugs, all of which showed no evidence of a difference. Insertion time was measured in seven studies (576 patients) [7, 9–11, 13, 16, 17]. There was substantial heterogeneity between studies (I2 = 92%) but no difference in insertion times overall, the WMD (95% CI) being 0.81 ( 2.96 to 1.33) s. For novice users (two studies, 186 patients), the mean (95% CI) insertion time of the SLIPA was 5.5 (10.6–0.3) s shorter compared with LMA insertion (p = 0.63), and I2 dropped to 0%. Insertion times for the two devices was similar when performed by experienced users (five studies, 390 patients), with a WMD (95% CI) of 0.3 ( 2.6 to 2.0) s; I2 was not decreased. On subgroup analysis for SLIPA size selection method (six studies, 526 patients), insertion time was significantly shorter for the LMA than for the SLIPA when selected based on patient height (three studies, 252 patients): WMD (95% CI) 2.0 (0.2–3.9) s, p = 0.12, whereas it was similar between two groups when selecting based on thyroid cartilage width (three studies, 274 patients): WMD (95% CI) 2.5 ( 5.5 to 0.6) s. Insertion time was significantly shorter for the SLIPA compared with the classic LMA (four studies, 324 patients): WMD (95% CI) 2.2 ( 3.8 to 0.6) s (p = 0.01), but significantly longer for the SLIPA compared with the ProSeal LMA (two studies, 180 patients): WMD (95% CI) 2.06 (0–4.1) s (p = 0.05). There was also no evidence of a difference in insertion time whether neuromuscular blockade was used or not (seven studies, 576 patients), with WMD (95% CI) of 0.5 ( 3.7 to 2.7) s with (five studies, 416 patients) and 1.6 ( 4.5 to 1.3) s without (two studies, 160 patients). Five studies (466 patients) evaluated the ease of insertion using different scales [7, 9, 10, 14, 17]. When the best scale in each study was used for analysis, there was no evidence of a difference between the two devices: the RR (95% CI) was 0.88 (0.76–1.02). Eight studies (771 patients) measured oropharyngeal leak pressure, all using the manometric stability technique [3, 7–10, 14, 15, 17]. Overall, oropharyngeal © 2015 The Association of Anaesthetists of Great Britain and Ireland
© 2015 The Association of Anaesthetists of Great Britain and Ireland
51 30 30 30 30 30 30 30 30 50 50 59 65 36 36 50 50 60 60
PLMA SLIPA PLMA SLIPA cLMA SLIPA cLMA SLIPA cLMA SLIPA cLMA SLIPA cLMA SLIPA SSLMA SLIPA PLMA SLIPA PLMA
(33.0–51.8) (34.0–54.8) (14.0) (14.0) (15.9) (15.5) (16.3) (15.8) (17.0)
49.0 43.0 35.2 33.0 36.9 39.9
38.0 38.2 52.8 54.6 46.6 47.7 NR [20–77] [19–81] (8.3) (7.0) (9.8) (11.1)
(8.7) (9.8) (9.4) (8.4) (9.3) (8.8)
43.1 (19.3) 42.0 (19.3) 46.3 (17.8) NR
41.0 45.5 41.8 38.1 46.0 43.8 41.2 37.5 46.6
Age; years (10.3) (13.9) (9.5) (12.0) (5.6) (5.5) (13.8) (15.1) (7.9)
56.8 54.8 53.2 50.6 70.0 75.0 77.0 73.0 66.0 66.0 64.6 64.9
NR (7.8) (6.3) (10) (11.3) (15.0) (12.0) [53–112] [45–100] (10.0) (11.0) (11.1) (9.2)
59.7 (8.3) 64.7 (11.2) 66.5 (15.1) NR
64.4 61.2 61.6 57.2 60.1 58.2 69.9 72.1 60.6
Weight; kg (7.1) (9.9) (6.8) (8.3) (3.9) (4.5) (12.2) (16.3) (5.5)
NR
164.5 163.3 160.2 158.7 170.0 170.0 169.0 170.0 NR
NR (5.5) (7.4) (5.9) (4.9) (11.0) (10.0) [152–183] [150–170]
161.0 (7.4) 168.8 (8.3) 163.2 (15.0) NR
162.9 160.4 162.8 160.5 158.2 157.1 169.1 165.5 159.5
Height; cm
H W T W T W
T S T W NR
W H W T W NR
T W T W H W H W T
NR
> 150 times > 200 times > 10 times Experienced No experience Experienced > 10 times > 3 years Practice with manikin > 100 times
> 1 year > 4 years < 5 times < 5 times > 10 times > 5 years > 100 times > 100 times > 20 times (manikin), > 30 times > 6 years > 20 times > 2 years NR
Expertise of device user
Minor gynaecological procedure
Laparoscopic gynaecological procedure
NR
Minor radiotherapy, gynaecological and general surgery Ophthalmic surgery
Chemoport insertion
Elective surgery
Laparoscopic gynaecological surgery
Elective surgery
Laparoscopic gynaecological surgery
Lower abdominal laparoscopic surgery
Minor surgery
Elective surgery
Laparoscopic cholecystectomy
Type of surgery
No
No
Yes
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Use of NBD
NBD, neuromuscular blocking drug; T, thyroid cartilage width; PLMA, ProSeal LMA; W, patient weight; cLMA, classic LMA; H, patient height; NR, not reported; S, patient sex; SSLMA, SoftSeal LMA.
Miller & Light [3]
Miller & Camporota [15]
Hein et al. [11]
Lange et al. [14]
Puri et al. [17]
Kim [7]
Jindal et al. 2009 [13]
Xu & Zhong [18]
Choi et al. [10]
Woo et al. [8]
Abdellatif & Ali [9]
Abd Rahman et al. [12]
Oh et al. [16]
60 60 57 57 31 31 60 60 50
SLIPA PLMA SLIPA cLMA SLIPA cLMA SLIPA PLMA SLIPA
Cha et al. [19]
n
Group
Study
Device selection method
Table 1 Characteristics of included studies comparing the streamlined liner of the pharynx airway (SLIPA) with the laryngeal mask airway (LMA). Values are number, mean (SD), median (IQR), or median [range].
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617
618
risk risk risk risk risk risk risk risk risk risk risk risk risk risk Low Low Low Low Low Low Low Low Low Low Low Low Low Low Low risk Unclear Unclear Unclear Low risk Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Low risk Low risk Unclear Low risk Low risk Low risk Unclear Unclear Unclear Low risk Unclear Low risk Unclear Low risk Low risk Unclear Low risk Unclear Low risk Low risk Low risk Low risk Unclear Unclear Unclear Unclear Unclear Low risk Low risk Unclear Unclear Unclear High risk Unclear Unclear Unclear Unclear Unclear Unclear High risk Unclear Unclear Unclear Unclear Unclear Unclear Low risk Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Low risk Low risk Low risk Unclear Low risk Low risk Unclear Low risk Unclear Low risk Unclear Low risk Low risk Low risk
Study
Cha et al. [19] Oh et al. [16] Abd Rahman et al. [12] Abdellatif & Ali [9] Woo et al. [8] Choi et al. [10] Xu & Zhong [18] Jindal et al. [13] Kim [7] Puri et al. [17] Lange et al. [14] Hein et al. [11] Miller & Camporota [15] Miller and Light [3]
Low risk Low risk Unclear Unclear Low risk Low risk Unclear Low risk Unclear Low risk Unclear Low risk Low risk Unclear
Blinding of outcome assessment during anaesthesia Blinding of participants Allocation concealment Random sequence generation
Table 2 Assessments of the risk of bias based on Cochrane risk of bias tool.
Blinding of outcome assessment after anaesthesia
Incomplete outcome data
Selective reporting
Other bias
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leak pressure was similar between groups: WMD (95% CI) 0.2 ( 1.1 to 0.8) cmH2O. Excluding one study at a time from the analysis did not affect the overall effect. We conducted subgroup analyses for method of SLIPA size selection, type of LMA, type of surgery and use of neuromuscular blocking drug. Oropharyngeal leak pressure showed marginal significance when selecting based on patient height (two studies, 180 patients): WMD (95% CI) 1.1 ( 2.3 to 0) cmH2O, whereas it was similar when selecting based on thyroid cartilage width (five studies, 467 patients): WMD (95% CI) 0.4 ( 1.2 to 1.9) cmH2O (Fig. 3). There were no significant differences within the subgroup comparisons for type of LMA, laparaoscopic vs other surgery, or use of neuromuscular blockade. Four studies (341 patients) evaluated the fibreoptic view of the larynx through the device using different scales [8–10, 18]; three (281 patients) of these studies mentioned related details [8–10]. We adjusted for the differences before combining data; there was no evidence of a difference; the RR (95% CI) of a good quality fibreoptic view of the larynx was 1.04 (0.84–1.27). Two studies (161 patients) compared perilaryngeal leakage with a change in head position between the SLIPA and the PLMA [8, 10]. One study reported an increased incidence of leakage with the PLMA vs the SLIPA [8], while the other study found similar rates for both devices [10]. Bloodstaining of the supraglottic device was recorded in nine studies (859 patients) [3, 7–10, 12, 14, 17, 19]; the RR (95% CI) was greater with the SLIPA at 2.01 (1.44–2.80) compared with the LMA devices (p = 0.36) (Fig. 4). Gastric insufflation was examined with a stethoscope in four studies (405 patients) [8–10, 14]; the RR (95% CI) of gastric insufflation was greater with the SLIPA at 2.15 (0.28–16.69), but this difference was not significant. Eight studies set out to record regurgitation [8–11, 14, 16–18]; only one instance of regurgitation, associated with use of the SLIPA, was reported in a single study [11]. One study reported one episode of transient bronchospasm in the LMA group and one episode of partial airway obstruction in the SLIPA group [11]. Three studies documented coughing [11, 17, 18]; this was observed once with the SLIPA in each study [11, 17, 18] and once with the LMA in one study [18]. Nine studies (812 patients) reported the incidence of © 2015 The Association of Anaesthetists of Great Britain and Ireland
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Figure 2 Forest plot showing the rate of insertion success on the first attempt: SLIPA vs LMA. Subgroup analyses according to expertise of device users: novice users vs experienced users. M-H, Mantel-Haenszel.
sore throat [7, 9, 10, 12, 14, 16–19], and four (377 patients) evaluated its severity using an 11-point visual analogue scale [9, 10], an 11-point [8] or a 101-point numerical rating scale [17]. The incidence and severity of sore throat were similar between the two groups, with RR (95% CI) 0.95 (0.75–1.21) for incidence and SMD (95% CI) 0.06 ( 0.24 to 0.35) for severity, respectively. Hoarseness (four studies, 394 patients) [9, 16–18] and dysphagia (three studies, 334 patients) [9, 16, 17] were comparable with the two devices, the RR (95% CI) being 0.44 (0.09–2.14) and 0.93 (0.46–1.85), respectively. Postoperative nausea and vomiting was sought in a single study [10] and was observed four times with the SLIPA and three times with the LMA.
Discussion This systematic review with meta-analysis suggests that the SLIPA and the LMA are similarly efficacious in use, as shown by both the rate of successful insertion on the first attempt, and the time taken to insert the © 2015 The Association of Anaesthetists of Great Britain and Ireland
devices. We also found no evidence of a difference between the two devices in ease of insertion, oropharyngeal leak pressure or quality of fibreoptic view of the larynx through the device. Bloodstaining of the device was more commonly noted after use of the SLIPA. Although only two studies examined how novice users performed on inserting the devices, novices seemed to be more likely to successfully insert the SLIPA than the LMA on the first attempt; SLIPA insertion was also more rapid. The SLIPA might be easier for novice users than the LMA because the device has no cuff to inflate and insertion involves fewer steps [11, 16]. This suggests the potential of the SLIPA as the primary supraglottic airway device for users with little prior experience, especially in an emergency. However, the overall rates of successful insertion by novice users of both devices were high, which might be a result of the apparent easy handling of supraglottic airway devices. Furthermore, although the rate of insertion 619
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Figure 3 Forest plot showing the oropharyngeal leak pressure: SLIPA vs LMA. Subgroup analyses according to the method of SLIPA size selection: patient height vs thyroid cartilage width. IV, inverse variance.
Figure 4 Forest plot showing the incidence of bloodstaining on the devices when the SLIPA is compared with the LMA.
success on the first attempt and insertion time were comparable when experienced users performed insertion, those surveyed had more accumulated experience with the LMA than with the SLIPA. This would suggest that it is easy to gain proficiency with the SLIPA, like other supraglottic airway devices [17]. The SLIPA has a preformed fixed shape, which may result in repeated attempts and inadequate sealing within the airway [8, 21]. Therefore, it is important to choose a SLIPA of appropriate size. The 620
manufacturer recommends that SLIPA size is selected based on the patient’s height. The other known method of size selection is to compare thyroid cartilage width with the widest point of the SLIPA [3, 15]. Our subgroup analysis has illuminated this question: SLIPA insertion took longer than LMA insertion when selection was based on height, but insertion times were similar when selection was based on thyroid cartilage width. This discrepancy between the two selection methods may suggest that SLIPA size selection © 2015 The Association of Anaesthetists of Great Britain and Ireland
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based on patient height is less accurate. Woo et al. mentioned that the manufacturer’s size rule was imprecise owing to size overlap [8]. The study that compared two selection methods reported that the method based on thyroid cartilage width was better in terms of oropharyngeal leak pressure and need for manipulation during SLIPA insertion [22]. Thus, clinical efficacy of the SLIPA may depend crucially on proper size selection. The oropharyngeal leak pressure determines the feasibility of positive pressure ventilation and hence the degree of airway protection provided by supraglottic airway devices [23]. The efficacy of the LMA seal depends on the fit between the oval groove surrounding the glottis and the oval cuff of the LMA [24]. Despite the lack of an inflatable cuff with the SLIPA, we found no evidence of a difference in oropharyngeal leak pressure between the two devices. As the shape of the SLIPA more closely resembles peripharyngeal anatomy [3], it may seal the airway effectively if size selection is suitable. Moreover, Woo et al. demonstrated that perilaryngeal leakage with a change in head position was more common with the PLMA than with the SLIPA, which might be associated with the fact that the shape of the SLIPA device is similar to that of the pharynx [8]. There were no serious complications with either device. No statistically significant difference was found between the two devices in the incidence of complications, except for bloodstaining on the devices. This complication, reflecting direct trauma to the pharyngeal mucosa or other structures, was not thought to be clinically significant. The incidence and severity of sore throat were comparable between the two groups. The SLIPA is constructed of stiffer plastic material than the LMA, which is made of silicone, and might cause more mucosal injury to the deeper pharyngeal structures [8, 10], which in turn may explain the higher incidence of bloodstaining on the SLIPA. Gastric insufflation can result from the inappropriate sealing of a supraglottic airway device. The result that gastric insufflation was comparable between groups may correlate with similar levels of oropharyngeal leak pressure. There was no report of regurgitation except in one case of SLIPA use; this did not lead to aspiration. © 2015 The Association of Anaesthetists of Great Britain and Ireland
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The present review has several limitations. First, only one study reported that assessment of outcomes noted during anaesthesia was blinded [19]. This may be insufflation was because of the challenge posed by clear differences in the appearances of these airway devices. However, outcomes during anaesthesia such as insertion time, oropharyngeal leak pressure, fibreoptic view and gastric insufflation were objective measurements. A successful or failed attempt at insertion was determined based on objective criteria. Second, some outcomes were heterogeneous. Insertion time showed substantial heterogeneity, which was most likely to be due to differences in: the expertise of the device users; the method for device size selection; the type of LMA; the use of neuromuscular blocking drugs; induction or maintenance of anaesthesia; anaesthesia depth; the range of definitions of insertion times; and the permissible number of attempts at successful insertion. In spite of the fact that we tried to conduct subgroup analyses for some of these factors, we could not take all of them into account. Third, experienced users in most studies would be expected to have greater accumulated experience with the LMA compared with the SLIPA, which may have introduced bias. However, the steep learning curve for use of the SLIPA seems to offset any discrepancy with regard to experience. Our study has demonstrated strength, notwithstanding these limitations, by applying rigorous methodology to provide the first systematic review comparing SLIPA and LMA devices used under general anaesthesia. In conclusion, the SLIPA was similar to LMAs with respect to the rate of insertion success on the first attempt, insertion time, ease of insertion, oropharyngeal leak pressure and quality of fibreoptic view of the larynx. The incidence of bloodstaining on the devices was greater in the SLIPA than in the LMA, but the other complications were similar. The selection of SLIPA size may be better based on thyroid cartilage width than patient height.
Acknowledgements This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A1A1 003700). 621
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Competing interests No competing interests declared.
References 1. Cook TM, Howes B. Recent developments in efficacy and safety of supraglottic airway devices. Continuing Education in Anaesthesia Critical Care & Pain 2011; 11: 56–61. 2. Brain AI. The development of the Laryngeal Mask – a brief history of the invention, early clinical studies and experimental work from which the Laryngeal Mask evolved. European Journal of Anaesthesiology 1991; Suppl 4: 5–17. 3. Miller DM, Light D. Laboratory and clinical comparisons of the Streamlined Liner of the Pharynx Airway (SLIPA) with the laryngeal mask airway. Anaesthesia 2003; 58: 136–42. 4. Higgins JP, Green S. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0. Oxford, UK. The Cochrane Collaboration, 2011. 5. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. British Medical Journal 2003; 327: 557–60. 6. Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Medicine 2009; 6: e1000097. 7. Kim JY. The effectiveness of the Streamlined Pharynx Airway Liner (SLIPA) compared with the classic Laryngeal Mask Airway (LMA) in patient undergoing chemoport insertion. Graduate school of Chungnam National University, Master’s Thesis, 2009. 8. Woo YC, Cha SM, Kang H, et al. Less perilaryngeal gas leakage with SLIPATM than with LMA-ProSealTM in paralyzed patients. Canadian Journal of Anesthesia 2011; 58: 48–54. 9. Abdellatif AA, Ali MA. Comparison of streamlined liner of the pharynx airway (SLIPATM) with the laryngeal mask airway ProsealTM for lower abdominal laparoscopic surgeries in paralyzed, anesthetized patients. Saudi Journal of Anaesthesia 2011; 5: 270–6. 10. Choi YM, Cha SM, Kang H, et al. The clinical effectiveness of the streamlined liner of pharyngeal airway (SLIPATM) compared with the laryngeal mask airway ProSealTM during general anesthesia. Korean Journal of Anesthesiology 2010; 58: 450– 7. 11. Hein C, Owen H, Plummer J. Randomized comparison of the SLIPA (Streamlined Liner of the Pharynx Airway) and the SSLM (Soft Seal Laryngeal Mask) by medical students. Emergency Medicine Australasia 2006; 18: 478–83. 12. Abd Rahman I, Nurlia Y, Wan Rahiza W, Esa K, Nadia M, Raha A. Comparison between the use of LMATM and SLIPATM in patients undergoing minor surgeries. Journal of Surgical Academia 2012; 2: 8–13. 13. Jindal P, Rizvi A, Sharma JP. Is I-gel a new revolution among supraglottic airway devices? – a comparative evaluation. Middle East Journal of Anesthesiology 2009; 20: 53–8. 14. Lange M, Smul T, Zimmermann P, Kohlenberger R, Roewer N, Kehl F. The effectiveness and patient comfort of the novel streamlined pharynx airway liner (SLIPAâ) compared with the conventional laryngeal mask airway in ophthalmic surgery. Anesthesia and Analgesia 2007; 104: 431–4. 15. Miller DM, Camporota L. Advantage of ProSealTM and SLIPATM airways over tracheal tubes for gynecological laparoscopies. Canadian Journal of Anesthesia 2006; 53: 188–93.
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Choi et al. | SLIPA vs LMA systematic review 16. Oh SK, Lim BG, Kim H, Lim SH. Comparison of the clinical effectiveness between the streamlined liner of pharyngeal airway (SLIPA) and the laryngeal mask airway by novice personnel. Korean Journal of Anesthesiology 2012; 63: 136–41. 17. Puri GD, Hegde HV, Jayant A, Bhukal I. Haemodynamic and bispectral index response to insertion of the streamlined liner of the pharynx airway (SLIPATM): Comparison with the laryngeal mask airway. Anaesthesia and Intensive Care 2008; 36: 404–10. 18. Xu J, Zhong TD. Comparison and superiority of streamlined liner of the pharynx airway to laryngeal mask airway or tracheal tubes for gynecological laparoscopy. National Medical Journal of China 2010; 90: 49–52. 19. Cha SM, Park S, Kang H, et al. Gastric distension with SLIPA versus LMA ProSeal during laparoscopic cholecystectomy: a randomized trial. Surgical Laparoscopy Endoscopy and Percutaneous Techniques 2014; 24: 216–20. 20. Vamadevan S, Diba A. The conventional LMA: benchmark for assessing supralaryngeal airway efficacy? Anesthesia and Analgesia 2007; 105: 1508–9. 21. Hooshangi H, Wong DT. Brief review: the Cobra Perilaryngeal Airway (CobraPLA and the Streamlined Liner of Pharyngeal Airway (SLIPA) supraglottic airways. Canadian Journal of Anesthesia 2008; 55: 177–85. 22. Ahn EJ, Hyun K, Choi GJ, et al. Streamlined Liner of the Pharynx Airway: Randomized comparison of size selection strategies with regard to patient height vs. thyroid cartilage width. Hong Kong Journal of Emergency Medicine (in press). 23. Keller C, Brimacombe JR, Keller K, Morris R. Comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients. British Journal of Anaesthesia 1999; 82: 286–7. 24. Keller C, Puhringer F, Brimacombe JR. Influence of cuff volume on oropharyngeal leak pressure and fibreoptic position with the laryngeal mask airway. British Journal of Anaesthesia 1998; 81: 186–7.
Appendix Clinical trial registries searched International Clinical Trial Registry Platform (ICTRP); International Committee of Medical Journal Editors (ICMJE); Clinicaltrials.gov; Australian New Zealand Clinical Trials Registry (ANZCTR); Clinical Research Information Service (CRiS) of Republic of Korea; Brazilian Clinical Trials Registry (ReBec); Chinese Clinical Trial Register (ChiCTR); Clinical Trials Registry of India (CTRI); Cuban Public Registry of Clinical Trials (RPCEC); EU Clinical Trials Register (EU-CTR); German Clinical Trials Register (DRKS); Iranian Registry of Clinical Trials (IRCT); ISRCTN.org; Japan Primary Registries Network (JPRN); Thai Clinical Trials Registry (TCTR); The Netherlands National Trial Register (NTR); Pan African Clinical Trial Registry (PACTR); and Sri Lanka Clinical Trials Registry (SLCTR).
© 2015 The Association of Anaesthetists of Great Britain and Ireland
doi:10.1111/anae.13035
Review Article Comparison of streamlined liner of the pharynx airway (SLIPATM) and laryngeal mask airway: a systematic review and meta-analysis G. J. Choi,1 H. Kang,2 C. W. Baek,3 Y. H. Jung,3 Y. C. Woo,3 S. H. Kim4 and J. G. Kim5 1 Clinical Assistant Professor, 2 Associate Professor, 3 Professor, Department of Anaesthesiology and Pain Medicine, 4 Assistant Professor, 5 Professor, Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea
Summary We performed a systematic review to compare the efficacy and safety of the streamlined liner of the pharynx airway and laryngeal mask airway used in adults during general anaesthesia. We included 14 studies with studies with 1273 patients in total. There was no evidence of a difference between the two devices in insertion success rate on the first attempt (13 studies, 1143 patients), insertion time (seven studies, 576 patients), ease of insertion (five studies, 466 patients), oropharyngeal leak pressure (eight studies, 771 patients) and the quality of the fibreoptic view of the larynx through the device (three studies, 281 patients). The relative risk (95% CI) of bloodstaining of the device (nine studies, 859 patients) was 2.09 (1.46–3.00) for the streamlined liner of the pharynx airway compared with the laryngeal mask airway. Other adverse events were comparable. Subgroup analysis suggested that the insertion by novice users might be faster and more successful with the streamlined liner of the pharynx airway than the laryngeal mask airway; however, this was from only two studies and 186 patients. The method of size selection of the streamlined liner of the pharynx airway device might also affect the speed of insertion: choosing according to the width of the patient’s thyroid cartilage, rather than height, may produce better results. .................................................................................................................................................................
Correspondence to: H. Kang Email: [email protected] Accepted: 13 January 2015
Introduction Supraglottic airway devices have been widely used as alternatives to tracheal intubation during general anaesthesia because of the convenience of insertion and the feasibility of effective positive pressure ventilation [1]. Since the introduction of the classic laryngeal mask airway (LMA) in the late 1980s, various types of LMA have been developed for clinical use with successful results in terms of efficacy and safety [1, 2]. The streamlined liner of the pharynx airway (SLIPATM) is a relatively new, non-cuffed, pharynxshaped disposable supraglottic airway device made of © 2015 The Association of Anaesthetists of Great Britain and Ireland
soft plastic [3]. Several studies have compared the SLIPA with various types of LMA with regard to clinical performance, but the results have been inconsistent. The purpose of this systematic review was to compare the effectiveness and safety of the SLIPA with various types of LMA when used in adults under general anaesthesia.
Methods We developed the protocol for this review and registered with PROSPERO (registration number: CRD42014007139; www.crd.york.ac.uk/PROSPERO), 613
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although we had already commenced data extraction at the time of registration. A systematic review of the literature for studies comparing SLIPA to LMAs in adults undergoing general anaesthesia was conducted according to the protocol recommended by the Cochrane Collaboration [4]. Two authors (SHK and JGK) independently conducted database searches using Embase, MEDLINE, the Cochrane Central Register of Controlled Trials (CENTRAL) and Google Scholar in November 2013; this was updated in October 2014. We also searched for registered trials in the clinical trial registries listed in the Appendix. The search terms included ‘laryngeal mask’, ‘laryngeal mask airway’, ‘LMA’, ‘streamlined liner of the pharynx airway’ and ‘SLIPA’. The reference lists of all identified reports were also searched manually. Randomised controlled trials (including studies with a crossover design) comparing the SLIPA to LMAs in adult patients undergoing general anaesthesia were included. Only peer-reviewed studies were included. There was no limit with respect to the language in which the article was written or the type of LMA used. Two authors (GJC and HK) independently selected eligible studies, and they discussed any differences in opinion to arrive at a consensus as to whether a study should be included or excluded. Disagreement over inclusion or exclusion was settled by discussion with two senior authors (CWB and YHJ). We treated all LMAs, including the classic LMA, ProSealâ LMA, and SoftSealâ LMA, as a single group (LMA group). If the type of LMA was not specified, we assumed that a classic LMA had been used. If studies compared the SLIPA with more than two airway devices including the LMA, only data for the SLIPA and LMA were extracted for analysis. For crossover studies, we included only data for the first period to avoid the possibility of carry-over bias [4]. To deal with missing data, we included dropouts in this analysis on an intention-to-treat basis for dichotomous data [4]. Where participants had been excluded from the trial before the study endpoint, we assumed that they experienced a negative outcome by the end of the trial. We examined the validity of this decision in the sensitivity analyses by applying worst- or best-case scenarios. For continuous data, we extracted data as reported by the authors [4]. We considered device users as 614
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‘novice’ when they had used each type of SLIPA and LMA fewer than five times; otherwise, users were regarded as ‘experienced’. When studies reported outcomes at various time points after anaesthesia, we extracted the data collected in the post-anaesthesia care unit. If the mean and standard deviation were not reported, we attempted to contact the corresponding author to obtain the data, or calculated them based on the methods described in the Cochrane Handbook [4]. Two authors (GJC and YCW) independently extracted the following data: name of the first author; year of publication; whether the trial was registered; type of LMA; number of participants; baseline data (age, weight, and height); methods of selecting the size of device; expertise of device user; type of surgery; use of a neuromuscular blocking drug; rate of insertion success on the first attempt; insertion time; ease of insertion; oropharyngeal leak pressure; fibreoptic view; and complications, assessed both during and after anaesthesia. We also recorded information about study sponsorship or competing interests. The quality of eligible studies was assessed independently by two authors (HK and YCW) using the ‘risk of bias’ tool provided with Review Manager software (version 5.3, The Cochrane Collaboration, Oxford, UK). Quality was evaluated based on the following eight potential sources of bias: random sequence generation; allocation concealment; blinding of the participants; blinding of the outcome assessors during anaesthesia; blinding of the outcome assessors after anaesthesia; incomplete outcome data; selective reporting; and other bias. Each of these domains was graded as ‘high’, ‘low’ or ‘unclear’, to reflect a high risk of bias, low risk of bias and uncertainty of bias, respectively. We computed the pooled relative risk (RR) with corresponding 95% CI for dichotomous data, and weighted mean difference (WMD) or standardised mean difference (SMD) with 95% CI for continuous data. We used the chi-squared test for homogeneity and the I2 test for heterogeneity. We regarded a level of 10% significance (p < 0.10) in the chi-squared statistic or an I2 greater than 50% as considerable heterogeneity, and we then used the Mantel-Haenszel random-effects model. Otherwise, we applied the Mantel–Haenszel fixed-effects model [4, 5]. We carried out subgroup analyses based on: the expertise of the device © 2015 The Association of Anaesthetists of Great Britain and Ireland
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user; the method of SLIPA size selection; the type of LMA; the type of surgery; and the use of neuromuscular blocking drugs. We also conducted sensitivity analyses to evaluate the influence of individual studies from analyses with a heterogeneity of I2 greater than 50% on the overall effect estimate, by excluding one such study at a time from the analysis. We also performed sensitivity analyses based on sponsorship or declared conflicts of interest. Funnel plots were drawn as a measure of publication bias across studies and were assessed visually for symmetry. We also estimated publication bias using Egger’s linear regression test [4]. If the funnel plot was asymmetrical or the p value was < 0.10 on Egger’s test, the presence of a publication bias was considered, and ‘trim and fill’ analysis was performed. We performed all analyses using Review Manager and Comprehensive meta-analysis software (version 2.0, Biostat, Englewood, NJ, USA).
Results The review is reported according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement [6]. The study flow diagram is shown in Fig. 1. One record was excluded as it was a
Records identified through database searching (n– = 290)
conference abstract reporting the same trial as another, full, publication. One study was a thesis identified through hand searching [7], included after discussion with the senior authors (CWB and YHJ), as, although not published, it was a peer-reviewed study. Of the fourteen included randomised controlled trials [3, 7–19], one study was a randomised crossover study [11]. Two studies had been prospectively registered [8, 19]. The SLIPA was compared with the classic LMA in seven studies [7, 12–14, 16–18], with the ProSeal LMA in six [3, 8–10, 15, 19], and with the SoftSeal LMA in one [11]. Three studies compared the SLIPA with two other types of airway device [13, 15, 18], namely: with the classic LMA and the i-gelTM [13]; with the classic LMA and a tracheal tube [18]; and with the ProSeal LMA and a tracheal tube [15]. Selection of the size of SLIPA was based on patients’ height in four studies [9–12] and thyroid cartilage width in eight [3, 7, 8, 15–19]. In two studies [11, 16], novice users inserted the devices: these were either medical students [11] or residents in the department of anaesthesiology [16]. Experienced anaesthesiologists inserted the device in ten studies [7–10, 12–15, 17, 19], one of which presented the detail of experience in response to a later letter to the editor of the journal [20]. Two studies did not
Records identified in clinical trial registries (n = 7)
Records identified through hand searching (n = 2)
174 records after removal of duplicates (n = 125)
Records excluded (n = 157)
Excluded (n = 3) Full-text articles assessed for eligibility (n = 17)
Studies included in meta-analysis (n = 14)
Irrelevant outcome (n = 1) Correspondence (n = 1) Duplicate (conference proceeding) (n = 1)
Figure 1 Flow diagram showing the number of abstracts and articles identified and evaluated during the review process. © 2015 The Association of Anaesthetists of Great Britain and Ireland
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mention operator experience [3, 18]. Twelve reports were written in English [3, 8–17, 19], one was in Korean [7] and one was in Chinese [18]. Devices were provided free of charge in five studies [3, 11, 13, 15, 17]. The author of two of these studies was the inventor of the SLIPA [3, 15]; the other studies reported that there was no competing interest [11, 13, 17]. The study characteristics are summarised in Table 1. All studies mentioned randomisation [3, 7–19], but only ten studies described the method used for sequence generation [3, 8, 10–13, 15–17, 19]. Eight studies reported allocation concealment [8, 10, 11, 13, 15–17, 19]. Blinding of outcome assessment was reported in one study during anaesthesia [19] and seven studies after anaesthesia [3, 8, 10, 11, 14, 17, 19]. Eight studies reported incomplete outcome data [3, 8– 11, 16, 17, 19]. Table 2 summarises the risks of bias for each domain. Sensitivity analyses for heterogeneous outcomes did not show any change in significance of results. We also conducted sensitivity analyses to evaluate the influence of conflict of interest or sponsorship on all outcomes: firstly by excluding the two studies reported by the inventor of the SLIPA [3, 15]; and secondly by excluding the five studies in which airway devices had been provided free of charge [3, 11, 13, 15, 17]. These exclusions did not affect the overall results. A funnel plot was applied for every comparison; all displayed a symmetrical appearance. The results of Egger’s test indicated that publication bias was unlikely for the primary outcomes: rate of insertion success on the first attempt (p = 0.21); insertion time (p = 0.19); ease of insertion (p = 0.08); oropharyngeal leak pressure (p = 0.25); fibreoptic view of the larynx (p = 0.34). On the assumption that ease of insertion showed publication bias, we performed trim and fill analysis to evaluate the influence of publication bias. However, the results from these tests suggested that publication bias was unlikely. All studies (1143 patients) investigated the insertion success rate on the first attempt [3, 7–18]; none reported a significant difference between the groups (RR 1.01, 95% CI 0.97–1.05, p = 0.26, I2 = 19%). We performed a subgroup analysis for expertise of device users. The RR (95% CI) of insertion success on the first attempt was significantly higher in the SLIPA 616
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group when novice users (two studies, 186 patients) inserted the devices, at 1.18 (1.02–1.36), p = 0.56, while it was similar when experienced users (nine studies, 777 patients) inserted the devices, at 0.98 (0.94– 1.02) (Fig. 2). We also conducted subgroup analyses for the method of SLIPA size selection, type of LMA, and use of neuromuscular blocking drugs, all of which showed no evidence of a difference. Insertion time was measured in seven studies (576 patients) [7, 9–11, 13, 16, 17]. There was substantial heterogeneity between studies (I2 = 92%) but no difference in insertion times overall, the WMD (95% CI) being 0.81 ( 2.96 to 1.33) s. For novice users (two studies, 186 patients), the mean (95% CI) insertion time of the SLIPA was 5.5 (10.6–0.3) s shorter compared with LMA insertion (p = 0.63), and I2 dropped to 0%. Insertion times for the two devices was similar when performed by experienced users (five studies, 390 patients), with a WMD (95% CI) of 0.3 ( 2.6 to 2.0) s; I2 was not decreased. On subgroup analysis for SLIPA size selection method (six studies, 526 patients), insertion time was significantly shorter for the LMA than for the SLIPA when selected based on patient height (three studies, 252 patients): WMD (95% CI) 2.0 (0.2–3.9) s, p = 0.12, whereas it was similar between two groups when selecting based on thyroid cartilage width (three studies, 274 patients): WMD (95% CI) 2.5 ( 5.5 to 0.6) s. Insertion time was significantly shorter for the SLIPA compared with the classic LMA (four studies, 324 patients): WMD (95% CI) 2.2 ( 3.8 to 0.6) s (p = 0.01), but significantly longer for the SLIPA compared with the ProSeal LMA (two studies, 180 patients): WMD (95% CI) 2.06 (0–4.1) s (p = 0.05). There was also no evidence of a difference in insertion time whether neuromuscular blockade was used or not (seven studies, 576 patients), with WMD (95% CI) of 0.5 ( 3.7 to 2.7) s with (five studies, 416 patients) and 1.6 ( 4.5 to 1.3) s without (two studies, 160 patients). Five studies (466 patients) evaluated the ease of insertion using different scales [7, 9, 10, 14, 17]. When the best scale in each study was used for analysis, there was no evidence of a difference between the two devices: the RR (95% CI) was 0.88 (0.76–1.02). Eight studies (771 patients) measured oropharyngeal leak pressure, all using the manometric stability technique [3, 7–10, 14, 15, 17]. Overall, oropharyngeal © 2015 The Association of Anaesthetists of Great Britain and Ireland
© 2015 The Association of Anaesthetists of Great Britain and Ireland
51 30 30 30 30 30 30 30 30 50 50 59 65 36 36 50 50 60 60
PLMA SLIPA PLMA SLIPA cLMA SLIPA cLMA SLIPA cLMA SLIPA cLMA SLIPA cLMA SLIPA SSLMA SLIPA PLMA SLIPA PLMA
(33.0–51.8) (34.0–54.8) (14.0) (14.0) (15.9) (15.5) (16.3) (15.8) (17.0)
49.0 43.0 35.2 33.0 36.9 39.9
38.0 38.2 52.8 54.6 46.6 47.7 NR [20–77] [19–81] (8.3) (7.0) (9.8) (11.1)
(8.7) (9.8) (9.4) (8.4) (9.3) (8.8)
43.1 (19.3) 42.0 (19.3) 46.3 (17.8) NR
41.0 45.5 41.8 38.1 46.0 43.8 41.2 37.5 46.6
Age; years (10.3) (13.9) (9.5) (12.0) (5.6) (5.5) (13.8) (15.1) (7.9)
56.8 54.8 53.2 50.6 70.0 75.0 77.0 73.0 66.0 66.0 64.6 64.9
NR (7.8) (6.3) (10) (11.3) (15.0) (12.0) [53–112] [45–100] (10.0) (11.0) (11.1) (9.2)
59.7 (8.3) 64.7 (11.2) 66.5 (15.1) NR
64.4 61.2 61.6 57.2 60.1 58.2 69.9 72.1 60.6
Weight; kg (7.1) (9.9) (6.8) (8.3) (3.9) (4.5) (12.2) (16.3) (5.5)
NR
164.5 163.3 160.2 158.7 170.0 170.0 169.0 170.0 NR
NR (5.5) (7.4) (5.9) (4.9) (11.0) (10.0) [152–183] [150–170]
161.0 (7.4) 168.8 (8.3) 163.2 (15.0) NR
162.9 160.4 162.8 160.5 158.2 157.1 169.1 165.5 159.5
Height; cm
H W T W T W
T S T W NR
W H W T W NR
T W T W H W H W T
NR
> 150 times > 200 times > 10 times Experienced No experience Experienced > 10 times > 3 years Practice with manikin > 100 times
> 1 year > 4 years < 5 times < 5 times > 10 times > 5 years > 100 times > 100 times > 20 times (manikin), > 30 times > 6 years > 20 times > 2 years NR
Expertise of device user
Minor gynaecological procedure
Laparoscopic gynaecological procedure
NR
Minor radiotherapy, gynaecological and general surgery Ophthalmic surgery
Chemoport insertion
Elective surgery
Laparoscopic gynaecological surgery
Elective surgery
Laparoscopic gynaecological surgery
Lower abdominal laparoscopic surgery
Minor surgery
Elective surgery
Laparoscopic cholecystectomy
Type of surgery
No
No
Yes
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Use of NBD
NBD, neuromuscular blocking drug; T, thyroid cartilage width; PLMA, ProSeal LMA; W, patient weight; cLMA, classic LMA; H, patient height; NR, not reported; S, patient sex; SSLMA, SoftSeal LMA.
Miller & Light [3]
Miller & Camporota [15]
Hein et al. [11]
Lange et al. [14]
Puri et al. [17]
Kim [7]
Jindal et al. 2009 [13]
Xu & Zhong [18]
Choi et al. [10]
Woo et al. [8]
Abdellatif & Ali [9]
Abd Rahman et al. [12]
Oh et al. [16]
60 60 57 57 31 31 60 60 50
SLIPA PLMA SLIPA cLMA SLIPA cLMA SLIPA PLMA SLIPA
Cha et al. [19]
n
Group
Study
Device selection method
Table 1 Characteristics of included studies comparing the streamlined liner of the pharynx airway (SLIPA) with the laryngeal mask airway (LMA). Values are number, mean (SD), median (IQR), or median [range].
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617
618
risk risk risk risk risk risk risk risk risk risk risk risk risk risk Low Low Low Low Low Low Low Low Low Low Low Low Low Low Low risk Unclear Unclear Unclear Low risk Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Low risk Low risk Unclear Low risk Low risk Low risk Unclear Unclear Unclear Low risk Unclear Low risk Unclear Low risk Low risk Unclear Low risk Unclear Low risk Low risk Low risk Low risk Unclear Unclear Unclear Unclear Unclear Low risk Low risk Unclear Unclear Unclear High risk Unclear Unclear Unclear Unclear Unclear Unclear High risk Unclear Unclear Unclear Unclear Unclear Unclear Low risk Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Low risk Low risk Low risk Unclear Low risk Low risk Unclear Low risk Unclear Low risk Unclear Low risk Low risk Low risk
Study
Cha et al. [19] Oh et al. [16] Abd Rahman et al. [12] Abdellatif & Ali [9] Woo et al. [8] Choi et al. [10] Xu & Zhong [18] Jindal et al. [13] Kim [7] Puri et al. [17] Lange et al. [14] Hein et al. [11] Miller & Camporota [15] Miller and Light [3]
Low risk Low risk Unclear Unclear Low risk Low risk Unclear Low risk Unclear Low risk Unclear Low risk Low risk Unclear
Blinding of outcome assessment during anaesthesia Blinding of participants Allocation concealment Random sequence generation
Table 2 Assessments of the risk of bias based on Cochrane risk of bias tool.
Blinding of outcome assessment after anaesthesia
Incomplete outcome data
Selective reporting
Other bias
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leak pressure was similar between groups: WMD (95% CI) 0.2 ( 1.1 to 0.8) cmH2O. Excluding one study at a time from the analysis did not affect the overall effect. We conducted subgroup analyses for method of SLIPA size selection, type of LMA, type of surgery and use of neuromuscular blocking drug. Oropharyngeal leak pressure showed marginal significance when selecting based on patient height (two studies, 180 patients): WMD (95% CI) 1.1 ( 2.3 to 0) cmH2O, whereas it was similar when selecting based on thyroid cartilage width (five studies, 467 patients): WMD (95% CI) 0.4 ( 1.2 to 1.9) cmH2O (Fig. 3). There were no significant differences within the subgroup comparisons for type of LMA, laparaoscopic vs other surgery, or use of neuromuscular blockade. Four studies (341 patients) evaluated the fibreoptic view of the larynx through the device using different scales [8–10, 18]; three (281 patients) of these studies mentioned related details [8–10]. We adjusted for the differences before combining data; there was no evidence of a difference; the RR (95% CI) of a good quality fibreoptic view of the larynx was 1.04 (0.84–1.27). Two studies (161 patients) compared perilaryngeal leakage with a change in head position between the SLIPA and the PLMA [8, 10]. One study reported an increased incidence of leakage with the PLMA vs the SLIPA [8], while the other study found similar rates for both devices [10]. Bloodstaining of the supraglottic device was recorded in nine studies (859 patients) [3, 7–10, 12, 14, 17, 19]; the RR (95% CI) was greater with the SLIPA at 2.01 (1.44–2.80) compared with the LMA devices (p = 0.36) (Fig. 4). Gastric insufflation was examined with a stethoscope in four studies (405 patients) [8–10, 14]; the RR (95% CI) of gastric insufflation was greater with the SLIPA at 2.15 (0.28–16.69), but this difference was not significant. Eight studies set out to record regurgitation [8–11, 14, 16–18]; only one instance of regurgitation, associated with use of the SLIPA, was reported in a single study [11]. One study reported one episode of transient bronchospasm in the LMA group and one episode of partial airway obstruction in the SLIPA group [11]. Three studies documented coughing [11, 17, 18]; this was observed once with the SLIPA in each study [11, 17, 18] and once with the LMA in one study [18]. Nine studies (812 patients) reported the incidence of © 2015 The Association of Anaesthetists of Great Britain and Ireland
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Figure 2 Forest plot showing the rate of insertion success on the first attempt: SLIPA vs LMA. Subgroup analyses according to expertise of device users: novice users vs experienced users. M-H, Mantel-Haenszel.
sore throat [7, 9, 10, 12, 14, 16–19], and four (377 patients) evaluated its severity using an 11-point visual analogue scale [9, 10], an 11-point [8] or a 101-point numerical rating scale [17]. The incidence and severity of sore throat were similar between the two groups, with RR (95% CI) 0.95 (0.75–1.21) for incidence and SMD (95% CI) 0.06 ( 0.24 to 0.35) for severity, respectively. Hoarseness (four studies, 394 patients) [9, 16–18] and dysphagia (three studies, 334 patients) [9, 16, 17] were comparable with the two devices, the RR (95% CI) being 0.44 (0.09–2.14) and 0.93 (0.46–1.85), respectively. Postoperative nausea and vomiting was sought in a single study [10] and was observed four times with the SLIPA and three times with the LMA.
Discussion This systematic review with meta-analysis suggests that the SLIPA and the LMA are similarly efficacious in use, as shown by both the rate of successful insertion on the first attempt, and the time taken to insert the © 2015 The Association of Anaesthetists of Great Britain and Ireland
devices. We also found no evidence of a difference between the two devices in ease of insertion, oropharyngeal leak pressure or quality of fibreoptic view of the larynx through the device. Bloodstaining of the device was more commonly noted after use of the SLIPA. Although only two studies examined how novice users performed on inserting the devices, novices seemed to be more likely to successfully insert the SLIPA than the LMA on the first attempt; SLIPA insertion was also more rapid. The SLIPA might be easier for novice users than the LMA because the device has no cuff to inflate and insertion involves fewer steps [11, 16]. This suggests the potential of the SLIPA as the primary supraglottic airway device for users with little prior experience, especially in an emergency. However, the overall rates of successful insertion by novice users of both devices were high, which might be a result of the apparent easy handling of supraglottic airway devices. Furthermore, although the rate of insertion 619
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Figure 3 Forest plot showing the oropharyngeal leak pressure: SLIPA vs LMA. Subgroup analyses according to the method of SLIPA size selection: patient height vs thyroid cartilage width. IV, inverse variance.
Figure 4 Forest plot showing the incidence of bloodstaining on the devices when the SLIPA is compared with the LMA.
success on the first attempt and insertion time were comparable when experienced users performed insertion, those surveyed had more accumulated experience with the LMA than with the SLIPA. This would suggest that it is easy to gain proficiency with the SLIPA, like other supraglottic airway devices [17]. The SLIPA has a preformed fixed shape, which may result in repeated attempts and inadequate sealing within the airway [8, 21]. Therefore, it is important to choose a SLIPA of appropriate size. The 620
manufacturer recommends that SLIPA size is selected based on the patient’s height. The other known method of size selection is to compare thyroid cartilage width with the widest point of the SLIPA [3, 15]. Our subgroup analysis has illuminated this question: SLIPA insertion took longer than LMA insertion when selection was based on height, but insertion times were similar when selection was based on thyroid cartilage width. This discrepancy between the two selection methods may suggest that SLIPA size selection © 2015 The Association of Anaesthetists of Great Britain and Ireland
Choi et al. | SLIPA vs LMA systematic review
based on patient height is less accurate. Woo et al. mentioned that the manufacturer’s size rule was imprecise owing to size overlap [8]. The study that compared two selection methods reported that the method based on thyroid cartilage width was better in terms of oropharyngeal leak pressure and need for manipulation during SLIPA insertion [22]. Thus, clinical efficacy of the SLIPA may depend crucially on proper size selection. The oropharyngeal leak pressure determines the feasibility of positive pressure ventilation and hence the degree of airway protection provided by supraglottic airway devices [23]. The efficacy of the LMA seal depends on the fit between the oval groove surrounding the glottis and the oval cuff of the LMA [24]. Despite the lack of an inflatable cuff with the SLIPA, we found no evidence of a difference in oropharyngeal leak pressure between the two devices. As the shape of the SLIPA more closely resembles peripharyngeal anatomy [3], it may seal the airway effectively if size selection is suitable. Moreover, Woo et al. demonstrated that perilaryngeal leakage with a change in head position was more common with the PLMA than with the SLIPA, which might be associated with the fact that the shape of the SLIPA device is similar to that of the pharynx [8]. There were no serious complications with either device. No statistically significant difference was found between the two devices in the incidence of complications, except for bloodstaining on the devices. This complication, reflecting direct trauma to the pharyngeal mucosa or other structures, was not thought to be clinically significant. The incidence and severity of sore throat were comparable between the two groups. The SLIPA is constructed of stiffer plastic material than the LMA, which is made of silicone, and might cause more mucosal injury to the deeper pharyngeal structures [8, 10], which in turn may explain the higher incidence of bloodstaining on the SLIPA. Gastric insufflation can result from the inappropriate sealing of a supraglottic airway device. The result that gastric insufflation was comparable between groups may correlate with similar levels of oropharyngeal leak pressure. There was no report of regurgitation except in one case of SLIPA use; this did not lead to aspiration. © 2015 The Association of Anaesthetists of Great Britain and Ireland
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The present review has several limitations. First, only one study reported that assessment of outcomes noted during anaesthesia was blinded [19]. This may be insufflation was because of the challenge posed by clear differences in the appearances of these airway devices. However, outcomes during anaesthesia such as insertion time, oropharyngeal leak pressure, fibreoptic view and gastric insufflation were objective measurements. A successful or failed attempt at insertion was determined based on objective criteria. Second, some outcomes were heterogeneous. Insertion time showed substantial heterogeneity, which was most likely to be due to differences in: the expertise of the device users; the method for device size selection; the type of LMA; the use of neuromuscular blocking drugs; induction or maintenance of anaesthesia; anaesthesia depth; the range of definitions of insertion times; and the permissible number of attempts at successful insertion. In spite of the fact that we tried to conduct subgroup analyses for some of these factors, we could not take all of them into account. Third, experienced users in most studies would be expected to have greater accumulated experience with the LMA compared with the SLIPA, which may have introduced bias. However, the steep learning curve for use of the SLIPA seems to offset any discrepancy with regard to experience. Our study has demonstrated strength, notwithstanding these limitations, by applying rigorous methodology to provide the first systematic review comparing SLIPA and LMA devices used under general anaesthesia. In conclusion, the SLIPA was similar to LMAs with respect to the rate of insertion success on the first attempt, insertion time, ease of insertion, oropharyngeal leak pressure and quality of fibreoptic view of the larynx. The incidence of bloodstaining on the devices was greater in the SLIPA than in the LMA, but the other complications were similar. The selection of SLIPA size may be better based on thyroid cartilage width than patient height.
Acknowledgements This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A1A1 003700). 621
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Competing interests No competing interests declared.
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Appendix Clinical trial registries searched International Clinical Trial Registry Platform (ICTRP); International Committee of Medical Journal Editors (ICMJE); Clinicaltrials.gov; Australian New Zealand Clinical Trials Registry (ANZCTR); Clinical Research Information Service (CRiS) of Republic of Korea; Brazilian Clinical Trials Registry (ReBec); Chinese Clinical Trial Register (ChiCTR); Clinical Trials Registry of India (CTRI); Cuban Public Registry of Clinical Trials (RPCEC); EU Clinical Trials Register (EU-CTR); German Clinical Trials Register (DRKS); Iranian Registry of Clinical Trials (IRCT); ISRCTN.org; Japan Primary Registries Network (JPRN); Thai Clinical Trials Registry (TCTR); The Netherlands National Trial Register (NTR); Pan African Clinical Trial Registry (PACTR); and Sri Lanka Clinical Trials Registry (SLCTR).
© 2015 The Association of Anaesthetists of Great Britain and Ireland
