The widespread use of supraglottic airway devices has revolutionised clinical anaesthesia and offers a genuine alternative to tracheal intubation in certain situations. One example is laparoscopic surgery, an approach that may increase the risk of regurgitation due to peritoneal insufflation. The safety of the Laryngeal Mask Airway Proseal (LMAP) in this setting, with its high seal pressure and gastric drain tube, has been established.1–4
The LMA Supreme (LMAS) has recently been added to the LMA family as a new single-use device that shares attributes with LMA Fastrach and LMAP. Its curved shape makes it easy to insert and the effective oropharyngeal seal pressure together with drain tube allows the LMAS to be used in laparoscopic surgery. Studies to date have not achieved a consensus regarding leak pressures of the LMAS and LMAP, and there is little information on laparoscopic cholecystectomy because most studies have investigated gynaecological laparoscopy.
The purpose of this prospective randomised study was to compare the LMAS and LMAP in fasted adults undergoing elective laparoscopic cholecystectomy. Our primary outcome was the oropharyngeal leak pressure (OLP). Our secondary outcomes were as follows: number of attempts, ease of insertion of the device and the gastric tube, time to reach correct ventilation and adverse events including postoperative sore throat.
Materials and methods
Ethical approval for this study was provided by the Ethical and Investigation Committee of the Hospital Universitario del Sureste, Arganda del Rey, Madrid, Spain (Chairperson Dr F.J. Yuste) on 15 May 2009. After written informed consent, fasted patients of American Society of Anesthesiologists Physical Status (ASA) classes I to III undergoing elective laparoscopic cholecystectomy were recruited. Patients were excluded if they were less than 18 years, having ASA class IV or V, with BMI more than 40 kg m−2, symptomatic hiatus hernia or severe gastro-oesophageal reflux.
Patients were randomly allocated using computer-generated numbers. Allocation was concealed using opaque sealed envelopes that were opened just prior to induction of general anaesthesia.
The size of LMAS and LMAP was chosen according to the manufacturer[Combining Acute Accent]s recommendations based on weight (size 3 for patients weighing 30 to 50 kg; size 4, 50 to 70 kg and size 5, >70 kg).5 All the devices were completely deflated to standardise the comparison between the devices. The posterior surface of the LMA was lubricated with a water-soluble lubricant (Sulky; Laboratorios Bohm S.A., Madrid, Spain).
Routine monitoring of electrocardiograph, non-invasive blood pressure and pulse oximetry was begun before induction of anaesthesia. All patients were premedicated with midazolam 0.04 mg kg−1 and remifentanil 0.1 μg kg−1 min−1 intravenously (i.v.). Anaesthesia was induced in the supine position with the head on a standard pillow 7 cm in height. After preoxygenation for 3 min, remifentanil 0.3 μg kg−1 min−1 and propofol 2 to 3 mg kg−1 were given. No muscle relaxant was used at this time. We continued ventilating with 100% oxygen using a facemask for at least 1 min until optimum conditions for LMA insertion were achieved (relaxation of the jaw, loss of eyelash reflex, immobility and apnoea). The LMAS was inserted with the head in the ‘semi-sniffing’ position using a single-handed technique such as that suggested by the manufacturer.5 The LMAP was inserted using the manual technique in the ‘sniffing’ position. Cuff pressure was monitored using a handheld manometer (Ambu, Ballerup, Denmark) to achieve 60 cmH2O in both devices. A closed circle system was connected (inspired tidal volume 8 ml kg−1, respiratory rate of 12 breaths min−1, I: E ratio of 1 : 2 and fresh gas flow 3 l min−1). Effective ventilation was defined as a square-wave tracing on the capnograph with end-tidal CO2 (EtCO2) values from 30 to 45 mmHg and normal thoracoabdominal movements. The LMA was repositioned if necessary to achieve this. The number of insertion attempts was recorded. Three attempts were allowed before insertion was considered a failure. The anaesthesiologist ventilated the patient using the facemask between attempts. The time taken for insertion was defined as the time from removing the facemask to the first valid capnography trace. Drain tube air leaks were detected by placing lubricant into the drain tube and detecting upcoming bubbles during ventilation. When mechanical ventilation was ineffective (maximum expired tidal volume <6 ml kg−1 or EtCO2 >45 mmHg), the cuff was deflated to zero pressure and the LMA repositioned by gentle ‘up and down’ or lateral movements. If ventilation continued to be suboptimal, one further insertion attempt was allowed. When ventilation was impossible or ineffective after the third attempt, we defined it as ventilation failure. In case of insertion or ventilation failure, endotracheal intubation was performed.
A well lubricated 120 cm long, #14 Salem sump gastric tube (Vecmedical Spain S.L., Barcelona, Spain) was inserted via the drain tube and ease of insertion was recorded (easy to insert, difficult to insert and impossible to insert). Finally, we secured the LMA to the face with adhesive tape. Four anaesthesiologists experienced in the use of LMA Classic (>1000 uses), LMAP (>100 uses) and LMAS (>50 uses) participated in the trial. A second anaesthesiologist was available to collect data as an independent observer.
Anaesthesia was maintained with sevoflurane (2% end-tidal) in 50% oxygen in air, and remifentanil 0.15 to 0.5 μg kg−1 min−1. Once ventilation and anaesthesia had stabilised, the expiratory valve of the circle system was closed at a fixed gas flow of 3 l min−1, and the OLP was recorded. This was the airway pressure generated (for safety, the maximum allowed was 40 cmH2O) when an audible noise was heard over the mouth.6 After that, rocuronium 0.6 mg kg−1 was given to maintain neuromuscular blockade at one twitch of a train-of-four (TOF-Watch; Organon Ltd, Dublin, Ireland).
We recorded the peak airway pressure from the anaesthesia system Fabius GS (Dräger Medical AG & Co.KG, Lübeck, Germany). Peak airway pressures were recorded before and after the carboperitoneum in the supine position and in the reverse Trendelenburg position. Peritoneal insufflation pressure was set at 13 mmHg7 and head-up tilt was limited to 30°.
Cardiorespiratory data were collected every 3 min during the anaesthetic procedure by the monitoring computer program (Picis Care Suit Anesthesia Manager; Picis Ltd, Wakefield, MA, USA). Ventilatory variables were monitored continuously and adjusted accordingly to maintain SpO2 more than 95% and EtCO2 less than 45 mmHg. Peritoneal insufflation time and total anaesthetic time were also recorded.
The LMA was removed when the patient was awake and responded to verbal orders. The presence of any of the following complications was recorded by the observer: cough, laryngeal stridor, laryngospasm, bronchospasm, regurgitation, aspiration, hypoxia (SpO2 <90%) and presence of blood following removal of the LMA. After monitoring in the postoperative acute care unit (PACU), a second assessor blinded to the allocation group, assessed the patients for postoperative pain using a verbal questionnaire which evaluated the presence of sore throat, pain on swallowing and pain on speaking, before leaving the operating room (0 h) and postoperatively in the PACU (2 h) using a 0 to 10 visual analogue scale (VAS) where 0 = absence of sore throat, dysphagia or dysphonia and 10 = unbearable sore throat, total dysphagia or dysphonia. All the patients received a standard postoperative analgesic regime of paracetamol (1 g) and dexketoprofen (50 mg) i.v.
Our sample size was based on the results of a previous study, in which the LMAP was found to have an OLP of 25 cmH2O with a standard deviation of 6 cmH2O.8 To detect a clinically significant difference of 10% between the two groups, with α equal to 0.05 and power of 85% (1−β = 0.85) using a two-sided test, 57 patients per group were needed. This was increased to 60 to allow for the potential for dropout.
We analysed the data with SPSS version 17 (SPSS Inc., Chicago, Illinois, USA). Continuous data were analysed using Student's t-test. Non-parametric data were analysed using the two independent samples Mann–Whitney test. Nominal data were analysed with the χ2 test. Logistic regression was used to determine the factors associated with OLPs. A P value less than 0.05 was considered significant.
Two patients were excluded when the surgical approach changed from laparoscopy to laparotomy, and these were replaced, leaving 120 (60 per group) for analysis. Personal data were similar for both groups (Table 1).
The mean OLP with the LMAS group was significantly lower than that in the LMAP group (26.8 ± 4.1 versus 30.7 ± 6.2 cmH2O; P < 0.01). This finding was consistent with a lower maximum tidal volume achieved with the LMAS compared to the LMAP (475 ± 55 versus 511 ± 68 ml; P = 0.04) and matched the OLP values.
Success rate on first attempt insertion was higher for the LMAS group than the LMAP group (96.7 and 71.2%, respectively; P < 0.01). The median time taken for insertion was similar (11.78 s in the LMAS versus 11.20 s in the LMAP; P = 0.2). There were no failed insertions in either group. More than 95% of insertions were reported to be easy for both devices. Only two cases were graded as difficult in the LMAP group, and none in the LMAS group (Table 2).
There was no statistical difference in ease of insertion of the drain tube (P = 0.06). Intraoperative complications were similar in both groups. No episodes of laryngeal stridor/laryngospasm/bronchospasm, hypoxia, regurgitation or aspiration were seen. Cough at the time of withdrawal occurred in five patients (8.3%) in LMAS group and six (10%) in LMAP group. Blood was noted after removal of the LMAP in two cases. There were no differences between LMAS and LMAP with respect to incidence of postoperative sore throat (P = 0.13 at 0 h and P = 0.06 at 2 h). No patients reported dysphagia or dysphonia.
The findings of our study show that OLP in the LMAS group was lower than that in the LMAP group. Based on the results of secondary outcomes, the LMAS was easier to insert than LMAP. We did not find any significant differences with respect to insertion of the drain tube, incidence of postoperative sore throat or other adverse events.
There are many reports of the use of the LMA for laparoscopic surgery, mostly testing the LMA Classic against the LMAP1–3,9, and more recently, the LMAS4,10,11 and the I-gel7,12 for laparoscopy. This is the first clinical study comparing safety and efficacy of LMAS and LMAP in patients undergoing laparoscopic cholecystectomy.
The majority of previous studies only included ASA I and II patients. We were not restrictive and as a result, 10.8% of the patients were ASA III. Our exclusion threshold for BMI excluded those with a BMI greater than 40 kg m−2 but permitted inclusion of eight with BMI between 30 and 40 kg m−2. In this subgroup, although small, both LMAS and LMAP proved to be safe during laparoscopy, with no leaks measured and achieving adequate ventilation.
OLP test is commonly performed to quantify the seal with the airway when a supraglottic device is used. OLP values have been widely used as a reference for the assessment of safety of different masks. The leak pressure can indicate the success of positive pressure ventilation and the degree of airway protection6 and is regarded as the most important value when testing the suitability of a LMA for laparoscopic surgery.3,13
Several clinical studies have compared the OLP in LMAS versus LMAP with different results. Verghese and Ramaswamy14 presented a prospective randomised crossover study of 36 patients comparing LMAS and LMAP. This study showed no differences in OLP between devices, although it only included female patients with a size 4 LMA. Hosten et al.15 in another prospective randomised trial found similar OLP values between LMAS and LMAP, although in this case, only 12 of the 60 patients included underwent laparoscopic procedures, and muscle relaxants were used in 22%, which may have affected the measured OLP.
Two other investigators have found differences in mean OLP values between LMAS and LMAP,8,16 finding that OLP was 4 to 8 cmH2O lower in the LMAS compared to the LMAP group, although in both cases, the procedures were non-laparoscopic. Our findings are consistent with theirs and with those of Lee et al.4 The results of this prospective, controlled, randomised study of 70 female patients (ASA I to II) undergoing elective gynaecological procedures, are comparable to ours, although there are some differences worthy of note. Their study sample size was smaller, all patients were women and mivacurium was administered before measurement of OLP. We decided not to use muscle relaxants before insertion of the LMA, because the device can be inserted easily without their administration if an adequate depth of anaesthesia is reached,17 and there is some evidence suggesting that the use of neuromuscular blocking agents can alter the LMA leak pressures and may result in a lower measured OLP.18 We did, however, provide neuromuscular blockade during laparoscopy.
The higher OLP for the LMAP is mainly related to the dorsal cuff and the silicone rubber double cuff design compared to the polyvinyl chloride single cuff of the LMAS. Some authors19 have suggested that the lower OLP observed in LMAS may be due to the movement of the semi-rigid curved airway tube, something which does not seem to happen with the elastic tube of the LMAP.
The I-gel supraglottic airway device has recently been compared with the LMAP and the LMAS separately, looking for differences in OLP in laparoscopic surgery. In one study, a higher OLP was reached with the LMAP,12 but no differences were found between the I-gel and the LMAS regarding OLP values.7
Another important aspect that should be considered is the ease of insertion. In our study, we found a superior success rate on the first attempt in the LMAS group compared to the LMAP. Similar results were found by Seet et al.,8 but we did not find any differences in the median time taken for insertion. The curved semi-rigid airway tube of the LMAS, similar to the intubating LMA Fastrach, may facilitate the insertion of this device and may explain why none of the insertions in the LMAS group were graded as difficult. Some authors have proposed a guide insertion technique for the LMAP to improve digital insertion,20 but this would require training. Most of the studies comparing LMAS and LMAP have failed to demonstrate any differences in the success rate at first insertion,4,15,16 but neuromuscular blocking agents were used, and the more favourable conditions created can influence the results. Moreover, the sample size was too small to detect any difference, as the maximum number was 93 in the study by Eschertzhuber et al.16 We agree with Pearson and Young21 that the LMAS is a real option for airway rescue situations, in which there is no immediate access to suitable help and emergency intubation is an unacceptable risk.
Despite the fact that both devices have been manufactured using different materials, we found no differences in gastric tube placement.
The complication rate in our study was low in both groups, which is comparable to other reports that evaluated these airway devices.4,22 Nor were there significant differences in the incidence of sore throat.8,22–24 Mucosal injury, recognised by blood on the device after removal, was present in only 1.7% of patients in the LMAP group (no cases in the LMAS group), which is less than that in other reports4,8,23,25 and the incidence of cough was low and comparable for both masks. Consistent with other studies, dysphagia or dysphonia and other adverse events, such as laryngeal stridor, laryngospasm, bronchospasm, hypoxia, regurgitation or aspiration and neurovascular events were not reported.8,13,17. On the basis of these findings, we suggest that LMAS and LMAP are effective ventilatory devices for laparoscopic cholecystectomy with a low morbidity.
Our study has some limitations. First, and for obvious reasons, the anaesthesiologist involved in timing the events in the operating room was not blind to the type of device. To mitigate this, postoperative outcome assessors and patients were blinded to the group assignment. Second, we only investigated one type of surgery, although laparoscopic procedures are valuable for studying the safety and efficacy of these devices.
In conclusion, we found that the LMAP had a higher OLP and achieved a higher maximum tidal volume compared to the LMAS, in patients undergoing general anaesthesia for elective laparoscopic cholecystectomy. The success rate of the first insertion was higher for the LMAS group and this could have important implications when using the LMAS as an airway rescue device. The ease of insertion of the drain tube, adequacy of ventilation and complication rates are comparable for the two airway devices.
Assistance with the study: the authors wish to thank Francisco J.Yuste, MD, PhD for his cooperation and interest in this study.
Financial support and sponsorship: none declared.
Conflicts of interest: none declared.
1. Maltby JR, Beriault MT, Watson NC, et al. The LMA-ProSeal is an effective alternative to tracheal intubation for laparoscopic cholecystectomy
. Can J Anesth
2. Maltby JR, Beriault MT, Watson NC, et al. LMA-Classic and LMA-ProSeal are effective alternatives to endotracheal intubation for gynecologic laparoscopy. Can J Anesth
3. Natalini G, Lanza G, Rosano A, et al. Standard Laryngeal Mask Airway and LMA-ProSeal during laparoscopic surgery. J Clin Anesth
4. Lee AK, Tey JB, Lim Y, Sia AT. Comparison of the single-use LMA Supreme with the reusable Proseal LMA for anaesthesia in gynaecological laparoscopic surgery. Anaesth Intensive Care
5. The LMA Supreme. Instruction manual.
Maidenhead, Berkshire, UK: Intavent Orthofix Ltd; 2007.
6. 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. Br J Anaesth
7. Teoh WH, Lee KM, Suhitharan T, et al. Comparison of the LMA Supreme vs I-gel in paralysed patients undergoing gynaecological laparoscopic surgery with controlled ventilation. Anaesthesia
8. Seet E, Rajeev S, Firoz T, et al. Safety and efficacy of Laryngeal Mask Airway Supreme
versus Laryngeal Mask Airway Proseal
: a randomized controlled trial. Eur J Anaesthesiol
9. Lu PP, Brimacombe J, Yang C, Shyr M. ProSeal versus the Classic Laryngeal Mask Airway for positive pressure ventilation during laparoscopic cholecystectomy
. Br J Anaesth
10. Abdi W, Amathieu R, Adhoum A, et al. Sparing the larynx during gynaecological laparoscopy: a randomized trial comparing the LMA Supreme and the EET. Acta Anaesthesiol Scand
11. Yao T, Yang XL, Zhang F, et al. The feasibility of Supreme Laryngeal Mask Airway in gynaecological laparoscopy surgery. Zhonghua Yi Xue Za Zhi
12. Sharma B, Sehgal R, Sahai C, Sood J. PLMA vs. I-gel: a comparative evaluation of respiratory mechanics in laparoscopic cholecystectomy
. J Anaesthesiol Clin Pharmacol
13. Timmermann A, Cremer S, Eich C, et al. Prospective clinical and fiberoptic evaluation of the Supreme Laryngeal Mask Airway. Anesthesiology
14. Verghese C, Ramaswamy B. LMA-Supreme: a new single-use LMA with gastric access – a report on its clinical efficacy. Br J Anaesth
15. Hosten T, Gurkan Y, Ozdamar D, et al. A new supraglottic airway device: LMA Supreme, comparison with LMA-ProSeal. Acta Anaesthesiol Scand
16. Eschertzhuber S, Brimacombe J, Hohlrieder M, Keller C. The Laryngeal Mask Airway Supreme
: a single use laryngeal mask airway with an oesophageal vent. A randomized, cross-over study with the Laryngeal Mask Airway ProSeal
in paralyzed, anaesthetised patients. Anaesthesia
17. Beleña JM, Gracia JL, Ayala JL, et al. The Laryngeal Mask Airway Supreme
for positive pressure ventilation during laparoscopic cholecystectomy
. J Clin Anesth
18. Goldmann K, Hoch N, Wulf H. Influence of neuromuscular blockade on the airway leak pressure of the Proseal Laryngeal Mask Airway. Anasthesiol Intensivmed Notfallmed Schmerzther
19. Strube PJ. The LMA Supreme and LMA Proseal. Anaesthesia
20. Brimacombe J, Keller C. Gum elastic bougie-guided insertion of the Proseal Laryngeal Mask Airway. Anaesth Intensive Care
21. Pearson DM, Young PJ. Use of the LMA-Supreme for airway rescue. Anesthesiology
22. López AM, Valero R, Hurtado P, et al. Comparison of the LMA Supreme with the LMA Proseal for airway management in patients anaesthetized in prone position. Br J Anaesth
23. Cook TM, Lee G, Nolan JP. The ProSeal Laryngeal Mask Airway: a review of the literature. Can J Anaesth
24. Alexander CA, Leach AB. Incidence of sore throats with the LMA. Anaesthesia
25. Brimacombe J, Keller C, Fullekrug B, et al. A multicenter study comparing the ProSeal and Classic Laryngeal Mask Airway in anesthetized, nonparalyzed patients. Anesthesiology