Since the introduction of the classical laryngeal mask airway (cLMA) into clinical medicine by Brain,1 various supraglottic airway devices (SADs) have been developed for use in elective surgery and emergency medicine. The modifications and enhancements to the cLMA are aimed at improving ease of insertion, patient comfort and safety.2 An effective airway seal is an important surrogate for safety, as it is believed to correlate with protection against the aspiration of gastric contents. In addition, several devices have been provided with an oesophageal tube to enable the of draining gastric content to prevent aspiration. The laryngeal tube suction II (LTS II) is a dual lumen SAD (Fig. 1), which is designed for blind insertion into the oropharynx. It is equipped with two low-pressure cuffs to seal the oesophagus and pharynx, and both cuffs are inflated by a common tube. During insertion, the tip of the LTS II is placed blindly at the entry of the oesophagus, providing an additional lumen to release gastric pressure. The LTS II is based on the concept of the combitube, originally developed by Frass et al.3 as an alternative to endotracheal intubation during resuscitation. Several investigators described the use of the LTS and LTS II in elective surgery.4–10 Due to its ease of insertion, even by untrained personnel,11 it has been proposed as an alternative to intubation during cardiopulmonary resuscitation12 and for difficult airway situations.13
When compared with the cLMA, the LTS II provides an oesophageal sealing pressure up to 82 cmH2O,14 indicating that the LTS II may be superior for controlled mechanical ventilation in patients with elevated intra-abdominal pressure or for ventilation in the Trendelenburg position. In the presented study, we compared the LTS II with an endotracheal tube to assess the safety and efficacy of airway management during controlled mechanical ventilation for elective laparoscopic radical prostatectomy.
The study was approved by the local ethics committee of the Medical Faculty of the University of Leipzig (ref: 445/12-bk, 17 April 2014, Chairman Prof Dr R. Preiß) and registered with the German Clinical Trials Register (ref: DRKS00008985). Patients were identified by one of the responsible anaesthetists after surgery was planned. All patients gave written informed consent. Immediately before induction of anaesthesia, patients were randomly assigned to either the LTS II or endotracheal tube group in a 1 : 1 ratio. Randomisation was achieved using a computerised algorithm. Both patients and surgeons were blinded as to the type of airway device. Data were collected in a database sheet on the study site.
We investigated patients who were selected for elective laparoscopic radical prostatectomy at the University Hospital of Leipzig between April 2014 and May 2015; due to the nature of the underlying disease, only male patients aged more than 18 years were included. Exclusion criteria were a BMI more than 30, American Society of Anesthesiologists (ASA) class III or greater, any history of gastroesophageal reflux or other known risk of aspiration and a known difficult airway. Induction of anaesthesia was with propofol (1.5 to 2.5 mg kg−1), sufentanil (0.2 to 0.4 μg kg−1) and rocuronium bromide (0.5 mg kg−1). Neuromuscular blockade was monitored by acceleromyography, and the airway device was inserted when the train-of-four count was 0. The primary endpoint was successful use of the particular airway device during endoscopic radical prostatectomy. The attending anaesthetist determined ‘successful use’ based on the initial appropriate insertion of the airway device, subsequent adequate ventilation (no audible or measurable leakage, normocapnia, peak inspiratory pressure ≤35 cmH2O) and with no other device-associated complications. Secondary endpoints of the study included the initial success rates for insertion within two attempts, ease of insertion, time to first effective breath, doses of anaesthetics and the quality of ventilation. Criteria to switch from LTS II to endotracheal tube were audible or measurable airway leaks, peak inspiratory pressure more than 35 cmH2O and other complications. The decision to switch was at the discretion of the attending anaesthetist.
Quality of ventilation (i.e. minimal straining against the ventilator by the patient, stable oxygen saturation, normocapnia and none or only minor adjustments to ventilator settings or sedation were required), ease of insertion and quality of surgical condition were rated subjectively by the attending physicians on a numerical rating scale (NRS) as follows: 1 to 2 – very poor, 3 to 4 – poor, 5 to 6 – sufficient, 7 to 8 – good and 9 to 10 – excellent. Patients were visited 4 and 24 h after extubation and were asked about sore throat, dysphagia and traumatic lesions that could be explained by the airway device, and difficulties of swallowing (numerical rating from 0 = no complaints to 10 = maximum complaints).
Placement of the devices was supervised by one of four experienced anaesthetists who had learned how to place the LTS II prior to the start of the study. Time to insertion, number of attempts and the ease of insertion as well as airway seal and the quality of ventilation were recorded immediately after induction. Before the surgeon entered the surgical theatre, the patient's head was covered so that the surgeon was blinded as to the type of the device in use. All operations were performed by one of four experienced surgeons. Laparoscopic prostatectomy procedures are highly standardised in our hospital and were performed following the local written standard operating procedure. The procedure is minimally invasive using a pneumoretroperitoneum with only slightly increased intra-abdominal pressure with the patient placed supine in a 20 to 30° Trendelenburg position. The procedure has been described in detail elsewhere.15 Anaesthetics, opioids and relaxants were administered to individual patients at the discretion of the anaesthetist. Immediately after the end of the surgical procedure, the surgeon rated the surgical conditions experienced during the surgery. Reversal of anaesthesia was not commenced until after the surgeon had left the operating theatre so as to ensure blinding. The airway device was removed when the patient was awake and showed sufficient spontaneous breathing. All patients were monitored for at least 8 h in the postanaesthesia care unit.
For data compilation and statistical analysis, Excel 2003 (Microsoft Corp., Redmond, Washington, USA) and SPSS statistics 20 (IBM Corp., Armonk, New York, USA) were used. Groups were compared with the Mann–Whitney U test, the chi-square test or the Fisher's extract test, as appropriate. With the intended inclusion of 100 patients, the study power was 80% to detect a statistically significant difference in the primary endpoint of more than 15% between the groups.
Of the 352 patients scheduled for radical prostatectomy, only 50 were included in the study. Figure 2 shows the reasons for non-inclusion. No patients were excluded after randomisation. The first patient was enrolled on 23 April 2014 (Fig. 2). The study was stopped after 50 patients when, due to safety concerns, an unplanned interim analysis was performed. This revealed that in 15 of the 28 patients randomised to the LTS II, the airway device had to be changed to an endotracheal tube. Due to this high complication rate, it was decided to stop further patient recruitment, and the ethics committee was informed accordingly. In all 22 patients randomised to the endotracheal tube, ventilation was successful until the procedure was ended.
There were no significant differences in BMI, distribution of ASA class I and II or Mallampati scores between the two groups (Table 1). The Cormack and Lehane grade to evaluate the potential difficulty of endotracheal intubation was analysed only for patients in the endotracheal tube group and for those patients who were changed over from LTS II to endotracheal tube. The duration of the surgery, as well as the anaesthesia time (anaesthetic induction to the end of anaesthesia recovery), was shorter in the endotracheal tube group, but only the difference in anaesthesia time was statistically significant (Table 1). The doses of propofol and opioids were similar in both groups. Neuromuscular blockade, monitored by acceleromyography, was adjusted at the discretion of the attending anaesthetist. There was no difference in the use of neuromuscular blocking drugs between the LTS II and the endotracheal tube groups.
Insertion at the first attempt occurred in 75% of the LTS II patients and in 80% of endotracheal tube patients. Successful insertion after the first and second attempts were 86% in the LTS II and 100% in the endotracheal tube group (P = 0.12). The insertion of the LTS II was rated easier than the endotracheal tube, but without reaching statistical significance. There were seven patients in the LTS II group in whom the airway device could not be inserted at the first attempt (median NRS, 8.5) and four of 22 patients in the endotracheal tube group (median NRS, 7) (P = 0.31).
With regard to the surgical conditions as rated by the surgeons, overall there was no statistically significant difference between the groups (Table 2). However, only one endotracheal tube case scored less than 6, but there were four such cases in the LTS II group (Fig. 3) and three of the latter required endotracheal intubation. The quality of ventilation was rated better in the endotracheal tube group (P = 0.01) (Table 2).
Fifteen patients in the LTS II group had their SAD changed to an endotracheal tube. The most frequent reason for this change was cuff leakage (10 patients) followed by swelling of the tongue (three patients). In one patient, ventilation with the LTS II was not possible at any time. In six patients, the device was switched during induction of anaesthesia, in six patients after induction but before skin incision and in three patients after skin incision. In one patient during LTS II use, aspiration was suspected but this was not confirmed after switching to an endotracheal tube.
Dysphagia at 4 and 24 h after surgery was frequent but mild, and there was no difference between the LTS II and endotracheal tube groups. Few patients had severe sore throat, and most of these were in the LTS II group (Fig. 4). The two patients with the highest NRS (6 and 9 points) had had their LTS II changed to an endotracheal tube. However, the overall difference in sore throat did not reach statistical significance. Only one patient in the endotracheal tube group had any detectable lesion (swollen bottom lip).
In this study, we compared the LTS II with an endotracheal tube for ventilation of the lungs in patients undergoing elective laparoscopic radical prostatectomy. We evaluated both airway devices with regard to successful use during the entire surgical procedure, insertion success, insertion condition, quality of ventilation, surgical conditions and patients’ comfort.
Previous studies had showed that the original laryngeal tube suction can be used safely in laparoscopic surgery7,16,17; therefore, we hypothesised that the LTS II, due to its superior characteristics, could be safely used during more challenging conditions.
The major findings of our study were as follows:
- A substantial proportion of patients had to be switched from the LTS II to an endotracheal tube due to an airway leak or engorgement of the tongue.
- A reduced insertion success rate with two attempts in patients in the LTS II group when compared with the endotracheal tube group.
Data for success rates of LTS II placement differ in the literature. Although some authors demonstrated success in 89 to 100%5,7,8 of patients, we observed a lower rate of successful placement of the LTS II (75% at the first attempt), which is consistent with results of Kikuchi et al.6 In contrast, with the original LTS, Russo et al.10 observed a successful insertion rate of only 53% at the first attempt with an overall success of 70%. As all studies, including ours, have rather low numbers, it may be that different levels of operator experience might contribute to this variation in success rates. In our study, the LTS II was suitable for initial ventilation in all but one patient, and no aspiration of gastric content was confirmed.
Three patients developed a swollen and cyanotic tongue following insertion of the LTS II, resulting in the LTS II being changed for an endotracheal tube within 10 min. Engorgement of the tongue during LTS II use is probably a result of high pressure to the root of the tongue. As a potential complication of the laryngeal tube device, this has been reported in several other investigations.18–20 Mihai et al. described one case in 100 uses.4 In our study, the incidence was remarkably high, although cuff volumes were chosen following the manufacturers’ recommendations, and the cuff pressure was limited to a maximum of 60 cmH2O. It has been demonstrated that high cuff volumes in SADs may lead to a reduction of mucosal perfusion.21,22 In addition, controlling the intracuff pressure has been shown to reduce the incidence of sore throat.23
Even though there was no statistically significant difference in the occurrence of sore throat between the groups, patients with high NRS ratings for postoperative problems were mainly in the LTS II group. However, as most of these patients had also had their LTS II exchanged for an endotracheal tube it cannot be determined whether sore throat was induced by the LTS II or by endotracheal intubation. The duration of the surgery was shorter in the endotracheal tube group without reaching statistical significance. The duration of anaesthesia was significantly shorter in the endotracheal tube group. This difference may have been due to the time required to change the LTS II to an endotracheal tube for 15 patients.
Our study has some limitations: insertion attempts of the LTS II were limited to a maximum of two and, because the position of the surgical team limited access to the airway during surgery, an airway leak was not allowed at all. It could be postulated that the success rate of the LTS II would have been higher if repositioning it had been possible intraoperatively but this seems unlikely: in 12 of the 15 cases, replacement took place before surgery started. Due to the nature of the study, blinding of the anaesthetist was not possible, and blinding of the surgeon ceased if the patient had to be switched to an endotracheal tube after skin incision. The NRS rating of surgical conditions therefore might be biased in favour of the endotracheal tube. We excluded obese patients with BMI more than 30. These patients commonly require higher peak inspiratory pressure. Consequently, compared with our investigated patient population, we would expect an even greater failure rate of the LTS II due to airway leaks.
In summary, ventilation with the LTS II in patients undergoing laparoscopic radical prostatectomy in the Trendelenburg position resulted in a high complication rate, and we conclude that for this surgical procedure, endotracheal intubation appears to be superior to the LTS II. As a result of our experience, for elective surgery, we believe the range of indications for the LTS II remains to be elucidated. However, as the initial successful insertion rate was acceptable, the LTS II has a place in emergency situations.
Acknowledgements relating to this article
Assistance with this study: none.
Financial support a sponsorship: this project was supported with funding from The Department of Anaesthesiology and Intensive Care Medicine and The Department of Urology, both at the University of Leipzig Medical Faculty.
Conflicts of interest: none.
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* Alexander Dünnebier and Daniel Gardill contributed equally to this work.© 2017 European Society of Anaesthesiology