ProSeal versus the Classic laryngeal mask airway for positive pressure ventilation during laparoscopic cholecystectomy{dagger}

P. P. Lu1, J. Brimacombe*,2, C. Yang1 and M. Shyr1

1Department of Anesthesia, Chang Gung Memorial Hospital, 5 Fu-Hsin Street, Kuei-Shan Hsiang, 333 Taoyuan Hsien, Taiwan. 2University of Queensland and James Cook University, Department of Anaesthesia and Intensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia*Corresponding author

{dagger}Declaration of interest: Professor Brimacombe has intermittently received funds for research and lecturing overseas from Intavent Ltd, which manufactures both the devices used in this study. This study was not sponsored by Intavent Ltd.
{ddagger}LMA® is the property of Intavent Ltd.

Accepted for publication: January 17, 2002


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. We tested the hypothesis that the ProSeal laryngeal mask airway (PLMA) is a more effective ventilatory device than the Classic laryngeal mask airway (LMA{ddagger}) for laparoscopic cholecystectomy.

Methods. Eighty anaesthetized, paralysed patients (ASA 1–2, aged 18–80 yr) were randomly allocated for airway management with the PLMA or LMA. Ease of insertion and efficacy of seal were determined. Peak airway pressures were recorded immediately before and after carboperitoneum to 2.0 kPa. The inspired oxygen concentration and/or the ventilatory variable were adjusted according to a protocol to maintain SpO2 >=95% and E'CO2 <6.0 kPa. Oxygenation was considered suboptimal if SpO2 fell to 94–90% and failed if SpO2 was <90%. Ventilation was considered suboptimal if E'CO2 was >6.0–7.3 kPa and failed if E'CO2 was >7.3 kPa.

Results. First-time insertion success rates were higher for the LMA (40/40 vs 33/40; P=0.02). Seven patients required two attempts with the PLMA. Oropharyngeal leak pressure was higher for the PLMA [29 (SD 6) vs 19 (4) cm H2O; P<0.001]. There was a similar, significant increase in peak airway pressure after carboperitoneum for both devices (P<0.001). Before carboperitoneum, oxygenation and ventilation were optimal in all patients in both groups. After carboperitoneum, oxygenation was optimal in all patients in both groups, but ventilation was suboptimal more frequently with the LMA (8 vs 0; P=0.01). In three of these eight patients, ventilation failed but was subsequently optimal with the PLMA.

Conclusion. The PLMA is a more effective ventilatory device for laparoscopic cholecystectomy than the LMA. We do not recommend the use of the LMA for laparoscopic cholecystectomy.

Br J Anaesth 2002; 88: 824–7

Keywords: equipment, masks anaesthesia; surgery, laparoscopy; ventilation, positive end-expiratory pressure


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Laparoscopic cholecystectomy is one of the most commonly performed general surgical procedures.1 Tracheal intubation is recommended for airway management to facilitate ventilation and prevent aspiration,1 but three prospective studies24 and a retrospective survey5 have suggested that the Classic laryngeal mask airway (LMA{ddagger}) may be a suitable alternative. The ProSeal laryngeal mask airway (PLMA) is a new airway device that forms a more effective seal than the LMA and has a drainage tube that facilitates passage of a gastric tube. It probably provides protection against regurgitation, and prevents gastric insufflation when correctly placed.68 In this study, we tested the hypothesis that the PLMA is a more effective ventilatory device than the LMA for laparoscopic cholecystectomy.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
With institutional ethics committee approval and written, informed consent, 80 patients (ASA 1–2, aged 18–80 yr) undergoing elective laparoscopic cholecystectomy were randomly allocated (by opening a sealed envelope) for airway management with the PLMA or LMA. Patients were excluded if they had an interdental gap <2.5 cm, a body mass index >35 kg m2 or were at risk of aspiration (non-fasted, gastro-oesophageal reflux/disease).

A standard anaesthesia protocol was followed and routine monitoring applied. Anaesthesia was in the supine position with the patient’s head on a standard pillow 7 cm in height. Anaesthesia was induced with fentanyl 2 µg kg–1 and thiopental 5 mg kg–1. Maintenance was with 1–3% sevoflurane in 50% oxygen and air. Neuromuscular blockade was achieved with atracurium 0.5 mg kg–1 and maintained with 0.15 mg kg–1 boluses to maintain a train-of-four count of <1. The patient’s lungs were ventilated with a face mask until neuromuscular blockade was complete. Experienced LMA users (PLMA, >30 uses; LMA, >1000 uses) performed all the insertions and data were collected by independent observers. A size 4 PLMA or LMA was used for females and a size 5 PLMA or LMA was used for males. A clear, water-based gel was used for lubrication. The insertion technique for both devices was identical to the finger technique recommended for the LMA, and included neck flexion/head extension and full deflation of the cuff.9 A slight lateral approach was used if resistance was felt in the oropharynx. The introducer tool was not used with the PLMA because the operators had more experience with insertion using the finger technique. The PLMA or LMA was connected to a circle breathing system and the cuff inflated with air until an effective airway was established or the maximum recommended inflation volume reached (size 4, 30 ml; size 5, 40 ml). Fixation was by taping the tube over the chin. A rolled gauze swab was used as a bite block with the LMA. The number of insertion attempts to achieve effective ventilation was recorded. Effective ventilation was defined as a square-wave capnograph trace and normal thoracoabdominal movement. A failed insertion attempt was defined as removal of the device from the mouth. Three attempts were allowed before insertion was considered a failure.

Once an effective airway had been obtained, intracuff pressure was set at 60 cm H2O using a digital cuff pressure monitor, and the oropharyngeal leak pressure was determined by closing the expiratory valve of the circle system at a fixed gas flow of 3 litre min–1 and noting the airway pressure (maximum allowed was 40 cm H2O) at which equilibrium was reached.10 The location of gas leak at oropharyngeal leak pressure was determined as: (i) mouth: audible sound of gas escaping from the mouth heard by listening with the ear close to the mouth; (ii) stomach: audible sound of gas escaping into the oesophagus heard by listening over the epigastrium; and (iii) drainage tube: bubbling of lubricant placed on the proximal end of the drainage tube. For the PLMA group, insertion of a gastric tube (size 4, 14-FG; size 5, 16-FG) was attempted if there was no gas leak from the drainage tube during positive pressure ventilation. Any changes in peak airway pressure during gastric tube placement were noted. Correct placement was confirmed by injection of air and epigastric stethoscopy. The number of insertion attempts was recorded. Suction was applied to the gastric tube and the presence or absence of any gastric contents was recorded. The gastric tube was then removed. Gastric tube placement was not attempted with the LMA.

The patient’s lungs were initially ventilated with a tidal volume of 8 ml kg–1, a respiratory rate of 12 b.p.m. and an inspiratory:expiratory ratio of 1:2. Fresh gas flow was 1.5 litre min–1. Peak airway pressures were recorded immediately before and after carboperitoneum to 2 kPa in the supine position. The inspired oxygen concentration and/or the ventilatory variables were monitored continuously and adjusted according to a protocol to maintain SpO2 >=95% and E'CO2<6.0 kPa. If SpO2 fell below 97%, FIO2 was increased to 0.8, then to 1.0, and then the tidal volume was increased to 12 ml kg–1. If the E'CO2 increased above 5.6 kPa, the respiratory rate was first increased to 14 b.p.m., then 16 b.p.m., and then the tidal volume increased to 12 ml kg–1. A period of 3 min was allowed between adjustments. Oxygenation was considered suboptimal if SpO2 fell to 94–90% and failed if SpO2 <90%. Ventilation was considered suboptimal if E'CO2 >6.0–7.3 kPa or failed if E'CO2 >7.3 kPa. If oxygenation or ventilation failed during the procedure, the surgeon released the gas from the abdominal cavity, the patient was preoxygenated and the alternative device was inserted. If oxygenation or ventilation failed with the alternative device, the surgeon released the gas from the abdominal cavity, the patient was preoxygenated and the trachea intubated using a laryngoscope. Any episodes of gastric insufflation detected through the laparoscope by the surgeon were documented. The PLMA or LMA was removed at the end of surgery when the patient was able to open their mouth to command. Any blood detected on the device upon removal and the duration of anaesthesia were recorded. The oxygen saturation was recorded in the postanaesthesia care unit, 10–20 min after removal of the PLMA or LMA, the patient receiving oxygen at 4 litre min–1 via a Hudson-like face mask. Any adverse events (regurgitation, aspiration, bronchospasm, laryngospasm, coughing, retching, gagging, hiccup) were documented.

Sample size was based upon a projected difference of 20% between the groups for frequency of suboptimal ventilation, a type I error of 0.05 and a power of 0.9. Parametric data were analysed with unpaired and paired t-tests. Non-parametric data were analysed with the {chi}2 test. Data are mean (SD, range) or number of patients unless otherwise stated. Significance was taken as P<0.05.


    Results
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
The mean (SD, range) age, height and weight for the LMA and PLMA groups were similar [age, 49 (17, 18–80) and 52 (15, 18–76) yr respectively; height, 159 (6, 150–173) and 159 (7, 148–175) cm; weight, 59 (10, 43–82) and 62 (11, 43–90) kg]. The male:female ratios for the LMA and PLMA were similar (13:27 and 16:24 respectively). Duration of anaesthesia was similar for the LMA [91 (39) min] and PLMA [93 (46) min]. First-time insertion success rate was higher for the LMA (40/40 vs 33/40; P=0.02). Seven patients required two attempts with the PLMA. Oropharyngeal leak pressure was higher for the PLMA [29 (6) vs 19 (4) cm H2O; P<0.001]. For the PLMA, air leak at oropharyngeal leak pressure occurred into the mouth in 37 out of 40 patients, into the drainage tube in one out of 40, and was not detected in two out of 40. For the LMA, air leak at oropharyngeal leak pressure occurred into the mouth in 37 out of 40 and into the stomach in three out of 40.

Gastric tube placement was successful in all patients with the PLMA. There was no change in peak airway pressure during its placement. Fluid was detected in 31 out of 40 patients with the PLMA: 16 out of 40 had clear fluid, 14 out of 40 had bile-stained fluid and one out of 40 had semisolid fluid. Fluid detection was not attempted with the LMA.

There was a significant increase in peak airway pressure after carboperitoneum for both devices (Table 1). Before carboperitoneum, ventilation was optimal in all patients. After carboperitoneum, ventilation was suboptimal in eight patients with the LMA and none with the PLMA (P=0.01). Ventilation failed in three of these patients and was subsequently optimal with the PLMA (Table 1). No patient required tracheal intubation. There were no episodes of hypoxia, but gastric insufflation was identified in all three patients in whom use of the LMA was unsuccessful. In one patient (PLMA group), the laparoscopic procedure was converted to an open procedure because of surgical problems. Blood was detected more frequently with the PLMA at removal (6/40 vs 0/37; P=0.014). Postoperative oxygen saturation was similar [PLMA, 96.3 (1.9, 93–99)%; LMA, 96.9 (1.8, 92–100)%]. There were no other adverse events. Comparative data are summarized in Table 2.


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Table 1 Peak airway pressures [mean (SD)] and number of patients with optimal, suboptimal and failed ventilation before and after carboperitoneum for the Classic (LMA) and ProSeal (PLMA) laryngeal mask airways. *Reasons for suboptimal ventilation in all five patients were inadequate seal and hypoventilation with E'CO2 >6.0–7.3 kPa; {dagger}reasons for failed ventilation in all three patients were inadequate seal and hypoventilation with E'CO2 >7.3 kPa. ns=not significant
 

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Table 2 Summary of comparative data for the Classic (LMA) and ProSeal (PLMA) laryngeal mask airways. Data are mean (SD) or number of patients. ns=not significant
 

    Discussion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Our data show that the PLMA is a more effective ventilatory device than the LMA in patients undergoing laparoscopic cholecystectomy. As the peak airway pressures required for adequate ventilation during carboperitoneum are similar to mean oropharyngeal leak pressure for the LMA, it is not surprising that there is a high incidence of suboptimal and failed ventilation with the LMA. The PLMA forms a more effective seal, allowing higher peak airway pressures to be generated during carboperitoneum. Our findings contrast with those of Maltby and colleagues,2 Buniatian and Dolbneva3 and Ilzuka and colleagues,4 who all found that ventilation was adequate with the LMA during carboperitoneum. These interstudy differences may be related to the degree of suboptimal ventilation considered acceptable by the investigators, or to differences in the insufflation pressure or pulmonary compliance of the study population. Interestingly, Malby and colleagues2 found that oxygen saturation and E'CO2 were similar for the LMA and tracheal tube during carboperitoneum.

We found that 78% of patients in the PLMA group had some residual gastric fluid and that in almost half of these the fluid was bile-stained or contained semisolid material. Interestingly, none of these patients had symptoms of reflux and were therefore not considered at risk of aspiration during induction. Unfortunately, we did not measure residual gastric volume or pH. However, one of the authors (JB) has measured the volume and pH of fluid in 23 patients undergoing laparoscopic cholecystectomy with the PLMA, and found that the mean (range) volume was 18 (0–59) ml and pH 3.5 (2.5–5.8). Brain and colleagues6 found that the average residual gastric volume in patients undergoing routine minor procedures with the PLMA was 15 ml. The extent to which residual gastric fluid increases the risk of regurgitation and aspiration is unknown. We consider that residual gastric fluid should be removed by routine insertion of a gastric tube, but there is always the possibility that this might trigger regurgitation.11

The use of LMA for laparoscopic cholecystectomy is not conventional, but has been practised in some centres since the mid-1990s.5 However, there are insufficient data demonstrating that the technique is safe and effective, despite recent positive findings.24 12 There have also been two reports of aspiration in patients undergoing open cholecystectomy with the LMA.13 14 Sidaras and Hunter,15 in a recent editorial, comment on the dangers of extrapolating the risk and mortality of aspiration with the LMA from small numbers of subjects.

Our experience with the LMA was much greater than with the PLMA. There is both short-term16 and long-term17 skill acquisition with the LMA, and this probably applies to the PLMA. It is likely that first-time insertion failure rates and the frequency of trauma would be reduced with increasing experience. We suggest that the PLMA is only used for laparoscopic cholecystectomy by experienced LMA users who have a high success rate with the PLMA (say >95%) and substantial experience with the PLMA for other laparoscopic procedures, such as sterilization and inguinal hernia repair. The ventilatory capability and position of the PLMA should be assessed carefully after insertion. The patient should be intubated if the ventilatory capability is considered inadequate for carboperitoneum and/or the PLMA is malpositioned.

We conclude that the PLMA is a more effective ventilatory device for laparoscopic cholecystectomy than the LMA. We do not recommend the use of the LMA for laparoscopic cholecystectomy.


    References
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Cunningham AJ, Brull SJ. Laparoscopic cholecystectomy: anesthetic implications. Anesth Analg 1993; 76: 1120–33[Abstract]

2 Maltby JR, Beriault MT, Watson NC, Fick GH. Gastric distension and ventilation during laparoscopic cholecystectomy: LMA-Classic vs. tracheal intubation. Can J Anaesth 2000; 47: 622–6[Abstract/Free Full Text]

3 Buniatian AA, Dolbneva EL. [Laryngeal mask under total myoplegia and artificial pulmonary ventilation during laparoscopic cholecystectomies.] Vestn Ross Akad Med Nauk 1997; 9: 33–8[Medline]

4 IIzuka T, Kinoshita K, Fukui H. Pulmonary compliance of the laryngeal mask airway during laparoscopic cholecystectomy [abstract]. Anesth Analg 2000; 90: S210

5 Verghese C, Brimacombe J. Survey of laryngeal mask airway usage in 11910 patients: safety and efficacy for conventional and nonconventional usage. Anesth Analg 1996; 82: 129–33[Abstract]

6 Brain AIJ, Verghese C, Strube PJ. The LMA ‘ProSeal’—a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650–4[Abstract]

7 Brimacombe J, Keller C. The ProSeal laryngeal mask airway. A randomized, crossover study with the standard laryngeal mask airway in paralyzed, anesthetized patients. Anesthesiology 2000; 93: 104–9[ISI][Medline]

8 Keller C, Brimacombe J, Kleinsasser A, Loeckinger A. Does the ProSeal laryngeal mask airway prevent aspiration of regurgitated fluid? Anesth Analg 2000; 91: 1017–20[Abstract/Free Full Text]

9 Brimacombe JR, Brain AIJ, Berry AM. The Laryngeal Mask Instruction Manual for Anaesthesia. Henley-on-Thames: Intavent Research, 1999; 14–23

10 Keller C, Brimacombe J, Keller K, Morris R. A comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients. Br J Anaesth 1999; 82: 286–7[Abstract/Free Full Text]

11 Keller C, Brimacombe J, Rädler C, Puhringer F, Brimacombe N. The intubating laryngeal mask airway: effect of handle elevation on efficacy of seal, fibreoptic position, blind intubation and airway protection. Anaesth Intens Care 2000; 28: 414–9[ISI][Medline]

12 Georgiou L, Bousoula M, Spetsaki M. Combined thoracic epidural and general anaesthesia with laryngeal mask airway for laparoscopic cholecystectomy in a patient with myasthenia gravis. Anaesthesia 2000; 55: 821–2

13 Griffin RM, Hatcher IS. Aspiration pneumonia and the laryngeal mask airway. Anaesthesia 1990; 45: 1039–40[ISI][Medline]

14 Brain AIJ. The laryngeal mask and the oesophagus. Anaesthesia 1991; 46: 701–2

15 Sidaras G, Hunter JM. Is it safe to artificially ventilate a paralysed patient through the laryngeal mask? The jury is still out. [Editorial]. Br J Anaesth 2001; 86: 749–53[Free Full Text]

16 Lopez-Gil M, Brimacombe J, Cebrian J, Arranz J. Laryngeal mask airway in pediatric practice—a prospective study of skill acquisition by anesthesia residents. Anesthesiology 1996; 84: 807–11[ISI][Medline]

17 Brimacombe J. Analysis of 1500 laryngeal mask uses by one anaesthetist in adults undergoing routine anaesthesia. Anaesthesia 1996; 51: 76–80[ISI][Medline]