Is it safe to artificially ventilate a paralysed patient through the laryngeal mask? The jury is still out

Laryngeal mask combined with bronchial tube achieves one-lung ventilation for transthoracic oesophagectomy

Laryngeal mask combined with bronchial blocker provides an alternative for lung isolation but lacks adequate access to the non-dependent lung. Substituting the blocker with a bronchial tube may overcome this limitation. In this report, a #4.5 cuffed bronchial tube was introduced into the non-dependent lung through a second-generation laryngeal mask for transthoracic oesophagectomy. During the 2.5-hour thoracotomy, one-lung ventilation was achieved by isolating the left lung with the bronchial tube and ventilating the right lung via the laryngeal mask, using volume-control mode (7 mL/kg × 12/min) with P_IP21-23 cm H₂O, pH 7.36 and PaCO₂ 38.3. Prior to thoracotomy closure, suction and reinflation of the left lung were performed through the bronchial tube. Bronchoscopy via the laryngeal mask revealed no injury to the airway after removal of the bronchial tube. The case shows that laryngeal mask combined with bronchial intubation provides one-lung ventilation with access to the isolated lung.

The Stony Brook awake craniotomy protocol: A technical note

Most current awake craniotomy techniques utilize unnecessarily complicated airway management, and cause discomfort to the patients during the awake phase of the surgery. Our manuscript is written to discuss the neurosurgical and anesthetic techniques that we have developed to optimize awake craniotomy techniques at Stony Brook University Medical Center. We used the frameless Brainlab™ skull-mounted array for stereotactic navigation. Rigid fixation of the skull was avoided. General anesthesia with established airway was used during the "asleep" phase of the surgery. Following the removal of the bone flap and the opening of the dura, the patients were woken up, and the established airway was removed. Cortical mapping was performed to establish a safe entry zone for tumor removal. While the tumors were being removed, we continued motor examination and casual conversation with the patients to ensure safety. Patients were sedated during the remaining phase of the surgery until skin closure. No patient exhibited any neurological deficits or adverse anesthesia outcomes during the postoperative period. The protocol we developed avoids rigid skull fixation and emphasizes flexible intraoperative planning, thereby maximizing patient and physician comfort while allowing for successful tumor resection.

Extraglottic airway devices: technology update

Extraglottic airway devices (EADs) have revolutionized the field of airway management. The invention of the laryngeal mask airway was a game changer, and since then, there have been several innovations to improve the EADs in design, functionality, safety and construction material. These have ranged from changes in the shape of the mask, number of cuffs and material used, like rubber, polyvinylchloride and latex. Phthalates, which were added to the construction material in order to increase device flexibility, were later omitted when this chemical was found to have serious adverse reproductive outcomes. The various designs brought out by numerous companies manufacturing EADs resulted in the addition of several devices to the airway market. These airway devices were put to use, many of them with inadequate or no evidence base regarding their efficacy and safety. To reduce the possibility of compromising the safety of the patient, the Difficult Airway Society (DAS) formed the Airway Device Evaluation Project Team (ADEPT) to strengthen the evidence base for airway equipment and vet the new extraglottic devices. A preuse careful analysis of the design and structure may help in better understanding of the functionality of a particular device. In the meantime, the search for the ideal EAD continues.

Adducted vocal cords relieved by neuromuscular blocking drug: a cause of impaired mechanical ventilation when using a laryngeal mask airway: two photographically documented cases

Two cases of vocal cord closure, which was responsible for acute intraoperative impairment of mechanical ventilation in two patients with entropy-controlled depth of anesthesia, are reported. Administration of low-dose neuromuscular blocking drug was associated with immediate vocal cord relaxation and restoration of efficient mechanical ventilation.

[Clinical use of the ProSeal™ laryngeal mask in infants, children and adolescents : prospective observational survey]

BACKGROUND

In contrast to the adult population scientific data on ProSeal™-LMA (PLMA) usage in infants, children, and adolescents are rather limited. Most data have been generated by expert users in studies on small numbers of patients. The aim of this study was to gather comprehensive data about the characteristics, efficacy and safety of its routine use in children at a teaching institution.

METHODS

Using a standardized reporting form the following data were collected in the course of a prospective survey on PLMA usage in patients aged up to 18 years: user characteristics, patient characteristics, type and duration of operation, details of airway management and anesthetic technique, details of PLMA usage-related critical incidents and postoperative status of the patient.

RESULTS

Use of the PLMA was documented in 512 patients by 61 anesthesiologists (32% staff grade, 68% trainees). The average age, height and weight of the patients was 8 years (range 0-17 years), 130 cm (range 54-193 cm) and 29 kgBW (range 5-130 kgBW), respectively. Anesthesia was induced intravenously in 458 patients (89.5%) and by inhalation in 54 patients. Maintenance of anesthesia was by total intravenous anesthesia (propofol) in 184 patients (36.5%) and by an inhalational agent (sevoflurane or desflurane) in 320 patients (63.7%). Neuromuscular blocking agents were used in 7 patients (1.4%). The patients were anesthetized for an average of 80 min (range 15-270 min) and insertion success rate was 99% with a maximum of 3 attempts. The average initial airway leak pressure was 27cm H(2)O (range 12-40 cm H(2)O); however, lower pressures were recorded for smaller size masks (size 1.5-2.5) without a dorsal cuff than for larger size masks (size 3-5; p<0.01). Ventilation was controlled in 96% and combined with PEEP in 39% of cases. Critical incidents associated with PLMA were documented in a total of 8.4% of cases, the majority being minor trauma, evidenced by blood on the PLMA on removal, followed by some form of airway obstruction. In 3.3% of cases these incidents were judged as clinically relevant of which 0.6% were classified as serious. Twice as many problems occurred during induction of anesthesia as in the maintenance phase and emergence phase of anesthesia (p=0.037). In 1.6% the PLMA was abandoned in favor of the endotracheal tube. In 7 patients the PLMA was exchanged in the induction room whereas in 1 patient this took place intraoperatively. Failure of ProSeal™ laryngeal mask use correlated with the level of PLMA use experience with 75% of failures caused by users with an experience of less than 50 uses and no failure in users with an experience of more than 100 uses. Failure did not correlate with the size of the mask. In 2 cases the PLMA was successfully used after failed endotracheal intubation. In 6 patients drainage of regurgitated gastric fluid through the drain tube was documented. No long-term adverse sequelae resulted in any patient.

CONCLUSION

This survey demonstrates that the PLMA can be used effectively in infants, children and adolescents in the routine university clinical practice setting. However, this study does not confirm the extremely high success and low complication rates reported in controlled studies. The results support the assumption that with the PLMA regurgitated gastric fluid can be drained away from the larynx through the drain tube.

Use of ProSeal laryngeal mask airway in 2114 adult patients: a prospective study

BACKGROUND

There have been numerous studies published on the ProSeal laryngeal mask airway (PLMA). However, few have investigated its utility in a large practice setting. We sought to gather comprehensive data about the characteristics, efficacy, and safety of its use by a representative group of anesthesiologists working at a teaching center.

METHODS

Information was collected on a standardized data collection form. Clinical information obtained included user characteristics, patient characteristics, type and duration of operation, details of airway management and anesthetic technique, details of adverse events, and postoperative status of the patient.

RESULTS

Use of the PLMA was documented in 2114 patients by 81 anesthesiologists (57% trainee, 43% staff grade). The insertion success rate was 99% within a maximum of 3 attempts. Mean airway leak pressure was 28 (11-40) cm H(2)O. In 3.2% of cases, the PLMA was abandoned in favor of the endotracheal tube. Ventilation was controlled in 98%. Clinically "relevant" adverse events were recorded in 3.3% of all cases, of which 0.6% were classified as "serious." No long-term adverse sequelae resulted. No signs of aspiration were found in 12 patients with apparent regurgitation of gastric fluid through the drain tube of the PLMA. Five cases of difficult ventilation and 16 cases of difficult endotracheal intubation were successfully managed by the use of the PLMA.

CONCLUSION

This study demonstrates that airway management using the PLMA is safe and effective in a general practice setting. The results support the assumption that a correctly positioned PLMA can protect from pulmonary aspiration of regurgitate gastric fluid. The data also support use of the PLMA for the management of the difficult airway.

Pressure-controlled ventilation is superior to volume-controlled ventilation with a laryngeal mask airway in children

BACKGROUND

This prospective, randomized, crossover study had two purposes: first, to determine whether pressure-controlled ventilation (PCV) is safer than volume-controlled ventilation (VCV) by preventing gastric insufflation in children ventilated through an laryngeal mask airway (LMA); second, to assess whether the measurement of LMA leak pressure (P(leak)) is useful for preventing leakage during positive pressure ventilation (PPV).

METHODS

Forty-one, 2 to 15-year-old children underwent general anesthesia with an LMA. The expiratory valve was set at 30 cmH(2)O and P(leak) was measured using constant gas flow. Children were randomly ventilated using PCV or VCV for 5 min in order to reach a P(ET)CO(2) not exceeding 45 mm Hg, and then they were ventilated with the alternative mode. If the target P(ET)CO(2) could not be obtained in one mode, we switched to the other. If both modes failed, children were intubated. Tidal volumes, P(ET)CO(2) and airway pressures were noted and compared between modes. Gastric insufflation was checked by epigastric auscultation.

RESULTS

PCV provided more efficient ventilation than VCV, as targeted P(ET)CO(2) was obtained without gastric insufflation using PCV in all cases except one, whereas VCV failed in three cases. No gastric insufflation occurred when ventilating below peak.

CONCLUSIONS

These findings suggest that in the age group studied, PCV is more efficient than VCV for controlled ventilation with a laryngeal mask. Gastric insufflation did not occur with this mode.

Recent developments in airway management of the paediatric patient

PURPOSE OF THE REVIEW

During the last two years, several studies have enhanced our knowledge about the influence of pharmacological agents and routine airway management manoeuvres on the airway of paediatric patients. New supraglottic airway devices have been introduced into routine paediatric anaesthesia practice, and the design of paediatric endotracheal tubes has been modified. This review summarizes the most recent and relevant scientific developments in paediatric airway management.

RECENT FINDINGS

Strong evidence has been gained that the lateral position is the best to ensure a clear airway in anaesthetized or sedated spontaneously breathing children. Remifentanil has emerged as an appealing drug for airway management in anaesthetized or sedated children. The paediatric ProSeal-Laryngeal mask airway offers important advantages over the Classic-Laryngeal mask airway for supraglottic airway management. The newly designed Microcuff paediatric endotracheal tube offers an improved age-appropriate design.

SUMMARY

Remifentanil has found a place in airway management in paediatric patients. Recent improvements in the design of paediatric supraglottic airway devices and endotracheal tubes are promising. Further research is needed to consolidate their role in improving the perioperative outcome in paediatric patients.

Einsatz der ProSeal®-Kehlkopfmaske der Größe 3 bei Kindern

BACKGROUND

The low-pressure airway seal of the Classic laryngeal mask airway (CLMA) can be inadequate for positive pressure ventilation (PPV) in children. The ProSeal laryngeal mask airway (PLMA) forms a more effective seal of the airway than the CLMA and facilitates gastric tube placement in adults. The size 3 PLMA can be used in adults and children.

METHODS

The CLMA and PLMA were studied in random order -- crossover -- in 30 anaesthetized, non-paralysed children (average age 10.6 years, average body weight 39 kg). Airway leak pressure, maximum tidal volume, ease of insertion, quality of initial airway and fiberoptic position were determined. Gastric tube placement was assessed for the PLMA.

RESULTS

The mean airway leak pressure in neutral head position (27.0 vs. 16.8 cm H(2)O), maximum flexion (38.3 vs. 26.2 cm H(2)O) and maximum extension (21.1 vs. 14.2 cm H(2)O) as well as the mean maximum tidal volume (1432 vs. 1062 ml) were significantly higher (p<0.001) for the PLMA. Air insufflation into the stomach occurred with the CLMA but not with the PLMA. Gastric tube placement was possible in all patients.

CONCLUSIONS

The high reliability of g-tube placement and the significantly increased airway leak pressure seem to make the size 3 PLMA a more suitable device for PPV in children than the same size CLMA.

The Size 1½ ProSeal™ Laryngeal Mask Airway in Infants: A Randomized, Crossover Investigation with the Classic™ Laryngeal Mask Airway

Many problems with the Classic laryngeal mask airway (CLMA) in infants are believed to be related to its inadequate cuff design. One of the main limitations of the CLMA is that the resulting low-pressure seal can be inadequate for positive pressure ventilation (PPV). The ProSeal LMA (PLMA), a new laryngeal mask airway with a modified cuff, has been shown to form a more effective seal than the CLMA in children. The first infant size PLMA, size 1(1/2), became available recently. We studied 30 anesthetized, nonparalyzed infants aged 15 mo (2-30 mo) and weighing 9 kg (5-12 kg). The CLMA and PLMA were inserted in random order into each patient. Airway leak pressure and maximum tidal volume were measured. Ease of insertion, quality of initial airway, and fiberoptic position were also determined. Gastric tube placement was assessed for the PLMA. The mean airway leak pressure in neutral head position (26.7 versus 18.9 cm H2O), maximum flexion (35.6 versus 28.2 cm H2O), and the mean maximum tidal volume (312 versus 260 mL) were significantly higher for the PLMA (P < 0.01). Air entered the stomach in eight patients with the CLMA but did not with the PLMA. Gastric tube placement was possible in all but one patient. In three patients, the use of the PLMA led to some degree of clinically relevant compression of the larynx. The size 1(1/2) PLMA seems to be a more suitable device for airway maintenance in infants than the same size CLMA. The ability to insert a gastric tube at the same time, and a significantly higher airway leak pressure than with the CLMA, may have important implications for its use for PPV in infants.

Comparison of cuffed, uncuffed tracheal tubes and laryngeal mask airways in low flow pressure controlled ventilation in children

BACKGROUND

The use of low flow circle systems necessitates a 'leak free' breathing system which is commonly achieved by using a cuffed tracheal tube (TT). We hypothesized that low flow circle system anesthesia can equally effectively be achieved by using the LMA in pediatric anesthesia.

METHODS

Following local ethics committee approval we randomly recruited 45 patients scheduled for elective surgery and requiring mechanical ventilation into three groups (cuffed TT, uncuffed TT and LMA group, n = 15). The size of the TT was determined by means of the formula (age/4) + 4.5 for uncuffed and (age/4) + 4 for cuffed TT whereas the size of the LMA size was dependent on weight. Following induction of anesthesia and muscle paralysis patients were ventilated with pressure controlled ventilation through a pediatric circle system and the lowest fresh gas flow (FGF) determined.

RESULTS

The FGF achieved were (median and range) 0.20 (0.2-0.25) l.min(-1) for the LMA group, 0.20 (0.2-0.4) l.min(-1) for the cuffed TT group and 1.15 (0.2-4.75) l.min(-1) for the uncuffed group. The differences between the LMA and cuffed TT compared with the uncuffed TT were significant (P < 0.0001 and P = 0.0002, respectively). The difference in FGF between LMA and cuffed TT was not significant.

CONCLUSION

We conclude that pressure controlled ventilation using an LMA is an alternative to a cuffed TT during low flow circle system anesthesia in children. Low FGF is unlikely to be achieved consistently using an uncuffed TT because of a substantial leak.

The proseal™laryngeal mask airway: a review of the literature

PURPOSE

To analyze and summarize the published literature relating to the ProSeal LMA (PLMA): a modification of the "classic LMA" (cLMA) with an esophageal drain tube (DT), designed to improve controlled ventilation, airway protection and diagnosis of misplacement.

SOURCE

Articles identified through Medline and EMBASE searches using keywords "Proseal", "ProSeal" and "PLMA". Hand searches of these articles and major anesthetic journals from January 1998 to March 2005.

PRINCIPAL FINDINGS

Searches identified 59 randomized controlled trials or clinical studies and 79 other publications. Compared to the cLMA, PLMA insertion takes a few seconds longer. First attempt insertion success for the PLMA is lower, but overall success is equivalent. Airway seal is improved by 50%. The DT enables early diagnosis of mask misplacement, allows gastric drainage, reduces gastric inflation and may vent regurgitated stomach contents. Evidence suggests, but does not prove, that the correctly placed PLMA reduces aspiration risk compared with the cLMA. PLMA use is associated with less coughing and less hemodynamic disturbance than use of a tracheal tube (TT). Comparative trials of the PLMA with other supraglottic airways favour the PLMA. Clinicians have extended the use of the PLMA inside and outside the operating theatre including use for difficult airway management and airway rescue.

CONCLUSIONS

The PLMA has similar insertion characteristics and complications to other laryngeal masks. The DT enables rapid diagnosis of misplacement. The PLMA offers significant benefits over both the cLMA and TT in some clinical circumstances. These and clinical experience with the PLMA are discussed.

An evaluation of the Cobra Perilaryngeal Airway?: study halted after two cases of pulmonary aspiration

The Cobra Perilaryngeal Airway (Engineered Medical Systems, Indianapolis, IN) is a new supraglottic airway designed for spontaneous and controlled ventilation. It is not yet commercially available in the UK. Our aim was to evaluate the performance of the Cobra Perilaryngeal Airway in a cohort study and in a randomised, controlled, crossover comparison study with the Classic Laryngeal Mask Airway. After studying 29 patients, both studies were suspended and later stopped after two cases of significant pulmonary aspiration had occurred in patients whilst using the Cobra Perilaryngeal Airway. These cases raised concern about both the design and the safety of the Cobra Perilaryngeal Airway, particularly during controlled ventilation. We suggest that the Cobra Perilaryngeal Airway should not be marketed for controlled ventilation until more safety data are available.

Strategies for airway management

Airway management is a critical part of anaesthesia practice. Management includes mask ventilation, laryngoscopy, endotracheal intubation and extubation of the patient. Difficulty can be encountered at any of these stages, potentially resulting in significant complications. Thorough preoperative assessment, as well as careful planning and preparation, can reduce the potential for complications. The American Association of Anesthesiologists (ASA) developed and recently revised guidelines for the management of the difficult airway. These guidelines focus on strategies for intubation as well as alternative airway techniques that can be used when a patient with a difficult airway is encountered.

A new supraglottic airway, the Elisha Airway Device: a preliminary study

We describe the Elisha Airway Device (EAD), a new reusable supraglottic ventilatory device. Its uniqueness consists of its ability to combine three functions in a single device: ventilation, blind and/or fiberoptic-aided intubation without interruption of ventilation, and gastric tube insertion. This study was performed in 70 ASA status I-II, Mallampati class I-II patients undergoing elective knee arthroscopy and receiving general anesthesia with mechanical ventilation. Anesthesia was induced with fentanyl and propofol and was maintained with isoflurane in N20/oxygen. Neuromuscular blockade was achieved with vecuronium. Blind insertion of the device was successful in 96% of patients, with a mean insertion time of 20 +/- 4 s. In these patients it was possible to maintain oxygenation and ventilation throughout the surgical procedure. Gastric tube insertion was successful in all cases. Endotracheal intubation via the EAD was attempted in 20 patients. Blind intubation was possible during the first and second attempts in 15 and 2 patients, respectively. Fiberoptic intubation was then successful in two of the remaining three patients. The EAD is a new alternative in the evolution of supraglottic ventilatory devices; however, further clinical studies are necessary to evaluate its efficacy.

[Lesions to lips, oral and nasal cavities, pharynx, larynx, trachea and esophagus due to endotracheal intubation and its alternatives]

Dysphagia of greater than 48 h duration is an indication for indirect laryngoscopy and when odynophagia and otalgia occur simultaneously, the possibility of subluxation of the arytenoids demands an urgent ENT assessment. The potential seriousness of laryngeal lesions following intubation obliges us to use the smallest compatible endotracheal tube. The occurrence of pain cervical surgical emphysema and fever suggests a pharyngeal lesion necessitating the suspension of oral feeding and the initiation of antibiotic therapy with anaerobic activity, while awaiting possible surgical intervention. There is no argument to use a tooth-guard for each intubation, but tooth fragility must be researched. The incidence of nasal fossa trauma is reduced with the use of nasal packs impregnated with local anaesthetic containing a vasoconstrictor. This allows the introduction of a small flexible lubricated tube. Laryngeal mask-induced sore throat is more common than the more serious injuries. The classical technique of introducing a laryngeal mask of appropriate size (4 for women, 5 for men) in which the cuff is inflated to a leak pressure of 20 cm H(2)O reduces this frequency. The facial mask may cause injuries especially with prolonged use. The incidence of pulmonary aspiration, linked to the action of drugs, raised intra-abdominal pressure; an emergent situation or difficult intubation is decreased with the performance of the Sellick maneuver at intubation, rapid induction and the neutralization of gastric acidity. A meticulous technique of insertion of the, individualized anaesthesia, particular vigilance at the time of decurarisation and position changes and a calm awakening assure its optimal use, unless the Proseal laryngeal mask modifies this point of view.

Storage capacities of the laryngeal mask and laryngeal tube compared and their relevance to aspiration risk during positive pressure ventilation

IMPLICATIONS

Supraglottic airways used for positive pressure ventilation run the occasional risk of regurgitated liquid entering the lungs (aspiration). A dynamic model described here shows that the laryngeal tube has a larger liquid storage capacity between the two cuffs than the bowl of the laryngeal mask, with a consequent smaller aspiration risk.

Anaesthesia for awake craniotomy--evolution of a technique that facilitates awake neurological testing

BACKGROUND

There is an increasing trend towards performing craniotomy awake. The challenge for the anaesthetist is to provide adequate analgesia and sedation, haemodynamic stability, and a safe airway, with an awake, cooperative patient for neurological testing.

METHODS

The records of all patients who had awake craniotomy at our institution were reviewed. Patients were divided into three groups according to anaesthetic technique. Patients in Group 1 were sedated throughout the procedure. Patients in Groups 2 and 3 had an asleep-awake-asleep technique. Those in Group 2 were anaesthetized with a propofol infusion and fentanyl, and breathed spontaneously through a laryngeal mask airway (LMA). Patients in Group 3 had total i.v. anaesthesia with propofol and remifentanil, and ventilation was controlled using an LMA. We noted the incidence of complications in each group.

RESULTS

There were 99 procedures carried out between 1989 and 2002. Group 3 had the fewest complications. No patients in Group 3 developed hypercapnia (E'(CO(2)) >6 kPa), compared with all of the patients in Group 2. Patients in Group 1 had no E'(CO(2)) monitoring, but 7% developed airway obstruction. No patients in Group 3 required additional analgesia for pain, compared with 70% of patients in Group 2.

CONCLUSIONS

We have developed a technique for craniotomy, which facilitates awake neurological testing, is safe, and has good patient satisfaction.

Laboratory and clinical comparisons of the Streamlined Liner of the Pharynx Airway (SLIPA) with the laryngeal mask airway

The Streamlined Liner of the Pharynx Airway (SLIPA) is a new inexpensive disposable supraglottic airway designed to seal without the use of an inflatable cuff. It comprises a hollow blow-moulded soft plastic airway shaped to form a seal in the pharynx. Being hollow, liquid entrapment is possible and this may provide effective protection against aspiration. A model silicone rubber pharynx with an 'oesophageal' tube for injecting volumes of regurgitant liquid was designed to evaluate the SLIPA and the standard and ProSeal laryngeal mask airways during positive-pressure ventilation. A linear relationship between the volume 'regurgitated' and the volume 'aspirated' was found with the laryngeal mask airway and the ProSeal laryngeal mask airway with the drainage tube clamped. Both the ProSeal laryngeal mask airway with an open drainage tube and the SLIPA, but not the standard laryngeal mask airway, provided effective protection against 'aspiration' during positive-pressure ventilation using the model. In a clinical study, 120 patients were randomly allocated to receive controlled ventilation of the lungs via the standard laryngeal mask airway or the SLIPA. Both devices were equally easy to insert and satisfactory for airway management.

The ProSeal laryngeal mask in myasthenia gravis

This case describes the anaesthesia management of a patient with myasthenia gravis who required mastectomy with axillary lymph node clearance. After withholding medical therapy for the myasthenia preoperatively on the day of surgery, anaesthesia was maintained with halothane, nitrous oxide and a remifentanil infusion. Muscle relaxants were avoided, facilitated by the use of a ProSeal (Intravent, Orthofix, Maidenhead, United Kingdom) laryngeal mask airway for positive pressure ventilation. The ProSeal laryngeal mask airway is a new laryngeal mask device with a modified cuff and a drainage tube which has been shown to have advantages over older designs for use during positive pressure ventilation. The rationale for the management of this patient with myasthenia is discussed.

The LMA-ProSeal is an effective alternative to tracheal intubation for laparoscopic cholecystectomy

PURPOSE

To compare LMA-ProSeal (LMA-PS) with endotracheal tube (ETT) with respect to pulmonary ventilation and gastric distension during laparoscopic cholecystectomy.

METHODS

We randomized 109 ASA I-III adults to LMA-PS or ETT after stratifying them as non-obese or obese (body mass index > 30 kg x m-2). After preoxygenation, anesthesia was induced with propofol, fentanyl and rocuronium. An LMA-PS (women #4, men #5) or ETT (women 7 mm, men 8 mm) was inserted and the cuff inflated. A #14 gastric tube was passed into the stomach in every patient and connected to continuous suction. Anesthesia was maintained with nitrous oxide, oxygen and isoflurane. Ventilation was set at 10 mL x kg-1 and 10 breaths x min-1. The surgeon, blinded to the airway device, scored stomach size on an ordinal scale of 0-10 at insertion of the laparoscope and upon decompression of the pneumoperitoneum.

RESULTS

There were no statistically significant differences in SpO2 or P(ET)CO2 between the two groups before or during peritoneal insufflation in either non-obese or obese patients. Median (range) airway pressure at which oropharyngeal leak occurred during a leak test with LMA-PS was 34 (18-45) cm water. Change in gastric distension during surgery was similar in both groups. Four of 16 obese LMA-PS patients crossed over to ETT because of respiratory obstruction or airway leak.

CONCLUSIONS

A correctly seated LMA-PS or ETT provided equally effective pulmonary ventilation without clinically significant gastric distension in all non-obese patients. Further studies are required to determine the acceptability of the LMA-PS for laparoscopic cholecystectomy in obese patients.

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

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) for laparoscopic cholecystectomy.

METHODS

Eighty anaesthetized, paralyzed 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 > or = 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.

Aspiration prevented by the ProSeal laryngeal mask airway: a case report

PURPOSE

To describe a case of intraoperative passive regurgitation where the ProSeal laryngeal mask airway (PLMA) successfully protected the airway from the respiratory tract.

CLINICAL FEATURES

A 32-yr-old man was electively scheduled for change of dressings and application of plaster of Paris to both legs. A size 5 PLMA was inserted on the first attempt and the patient allowed to breathe spontaneously. Twenty-five minutes into the procedure brown fluid was noticed in the drainage tube of the mask. There was no change in respiratory pattern nor any evidence of coughing retching or vomiting. Twenty-five millilitres of fluid were suctioned out of the tube which tested positive for acid. The PLMA was left in place and the procedure continued uneventfully. After removal of the mask pH testing showed the dorsum of the mask to have a pH of 7 and the ventrum/bowl of the mask to be dry with a pH of 7. The patient had no respiratory symptoms in the recovery room and the postoperative course was uneventful.

CONCLUSIONS

This case illustrates that passive regurgitation can occur unexpectedly intraoperatively and shows that the PLMA can protect the airway during such an event by allowing the regurgitated fluid to pass up the drainage tube without leaking into the glottis.