C. Keller

The Laryngeal Mask Airway SupremeTM – a single use laryngeal mask airway with an oesophageal vent. A randomised, cross-over study with the Laryngeal Mask Airway ProSealTM in paralysed, anaesthetised patients

The LMA SupremeTM is a new extraglottic airway device which brings together features of the LMA ProSealTM, FastrachTM and UniqueTM. We test the hypothesis that ease of insertion, oropharyngeal leak pressure, fibreoptic position and ease of gastric tube placement differ between the LMA ProSealTM and the LMA SupremeTM in paralysed anesthetised patients. Ninety‐three females aged 19–71 years were studied. Both devices were inserted into each patient in random order. Two attempts were allowed. Digital insertion was used for the first attempt and guided insertion for the second attempt. Oropharyngeal leak pressure and fibreoptic position were determined during cuff inflation from 0 to 40 ml in 10 ml increments. Gastric tube insertion was attempted if there was no gas leak from the drain tube. First attempt and overall insertion success were similar (LMA ProSealTM, 92% and 100%; LMA SupremeTM 95% and 100%). Guided insertion was always successful following failed digital insertion. Oropharyngeal leak pressure was 4–8 ml higher for the LMA ProSealTM over the inflation range (p < 0.001). Intracuff pressure was 16–35 cm higher for the LMA ProSealTM when the cuff volume was 20–40 ml (p < 0.001). There was an increase in oropharyngeal leak pressure with increasing cuff volume from 10 to 30 ml for both devices, but no change from 0 to 10 ml and 30–40 ml. There were no differences in the fibreoptic position of the airway or drain tube. The first attempt and overall insertion success for the gastric tube was similar (LMA ProSealTM 91% and 100%; LMA SupremeTM 92% and 100%). We conclude that ease of insertion, gastric tube placement and fibreoptic position are similar for the LMA ProSealTM and LMA SupremeTM in paralysed, anaesthetised females, but oropharyngeal leak pressure and intracuff pressure are higher for the LMA ProSealTM.

Reversing sevoflurane-associated Q-Tc prolongation by changing to propofol.

Congenital or acquired forms of the long Q–T syndrome may result in ventricular tachycardia known as torsade de pointes. Many drugs including volatile anaesthetics modify the Q–T interval. Sevoflurane is known to prolong of the rate‐corrected Q–T interval (Q–Tc). The objective of this study was to determine whether the sevoflurane‐associated Q–Tc prolongation is rapidly reversible when propofol is substituted for sevoflurane. Thirty‐two female patients were allocated to two groups. All patients received sevoflurane induction and anaesthesia for 15 min. In one group, sevoflurane was then discontinued and anaesthesia maintained on propofol for another 15 min. The second group received sevoflurane anaesthesia for 30 min. Measurements were taken before, and 15, 20, 25 and 30 min after induction. Q–Tc prolongation was significantly reduced 5, 10 and 15 min after propofol had been substituted for sevoflurane. We conclude that the sevoflurane‐associated Q–Tc prolongation is fully reversible within 15 min when propofol is substituted for sevoflurane.

Pressure support ventilation versus continuous positive airway pressure ventilation with the ProSeal laryngeal mask airway: A randomized crossover study of anesthetized pediatric patients

Continuous positive airway pressure (CPAP) and pressure support ventilation (PSV) improve gas exchange in adults, but there are little published data regarding children. We compared the efficacy of PSV with CPAP in anesthetized children managed with the ProSeal™ laryngeal mask airway. Patients were randomized into two equal-sized crossover groups and data were collected before surgery. In Group 1, patients underwent CPAP, PSV, and CPAP in sequence. In Group 2, patients underwent PSV, CPAP, and PSV in sequence. PSV comprised positive end-expiratory pressure set at 3 cm H2O and inspiratory pressure support set at 10 cm H2O above positive end-expiratory pressure. CPAP was set at 3 cm H2O. Each ventilatory mode was maintained for 5 min. The following data were recorded at each ventilatory mode: ETco2, Spo2, expired tidal volume, peak airway pressure, work of breathing patient (WOB), &dgr; esophageal pressure, pressure time product, respiratory drive, inspiratory time fraction, respiratory rate, noninvasive mean arterial blood pressure, and heart rate. In Group 1, measurements for CPAP were similar before and after PSV. In Group 2, measurements for PSV were similar before and after CPAP. When compared with CPAP, PSV had lower ETco2 (46 ± 6 versus 52 ± 7 mm Hg; P < 0.001), slower respiratory rate (24 ± 6 versus 30 ± 6 min−1; P < 0.001), lower WOB (0.54 ± 0.54 versus 0.95 ± 0.72 JL−1; P < 0.05), lower pressure time product (94 ± 88 versus 150 ± 90 cm H2O s−1min−1; P < 0.001), lower &dgr; esophageal pressure (10.6 ± 7.4 versus 14.1 ± 8.9 cm H2O; P < 0.05), lower inspiratory time fraction (29% ± 3% versus 34% ± 5%; P < 0.001), and higher expired tidal volume (179 ± 50 versus 129 ± 44 mL; P < 0.001). There were no differences in Spo2, respiratory drive, mean arterial blood pressure, and heart rate. We conclude that PSV improves gas exchange and reduces WOB during ProSeal™ laryngeal mask airway anesthesia compared with CPAP in ASA physical status I children aged 1–7 yr.

A study of airway management using the ProSeal LMA laryngeal mask airway compared with the tracheal tube on postoperative analgesia requirements following gynaecological laparoscopic surgery.

In a randomised double blind prospective study, we tested the hypothesis that postoperative pain is lower in patients who receive an ProSeal LMA™ laryngeal mask airway compared with a tracheal tube. One hundred consecutive female patients (ASA I–II, 18–75 years) undergoing laparoscopic gynaecological surgery were divided into two equal‐sized groups for airway management with the ProSeal LMA or tracheal tube. Anaesthesia management was identical for both groups and included induction of anaesthesia using propofol/fentanyl, and maintenance with propofol/remifentanil, muscle relaxation with rocuronium, positive pressure ventilation, gastric tube insertion, dexamethasone/tropisetron for anti‐emetic prophylaxis, and diclofenac for pain prophylaxis. All types of postoperative pain were treated using intravenous patient‐controlled analgesia (PCA) morphine. Patients and postoperative staff were unaware of the airway device used. Data were collected by a single blinded observer. We found that pain scores were lower for the ProSeal LMA at 2 h and 6 h but not at 24 h. Morphine requirements were lower for the ProSeal LMA by 30.4%, 30.6% and 23.3% at 2, 6 and 24 h, respectively. Nausea was less common with the ProSeal LMA than with the tracheal tube at 2 h and 6 h but not at 24 h. There were no differences in the frequency of vomiting, sore throat, dysphonia or dysphagia. We conclude that postoperative pain is lower for the ProSeal LMA than the tracheal tube in females undergoing gynaecological laparoscopic surgery.

Fatal errors in nitrous oxide delivery

Nitrous oxide continues to be used frequently and the possibility of inadvertent fatal hypoxaemia resulting from technical errors with its administration still exists. A Medline analysis revealed only a few case reports over the last 30 years, and a closed claim analysis only reported ‘claims involving oxygen supply lines’ predating 1990. The aim of this study was to assess the frequency of nitrous oxide‐related catastrophes during general anaesthesia in Germany, Austria, and Switzerland. As nitrous oxide‐related anaesthesia casualties are rare but generally prosecuted, they almost invariably attract significant media attention. We scanned mass media archives from April 2004 until October 2006 for nitrous oxide‐related disasters during general anaesthesia. This approach detected six incidents which were almost certainly nitrous oxide ventilation‐related deaths. Searching non‐scientific data bases demonstrates that severe incidents involving oxygen supply lines occurred after 1990, and may be much more frequent than previously thought.

Repeat autoclaving does not remove protein deposits from the classic laryngeal mask airway

Introduction: We tested the hypothesis that repeated autoclaving removes protein deposits from the classic laryngeal mask airway (LMA). Methods: Twenty previously used LMAs were hand washed, machine washed, dried, autoclaved and randomly allocated into four equal‐sized groups for repeat autoclaving on 0 (control), 1, 2 and 3 occasions. After the final autoclave cycle, the LMAs were immersed in a protein‐staining solution, rinsed, dried and a high‐resolution digital image taken of the dorsal and ventral surfaces. The severity of staining was scored by two blinded observers. Results: All LMAs were stained. There was no reduction in staining with repeat autoclaving. Conclusions: Repeat autoclaving does not remove protein deposits from the LMA.

Comparison of guided insertion of the LMA ProSeal vs the i-gel.

In a randomised, non‐crossover study, we tested the hypothesis that the ease of insertion using a duodenal tube guided insertion technique and the oropharyngeal leak pressure differ between the LMA ProSeal™ and the i‐gel™ in non‐paralysed, anesthetised female subjects. One hundred and fifty‐two females aged 19–70 years were studied. Insertion success rate, insertion time and oropharyngeal leak pressure were measured. First attempt and overall insertion success were similar (LMA ProSeal, 75/76 (99%) and 76/76 (100%); i‐gel 73/75 (97%) and 75 (100%), respectively). Mean (SD) insertion times were similar (LMA ProSeal, 40 (16) s; i‐gel 43 (21) s). Mean oropharyngeal leak pressure was 7 cmH2O higher with the LMA ProSeal (p < 0.0001). Insertion of the LMA ProSeal and i‐gel is similarly easy using a duodenal tube guided technique, but the LMA ProSeal forms a more effective seal for ventilation.

ORIGINAL ARTICLE: Comparison of guided insertion of the LMA ProSeal™ vs the i-gel™

In a randomised, non‐crossover study, we tested the hypothesis that the ease of insertion using a duodenal tube guided insertion technique and the oropharyngeal leak pressure differ between the LMA ProSeal™ and the i‐gel™ in non‐paralysed, anesthetised female subjects. One hundred and fifty‐two females aged 19–70 years were studied. Insertion success rate, insertion time and oropharyngeal leak pressure were measured. First attempt and overall insertion success were similar (LMA ProSeal, 75/76 (99%) and 76/76 (100%); i‐gel 73/75 (97%) and 75 (100%), respectively). Mean (SD) insertion times were similar (LMA ProSeal, 40 (16) s; i‐gel 43 (21) s). Mean oropharyngeal leak pressure was 7 cmH2O higher with the LMA ProSeal (p < 0.0001). Insertion of the LMA ProSeal and i‐gel is similarly easy using a duodenal tube guided technique, but the LMA ProSeal forms a more effective seal for ventilation.

Protein cross-contamination during batch cleaning and autoclaving of the ProSeal laryngeal mask airway.

We tested the hypothesis that protein cross‐contamination occurs during batch cleaning and autoclaving of a reusable extraglottic airway device, the ProSeal™ laryngeal mask airway. At the end of each day for 10 days, nine laryngeal mask airways that had been used for non‐intra‐oral surgery were cleaned and autoclaved alongside a new unused laryngeal mask airway. In addition, a new unused laryngeal mask airway underwent the same cleaning and autoclaving procedures in isolation. Protein staining was more frequently detected on the unused laryngeal mask airways that were processed by batch rather than in isolation (p < 0.01). Protein staining was detected on all unused laryngeal mask airways that were processed by batch, but none on those processed in isolation. Protein staining was more severe with the used compared with the unused laryngeal mask airways (p < 0.001). We conclude that protein cross‐contamination of the laryngeal mask airway occurs during batch cleaning and autoclaving and recommend that reusable airway devices are cleaned in isolation.

A randomised, non-crossover study of the GuardianCPV Laryngeal Mask versus the LMA Supreme in paralysed, anaesthetised female patients.

We investigated the hypothesis that the oropharyngeal leak pressure would differ between the GuardianCPV™ and the LMA Supreme™ in anaesthetised patients. We randomly assigned 120 patients to receive either the GuardianCPV or the LMA Supreme for airway management. Oropharyngeal leak pressure was measured during cuff inflation from 0 to 40 ml in 10‐ml steps. In addition, intracuff pressure, fibreoptic position of the airway and drain tube, device insertion success, ventilation success, blood staining and airway morbidity were determined. Mean (SD) oropharyngeal leak pressures for clinically acceptable cuff volumes of 20–40 ml were 31 (7) cmH2O for the GuardianCPV and 27 (7) cmH2O for the LMA Supreme (p < 0.0001); mean (SD) intracuff pressures were 68 (33) cmH2O and 88 (43) cmH2O (p < 0.0001), respectively. We found no differences in device insertion success, ventilation success, fibreoptic position of the airway and drain tube, blood staining or airway morbidity. We conclude that the oropharyngeal leak pressure is better for the GuardianCPV than for the LMA Supreme in anaesthetised patients.