M. Kleine-Brueggeney

Crossover Comparison of the Laryngeal Mask Supreme™ and the i-gel™ in Simulated Difficult Airway Scenario in Anesthetized Patients

Background:The single-use supraglottic airway devices LMA-Supreme™ (LMA-S™; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) and i-gel™ (Intersurgical Ltd, Wokingham, Berkshire, United Kingdom) have a second tube for gastric tube insertion. Only the LMA-S™ has an inflatable cuff. They have the same clinical indications and might be useful for difficult airway management. This prospective, crossover, randomized controlled trial was performed in a simulated difficult airway scenario using an extrication collar limiting mouth opening and neck movement. Methods:Sixty patients were included. Both devices were placed in random order in each patient. Primary outcome was overall success rate. Other measurements were time to successful ventilation, airway leak pressure, fiberoptic glottic view, and adverse events. Results:Success rate for the LMA-S™ was 95% versus 93% for the i-gel™ (P = 1.000). LMA-S™ needed shorter insertion time (34 ± 12 s vs. 42 ± 23 s, P = 0.024). Tidal volumes and airway leak pressure were similar (LMA-S™ 26 ± 8 cm H20; i-gel™ 27 ± 9 cm H20; P = 0.441). Fiberoptic view through the i-gel™ showed less epiglottic downfolding. Overall agreement in insertion outcome was 54 (successes) and 1 (failure) or 55 (92%) of 60 patients. The difference in success rate was 1.7% (95% CI –11.3% to 7.6%). Conclusions:Both airway devices had similar insertion success and clinical performance in the simulated difficult airway situation. The authors found less epiglottic downfolding and better fiberoptic view but longer insertion time with the i-gel™. Our study shows that both devices are feasible for emergency airway management in patients with reduced neck movement and limited mouth opening.

Performance of the Pediatric-sized i-gel Compared with the Ambu AuraOnce Laryngeal Mask in Anesthetized and Ventilated Children

Background:This prospective, randomized, controlled trial compares the performance of the pediatric i-gel (Intersurgical Ltd., Wokingham, United Kingdom) with the Ambu AuraOnce laryngeal mask (Ambu A/S, Ballerup, Denmark) in anesthetized and ventilated children. Methods:With ethics committee approval and written informed consent, the authors included 208 children, aged 0–17 yr, scheduled for elective day-surgery under general anesthesia. The primary outcome variable was oropharyngeal leak pressure. Other outcome variables were first-attempt and overall success, time to sufficient ventilation, and adverse events. Results:Demographic data did not differ between groups. The leak pressure of the i-gel was significantly higher than the leak pressure of the Ambu (mean ± SD: 22 ± 5 cm H2O vs. 19 ± 3, P < 0.01). First-attempt success was 91% for the i-gel and 93% for the Ambu (P = 0.50). Overall success was 93% for the i-gel versus 98% for the Ambu (P = 0.10). Successfully inserted i-gels needed to be secured by taping in place to ensure the seal in 44% (0% with the Ambu, P < 0.01). Insertion was faster with the Ambu (24 ± 8 s vs. 27 ± 11, P = 0.02). There were no major side effects with either device. Conclusions:The leak pressure of the i-gel was statistically but not clinically significantly higher than the leak pressure of the Ambu. Time to insertion was longer with the i-gel. Both airway devices are suitable for positive pressure ventilation with high success rates in infants and children. Because the i-gel is prone to sliding out, it must be taped in place to avoid loss of the airway.

Evaluation of six videolaryngoscopes in 720 patients with a simulated difficult airway: a multicentre randomized controlled trial

BACKGROUND Videolaryngoscopes are aggressively marketed, but independent evaluation in difficult airways is scarce. This multicentre, prospective randomized controlled trial evaluates six videolaryngoscopes in patients with a simulated difficult airway. METHODS With ethics committee approval and written informed consent, 12 senior anaesthetists intubated the trachea of 720 patients. A cervical collar limited mouth opening and neck movement, making intubation difficult. We evaluated three unchannelled (C-MAC™ D-blade, GlideScope™, and McGrath™) and three channelled videolaryngoscopes (Airtraq™, A.P. Advance™ difficult airway blade, and KingVision™). The primary outcome was first-attempt intubation success rate. Secondary outcomes included overall success rate, laryngeal view, intubation times, and side-effects. The primary hypothesis for every videolaryngoscope was that the 95% confidence interval of first-attempt success rate is ≥90%. RESULTS Mouth opening was decreased from 46 (sd 7) to 23 (3) mm with the cervical collar. First-attempt success rates were 98% (McGrath™), 95% (C-MAC™ D-blade), 87% (KingVision™), 85% (GlideScope™ and Airtraq™), and 37% (A.P. Advance™, P<0.01). The 95% confidence interval of first-attempt success rate was >90% only for the McGrath™. Overall success, laryngeal view, and intubation times differed significantly between videolaryngoscopes (all P<0.01). Side-effects were minor. CONCLUSIONS This trial revealed differences in the performance of six videolaryngoscopes in 720 patients with restricted neck movement and limited mouth opening. In this setting, first-attempt success rates were 85-98%, except for the A.P. Advance™ difficult airway blade. Highest success and lowest tissue trauma rates were achieved by the McGrath™ and C-MAC™ D-blade, highlighting the importance of the videolaryngoscope blade design. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov: identifier NCT01692535.

CYP2D6- and CYP3A-dependent enantioselective plasma concentrations of ondansetron in postanesthesia care.

BACKGROUND: An influence of polymorphic cytochromes P450 (CYP) 2D6 genetic variants on antiemetic efficacy of ondansetron has been suggested. However, the role of CYP3A in ondansetron metabolism and efficacy has been unclear. In this study, we evaluated the hypothesis that genotype-dependent CYP2D6 and CYP3A activity selectively influences plasma concentrations of ondansetron enantiomers. Additionally, the effects of doubling the ondansetron dose on genotype-dependent plasma concentrations were investigated. METHODS: Patients received IV ondansetron 4 or 8 mg for emesis prophylaxis before emergence from anesthesia. The CYP2D6-dependent activity score representing no, decreased, normal, or increased CYP2D6 enzyme activity as well as CYP3A low (CYP3A5*3/*3) and high expressor status (CYP3A5 wt/wt or wt/*3) were determined. Plasma concentrations of R- and S-ondansetron enantiomers were measured by liquid chromatography–tandem mass spectrometry. Area under the plasma concentration-time curves (AUCs) of R- and S-ondansetron were associated with CYP2D6 and CYP3A5 genotype-dependent enzyme activity. RESULTS: Complete data of 141 subjects were analyzed. Concentrations of S-ondansetron differed between CYP2D6 activity groups (P = 0.01) with highest values in patients with no CYP2D6 activity (mean [95% confidence interval]: 362.5 [238.3/486.7] h · ng/mL) and lowest values in those with increased activity (149.6 [114.5/184.8] h · ng/mL) compared with subjects displaying genotypes resulting in reduced or normal CYP2D6 activity (263.6 [228.8/298.8], 255.4 [228.2/282.7] h · ng/mL). AUC of R-ondansetron was 2 times higher in CYP3A5 low expressors compared with high expressors (281.5 [248.6/314.3] vs 142.5 [92.4/192.7] h · ng/mL; P = 0.003). Doubling the ondansetron dose increased plasma concentrations only in individuals with low CYP3A activity, but not in individuals with high enzyme activity (P < 0.001). CONCLUSIONS: The metabolism of ondansetron seems to be enantioselective. In this postoperative setting, CYP2D6 activity scores correlated with concentrations of S-ondansetron, whereas CYP3A5 expressor status mainly influenced concentrations of R-ondansetron. Genetically and environmentally determined CYP2D6 and CYP3A enzyme activity might have implications for antiemetic efficacy.

Blind intubation of anaesthetised children with supraglottic airway devices AmbuAura-i and Air-Q cannot be recommended: A randomised controlled trial.

BACKGROUND Paediatric supraglottic airway devices AmbuAura-i and Air-Q were designed as conduits for tracheal intubation. Although fibreoptic-guided intubation has proved successful, blind intubation as a rescue technique has never been evaluated. OBJECTIVE Evaluation of blind intubation through AmbuAura-i and Air-Q. On the basis of fibreoptic view data, we hypothesised that the success rate with the AmbuAura-i would be higher than with the Air-Q. DESIGN A randomised controlled trial. SETTING University Childrens’ Hospital; September 2012 to July 2014. PATIENTS Eighty children, American Society of Anesthesiologists (ASA) class I to III, weight 5 to 50 kg. INTERVENTIONS Tracheal intubation was performed through the randomised device with the tip of a fibrescope placed inside and proximal to the tip of the tracheal tube. This permitted sight of tube advancement, but without fibreoptic guidance (visualised blind intubation). MAIN OUTCOME MEASURES Primary outcome was successfully visualised blind intubation; secondary outcomes included supraglottic airway device success, insertion times, airway leak pressure, fibreoptic view and adverse events. RESULTS Personal data did not differ between groups. In contrast to our hypothesis, blind intubation was possible in 15% with the Air-Q and in 3% with the AmbuAura-i [95% confidence interval (95% CI) 6 to 31 vs. 0 to 13%; P = 0.057]. First attempt supraglottic airway device insertion success rates were 95% (Air-Q) and 100% (AmbuAura-i; 95% CI 83 to 99 vs. 91 to 100; P = 0.49). Median leak pressures were 18 cmH2O (Air-Q) and 17 cmH2O [AmbuAura-i; interquartile range (IQR) 14 to 18 vs. 14 to 19 cmH2O; P = 0.66]. Air-Q insertion was slower (27 vs. 19 s, P < 0.001). There was no difference in fibreoptic view, or adverse events (P > 0.05). In one child (Air-Q size 1.5, tube size 3.5), the tube dislocated during device removal. CONCLUSION Ventilation with both devices is reliable, but success of blind intubation is unacceptably low and cannot be recommended for elective or rescue purposes. If intubation through a paediatric supraglottic airway device is desired, we suggest that fibreoptic guidance is used. TRIAL REGISTRATION Clinicaltrials.gov identifier: NCT01692522.

Awake tracheal intubation using the Sensascope in 13 patients with an anticipated difficult airway

We present the use of the SensaScope™, an S‐shaped rigid fibreoptic scope with a flexible distal end, in a series of 13 patients at high risk of, or known to have, a difficult intubation. Patients received conscious sedation with midazolam or fentanyl combined with a remifentanil infusion and topical lidocaine to the oral mucosa and to the trachea via a trans‐cricoid injection. Spontaneous ventilation was maintained until confirmation of tracheal intubation. In all cases, tracheal intubation was achieved using the SensaScope. The median (IQR [range]) insertion time (measured from the time the facemask was taken away from the face until an end‐expiratory CO2 reading was visible on the monitor) was 58 s (38–111 [28–300]s). In nine of the 13 cases, advancement of the SensaScope into the trachea was easy. Difficulties included a poor view associated with a bleeding diathesis and saliva, transient loss of spontaneous breathing, and difficulty in advancing the tracheal tube in a patient with unforeseen tracheal narrowing. A poor view in two patients was partially improved by a high continuous flow of oxygen. The SensaScope may be a valuable alternative to other rigid or flexible fibreoptic scopes for awake intubation of spontaneously breathing patients with a predicted difficult airway.

SWIVIT - Swiss video-intubation trial evaluating video-laryngoscopes in a simulated difficult airway scenario: study protocol for a multicenter prospective randomized controlled trial in Switzerland

BackgroundVideo-laryngoscopes are marketed for intubation in difficult airway management. They provide a better view of the larynx and may facilitate tracheal intubation, but there is no adequately powered study comparing different types of video-laryngoscopes in a difficult airway scenario or in a simulated difficult airway situation.Methods/DesignThe objective of this trial is to evaluate and to compare the clinical performance of three video-laryngoscopes with a guiding channel for intubation (Airtraq™, A. P. Advance™, King Vision™) and three video-laryngoscopes without an integrated tracheal tube guidance (C-MAC™, GlideScope™, McGrath™) in a simulated difficult airway situation in surgical patients. The working hypothesis is that each video-laryngoscope provides at least a 90% first intubation success rate (lower limit of the 95% confidence interval >0.9). It is a prospective, patient-blinded, multicenter, randomized controlled trial in 720 patients who are scheduled for elective surgery under general anesthesia, requiring tracheal intubation at one of the three participating hospitals. A difficult airway will be created using an extrication collar and taping the patients’ head on the operating table to substantially reduce mouth opening and to minimize neck movement. Tracheal intubation will be performed with the help of one of the six devices according to randomization. Insertion success, time necessary for intubation, Cormack-Lehane grade and percentage of glottic opening (POGO) score at laryngoscopy, optimization maneuvers required to aid tracheal intubation, adverse events and technical problems will be recorded. Primary outcome is intubation success at first attempt.DiscussionWe will simulate the difficult airway and evaluate different video-laryngoscopes in this highly realistic and clinically challenging scenario, independently from manufacturers of the devices. Because of the sufficiently powered multicenter design this study will deliver important and cutting-edge results that will help clinicians decide which device to use for intubation of the expected and unexpected difficult airway.Trial registrationNCT01692535

Evaluation of three unchannelled videolaryngoscopes and the Macintosh laryngoscope in patients with a simulated difficult airway: a randomised, controlled trial†

This prospective randomised, controlled trial compares the performance of three unchannelled videolaryngoscopes (KingVision™, Airtraq™, A.P. Advance™ MAC) and the standard Macintosh laryngoscope. With ethics committee approval and written informed consent, 480 patients were included. A difficult airway was created with a cervical collar, limiting mouth opening and neck movement. Primary outcome was first‐attempt orotracheal intubation success. Overall success, laryngeal view, intubation difficulty scale, handling, intubation times and side‐effects were secondary outcomes. First‐attempt success rates were: KingVision 90% (95% CI 83–94%), Airtraq 82% (74–88%), A.P. Advance MAC 49% (40–58%), Macintosh 44% (35–53%; p < 0.001). The 95% confidence interval of first‐attempt success rate was thus below 90% for all devices, but the KingVision and the Airtraq performed better than the A.P. Advance MAC and the Macintosh laryngoscope. Also, performance was better with the KingVision and the Airtraq in terms of overall success, laryngeal view, intubation difficulty scale and quality of view. Problems with tube advancement were a frequent cause of intubation failure. In summary, the KingVision and the Airtraq performed better than the A.P. Advance MAC and the Macintosh laryngoscope. Success rates of the unchannelled KingVision and Airtraq were similar to those of their channelled versions reported previously, indicating that performance largely depends on blade design rather than the presence of a channel for tube advancement.

Transnasal humidified rapid insufflation ventilatory exchange for oxygenation of children during apnoea: a prospective randomised controlled trial.

Background: Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) comprises the administration of heated, humidified, and blended air/oxygen mixtures via nasal cannula at rates of ≥2 litres kg−1 min−1. The aim of this randomized controlled study was to evaluate the length of the safe apnoea time using THRIVE with two different oxygen concentrations (100% vs 30% oxygen) compared with standard low‐flow 100% oxygen administration. Methods: Sixty patients, aged 1–6 yr, weighing 10–20 kg, undergoing general anaesthesia for elective surgery, were randomly allocated to receive one of the following oxygen administration methods during apnoea: 1) low‐flow 100% oxygen at 0.2 litres kg−1 min−1; 2) THRIVE 100% oxygen at 2 litres kg−1 min−1; and 3) THRIVE 30% oxygen at 2 litres kg−1 min−1. Primary outcome was time to desaturation to 95%. Termination criteria included SpO2 decreased to 95%, transcutaneous CO2 increased to 65 mmHg, or apnoea time of 10 min. Results: The median (interquartile range) [range] apnoea time was 6.9 (5.7–7.8) [2.8–10.0] min for low‐flow 100% oxygen, 7.6 (6.2–9.1) [5.2–10.0] min for THRIVE 100% oxygen, and 3.0 (2.4–3.7) [0.2–5.3] min for THRIVE 30% oxygen. No significant difference was detected between apnoea times with low‐flow and THRIVE 100% oxygen administration (P=0.15). THRIVE with 30% oxygen demonstrated significantly shorter apnoea times (P<0.001) than both 100% oxygen modalities. The overall rate of transcutaneous CO2 increase was 0.57 (0.49–0.63) [0.29–8.92] kPa min−1 without differences between the 3 groups (P=0.25). Conclusions: High‐flow 100% oxygen (2 litres kg−1 min−1) administered via nasal cannulas did not extend the safe apnoea time for children weighing 10–20 kg compared with low‐flow nasal cannula oxygen (0.2 litres kg−1 min−1). No ventilatory effect was observed with THRIVE at 2.0 litres kg−1 min−1. Clinical trial registration: NCT02979067.

The performance of rigid scopes for tracheal intubation: a randomised, controlled trial in patients with a simulated difficult airway

We compared the Bonfils™ and SensaScope™ rigid fibreoptic scopes in 200 patients with a simulated difficult airway randomised to one of the two devices. A cervical collar inhibited neck movement and reduced mouth opening to a mean (SD) of 23 (3) mm. The primary outcome parameter was overall success of tracheal intubation; secondary outcomes included first‐attempt success, intubation times, difficulty of intubation, fibreoptic view and side‐effects. The mean (95% CI) overall success rate was 88 (80–94)% for the Bonfils and 89 (81–94)% for the SensaScope (p = 0.83). First‐attempt intubation success rates were 63 (53–72)% for the Bonfils and 72 (62–81)% for the SensaScope (p = 0.17). Median (IQR [range]) intubation time was significantly shorter with the SensaScope (34 (20–84 [5–240]) s vs. 45 (25–134 [12–230]) s), and fibreoptic view was significantly better with the SensaScope (full view of the glottis in 79% with the SensaScope vs. 61% with the Bonfils). This might be explained by its steerable tip and the S‐formed shape, contributing to better manoeuvrability. There were no differences in the difficulty of intubation or side‐effects.