Do mask aperture bars of extraglottic airway devices prevent prolapse of epiglottis causing airway obstruction? A randomized crossover trial in anesthetized adult patients.

STUDY OBJECTIVE: The study objective is to determine whether extraglottic airway devices (EADs) with or without mask aperture bars (MABs) result in similar anatomical positions in patients undergoing surgery. DESIGN: Prospective, randomized, crossover comparison of four extraglottic airway devices. SETTING: Operating theatre at a large teaching hospital. PATIENTS: Eighty consenting patients scheduled to undergo surgery with general anesthesia. INTERVENTIONS: Patients were randomly allocated to receive anesthesia with one of four tested EADs. Two versions of each EAD were inserted in random order; one with and one without MABs. MEASUREMENTS AND MAIN RESULTS: Endoscopic evaluation did not demonstrate any difference between the EADs with or without MABs. Contact between MABs and arytenoids (n=15) and herniation of arytenoids (n=7) was restricted to the Cobra-group patients. In nine patients the epiglottis made contact with a MAB, although this contact was very limited and often unilateral. CONCLUSION: This study demonstrated that the anatomical position of the four tested single-use EADs is similar with or without mask aperture bars. We therefore question whether MABs have a protective role in prevention of airway occlusion and whether MABs are essential components. In the overall majority of EADs with MABs, the latter did not prevent contact with the epiglottis. Contact and herniation of the laryngeal structures are seen more frequently when more than two MABs are present.

The StyletScope is a better intubation tool than a conventional stylet during simulated cervical spine immobilization.

PURPOSE: We compare the StyletScope fibreoptic stylet (FOS) and the Satin Slip conventional metal stylet (CMS), during simulated difficult airway management with manual-in-line stabilization in terms of ease of intubation and esophageal intubation. METHODS: 193 patients (ASA I-II, 18-80 yr) were studied in a non-crossover, randomized fashion. Manual-in-line stabilization was applied and the best laryngoscopic view obtained. For the CMS, the primed tracheal tube was advanced under direct vision if Cormack-Lehane grade 1/2, placed behind the epiglottis and advanced blindly if grade 3, and intubation was not attempted if grade 4. For the FOS, the primed tracheal tube was advanced under the direct vision if grade 1/2 and under fibreoptic vision if grade 3/4. RESULTS: Intubation was successful more frequently (P = 0.02) and required fewer attempts (P = 0.003) with the FOS than the CMS. Intubation with the FOS was successful more frequently (P = 0.02) and required fewer attempts (P = 0.007) than the CMS if grade 3/4. For both stylets, intubation required fewer attempts (P < 0.007) and was quicker (P

A comparison of sex- and weight-based ProSeal laryngeal mask size selection criteria: a randomized study of healthy anesthetized, paralyzed adult patients.

BACKGROUND: The authors compared the manufacturer's weight-based formula (size 3 for weight < 50 kg, size 4 for weight 50-70 kg, and size 5 for weight > 70 kg) with a sex-based formula (size 4 for women and size 5 for men) for selecting the appropriate size of ProSeal laryngeal mask airway. METHODS: Two hundred thirty-seven healthy, anesthetized, paralyzed adult patients (American Society of Anesthesiologists physical status I or II; age, 18-80 yr) were randomly allocated for weight- or sex-based size selection. An experienced user inserted the ProSeal laryngeal mask airway with the digital technique. The following were compared: ease of insertion, oropharyngeal leak pressure, ease of ventilation, gas exchange, location of gas leak, anatomic position, mucosal injury, and postoperative pharyngolaryngeal problems. Intraoperative and postoperative data collection were unblinded and blinded, respectively. RESULTS: Ease of insertion, anatomic position, gas exchange, mucosal injury, and postoperative pharyngolaryngeal problems were similar between groups. For the sex-based group, larger ProSeal laryngeal mask airways were selected more frequently (P < 0.0001), oropharyngeal leak pressure (P = 0.02) was higher, leak volume (P = 0.004) and leak fraction (P = 0.007) were lower, and oropharyngeal leaks (P = 0.03) were detected less frequently. CONCLUSION: Size selection for the ProSeal laryngeal mask airway is equally effective using the manufacturer's weight-based formula or the sex-based formula in healthy, anesthetized, paralyzed adult patients, but leakage of small volumes of air from the mouth occurs less frequently with the sex-based formula.

A silicone-based wire-reinforced tracheal tube with a hemispherical bevel reduces nasal morbidity for nasotracheal intubation.

UNLABELLED: We tested the hypothesis that a silicone-based wire-reinforced tracheal tube with a hemispherical bevel is superior to a polyvinyl chloride (PVC)-based precurved tube with a conventional diagonal bevel for nasotracheal intubation. Eighty anesthetized paralyzed adults (ASA physical status I-II) requiring nasotracheal intubation for tonsillectomy were randomly allocated into two equal-sized groups for airway management with the silicone tracheal tube or PVC tracheal tube. Intubation was subdivided into three phases: 1). passage through the nose into the pharynx, 2). laryngoscope-guided passage into the glottic inlet, and 3). laryngoscope-guided passage into the trachea. A specific sequence of airway maneuvers was followed at each stage if it was unsuccessful. The number of attempts and intubation time were documented by an unblinded observer. The frequency of epistaxis and postoperative nasal complications was documented by blinded observers. There were no intubation failures. The number of attempts at pharyngeal (47 versus 56; P = 0.04) and tracheal (43 versus 55; P = 0.005) placement was smaller for the silicone tracheal tube, but the number of attempts at glottic placement was more (72 versus 49; P < 0.0001). Intubation time was similar. The frequency (32% versus 80%; P < 0.0001) and severity of epistaxis were less for the silicone tracheal tube. The total number of postoperative nasal symptoms was smaller for the silicone tracheal tube (10 versus 21; P < 0.05). We conclude that the pharyngeal and tracheal placement phases of nasotracheal intubation require fewer attempts with the silicone tracheal tube than the PVC tracheal tube but that the glottic placement phase requires more attempts. Nasal morbidity is less common with the silicone tracheal tube. IMPLICATIONS: The pharyngeal and tracheal placement phases of nasotracheal intubation require fewer attempts with a silicone-based wire-reinforced tracheal tube with a hemispherical bevel than with a polyvinyl chloride-based precurved tracheal tube with a conventional diagonal bevel, but the glottic placement phase requires more attempts. Nasal morbidity is less common with the silicone tracheal tube.

Influence of nitrous oxide on minimum alveolar concentration of sevoflurane for laryngeal mask insertion in children.

BACKGROUND: Inhalational induction with sevoflurane and nitrous oxide is frequently used for Laryngeal Mask Airway (LMA; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) insertion in children. The authors determined the influence of nitrous oxide on the minimum alveolar concentration (MAC) of sevoflurane for LMA insertion. METHODS: One hundred twenty unpremedicated children (age, 1-9 yr; American Society of Anesthesiologists physical status I) were randomly assigned to receive 1 of 15 end-tidal concentrations of nitrous oxide and sevoflurane for inhalational induction via a facemask: 0% nitrous oxide with 1.2, 1.4, 1.6, 1.8, or 2.0% sevoflurane; 33% nitrous oxide with 0.8, 1.0, 1.2, 1.4, or 1.6% sevoflurane; or 67% nitrous oxide with 0.4, 0.6, 0.8, 1.0, or 1.2% sevoflurane. The LMA was inserted after steady state end-tidal anesthetic concentrations had been maintained for 15 min. The response to insertion was recorded by three independent blinded observers. The interaction between nitrous oxide and sevoflurane was determined using logistic regression analysis. RESULTS: The MAC of sevoflurane for LMA insertion (95% confidence limit) was 1.57% (1.42-1.72%), and the concentration of sevoflurane required to prevent movement in 95% of children was 1.99% (1.81-2.57%). The addition of 33% and 67% nitrous oxide linearly decreased the MAC of sevoflurane for LMA insertion by 22% and 49%, respectively (P < 0.001). The interaction coefficient between nitrous oxide and sevoflurane did not differ from zero (P = 0.7843), indicating that the relation was additive. CONCLUSIONS: Nitrous oxide and sevoflurane suppress the responses to LMA insertion in a linear and additive fashion in children.

Flexible lightwand-guided tracheal intubation with the intubating laryngeal mask Fastrach in adults after unpredicted failed laryngoscope-guided tracheal intubation.

BACKGROUND: The authors determined the efficacy of using the intubating laryngeal mask airway Fastrach (ILM) as a ventilatory device and aid to flexible lightwand-guided tracheal intubation in patients with unpredicted failed laryngoscope-guided tracheal intubation when managed by experienced anesthetists. METHODS: During a 27-month period, 16 experienced anesthetists agreed to use the ILM as an airway device and airway intubator in patients (aged > 18 yr) with predicted normal airways who were subsequently found to be difficult to intubate (three failed attempts at laryngoscopy). Intubation via the ILM was performed with a flexible lightwand. The number of attempts at ILM placement, the number of adjusting maneuvers, the number of attempts at tracheal intubation via the ILM,and any episodes of hypoxia (oxygen saturation < 90%) were recorded. RESULTS: Forty-four of 11,621 patients (0.4%) met the inclusion criteria. ILM insertion and ventilation was successful at the first attempt in 40 of 44 patients (91%) and at the second attempt in 4 of 44 (9%). Flexible lightwand-guided tracheal intubation via the ILM was successful in 38 of 44 patients (86%) at the first attempt, 3 of 44 (7%) at the second attempt, 2 of 44 (5%) at the third to fifth attempts, and failed in 1 of 44 (2%). The median number of adjusting maneuvers before successful intubation was 1 (range, 0-4). Hypoxia occurred in 5 patients before ILM insertion (range, 52-82%), but none after ILM insertion. No patient developed hypoxia during or after intubation via the ILM. CONCLUSION: The ILM is an effective ventilatory device and aid to flexible lightwand-guided tracheal intubation in adult patients with predicted normal airways in whom laryngoscope-guided tracheal intubation subsequently fails when managed by experienced anesthetists.

Airway management outside the operating room.

The choice of airway device for resuscitation depends on the skill of the user, the equipment available, the conscious state of the patient, the location of the patient and the probable cause of the cardiorespiratory arrest. Extraglottic airway devices are recommended by the European and American Resuscitation Councils for use when intubation skills are lacking. In this review, we discuss recent research relevant to the use of extraglottic airway devices in resuscitation.