Tracheal intubation and cervical spine excursion: direct laryngoscopy vs. intubating laryngeal mask

Until recently, the most appropriate technique of intubating a patient with a cervical spine injury has been the subject of debate. Tracheal intubation by means of the intubating laryngeal mask (Fastrach), a modified conventional laryngeal mask airway, seems to require less neck manipulation. The aim of this study was to compare the excursion of the upper cervical spine during tracheal intubation using direct laryngoscopy with that during intubation via the laryngeal mask (Fastrach), by examination of lateral cervical spine radiographs in healthy young patients. The intubating laryngeal mask (Fastrach) caused less extension (at C1-2 and C2-3) than intubation by direct laryngoscopy. Direct laryngoscopy is still the fastest method to secure an airway provided no intubating difficulties are present. However, in trauma patients requiring rapid sequence induction and in whom cervical spine movement is limited or undesirable, the intubating laryngeal mask (Fastrach) is a safe and fast method by which to secure the airway.     

Tracheal intubation and sore throat: a mechanical explanation

Although tracheal intubation remains a valuable tool, it may result in pressure trauma and sore throat. The evidence for an association between these sequelae is not conclusive and sore throat may be caused at the time of intubation. This hypothesis was tested in a mechanical model and the results from tracheal intubation compared with those from insertion of a laryngeal mask airway, which is associated with a lower incidence of sore throat. Use of the model suggests that the tracheal tube and laryngeal mask airway impinge on the pharyngeal wall in different manners and involve different mechanisms for their conformation to the upper airway, but that in a static situation, the forces exerted on the pharyngeal wall are low with both devices. It also suggests that the incidence of sore throat should be lower for softer and smaller tracheal tubes and that the standard 'Magill' curve (radius of curvature 140 +/- 20 mm) is about optimum for the average airway.     

Tracheal intubation of morbidly obese patients: LMA CTrach vs direct laryngoscopy

Background. LMA CTrach^TM (CT), a modified version of the intubatingLMA Fastrach^TM, allows continuous video-endoscopy of the trachealintubation procedure. We tested the hypothesis that the CT isefficient for tracheal intubation of morbidly obese patientswho are at risk of a difficult airway. Methods. After Ethics’ Committee approval, 104 morbidlyobese patients (BMI >35 kg m^–2) scheduled for bariatricsurgery were included in this prospective study. Patients wererandomly assigned in two groups: tracheal intubation using directlaryngoscopy (DL) or the CT. Induction of anaesthesia was standardizedusing sufentanil, propofol and succinylcholine. Characteristicsand consequences of airway management were evaluated. Results. Preoperative characteristics of patients and consequencesof anaesthesia induction on physiological variables were similarin both groups. Difficulty in facemask ventilation was similarin both groups. Tracheal intubation was successfully carriedout with DL and CT. Forty-nine per cent of the patients fromthe CT group required laryngeal mask manipulation (ventilationand view optimization) resulting in increased duration of trachealintubation by 57 s as compared with DL. Oxygenation was of betterquality in the patients managed with CT than with DL. Blindtracheal intubation was mandatory in eight (17%) patients ofthe DL group, while tracheal intubation was seen in all patientsof the CT group. Conclusion. We demonstrated that the CT was an efficient airwaydevice for ventilation and tracheal intubation in case of adifficult airway in morbidly obese patients.      

Tracheal intubation through the intubating laryngeal mask in patients with unstable necks

BACKGROUND: In patients with unstable necks, the neck should be stabilized during induction of anaesthesia, but this may make tracheal intubation difficult. Awake intubation may produce straining, which could be detrimental to the unstable neck. METHODS: We studied 20 patients with unstable necks to examine the efficacy of insertion of the intubating laryngeal mask under conscious sedation (to minimize the possibility of losing a patent airway and to facilitate fibrescope-aided intubation) followed by tracheal intubation through the laryngeal mask after induction of anaesthesia (to reduce stress response to intubation). After the patient had been sedated with midazolam (up to 5 mg) and fentanyl (up to 100 microg), the intubating laryngeal mask was inserted. General anaesthesia was then induced with sevoflurane and tracheal intubation attempted. RESULTS: In all patients, tracheal intubation through the laryngeal mask succeeded without airway obstruction. Neither insertion of the mask under conscious sedation nor tracheal intubation after induction of anaesthesia caused straining, and only two patients moved upper extremities at intubation. Insertion of the laryngeal mask did not significantly alter blood pressure or heart rate. Tracheal intubation significantly increased blood pressure and heart rate, but the increase was considered to be small. CONCLUSIONS: In the patient with an unstable neck with a low risk of pulmonary aspiration, insertion of the intubating laryngeal mask while the patient is sedated may minimize difficulty in obtaining a patent airway before tracheal intubation and may facilitate a fibrescope-aided tracheal intubation; subsequent induction of anaesthesia before tracheal intubation may minimize stress response to intubation.     

Piriform fossa perforation during attempted tracheal intubation

Perforation of the piriform fossa is a rare complication of attempted tracheal intubation. The consequences vary from cervical emphysema to respiratory distress, mediastinitis, septic shock, empyema pyopneumothorax and death. The mortality rate due to mediastinitis is over 50%, so early diagnosis and management can improve survival. This case report describes one case and discusses the diagnosis and management of this complication.     

Randomized, controlled trial of the double setup tracheal tube during fibreoptic orotracheal intubation under general anaesthesia

Background. Impingement of the tracheal tube (ETT) on upperairway structures during railroading over the fibreoptic bronchoscope(FOB) occurs commonly. Potential complications of impingementinclude prolonged intubation time, leading to arterial desaturation,failed intubation and laryngeal trauma. The objective of thisrandomized, controlled trial was to assess the effect of thedouble setup ETT (a paediatric ETT is placed inside an adultETT) on the incidence of impingement during orotracheal fibreopticintubation. Method. Two hundred patients were randomized to have a singleETT or double setup ETT. After induction of anaesthesia, fibreopticorotracheal intubation was performed. The degree of impingementof the ETT during advancement over the FOB was assessed usinga standardized scoring system based on the manoeuvres requiredto overcome the impingement. Results. The incidence of impingement was lower using the doublesetup ETT compared with the single ETT (18 vs 93%, P<0.001).The double setup ETT also reduced the incidence of impingementrequiring more than a simple 90° counterclockwise rotationto achieve intubation (3 vs 14%, P=0.01) and reduced the medianintubation time (31 vs 35 s, P=0.046). Conclusions. The double setup ETT is effective in reducing ETTimpingement and in reducing intubation time. We did not findan association between ETT impingement and arterial desaturation. Br J Anaesth 2004; 92: 536–40     

Unexpected difficult intubation

Two cases of asymptomatic epiglottic cysts which presented as partial upper airway obstruction following induction of anaesthesia are described. The incidence, pathology and anaesthetic management are discussed.     

The relevance of clinical and radiological measurements in predicting difficulties in fibreoptic orotracheal intubation in adults

Resistance to the passage of the tracheal tube has been reported to occur in up to 36% of patients subjected to orotracheal fibreoptic intubation. In this prospective study we assessed five radiological measurements of the upper airway in an attempt to find anatomical causes of obstruction to passage of the tube. Forty-nine patients undergoing fibreoptic orotracheal intubation under general anaesthesia were studied. Pre-operatively, the Mallampati grade and the thyromental distance were assessed. The plain films, CT scans or MR images of the cervical spine were used for measurement of the position of the vocal cords, the length of the epiglottis and the size of the tongue. The resistance to the passage of the tube was graded as none, mild, moderate or severe. The length of the epiglottis and the size of the tongue, but not the position of the vocal cords, had positive correlations with the severity of impingement. The pre-operative bedside tests did not correlate with difficulties in fibreoptic intubation.     

Esmolol prevents movement and attenuates the BIS response to orotracheal intubation

Background. Beta-adrenergic agonists enhance behavioural andelectroencephalographic arousal reactions. We explored whetheradding esmolol, a short-acting ß₁-adrenoceptor antagonist,to propofol anaesthesia modified the bispectral index (BIS)during induction of anaesthesia and orotracheal intubation. Methods. Fifty patients were randomly allocated, in a double-blindfashion, to receive esmolol 1 mg kg^–1 followed by 250µg kg^–1 min^–1 or saline (control). Esmololor saline was started 6 min after a target-controlled infusion(TCI) of propofol (effect-site concentration 4 µg ml^–1).After loss of consciousness, and before administration of vecuronium0.1 mg kg^–1, a tourniquet was applied to one arm and inflatedto 150 mm Hg greater than systolic pressure. Eleven minutesafter the TCI began, the trachea was intubated; gross movementwithin the first min after orotracheal intubation was recorded.BIS was recorded at 10-s intervals. Mean arterial pressure (MAP)and heart rate were measured non-invasively every min. Results. There were no intergroup differences in BIS, heartrate or MAP before laryngoscopy. BIS increased significantlyafter orotracheal intubation (compared with the pre-laryngoscopyvalues) in the control group only, with a maximum increase of40 (SD 18)% vs 8 (11)% in the esmolol group (P<0.01). Maximumchanges in heart rate [45 (19)% vs 23 (14)%] and MAP [62 (24)%vs 45 (23)%] with orotracheal intubation were also significantlygreater in the control group than in the esmolol group. Morepatients in the control than in the esmolol group moved afterorotracheal intubation (23 vs 12, P<0.01). Conclusion. Esmolol not only attenuated haemodynamic and somaticresponses to laryngoscopy and orotracheal intubation, but alsoprevented BIS arousal reactions in patients anaesthetized withpropofol. Br J Anaesth 2002; 89: 857–62     

The clinical implication of the vocal cords-carina distance in anaesthetized Chinese adults during orotracheal intubation

Background. Previous studies have identified no strong correlationbetween patients' height and tracheal length in anaesthetizedpatients. We have attempted to compare vocal cords–carinadistance (VCD) in Chinese patients with the dimensions of fivecommonly used tracheal tubes. In addition, we attempted to finda surface anatomy measurement that would identify patients with‘short tracheas’. Methods. We measured VCD in 130 anaesthetized Chinese patientswith a fibreoptic bronchoscope. Also measurements were obtainedof the distal ends of five commonly used tracheal tubes. Weundertook various surface anatomy measurements on the patients'chest and neck region to predict those patients with short tracheas. Results. VCD averaged 12.6 (SD 1.4) cm. In seven patients (5%)this distance was particularly short (between 8.8 and 10.4 cm).Many of the commonly used tracheal tubes would be placed closeto or beyond the carina when the black intubation guide mark(s)is (are) at the level of the vocal cords. The VCD of     

Gabapentin attenuates the pressor response to direct laryngoscopy and tracheal intubation

Background. Laryngoscopy and tracheal intubation increase bloodpressure and heart rate (HR). The aim of the present study wasto investigate the effect of gabapentin when given before operationon the haemodynamic responses to laryngoscopy and intubation. Methods. Forty-six patients undergoing abdominal hysterectomyfor benign disease were randomly allocated to receive gabapentin1600 mg or placebo capsules at 6 hourly intervals starting theday (noon) before surgery. Anaesthesia was induced with propofoland cis-atracurium. Systolic, diastolic arterial blood pressures(SAP, DAP) and heart rate (HR) were recorded before and afterthe anaesthetic and 0, 1, 3, 5 and 10 min after tracheal intubation. Results. SAP was significantly lower in the gabapentin vs thecontrol group 0, 1, 3, 5 and 10 min after intubation [128 (27)vs 165 (41), P=0.001, 121 (14) vs 148 (29), P=0.0001, 115 (13)vs 134 (24), P=0.002, 111 (12) vs 126 (19), P=0.004 and 108(12) vs 124 (17), P=0.001 respectively]. DAP also was lowerin the gabapentin group 0, 1, 3, and 10 min after intubation[81 (18) vs 104 (19), P=0.0001, 77 (9) vs 91 (16), P=0.001,71 (10) vs 84 (13), P=0.001 and 67 (10) vs 79 (12), P=0.004].HR did not differ between the two groups at any time [82 (11)vs 83 (15), 79 (10) vs 80 (12), 86 (17) vs 92 (10), 82 (11)vs 88 (10), 81 (12) vs 81 (11), 77 (13) vs 79 (13), and 75 (15)vs 78 (12)]. Conclusion. Gabapentin, under the present study design attenuatesthe pressor response but not the tachycardia associated withlaryngoscopy and tracheal intubation.     

Comparison of a new video-optical intubation stylet versus the conventional malleable stylet in simulated difficult tracheal intubation

Handling and efficacy of a new video-optical intubation stylet were assessed in a simulated difficult tracheal intubation setting and compared with a conventional malleable stylet. Forty-five anaesthetists performed 10 tracheal intubations using both techniques. Laryngoscopy was performed by the observer, who created a grade 3 view according the classification by Cormack and Lehane. The time taken to place the tracheal tube and the final tracheal tube positions were documented. Mean (SD) intubation time for the video-optical stylet was 20.4 (7.7) s and for the malleable stylet 10.2 (3.3) s (p<0.01). With the video-optical stylet the trachea was correctly intubated in all 225 attempts; with the malleable stylet 44 (19.6%) oesophageal and 44 (19.6%) endobronchial intubations occurred (p<0.01). The video-optical intubation stylet enabled us to recognise inappropriate tracheal tube positions and to correct them immediately. This equipment can be considered a reliable and effective tool for management of the difficult airway.     

Videolaryngoscopy vs. direct Macintosh laryngoscopy in tracheal intubation in adults: a ranking systematic review and network meta-analysis

Videolaryngoscopes are thought to improve glottic view and facilitate tracheal intubation compared with the Macintosh direct laryngoscope. However, we currently do not know which one would be the best choice in most patients undergoing anaesthesia. We designed this systematic review with network meta-analyses to rank the different videolaryngoscopes and the Macintosh direct laryngoscope. We conducted searches in PubMed and a further five databases on 11 January 2021. We included randomised clinical trials with patients aged ≥16 years, comparing different videolaryngoscopes, or videolaryngoscopes with the Macintosh direct laryngoscope for the outcomes: failed intubation; failed first intubation attempt; failed intubation within two attempts; difficult intubation; percentage of glottic opening seen; difficult laryngoscopy; and time needed for intubation. We assessed the quality of evidence according to GRADE recommendations and included 179 studies in the meta-analyses. The C-MAC and C-MAC D-Blade were top ranked for avoiding failed intubation, but we did not find statistically significant differences between any two distinct videolaryngoscopes for this outcome. Further, the C-MAC D-Blade performed significantly better than the C-MAC Macintosh blade for difficult laryngoscopy. We found statistically significant differences between the laryngoscopes for time to intubation, but these differences were not considered clinically relevant. The evidence was judged as of low or very low quality overall. In conclusion, different videolaryngoscopes have differential intubation performance and some may be currently preferred among the available devices. Furthermore, videolaryngoscopes and the Macintosh direct laryngoscope may be considered clinically equivalent for the time taken for tracheal intubation. However, despite the rankings from our analyses, the current available evidence is not sufficient to ensure significant superiority of one device or a small set of them over the others for our intubation-related outcomes.     

Bullard laryngoscopy for tracheal intubation in a neonate with Pierre-Robin syndrome

In a newborn with Pierre-Robin syndrome, repeated attempts using standard direct laryngoscopy failed to visualize the glottis or even the tip of the epiglottis. In contrast, a clear view of the glottis was seen when the Bullard fibreoptic paediatric laryngoscope was used. Tracheal intubation was facilitated by ‘rail-roading’ the tube over a bougie which was threaded via the suction channel of the laryngoscope into the trachea. The report suggests that the Bullard fibreoptic laryngoscope can succeed to visualize the glottis in the newborn with Pierre-Robin syndrome, whenever the glottis cannot be brought within line-of-sight by standard laryngoscopy.     

Evaluation of the SCOTI device for confirming blind nasal intubation

The sonomatic confirmation of tracheal intubation (SCOTI) is a new device used to confirm the correct placement of tracheal tubes. It utilises a sonic technique for recognition of a resonating frequency for detection of tracheal intubation. We compared its predictive value with that of the clinical auscultatory method and a capnograph to confirm 132 blind nasal intubations using three different tracheal tubes [red rubber (n = 82), polyvinyl chloride (n = 33) and RAE preformed nasal (n = 17)]. SCOTI correctly identified 70.8% of intubations and chest auscultation did so 99.2% of times. All results were confirmed using a capnograph. The SCOTI device gave a false-negative value in 37 patients (28%) and a false-positive result in two patients (1.5%). The response time for confirming intubations was 2.5 (1.5) s for the SCOTI, 4.1 (1.1) s for a capnograph and 40 (9.4) s for the auscultatory method. The erroneous results shown by the SCOTI device were highest when polyvinyl chloride tubes with a Murphy's eye were used for intubation. This study shows that this device is not very useful for ascertaining the correct placement of tracheal tubes after blind nasal intubation.