Tag Archives: difficult airway


NAP 4 Podcast

Check out EMCrit.org for our Podcast interview with Professor Jonathan Benger, the Emergency Physician who contributed to the design, execution, and analysis of the important NAP 4 national airway audit, which has important learning points for all of us involved in pre-hospital, emergency, or ICU airway management.

EMCrit Podcast

2016 Update
An important follow up study showing the effect of the NAP 4 Audit:
A national survey of the impact of NAP4 on airway management practice in United Kingdom hospitals: closing the safety gap in anaesthesia, intensive care and the emergency department
Br. J. Anaesth. (2016) 117 (2): 182-190.

Disposable flexible intubating scope

There is now a single use flexible intubating device that compares favourably with conventional fibreoptic devices. It does not have fibreoptic cables, but rather has a small camera at its tip illuminated by an LED. The image is transmitted via a cable in the device to a reusable screen. Dr Cook’s team in Bath, England have an extensive track record of evaluating new airway devices, and they report their assessment of this gadget in a manikin-based study. I think this may extend the airway management options to departments or teams for whom the cost and maintenance of conventional fibreoptic equipment is prohibitive.

We compared the Ambu aScopeā„¢ with a conventional fibrescope in two simulated settings. First, 22 volunteers performed paired oral and nasal fibreoptic intubations in three different manikins: the Laerdal Airway Trainer, Bill 1 and the Airsim (a total of 264 intubations). Second, 21 volunteers intubated the Airway Trainer manikin via three supraglottic airways: classic and intubating laryngeal mask airways and i-gel (a total of 66 intubations). Performance of the aScope was good with few failures and infrequent problems. In the first study, choice of fibrescope had an impact on the number of user-reported problems (p=0.004), and user-assessed ratings of ease of endoscopy (p<0.001) and overall usefulness (p<0.001), but not on time to intubate (p=0.19), or ease of railroading (p=0.72). The manikin chosen and route of endoscopy had more consistent effects on performance: best performance was via the nasal route in the Airway Trainer manikin. In the second study, the choice of fibrescope did not significantly affect any performance outcome (p=0.3), but there was a significant difference in the speed of intubation between the devices (p=0.02) with the i-gel the fastest intubation conduit (mean (SD) intubation time i-gel 18.5(6.8)s, intubating laryngeal mask airway = 24.1(11.2)s, classic laryngeal mask airway = 31.4(32.5)s, p=0.02). We conclude that the aScope performs well in simulated fibreoptic intubation and (if adapted for untimed use) would be a useful training tool for both simulated fibreoptic intubation and conduit-assisted intubation. The choice of manikin and conduit are also important in the success of such training. This manikin study does not predict performance in humans and a clinical study is required.

Evaluation of a single-use intubating videoscope (Ambu aScopeTM) in three airway training manikins for oral intubation, nasal intubation and intubation via three supraglottic airway devices
Anaesthesia. 2011 Apr;66(4):293-9

Remifentanil for awake intubation

Awake fibreopic intubation (AFOI) is indicated in a subgroup of critically ill patients in whom RSI is contraindicated due to a predicted difficult airway, and in whom time pressures do not mandate a more immediate route to the airway. Last night I intubated a patient with a swollen tongue using this technique, under remifentanil sedation. It was interesting to subsequently see that this month’s Anaesthesia contains an article on ‘remi’ for AFOI:

Remifentanil is increasingly being used as the primary agent to provide sedation during awake fibreoptic nasal intubation. In this observational study, we aimed to determine the optimal effect site concentration of remifentanil, using a target controlled infusion based on the Minto pharmacological model, to provide optimal safe intubation conditions without the use of other sedatives/premedication and/or spray-as-you-go local anaesthesia. Twenty patients with anticipated difficult airway participated in the study. Good intubating conditions were achieved in all patients with mean (SD) effect site concentration of 6.3 (3.87) ng.ml(-1) of remifentanil recorded at nasal endoscopy and 8.06 (3.52) ng.ml(-1) during tracheal intubation. No serious adverse event occurred during any of these procedures. These preliminary findings suggest that this is a feasible and safe technique for awake fibreoptic nasal intubation.

Remifentanil as single agent to facilitate awake fibreoptic intubation in the absence of premedication
Anaesthesia. 2011 May;66(5):368-72

Those of us not familiar with target controlled infusions might find a dose in micrograms per kilo more helpful. This paper from Analgesia and Anesthesia provides a useful guide, comparing relatively high and low doses of loading and maintenance doses:

Awake nasotracheal fiberoptic intubation requires an anesthetic management that provides sufficient patient comfort, adequate intubating conditions, and stable hemodynamics. Short-acting and easily titratable analgesics are excellent choices for this maneuver. In this study, our aim was to determine an appropriate dosage regimen of remifentanil for awake nasotracheal fiberoptic intubation. For that reason, we compared two different dosage regimens. Twenty-four patients were randomly assigned to receive remifentanil 0.75 micro g/kg in bolus, followed by a continuous infusion of 0.075 micro g x kg(-1) x min(-1) (Group L), or remifentanil 1.5 micro g/kg in bolus, followed by a continuous infusion of 0.15 micro g x kg(-1) x min(-1) (Group H). All patients were premedicated with midazolam 0.05 mg/kg IV and glycopyrrolate 0.2 mg IV. Both dosage regimens ensured patient comfort and sedation. Discomfort did not differ between groups. Patients in Group H were sedated more profoundly. Hemodynamic stability was maintained with both remifentanil doses. Intubating conditions were adequate in all patients and comparable between the groups. The large dosage regimen did not result in any additional benefit compared with the small dosage. For awake nasotracheal fiberoptic intubation, we therefore recommend remifentanil 0.75 micro g/kg in bolus followed by continuous infusion of 0.075 micro g x kg(-1) x min(-1), supplemented with midazolam 0.05 mg/kg

Awake nasotracheal fiberoptic intubation: patient comfort, intubating conditions, and hemodynamic stability during conscious sedation with remifentanil
Anesth Analg. 2003 Sep;97(3):904-8 (Free Full Text)

 

An alternative to bolus + maintenance is using an incremental infusion rate via an infusion pump. In a comparision with midazolam and fentanyl, remifentanil was given to 37 patients in incremental dosages (0.1-0.25-0.5 microg/kg/min) by an infusion pump according to comfort, level of sedation and respiratory depression. Nasotracheal intubation was better tolerated in the remifentanil group, who also showed better suppression of haemodynamic effects of intubation.

BACKGROUND: Awake fiberoptic intubation is the standard of care for difficult airway management. Quality and success of this technique depend on the experience of the intubating physician and the proper preparation of the patient. The aim of this study was to compare remifentanil (R) as single agent to the combination of fentanyl (F) and midazolam (M), which have been the drugs for analgesia and sedation for this procedure.

METHODS: Seventy-four adult patients requiring nasotracheal intubation were randomly assigned to one of two groups. In group I, (n=37) R was administered in incremental dosages (0.1-0.25-0.5 microg/kg/min) by an infusion pump according to comfort, level of sedation and respiratory depression. In group II, (n=37) analgesia and sedation was achieved by F 1.5 microg/kg and doses of between 1 and 10 mg M, titrated to the individual needs. Patient reactions like grimacing, movement and coughing during intubation were assessed, as well as patient recall of the procedure. Haemodynamic and respiratory parameters were continuously recorded.

RESULTS: Group I patients better tolerated nasal tube passage (P<0.001) and laryngeal tube advancement (P<0.001) than group II. Remifentanil better suppressed hemodynamic response to nasal intubation (P<0.001). No significant difference in respiratory data was recorded. In group I more recall of the procedure was observed (six vs. zero patients, P<0.05).

CONCLUSION: Remifentanil in high doses, as the single agent for patient preparation for awake fiberoptic intubation seems to improve intubating conditions, quality and reliability of the procedure. However, a higher incidence of recall is to be expected.

Evaluation of remifentanil as single drug for awake fiberoptic intubation
Acta Anaesthesiol Scand. 2002 Apr;46(4):350-4

Some authors advocate dexmedetomidine for AFOI. Remifentanil was compared with dexmedetomidine in a randomised, double-blind trial. Remi was loaded and maintained at the ‘low’ dose as described in the second paper above and was associated with a higher intubation success rate on first attempt than dexmedetomidine (76% vs 38%):

Introduction: Dexmedetomidine (DEX), a centrally acting, selective alpha-2 agonist, with analgesic and sedation properties, has been successfully used for sedation in intensive care units. Remifentanil (REM), an ultra-short acting synthetic opioid, is often used to aid awake fiberoptic intubation (AFOI). As a narcotic, REM has a potential for respiratory depression, whereas DEX does not. This study compares the use of REM and DEX as adjuncts to local anesthetic preparation of the airway for AFOI.

Methods: Thirty adult ASA I-III patients with expected difficult airways were randomized to receive REM or DEX for sedation during AFOI. Operators and assessors were blinded to the drug used. Preoperatively, all patients received 2 mg midazolam intravenously and their airways were topicalized with 4% lidocaine. Patients in the REM group received a bolus of 0.75 mcg/kg over 10 minutes followed by an infusion of 0.075 mcg/kg/min. Patients in the DEX group received a bolus of 0.4 mcg/kg over 10 minutes followed by an infusion of 0.7 mcg/kg/hr. A word and picture set was presented to each patient before any drugs were administered, after loading of either sedative, and following extubation. Heart rate, blood pressure, respiratory rate, SpO2, bispectral (BIS) index level, and Ramsay sedation level (RSS) were recorded. Recall of each 3 sets of pictures and words was assessed at 30 minute intervals for a period of 3 hours after the completion of surgery.

Results: Patient demographics were similar between the 2 groups. All patients’ airways were successfully secured by fiberoptic intubation. Seventy-six percent of REM cases were intubated on the first attempt, as compared to 38% of the DEX cases (p=0.02). Intubation attempts were greater in the DEX group even after adjusting for confounders (OR unadjusted = 5.26, 95% C.I. = 1.19, 25.72; OR adjusted = 4.84, 3.43, 6.82). The DEX group had a higher mean oxygen saturation rate than REM (1.58 higher; 95% C.I. = 0.14, 3.03; p=0.03). Although the incidence of O2 saturation < 90% was greater in the REM group, it was not significant. No apneic episodes occurred and no rescue maneuvers, such as administration of reversal drugs or positive pressure ventilation, were required in either group. There was a lower Ramsey Sedation Scale (RSS) score (lower by = 0.45, 95% C.I. = 0.1142, 0.7792; p=0.008) in the DEX group compared to the REM group. A Kaplan Meier survival analysis showed that DEX patients took longer to attain a RSS of 3 despite reaching a lower RSS score. (Logrank test = 4.00 with one degree of freedom, p=0.0455) The DEX group also had 6.99 lower (95% C.I. = 1.19, 12.79; p=0.018) BIS score compared to the REM group. Generalized estimating equations (xtgee) showed no significance in the recall results with the exception of verbal recall in the DEX group after the initial bolus. Minimal hemodynamic instability was observed in both groups.

Discussion: Both Dex and REM can be safely used as sedative agents for AFOI. Despite increased sedation and lower recall after the initial bolus, the DEX group required more attempts at intubation. Nonetheless, lower oxygen saturation was observed in the REM group.

Dexmedetomidine vs. Remifentanil for Sedation in Awake Intubations-A Randomized, Double-Blind Trial
Anesthesiology 2008; 109 A14

Pre-hospital Airtraq use often failed

The Airtraq seems nifty when you try it on a manikin, but until now the question of whether it would be a useful pre-hospital tool was unanswered. This Austrian study provides helpful data:

OBJECTIVES: The optical Airtraq laryngoscope (Prodol Meditec, Vizcaya, Spain) has been shown to have advantages when compared with direct laryngoscopy in difficult airway patients. Furthermore, it has been suggested that it is easy to use and handle even for inexperienced advanced life support providers. As such, we sought to assess whether the Airtraq may be a reliable alternative to conventional intubation when used in the prehospital setting.

DESIGN, SETTING, AND PATIENTS: Prospective, randomized control trial in emergency patients requiring endotracheal intubation provided by anesthesiologists or emergency physicians responding with an emergency medical service helicopter or ground unit associated with the Department of Anesthesiology, General Hospital, Wiener Neustadt, Austria.

MEASUREMENTS AND MAIN RESULTS: During the 18-month study period, 212 patients were enrolled. When the Airtraq was used as first-line airway device (n=106) vs. direct laryngoscopy (n=106), success rate was 47% vs. 99%, respectively (p<.001). Reasons for failed Airtraq intubation were related to the fiber-optic characteristic of this device (i.e., impaired sight due to blood and vomitus, n=11) or to assumed handling problems (i.e., cuff damage, tube misplacement, or inappropriate visualization of the glottis, n=24). In 54 of 56 patients where Airtraq intubation failed, direct laryngoscopy was successful on the first attempt; in the remaining two and in one additional case of failed direct laryngoscopy, the airway was finally secured employing the Fastrach laryngeal mask. There was no correlation between success rates and body mass index, age, indication for airway management, emergency medical service unit, or experience of the physicians.

CONCLUSIONS: Based on these results, the use of the Airtraq laryngoscope as a primary airway device cannot be recommended in the prehospital setting without significant clinical experience obtained in the operation room. We conclude that the clinical learning process of the Airtraq laryngoscope is much longer than reported in the anesthesia literature.

Use of the Airtraq laryngoscope for emergency intubation in the prehospital setting: A randomized control trial
Crit Care Med. 2011 Mar;39(3):489-93

Easy on the ELM

A first report of thyroid cartilage fracture resulting from laryngoscopy and intubation has been published. An elective surgery patient underwent paralysis with 60 mg rocuronium after which ‘laryngoscopy and intubation attempts with a Macintosh 3 blade, Miller 2 blade, stylet, and vigorous external laryngeal manipulation yielded only Cormack Lehane grade 3 views of the larynx‘. Intubation was eventually achieved with a Glidescope, but it was noted that ‘external laryngeal manipulation was applied as forcefully as the assistant could perform the maneuver‘.

The author suggests the fracture could either have resulted from the external laryngeal manipulation during laryngoscopy or from the rigid curved stylet used with the Glidescope. Whichever it was, their take home advice is sound:

Even during difficult laryngoscopies, gentle manipulations are best

I would add to this – do the ELM yourself – in other words, bimanual laryngoscopy.

Laryngoscopy Complicated by Thyroid Cartilage Fracture
Anesthesiology. 2010 Oct;113(4):993-4

Pull that tongue

A way of improving glottic visualisation when attempting fibreoptic intubation is for an assistant to perform a jaw thrust manoeuvre. This is nicely demonstrated in a video on the New England Journal website. However my retrieval medicine colleague and anaesthetist Dr Anthony Lewis pointed out the following situation and its solution:

What if they are a ‘difficult airway’ and you the jaw can’t move? Get your Magills forceps, grab the tongue and pull the tongue out. Very nice!