Tag Archives: airway

All Updates, ICU, PHARM, Resus

Needle crike: low rate and allow exhalation

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Two dedicated devices for transtracheal oxygen delivery through a cricothyroidotomy needle are available, the ENK Oxygen Flow Modulator (ENK) and the Manujet. Both maintain oxygenation, but the ENK is thought to achieve better ventilation (as previously shown in a pig model) because of a continuous flow that provides CO2 washout between insufflations. Very little is known concerning the lung pressures generated with these 2 devices, so a study using a simulated trachea and artificial lung model sought to determine oxygen flow, tidal volumes, and airway pressures at different occlusion rates and during both simulated partial and complete upper airway obstruction.

Manujet

Gas flow and tidal volume were 3 times greater with the Manujet than the ENK (approximately 37 vs 14 L/min and 700 vs 250 mL, respectively) and were not dependent on the respiratory rate. In the absence of ventilation, the ENK delivered a 0.6+/-0.1 L/min constant gas flow. In the totally occluded airway, lung pressures increased to 136 cm H2O after 3 insufflations with the Manujet, whereas the ENK, which has a pressure release vent, generated acceptable pressures at a low respiratory rate (4 breaths/min) (peak pressure at 27.7 +/-0.7 and end-expiratory pressure at 18.8+/- 3.8 cm H2O). When used at a respiratory rate of 12 breaths/min, the ENK generated higher pressures (peak pressure at 95.9 +/- 21.2 and end-expiratory pressure at 51.4+/- 21.4 cm H2O). In the partially occluded airway, lung pressures were significantly greater with the Manujet compared with the ENK, and pressures increased with the respiratory rate with both devices. Finally, the gas flow and tidal volume generated by the Manujet varied proportionally with the driving pressure.
The authors asset that this study confirms:

  • the absolute necessity of allowing gas exhalation between 2 insufflations and
  • maintaining low respiratory rates during transtracheal oxygenation.

In the case of total airway obstruction, the ENK may be less deleterious because it has a pressure release vent. Using a Manujet at lower driving pressures may decrease the risk of barotrauma and allow the safe use of higher respiratory rates

ENK

Oxygen delivery during transtracheal oxygenation: a comparison of two manual devices
Anesth Analg. 2010 Oct;111(4):922-4

All Updates, ICU, PHARM, Resus

LMA to stoma ventilation

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Level 1 evidence is great, but for useful tips that can add options to your resuscitation toolbox there are some great finds in journal letters pages.
Try this one: An apneoic patient requires assisted ventilation in your resuscitation room. Bag-mask ventilation is ineffective. You then notice a mature tracheostomy at the same time that you’re told he had a laryngectomy. How would you ventilate him?
The obvious answer is to intubate the stoma with a size 6.0 tracheal tube or a tracheostomy tube if you have one. However prior to that you could bag-‘mask’ ventilate with a size 2 laryngeal mask airway applied to the stoma, holding the cuff in place with pressure through an index finger.

Such a technique is desribed in the context of an elective anaesthesia case in this month’s Anaesthesia. The LMA cuff provided an effective seal around the stoma, thereby allowing leak-free ventilation.
Stoma ventilation using a paediatric facemask is another option.

Tracheostomy ventilation using a laryngeal mask as a ‘bridge to extubation’
Anaesthesia 2010;65(12):1232–1233

All Updates, ICU, Resus

Left molar approach

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The left molar approach is a technique to improve the view at laryngoscopy using a standard macintosh laryngoscope. It was described by Yamamoto1 as follows:

  • insert the blade from the left corner of the mouth at a point above the left molars;
  • the tip of the blade is directed posteromedially along the groove between the tongue and the tonsil until the epiglottis and glottis come into sight;
  • before elevating the epiglottis, the tip of the blade is kept in the midline of the vallecula and the blade is kept above the left molars;
  • the view provided is framed by the flange, the lingual surface of the blade, and the tongue bulged to right of the blade.


The success of this approach in comparison with alternatives has been reproduced by others2. However although Yamamoto and others demonstrated that this improved the laryngoscopic view, actual intubation may still be difficult because of the limited access to the cords, in part caused by the bulging of the tongue.
Physicians from Turkey described a case3 of an unpredicted difficult airway to demonstrate that the use of the gum elastic bougie can facilitate intubation which had otherwise not been successful via the left molar approach.
The take home message for me is that if I have a grade IV view despite my usual first-pass success optimisation manoeuvres such as positioning, reducing or releasing cricoid pressure, and providing external laryngeal manipulation, it is worth trying the left molar approach in combination with a bougie to gain a view of the glottis and to pass the tube.
1. Left-molar Approach Improves the Laryngeal View in Patients with Difficult Laryngoscopy
Anesthesiology. 2000 Jan;92(1):70-4 Full Text
2. Comparative Study Of Molar Approaches Of Laryngoscopy Using Macintosh Versus Flexitip Blade
The Internet Journal of Anesthesiology 2007 : Volume 12 Number 1
3. The use of the left-molar approach for direct laryngoscopy combined with a gum-elastic bougie
European Journal of Emergency Medicine December 2010 ;17(6):355-356

All Updates, PHARM, Resus

LMA not always successful; needle crike fails often

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A meta-analysis of pre-hospital airway control techniques evaluated alternative techniques to tracheal intubation. The outcome was placement success; there were no data on effectiveness of ventilation or other clinical outcomes. Although limited by poor quality studies, there are some interesting findings.
The pooled placement success rates for Combitube and LMA, were similar but unimpressive, with nonphysician placement success rates of 83.0% and 82.7%, respectively. The authors point out that while these devices might offer potential advantages over conventional tracheal intubation in terms of reduced training requirements, or perhaps fewer or less severe complications, they should not be expected to provide higher airway management success rates than conventional tracheal intubation.

Low success rates for this 'rescue procedure'. Just get your scalpel...

They identified only four studies reporting the success rates of needle cricothyroidotomy (NC). Regardless of patient circumstances or clinician credentials, the NC success rate was ubiquitously low, ranging from 25.0% to 76.9%. The pooled results for the 18 surgical cricothyroidotomy (SC) studies produced substantially higher success rates, although the success rate for all nonphysician clinicians was still only 90.4%. The authors state: “EMS systems that choose to incorporate a percutaneous airway procedure into their airway management protocols should recognize that the success rate of SC far exceeds that of NC”.
A meta-analysis of prehospital airway control techniques part II: alternative airway devices and cricothyrotomy success rates
Prehosp Emerg Care. 2010 Oct-Dec;14(4):515-30

All Updates, ICU, Resus

Etomidate vs midazolam in sepsis

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Given that single-dose etomidate can cause measurable adrenal suppression, its use in patients with sepsis is controversial. A prospective, double-blind, randomised study of patients with suspected sepsis who were intubated in the ED randomised patients to receive either etomidate or midazolam before intubation. The primary outcome measure was hospital length of stay, and no difference was demonstrated. The study was not powered to detect a mortality difference.
This study is interesting as a provider of fuel for the ‘etomidate debate’, but still irrelevant to those of us who have abandoned etomidate in favour of ketamine as an induction agent for haemodynamically unstable patients. Personally I remain unconvinced of the existence of patients who can’t be safely intubated using the limited choice of thiopentone or ketamine.
A Comparison of the Effects of Etomidate and Midazolam on Hospital Length of Stay in Patients With Suspected Sepsis: A Prospective, Randomized Study
Annals Emergency Medicine 2010;56(5):481-9

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Rocuronium reusable after sugammadex

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Sugammadex currently has no role in my own emergency / critical care practice. However a helpful paper informs us that patients whose rocuronium-induced neuromuscular blockade had been reversed by sugammadex may be effectively re-paralysed by a second high dose (1.2 mg/kg) of rocuronium. Onset was slower and duration shorter if the second dose of rocuronium was given within 25 minutes of the sugammadex.

The study was done with sixteen volunteers and the initial dose of roc was only 0.6 mg/kg – less than that used for rapid sequence intubation by many emergency & critical care docs.
When repeat dose roc was given five minutes after sugammadex (n=6), mean (SD) onset time maximal block was 3.06 (0.97) min; range, 1.92–4.72 min. For repeat dose time points ≥25 min after sugammadex (n=5), mean onset was faster (1.73 min) than for repeat doses <25 min (3.09 min) after sugammadex. The duration of block ranged from 17.7 min (rocuronium 5 min after sugammadex) to 46 min (repeat dose at 45 min) with mean durations of 24.8 min for repeat dosing <25 min vs 38.2 min for repeat doses ≥25 min.
Repeat dosing of rocuronium 1.2 mg kg−1 after reversal of neuromuscular block by sugammadex 4.0 mg kg−1 in anaesthetized healthy volunteers: a modelling-based pilot study
Br J Anaesth. 2010 Oct;105(4):487-92

All Updates, ICU, PHARM, Resus, Trauma

Ketamine for HEMS intubation in Canada

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Ketamine was used by clinical staff from the The Shock Trauma Air Rescue Society (STARS) in Alberta to facilitate intubation in both the pre-hospital & in-hospital setting (with a neuromuscular blocker in only three quarters of cases). Changes in vital signs were small despite the severity of illness in the study population.

A prospective review of the use of ketamine to facilitate endotracheal intubation in the helicopter emergency medical services (HEMS) setting
Emerg Med J. 2010 Oct 6. [Epub ahead of print]

All Updates, PHARM, Resus, Trauma

Pre-hospital RSI by different specialties

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This aim of the study was to evaluate the tracheal intubation success rate of doctors drawn from different clinical specialities performing rapid sequence intubation (RSI) in the pre-hospital environment operating on the Warwickshire and Northamptonshire Air Ambulance. Over a 5-year period, RSI was performed in 200 cases (3.1/month).

Failure to intubate was declared if >2 successive attempts were required to achieve intubation or an ETT could not be placed correctly necessitating the use of an alternate airway. Successful intubation occurred in 194 cases, giving a failure rate of 3% (6 cases, 95% CI 0.6 to 5.3%). While no difference in failure rate was observed between emergency department (ED) staff and anaesthetists (2.73% (3/110, 95% CI 0 to 5.7%) vs 0% (0/55, 95% CI 0 to 0%); p=0.55), a significant difference was found when non-ED, non- anaesthetic staff (GP and surgical) were compared to anaesthetists (10.34% (3/29, 95% CI 0 to 21.4%) vs 0%; p=0.04). There was no significant difference associated with seniority of practitioner (p=0.65). The authors conclude that non-anaesthetic practitioners have a higher tracheal intubation failure rate during pre-hospital RSI, which may reflect a lack of training opportunities.
The small numbers of ‘failure’ rates, combined with the definition of failure in this study, make it hard to draw generalisations. Of note is that the paper lists the outcomes of the six patients who met the failed intubation definition, all of whom appear to have had their airway satisfactorily maintained by the RSI practitioner, three by eventual tracheal intubation, one by LMA, and two by surgical airway. More data are needed before whole specialties are judged on the performance of a small group of doctors.
Should non-anaesthetists perform pre-hospital rapid sequence induction? an observational study
Emerg Med J. 2010 Jul 26. [Epub ahead of print]

All Updates, ICU, PHARM, Resus, Trauma

EM trainee RSI experience

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A single centre observational study of rapid sequence intubation (RSI) was performed in a Scottish Emergency Department (ED) over four and a quarter years, followed by a postal survey of ED RSI operators.
There were 329 RSIs during the study period. RSI was performed by emergency physicians (both trained specialists and training grade, or ‘registrar’ doctors) in 288 (88%) patients. Complication rates were low and there were only two failed intubations requiring surgical airways (0.6%). ED registrars were the predominant RSI operator, with 206 patients (63%). ED consultants performed RSIs on 82 (25%) patients, anaesthetic registrars on 31 (9.4%) patients, and anaesthetic consultants on 8 (2.4%) patients. An ED consultant was present during every RSI performed and an anaesthetist was present during 72 (22%). The average number of ED registrars during this period of training was 8. This equates to each ED trainee performing approximately 26 ED RSIs (6.5 RSIs/year). On average, ED consultants performed 14 RSIs during this period (approx 3.5 RSIs/year). Of the 17 questionnaires, 12 were completed, in all of which cases the trainees were confident to perform RSI independently at the end of registrar training. Interestingly, 45 (14%) of the RSIs in the study were done in the pre-hospital environment by ED staff, two thirds of which were done by ED consultants.
Training and competency in rapid sequence intubation: the perspective from a Scottish teaching hospital emergency department
Emerg Med J. 2010 Sep 15. [Epub ahead of print]

All Updates, Kids, PHARM

Paediatric Tube Cuff Pressures

A paediatric critical care transport service encountered elevated tracheal tube cuff pressures (>30 cmH20) in 41% of 60 consecutive care studied, and over 60 cmH20 in 30%. This measurement was taken on arrival at the bedside, not in flight.
Cuffed tubes are good, but we need to keep an eye on the pressures.
This is in keeping with the results of an adult study previously blogged on this site.
Endotracheal Tube Cuff Pressures in Pediatric Patients Intubated Before Aeromedical Transport
Pediatr Emerg Care. 2010 May;26(5):361-3