Physiologically Difficult Intubations

Written by: Samantha Stark, MD (NUEM ‘20) Edited by: Steve Chukwulebe, MD (NUEM ‘19) Expert Commentary by: Seth Trueger, MD, MPH

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It’s the first few minutes of your shift, and the paramedics roll by your workstation with your first patient, a young woman clutching an inhaler and breathing with every accessory muscle in her body. You direct them to your resuscitation room and they inform you that she has a history of asthma and is having an attack; she’s too exhausted from breathing to verify this, but it seems true. You quickly get her on BiPAP, which mildly improves her work of breathing, but as she becomes drowsy, you obtain a VBG showing a climbing CO2 of 45. You realize that it’s time to intubate this patient, and as you get set up, you collect your thoughts and quickly review everything you’ve heard about intubating asthmatics.

Obstructive Airway Disease

First, remember that asthma is an obstructive airway disease, meaning that there are two main processes to worry about during and after intubation:

• Auto PEEP

• Hypotension secondary to increased intrathoracic pressure from auto PEEP

*Note: auto PEEP is caused by breath stacking in a patient whose expiration is impaired (such as asthma or COPD) – the ventilator initiates a breath before there’s time for full exhalation, and this leads to progressively more volume retained in the lungs, increasing the risk of barotrauma. This can also lead to increased intrathoracic pressure, in turn decreasing preload to the heart and thus causing hypotension.

How to optimize the intubation:

• As you already have this patient on BiPAP, try to preoxygenate as much as possible with this mode of positive pressure

• Consider attempting delayed sequence intubation with ketamine

  • It will maintain the patient’s respiratory drive and may help with BiPAP synchrony and anxiolysis

  • It serves as a bronchodilator

• Use rocuronium for paralysis

  • It will last longer than succinylcholine, and initially help with vent synchrony

  • *Note: remember to fully sedate the patient after intubation, as they won’t tell us that they’re not sedated during their prolonged paralysis

• Decrease the dead space and resistance of your vent by using the largest endotracheal tube feasible

• Frequently reassess the ventilator to ensure that breath stacking is not occurring:

  • Low respiratory rate to allow for exhalation

  • Higher tidal volumes of 6-8 cc/kg IBW

  • Decreased I:E ratio (at least 1:3, may very well need to be longer)

You’ve successfully intubated this patient, and now the lab pages you to let you know that there is a patient in the waiting room with a bicarb of 9. When the patient is wheeled back, his marked tachypnea and work of breathing makes you think he may need to be intubated as well. But he’s so acidotic, and you’re sure you’ve hear something about intubating acidotic people…

Metabolic Acidosis

What you’ve heard is that if you intubate a severely acidotic patient, you’ve killed them. There are two reasons for this:

• It’s very difficult to keep up with their minute ventilation

• There is a transient increase in pCO2 with paralysis (this is normally inconsequential, but in the decompensating acidotic patient, can lead to cardiovascular collapse)

How to optimize the intubation:

• Optimize cardiovascular status as much as possible beforehand

• Bolus fluids

• Consider starting pressors pre-intubation, or having push-dose phenylephrine or epinephrine on hand during intubation

• Match the patient’s minute ventilation

• Ensure adequate pre-oxygenation, using NIPPV

• However, even if oxygenation is not an issue, BiPAP should be used to assess the minute ventilation the patient is maintaining on their own, to help determine what is needed post intubation

• Using delayed sequence technique with ketamine as the induction agent and a short acting paralytic like succinylcholine could theoretically help to avoid apnea as much as possible

• Once intubated, the patient’s pre-intubation minute ventilation (respiratory rate and tidal volume) MUST be matched on the ventilator

• Don’t be surprised to see higher tidal volumes of 8 cc/kg IBW

As you’re sitting down to catch up on notes, a nurse gets your attention to let you know that there is an altered, febrile, tachycardic patient with a pressure of 65/40 tucked away in a bed at the back of the ED that you should probably see right away. As it turns out, this patient needs to be intubated as well.

Shock

As mentioned above, increased intrathoracic pressure from PPV results in decreased venous return to the heart, leading to decreased preload. This obviously has the potential to be quite detrimental to a patient with shock.

How to optimize the intubation:

• Optimize cardiovascular status as much as possible beforehand

• Fluid resuscitation and vasopressors started prior to intubation

• Have push dose pressors available at the bedside should they be needed

• Induction agents:

  • Avoid propofol as it has a propensity to cause hypotension

  • Use etomidate or ketamine

  • Ketamine has been shown to be more hemodynamically stable than etomidate

  • Also, the body should prioritize cerebrovascular blood flow in shock, therefore if etomidate is used, consider decreasing the dose to minimize hemodynamic effects

At this point, you’re too tired to write any notes, so you decide to sit down and, given how your shift has been going so far, do some reading about patients that are dangerous to intubate or difficult to manage on the vent. The first topic you come across is pulmonary hypertension.

Pulmonary Hypertension

Mechanical ventilation is dangerous in these patients due to their inability to tolerate decreased preload, increased afterload, or really any alteration in their tenuous hemodynamics. Unfortunately, in patients with pulmonary hypertension but also systemic hypotension, IV fluids can over-distend the right ventricle and make things worse. There’s not a super reliable way to tell if these patients will be fluid responsive or not; most would suggest a small fluid bolus challenge to see how they respond. There may or may not be time for this prior to intubation, but if there is time, it’s probably worth a try.

How to optimize the intubation:

• Can consider pre-medication with fentanyl:

  • Thought to blunt the hypertensive response to laryngoscopy, similar to head-injured patients

  • In theory, this prevents increased afterload in the pulmonary vasculature

• Induction agent:

  • Consider etomidate

  • Theoretically should have less of an effect on preload than propofol

  • Additionally, less of an effect on afterload than ketamine

• Ventilator settings:

  • Closely monitor plateau pressures to keep them less than 30 cm H2O, to avoid drops in preload due to increased intrathoracic pressure

  • Consider placing an arterial line for frequent ABG checks

  • Both hypercapnia and hypoxia can cause vasoconstriction (increasing afterload in the pulmonary vasculature)

Two days later, while you’re following up on some of your prior patients, you note that the patient in septic shock that you intubated a couple of days ago now has ARDS, and it seems that the inpatient team is having some difficulty managing her on the vent.

ARDS

While this is an area of active research and there are different strategies and methods for helping to improve these patients’ oxygenation, the main thing to remember from the perspective of managing the ventilator is the lung protective strategy:

• Tidal volume 6 cc/kg IBW

• Plateau pressure less than 30 cm H2O

• Minimum PEEP of 5 cm H2O (and remember that these patients may often need significantly higher PEEP) 

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Expert Commentary

Thank you for this review of intubating sick patients - intubating complex physiology is arguably one of the most dangerous things we can do, but there are some straightforward, concrete steps we can take to do it as safely as possible.

For me, the first step is to consider every ED intubation potentially dangerous. Maximize resuscitation (IV fluids; pressors if needed, always ready) and optimize preoxygenation to provide the biggest possible safety net. It’s much more CBA than ABC.

Every patient we intubate in the ED has potential to crump: the sympatholysis from sedation will reduce endogenous catecholamines, and the switch to positive pressure ventilation impairs preload.

Every intubated patient needs post-intubation sedation. I generally default to a fentanyl drip and modify from there (eg add propofol if BP tolerates; add ketamine if not). Do not remove sedation for hypotension; do not use pain as a pressor. That is torture and it is bad. Sedate the patient adequately and if that means more resuscitation (fluid, blood, pressors, etc) then do that too. Do not torture patients to maintain BP.

The easiest tactic to ensure post-intubation sedation is to think of RSI as 3 medications: NMBA, induction agent, and post-intubation sedative. I should not be surprised that I will need post-intubation sedation shortly after intubation.

Perhaps the biggest lesson in ARDS management and prevention in recent years is that nearly everyone potentially benefits from lung protective ventilation, i.e. 6 ml/kg *ideal* body weight. I’ve changed my default tidal volume to 400-450ml (it was 550-600 when I was in med school). Otherwise, ventilation (minute ventilation, or CO2 management) is all about adjusting respiratory rate (my default is 16-18, not 12) as the patient’s height usually does not change in the ED.

Special situations: asthma patients don’t have a big enough tube to exhale properly. Pay special attention, make sure they have sufficient time to exhale (and they may the one group that may benefit from *not* being on 6 ml/kg IBW. Perhaps even more importantly, unlike many other situations, intubation does not fix asthma; it makes it even harder to manage, as even the largest ET tubes are, by definition, smaller than the patient’s natural airway. Maximize NIV and other management options (eg epinephrine) if at all possible.

Acidosis is tough and the key is maximizing ventilation before and after intubation. These patients may need absurd-seeming respiratory rates and regardless of how hypercarbic they are, acidosis does not make patients taller so there is no reason to adjust tidal volume.

Pulmonary hypertension is complex and scary. Prepare beforehand, and work with your intensivists and other relevant specialists.

The most important part of airway management is preparation – not just in the ED, but learning as much as I can beforehand.

Seth Trueger, MD, MPH

Assistant Professor of Emergency Medicine

Department of Emergency Medicine

Northwestern University expert commentator

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How To Cite This Post:

[Peer-Reviewed, Web Publication] Stark, S. Chukwulebe, S. (2020, Oct 5). Physiologically Difficult Intubations. [NUEM Blog. Expert Commentary by Trueger, S]. Retrieved from http://www.nuemblog.com/blog/physiologically-difficult-intubations

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References

1. Ebert TJ, Muzi M, Berens R. Sympathetic responses to induction of anesthesia in humans with propofol or etomidate. Anesthesiology. 1992;76:725-33.

2. Van Berkel MA, Exline MC, Cape KM, et al. Increased incidence of clinical hypotension with etomidate compared to ketamine for intubation in septic patients: a propensity matched analysis. Journal of Critical Care. 2017;38:209-214.

3. Dalabih M, Rischard F, Mosier JM. What’s new: the management of acute right ventricular decompensation of chronic pulmonary hypertension. Intensive Care Med. 2014;40(12):1930-3.

4. Hemmingsen C, Nielson PC, Odorico J. Ketamine in the treatment of bronchospasm during mechanical ventilation. Am J emerg Med. July 1994;12(4):417-420.

5. Eames WO, Rooke GA, Wu RS, Bishop MJ. Comparison of the effects of etomidate, propofol, and thiopental on respiratory resistance after tracheal intubation. Anesthesiology. June 1996;84(6):1307-11.

6. Gragossian A, Asp A, Hamilton R. High Risk Post Intubation Patients. www.emdocs.net/ high-risk-post-intubation-patients/ June 2017

7. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes fo acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342:1301-1308.

8. NIH NHLBI ARDS Clinical Network. Mechanical Ventilation Protocol Summary. www.ardsnet.org/files/ventilator_protocol_2008-07.pdf

9. Marino, Paul L. 2009. The Little ICU Book. Wolters Kluwer Health. Philadelphia, PA.

10. Arbo, John E. 2015. Decision Making in Emergency Critical Care: An Evidence-Based Handbook. Wolters Kluwer Health. Philadelphia, PA.

The Top NUEM Blog Posts of 2019

Edited by: Maury Hajjar, MD (NUEM PGY-2), Niki Patel, MD (NUEM PGY-2), Vytas Karalius, MD, (NUEM PGY-2), Justine Ko (NUEM PGY-3)  Expert commentary by:  Seth Trueger, MD

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Happy New Year, Everyone!

Let’s take a look back at the 2019 NUEM Blog!

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The Top Ten NUEM Blog Posts of 2019

10. REBOA

Recent grads Andew Cunningham, Bill Burns, and Trauma/EM doc Zaffer Qasim walk us through the ever-popular and sublimely named REBOA.

9. The Seriousness of Deliriousness

Thorough discussion of the important but easy to overlook issue of delirium in the ED by Nery Porras, recent grad and current neuro critical care fellow Katie Colton and geriatrician Lee Lindquist.

8. Pelvic Fractures

Justine Ko, Terese Whipple, and Matt Levine walk is through pelvic fractures and the important associated injuries.

7. Verbal Deescalation in the ED

Vidya Eswaran, Zach Schmitz, Abiye Ibiebele, NUEM-blog-founder Michael Macias, recent grad Arthur Moore, and John Bailitz review the complex but important topic of verbal deescalation in the ED.

6. Visual Guide to Splinting

Recent grad and current Stanford med ed fellow, recentish grad John Sarwarkand remote grad Matthew Pirotte provide a surprising amount of information in a small amount of words & images.

5. Post-Intubation Management

It’s easy to fall into the trap getting the tube & high-fiving and walking away; Andra Farcas, recent grad and current Air Force doc Paul Trinquero and recentish grad Andrew Pirotte walk is through the steps to post-intubation management.

4. Flexor Tenosynovitis

Thorough and concise review of flexor tenosynovitis by Kevin Dyer and recent grad Adnan Hussain, featuring expert commentary hand surgeon Avi Giladi (who also had the #4 post in 2018).

3. Tetracaine

Nice review by Jonathan Hung and recent grad and current med ed fellow Matt Klein of an Annals study showing a safe approach to tetracaine for corneal abrasions. Won’t solve the controversy but does include an expert commentary by @DGlaucomflecken

2. Intubation Positioning: Beyond the Sniffing Position

Unfortunately, optimal positioning is not always optimally executed in the ED; this post reviews both “standard” sniffing position and ramping, which, if nothing else, will help push us to better position our patients. Very nice work by recent grad and current neuro critical care fellow Katie Colton, and recent grad Charles Caffrey, and recentish grad Andrew Pirotte!

1. Unstable C-Spine Fractures

The top spot goes to a very nice succinct review by recent grads Sarah Sanders and Alison Marshall featuring beautiful images and a commentary by NLFH faculty Steve Hodges.

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 How to cite this post

[Peer-Reviewed, Web Publication]  Hajjar M, Patel N, Karalius V, Ko J, (2019, December 30 ). The Top NUEM Blog Posts of 2019.  [NUEM Blog. Expert Commentary by Trueger S ]. Retrieved from http://www.nuemblog.com/blog/top-ten-2019.

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Other posts you might enjoy…

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Post-Intubation Checklist

Written by: Andra Farcas, MD (NUEM PGY-2) Edited by: Paul Trinquero, MD (NUEM PGY-4) Expert commentary by: Andrew Pirotte, MD

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Developing a Post-Intubation Checklist

Multiple studies have shown checklists in medicine can be beneficial. They have been used to reduce rates of catheter-related blood stream infections and ventilator associated pneumonias and to improve team performance in various settings.  

In the ED setting, a peri-intubation checklist for trauma patients resulted in more use of rapid sequence intubation and a trend towards improvement in post-intubation sedation rates.[1] This checklist included meds for pre-intubation (pre-treatment, induction, paralytics) and information about which intubation device was used but had only one line for post-intubation medications and did not include other post-intubation safety measures.  

One of the few studies that we could find specifically focused on a post-intubation checklist was a MICU study by McConnell, et al. They looked at the proportion of patients who had an ABG drawn within 60 minutes of mechanical ventilation initiation, as well as rates of respiratory acidosis and acidemia. They found that after initiating a post-intubation checklist and timeout, the rates of ABGs increased, which led to earlier recognition of inappropriate ventilation settings.  

There are a lot of pre-intubation checklists available for public use. For example, a great podcast/blogpost by Scott Weingart on the topic was developed into a checklist by Jeffrey Siegler and Christ Huntley. Their versions can be found at https://emcrit.org/emcrit/post-intubation-package/.

Our goal was to design a checklist specifically for the post-intubation setting that could potentially be implemented in our emergency department. We took ideas from aforementioned studies and existing checklists, as well as personal experience. In addition to covering a broad array of post-intubation tasks, we wanted to focus especially on post-intubation sedation and initial vent settings. In regards to these important tasks, what we do in the ED matters. Not only are the first few hours a critical period in the course of illness, but there is significant downstream momentum associated with choices made in the Emergency Department.  

The SPICE trial showed a link between deep early sedation and prolonged ventilation and increased mortality.[6] Conversely, an analgesia only, no-sedation approach has been shown to reduce time on the ventilator.[7] Consequently, we advocate for an analgesia-first approach. Fentanyl is a commonly used opioid for this purpose because of its rapid onset and short half-life. An easy starting point is a 0.5 - 1mcg/kg fentanyl push, followed by a drip starting at 25mcg/hr and uptitrated by 25mcg every 15-30 minutes (concurrent with another bolus as needed to control pain).

If pain is under control and additional sedation is needed, there are many options. Propofol is commonly used and is easily titratable. Start with a bolus of 5 mcg/kg/min (for 5 min) and start the drip at 5 to 10 mcg/kg/min, increasing by 5-10mcg/kg/min intervals every 5 min as needed (usual range 5-50mcg/kg/min). In the case of hypotension precluding the use of propofol, consider ketamine. Try to avoid benzodiazepines as these have been shown to increase risk of delirium.

Similarly, the initial vent settings that we chose in the ED matter and they can affect duration of ventilation, ICU length of stay, hospital length of stay, and other patient-oriented outcomes.[2] Not all illnesses requiring intubation and mechanical ventilation are the same and consequently vent-settings are not a one size fits all selection. Try to tailor settings to the individual patient and illness and choose one of the following broad strategies[9]:

1. Lung Protective Strategy (ARDS, lung injury, default for most patients): goal is to minimize additional injury via volutrauma or barotrauma. Set the tidal volume at 6-8cc per kg (of ideal body weight). Soon after intubation, drop Fio2 to 30% and PEEP to 5cm then titrate according to ARDSNet strategy for goal oxygen saturation 88-95%.

2. Obstructive Strategy (asthma or COPD): goal is to minimize air trapping by maximizing expiration time. Hence, set a low rate (perhaps 10) which will minimize I:E ratio (perhaps 1:4). Tidal volume can be standard 8cc/kg. This strategy may require permissive hypercapnea.

3. Severe acidosis (DKA, severe sepsis, etc.): Goal is to mimic the pre-intubation minute ventilation. Set the respiratory rate to match pre-intubation rate (usually at least 25-30).

Below is our designed post-intubation checklist:

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Expert Commentary

This column highlights the need for optimized post-intubation management.  This process requires attention to detail and patient needs.  Effective management not only involves delivery of adequate analgesia and sedation, but also efficient titration of the ventilator.  Each of these aspects of post-intubation management can be multi-faceted and challenging.  To assist with these processes and to simplify tasks, a checklist can be of great value.

Checklists can help create a stepwise clinical approach and trigger timely delivery of individual tasks.  Checklists can also help prevent omission of vital steps.  A task as simple as a chest X-ray to confirm endotracheal tube placement and positioning can be overlooked in an emergent situation.  The checklist provided in the review provides a simple, direct pathway to assist with post-intubation management, and avoid task omission.  In addition, this checklist can help emphasize strategies in the post-intubation period.  For example, the use of an “analgesic first” pathway for patient comfort following intubation.

As stated in the blog post, evidence now suggests “analgesic first” pathways improve patient outcomes.  The clinician should strive to enhance analgesia prior to escalating sedation.  Sedation has its role in post-intubation management, but should be employed only if escalated analgesic efforts fail.  “Analgesic first” pathways decrease ICU length of stay, decrease complications, and improve outcomes.  In addition to managing patient comfort, the clinician must also focus on optimizing ventilation and oxygenation.

Successful ventilator management requires attention to detail and the clinical scenario.  Every patient has different ventilation and oxygenation needs.  In addition to frequently reevaluating the patient clinically, a common and effective strategy for optimizing a ventilated patient is use of frequent blood gas measurement.  Titration of ventilation and oxygenation can be aided greatly with serial blood gas monitoring.  The use of blood gas data can also guide the provider utilizing a specific ventilation strategy (eg Lung-protective strategy).  Common problems in early post-intubation management include excessive oxygen delivery and hypoventilation.  Both of these can be identified by blood gas sampling.  Once optimal ventilation and oxygenation is achieved, the clinician can proceed with further diagnostic and stabilization pathways.

 Within the airway community, much focus is placed on optimized laryngoscopy and endotracheal tube delivery, no desaturation during intubation, interesting new equipment, etc.  However, managing an airway does not conclude with delivery of the endotracheal tube.  All clinicians managing airways would benefit greatly from accompanying this enthusiasm for intubation with focused and detailed care (often supplemented by checklists) in the post-intubation period. 

Special thanks to Dr. Jordan Kaylor and Dr. Matthew Pirotte

Andrew Pirotte, MD

Department of Emergency Medicine, University of Kansas Hospital

Clinical Assistant Professor, University of Kansas Medical Center

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How To Cite This Post

[Peer-Reviewed, Web Publication] Farcas A, Trinquero P (2019, February 11). Post-Intubation Checklist [NUEM Blog. Expert Commentary by Pirotte A]. Retrieved from http://www.nuemblog.com/blog/post-intubation

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References

1. Conroy, M.J., Weingart, G.S., Carlson, J.N. Impact of checklists on peri-intubation care in ED trauma patients. American Journal of Emergency Medicine, 2014; 32:541-544.

2. Fuller, B.M., Ferguson, I.T., Mohr, N.M., Drewery, A.M., Palmer, C., Wessman, B.T. et al. Lung-Protective Ventilation Initiated in the Emergency Department (LOV-ED): A Quasi-Experimental, Before-After Trial. Annals of Emergency Medicine, 2017; 70(3):406-418.  

3. Guthrie, K., Rippey, J. Emergency Department Post-Intubation Checklist. Agency for Clinical Innovation, 2013. https://www.aci.health.nsw.gov.au/__data/assets/pdf_file/0003/273792/emergency-department-post-intubation-checklist-charles-gairdner.pdf. Accessed May 26, 2018.

4. McConnell, R.A., Kerlin, M.P., Schweickert, W.D., Ahmad, F., Patel, M.S., Fuchs, B.D. Using a Post-Intubation Checklist and Time Out to Expedite Mechanical Ventilation Monitoring: Observational study of a Quality Improvement Intervention. Respiratory Care, 2016; 61(7):902-912.

5. Nickson, C. Post-intubation care. Life In The Fast Lane, Jan 5 2013. https://lifeinthefastlane.com/ccc/post-intubation-care/. Accessed May 26, 2018.

6. Shehabi, Y., Bellomo, R., Reade, M., Bailey, M., Bass, F., Howe, B. et al. Early Intensive Care Sedation Predicts Long-Term Mortality in Ventilated Critically Ill Patients. American Journal of Respiratory and Critical Care Medicine, 2012; 186(8):724-731.

7. Strøm, T., Martinussen, T., Toft, P. A protocol of no sedation for critically ill patients receiving mechanical ventilation: a randomised trial. The Lancet, 2010; 375:475-480

8. Weingart, S. Podcast 84 – The Post-Intubation Package. EMCrit RACC, Oct 16 2012. https://emcrit.org/emcrit/post-intubation-package/. Accessed May 26, 2018.

9. Weingart, S. Managing Initial Mechanical Ventilation in the Emergency Department. Annals Of Emergency Medicine, 2016; 68(5):614-61