Critical Care, Critical Care Roadblock, Airway

Roadblock: Difficult Intubations

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Welcome to the second installment of the EMRA Critical Care Committee's Roadblock series - the resuscitationist's guide to overcoming the obstacles in the normal algorithm of critically ill patients. Through this series, we will ask the opinions of both EM and CCM fellows/attendings on their approaches to the most common obstacles encountered in a treatment algorithm. 

Difficult Intubations

In this series we focus on strategies to bypass the most common pitfalls in our treatment algorithm when faced with a difficult intubation. We all know the approach as well as the medications in our toolbox for a simple intubation in the ED, but what if a wrench is thrown in our pathway? What else do we need to consider to optimize an intubation in certain common scenarios we face in our resuscitation bay? We asked Dr. Colin Pesyna and Dr. Evan Leibner, current dual-trained faculty in EM and critical care medicine at The Mount Sinai Hospital how they approach some of the most common roadblocks when intubating a patient.

Q: How is your approach changing when intubating a patient in severe RV failure from a cause such as pulmonary HTN or a massive PE?

Dr. Pesyna: You need to be extremely careful when intubating patients with severe RV failure. You should not be intubating these patients unless you are absolutely sure you need to. To help in the decision-making process, you need to understand if the patient is presenting with an acute or chronic process. For a chronic process, it is important to get in touch with other specialists such as their pulmonologist to get an idea of what their baseline is. Many patients appear to be "sick" to us as providers in the emergency department but are often not too far from their baseline and can be medically managed without the need of an intubation.

Once you have made the decision to intubate, preparation is key. Consider placing a right-sided arterial line to monitor the patient's hemodynamics. At this point, you should also consider calling the ECMO team, as these patients can decompensate very rapidly. If your institution has it available, consider placing the patient on nitric oxide or another inhaled pulmonary vasodilator. I would also add a pure vasopressor such as vasopressin. I particularly like vasopressin because it will increase systemic vascular resistance but not necessarily in the pulmonary circuit since the pulmonary vasculature does not carry any vasopressin receptors. I also recommend initiating an inotropic agent such as epinephrine.

Now, as you are preparing to intubate, I want you to channel your inner part-anesthesiologist and titrate your dosing of medications to awareness over the course of a minute using a combination of fentanyl, midazolam, and etomidate. Once the patient has lost awareness, I will use rocuronium as my paralytic. Following intubation, it is very important to minimize PEEP as much as possible. Don't forget to continue using an inhaled pulmonary dilator through the ventilator.

Dr. Leibner: This is a very difficult case to intubate, primarily because patients with severe RV failure do not take the insult of positive pressure or hypotension very well.

As I am getting ready to intubate, I am optimizing the patient's current condition to maximize the chance of a successful intubation. I start by adding an inopressor such as epinephrine as my first agent, regardless of their current BP, to provide additional RV support. I will also initiate HFNC or BIPAP and provide the patient with inhaled nitric oxide with a dose of approximately 40ppm. I also will call the ECMO team early and have the team on standby in case the patient decompensates further. In addition to the above therapy, I will also give calcium for a positive inotropic effect before I intubate the patient.

My method of intubating these patients consists of using a low-dose induction agent such as ketamine/etomidate and a high-dose paralytic such as rocuronium. Once intubated, I will adjust the ventilator settings to decrease the tidal volume and PEEP as much as possible to prevent a complication of excessive positive pressure.

Q: How is your approach changing when intubating a patient with concern with critical aortic stenosis? 

Dr. Pesyna: When intubating a patient with severe aortic stenosis you need to remember that the patient has a fixed obstruction. They cannot effectively increase their stroke volume to compensate for a drop in systemic vascular resistance. Furthermore, tachycardia will paradoxically tend to induce a drop in cardiac output in these patients. Thus, hypotension and tachycardia must be avoided at all costs.

As with all of the cases with an anticipated complicated intubation, I strongly recommend placing an arterial line to be able to adequately monitor a patient's hemodynamics since these patients are highly prone to suffer from hemodynamic collapse. Phenylephrine and vasopressin are great agents to have on board. In particular, having a phenylephrine stick at bedside can be highly useful. With phenylephrine being a pure alpha-1 agonist, you are able to increase a patient's SVR without increasing their HR. In addition, it gives you the added benefit of a possible reflexive bradycardia side effect. Etomidate is a great hemodynamically stable induction agent that can be used. I would strongly recommend against the use of ketamine or epinephrine, which promote tachycardia.

Following intubation, I would ideally want to have the patient on minimal PEEP and tidal volume settings. Patients with critical stenosis are very preload dependent so you want to avoid excessive positive pressure ventilation.

Dr. Leibner: Intubating patients with critical aortic stenosis are one of the most difficult intubations you will have to do in the emergency department. Because of the fixed obstruction and their preload dependence, you have to be very mindful of their hemodynamics as they can decompensate very rapidly during intubation. Phenylephrine is the first-line pressor for these patients as mentioned above to help increase their SVR without causing a tachycardic response.

Regarding fluid resuscitation prior to intubation, you need to be very careful and consider the patient’s overall clinical status. You need to balance between the risk of optimizing preload vs vascular congestion. Using a bedside US can be very helpful to gain additional data points in terms of your fluid resuscitation.

During the intubation, I prefer using a low-dose stable induction agent such as etomidate while using a high-dose paralytic such as rocuronium.

Q: How is your approach changing when intubating a patient in anaphylactic shock and/or severe angioedema?

Dr. Pesyna: You need to think critically about these patients since they have an upper airway obstruction. Similarly to most complex intubations, you should not be intubating these patients unless you are absolutely sure you need to. You need to first maximize medical treatments to treat the anaphylaxis or angioedema before the intubation.

In patients with a pathologic airway, I will use a flexible fiberoptic bronchoscope to understand how deep the swelling is (tongue, epiglottis, etc.) and anticipate how difficult the intubation will be. If you need to intubate, I would consider an awake fiberoptic intubation through the nose or mouth with airway topicalization with 4% lidocaine. You can also choose to give a mild sedating agent while coaching the patient through the procedure.

If you are anticipating a very difficult airway, I would set up for a cricothyroidotomy at the same time to prepare yourself and the room well in case the patient decompensates further.

Dr. Leibner: This is a case example in which you may want to consider pulling the trigger and intubating earlier than sooner. If your institution has one, I would call for a difficult airway team to prepare for the intubation. I would perform an awake fiberoptic intubation and prepare for a surgical cricothyroidotomy at the same time.

I prepare for an awake fiberoptic intubation by first nebulizing several cc of 4% lidocaine into the patient. I also will give glycopyrrolate to dry out their secretions several minutes before I begin the intubation. Finally, I will spray Afrin® into the nose. To intubate, I will use a lot of lube at the end of the ETT tube. I generally will use an ETT sized below a 7.0. You can also use a sedative agent such as etomidate to help relax the patient as you are intubating.

If the patient is peri-code, I would highly consider preparing for a cricothyroidotomy, especially if you are anticipating a difficult airway based on the patient's anatomy.

Q: How is your approach changing when intubating a patient with concern for intracerebral hemorrhage?

Dr. Pesyna: A very important consideration you want to keep in the back of your mind when intubating these patients is their blood pressure. The act of intubating is very stimulating to the vallecula and can cause a temporary catecholamine surge and increase their blood pressure. I use fentanyl at a dose between 3-5 mcg/kg for pre-treatment. To make it easy, you can ask for 300 mcg of fentanyl. Fentanyl can take a few minutes to take effect so in terms of order of operations, it should be the first agent you push as you are preparing for the intubation. I like to use propofol as my induction agent.

Dr. Leibner: There is always a question when intubating these patients if they are suffering from a catastrophic ischemic vs. hemorrhagic stroke. My approach is slightly different for both of them. For patients I am more concerned about an ischemic stroke, I will tend to keep their blood pressures relatively stable and aim for the SBPs to range between the 160s-180s. Therefore, I will use etomidate/midazolam as my induction agent followed by rocuronium. For patients with a hemorrhagic stroke, you can be a little more aggressive in terms of their SBP goal and therefore I will use a combination of propofol/fentanyl followed by rocuronium to intubate. The enemy is hypoxia and hypotension because their recovery becomes much worse.

Q: How is your approach changing when intubating a patient with an undifferentiated shock? 

Dr. Pesyna: When intubating a patient with an undifferentiated shock, you need to change your dose of your induction and paralytic agent. I prefer decreasing your induction agent and doubling the paralytic dosing. In addition, to maximize a successful intubation, I would add pressors to help increase their SVR during induction. If there is time prior to intubation, I always prefer placing an arterial line to continually monitor the patient's hemodynamics.

Dr. Leibner: When intubating a patient with an undifferentiated shock you need to focus on how you can medically treat and resuscitate the patient. To the best of your ability, you need to understand why the patient is in shock and use all of the tools in your toolbox (pressors, broad-spectrum antibiotics, BIPAP/HFNC) before intubation. It is critical to use your bedside US to know the patient's ejection fraction, IVC, etc.

If you have maximized your medical therapy and are considering intubation, it may be worthwhile to place the patient on BIPAP and increase their FiO2 to pre-oxygenate them as long as they have a mental status. For patients who are in shock, I recommend half-dosing your induction agent and doubling your dose of rocuronium to maximize your chances of a successful intubation. I also push calcium in many cases to help with contractility during induction.

Q: How is your approach changing when intubating a patient with an undifferentiated metabolic acidosis?

Dr. Pesyna: You really want to avoid intubating these patients since it is one of the most common causes of peri-intubation arrest. You really need to medically treat their underlying pathology first. If you decide you do need to intubate these patients, my biggest recommendation is to continually ventilate the patient with a BVM through induction. Because patients who are in severe metabolic acidosis are probably already very tachypneic, any further CO2 retention can precipitate a cardiac arrest. Therefore, continually ventilating the patient through induction is a mainstay part of your approach.

Dr. Leibner: This may be a controversial topic, but for patients in severe metabolic acidosis requiring intubation, I tend to push several amps of bicarbonate prior to RSI. In addition, prior to intubation, I will place patients on BIPAP and increase their RR to help ventilate the patient prior to induction if they still have a mental status. I will also have Phenylephrine and Calcium at bedside to push if needed to aid with contractility and SVR.

Discussion

The approach to a difficult intubation is a form of art and is highly dependent on the patient's clinical picture. As emphasized by Dr. Pesyna and Dr. Leibner in their discussion, the most important decision in the process is deciding to intubate the patient. To the best of your ability, you need to understand the patient's pathology and hemodynamics and critically think if the patient actually needs to be intubated. Understanding the intricate relationship between a patient's hemodynamics, the medications administered during intubation, and the effects of positive pressure ventilation is crucial. This comprehension is essential as it can significantly influence the patient's overall outcomes.

Before attempting any challenging intubation, it is essential to ensure that you have the necessary space, resources, and assistance at bedside. First, if your institution has a difficult airway team, it is recommended that you activate them to have additional support at bedside especially if it is an anatomically difficult airway. In the absence of a dedicated difficult airway team, reach out to Anesthesia or another emergency department provider for assistance during the intubation. Secondly, prioritize optimizing the patient’s hemodynamics. Third, consider placing a right-sided arterial line, given these patients' heightened susceptibility to hemodynamic collapse during induction. Lastly, if there is a potential need for ECMO, activate or contact a transfer center as early in the resuscitation as possible.


Through this series, we hope you are a little better equipped to deal with an obstacle the next time you come across a difficult intubation in the ED. Stay tuned for the next series in which we tackle roadblocks associated with having goals of care conversations in the ED.

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