Updated: Nov 2, 2022
What if I told you that 2-4% of critically ill patients we intubate, primarily with poor hemodynamics and hypoxemia, will experience that dreaded cardiac arrest . That's as many as 1 in 25! 😱
What if I also told you that in patients WITHOUT poor hemodynamics and severe hypoxemia, as reported by the INTUBE Study, 45.2% will experience at least one major adverse peri-intubation event; which includes cardiovascular instability, hypoxemia, and cardiac arrest . Of those patients that experience adverse events, 42.6% experienced cardiovascular instability (defined by a SBP <65 mm Hg at least once, SBP <90 mm Hg for >30 minutes, new or increased need of vasopressors or fluid bolus >15 mL/kg), 9.3% experienced severe hypoxemia, and 3.1% experienced cardiac arrest.
Does it make you a little nervous as you think about your next RSI? It sure makes me nervous! 😬
Now, the numbers were obtained from various studies (in the ED and ICU) where several different approaches to intubation or RSI were used. This makes it difficult to track down what the common denominator is. But, independent risk factors have been identified to be the cause of these adverse events. While there is a laundry list of these independent risk factors, we can modify three of them, as clinicians, to decrease the risk of unwanted/adverse reactions. These three factors include:
Absence of pre-ox
I have previously written blogs on pre-oxygenation, so the focus for this blog will be factor #3, HYPOTENSION. The previous blogs on pre-oxygenation and how to pre-ox can be found HERE and HERE, respectively. I think it could go without saying that ALL patient's should be pre-oxygenated prior to intubation.
As clinicians, I find that we can mitigate the above statistics if we slow down to treat our patients appropriately. As the meme farmer says, "It ain't much, but it's honest work." And really, I don't think it is that "much" and I think it's the right thing to do for our patients. With the addition of a few interventions and some knowledge, we can prep our patients for the best possible outcome -- make it honest work.
For that prep, I would like to ask, then answer, the following questions:
"Who needs to be optimized?"
"What are the recommendations for optimizing our patients?"
Before we get into it, poor hemodynamics (hypotension) is the animal we will be tackling in this blog and, it isn't always a patient problem. Sometimes, the interventions we perform during the RSI exacerbates the pre-existing hypotension or unstable patient. The additive effects of hypovolemia, suppression of the sympathetic response through medication, and the transition to positive pressure ventilation do not assist with the patient's already poor hemodynamics. So as providers, we MUST be diligent and attempt to prevent cardiovascular collapse.
Who Needs "Optimized?"
Am I allowed to say, "everyone?!" 😋 While multiple studies report adverse events in the presence of hypotension (DUH!), even The INTUBE Study -- Adverse Peri-Intubation Events in the Critically Ill which excluded severely hypoxic patients and hypotension at the time of laryngoscopy, still had a high rate of adverse events. So, I feel as though it is safe to say that ALL patients would likely benefit from some form of "optimization" prior to intubation.
We do have to consider other factors than simply heart rate and blood pressure. Factors like age, BMI, co-morbidities, general medical history, the reason for intubation... and so on, should be considered as well. We have to utilize our critical thinking. Is there harm in assuming an adverse event will happen and preparing for the worst every time?
The patients at the highest risk of cardiovascular collapse or arrest include those with:
SBP < 90
MAP < 65
Any prior vasopressor administration
Shock index 0.9, or Higher
0.8, or higher, is the value utilized in the consensus recommendation used by the Society for Airway Management .
High shock index patients (SI of 0.9, or higher) exhibited blunted hypertensive responses and more frequent hypotension, with the administration of Ketamine as the induction agent .
Among hemodynamically stable patients undergoing emergency intubation, immediate pre-RSI shock index was the strongest predictor of post-intubation hypotension .
** According to Heffner et al, 2013; SI was independently associated with cardiac arrest with an optimized threshold approximating SI greater than or equal to 0.9, which is associated with adverse outcomes and the need for therapeutic intervention in other acute conditions. **
What are the recommendations for optimizing our patients?
The treatment for patients with physiologically difficult airways comes from many different sources and literature throughout the years. But of most recent, the Society for Airway Management has compounded a list of recommendations for the treatment of hypotension prior to airway management. There are what seems like a gamut of recommendations, which may seem a bit intimidating... But, the recommendations are also pretty intuitive, which makes them easier to recall and understand.
1. Patients should have intravenous access sufficient for rapid fluid administration before intubation.
Two or more IVs are suggested, typically.
2. Patients should be screened for high risk of hemodynamic collapse -- those with a shock index greater than or equal to 0.8 are at high risk.
The higher the shock index, the more likely adverse events are to occur; such as hypotension or cardiac arrest.
3. Hypotensive patients due to obstructive shock secondary to acute or acute-on-chronic RV failure should be managed using RV failure guidelines.
This one is for you POCUS nerds 🤓
4. Fluid-responsive and fluid tolerant patients should be fluid resuscitated before intubation, or at least during the intubation attempt.
Aggressive volume resuscitation.
Use appropriate fluids for resuscitation
Standard NS or LR
Bleeders get BLOOD 🩸
5. When possible, vasopressor infusions should be started before intubation in patients that are not volume responsive or fluid tolerant.
Norepinephrine is the preferred vasopressor .
6. When vasopressor infusions are not possible or impending arrest is anticipated, bolus-dose vasopressors should be available and used to maintain systemic pressure during and after the intubation, until an infusion can be started.
Epinephrine should be considered as the vasopressor of choice in patients with decreased myocardial function.
7. Hemodynamically neutral induction agents should be used
Ketamine or Etomidate
Reduction of the induction agent dose is reasonable in patients with a high shock index, but SHOULD NOT REPLACE ADEQUATE PRE-INTUBATION RESUSCITATION .
Although I use the term "hemodynamically neutral," be aware that ALL induction agents can cause hypotension; this includes Ketamine and Etomidate 😉
Always expect these agents to cause hypotension and proceed with caution ⚠️
Now, what is the resuscitation end goal? I don't mention how much fluid. I don't mention doses for the drips or the push-dose pressors. I don't mention much about the hemodynamically "neutral" induction agents. What the hell are you to do?! Is there a targeted blood pressure? Is there a targeted SI?
Fluids, pressors, and induction agent choices are something I'm saving for another blog, so keep those 👀 peeled.
I searched high and low for an answer, without luck. However, I will leave you with this bit of info I did find:
1. Per the Manual of Emergency Airway Management (Fifth Edition), "If the need for intubation is not immediate, then abnormal hemodynamic parameters should be normalized as much as possible prior to intubation."
2. Heffner et al, 2012, reports a study that "demonstrated pre-RSI systolic pressures less than 140 as independently associated with post-intubation hypotension, but SI was not included in this analysis" .
3. In hemorrhagic shock, the patients should be resuscitated with blood products to achieve a SBP above 100mmHg .
4. In a 2020 research article titled, Risk Factors for and Prediction of Post-Intubation Hypotension in Critically Ill Adults: A Multicenter Prospective Cohort Study, they report an increased risk of post-intubation hypotension once SBP fell below 130 mmHg. When a MAP was used rather than SBP, there was a threshold below 95 mmHg that was associated with post-intubation hypotension. Perhaps aiming for a higher perfusion pressure in the critically ill, either via MAP or SBP would prevent post-intubation hypotension and associated poor outcomes . They also report the typical, "this would need to be tested via a future interventional trial."
5. Of the studies I read regarding this topic, most report a high incidence and high likelihood of adverse events occurring at SBP < 90, MAP <65, or a shock index of 0.9 or higher.
Jared Patterson, CCP-C, One Rad Medic
Killin' It Since 1989
Just a QUICK word on the meaning of "difficult airway."
Patients are difficult or challenging to intubate for many different reasons. When the airway is anatomically difficult, it becomes easy to identify the reason for the adverse reaction -- the inability to place plastic in the trachea. But in the physiologic difficult airway, even when intubation is successful, the life-threatening complications are thought to be "unpreventable." Buuuuut, there is evidence out there that complications such as hypoxemia, hypotension, and cardiac arrest can be reduced with better pre-intubation optimization .
The term "difficult airway" is typically synonymous with an anatomically difficult airway, and I think most would agree. But in the present day (as of this blog), technological advancements such as video laryngoscopes have absolutely positively increased our ability to safely and appropriately manage patients with an anatomically difficult airway. Attention to the physiologic difficult airway should also be considered when we utilize the term "difficult airway,' as critically ill patients still have a high incidence of life-threatening complications, regardless of how anatomically difficult the airway is.
BOOM! 💥 (again)
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