A structured approach to preventing post-intubation hypotension

Post-intubation hypotension is one of the most common risks of intubation for critically ill patients. This lesson gives you a structured approach to plan your resuscitation and induction strategy, so you can keep your patient hemodynamically stable throughout the procedure.

In this lesson from our Advanced Airway Management course, you'll learn how to:

• Calculate and interpret the shock index to flag post-intubation hypotension risk
• Assess volume responsiveness and decide between fluids, vasopressors, or both
• Recognize how metabolic acidosis raises the risk of decompensation during intubation
• Choose induction agents based on a patient's hemodynamic risk
• Manage right ventricular strain from positive pressure ventilation after intubation
   

Preventing post-intubation hypotension

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Post-intubation hypotension, or even cardiac arrest, is a real danger for critically ill patients undergoing any procedure, especially endotracheal intubation. Understanding the patient's overall condition, including their blood pressure, heart rate, and other factors, is key to preventing complications. 

Considerations for your resuscitation plan

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When creating a resuscitation plan that involves intubation, it is important to consider hypotension, as well as several other important factors such as shock index, volume status and volume responsiveness, acidosis, anticipated response to decreased preload, and increased right ventricular afterload. Let's discuss these additional items one at a time, starting with the shock index. 

Using the shock index to assess risks of intubation

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Shock index is calculated by dividing the heart rate by the systolic blood pressure. A normal shock index is between 0.5 and 0.7, which indicates the system is running smoothly. But if the index rises above 0.8, there is a significant risk of post-intubation hypotension.

Assessing volume responsiveness before intubation

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Assessing volume responsiveness helps us to determine which patients require fluids or blood products. Repleting any absolute or relative volume loss is an important early step in resuscitation, because some hypotensive patients will need only volume, some are already volume overloaded, and others will require both volume and vasopressors to offset vasodilatation. The exact approach towards assessing volume responsiveness will depend on the clinical scenario and resources available to you.

Managing volume to keep patients hemodynamically stable throughout intubation

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A common approach in shock management is to deliver volume if required, followed by vasopressors if there is not an adequate response in blood pressure or cardiac output. In addition to increasing blood pressure by constricting blood vessels, vasopressors also increase cardiac output by strengthening the heart's contractions, which is referred to as increasing cardiac inotropy. This step is crucial, because most induction agents used for intubation, as well as positive pressure ventilation itself, decrease preload, so make sure to address volume responsiveness and ensure euvolemia before you start.

Understanding the risks of intubation in metabolic acidosis

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Acidosis creates a very challenging problem for intubation. Metabolic acidosis, with significant respiratory compensation, increases metabolic demand, decreases cardiac contractility, and requires a high minute ventilation, meaning the breathing rate increases significantly. The act of paralyzing a patient to intubate them removes that respiratory compensation even briefly, and can push a sick patient over the edge to decompensation.

Addressing acidosis before, during, and after intubation

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It's vital to address acidosis as much as possible prior to intubation, and every effort should be made to complete the fastest possible intubation time. Using equipment like video laryngoscopy and having the most experienced operator available perform the procedure can reduce procedure time. After intubation, it's critical to set the ventilator so that the patient's minute ventilation, or MV, matches their body's needs to blow off carbon dioxide, which in turn maintains the blood pH within a normal range.

Anticipating decreased preload from induction agents

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Let's look at the next point: response to decreased preload. Induction agents are powerful sedatives used to induce and maintain general anesthesia as part of the intubation process. These agents can affect preload, the volume of blood returning to the heart. To some degree, they can cause vasoplegia, leading to dangerously low blood pressure due to excessive vasodilatation, or myocardial depression, where the heart doesn't pump as effectively.

Selecting induction agents for patients at risk of post-intubation hypotension

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So, in patients with poor hemodynamics, consider a dosage reduction or an alternative agent to offset these effects somewhat. For example, benzodiazepines and propofol create more vasodilatation than ketamine or etomidate, so the latter two agents might be better choices in patients at risk for hypotension.

Managing right ventricular afterload during intubation

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Lastly, consider the right ventricle, which is sensitive to overload and strain, especially as the afterload increases through increased pulmonary pressures. If you suspect issues like pulmonary embolism or pre-existing pulmonary hypertension, consider using norepinephrine to increase mean arterial pressure and ventricular contractility.

Post-intubation, use positive pressure sparingly in patients with right ventricular dysfunction to avoid straining the right ventricle further, because positive pressure further worsens afterload.