POCUS for the Physiologically Difficult Airway

March 22, 2023

Written by Megan Hilbert

Spoon Feed
Through the use of point-of-care ultrasound (POCUS) Emergency Medicine providers can optimize and tailor pre-intubation resuscitation in critically ill patients. See algorithm below.

Why does this matter?
Critically ill patients in the ED very frequently have minimal physiologic reserve. Peri-intubation hemodynamic instability carries with it a higher risk of 28 day mortality. The INTUBE study has shown a 42.6% risk of cardiovascular instability, 9.3% risk of severe hypoxemia, and 3.1% risk of cardiac arrest risk during intubation. It is our job as Emergency Medicine providers to minimize these risks to the best of our abilities.

One size [resuscitation] doesn’t fit all
This narrative review article published in Airway Management within the anesthesia literature encourages use of POCUS for identifying etiologies of peri-intubation hemodynamic instability in the hopes of minimizing morbidity and mortality. They have proposed a potential algorithm (see image below) depending upon the leading hemodynamic concern.

In words:

• Hypotension – authors suggest completion of RUSH to guide selection of IV fluid versus early peripheral vasopressors.  Quick review of RUSH below.
• Hypoxemia – authors suggest completion of BLUE protocol to optimize preoxygenation strategy. Quick review of BLUE below.
• Aspiration risk – can consider estimation of gastric volume via measuring of gastric antral cross-sectional area. Larger area corresponding to an increased aspiration risk. This tends to be less of a concern in the ED as we complete RSI regardless. It can, however, guide if we decide to elevate the head of the bed.
• Anatomically-difficult airway – Ratio of pre-epiglottic space to  epiglottic-vocal cord length can be a predictor of Cormack-Lehane Grade. Identification of cricothyroid membrane (CTM) prepping for potential surgical airway.
• Post-intubation – Can consider confirmation of ET tube placement with suprasternal notch approach as well as evaluation of bilateral pleural sliding.

The clinical context should always guide how much, or little, you do – after all, we don’t want to delay definitive management. But if you can take a moment to pick up a probe and further optimize your hemodynamics, I would encourage you to do so. I would also highly encourage reading the full article to remind yourself of the specifics.

RUSH:

• Pump – evaluation of pericardial effusion, decreased LV contractility suggesting heart failure, RV dilation suggesting potential pulmonary embolus
• Tank – intravascular volume status via IVC, eFAST for identification of other source of hypovolemia
• Pipes – AAA, aortic dissection, DVT evaluation
• (can also remember HIMAP acronym – heart, IVC, Morrison’s pouch/eFAST, aorta, pulmonary/plus DVT)

BLUE protocol:

• “A” profile – anterior diffuse lung sliding with A-lines and no consolidation = nonparenchymal disease such as asthma/COPD. With consolidation = pneumonia or acute respiratory distress syndrome (ARDS)
• “B” profile – anterior, bilateral, symmetric B-lines associated with lung sliding = interstitial edema indicative of cardiogenic pulmonary edema (homogenous) or ARDS (non-homogenous). Unilateral B-pattern suggests pneumonia.
• “C” profile – anterior lung consolidation correlating with diagnosis of pneumonia or ARDS.

Source
Role of Point-of-Care Ultrasound in Emergency Airway Management Outside the Operating Room. Anesth Analg. 2023 Jan 24. doi: 10.1213/ANE.0000000000006371. Online ahead of print.