Intubated and Hypoxic

OVERVIEW

Refractory hypoxemia in the intubated patient is a worst-case scenario that requires a rational, stepwise approach. In this episode, host Peter Lorenz, MD, discusses ventilator management, patient positioning, bedside procedures, and adjunctive medications with Steven Haywood, MD, RRT.

DISCUSSION QUESTION

What is your algorithm when faced with refractory hypoxemia?

• Secure the airway, stabilize the hemodynamics
• Take a step back and ask: Why are they hypoxemic?
• Increase the FRC
  • Through positioning – raise the head of the bed
  • By increasing PEEP
    • Follow the ARDS net PEEP table
    • General rule: If FiO2 > 60%, start at a PEEP of 15
    • If PEEP is going to get to 25, switch to APRV
  • Don’t bother with advanced recruitment maneuvers
  • Be patient, alveolar recruitment takes time
• Continue to optimize patient factors
  • Deeply sedate
  • Consider paralysis
  • Consider proning, especially if ED time will be prolonged – involve the ICU early
• Be wary of transfusion unless absolutely indicated
• Consider supportive procedures such as draining effusions or bronchoscopy
• Optimize V/Q matching
  • Refine positioning; Bleeding in the lung -> good lung up. Unilateral lung disease -> good lung down
  • Trial inhaled vasodilators
    • Nitric oxide
    • Inhaled prostaglandins
    • Nitroglycerin can be considered in a pinch
      • Dose is ~5 mg in 15 minutes
      • Typical concentration is 100-500 ug/mL, which corresponds to 10-50mL ➜ will be difficult to nebulize this much!
    • If pressors are on, keep in mind that vasopressin will spare the pulmonary vasculature
    • ECMO
      • Get them involved early

TAKE-HOME POINTS

• Be patient and stay calm
• Make sure your equipment is all in order
• Utilize lung protective ventilation at all times
• Maximize FRC
• Optimize VQ Matching
• Ask for help early

References

1. Hunsicker O, Materne L, Bünger V, et al. Lower versus higher hemoglobin threshold for transfusion in ARDS patients with and without ECMO. Crit Care. 2020;24(1):697.
2. Juffermans NP, Aubron C, Duranteau J, et al. Transfusion in the mechanically ventilated patient. Intensive Care Med. 2020;46:2450–2457.
3. Zou X, Zhang H, Wu Y, et al. Physiologic Comparison of Airway Pressure Release Ventilation and Low Tidal Volume Ventilation in ARDS: A Randomized Controlled Trial, Chest. 2025;167(2):453-465.
4. Lim J, Litton E. Airway Pressure Release Ventilation in Adult Patients With Acute Hypoxemic Respiratory Failure: A Systematic Review and Meta-Analysis. Crit Care Med. 2019;47(12):1794-1799.
5. Qadir N, Sahetya S, Munshi L, et al, for the American Thoracic Society Assembly on Critical Care. An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline. Am J Respir Crit Care Med. 2024;209(1):24-36.
6. Pulsipher AM, Pratt EH, Brucker A, Green C, Bonadonna D, Rackley C. Hemoglobin transfusion thresholds in patients on VV-ECMO for ARDS. Am J Respir Crit Care Med. 2021;203:A2673.
7. Farkas J. Nebulized glycerin: The stealth pulmonary vasodilator hiding under your nose? EMCrit’s PulmCrit. Dec. 21, 2019.
8. Gelmann D. Critical Care Roadblock: Refractory Hypoxemia on the Ventilator. EM Resident. Nov. 5, 2024.