Critical Care Medicine-Neurologic Disorders>>>>>Acute Respiratory Distress Syndrome
Question 4#

A 66-year-old woman with Haemophilus influenzae pneumonia is intubated on the floor for hypoxemic respiratory failure and transferred to the ICU. Chest radiograph demonstrates bilateral patchy infiltrates; ABG is:

Mechanical ventilation is titrated to tidal volumes 6 mL/kg with PEEP 8 cm H2O, and plateau pressures remain <30 cm H2O. The patient is paralyzed and sedated with no ventilator asynchrony noted.

What is the next best step?

A. Initiate venovenous ECMO
B. Prone the patient
C. Initiate inhaled nitric oxide
D. Esophageal pressure monitoring to titrate PEEP

Correct Answer is B

Comment:

Correct Answer: B

In patients with severe ARDS (defined as PaO2 :FiO2 <150 with an FiO2 of >60%, PEEP >5 cm H2O, and tidal volumes 6 mL/kg), changing from supine to the prone position is associated with decreased mortality. Best outcomes have been shown when performed early in the course (<48 hour), and in conjunction with neuromuscular blockade and tidal volume <6 mL/kg. It improves oxygenation and reduces the risk of ventilator-associated lung injury by homogenizing ventilation in the dependent and nondependent portions of lung, reducing ventral overdistension, and improving dorsal alveolar recruitment.

Contraindications to prone ventilation include patients with facial/neck trauma or spinal instability, patients with elevated ICP, recent sternotomy, large burns or lacerations over the ventral body area, massive hemoptysis, hemodynamic instability, or patients at high risk for needing CPR/defibrillation. Factors such as chest tubes, multiple lines, and large body habitus can require extensive coordination with the care team during turning but are not contraindications. Potential complications of the prone position include kinking or misplacement of the ETT, kinking of vascular access, temporary increase in oral or tracheal secretions that can occlude the ETT, facial pressure ulcers, facial edema, brachial plexus injury, and elevated intra-abdominal pressure, which can complicate enteral feeding. Venovenous ECMO can be used in patients with ARDS or other causes of reversible pulmonary failure who experience refractory severe hypoxemia (PaO2 :FiO2 <80) or hypercapnia (pH <7.20.) Early initiation has not been shown to have a mortality benefit in ARDS as compared to conventional low tidal volume ventilation strategies with standard supplementary maneuvers such as neuromuscular blockade, proning, and rescue ECMO. Inhaled nitric oxide transiently improves oxygenation in ARDS patients while therapy is maintained but has not been shown to improve mortality and is associated with acute renal injury. Esophageal pressure measurements can be used as a proxy for pleural pressure in patients with ARDS to titrate PEEP to maintain positive end-expiratory transpulmonary pressure, minimizing atelectotrauma and volutrauma, but has not been shown to have a mortality benefit.

References:

  1. Guérin C, Reignier J, Richard JC, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368:2159-2168.
  2. Koulouras V, Papathanakos G, Papathanasiou A, Nakos G. Efficacy of prone position in acute respiratory distress syndrome patients: a pathophysiology-based review. World J Crit Care Med. 2016;5(2):121-136.
  3. Scholten E, Beitler J, Prisk G, Malhotra A. Treatment of ARDS with prone positioning. Chest. 2017;151(1):215-224.