A 65-year-old woman with a history of severe COPD and coronary artery disease is intubated for severe acute respiratory distress syndrome (ARDS) in the setting of pneumonia. Despite ventilation with 6 mL/kg tidal volumes and neuromuscular blockade, PaO2 :FiO2 remains 85 on FiO2 100%. PEEP is increased from 5 to 10 cm H2O, and mean arterial pressure subsequently decreases from 65 to 45.
In what setting is increased PEEP least likely to improve oxygenation and hemodynamics?
Correct Answer: A
Recruitment maneuvers and higher levels of PEEP are thought to protect against atelectrauma caused by repeated opening and closing of alveolar units in patients with ARDS. Higher PEEP has been shown to improve oxygenation and is not associated with worsened barotrauma or new organ failure. Its benefits are most established in patients with moderate to severe ARDS, and one meta-analysis found there may be a mortality benefit to higher PEEP in patients with severe ARDS.
Increased PEEP can also be beneficial for congestive heart failure with reduced LV ejection fraction. It reduces preload to the right-sided heart and increases right-sided heart afterload by increasing pulmonary vascular resistance, therefore, decreasing LV preload and placing an overfilled heart on a more favorable portion of the Frank–Starling curve to maximize contractility. It also decreases LV afterload (and thereby LV work) by reducing transmural pressure, and thus improves cardiac output in patients with poor LV function. On the other hand, cardiac output can decrease in patients with at risk for right-sided heart failure, as in this patient. COPD can lead to pulmonary hypertension, which in turn can lead to reduction in RV function and cor pulmonale. The decrease in RV preload and increase in RV afterload caused by PEEP can exacerbate preexisting RV dysfunction. The permissive hypercapnia seen in standard ARDS ventilation can likewise worsen RV dysfunction.
A 67-year-old woman was intubated for ARDS in the setting of pneumonia with septic shock and received muscular paralysis with cisatracurium to improve ventilator synchrony over the first 24 hours of mechanical ventilation. Her mean arterial pressure remains >65 on norepinephrine 35 µg/min. Cisatracurium was discontinued 12 hours prior, and the ventilator has been weaned to pressure support mode. She receives a spontaneous breathing trial (SBT) for 30 minutes on CPAP 5 cm H2O and FiO2 0.4. At this setting she has an SpO2 92%, generates a tidal volume of 4 mL/kg, and respiratory rate 28 breaths/min, with no signs of respiratory distress.
What is the contraindication to extubation in the patient?
Correct Answer: D
Extubation is contraindicated in hemodynamically unstable patients, including those requiring ongoing significant vasopressor support to maintain normotension. The NHLBI ARDS Network protocol recommends conducting a daily SBT for patients with ARDS when:
If these criteria are met, an SBT can be conducted on a T-piece of trach collar with FiO2 <0.5 and PEEP <5 cm H2O. The patient can be assessed for tolerance of SBT for up to 120 minutes. Evidence of tolerance includes:
If the patient tolerates the SBT for 30 minutes, extubation should be considered. A 30 minute SBT is noninferior to a 120 minute trial, with no significant difference in percentage of patients extubated, percentage who remained extubated at 48 hours, reintubation rates, ICU mortality, and hospital mortality. For patients at high risk of extubation failure, extubation to noninvasive ventilation can significantly reduce ICU length of stay and mortality.
This patient satisfied the criteria to be extubated based on SBT. However, presence of high vasopressor support is considered a contraindication to SBT and extubation.
Two 24-year-old males are admitted to the ICU intubated after polytrauma status post motor vehicle collision. Over the first 24 hours of admission, Patient 1 develops hypoxemia with bilateral pulmonary opacities on chest radiograph and PaO2 :FiO2 110. Patient 2 remains intubated for persistent altered mental status, and then on hospital day 4, develops bilateral pulmonary infiltrates with PaO2 :FiO2 220. Compared to Patient 2, Patient 1’s clinical course likely includes:
Correct Answer: C
ARDS is a clinical syndrome with a plethora of etiologies; the heterogeneity of its causes and their pathophysiology is being increasingly recognized and studied. Patients who develop ARDS after trauma can be separated into two temporal phenotypes: (1) early, defined as onset of ARDS within the first 48 hours of presentation, and (2) late, defined as ARDS diagnosis after 48 hours. Early-onset ARDS in trauma is associated with increased severity of thoracic trauma, more severe early hypotension, and increased red blood cell transfusion during initial resuscitation, as compared to the late-onset phenotype. Inflammatory biomarkers associated with endothelial injury and regulation of alveolar-capillary barrier integrity are more elevated in the early-onset group. This suggests that the early-onset phenotype is characterized by a higher degree of hemorrhagic shock, with increased early vascular injury and disruption of the alveolar-capillary barrier. The late-onset phenotype, by contrast, is associated with progressive multiorgan system dysfunction and complications of prolonged mechanical ventilation, such as pneumonia. No significant difference in mortality has been found between the earlyand late-onset phenotypes, however.
© 2010-2030 Your Doctor - Dr.Khalil Al-Yousifi - Kuwait - Contact Us