Management of refractory hypoxemia using recruitment maneuvers and rescue therapies. Frontiers. 2023 Flashcards
What are the hemodynamic effects of recruitment maneuvers and high PEEP?
- decreased RV and LV preload
- increased RV afterload
- increased pulmonary vascular resistance
> > decreased CO, hypotension, tachycardia
reported: arrhythmias
What are the complications from barotrauma?
- pneumothorax
- subcutaneous emphysema
- pneumomediastinum
\Which type of recruitment maneuver has less negative hemodynamic effects, sustained inflation or a stepwise approach?
sustained inflantion
What minimum level of PEEP should be implemented after recruitment maneuvers to keep the recruited alveoli open?
10-12 mm Hg
List contraindications for recruitment maneuver
- hemodynamic instability
- right sided heart failure
- intracranial hypertension
- pneumothorax
- barotrauma risk
- patients with focal lung disease
What are the benefits of neuromuscular blockade in mechanically ventilated patients?
improved synchrony results in:
* improved recruitment
* improved compliance
* improved gas exchange
* reduced biotrauma
What are the downsides of neuromuscular blockade in mechanically ventilated patients?
- loss of diaphragmatic tone –> atalectasis –> hypoxemia
- intensive care acquired weakness
- critical illness polyneuropathy
What are the proposed benefits of inhaled pulmonary vasodilators?
- reverse pulmonary hypoxic vasoconstriction
- support right ventricular function (indirectly) –> reduce pulmonary vascular resistance
Name 2 inhaled vasodilators
- nitric oxide
- prostaglandins
What are adverse effects of inhaled nitric oxide?
- methemoglobinemia
- kidney failure
- inhibition of platelet activity
- hypotension
What happens if inhaled vasodilators are stopped too abruptly?
severe rebound hypertension
epoprostenol: half dose every 2-4 hours considered safe
Describe APRV
Phases of high continuous airway pressure with short phases of intermittent pressure release
i.e., high I:E ratio
What are the different settings to control in APRV?
High-level pressure - set to the plateau pressure on conventional mode prior to APRV
High pressure time - 3-8 seconds, start at 4 sec - should be ~90% of the cycle time
Low-level pressure - set to 0 mm Hg
Low-pressure time - 0.2-0.8 seconds - set at 0.5 seconds initially
If PLow is set to 0 in APRV, why aren’t most alveoli collapsing?
The short release preiod permits only partial unloading - causes auto-PEEP
What is high frequency oscillatory ventilation
low tidal volume with high RR with high PEEP
Define “refractory hypoxemia”
PaO2 < 60 mm< 100
on:
* FiO2 of 0.8-1.0
* PEEP of 10-30 cm H2O
* plateau pressure > 30 cm H2O
What is the main common cause of death in patients with ARDS?
MODS
What entails “protective mechanical ventilation”?
low tidal volues - 4-8 mL/kg
low plateau pressure - up to 30-32 cm H2O
Define anatomic versus functional recruitment
anatomic recruitments is defined as the restoration of aeration as assessed by CT
functional recruitment is defined as the improvement in gas exchange
List criteria to determine lung recruitability
- Distribution of lung lesions –> focal (nonrecruitable) versus diffuse (recruitable)
- Predominant lesion type –> interstitial edema, compressive and congestive atelectasis (recruitable) versus complete alveolar filling (nonrecruitable)
- Timing of recruitment maneuver compared to onset of ARDS - unlikely to be beneficial with ARDS of more than 3-5 days
List methods to assess the effectiveness of recruitment maneuvers
- CT scans
- Pressure-volume curve
- Electrical impedance tomography
- Lung ultrasound
- Stress index
- Recruitment-to-inflation ratio
Describe the “stress index” in mechanical ventilation
Assessed on the pressure-time scalar in volume-controlled ventilation
linear line equals stress index of 1
stress index < 1 - downward concavity = recruitment
stress index > 1 - upward convacity = overdistention
