Refractory Hypoxemia¶
Amelia Muhs
Background¶
- Inadequate arterial oxygenation despite high levels of inspired O2 or the development of barotrauma in mechanically ventilated pts
- Generally start to consider the interventions below if needing FiO2 >80%
- Differential:
- Worsening underlying primary process (e.g. progressive ARDS)
- PE
- Pneumothorax
- Fluid overload
- Ventilator-associated Pneumonia
- New ARDS
Evaluation¶
- Always get CXR STAT if pt has new or worsening O2 requirement
- ABG is frequently helpful as well
- Can use POCUS to check for lung sliding (pneumothorax) or RV enlargement/septal bowing/McConnell’s sign (RV strain in PE)
Initial management¶
- Remember – if at any point the pt is rapidly decompensating, you can always disconnect them from the vent and bag them until they recover/while calling for help
- Early consideration of ECMO consult in appropriate pts (discuss with MICU fellow)
- Optimize fluid status consider diuresis/dialysis if not making urine
- Consider higher PEEP strategy
- Increased PEEP higher mean airway pressure, generally improves
oxygenation especially with diffuse pulmonary pathologies
- Exceptions may include certain focal/shunt pathologies (e.g. dense lobar PNA)
- Worsening oxygenation may occur with overdistension of alveoli increase dead space ventilation; generally determined empirically at the bedside
- Titrate up slowly; generally do not exceed PEEP 18
- Limited by high plateau pressures/barotrauma, overdistension/dead space ventilation, decreased preload/venous return
-
ARDSnet FiO2/PEEP Tables: At VUMC we typically use the Lower PEEP table
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Other recruitment maneuvers
- Reposition pt – can try elevating HOB or positioning so “good lung” is down
- If concern for mucus plug, consider need for bronch
- If concern for significant atelectasis can try recruitment maneuvers with the vent including sustained inflation (setting expiratory pressure to ~30 for ~30 seconds) and PEEP titration (setting PEEP to 20-25 and decreasing by 2cm at a time) – call the fellow before attempting
Management Algorithm for Refractory Hypoxemia¶
- Inhaled vasodilators: Distribute preferentially to well-ventilated alveoli local vasodilation improved V/Q matching
- VUMC formulary preference: inhaled epoprostenol (aka Flolan)
- Alternatives: inhaled milrinone, inhaled nitric oxide
- Data suggest improved PaO2/FiO2; large RCT without evidence for mortality benefit
- Deep sedation (RASS -4 or -5)
- Promotes ventilator synchrony
- Neuromuscular blockade (paralysis) – call your fellow before doing
this
- Rationale: maximal vent synchrony (eliminates residual chest wall/diaphragm tone)
- Pt MUST be RASS -5 (need analgesia + sedation)
- Trial one time IV push of vecuronium 0.1 mg/kg
- If improved vent synchrony/oxygenation, consider cisatracurium (Nimbex) drip
- Data are mixed ACURASYS 2010 (improved 90-day mortality but underpowered likely overestimating benefit); ROSE 2019 (no difference in 90-day mortality)
- Prone positioning (Need attending approval)
- Pts with moderate to severe ARDS (PaO2/FiO2 ratio \< 150)
- At VUMC, we use regular ICU beds and manually flip pts; cycle prone 16 hrs/supine 8 hrs
- When proning or supining a pt, always have a provider who can intubate in the room in case unplanned extubation occurs
- Considerations: need a team of people to reposition, high risk of ET tube malposition, difficult to access lines/perform procedures, high risk of pressure injuries
- Data: PROSEVA 2013 proning improved 28-day mortality; study complicated by imbalances between groups
- Alternative ventilator modes (usually Pressure Control or APRV/BiLevel/BiVent)
- APRV/BiVent should be avoided in people with bad obstructive lung disease, hemodynamic instability, refractory hypercarbia
- Venovenous (V-V) ECMO
- Indications for hypoxemia:
- PaO2/FiO2 \< 50 with FiO2 >80% for >3 hrs OR
- PaO2/FiO2 \< 80 with FiO2 >80% for >6 hrs AND
- Mechanical ventilation ≤ 1 week
- Absolute Contraindications:
- Poor short-term prognosis (e.g. metastatic cancer)
- Irreversible, devastating neurologic pathology
- Chronic respiratory insufficiency without the possibility for transplant
- Can calculate RESP score predicts in-hospital survival with ECMO
- CONSULT EARLY if a pt may be a candidate; allows ECMO team to assist with evaluation
- Data:
- CESAR 2009: improved 6-month survival without severe disability
- EOLIA 2018 : no mortality benefit but 28% crossover from control to ECMO arm dilutes potential effects
- Indications for hypoxemia:
Last update:
2022-06-02 13:28:55