Hypoxemia
Differential Diagnosis
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Low FiO2:
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Oxygen failure or pipeline crossover of gases
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Hypoventilation:
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Low TV or RR
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Ventilator dyssynchrony
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Circuit leak
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Obstructed ETT
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V/Q mismatch or shunt:
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Airway:
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Bronchospasm
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Mainstem intubation
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Mucous plug
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Alveolar:
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Pulmonary edema
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Aspiration
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Atelectasis
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Pleura:
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Pneumothorax
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Pleural effusion
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Deadspace:
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Pulmonary embolism
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Low cardiac output state
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↑ metabolic O2 demand:
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Malignant hyperthermia, thyrotoxicosis, sepsis, hyperthermia, neuroleptic malignant syndrome
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Diffusion abnormality:
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Chronic lung disease
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Artifacts:
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Confirm by ABG
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Poor waveform (probe malposition, cold extremity, light interference, cautery)
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Dyes (methylene blue, indigo carmine, blue nail polish)
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Management
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↑ FiO2 to 100%, high flow
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Check gas analyzer to rule out low FiO2 or high N2O
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Check other vitals, cycle NIBP, check peak inspiratory pressure, feel for pulse
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Check ETCO2 (?extubated/disconnected/low BP)
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Hand ventilate (check compliance, rule out leaks & machine factors)
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Listen for breath sounds
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Check position of ETT
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Soft suction via ETT (to clear secretions & check for obstructions)
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Consider code cart if severe
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Depending on likely diagnosis, consider:
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Large recruitment breaths, consider PEEP
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Bronchodilators
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Additional neuromuscular blockade
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↑ FRC (head up, desufflate abdomen)
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Fiberoptic scope to rule out mainstem intubation or ETT obstruction
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ABG, CXR
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Consider terminating surgery for refractory hypoxemia
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Plan for post-op care
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