Management of Mixed Respiratory Alkalosis and Metabolic Acidosis with Severe Hypoxemia

Immediate Management

The American College of Physicians recommends immediate high-flow oxygen therapy targeting SpO2 94-98% via reservoir mask at 15 L/min, followed by urgent identification and treatment of the underlying cause, such as pulmonary embolism, sepsis, or acute respiratory distress syndrome, in patients with mixed respiratory alkalosis and metabolic acidosis with severe hypoxemia 1
The British Thoracic Society suggests that respiratory alkalosis is characterized by a pH 7.489 (elevated) with PaCO2 22.4 mmHg (severely low, indicating hyperventilation) 2

The American Thoracic Society recommends calculating anion gap: [Na+] - ([Cl-] + [HCO3-]) to assess metabolic acidosis, and if anion gap >12, consider lactic acidosis, ketoacidosis, renal failure, or toxins 2
The American College of Emergency Physicians suggests immediately evaluating for life-threatening causes, including pulmonary embolism, sepsis, acute respiratory distress syndrome, pneumonia, and acute coronary syndrome, in patients with severe hypoxemia and mixed acid-base disorder 1

The American College of Chest Physicians recommends anticoagulation or thrombolysis as indicated for pulmonary embolism, and antibiotics for pneumonia or infection, with first-line amoxicillin or tetracycline unless previously ineffective 1, 3
The National Institute for Health and Care Excellence suggests that bicarbonate administration is reserved for severe acidosis with pH <7.1 and base excess <-10, which is not met in this patient (pH 7.489, BE -4.8) 5

The American Thoracic Society recommends considering invasive mechanical ventilation if pH continues to fall despite treatment of underlying cause, rising lactate indicating worsening tissue perfusion, respiratory rate >30 breaths/min with signs of exhaustion, or altered mental status or inability to protect airway 2, 3
The Society of Critical Care Medicine suggests using low tidal volumes (6 mL/kg ideal body weight) to prevent barotrauma, maintaining plateau pressures <30 cmH2O, and considering prone positioning if FiO2 >0.60 is required 4

The American Association for Respiratory Care recommends repeat ABG in 30-60 minutes after initiating treatment to assess response, continuous pulse oximetry maintaining SpO2 94-98%, and monitoring respiratory rate, heart rate, and mental status closely 1, 3
The National Institute for Health and Care Excellence suggests serial lactate measurements to assess tissue perfusion, and if clinical deterioration occurs at any time, repeat blood gases immediately 2, 3