Diagnosis

Respiratory alkalosis

Etiology

Cause [lvk][psg][ufq][6qw]

• Hyperventilation

  • CNS: Head injury, stroke, anxiety, pain, fear, stress, drugs

  • Toxicity (Salicylate, Theophylline)

  • Pulmonary: Hypoxemia --> tachypnea (asthma, COPD, pulmonary embolism, pneumothorax, pneumonia)

  • Iatrogenic: hyperventilation during mechanical ventilation or ECMO

  • Anemia

  • Fever

  • Hyperthyroidism

  • Pregnancy

Pathophysiology [psg][ufq][6qw]

1. The primary pH buffer system in the human body: HCO3/CO2 equilibrium

   H+ + HCO3- <--> H2CO3 <--> CO2 + H2O

2. HCO3 is the alkalotic substance and CO2 is the acidic substance

3. CO2 is regulated by the pulmonary system through respiration, whereas the HCO3 is regulated through the renal system with bicarbonate reabsorption

4. Chronic process if metabolic compensation

5. Increase in alveolar ventilation that is disproportionate to the rate of metabolic carbon dioxide production --> decreased PaCO2

6. Loss of carbon dioxide --> shift of equilibrium if given time

7. Metabolic compensation over the course of days:

   • Consumption of bicarbonate --> alkalosis (pH > 7.45)

   • Renal decrease of H secretion and increasing HCO3 secretion

Epidemiology

Incidence per 100.000 [lvk]

Approach

• Blood test: Complete blood count, liver function, thyroid function, b-HCG, theophylline and salicylate levels

• Blood gas: Low HCO3 in chronic respiratory alkalosis

• Cultures of blood, sputum, urine, and other sites

• Chest x-ray

• Chest CT

• Ventilation perfusion scanning

• MRI Caput

Treatment

1. Treat the underlying disorder [lvk]

   • Anxiety: Reassurance, rebreathing into a paper bag, treatment for underlying psychological stress, beta-adrenergic blockers, anxiolytics

   • Pain: Sedation and pain control

   • Mechanically ventilated patients: Decrease the tidal volume and/or respiratory rate

   • Pneumonia: Antibiotics

   • Pulmonary embolism: Anticoagulation

Differential diagnoses

Acute respiratory distress syndrome, Anxiety, Asthma, Atrial fibrillation, Clostridium tetani, COPD, Drug side effects, Elevated intracranial pressure, Head trauma, Heart failure, Heatstroke, Hyperkalemia, Hyperphosphatemia, Hyperthyroidism, Hyperventilation, Hypocalcemia, Hypocapnia, Hypokalemia, Hypomagnesemia, Hypoparathyroidism, Meningitis, Metabolic acidosis, Metabolic alkalosis, Milk-alkali syndrome, Myocardial infarction, Pleural effusion, Pneumonia, Pneumothorax, Pregnancy, Pulmonary edema, Pulmonary embolism, Pulmonary fibrosis, Sepsis, Thyrotoxicosis