What is the diagnosis and treatment for a patient presenting with alkalosis, as indicated by an ABG pH of 7.46?

Respiratory Alkalosis

This patient has respiratory alkalosis, indicated by a pH of 7.46 (above the normal range of 7.35-7.40), and the primary treatment is to identify and correct the underlying cause of hyperventilation rather than administering any alkalinizing agents.

Diagnosis

The ABG pH of 7.46 confirms alkalosis. To distinguish respiratory from metabolic alkalosis, you need the PaCO2 and bicarbonate levels from the complete ABG panel 1, 2:

• Respiratory alkalosis: Low PaCO2 (primary disturbance) with compensatory decrease in bicarbonate
• Metabolic alkalosis: Elevated bicarbonate (primary disturbance) with compensatory increase in PaCO2

Pathophysiology of Respiratory Alkalosis

Respiratory alkalosis results from alveolar hyperventilation, which decreases PaCO2 and increases pH 1. This produces multiple metabolic abnormalities including:

• Shifts in potassium, phosphate, and calcium 1
• Development of mild lactic acidosis 1
• Altered renal ion handling 1

Cardiovascular effects include tachycardia, ventricular and atrial arrhythmias, and both ischemic and nonischemic chest pain 1. Pulmonary vasodilation occurs, and gastrointestinal perfusion, motility, and electrolyte handling are affected 1.

Common Etiologies to Investigate

Respiratory alkalosis may be related to pulmonary or extrapulmonary disorders 1:

Pulmonary causes:

• Pneumonia, pulmonary embolism, asthma exacerbation, interstitial lung disease
• Pneumothorax, pulmonary edema

Extrapulmonary causes:

• Hyperventilation syndrome (diagnosis of exclusion in emergency settings) 1
• Sepsis, liver failure, pregnancy
• Central nervous system disorders (stroke, meningitis, encephalitis)
• Anxiety, pain, fever
• Medications (salicylates, progesterone)
• High altitude

Treatment Algorithm

The best method of correcting respiratory alkalosis is to treat the underlying cause 1:

1. Identify the etiology through targeted history and examination:

   • Assess for dyspnea, chest pain, fever, neurological symptoms
   • Review medications and recent exposures
   • Evaluate for signs of sepsis or systemic illness

2. Address the specific cause:

   • Treat infection with appropriate antibiotics
   • Manage pain or anxiety
   • Correct hypoxemia if present
   • Treat underlying pulmonary or cardiac disease

3. For hyperventilation syndrome (after excluding organic causes):

   • Reassurance and breathing retraining
   • Address underlying anxiety or panic disorder

4. Therapeutic use: Respiratory alkalosis is intentionally induced for treatment of elevated intracranial pressure, but this is a specific clinical scenario requiring careful monitoring 1.

Critical Pitfall

Do NOT administer sodium bicarbonate or any alkalinizing agent for respiratory alkalosis—this would worsen the alkalemia 3, 4. Bicarbonate is only indicated for severe metabolic acidosis with specific criteria (pH <7.0-7.1), not for alkalosis of any type 3, 4.

Monitoring

If the alkalosis is severe or the patient is critically ill, monitor:

• Serial ABGs to assess response to treatment
• Electrolytes, particularly potassium, calcium, and phosphate 1
• Cardiac rhythm for arrhythmias 1