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Source: Devlin JW, Matzke GR. Acid–Base Disorders. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. Accessed August 8, 2012.

  • Acid–base disorder characterized by primary decrease in PaCO2 that leads to elevation in pH.

  • Increases in neurochemical stimulation via central or peripheral mechanisms
  • Physical increases in ventilation via voluntary or artificial means (e.g., mechanical ventilation)

  • Paco2 decreases when ventilatory CO2 excretion exceeds metabolic CO2 production, usually because of hyperventilation.
  • Compensation
    • Earliest compensatory response is to chemically buffer excess bicarbonate by releasing hydrogen ions from intracellular proteins, phosphates, and hemoglobin.
    • Kidneys increase bicarbonate elimination with prolonged respiratory alkalosis (>6 hours).

  • Mechanical ventilation

  • Usually asymptomatic if condition chronic and mild.

Signs and Symptoms

  • Decreased cerebral blood flow may result in:
    • Lightheadedness
    • Confusion
    • Decreased intellectual functioning
    • Syncope
    • Seizures
  • Nausea and vomiting can occur, probably due to cerebral hypoxia.
  • Cardiac arrhythmias
  • Hyperventilation

Means of Confirmation and Diagnosis

  • Primary tools for determining cause of acid–base disorders and designing therapy:
    • Blood gases
    • Serum electrolytes
    • Medical history
    • Clinical condition

Laboratory Tests

  • Metabolic panel
    • Serum chloride usually increased.
    • Serum potassium, phosphorus, and ionized calcium usually decreased.
  • Arterial blood gases (ABG) measured to determine oxygenation and acid–base status.

  • Correction of acid–base disorder

  • Treatment often unnecessary because most patients have few symptoms and only mild pH alterations (i.e., pH <7.50).

  • Direct measures (e.g., treatment of pain, hypovolemia, fever, infection, or salicylate overdose) can be effective.
  • Rebreathing device (e.g., paper bag) can help control hyperventilation in patients with anxiety/hyperventilation syndrome.
  • Adjust ventilator if respiratory alkalosis associated with mechanical ventilation.
  • Initiate oxygen therapy with severe hypoxemia.

  • ABG measurements primary tools for evaluation of therapeutic outcome.
    • Monitor closely to ensure resolution of simple acid–base disorders without deterioration to mixed disorders due to compensatory mechanisms.
  • Monitor metabolic panel.

  • Resolution of underlying disorder determines prognosis.

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