Skip to Main Content

++

SOURCE

++

Source: Devlin JW, Matzke GR. Acid–base disorders. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed, New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146062232. Accessed August 8, 2012.

++

DEFINITION

++

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

++

ETIOLOGY

++

  • Increases in neurochemical stimulation via central or peripheral mechanisms.

  • Physical increases in ventilation via voluntary or artificial means (eg, mechanical ventilation)

++

PATHOPHYSIOLOGY

++

  • 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).

++

RISK FACTORS

++

  • Mechanical ventilation.

++

CLINICAL PRESENTATION

++

  • Usually asymptomatic if condition is 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.

++

DIAGNOSIS

++
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.

++

DESIRED OUTCOMES

++

  • Correction of acid–base disorder.

++

TREATMENT: GENERAL APPROACH

++

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

++

TREATMENT: NONPHARMACOLOGIC THERAPY

++

  • Direct measures (eg, treatment of pain, hypovolemia, fever, infection, or salicylate overdose) can be effective.

  • Rebreathing device (eg, 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.

++

MONITORING

++

  • 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.

++

PROGNOSIS

++

  • Resolution of underlying disorder determines prognosis.

++

Date Written: January 1, 2017

++

Contributor: Laura Baumgartner, PharmD, BCPS, BCCCP

++

Editor: Lauren Roller, PharmD, BCCCP; Laura Baumgartner, PharmD, BCPS, BCCCP

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.