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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 increase in PaCO2 that leads to decrease in pH.

  • Occurs when lungs fail to excrete carbon dioxide (CO2) including (Table 1):
    • Disorders that restrict ventilation or increase CO2 production
    • Airway and pulmonary abnormalities
    • Neuromuscular abnormalities
    • Mechanical ventilator problems

Table 1. Causes of Acute Respiratory Acidosis

  • Restricted breathing or increased CO2 production result in lower pH.
    • Acute respiratory acidosis with hypoxemia, hypercarbia, and acidosis is life-threatening.
    • Chronic respiratory acidosis seen with disorders that produce increase in PaCO2 and hypoxemia compatible with life (e.g., chronic obstructive pulmonary disease [COPD]; Table 2)
  • Compensatory response:
    • Chemical buffering occurs early
    • If prolonged respiratory acidosis (>12–24 hours), metabolic compensation occurs.
      • Serum HCO3 increases raising pH to normal by:
        • Proximal tubular HCO3 reabsorption
        • Ammoniagenesis
        • Distal tubular H+ secretion

  • Mechanical ventilation
  • COPD

  • Patient usually symptomatic.

Signs and Symptoms

  • Confusion
  • Difficulty thinking
  • Headache
  • Severe cases:
    • Central nervous system (CNS) symptoms include:
      • Altered mental status
      • Abnormal behavior
      • Seizures
      • Stupor
      • Coma
    • Increased cardiac output
    • Hypercapnia can mimic stroke or CNS tumor by producing:
      • Headache
      • Papilledema
      • Focal paresis
      • Abnormal reflexes

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 potassium may be modestly increased.
  • Arterial blood gases (ABG) measured to determine oxygenation and acid–base status.

  • Maintain patent airway and adequate oxygenation.

  • Treatment dependent on chronicity of condition.

  • Provide adequate ventilation if CO2 excretion acutely and severely impaired (Paco2 >80 mm Hg [>10.6 kPa]) or if life-threatening hypoxia present (arterial oxygen tension [Pao2] <40 mm Hg [<5.3 kPa]).
    • Ventilation established by:
      • Maintaining patent airway (e.g., emergency tracheostomy, bronchoscopy, or intubation)
      • Clearing excessive secretions
      • Administering ...

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