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. http://accesspharmacy.com/content.aspx?aid=7984321.
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 |Favorite Table|Download (.pdf)
Table 1. Causes of Acute
Drugs (anesthetics, opioids, sedatives)
Massive pulmonary embolism
Airway and pulmonary abnormalities
Airway obstruction: foreign body, laryngeal edema
Aspiration of vomitus
Chronic obstructive pulmonary disease
Severe pulmonary edema
Adult respiratory distress syndrome
Brainstem or cervical cord injury
Inadequate frequency or tidal volume settings
Large dead space
Total parenteral nutrition (increased
- 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
- If prolonged respiratory acidosis (>12–24 hours),
metabolic compensation occurs.
- Serum HCO3– increases
raising pH to normal by:
- Proximal tubular HCO3– reabsorption
- Distal tubular H+ secretion
- Mechanical ventilation
- Patient usually symptomatic.
- Difficulty thinking
- Severe cases:
- Central nervous system (CNS)
- Altered mental status
- Abnormal behavior
- Increased cardiac output
- Hypercapnia can mimic stroke or CNS tumor by producing:
- 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
- Metabolic panel
- Serum potassium may be
- 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]).
- Maintaining patent airway (e.g.,
emergency tracheostomy, bronchoscopy, or intubation)
- Clearing excessive secretions
- Administering oxygen...