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Emergency: requires immediate attention
Respiratory acidosis
Other Resources UpToDate PubMed
Emergency: requires immediate attention

Respiratory acidosis

Contributors: Scott Echternacht, Christine Osborne MD, Mary Anne Morgan MD, Michael W. Winter MD
Other Resources UpToDate PubMed

Synopsis

Respiratory acidosis is a condition that raises the serum partial pressure of carbon dioxide (pCO2 > 45) and lowers the serum pH (< 7.35). Presentation varies based on the acuity of onset as well as on the underlying cause.
  • Typical symptoms associated with a rapid increase in pCO2 include anxiety, dyspnea, confusion, hallucination, and psychosis; this can progress to coma.
  • A more gradual increase, as is seen with chronic respiratory acidosis, may cause memory impairment, sleep disturbances, personality changes, daytime somnolence, coordination impairment, tremors, myoclonic jerks, or asterixis.
Causes of respiratory acidosis include:
  • Decreased central respiratory drive (eg, sedative overdose, encephalitis, stroke, sleep apnea, obesity hypoventilation, hypothermia, starvation)
  • Decreased respiratory, neuromuscular, or thoracic cage function (eg, primary spinal cord / lower motor neuron / muscle disorders, thoracic cage disorders, metabolic disorders, toxins / poisoning / drugs)
  • Increased alveolar dead space
  • Increased carbon dioxide production (eg, fever, thyrotoxicosis, sepsis, steroids, overfeeding, exercise) – Unless a patient has limited pulmonary reserve, this will rarely result in clinically important hypercapnia.
  • Upper airway disorders (eg, epiglottitis, foreign body aspiration, obstructive goiter) – These are rare causes of hypercapnia.
Respiratory acidosis can occur as an acute or a chronic process. Depending on the acuity of the condition, the body will compensate in different ways.
  • Acute respiratory acidosis – Acute hypercapnia typically follows sudden obstruction of the airway or generalized bronchospasm. The acute compensatory response for respiratory acidosis is an increase in the serum bicarbonate concentration by 1 mEq/L for every 10 mm Hg elevation in pCO2.
  • Chronic respiratory acidosis – Chronic hypercapnia (defined as respiratory acidosis persisting after 3-5 days) occurs in end-stage COPD, restrictive lung disease with ventilatory muscle fatigue, or advanced states of intrapulmonary and extrapulmonary restrictive lung disease. With chronic acidosis, the kidneys increase acid excretion, allowing for generation of additional HCO3, and the renal tubule increases HCO3 reabsorption, a process that takes 3-5 days to complete. The chronic response leads to a 4 mEq/L increase in the serum bicarbonate concentration per 10 mm Hg elevation in pCO2.

Codes

ICD10CM:
E87.2 – Acidosis

SNOMEDCT:
12326000 – Respiratory acidosis

Look For

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

Common conditions associated with respiratory acidosis include:
It is important to differentiate a respiratory acidosis from a metabolic acidosis. The best method for doing this is to review the HCO3- concentration (decreased in metabolic acidosis) and the pCO2 (increased in respiratory acidosis).

If a patient with a chronic respiratory acidosis presents with a moderate to severe acidemia, it is usually suggestive of a concurrent metabolic acidosis or superimposed acute respiratory acidosis. On the contrary, if a patient with a chronic respiratory acidosis presents with a pH ≥ 7.40, look for a concurrent metabolic alkalosis or acute respiratory alkalosis.

Best Tests

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Management Pearls

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Therapy

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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References

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Last Reviewed:02/05/2019
Last Updated:02/28/2019
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Emergency: requires immediate attention
Respiratory acidosis
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Respiratory acidosis : Headache, Anxiety, Delirium, Memory impairment, Sleep disturbance, Dyspnea, Tremor, Hypoventilation, Myoclonic jerks
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