Respiratory alkalosis
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Resident Survival Guide |
| Respiratory alkalosis | |
| ICD-10 | E87.3 |
|---|---|
| ICD-9 | 276.3 |
| DiseasesDB | 406 |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Priyamvada Singh, M.D. [2]Madhu Sigdel M.B.B.S.[3]
Overview
Respiratory alkalosis results from increased alveolar respiration (hyperventilation) leading to decreased plasma carbon dioxide concentration. This leads to decreased hydrogen ion and bicarbonate concentrations.
Pathophysiology
Compensation in respiratory alkalosis
Acute compensatory stage
- Starts within minutes to hours
- Mediated through the plasma buffer
- For every pCO2 decrease of 10, serum bicarbonate decreases by 2
- Change in pH is unpredictable
Chronic compensatory stage
- Renal mediated
- Starts within 1-3 days
- For every pCO2 decrease of 10, serum bicarbonate decreases by 5
- Change in pH is unpredictable
Classification
There are two types of respiratory alkalosis: chronic and acute.
Acute respiratory alkalosis
- Increased levels of carbon dioxide are "blown off" by the lungs, which are hyperventilating.
- During acute respiratory alkalosis, the person may lose consciousness where the rate of ventilation will resume to normal.
Chronic respiratory alkalosis
- For every 10 mM drop in pCO2 in blood, there is a corresponding 5 mM of bicarbonate ion drop.
- The drop of 5 mM of bicarbonate ion is a compensation effect which reduces the alkalosis effect of the drop in pCO2 in blood. This is termed metabolic compensation.
Causes
Lung and airways
Central respiratory drive
- Pain
- Anxiety
- Fever
- High altitude
- CNS tumor
- Drugs like doxapram and large doses of aspirin (stimulate the respiratory center), Gallium nitrate
- CNS causes, including stroke, subarachnoid haemorrhage, meningitis
- Caffeine overdose and coffee abuse
Systemic diseases
- Sepsis
- Salicylates
- Liver failure
- Hyperthyroid
- Pregnancy
- Hypotension
- CHF
- Anxiety, hysteria, and stress
- Iatrogenically during mechanical ventilation of patients
Special considerations
- Sepsis or salicylate toxicity are the only single disorders that cause both an elevated anion gap metabolic acidosis and a respiratory alkalosis.
- Ischemia, infection or infarction of the central respiratory centers may result either respiratory acidosis (decreased respiratory drive) or respiratory alkalosis (increased respiratory drive)
- Asthma, and Pneumonia can also present with either repiratory alkalosis or acidosis. Asthma typically presents with a respiratory alkalosis, however as the patient tires, respiratory acidosis may occur.
- Pulmonary embolus can be a life threatening condition and often presents as respiratory alkalosis.
- Progesterone is sometimes used as a respiratory stimulant in obstructive sleep apnea and hypoventilation.
Symptoms
- Symptoms of respiratory alkalosis are related to the decreased blood carbon dioxide levels, and include peripheral paraesthesiae.
- In addition, the alkalosis may disrupt calcium ion balance, and cause the symptoms of hypocalcaemia (such as tetany) with no fall in total serum calcium levels.