Respiratory alkalosis resident survival guide
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rinky Agnes Botleroo, M.B.B.S.
Overview
The normal physiological pH of blood is 7.35 to 7.45. An increase above this range is known as alkalosis. Respiratory alkalosis is a state where the body’s pH is more than 7.45 secondary to some respiratory or pulmonary cause.Respiratory alkalosis is characterized by the presence of low pCO2 and high pH (>7.40). Respiratory alkalosis occurs when a person breathes too fast or too deep and carbon dioxide levels drop too low. This causes the pH of the blood to increase and become too alkaline. It is also known as the primary hypocapnia in which patients usually present with hyperventilation. The resultant alkalinization of body fluids is balanced by a decrease in serum [HCO3−]. Secondary hypocapnia should be differentiated from primary hypocapnia, as the former occurs in response to metabolic acidosis. When respiratory alkalosis develops, a decrease in serum [HCO3−] occurs within a few minutes as soon as possible. This is due to nonbicarbonate buffering as well as H+ release from tissues. This buffering from various sources persists for several hours, and the resultant acid-base disturbance is called acute respiratory alkalosis. During acute respiratory alkalosis, the H+ secretion in both proximal tubule and cortical collecting duct is suppressed. When alkalemia persists, renal compensation starts with a decrease in both H+ secretion and basolateral exit of HCO3− in the proximal tubule. This lowers more serum [HCO3−], due to which the pH is maintained close to normal. The complete renal compensation takes 2–3 days to occur, and when a new steady state is established, it is called chronic respiratory alkalosis.
Causes
Life Threatening Causes
Life-threatening causes of Respiratory Alkalosis include
Common Causes
- Central Nervous System related causes:[1]
- Increased Intracranial Pressure[2]
- Stroke
- Head injury
- CNS infection
- Intracranial hemorrhage
- Pontine tumors
- Anxiety Hyperventilation
- Voluntary Hyperventilation
- Sepsis(Cytokine mediated)
- Chronic Liver disease(Toxin mediated)
- Drugs(Salicylates, progesterone)
- Pain
- Hypoxemic causes: Hypoxic stimulation leads to hyperventilation.
- Pulmonary Causes:
- Extrinsic Causes(deliberate or iatrogenic):
- Excessive minute ventilation during mechanical ventilation
Diagnosis
Shown below is an algorithm summarizing the diagnosis of Respiratory Alkalosis:[3][4]
Patient with Acute Respiratory Alkalosis | |||||||||||||||||||||||||
Take complete history | |||||||||||||||||||||||||
Ask the following questions regarding CNS manifestations ❑If they felt dizzy or confused recently?
Light-headedness and Confusion due to reduced cerebral blood flow ❑Ask if they had experienced tremor of the hand when the wrist is extended, sometimes said to resemble a bird flapping its wings to check Asterexis ❑If there is any history of loss of consciousness ❑Ask about any event of seizues | |||||||||||||||||||||||||
Ask the following questions regarding Cardiovascular manifestations ❑Ask if they felt any chest discomfort or pain? Chest pain due to vasoconstriction❑If they felt their heart was racing? Ask about cardiac Arrythmia | |||||||||||||||||||||||||
Ask the following questions regarding Metabolic effects ❑Ask if they have experienced perioral tingling sensations ❑Tetany ❑Ask about any symptoms of mild hyponatremia, hypokalemia, and hypophosphatemia | |||||||||||||||||||||||||
Do complete physical examination | |||||||||||||||||||||||||
Vital signs ❑Decreased blood pressure(hypotension) due to hypoxemia ❑Orthostatic changes due to reduced plasma volume | |||||||||||||||||||||||||
Examination of respiratory system ❑Inspiratory crackles if patient has Pulmonary edema ❑Prolonged expiratory wheezing in patient with Asthma | |||||||||||||||||||||||||
Examination of Cardiovascular System ❑Irregular rhythm may be seen ❑palpable P2, right ventricular heave may be seen if patient has Pulmonary hypertension | |||||||||||||||||||||||||
Examination of Central Nervous System ❑Tremor, paresthesias ❑Chvostek’s and Trousseau’s signs due to Low ionized Ca2+ | |||||||||||||||||||||||||
Do following tests | |||||||||||||||||||||||||
Serum Chemistry ❑Persistent hyponatremia, hypokalemia, hypophosphatemia, and low ionized Ca2+❑Increased WBC if there is any infection ❑Decreased Hemoglobin if there is anemia ❑ Increased Hematocrit which is suggestive of exposure to high altitude ❑Abnormal liver function tests in liver disease ❑Increased T3 and T4 and low TSH in a patient of hyperthyroidism ❑Positive urine β-human chorionic hormone if patient is pregnant ❑When both respiratory alkalosis and high Anion gap metabolic acidosis are present—suspect salicylate intake | |||||||||||||||||||||||||
Do Arterial Blood Gas (ABG) ❑low pCO2, low serum [HCO3−], high pH | |||||||||||||||||||||||||
Do Chest X-ray | |||||||||||||||||||||||||
Treatment
- Respiratory alkalosis is not self-limiting.
- Correction of the primary disorder of the respiratory alkalosis is needed
Shown below is an algorithm summarizing the treatment of Respiratory Alkalosis:
If patient comes with Anxiety or hyperventilation syndromes | Treatment options ❑Rebreathing into a paper or plastic bag ❑mild sedation ❑Reassurance | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient is Hypoxic | Treatment options ❑Give O2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Respiratory Alkalosis | Salicylates overdose | Treatment options ❑Urinary alkalinization ❑Forced diuresis ❑Dialysis | |||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient has Hyperthyroidism | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient has Asthma | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient has Pneumonia | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient has Pulmonary oedema | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient has Pulmonary embolism | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
If patient has history of going to high altitude, climbing | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mechanical ventilation | Treatment options ❑Reduce Ventilatory rate and tidal volume | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Do's
- Patient may experience faster and deeper breathing, physician should provide reassurance and empathy which can help to get patient's breathing under control.[5]
- Physician should look for the underlying cause and it's severity.
- A patient who suffers from regular respiratory can seek help from a therapist and can learn breathing exercises, meditation, and regular exercise.[5]
Don'ts
- Patient should not hesitate to seek help from professionals in case of recurrence of respiratory alkalosis.
References
- ↑ "Respiratory Alkalosis - StatPearls - NCBI Bookshelf".
- ↑ Hopkins E, Sanvictores T, Sharma S. PMID 29939584. Missing or empty
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(help) - ↑ Hasan, Ashfaq (2009). "Respiratory Alkalosis": 207–212. doi:10.1007/978-1-84800-334-7_9.
- ↑ Reddi, Alluru S. (2018). "Respiratory Alkalosis": 441–448. doi:10.1007/978-3-319-60167-0_33.
- ↑ 5.0 5.1 "Respiratory Alkalosis: Symptoms, Treatments, and Prevention".