Respiratory alkalosis resident survival guide

Respiratory alkalosis Resident Survival Guide Microchapters
Overview
Causes
Diagnosis
Treatment
Dos
Don'ts

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rinky Agnes Botleroo, M.B.B.S.
Synonyms and keywords: Approach to respiratory alkalosis, Respiratory alkalosis management, Respiratory alkalosis Workup

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 pCO₂and high pH (>7.40). Respiratory alkalosis occurs when a person breathes too quickly 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. This is due to non-bicarbonate 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:

• Sepsis (Cytokine mediated)

Common Causes

• Central Nervous System related causes:
  • Increased Intracranial Pressure
  • 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:
  • Pneumonia
  • Asthma
  • Pulmonary oedema
  • Pulmonary thromboembolism
• Extrinsic Causes(deliberate or iatrogenic):
  • Excessive minute ventilation during mechanical ventilation

Diagnosis

Shown below is an algorithm summarizing the diagnosis of Respiratory Alkalosis:

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 ❑ If they felt numbness or tingling sensation on peripheral parts of the body? Acral paresthesia due to reduced blood flow to the skin ❑ 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 seizures

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 ❑ Increased heart rate due to fever, anxiety ❑ Increased temperature due to infection or sepsis ❑ Tachypnea due to Arrhythmias, hypoxemia, pulmonary disease ❑ Orthostatic changes due to reduced plasma volume

Examination of respiratory system ❑ Inspiratory crackles if patient has pulmonary edema ❑ Inspiratory ronchi and crackles in patient with pulmonary fibrosis ❑ Tachypnea, pulmonary rub in Pulmonary embolism ❑ 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 Abdomen ❑ Ascites in liver disease ❑ Gravid uterus in pregnant women

Examination of the Extremities ❑ Cyanosis due to hypoxemia

Examination of Central Nervous System ❑ Tremor, paresthesias ❑ Muscle weakness Hypokalemia, hypophosphatemia ❑ 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 ❑ In acute respiratory alkalosis, serum [HCO3−] is around 20 mEq/L, because the secondary response to hypocapnia of 20 mmHg is a decrease of 4 mEq/L from normal [HCO3−] of 24 mEq/L ❑ Serum [HCO3−] from normal level of 24 mEq/L drops to 16 mEq/L in chronic respiratory alkalosis for the same hypocapnia of 20 mmHg.

Do Chest X-ray

Do blood cultures

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 ❑ Breathing into a paper or plastic bag ❑ Mild sedation ❑ Reassurance ❑ To view treatment of panic attack click here

If patient is Hypoxic

Treatment options ❑ Give O2

Respiratory Alkalosis

Salicylates overdose

Treatment options ❑ Urinary alkalinization ❑ Forced diuresis ❑ Dialysis

If patient has Hyperthyroidism

Treatment options ❑ β-Blockers ❑ Antithyroid medications ❑ To view treatment of hyperthyroidism click here

If patient has Asthma

Treatment options ❑ Bronchodilators ❑ Corticosteroids ❑ To view treatment of asthma click here

If patient has Pneumonia

Treatment options ❑ Antibiotics ❑ To view treatment of pneumonia click here

If patient has pulmonary oedema

Treatment options ❑ Diuretics ❑ Treatment and improvement in CHF ❑ To view treatment of pulmonary edema click here

If patient has pulmonary embolism

Treatment options ❑ Give O2 ❑ Anticoagulation ❑ To view treatment of pulmonary embolism click here

If patient has history of going to high altitude climbing

Treatment options ❑ Give O2 ❑ Acetazolamide ❑ To view treatment of altitude sickness click here

Mechanical ventilation

Treatment options ❑ Reduce ventilatory rate and tidal volume ❑ Increase dead space ❑ Mild sedation without skeletal muscle paralysis

Dos

• Patient may experience faster and deeper breathing, physician should provide reassurance and empathy which can help to get patient's breathing under control.
• Physicians should look for the underlying cause and its severity.
• A patient who suffers from regular respiratory alkalosis can seek help from a therapist and can learn breathing exercises, meditation, and regular exercise.

Don'ts

• Patients should not hesitate to seek help from professionals in case of recurrence of respiratory alkalosis.