Respiratory Alkalosis

Acid-Base Physiology


Definitions

Alkalemia

  • Definition: increased arterial pH
  • Note: patient can be alkalemic without having a respiratory alkalosis
    • Example: metabolic alkalosis can produce alkalemia without the presence of a respiratory alkalosis

Respiratory Alkalosis

  • Definition: disorder that results in decreased pCO2 with associated increased pH
  • Note: patient can have a respiratory alkalosis without being alkalemic
    • Example: a respiratory alkalosis may induce metabolic compensation (with a decrease in serum bicarbonate) without significant alkalemia

Etiology

Central Nervous System Stimulation

Drug/Toxin

  • Doxapram
  • Methylxanthines: stimulate ventilation and increase the ventilatory response to carbon dioxide
  • Progesterone (see Progesterone, [[Progesterone]]): increases ventilation and lowers arterial pCO2 by as much as 5–10 mm Hg
  • Salicylate Intoxication (see Salicylates, [[Salicylates]]): most common etiology if drug-induced respiratory alkalosis
    • Mechanism: direct stimulation of the medullary chemoreceptor

Withdrawal

  • Delirium Tremens (see Ethanol, [[Ethanol]])

Infection

Other

  • Anxiety/Panic Disorder
  • Central Nervous System Space-Occupying Lesion
    • Brain Tumor
  • Fever (see Fever, [[Fever]])
  • Ischemic Cerebrovascular Accident (CVA) (see Ischemic Cerebrovascular Accident, [[Ischemic Cerebrovascular Accident]])
  • Pain

Peripheral Stimulation

Unknown Mechanism

  • Metabolic Encephalopathy
  • Sepsis (see Sepsis, [[Sepsis]]): respiratory alkalosis may occur early prior to the onset of fever and hypotension

Physiology

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Diagnosis


Clinical Features of Respiratory Alkalosis

General Comments

  • Clinical Manifestations Attributable to Acute Respiratory Alkalosis are More Common Than in Metabolic Alkalosis: respiratory alkalosis probably causes a larger change in intracellular and brain pH than metabolic alkalosis
    • Acute Respiratory Alkalosis: rapid shift in arterial pCO2 is almost immediately transmitted throughout the total body water (including the intracellular fluid compartment, the brain, and the cerebrospinal fluid) -> this accounts for the characteristic symptoms of paresthesias, carpopedal spasm, and lightheadedness observed in acute respiratory alkalosis
    • Metabolic Alkalosis: alterations in blood bicarbonate cause slower and less marked pH changes within the intracellular fluid compartment and across the blood brain barrier

Cardiovascular Manifestations

Dermatologic Manifestations

Neurologic Manifestations


Treatment

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References

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