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Respiratory alkalosis
Last reviewed: 23.04.2024
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Respiratory alkalosis - a primary decrease in PSR2 with or without compensatory reduction of HCO3; The pH can be high or close to normal. The reason - an increase in the frequency of respiration and / or the respiratory volume (hyperventilation). Respiratory alkalosis can be acute or chronic. The chronic form is asymptomatic, but the acute form causes dizziness, impaired consciousness, paresthesia, spasms, fainting. Signs include hyperpnoea or tachypnea, carpopedal spasm.
[Causes of the respiratory alkalosis
Respiratory alkalosis is characterized by a primary decrease in PCO2 (hypocapnia) due to increased respiratory rate and / or tidal volume (hyperventilation). Increased ventilation is often observed as a physiological response to hypoxia, metabolic acidosis, increased metabolic needs (eg, fever), often observed in many severe conditions. Also, pain, anxiety, and some disorders of the central nervous system can increase breathing without a physiological need.
Respiratory alkalosis can be acute or chronic. The difference is based on the degree of metabolic compensation; within minutes the excess HCO3 "binds extracellular H, but more significant compensation is observed after 2-3 days, when the kidneys reduce the excretion of H.
Pseudo-respiratory alkalosis is characterized by low arterial and high pH in patients with severe metabolic acidosis due to poor systemic circulation (eg cardiogenic shock, during cardiopulmonary resuscitation). Pseudo-respiratory alkalosis is observed when mechanical ventilation (often hyperventilation) displays greater amounts of alveolar CO2 than normal. Significant amounts of alveolar CO2 cause obvious respiratory alkalosis according to the gas composition of the arterial blood, but poor systemic perfusion and cellular ischemia lead to cellular acidosis, which leads to acidosis of venous blood. Diagnosis is based on the detection of a significant arteriovenous difference in pH and in determining the elevated level of lactate; treatment is to improve systemic hemodynamics.
Symptoms of the respiratory alkalosis
Symptoms of respiratory alkalosis depend on the speed and degree of fall in the level of PCO2. Acute respiratory alkalosis causes dizziness, impaired consciousness, peripheral and perioral paresthesia, spasms, fainting; it is assumed that the mechanism consists in changing cerebral blood flow and pH. Often the only sign is tachypnea or hyperpnoea; in severe cases, carpopedal spasm can be observed. Chronic respiratory alkalosis usually occurs asymptomatically and does not have distinctive signs.
Diagnostics of the respiratory alkalosis
It is necessary to determine the gas composition of arterial blood and plasma electrolyte levels. A slight hypophosphatemia and hypokalemia can occur as a result of intracellular movement and a decrease in the level of ionized Ca ++ with an increase in the binding ability of proteins.
The presence of hypoxia or an increase in the alveolar arterial gradient [PO2 on inspiration - (arterial PO2 + 5/4 arterial P2O2)] requires a search for a cause. Other causes are usually evident from the history and examination data. However, since pulmonary embolism is often observed without hypoxia, in patients with hyperventilation before decongesting the cause for concern, it is first necessary to exclude embolism.
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Treatment of the respiratory alkalosis
Treatment of respiratory alkalosis is directed to the original cause; Respiratory alkalosis is not a life-threatening condition, therefore, there is no need to carry out measures to change the pH. The increase in CO2 content in respirable air with respiratory respiration (for example, using a paper bag) is used quite often, but it can be dangerous in patients with CNS disorders whose pH of the cerebrospinal fluid may be below normal.