Pathophysiology and therapeutic strategy of respiratory alkalosis

Respiratory alkalosis is a condition characterized by low partial pressure of carbon dioxide and an associated elevation in arterial pH caused by an imbalance between CO2 production and removal, in favour of the latter. Conditions that cause increased alveolar ventilation, without having a reduction in pH as input stimulus, will cause hypocapnia associated with a variable degree of alkalosis. The major effect of hypocapnia is the increase in pH (alkalosis) and the consequent shift of electrolytes that occurs in relation to it. As a general law, in plasma, anions will increase, while cations will decrease. The acute reduction in ionized calcium, due to the change in extracellular pH, may cause neuromuscular symptoms ranging from paraesthesias, to tetany and seizures. The effect on urine is an increase in urinary strong ion difference/urinary anion gap and a consequent increase in urinary pH. Finally, acute hypocapnic alkalosis causes a constriction of cerebral arteries that can lead to a reduction of cerebral blood flow. The clinical approach to respiratory alkalosis is usually directed toward the diagnosis and treatment of the underlying clinical disorder