alkalose

Alkalose, or alkalosis, is a condition in which the body's fluids become more alkaline than normal, with a blood pH above 7.45. It can arise from a primary decrease in hydrogen ion concentration or from an excess of bicarbonate. The two main categories are respiratory alkalosis, caused by low carbon dioxide, and metabolic alkalosis, caused by elevated bicarbonate or loss of hydrogen ions. In respiratory alkalosis, a reduced arterial PCO2 drives the pH up; in metabolic alkalosis, elevated HCO3- is the main driver.

Respiratory alkalosis results from processes that increase ventilation and lower PCO2, such as anxiety or pain, fever, hypoxemia, high altitude exposure, or certain forms of mechanical ventilation. Metabolic alkalosis can occur with loss of gastric acid from vomiting or gastric suction, volume depletion (contraction alkalosis), diuretic use, mineralocorticoid excess, or severe potassium depletion. Some cases involve a combination of factors.

Clinical features vary with the underlying cause and electrolyte balance. Common symptoms include lightheadedness, tingling around the mouth or in the extremities, muscle cramps, irritability, and confusion; severe cases can cause tetany, seizures, or cardiac arrhythmias, particularly with accompanying hypokalemia or hypochloremia.

Diagnosis rests on arterial blood gas measurements and electrolyte testing. Typical findings are a blood pH > 7.45, with elevated bicarbonate levels in metabolic alkalosis or reduced PCO2 in respiratory alkalosis; chloride and potassium abnormalities help differentiate chloride-responsive from chloride-resistant forms.

Treatment targets the underlying cause. Metabolic alkalosis often improves with volume repletion and correction of electrolytes (particularly potassium and chloride); acetazolamide may be used in select cases. Respiratory alkalosis is managed by addressing the cause of hyperventilation and, in severe cases, controlled ventilation to increase CO2. Prognosis generally depends on the underlying condition and the patient’s comorbidities.