alcalosis

Alkalosis is a condition in which the body’s fluids become more alkaline, with a blood pH above 7.45. It can arise from either a decrease in hydrogen ion concentration (metabolic alkalosis) or a reduction in carbon dioxide (respiratory alkalosis). Each form has characteristic causes, patterns, and management strategies.

Metabolic alkalosis results from an increase in bicarbonate or a loss of hydrogen ions. Common causes include loss of gastric acid from prolonged vomiting or nasogastric suction, diuretic therapy, alkali ingestion, and hyperaldosteronism. It may also occur with volume depletion and certain renal tubular disorders. Chloride status helps distinguish subtypes: chloride-responsive metabolic alkalosis (low to normal chloride, often due to vomiting or diuretics) tends to improve with saline and correction of potassium; chloride-resistant metabolic alkalosis (high potassium depletion or mineralocorticoid excess) is less responsive to fluid therapy and may require addressing the underlying hormonal or renal problem.

Respiratory alkalosis is caused by hyperventilation, which lowers arterial CO2 tension. Acute triggers include pain, anxiety, hypoxemia, fever, and pulmonary disease; pregnancy and high altitude can contribute. Compensation is primarily renal, with increased bicarbonate excretion over hours to days, lowering the pH toward normal if the underlying cause is treated.

Diagnosis relies on arterial blood gas analysis showing pH > 7.45, with elevated bicarbonate in metabolic cases or decreased PaCO2 in respiratory cases, along with electrolytes such as potassium and chloride. Management targets the underlying cause and may involve fluid and electrolyte replacement, correction of potassium and chloride deficits, or treatment of the inciting condition for respiratory alkalosis.