Diagnosis and management of metabolic alkalosis

Elevated pH and elevated plasma bicarbonate level above normal characterise metabolic alkalosis. When bicarbonate is elevated pCO2 must also be elevated to maintain pH to its normal range. Therefore with metabolic alkalosis, the compensation is to decrease alveolar ventilation, and increase pCO2. The causes of metabolic alkalosis are gastro-intestinal hydrogen and chloride loss and due to renal cause. For metabolic alkalosis to continue both generation and maintenance of high levels of bicarbonate are necessary. The diagnosis of metabolic alkalosis is established by noting pH, serum bicarbonate (elevated) and pCO2 (compensatory) elevation. To establish the causes it is necessary to determine intravascular volume, supine and standing blood pressure and renin angiotension alolosterone axis. In chloride responsive alkalosis in which the conditions are extracellular volume depletion, hypokalaemia and hypochloraemia correction of intravascular volume with sodium chloride is needed. In severe metabolic alkalosis of any cause dilute hydrochloric acid (0.1 N HCl) may be infused intravenously but haemolysis may be a complication. In emergency situation with severe hypokalaemia dialysis with higher K+, Cl- and low HCO3- bath will be appropriate.