Distinction of saline responsive from saline unresponsive metabolic alkalosis is important for both diagnosis and management.


Laboratory features of metabolic alkalosis:

(1) elevated serum pH

(2) normal to increased PaCO2

(3) elevated serum bicarbonate

(4) variable depletion of chloride, potassium and sodium


Urine pH:

(1) early the urine pH is alkaline, with excretion of sodium and potassium

(2) with potassium depletion, the urine pH becomes acid and there is less excretion of sodium and potassium


Saline Responsive Metabolic Alkalosis


Saline responsive metabolic alkalosis - Features:

(1) urine chloride often < 10 mmol/L but may be higher; recent diuretic therapy can result in value > 20 mmol/L

(2) volume depletion with orthostatic hypotensive, tachycardia, poor skin turgor


Saline responsive metabolic alkalosis - Causes:

(1) vomiting, continuous gastric aspiration or other loss of gastric fluid

(2) exogenous alkali (diet, antacids, blood transfusions)

(3) diuretic therapy


Saline responsive metabolic alkalosis - Management:

(1) infusion of normal saline

(2) correction of hypokalemia with potassium chloride

(3) adequate amounts of chloride, with endpoint urine chloride > 40 mmol/L


Saline Unresponsive Metabolic Alkalosis


Saline unresponsive metabolic alkalosis - Features:

(1) urine chloride > 20 mmol/L without recent diuretic use

(2) increased extracellular fluid volume

(3) normotensive or hypertensive


Saline unresponsive metabolic alkalosis, normotensive - Causes:

(1) severe potassium depletion

(2) hypercalcemia (?)


Saline unresponsive metabolic alkalosis, hypertensive - Causes:

(1) mineralocorticoid excess (hyperaldosteronism, hyperreninism, licorice ingestion)


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