Metabolic alkalosis is primarily due to either a gain in alkali or a loss of non-respiratory acid. The most common causes are listed in Table...?.
Table 2 Generation of metabolic alkalosis
In normal conditions, kidneys are able to excrete large amounts of bicarbonate and rapidly reverse the alkalosis. Therefore alkalosis only persists if, for any reason, the kidneys contribute to maintaining the bicarbonate excess. The principal maintenance factors are chloride depletion, decreased effective blood volume, potassium depletion, and mineralocorticoid stimulation. Chloride depletion is the most common and most important factor, and its prominent role has been emphasized repeatedly. Decreased glomerular filtration rate is usually observed but is not mandatory, at least in some models. The exact mechanisms by which these factors contribute to maintaining the alkalosis and their relative importance in different conditions has yet to be clarified. In many cases, and particularly in critically ill patients, several maintenance factors are present and contribute to the typical picture of hypochloremic hypokalemic metabolic alkalosis. Identification of maintenance factors is necessary because they can maintain the alkalosis even when the generating factors have disappeared.
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