Metabolic alkalosis

 

 

 

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A metabolic alkalosis is characterised by a high plasma bicarbonate.

The initial presence of excessive amounts of bicarbonate in plasma may be due to

1. Excessive loss of hydrogen ions from the system - either from GI tract / kidney
2. Administration of bicarbonate

The kidney play a vital part in the origin of a metabolic alkalosis. Normally any excess bicarbonate in plasma is promptly excreted by the kidney. Failure of this mechanism results in retention of bicarbonate.

Classification

The classification of a metabolic alkalosis is based on the observation that a defecit of chloride plays key part in the development and maintenance of this type of alkalosis. Hence -

Chloride sensitive
Chloride resistant
Exogenous bicarbonate

Measure urine chloride (UCl) to help in classification

Chloride sensitive - UCl < 20 mmol/l
Chloride resistant - UCl > 20 mmol/l