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|12. Metabolic Alkalosis with Positive Pressure Ventilation.
Protracted diuretic therapy has caused significant metabolic alkalosis. This man normally has a slight respiratory acidosis because he tends to retain carbon dioxide in partial compensation. His usual PCO2 is about 49 mmHg. When undergoing emergency eye surgery, the anesthesiologist ventilates the patient to a PCO2 of 40 mmHg - a value which appears to be normal.
Examined in isolation, these results would appear to be typical of a pure metabolic alkalosis. However, the typical response to metabolic alkalosis is retention of carbon dioxide. When a metabolic alkalosis is not associated with the typical respiratory acidosis, it suggests some other factor may be at work - as here.
The diagram shows the position of the principal zones. These zones are based on the review of the literature described by Schlichtig, Grogono, and Severinghaus. The arrows indicate typical acidosis and alkalosis. The labels in the black circles correspond to the legend in the table below.
|AR||Acute Respiratory Acidosis:||SBE = 0|
|CR||Chronic Respiratory Acidosis:||SBE = 0.4 x PCO2|
|M||Metabolic Acidosis:||PCO2 = 1.0 x SBE|
|AR||Acute Respiratory Alkalosis:||SBE = 0|
|CR||Chronic Respiratory Alkalosis:||SBE = 0.4 x PCO2|
|M||Metabolic Alkalosis:||PCO2 = 0.6 x SBE|
Alan W. Grogono
|Copyright Oct 2016.|
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