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|9. Chronic Respiratory Acidosis with Acute Metabolic Acidosis.
This patient with chronic obstructive pulmonary disease normally has a PCO2 of 60 mmHg. With this chronic respiratory acidosis he normally has a compensatory metabolic alkalosis (SBE= 7 mMol/L).
Following femoral bypass surgery his initial recovery is satisfactory. During the night the graft occludes and he develops an ischemic lactic acidosis which alters his SBE from his usual value to SBE = 0 mMol./L
These acid-base results in isolation appear to be typical of an acute respiratory acidosis with no compensation. Knowledge of the patient and familiarity with his usual values allows the results to be interpreted correctly: A patient with chronic respiratory acidosis accompanied by a developing metabolic acidosis.
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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