Click on an example above
|11. Metabolic Acidosis with Respiratory Depression.
A road traffic accident has caused multiple injuries to both legs of this man. The metabolic acidosis due to ischemic lactic acid release. In response the patient was hyperventilating and initially had a respiratory alkalosis.
Treatment with morphine depressed the ventilation and the PCO2 rose from the typical value of 28 mmHg to an apparently normal PCO2 of 40 mmHg.
If these acid-base results were reviewed with no knowledge of the patient's history, this would appear to be a case of pure metabolic acidosis. However, metabolic acidosis typically elicits hyperventilation in partial compensation. A pure metabolic acidosis, therefore, implies the probability that there is, as in this case, respiratory depression - a respiratory acidosis moving the patient in a more acid direction than expected.
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.|
All Rights Reserved