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Acid-Base Physiology I and II

Terms in this set (65)

In such cases there is a primary abnormality and, possibly, a compensatory process.
-There are occasional situations, however, where patients may have more than one disorder going on at the same time.
-For example, it is possible for patients to have a concurrent metabolic acidosis and metabolic alkalosis or a concurrent elevated anion-gap acidosis and non-anion gap acidosis
>The only combination you cannot have is a combined respiratory alkalosis and acidosis as it is impossible for the patient to hyper- and hypoventilate at the same time

-These situations are referred to as mixed acid-base disorders.
-One way to determine if a mixed acid-base disorder is present is to calculate the anticipated response to the primary abnormality.
-If the actual response deviates from this value then you know an additional process may be at work.
-There are equations for example, that stipulate that the bicarbonate should change by a certain amount in response to a chronic respiratory acidosis.
-The problem is that these equations are difficult to remember and, as a result, are tedious to apply in the acute setting.
-An alternative approach is to calculate what is referred to as the Delta-Delta.
>This approach, which gives you a sense of whether the body is holding onto or losing more bicarbonate than you would expect simply based on looking at the pH, serum anion gap (SAG) and the bicarbonate values, can be done as follows: ->Calculate the Delta Gap: Measured SAG - Normal SAG (12)
->Calculate the Delta Delta: Add the Delta Gap to the measured bicarbonate (from the chemistry panel)
->Compare the Delta Delta to a normal bicarbonate (22-28):
->If the Delta Delta <22, the patient is losing bicarbonate somewhere and there is a NON-gap acidosis.
->If you found a non-gap acidosis (either the compensatory or the primary process) in the initial steps above, then the acidosis you identify here represents the same process.
-If however, you did not identify an acidosis in the earlier steps or you identified a gap acidosis in the initial steps, then this last step reveals the presence of an additional non-gap acidosis.
>If the Delta Delta >28, the patient is holding onto bicarbonate and there is an additional metabolic alkalosis. -If you found an alkalosis (either the compensatory or the primary process) in the initial step above, then the alkalosis you identify here represents the same process.
-If however, you identify an acidosis in the initial steps and then this last step reveals the presence of alkalosis, you have found an additional metabolic process.