Which of the following indicates compensated metabolic alkalosis?


Which of the combinations of laboratory results below indicates compensated metabolic alkalosis?
a. Low PCO2, normal bicarbonate, high pH
b. Low PCO2, low bicarbonate, low pH
c. Normal PCO2, low bicarbonate, low pH
d. High PCO2, normal bicarbonate, low pH
e. High PCO2, high bicarbonate, high pH

e. High PCO2, high bicarbonate, high pH
(Murray, pp 15–26.)

Pure metabolic acidosis (choice c) or pure metabolic alkalosis exhibits abnormal bicarbonate and normal lung function. Pure respiratory acidosis (choice d) or alkalosis (choice a) is associated with normal renal function (and normal blood acids) with a normal bicarbonate and abnormal PCO2. Thus choices b and e must involve compensation, since both the PCO2 and bicarbonate are abnormal. Choice e must represent compensated metabolic alkalosis since the PCO2 is high—if it were compensated respiratory acidosis with a high PCO2, the pH would be low.