Compensatory response to metabolic acidosis: Decrease in
bicarbonate and in PCO2
COMPREHENSION QUESTIONS
Recovery from a severe metabolic acidosis is most dependent on which of the following?
A. The rate of ventilation to blow off excess CO2
B. The rate of H+ secretion by the kidney
C. The rate of H+ excretion by the kidney
D. The arterial pH
E. The arterial PCO2
C. The rate of recovery from a severe metabolic acidosis is most
dependent on the rate of H+ excretion. Pulmonary compensation
occurs rapidly; however, it can only minimize the change in pH.
Pulmonary compensation cannot restore the balance after a metabolic
disturbance. Recovery necessitates the excretion of the entire acid
load to the system. Renal acid excretion is limited by the availability
of titratable acids and ammonia for ammonium ion formation from
CLINICAL CASES 229
230 CASE FILES: PHYSIOLOGY
secreted H+. The primary adaptive response of the kidney to an acidosis
is ammoniagenesis. Ammoniagenesis can augment the daily
excretion of acids as much as threefold. When an equivalent amount
of acid is excreted, acid–base balance will be restored.