Which initial change in acid-base balance will the nurse expect in the progressive stage of shock?

• A. Metabolic acidosis
• B. Metabolic alkalosis
• C. Respiratory acidosis
• D. Respiratory alkalosis

Answer: (A)

When tissue perfusion drops during the progressive stage of shock, cells switch to anaerobic metabolism and produce lactic acid. This lactic acid accumulation lowers the blood pH and consumes bicarbonate, leading to metabolic acidosis. That shift is the earliest acid-base change you’d expect as shock worsens. The body may try to compensate by increasing ventilation to blow off CO2, which can blunt the acidosis somewhat, but the primary disturbance remains metabolic acidosis. Choices involving alkalosis (metabolic or respiratory) would reflect loss of acid or excessive CO2 loss not driven by tissue hypoxia, while respiratory acidosis would come from CO2 retention due to respiratory failure, not the initial acid-base change caused by poor perfusion.