A 35-year-old man develops septicaemia following surgery for a perforated acute appendicitis. He is hypotensive. Arterial blood gas analysis reveals the following: - pH: 7.25 (Normal: 7.35–7.45) - PaO₂: 7.2 kPa (Normal: 11.9–13.3 kPa) - PaCO₂: 7.5 kPa - Bicarbonate (HCO₃⁻): 17 mmol/L What is the most likely explanation for these findings?