MSFinals-0417

A 51-year-old man is admitted with an ischaemic left leg which is unviable and requires amputation. He becomes increasingly unwell while awaiting surgery, including experiencing episodes of difficulty breathing. An arterial blood gas (ABG) was taken.
pH 7.23, pO2 12.4, PCO2 ?, HCO3− ?, lactate 10.3 mmol/l.
What are the most likely PCO2 and HCO3−?