A 57 year old man presents to your ED with some spastic movements of his limbs. He has a history of chronic pain in his shoulders, back and nack for which he is on pain medication.
His blood gas shows:
pH 6.906 (7.36-7.44)
pCO2 96.8 (35-45 mmHg)
HCO3 18.2 (22-26 mmol/l)
BE -19 (0+/-2)
Na 148 (137-145 mmol/l)
K 3.8 (3.3-5 mmol/l)
Cl 106 (99-111 mmol/l)
Glu 6.9 (4-6 mmol/l)
Lactate 17 (<2 mmol/l)
Creat 93 (<130umol/l)
Describe and Interpret his blood gas
What are the possible causes?
Blood Gas: critically severe respiratory acidosis with coexisting high anion gap lactic acidosis.
anion gap 24 expected bicarb compensation for this CO2 (if acute) is 28.5 (if chronic 42) but his lactate is 18
slight hypernatremia, normal glucose, normal creatinine
Difficult differential, knowing GCS, temp and oxygenation would help.
Possible causes: cervical spinal cord compression from e.g. spinal canal stenosis, abscess, tumour, TB as cause for chronic pain and now spasticity, and hypoventilation (hypercarbia) . Lactic acidosis may be from an intercurrent infection/sepsis e.g. the abscess if present, pneumonia if under ventilating, or other. lactic acidosis may also be from infarction of tissue – e.g. spinal tissue? hard to explain that. or generalised severe hypoxia.
other causes for severe respiratory acidosis – opiate toxicity, baclofen toxicity, but both would have severe GCS. suffocation and severe hypoxic lactic acidosis – but stem does not suggest it. neuromuscular weakness, cyanide toxicity…
… or multiple myeloma with type B lactic acidosis
or intracranial malignancy
or even tetanus
Very good interpretation. The actual cause was very straight forward. See the follow up post.