Lab Case 77

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?


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3 thoughts on “Lab Case 77

  1. 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…

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    • … or multiple myeloma with type B lactic acidosis
      or intracranial malignancy
      or even tetanus

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    • Very good interpretation. The actual cause was very straight forward. See the follow up post.

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