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A 21 year old man is brought in by his father with a one week history of vomiting. He has not been able to keep any food down. He has been diagnosed with Hashimoto’s thyroiditis by his local doctor 4 months previously. Today his blood pressure is 90/48 and pulse rate 104. These are his venous blood gas results:

pH 7.31
pCO2 39
pO2 25
HCO3- 19
BE -7
Na 108
K 6.2
Cl 72
Glc 3.3

Using the 7 step to ECGs:

Is it acidosis or alkalosis? ACIDOSIS

What is the primary cause? Given the low HCO3 and the not so high pCO2 it is METABOLIC ACIDOSIS.

Is there adequate compensation?

Expected pCO2 is [(1.5xHCO3) +8]+2 i.e.., [(~30) + 8]+2 = 38-39 so there is adequate compensation

What is the Anion Gap?

Na -(Cl + HCO3) = 108-(72 + 19) = 17 so raised anion gap metabolic acidosis. (reference is 8-16)

Is there any other process going on? Look at the delta gap.

change in AG/change in HCO3 = 17-12(use 12 as the expected AG)/24-19(24 is the expected HCO3)
= 5/5 = 1 so this is a pure anion gap metabolic acidosis. ( Given what I say below, I might have also expected a normal anion gap metabolic acidosis)


If we comment on the Na and K:
The Na is very low and the corrected K is (6.2 + 0.5) 6.7. This is indicative of Addison’s disease.

The patient was initially treated with 1L of normal saline stat. There was also a concern that there may have been an adrenal crisis occurring and he was given hydrocortisone IV, after which the blood pressure increase. He was admitted for slow correction of his hyponatremia and further investigation of his underlying condition.

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