A 27 year old female presents to your Emergency Department by ambulance. She has been unwell for 2 days and complains of fever, sore throat and a cough.
BP 106/50 mmHg
Her blood gas shows:
pCO2 38.6 (35-45 mmHg)
HCO3 16.2 (24+/-2 mmol/l)
BE -8 (-2-+2)
Hb 136 (115 – 135 g/l)
Na 127 (136 – 145 mmol/l)
K 5.7 (3.3 – 5 mmol/l)
cCa 0.99 (2.2 – 2.55 mmol/l)
Cl 100 (99 – 111 mmol/l)
Glucose 18.9 (3 – 6 mmol/l)
Lactate 1.4 (<2 mmol/l)
1. Describe the abnormalities
2. Interpret your findings
3. What key features would you look for on examination
4. List your treatment priorities
Thank you Claire Mcquillan for this awesome case
1. Tachycardia, tachypnoea, febrile
Low normal pH, low normal pCO2.
Very low pO2 – likely VBG.
Moderately low HCO3
Base excess -8: appropriate for HCO3 of 16
Hb just elevated out of normal range at 136
Hyponatraemia – mild. Actual Na is 131 correcting for BSL.
Hyperkalaemia – mild. Expected K with pH of 7.35 is 5.25 approx.
Very low Ca2+
Metabolic acidosis – moderate
Expected pCO2 by Winter’s formula is 1.5 x 16 + 8 = 32
So mild resp acidosis also.
Anion gap using corrected Na is 131 – 100 – 16 = 15
Delta ratio 3/8 – so mixed HAGMA and NAGMA
?Mild DKA correcting itself
Adrenal insufficiency with concurrent illness
Renal tubular acidosis
?no suggestion of toxins.
Would suggest further investigations, such as renal function, albumin, blood ketones, urine and serum osmolality, urinary Na, dipstick and urinary pH.
Dehydration – reduced skin turgor, dry mucous membranes, hypotension, IVC on U/S.
Skin pigmentation, vitiligo consistent with Addisons
4. Rehydration, correction of electrolytes, consider dexamethasone 10mg IV. Management of precipitating illness with ibuprofen/paracetamol/fluids.
A couple of points:
1. When calculating anion gap, it is not necessary to use corrected Sodium. See this article
2. Usually not necessary to correct for Potassium when the pH is normal (shifts are pH dependant)
3. Difficult to assess CO2 in the seting of a VBG if the changes are small
The answer should appear on Wednesday, have a read and let me know what you think.