Lab Case 41

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

PR  135/min

T  38.3

RR   26/min

Her blood gas shows:

pH  7.357

pCO2  38.6      (35-45  mmHg)

pO2 24.4

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


2 thoughts on “Lab Case 41

  1. 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+
    Elevated Glucose

    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

    2. Interpret:
    Given hx:
    ?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.

    3. Examination:
    Dehydration – reduced skin turgor, dry mucous membranes, hypotension, IVC on U/S.
    Skin pigmentation, vitiligo consistent with Addisons
    Postural BP
    Urine output
    MMSE, ECG.

    4. Rehydration, correction of electrolytes, consider dexamethasone 10mg IV. Management of precipitating illness with ibuprofen/paracetamol/fluids.

  2. Hi Simon,
    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.

Comments are closed.