Lab case 43

A 28 year old female presents to your Emergency Department with palpitations and shortness of breath. She has no chest pain and no significant past medical history.

On examination she is dyspnoeic with clear lung fields and good air entry bilaterally. She has a normal CXR.


BP  120/60

PR 220/min  SVT, which reverts to a sinus rate of 110/min after Valsalva

RR 25

T  36.7 degrees celcius

Sats 84% on 15 litres non rebreather 

Her Arterial gas:

pH 7.46  (7.36-7.44)

pCO2    27 (35-45 mmHg)

pO2     49mmHg

HCO3   19  (24 +/-2 mmol/l)

Hb 194   (115-135 g/l)

Na   143  (137-145  mmol/l)

K   3.7   (3.3 – 5 mmol/l)

Cl  115   (99-111  mmol/l)


1. Describe the abnormalities

2. Interpret the findings

3. What is the most important investigation?

Thanks to Shai for this great case

5 thoughts on “Lab case 43

  1. Type 1 Respiratory failure / respiratory alkalosis/ High A- a Gradient
    Possible PE – Hypoxia / Tachycardia with clear chest
    Hb 194— Polycythemia ? Chronic hypoxia

    • Hi Karthik,

      Why the chronic hypoxia (in a 29 year old) with an acute event like a PE?

  2. Agree. Its not clear as to the duration of the symptoms and I am not sure of the reason for the polycythemia.

  3. Hi guys,

    This was my patient. I followed her up when she was admitted to CCU. She has a large ASD with Eisenmenger’s, and was referred for ASD closure.

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