Lab Case 332 – Interpretation

A 4 week old is brought to ED post cardiac arrest – the child was found in her cot not breathing. The parents performed CPR immediately and on arrival the child had ROSC. The child has been unwell for a few days

A VBG was performed

pH 6.83                               Na 141mmol/l

pCO2 68 mmHg                K 6.4 mmol/l

pO2 39 mmHg                   Cl 110mmol/l

HCO3 11 mmol/l              Cr 45 umol/l

B/E-22                                 BSL 9mmol/l

Lactate 18 mmol/l


  1. Describe and Interpret the VBG
  2. List possible causes of a critically unwell neonate



pH 6.83 acidaemia

Combined metabolic and respiratory acidosis – pCO2 68 mmHg and HCO3 11mmol/l

AG = Na – (HCO3 + Cl) = 20

Delta ratio = Change in AG/Change in HCO3 = 20-12/24-11 = 0.6 (HAGMA and NAGMA)

Raised potassium in proportion to low pH – corrected K 3.4mmol/l

Severely raised lactate

The above VBG shows a combined respiratory acidosis as well as a NAGMA and HAGMA.  The respiratory acidosis is secondary to the cardiorespiratory arrest, the HAGMA most likely secondary to the severe lactic acidosis and the NAGMA in the context of an unwell neonate – diarrhoea and Addison’s disease are possible causes. The lactic acidosis is most likely a type A – increased demand acidosis from cardiogenic shock/arrest

Causes of a critically unwell neonate includes: (THE-MisFits)

Trauma (including NAI)

Heart disease



In born errors of metabolism