Lab Case 224 answers

Question 1:

  • Ph = 7.28 so we have acidaemia
  • HCO3 = 11.1 (low) so the process is metabolic acidosis
  • Next we have to calculate the anion gap and check for compensation.
    AG = Na – (Cl + HCO3) that is 133 – (108 + 11) = 14 (slightly elevated – can be considered normal)

Compensation is calculated using winter’s formula (expected PCO2 = 1.5 x HCO3 + 8 +/- 2) that is 1.5X11+8 = 24.5 so we have fully compensated metabolic acidosis.
For completion we can calculate delta ratio (AG-12)/(24-HCO3) that is 2/13 = 0.15 (< 0.4) so we have pure NAGMA.

The other findings on the blood gas were:
Mild hyperchloraemia
Elevated ketones (ketosis).
So final interpretation is Normal anion metabolic acidosis with mild hyperchloraemia and ketosis.

Question 2:
For NAGMA, considering the USED CARP mnemonic,
S—Small bowel fistula
E—Extra chloride
C—Carbonic anhydrase inhibitors
A—Adrenal insufficiency/ Addison’s disease
R—Renal tubular acidosis
P—Pancreatic fistula.

This patient had mild hyperchloraemia, RTA is another potential cause.

Regarding the Ketosis/ Ketoacidosis.

Causes are:

  • Diabetic Ketosis – Glucose level was normal.
  • Alcoholic ketosis – what are the chances
  • Starvation ketosis – this child didn’t eat for 2 days; she was drinking water only.
  • The other cause for ketosis is a side effect of medication – antipsychotics/ SGLT2 Inhibitor Diabetes Drugs.

The child was put on maintenance dose of N/S and 5% dextrose. She was admitted under the paediatric endocrinology team. Her blood gases normalized within 8 hours.
She was reviewed the Metabolic disease team and no cause was found. She was also reviewed by the renal team, all her urinary electrolytes were within normal ranges and RTA was excluded.
The final conclusion regarding these changes was starvation.

**** The final message, children are more prone to ketosis, and when rehydrating a child consider adding glucose to the rehydrating solution (ORS instead of water, N/S + 5% dextrose instead of N/S alone).