Calculations

Question 1

Metabolic acidosis Exp CO2

Answer 1

1.5 x HCO3 + 8 (+/-2)

Question 2

Delta Ratio

Answer 2

[AG-12] / [24-HCO3]

<0.4 Low or normal (hyperchloraemic) AG metabolic acidosis

0. 4-0.8 Normal + HAGMA
1. 8-2.0 Pure HAGMA

>2.0 Metabolic acidosis with metabolic alkalosis/respiratory acidosis

Question 3

Osmolar Gap

Answer 3

Calculated osmolarity = (2 x [Na+]) + [glucose] + [urea])

Osmolar gap = Osmolality (measured) – Osmolarity (calculated)

normal = < 10

Consider:

• Mannitol
• Methanol
• Ethylene glycol
• Sorbitol
• Polyethylene glycol (IV lorazepam)
• Propylene glycol (IV lorazepam, diazepam and phenytoin)
• Glycine (TURP syndrome)
• Maltose (IV IG – Intragram)

Question 4

Corrected Sodium in Hyperglycaemia

Answer 4

Na + (glucose - 5)/3

Question 5

Alveolar Gas Equation

Answer 5

FiO2 (PB-PH2O) - 1.25 PaCO2

Question 6

Metabolic alkalosis

Answer 6

0.7 x HCO3 +20 (+/-5)