LFTs, ABGs & Electrolytes

Question 1

Which graph can be memorised to determine whether there is an acidosis or an alkalosis?

Answer 1

• metabolic acidosis = low pCO₂ and high [H⁺]
• respiratory acidosis = high pCO₂ and high [H⁺]
• respiratory alkalosis= low pCO₂ and low [H⁺]
• metabolic alkalosis = high pCO₂ and low [H⁺]

Question 2

What is the “all roads lead to rome” analogy for interpreting ABGs?

Answer 2

“all ABGs can be solved with ROME”

• in respiratory pathology, pH and CO₂ move in OPPOSITE directions
  
  • when pH goes up, CO₂ goes down and vice versa
• in metabolic pathology, pH and CO₂ move in the SAME direction
  
  • ​when pH goes up, so does CO₂ and vice versa

Question 3

What is the first question to ask yourself when interpreting an ABG?

Answer 3

does the CO₂ explain the pH?

• if it does, then this is respiratory pathology
• if it doesn’t, then this is metabolic pathology

Question 4

What is the respiratory acid equation?

How can this help when working out ABGs?

Answer 4

H⁺ + HCO₃^- = CO₂ + H₂O

• the respiratory acid is carbonic acid
• in this equation, both sides must balance
• if there is increased CO₂, there must also be increased H⁺

Question 5

What type of ABG is shown here and how can you tell?

Answer 5

• in this example CO2