ABGs Interpretation

Question 1

What do ABGs show?

Answer 1

ABGs show a pts respiratory and metabolic status

• 94-98% O2 is the target sats
  
  • normal O2 sats mean we want to check metabolic status - could use VBG instead
• lactate = shows major organ perfusion

FIO2 is the inspired O2 conc - we want to know this for the ABG machine e.g. how much o2 is pt on NB:room air is 21% oxygen

Temperature alters reference range - if pt has an infection etc

• HCO3 is metabolic
  
  • inc BE = inc alkalosis (HCO3)
  • dc BE = acidic
• PO2 and PCO2 is resp

Question 2

What steps should you look at an ABG in?

Answer 2

1. Oxygenation - PaO2
2. CO2
3. pH
4. LOOK AGAIN @ PCO2
5. Bicarbonate
6. Compensation

Question 3

What should be considered about oxygenation levels in an ABG - PaO2?

Answer 3

• are they hypoxic
• >10kPa on air?
  
  • should be ~10% less than inspired O2
• <10kPa = HYPOXIC
• <8 = severly hypoxic & in RESP FAILURE

venturi masks are: 24, 28, 35, 40 & 60

a hudson mask is a non rebreathe mask = is 80% as system isnt sealed –> a bag valve mask is a seal

Question 4

What should be considered about carbon dioxide levels in an ABG - PaCO2?

Answer 4

• type 1 resp failure
  
  • decreased oxygen (<8kPa) and a normal/low CO2
  • Causes:
    
    • V/Q mismatch
    • PE
    • pulm oedema
    • pneumonia
• type 2 respiratory failure
  
  • LOW O2 and HIGH CO2
  • cause
    
    • ventrilation problems e.g. getting in and out of lungs problem
    • reduced respiratory drive and hypoventilation
    • e.g. brain problems / chest wall / ribcage decreased expansion
    • pulmonary cause

Question 5

What should be considered about pH levels in an ABG?

Answer 5

• <3.5 is acidosis
• >7.45 is alkalosis

Question 6

What should be considered about CO2 levels when you look at them AGAIN (after O2, Co2, pH…)?

Answer 6

looking again at PCO2 for metabolic side

• acidosis and raised PCO2 = respiratory acidosis
• Alkalosis and LOW PCO2 = resp alkalosis

Question 7

What should be considered about bicarbonate levels in an ABG?

What is SMORF?

Answer 7

• acidosis (low pH) and HCO3 LOW = metabolic acidosis
• alkalosis (high pH) and HIGH HCO3 = metabolic alkalosis

SMORF- Same (direction as pH) = Metabolic & Opposite (direction of pH) = Respiratory

Question 8

How do you check for compensation?

Answer 8

NB: remember you can get partial/alltogether compensation - think is the pH still affected?

is the alternative still in range e.g. not comp?

Question 9

What is anion gap?

what is MUDPILES?

Answer 9

• metabolic acidosis
  
  • can also include an anion gap (+ takeway -ve ions)
• normal anion gap = losing bicarb
• high = excess acid - so where is the acid coming from

if the anion gap is high (met acidosis)

• losing HCo3 by diarrhoea/gi tract

uraemia can cause acidosis, so can sepsis

(mudpiles; methanol, uraemia, diabetic/alco/starvation ketoacidosis, paracetamol, iron, lactic acidosis, ethanol (from lactic acidosis), salicylates)