Emergency medicine Flashcards
What is normal pH on a blood gas?
7.35 to 7.45
What is normal PaCO2 on a blood gas?
4.7 - 6 kPa
What is normal PaO2 on a blood gas?
11-13 kPa
What is a normal HCO3- on a blood gas?
22-26 mEq/L
What is a normal base excess on blood gas?
-2 to +2 mol/L
How to see if the patient is hypoxic on the blood gas
PaO2 should be >10 on room air
If they’re having oxygen therapy - their PaO2 should be 10kPa less than the % inspired concentration FiO2
What percentage oxygen is delivered by nasal cannulae, simple face masks, non-rebreather mask and venturi masks?
Nasal cannulae - 1L - 24% 2L - 28% 3L - 32% 4L - 36%
simple face mask - 40-60%
Non-rebreather mask - 60-90%
venturi masks - 24% 28% 35% 40% 60%
What are the two types of respiratory failure?
Type 1 respiratory failure = hypoxaemia with normocapnia
Type 2 respiratory failure = hypoxaemia with hypercapnia
Causes of type 1 respiratory failure
Pulmonary oedema
Bronchoconstriction
Pulmonary embolism
Causes of type 2 respiratory failure
COPD pneumonia rib fractures obesity Guillain Barre MND Opiates
What are the 4 acid base disturbances you see on blood gas?
Respiratory acidosis - acidotic pH <7.35, with high PaCO2 & normal HCO3-
Respiratory alkalosis - alkalemic pH >7.45, with PaCO2 low & normal HCO3-
Metabolic acidosis - acidotic pH <7.35, with normal PaCO2 & low HCO3-
Metabolic alkalosis - alkalemic pH >7.45, with PaCO2 normal & high HCO3-
How can you tell if an acid base abnormality has been compensated for on blood gas?
Respiratory acidosis with metabolic compensation - low/normal pH, with high PaCO2 and high HCO3-
Respiratory alkalosis with metabolic compensation - high/normal pH, with low PaCO2 and low HCO3-
Metabolic acidosis with respiratory compensation - low pH, with low HCO3- and low PaCO2
Metabolic alkalosis with respiratory compensation - high pH, with high HCO3- and high PaCO2
What does base excess show on a blood gas?
shows metabolic acidosis or alkalosis
- High BE = there is a higher than normal amount of HCO3- in the blood (due to metabolic alkalosis or compensated respiratory acidosis)
- Low BE = there is a lower than normal amount of HCO3- in the blood (metabolic acidosis or compensated respiratory alkalosis)
How can you tell if there’s mixed acidosis and alkalosis?
the CO2 and HCO3– will be moving in opposite directions (e.g. ↑ CO2 ↓ HCO3– in mixed respiratory and metabolic acidosis).
Causes of respiratory acidosis
Respiratory depression - opiates
Guillian-Barre
Asthma
COPD
Causes of respiratory alkalosis
Anxiety - panic attack pain causing an increase RR Hypoxia causing increased alveolar ventilation to try compensate PE Pneumothorax