Data Interpretation: Arterial Blood Gas Flashcards
What are the 2 main conclusions to find in ABG interpretation?
If the patient has respiratory acidosis or respiratory alkalosis
If the patient has type 1 or type 2 respiratory failure
What is the normal pH range in ABG interpretation?
pH 7.35-7.45
Can a patient with respiratory acidosis or alkalosis still have a normal pH value?
Yes, if there is full compensation then the pH will be within normal range but near the range limits
What value should you first look at in ABG interpretation?
The pH value
In ABG interpretation, which 2 values should you look at after looking at the pH value?
CO2 value and HCO3- value
If patient’s pH is acidotic or alkalotic, these values indicate if its due to respiratory or metabolic causes
In ABG interpretation, what is meant by respiratory acidosis?
The pH is normal/acidotic and is driven primarily by a high CO2 level in the blood
In ABG interpretation, what is meant by respiratory alkalosis?
The pH is normal/high which is primarily driven by a low CO2 level
In ABG interpretation, what is meant by uncompensation, partial or full compensation?
Partial compensation: pH value is not within normal range, secondary component is high
Full compensation: pH value is within normal range, secondary component is high
Uncompensation: pH value is not within normal range, secondary component is normal
In ABG interpretation, what is meant by metabolic acidosis?
The pH value is normal/low which is primarily driven by low HCO3- value
In ABG interpretation, what is meant by metabolic alkalosis?
The pH value is normal/high which is primarily driven by high HCO3- value
What is the normal range of PaCO2, in ABG interpretation?
PaCO2: 4.5-6 kPa OR 35-45 mmHg
What is the normal range of HCO3-, in ABG interpretation?
HCO3-: 22-26 mmol/L
In ABG interpretation, what is meant by respiratory acidosis with full metabolic compensation?
pH: 7.35-7.45
PaCO2: (high) more than 6kPa/45mmHg
HCO3-: (high) more than 26 mmol/L
In ABG interpretation, what is meant by respiratory acidosis with partial metabolic compensation?
pH: (low) below 7.35
PaCO2: (high) more than 6kPa/45mmHg
HCO3-: (high) more than 26 mmol/L
In ABG interpretation, what is meant by uncompensated respiratory acidosis?
pH: (low) below 7.35
PaCO2: (high) more than 6 kPa/45mmHg
HCO3-: (normal) 22-26 mmol/L
In ABG interpretation, what is meant by respiratory alkalosis with full metabolic compensation?
pH: (normal) 7.35-7.45
PaCO2: (low) less than 4.5 kPa/35 mmHg
HCO3-: (low) less than 22 mmol/L
In ABG interpretation, what is meant by respiratory alkalosis with partial metabolic compensation?
pH: (high) more than 7.45
PaCO2: (low) less than 4.5 kPa/35 mmHg
HCO3-: (low) less than 22 mmol/L
In ABG interpretation, what is meant by respiratory alkalosis with no compensation?
pH: (high) more than 7.45
PaCO2: (low) less than 4.5 kPa/35 mmHg
HCO3-: (normal) 22-26 mmol/L
In ABG interpretation, what is meant by metabolic acidosis with full respiratory compensation?
pH: (normal) 7.35-7.45
PaCO2: (low) less than 4.5 kPa/35 mmHg
HCO3-: (low) less than 22 mmol/L
In ABG interpretation, what is meant by metabolic acidosis with partial respiratory compensation?
pH: less than 7.35
PaCO2: (low) less than 4.5 kPa/35 mmHg
HCO3-: (low) less than 22 mmol/L
In ABG interpretation, what is meant by metabolic acidosis with no compensation?
pH: (less) more than 7.35
PaCO2: normal
HCO3-: (low) less than 22 mmol/L
In ABG interpretation, what is meant by metabolic alkalosis with full respiratory compensation?
pH: 7.35-7.45
PaCO2: (high) more than 6kPa/45 mmHg
HCO3-: (high) more than 26 mmol/L
In ABG interpretation, what is meant by metabolic alkalosis with partial respiratory compensation?
pH: more than 7.45
PaCO2: (high) more than 6kPa/45 mmHg
HCO3-: (high) more than 26 mmol/L
In ABG interpretation, what is meant by metabolic alkalosis with no compensation?
pH: more than 7.45
PaCO2: normal
HCO3-: (high) more than 26 mmol/L
In ABG interpretation, what is meant by mixed acidosis?
Acidosis is caused by metabolic and respiratory causes
pH: less than 7.35
PaCO2: (high) more than 6kPa/45mmHg
HCO3-: (low) less than 22 mmol/L
In ABG interpretation, what is meant by mixed alkalosis?
Alkalosis is caused by metabolic and respiratory causes
pH: more than 7.45
PaCO2: (low) less than 4.5kPa/35mmHg
HCO3-: (high) more than 26 mmol/L
What are the causes of respiratory acidosis? SAINTS
Hypoventilation
S: CNS depression eg. Stroke, drugs eg. opiate overdose
A: Airway obstruction eg. COPD
I: Increased dead space eg. pulmonary embolism
N: Neuromuscular diseases
T: Trauma to chest
S: Sleep apnea
What are the causes of respiratory alkalosis?
Hyperventilation and tachycardia:
Anxiety, fear
Pregnancy
Hypoxia
High altitudes
Fever
What are the causes of metabolic alkalosis? VOMED
V: Vomiting or aspiration
O: Overcorrection of chronic high CO2 or any acidosis eg. diabetic ketoacidosis
M: Mineralocorticoid excess eg. Cushing’s
E: Early sepsis
D: Diuretics or diarrhoea
What are the causes of metabolic acidosis?
CAT MUDPILE
Congential heart failure, carbon monoxide
Alcoholic ketoacidosis
Toluline (methybenzine – used as an inhaled narcotic)
Methanol, metformin
Uraemia
Diabetic Ketoacidosis
Paracetamol
Iron, isoniazid
Lactate
Ethanol, ethylene glycol
Salicylate eg. aspirin
Which values on an ABG indicate type 1 respiratory failure?
PaO2: less than 8 kPa (hypoxaemia)
PaCO2: 4.5-6 kPa (normocapnia)
Which values on an ABG indicate type 2 respiratory failure?
PaO2: less than 8 kPa (hypoxaemia)
PaCO2: More than 6 kPa (hypercapnia)
