ABG Flashcards
What is the purpose of the arterial blood gas test?
To assess acid-base status and to determine adequacy of oxygenation and ventilation.
True or false: Bicarbonate is not measured on ABG but has to be calculated.
True
Define primary event and give examples:
The problem that initiates the acid - base imbalance.
Hyperventilation, hypoventilation, vomiting, diarrhea
What is the normal serum CO2 level?
22-26
What is normal arterial CO2 level?
35-45
Describe what a primary disorder is:
What results from the primary event - respiratory acidosis or metabolic alkalosis
In metabolic acidosis, what is the direction of the pH, HCO3, and PaCO2. Which is the causative level and which is the compensation level?
pH = decrease
HCO3 = decreased (primary)
PaCO2 = decreased (compensation)
In metabolic alkalosis, what is the direction of the pH, HCO3, and PaCO2. Which is the causative level and which is the compensation level?
pH = increase
HCO3 = increased (primary)
PaCO2 = increased (compensation)
In respiratory acidosis, what is the direction of the pH, HCO3, and PaCO2. Which is the causative level and which is the compensation level?
pH = decrease
HCO3 = increase (compensatory)
PaCO2 = increase (primary)
In respiratory alkalosis, what is the direction of the pH, HCO3, and PaCO2. Which is the causative level and which is the compensation level?
pH = increase
HCO3 = decrease (compensation)
PaCO2 = decrease (primary)
What are the causes of metabolic alkalosis?
-Excess baking soda / alka-seltzer
-Prolonged vomiting
-NG tube
-Diuretics
What are the manifestations of metabolic alkalosis?
CNS over-excitability
Confusion
Tremors
Muscle cramps
Paraesthesia
Coma
N/V/D
Respiratory depression (this is a mechanism for compensation)
What are causes of respiratory alkalosis?
Hyperventilation
Increased metabolic demands (fever, sepsis)
Medication
Acute anxiety
Hypoxia
PO / lung disease
CNS lesions
Ventilation setting
What are the manifestations for respiratory alkalosis?
CNS over-excitability
Tachypnea
Confusion
Light headedness
Blurred vision
Paraesthesia
Hyperactive reflexes
Seizures
Coma
What levels are abnormal for acute respiratory acidosis vs chronic respiratory acidosis?
Acute = PaCO2 high (> 45) BUT normal HCO3 (bicarb - or may be serum CO2)
Chronic = HCO3 high (serum CO2)
What are the causes of respiratory acidosis?
Hypoventilation
Cardiopulmonary arrest
Head injury
Narcotics / sedatives
Pulmonary disorders
Pain
Abdominal distention
Airway obstruction
Chest wall deformities
Neuromuscular problems
What are manifestations of respiratory acidosis?
CNS depression - hypoventilation, dyspnea, respiratory distress, shallow breathing, headache, restlessness, confusion, tachycardia dysrhythmias, decreased LOC, stupor, coma
What are the causes of metabolic acidosis?
Renal failure
Fistulas
Diabetes
Lactic acidosis
Prolonged diarrhea
Starvation
Shock
Cardiac arrest
What are the manifestations of metabolic acidosis?
CNS - lethargy drowsiness, confusion, tremors, muscle cramps, parasthesia
Hypotension
Hyperkalemia
Deep breathing - Kussmaul respirations
How do the kidneys compensate for respiratory acidosis or alkalosis?
Retention / excretion of H+ / HCO3
What is full compensation?
When pH is returned to a normal level
Acid and base are neutralized but not corrected
What is partial compensation?
pH is still abnormal
Acid AND base abnormal
What is uncompensation?
pH abnormal
Acid OR base abnormal (not enough time to compensate)
What is considered corrected?
pH normal, all acid / base returned to normal after imbalance
