ABGs Flashcards
Normal pH
7.35-7.45
What does <7.35 pH indicate?
Acidosis (more H+ ions)
What does >7.45 pH indicate?
Alkalosis (less H+ ions)
What does PaO2 show?
- Partial pressure of O2 dissolved in plasma (3-5% of total oxygen content of arterial blood)
- tells us how well oxygen is moving from alveoli into the blood
Normal PaO2 value
80-100 mmHg
PaO2 indicating hypoxemia
<60 mmHg
What does PaCO2 show us?
- Partial pressure of CO2 dissolved in plasma (5% of total CO2 content in arterial blood)
*Measure of carbonic acid
*Direct reflection of alveolar ventilation (how well the pt is ventilating, NOT oxygenation)
Normal PaCO2 range
35-45 mmHg
What does a PaCO2 <35 indicate?
Hyperventilation (blowing off too much CO2 = alkalosis)
What does a PaCO2 >45 indicate?
Hypoventilation (CO2 buildup = **Respiratory acidosis)
Causes of respiratory acidosis
- CNS depression
- Impaired neuromuscular function
- Chest wall trauma
- Large pneumo or Hemothorax
- Airway disease or obstruction
- Overdose (causing CNS depression)
- Electrolyte imbalances - low phosphate, low potassium
Manifestations of respiratory acidosis
- CNS depression (lethargy, dizziness, mental cloudiness, HA, coma) *Remember acid is a depressant
- Depression of myocardial contractility
- V fib
- Increased RR
- Decreased affinity of Hg for O2 (Hgb wont pick up as much O2 now)
Treatment for respiratory acidosis
- Increase alveolar ventilation
- TCDB/incentive spirometer
- Suction
- Mechanical ventilation - Correct the cause
- Administer O2
What does a PaCO2 <35mmHg indicate?
Respiratory Alkalosis (alveolar hyperventilation)
Causes of respiratory alkalosis
- Hypoxemia (too much compensation)
- Artificial ventilation (over compensation)
- Stress
- Anxiety
- Fear
Respiratory alkalosis manifestations
CNS excitability (tingling, twitching, tremors, seizures)
Arrhythmias (premature beats & tachys)
Decreased ventilation (trying to compensate)
Increased affinity of Hg for O2 (hgb doesn’t drop O2 off to cells as well)
Treatment for respiratory alkalosis
- Decrease alveolar ventilation
- Correct the cause
What does HCO3 measure?
Metabolic base (which is regulated by the kidneys)
Normal HCO3 range
22-28 mEq/L
What does an HCO3 <22 indicate?
Metabolic acidosis (base deficit)
What does an HCO3 >28 mEq/L indicate?
Metabolic Alkalosis (Base excess)
Causes of metabolic acidosis
- Increased production of acids (ex: DKA)
- Reduced excretion of acids (Renal Failure)
- Excessive loss of base (diarrhea)
Manifestations of metabolic acidosis
- HA
- Confusion
- Drowsiness
- N/V
- Hyperventilation
Treatment of metabolic acidosis
- Correct the cause
- If severe, administer bicarbonate (pH <7)
Causes of metabolic alkalosis
- Loss of chloride (vomiting, NG suction, diuresis)
- Chronic respiratory acidosis (conserving bicarbonate to compensate)
- Base administration (too much)
Manifestations of metabolic alkalosis
- Numbness
- Tingling
- Dizziness
- Carpopedal spasm (contracture of hand)
- Decreased RR & depth (compensating to help kidneys)
Treatment for metabolic alkalosis
- Administer chloride (NS + extra potassium chloride)
- Correct cause
What does SaO2 show?
Degree to which Hg molecules are saturated with O2
Normal SaO2 level
> or= 95%
What does an SaO2 <90% indicate?
Hypoxemia
How does the respiratory system compensate?
Acts in minutes to hours
Controls CO2 concentrations in ECF by changing rate and depth of respiration
How does the renal system compensate?
Acts in hours to days
Increases or decreases HCO3 in ECF
