ABG's Flashcards
Why are ABGs important?
ABGs help maintain the balance between acids and bases in the body to achieve homeostasis.
ABG’s provide insights into the blood’s makeup ____ it is distributed to tissues.
BEFORE
Normal pH
7.35 - 7.45
(slightly alkaline)
Normal PaCO2
35 - 45 mm Hg
Normal HCO3 (bicarbonate)
22 - 26 mEq/L
Normal PaO2 (partial pressure of oxygen)
80 - 100 mmHg
Normal SaO2
(% value)
96 - 100%
(arterial oxygen saturation)
HCO3 is a component of what system?
Metabolic
- Acts as a buffer to neutralize excess acids, helping to regulate the pH of blood.
PaCO2 is a component of what system?
RESPIRATORY
- indicator of how the respiratory system regulates the removal of carbon dioxide from the blood.
PaO2 is found in what type of blood
ARTERIAL blood
- reflects the oxygen content in arterial blood, indicating how efficiently oxygen is being transported from the lungs to the bloodstream for tissue perfusion.
SaO2 is found in what type of blood
Arterial (dont mix with SpO2)
- reflects how effectively oxygen is being transported in the blood. Important that organs receive sufficient O2.
Types of solutions that help maintain a stable pH in the body.
Buffers
3 examples of Buffers
- bicarbonate
- proteins
- hemoglobin
System that ELIMINATES CO2 from body
Respiratory System
Increased respirations leads to
- CO2 elimination from body
- ↓ CO2 in blood
(respiratory alkalosis)
Decreased respirations leads to
- retained CO2
- ↑ CO2 in blood(respiratory acidosis)
System that excretes or retains bicarbonate (HCO3), hydrogen ions (H+), and electrolytes
Renal System
System that responds within minutes to hours.
Respiratory system
System that responds within hours to days
Renal System
What is the preferred site for obtaining an ABG sample.
radial or femoral artery.
What test will need to be performed if using the Radial artery to obtain an ABG sample?
Allen’s Test
* ensure adequate blood flow from both ulnar and radial artery to hand & body.
Steps for Allen’s Test:
- Elevate hand, make a fist for 20 seconds.
- Compress firmly on radial and ulnar arteries.
- Pt opens hand, hand should blanche (turn white)
- Examiner releases ONLY ulnar artery to ensure blood flow (hand turns pink again)
What materials and conditions are necessary for obtaining arterial blood samples?
- A heparinized syringe
- place syringe in ice
- prompt delivery to the lab.
Blood sample should include what 5 pieces of information?
- time drawn
- FiO2
- O2 delivery rate & method
-ventilator settings - patient temperature
- pulse O2 saturation
Method used to INTERPRET ABG’s
first, middle, and last name
First name is
- Whether systemic compensation has maintained a normal pH
- Compensate or Uncompensated?
Middle name is
- System causing the disturbance
- Respiratory or Metabolic?
Last name is
- Type of disturbance
- Acidosis or Alkalosis?
Interpretating ABG’s:
1st step is
Check for Hypoxemia - low O2 in BLOOD
- Normal PaO2 (O2 in BLOOD) = 80-100 mmHG
Hypoxemia is considered when PaO2 is
less than 80 mmHg
Highest priority with Hypoxemia
Establish airway and oxygenate!!
your ABC’s- KNOW
Interpretating ABG’s:
2nd step is to
Analyze pH
* Any disturbances?
Analyzing pH will give you
FIRST & LAST names
pH < 7.35
acidosis
pH > 7.45
alkalosis
if pH is NORMAL we call it
COMPENSATED
pH: 7.35-7.45
if pH is ABNORMAL we call it
Uncompensated
pH number that is considered “in the middle”
pH = 7.40
pH < 7.35 =
pH > 7.45 =
Acidosis
Alkalosis
3rd step is to find out Middle name by determining if
The PaCO2 levels are causing the problem?
or
The HCO3 levels are causing the problem?
Middle name:
If PaCO2 < 35 we say
Respiratory alkalosis.
Middle name:
If PaCO2 >45 we say
Respiratory acidosis.
Middle name*:
If HCO3 < 22 we call it
Metabolic acidosis
Middle name:
If HCO3 >26 we call it
Metabolic alkalosis
4th Step is to determine
ROME
(Respiratory Opposite, Metabolic Equal)
ROME:
If pH and PaCO2 go opposite ways we call it
Respiratory problem
- Respiratory acidosis: ↓ pH, ↑ PaCO2.
- Respiratory alkalosis: ↑ pH, ↓ PaCO2.
ROME:
If pH and HCO3 go the same way
Metabolic problem
- Metabolic acidosis: ↓ pH, ↓ HCO3.
- Metabolic alkalosis: ↑ pH, ↑ HCO3.
Step 5 we check compensation:
In Acidosis, the kidneys increase
HCO3 to compensate.
Respiratory Acidosis can occur due to:
List 6 causes
- Hypoventilation
- COPD
- over-sedation: depress CNS leading to slow breathing
- drug overdose
- neuromuscular diseases (resp. muscle weakness)
- head trauma.
Respiratory Acidosis:
pH and PaCO2 results
- pH < 7.35
- PaCO2 > 45 (retaining CO2)
Step 5 we check compensation:
In Alkalosis, the respiratory system retains
CO2 to compensate.
Respiratory Acidosis is ALWAYS due to
respiratory problems unable to remove CO2
How does the body compenssate in RESPIRATORY ACIDOSIS
Kidneys conserve HCO3- in the blood stream (does not excrete into urine) and excrete H+ into urine.
(H+ are acidic)
S/S of Respiratory Acidosis
SUDDEN Increase of:
- ↑ pulse
- ↑ respiratory rate
- ↑BP: speeds up CO2 circulation to lungs for removal
- Mental changes: feeling of fullness in the head
Interventions for Respiratory Acidosis
- Treat the underlying cause of acidosis
- Improve ventilation, maintain patent airway, give O2
What causes Respiratory Alkalosis?
Hyperventilation from:
- anxiety
- pain
- septicemia: serious bloodstream infection
- PE: blocks O2 to be received in lungs
- CNS lesions: affects respiratory center+
- severe anemia: less hgb to carry O2 to body
How does the body compensate during Respiratory Alkalosis
Rarely occurs because WE treat the underlying cause (hypoxemia) early and aggressively that the body doesnt have time to compensate.
* we treat hypoxemia bc pt starts to breath faster (getting rid of CO2 fast) leading to respiratory alkalosis
S/S of Respiratory Alkalosis
- Lightheadedness: low CO2 reduces blood flow to head
- inability to concentrate: low CO2 affects brain function
- numbness/tingling: more alkaline = affects Calcium levels & nervous system
- sometimes loss of consciousness
Interventions for Respiratory Alkalosis
- Slow down RR
- breathe into a paper bag- (rebreath the CO2 inside bag)
- reassess ventilator settings
- Treat the underlying cause.
pH and PaCO2 results in Respiratory Alkalosis
pH > 7.45
PaCO2 < 35.
What causes Metabolic Acidosis
Kidney injury due to:
- Diabetic ketoacidosis- most common
- renal failure
- severe diarrhea
- Anaerobic metabolism (shock)
- severe dehydration
- starvation
- Salicylate ingestions-aspirin overdose
- severe diarrhea
Remember: Vomit acid but poop base- if we poop all our base, then we become ACIDIC.
How does the body compensate in Metabolic Acidosis
- Lungs increase CO2 excretion
-
Kussmaul respirations: hyperventilation- deep and rapid to exhale CO2
-every-time we exhale, we get rid of CO2
S/S of Metabolic Acidosis
- Headache: ’A for Acid Affects the Brain’
- confusion
- drowsiness
- ↑ RR and ↑ depth
- ↓BP: acidic blood affects heart function
- dysrhythmias
pH and HCO3 results in Metabolic Acidosis
- pH < 7.35
- HCO3 < 22
What causes Metabolic Alkalosis
- Prolonged vomiting
- GI suctioning- *too high or not intermittent
- long-term diuretic therapy (hypokalemia)
- hypochloremia
-vomit acid, poop base
Interventions for Metabolic Acidosis
- Hydration
- antidiarrheal
- bicarbonate administration if needed.
- treat underlying cause (e.g., insulin for diabetic ketoacidosis, why are they hyperventilating in the 1st place?),
pH and HCO3 for Metabolic Alkalosis
- pH > 7.45
- HCO3 > 26
How does the body compensate for Metabolic Alkalosis
- Decreased respiratory rate to retain plasma CO2.
S/S of Metabolic Alkalosis
- Respiratory depression
- tachycardia
- hypokalemia
- hypocalcemia
Interventions for Metabolic Alkalosis
- Fluid and electrolyte replacement
- antiemetics
- modify gastric suctioning
