ABG imbalance interpretation
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NRS 400
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137 Terms
What is the normal pH range?
7.35–7.45.
What does a pH below 7.35 indicate?
Acidosis.
What does a pH above 7.45 indicate?
Alkalosis.
What is the normal PaCO2 range?
35–45 mmHg.
What is the normal HCO3- range?
22–26 mEq/L.
What is the normal PaO2 range in this lecture?
83–108 mmHg.
What does HCO3- represent in acid-base balance?
The base component and the metabolic system.
What body system regulates CO2?
The lungs/respiratory system.
What body system regulates HCO3-?
The kidneys/metabolic system.
What is the buffer system?
The primary regulator of acid/base balance; it helps neutralize or weaken excess acid.
What is compensation?
The body trying to push the pH back toward normal.
If the primary problem is respiratory, which system compensates?
The kidneys.
If the primary problem is metabolic, which system compensates?
The lungs.
What do the kidneys adjust when compensating for a respiratory problem?
HCO3-.
What do the lungs adjust when compensating for a metabolic problem?
CO2.
What does ROME stand for?
Respiratory Opposite; Metabolic Equal.
What does Respiratory Opposite mean?
pH and CO2 move in opposite directions.
What does Metabolic Equal mean?
pH and HCO3- move in the same direction.
How do pH and HCO3- move?
They move together.
How do pH and CO2 move?
They move in opposite directions.
What is the first step in interpreting an ABG?
Look at the pH.
What is the second step after identifying pH?
Determine whether the pH indicates acidosis or alkalosis.
What should be assessed after pH?
Determine what CO2 and HCO3- are doing.
What is the purpose of the Tic-Tac-Toe method?
To systematically interpret pH, CO2, and HCO3- and identify the primary acid-base disturbance.
What is the first step of the alternate Tic-Tac-Toe method?
Set up the grid.
What is the second step of the alternate Tic-Tac-Toe method?
Analyze each lab value: pH, CO2, and HCO3-.
What does CO2 equal in the Tic-Tac-Toe method?
CO2 = acid and CO2 = respiratory system.
What does HCO3- equal in the Tic-Tac-Toe method?
HCO3- = base and HCO3- = metabolic system.
What is the third step of the alternate Tic-Tac-Toe method?
Interpret the results.
What does it mean if values line up in a row on the Tic-Tac-Toe grid?
The primary acid/base disturbance has been identified.
What is uncompensated?
Abnormal pH, one abnormal CO2 or HCO3- value, and one normal value; the imbalanced system has not started to compensate.
What is partially compensated?
Abnormal pH with two abnormal values; the imbalanced system and the system trying to compensate are both abnormal.
What is fully compensated?
Normal pH with two abnormal values; the original imbalanced system and the compensating system are both abnormal.
What is respiratory acidosis?
The lungs retain too much CO2 because of hypoventilation, causing a buildup of H+ ions.
How do the kidneys compensate for respiratory acidosis?
They excrete excess H+ ions and retain HCO3-.
What causes of respiratory acidosis are listed?
Oversedation, CNS depression, drug overdose, stroke, chronic COPD, ALS, muscular dystrophy, myasthenia gravis, Guillain-Barré, and respiratory distress.
What ABG pattern indicates respiratory acidosis?
Low pH and high PaCO2.
What signs/symptoms are listed for respiratory acidosis?
Decreased respirations, tachycardia, hypotension, cyanosis, anxiety, dizziness, impaired coordination, and decreased LOC.
What interventions are listed for respiratory acidosis?
Correct the underlying cause, semi-High Fowler’s, good pulmonary hygiene, oxygen or ventilation, and IV bicarbonate drip.
What is metabolic acidosis?
The kidneys lose excess HCO3- and retain too much H+ ions.
How do the lungs compensate for metabolic acidosis?
They blow off more CO2 to lower H+ ions.
What causes of metabolic acidosis are listed?
Shock states, DKA, dehydration, renal failure, starvation, excessive diarrhea, and laxative overuse.
What ABG pattern indicates metabolic acidosis?
Low pH and low HCO3-.
What signs/symptoms are listed for metabolic acidosis?
Tachycardia, hypotension, Kussmaul respirations, altered mental status, and dysrhythmias.
What interventions are listed for metabolic acidosis?
Correct the underlying cause, bicarbonate drip, isotonic IV fluids, correct electrolytes, treat heart rhythms, and dialysis.
What is respiratory alkalosis?
The lungs lose too much CO2 because of hyperventilation; the lecture describes a buildup of HCO3-.
How do the kidneys compensate for respiratory alkalosis?
They excrete excess HCO3- and retain H+ ions.
What causes of respiratory alkalosis are listed?
Anxiety, panic attacks, head injuries, high altitude, pain, infection, stress, acute asthma attacks, acute COPD exacerbation, and laboring mothers.
What ABG pattern indicates respiratory alkalosis?
High pH and low PaCO2.
What signs/symptoms are listed for respiratory alkalosis?
Tachycardia, dizziness, headache, lightheadedness, dry mouth, wheezing, chest pain, low calcium, Chvostek’s sign, rhythm changes, and seizures.
What interventions are listed for respiratory alkalosis?
Correct the underlying cause, brown bag breathing, slow breathing, anxiety medications/benzodiazepines, correct electrolytes, and monitor for seizures.
What is metabolic alkalosis?
The kidneys lose excess H+ ions and retain too much HCO3-.
How do the lungs compensate for metabolic alkalosis?
They attempt to retain CO2, raising H+ ions and lowering HCO3-.
What causes of metabolic alkalosis are listed?
Overuse of antacids or steroids, excessive vomiting, bulimia, TPN, Cushing’s syndrome, NG tube suctioning, potassium wasting, diuretics such as furosemide, and massive blood transfusions.
What ABG pattern indicates metabolic alkalosis?
High pH and high HCO3-.
What signs/symptoms are listed for metabolic alkalosis?
Tachycardia, decreased respiratory rate/hypoventilation, low calcium, low potassium, and heart rhythm changes.
What interventions are listed for metabolic alkalosis?
Correct the underlying cause, NIV management, isotonic IV fluids, correct electrolytes, monitor for seizures, and correct heart rhythms.
What acid-base imbalance is associated with septic shock?
Metabolic acidosis.
What acid-base imbalance is associated with DKA?
Metabolic acidosis.
What acid-base imbalance is associated with respiratory failure?
Respiratory acidosis.
What acid-base pattern can PE cause according to the lecture?
Respiratory alkalosis progressing to acidosis.
What acid-base imbalance can cardiogenic shock cause?
Metabolic acidosis from tissue hypoperfusion.
What acid-base imbalance is associated with AKI?
Metabolic acidosis.
What acid-base effect is associated with mechanical ventilation in the lecture?
Respiratory compensation.
What is the relationship between hypoventilation and respiratory acidosis?
Hypoventilation retains CO2, producing respiratory acidosis.
What is the relationship between hyperventilation and respiratory alkalosis?
Hyperventilation blows off CO2, producing respiratory alkalosis.
A patient is oversedated and has decreased respirations. What imbalance should the nurse anticipate?
Respiratory acidosis.
A patient with an opioid overdose has decreased respirations. What imbalance should the nurse anticipate?
Respiratory acidosis.
A patient with COPD develops worsening hypoventilation. What imbalance should the nurse anticipate?
Respiratory acidosis.
A patient with DKA develops an acid-base imbalance. What should the nurse anticipate?
Metabolic acidosis.
A patient with severe diarrhea develops an acid-base imbalance. What should the nurse anticipate?
Metabolic acidosis.
A patient with renal failure develops an acid-base imbalance. What should the nurse anticipate?
Metabolic acidosis.
A patient with anxiety is hyperventilating. What imbalance should the nurse anticipate?
Respiratory alkalosis.
A patient has a panic attack with hyperventilation. What imbalance should the nurse anticipate?
Respiratory alkalosis.
A patient at high altitude is hyperventilating. What imbalance should the nurse anticipate?
Respiratory alkalosis. A laboring patient is hyperventilating.
A patient has prolonged vomiting. What imbalance should the nurse anticipate?
Metabolic alkalosis.
A patient has excessive NG tube suctioning. What imbalance should the nurse anticipate?
Metabolic alkalosis.
A patient taking furosemide develops an acid-base imbalance. What should the nurse anticipate?
Metabolic alkalosis.
A patient has low pH and high PaCO2. Which system is primarily responsible?
The respiratory system; respiratory acidosis.
A patient has low pH and low HCO3-. Which system is primarily responsible?
The metabolic system; metabolic acidosis.
A patient has high pH and low PaCO2. Which system is primarily responsible?
The respiratory system; respiratory alkalosis.
A patient has high pH and high HCO3-. Which system is primarily responsible?
The metabolic system; metabolic alkalosis.
What does PaO2 help determine?
Whether the patient is hypoxic or not.
What PaO2 value is below the normal range used in this lecture?
Any value below 83 mmHg.
What PaO2 value is within the normal range used in this lecture?
83–108 mmHg.
What does an abnormal pH with one abnormal CO2 or HCO3- value suggest?
Uncompensated.
What does an abnormal pH with two abnormal values suggest?
Partial compensation.
What does a normal pH with two abnormal values suggest?
Full compensation.
What is the ABG example: pH 7.2, PaCO2 53, HCO3- 23, PaO2 82?
Respiratory acidosis, noncompensating, hypoxic.
Why is pH 7.2 acidotic?
It is below 7.35.
Why does PaCO2 53 support respiratory acidosis?
It is above the normal 35–45 mmHg range.
Why does HCO3- 23 indicate no metabolic compensation in that example?
It is within the normal 22–26 mEq/L range.
Why is PaO2 82 labeled hypoxic in the lecture?
It is below the normal 83–108 mmHg range.
What is the ABG example: pH 7.22, PaCO2 53, HCO3- 30, PaO2 85?
Respiratory acidosis with partial compensation and not hypoxic.
Why is pH 7.22 partially compensated?
The pH remains abnormal while both PaCO2 and HCO3- are abnormal.
What is the ABG example: pH 7.37, PaCO2 51, HCO3- 33, PaO2 88?
Respiratory acidosis with full compensation and not hypoxic.
Why is pH 7.37 fully compensated?
The pH is normal while both PaCO2 and HCO3- are abnormal.
What is the practice ABG: pH 7.28, PaCO2 72, HCO3- 25, PaO2 82?
Respiratory acidosis, noncompensating, hypoxic.
What is the practice ABG: pH 7.30, PaCO2 36, HCO3- 20, PaO2 94?
Metabolic acidosis, noncompensating, not hypoxic.
What is the practice ABG: pH 7.46, PaCO2 48, HCO3- 29, PaO2 87?
Metabolic alkalosis, partial compensation, not hypoxic.