The pH scale, ranges from 0 (strongly acidic) to 14 (strongly basic or alkaline). A pH of 7.0, in the middle of this scale, is neutral. Blood is normally slightly basic, with a normal pH range of about 7.35 to 7.45. Usually the body maintains the pH of blood close to 7.40.

1. Acid-Base Balance
Review
Saunders Pyramid to Success

2. A Note About the NCLEX
• The National Council Licensure Examination (NCLEX) will not ask
specific questions about the pathophysiology associated with acid-
base disorders, such as the hydrogen ions, acids, bases, and the
regulatory systems for hydrogen ion concentration in the blood.
• In practice, however, understanding pathophysiology is essential
• See Chapter 10 of the Saunders Comprehensive Review for the NCLEX Examination for a
self-paced review.
• Review the following slides to prepare for the NCLEX.

3. Regulatory Systems
Five Strategic Points
1. When you hear or read the words hydrogen ions, think acids.
2. When you hear or read the words base or bicarbonate, think alkaline.
3. In acidosis, although hypoventilation may occur initially, the respiratory rate
and depth increase in an attempt to exhale acids.
4. In alkalosis, although hyperventilation may occur initially, the respiratory rate
and depth decrease; carbon dioxide is retained to neutralize and decrease the
strength of excess bicarbonate.
5. When the client experiences an acid-base imbalance, potassium moves in or
out of the cells in an attempt to maintain acid-base balance.
• In acidosis, hydrogen ions move into the cell and potassium moves out of
the cell; therefore the serum potassium level increases.
• In alkalosis, the opposite movement occurs. Hydrogen ions move out of
the cell and potassium moves into the cell; therefore the serum potassium
level decreases.

4. Focus on These Four Disorders
• Respiratory acidosis
• Respiratory alkalosis
• Metabolic acidosis
• Metabolic alkalosis

5. Focus on These Four Disorders, cont’d.
• What should you know?
• Causes of each disorder
• Clinical manifestations of each disorder
• Treatment for each disorder

6. Tips on Answering Questions About
Acid-Base Disorders
• How do you answer correctly if you are asked to determine which
acid-base disorder is expected to occur in a specific condition?
• Focus on the condition identified in the test question
• If the condition is a respiratory one then the answer is going to be a respiratory acid-base
disorder.
• If the condition is NOT a respiratory one then the answer will be a metabolic acid-base
disorder.
• How do you select correctly from the remaining options?
• Think about its pathophysiology of the condition presented and its effect on the body.

7. Sample Question 1
The nurse caring for a client with chronic obstructive pulmonary
disease, known as COPD*, monitors for which acid-base disorder that is
most likely to occur?
1. Respiratory acidosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Metabolic alkalosis
*Since the question identifies a respiratory condition you can easily
eliminate options 3 and 4 (the metabolic conditions).

8. Sample Question 1: Answer and
Rationale
• How do you select correctly from the remaining two options?
• Note the respiratory condition presented in the question (e.g. COPD).
• Think about its pathophysiology.
• The client with COPD loses elasticity of alveolar sacs restricting air
flow.
• These clients and those with emphysema, bronchiectasis, or bronchitis
develop inflammation causing airway obstruction.
• If the disorder causes an obstruction of the airways or depresses the
respiratory system, then the correct answer is respiratory acidosis.
• If the disorder causes overstimulation of the respiratory system, then the
correct answer is respiratory alkalosis.
• Correct answer: Respiratory Acidosis

9. Respiratory Acidosis
• What other conditions cause respiratory acidosis?
• Asthma – remember bronchiole spasm leads to airway constriction.
• Pneumonia or atelectasis because excess mucus production leads to airway
obstruction.
• Pulmonary edema because excess accumulation of fluid leads to airway
obstruction, and pulmonary emboli because the emboli cause airway
obstruction.
• Any central nervous system depressant such as sedatives, opioids, or
anesthetics can lead to respiratory acidosis because these depressants cause
hypoventilation.
• And finally, brain trauma because brain trauma causes pressure on the
respiratory center or medulla and depresses respirations.

10. Sample Question 2
The nurse would monitor a client who is being mechanically ventilated
for which acid-base disorder that is caused by overventilation*?
1. Respiratory acidosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Metabolic alkalosis
*Since the question identifies a respiratory condition you can easily
eliminate options 3 and 4 (the metabolic conditions).

11. Sample Question 2: Answer and
Rationale
• How do you select correctly from the remaining two options?
• Note the respiratory condition presented in the question (e.g.
overventilation).
• Think about its pathophysiology.
• If the disorder causes an obstruction of the airways or depresses the
respiratory system, then the correct answer is respiratory acidosis.
• If the disorder causes overstimulation of the respiratory system, then the
correct answer is respiratory alkalosis.
• Correct answer: Respiratory Alkalosis

12. Respiratory Alkalosis
• What other conditions cause respiratory alkalosis?
• Fever, because it increases metabolism, resulting in overstimulation of the
respiratory system.
• Hyperventilation or rapid respirations results in overstimulation of the
respiratory system.
• Hypoxic conditions will stimulate the respiratory center in the brainstem
causing hyperventilation.
• Hysteria, because it results in vigorous, fast breathing.
• Pain because it leads to overstimulation of the respiratory center in the
brainstem.

13. Summary of Respiratory Disorders
• If the client has a condition that causes an obstruction of the airway
or depresses the respiratory system, the client is at risk for respiratory
acidosis.
• If the client has a condition that causes overstimulation of the
respiratory system, the client is at risk for respiratory alkalosis.

14. Metabolic Acid-Base Disorders
• Metabolic acidosis results from an increased amount of hydrogen ions
or acids in the blood or a decrease in available base or bicarbonate
solution.
• Metabolic alkalosis results from an increased amount of available
base or bicarbonate solution in the blood or a decrease in available
hydrogen ions or acids.
• Again, note the condition identified in the test question. If the
condition identified in the question is NOT a respiratory one, then the
answer will be a metabolic acid-base disorder.

15. Sample Question 3
The nurse is caring for a client with gastroenteritis who is experiencing
severe diarrhea*. Which acid-base disorder is most likely to occur in
the client?
1. Respiratory acidosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Metabolic alkalosis
*Since the question DOES NOT identify a respiratory condition you can
easily eliminate options 1 and 2 (the respiratory conditions).

16. Sample Question 3: Answer and
Rationale
• How do you select correctly from the remaining two options?
• Note the metabolic condition presented in the question (e.g. severe diarrhea).
• Think about its pathophysiology.
• The client’s excess intestinal contents are being eliminated from the client’s body and intestinal
contents are highly alkaline.
• Metabolic acidosis results from an increased amount of hydrogen ions or acids in the
blood or a decrease in available base or bicarbonate solution.
• Metabolic alkalosis results from an increased amount of available base or
bicarbonate solution in the blood or a decrease in available hydrogen ions or acids.
• Therefore, since base or alkali substances are being removed, the client is at risk for
metabolic acidosis.
• Correct answer: Metabolic Acidosis

17. Metabolic Acidosis
• In addition to the loss of intestinal fluid, what other conditions cause
metabolic acidosis?
• Diabetic ketoacidosis – the insufficient supply of insulin leads to an excess
accumulation of ketones or other acids; the bicarbonate then ends up being
depleted.
• Excessive ingestion of acetylsalicylic acid (aspirin) increases the hydrogen ion
concentration.
• A high-fat diet causes a rapid accumulation of the waste products of fat metabolism,
leading to a buildup of ketones and acids.
• The insufficient metabolism of carbohydrates causes the production of lactic acid
resulting in lactic acidosis.
• The improper metabolism of nutrients that occurs in the client with malnutrition
causes fat catabolism, leading to an excess buildup of ketones and acids.
• Renal insufficiency or kidney failure causes the retention of waste products; acids
increase, and bicarbonate is unable to maintain acid-base balance.

18. Sample Question 4
The nurse is caring for a client with a nasogastric tube* attached to
continuous suction. The nurse should monitor for which acid-base
disorder that is most likely to occur?
1. Respiratory acidosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Metabolic alkalosis
*Since the question DOES NOT identify a respiratory condition you can
easily eliminate options 1 and 2 (the respiratory conditions).

19. Sample Question 4: Answer and
Rationale
• How do you select correctly from the remaining two options?
• Note the metabolic condition presented in the question (e.g. nasogastric tube
attached to continuous suction).
• Think about its pathology.
• Gastric contents are being suctioned out of the client’s body, and along with the gastric contents
are gastric acids.
• Metabolic acidosis results from an increased amount of hydrogen ions or acids in the
blood or a decrease in available base or bicarbonate solution.
• Metabolic alkalosis results from an increased amount of available base or
bicarbonate solution in the blood or a decrease in available hydrogen ions or acids.
• Therefore, since acids are being removed, the client is at risk for metabolic alkalosis.
• Correct answer: Metabolic Alkalosis

20. Metabolic Alkalosis
• In addition to suctioning gastric contents, what other conditions
cause metabolic alkalosis?
• Excessive vomiting because it leads to an excessive loss of gastric acid.
• Diuretics because their use results in a loss of hydrogen ions and an
accumulation of bicarbonate in the blood.
• The ingestion of and/or infusion of excess sodium bicarbonate, which causes
an increase in the amount of base in the blood.
• Hyperaldosteronism increases renal tubular reabsorption of sodium resulting
in a loss of hydrogen ions or acids.
• The client receiving massive transfusions of whole blood because the citrate
anticoagulant used for the storage of blood is metabolized to bicarbonate.

21. Summary of Metabolic Disorders
• If the client has a condition that will result in an increased amount of
hydrogen ions or acids in the blood or a decrease in available base or
bicarbonate solution, the client is at risk for metabolic acidosis.
• If the client has a condition that will result in an increased amount of
available base or bicarbonate solution in the blood or a decrease in
available hydrogen ions or acids, the client is at risk for metabolic
alkalosis.

22. Manifestations
Respiratory and Metabolic Acidosis Disorders
• Manifestations for both respiratory and metabolic acidosis disorders
are similar.
• Neurological system: manifestations such as drowsiness, disorientation,
confusion, headache, and coma may occur.
• Cardiovascular system: blood pressure decreases, dysrhythmias occur, and
the skin becomes warm and flushed because of vasodilation.
• Respiratory system: although hypoventilation may occur initially, the
respiratory rate and depth will increase in an attempt to exhale acids.

23. Manifestations
Respiratory and Metabolic Alkalosis Disorders
• Manifestations for both respiratory and metabolic alkalosis disorders
are similar.
• Neurological system: manifestations such as drowsiness, dizziness, and
confusion may occur
• Cardiovascular system: tachycardia and dysrhythmias occur.
• Gastrointestinal system: anorexia, nausea, and vomiting can occur.
• Respiratory system: although hyperventilation may occur initially, the
respiratory rate and depth decrease. Carbon dioxide is then retained to
neutralize and decrease the strength of excess bicarbonate.

24. Treatment
• There are some general treatment measures that apply to all types of
acid-base disorders.
• Also, remember that treatment is based on the cause of the disorder.
• Monitoring airway patency
• Monitoring respirations
• Monitoring vital signs
• Monitoring laboratory results

25. Treatment: Examples
• Examples:
• If the client is experiencing airway obstruction from accumulated secretions
and is experiencing respiratory acidosis then respiratory treatments will be
instituted to loosen and remove these secretions to alleviate the obstruction.
• If the client is experiencing respiratory alkalosis because of a fever, then
treatments will be instituted to reduce the fever.
• If vomiting is the cause of metabolic alkalosis, then measures will be
instituted to alleviate the vomiting.
• If the cause of metabolic acidosis is diabetic ketoacidosis then intravenous
normal saline and regular insulin will be initiated.

26. Summary: Clinical Manifestations and
Treatments
• In acidosis, although hypoventilation may occur initially, the
respiratory rate and depth increase in an attempt to exhale acids.
• In alkalosis, although hyperventilation may occur initially, the
respiratory rate and depth decrease. Carbon dioxide is then retained
to neutralize and decrease the strength of excess bicarbonate.
• The cause of the disorder is the focus for treatment.

27. Analyzing an Arterial Blood Gas Result
• NCLEX may test your ability to analyze an arterial blood gas result.
• The following slides review some strategic Pyramid Points and
Pyramid Steps.
• If you remember these points and use these steps you will be able to
analyze any blood gas report.

28. Normal Arterial Blood Gas Values
• pH
• 7.35-7.45
• partial pressure of carbon dioxide (PCO2)
• 35-45 millimeters of mercury (mmHg)
• HCO3
- or the bicarbonate
• 22-27 mEq/L
• partial pressure of oxygen (PO2)
• 80-100 mmHg
Note: mmHg will be used hereafter, as will PCO2, HCO3
- and PO2

29. Pyramid Points
• In acidosis, the pH is decreased.
• In alkalosis, the pH is elevated.

30. Pyramid Steps: Step 1
 Look at the pH.
 Is the pH elevated or decreased?
 If the pH is elevated, it reflects alkalosis.
 If the pH is decreased, it reflects acidosis.

31. Pyramid Steps: Step 2
 Look at the PCO2.
 Is the PCO2 elevated or decreased?
 If the PCO2 reflects an opposite relationship to the pH, then you know
that the condition is a respiratory imbalance.
 If the PCO2 does not reflect an opposite relationship to the pH, then
move on to Pyramid Step 3.

32. Pyramid Steps: Step 3
 Look at the HCO3
-.
 Does the HCO3
- reflect a corresponding relationship with the pH?
 If it does, then the condition is a metabolic imbalance.

33. Pyramid Steps: Step 4
 Compensation has occurred if the pH is in a normal range of 7.35 to
7.45.
 The condition is uncompensated if the pH is NOT in a normal range of
7.35 to 7.45.

34. Practice Question 1
Arterial blood gas values:
pH of 7.30
pCo2 of 50 mm Hg
HCO3
- of 27 mEq/L
PO2 of 85 mm Hg
• Pyramid Step 1: Look at the pH. Is the pH elevated or decreased? The pH of 7.30 is
decreased, therefore it reflects acidosis.
• Pyramid Step 2: Look at the PCO2. Is the PCO2 elevated or decreased? The PCO2 of 50
mmHg reflects an opposite relationship to the pH, so you know that the condition is a
respiratory imbalance.
• Initial conclusion: this condition is respiratory acidosis.
• Note that the pH of 7.30 is not within the normal range. Therefore the condition is
uncompensated.
• Final conclusion: these blood gas values identify respiratory acidosis, uncompensated.

35. Practice Question 2
Arterial blood gas values:
pH of 7.50
pCo2 of 50 mm Hg
HCO3
- of 30 mEq/L
PO2 of 90 mm Hg
• Pyramid Step 1: Look at the pH. Is the pH elevated or decreased? The pH of 7.50 is elevated,
therefore it reflects alkalosis.
• Pyramid Step 2: Look at the PCO2. Is the PCO2 elevated or decreased? The PCO2 of 50 mmHg is
elevated and reflects the same relationship to the pH, so you know that the condition is NOT a
respiratory imbalance.
• Pyramid Step 3: Look at the HCO3
- and note that it is elevated at 30 mEq/L and therefore reflects a
corresponding relationship with the pH. Thus, the condition is a metabolic imbalance.
• Initial conclusion: this condition is metabolic alkalosis.
• Note that the pH is not within the normal range. Therefore the condition is uncompensated.
• Final conclusion: these blood gas values identify metabolic alkalosis, uncompensated.

36. Conclusion
• This ends the acid-base balance review.
• I encourage you to continue reviewing these slides and to review
Chapter 10 of the Saunders Comprehensive Review for the NCLEX
Examination.
• This chapter provides you with additional information about acid-base
disorders and practice questions.
• The Evolve site accompanying the Saunders Comprehensive Review for the
NCLEX Examination will also provide you with these types of questions if you
select Fundamental Skills: Acid-Base
• I wish you the best of luck on your nursing exams and on the NCLEX!