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Questions and Answers
What is the primary regulator of acid-base balance?
What is the primary regulator of acid-base balance?
Buffer system
What is the normal pH range of blood?
What is the normal pH range of blood?
Match the following blood gas values with their normal reference intervals:
Match the following blood gas values with their normal reference intervals:
pH = 7.35 - 7.45 PaCO2 = 35 - 45 mm of Hg Bicarbonate (HCO3− ) = 22 – 26 mEq/L PaO2 = 80 – 100 mm of Hg SaO2 = >95%
______ excretion is one of the mechanisms for acid excretion in the renal system.
______ excretion is one of the mechanisms for acid excretion in the renal system.
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Respiratory alkalosis can be caused by hyperventilation.
Respiratory alkalosis can be caused by hyperventilation.
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What imbalance is indicated by the following ABG results: pH 7.60, PaCO2 30 mm Hg, PaO2 60 mm Hg, HCO3− 22 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.60, PaCO2 30 mm Hg, PaO2 60 mm Hg, HCO3− 22 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.28, PaCO2 28 mm Hg, PaO2 70 mm Hg, HCO3− 18 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.28, PaCO2 28 mm Hg, PaO2 70 mm Hg, HCO3− 18 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.33, PaCO2 67 mm Hg, PaO2 47 mm Hg, HCO3− 37 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.33, PaCO2 67 mm Hg, PaO2 47 mm Hg, HCO3− 37 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.50, PaCO2 28 mm Hg, PaO2 85 mm Hg, HCO3− 24 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.50, PaCO2 28 mm Hg, PaO2 85 mm Hg, HCO3− 24 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.39, PaCO2 38 mm Hg, PaO2 44 mm Hg, HCO3− 24 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.39, PaCO2 38 mm Hg, PaO2 44 mm Hg, HCO3− 24 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.57, PaCO2 46 mm Hg, PaO2 87 mm Hg, HCO3− 38 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.57, PaCO2 46 mm Hg, PaO2 87 mm Hg, HCO3− 38 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.37, PaCO2 59.8 mm Hg, PaO2 87 mm Hg, HCO3− 34.5 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.37, PaCO2 59.8 mm Hg, PaO2 87 mm Hg, HCO3− 34.5 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.38, PaCO2 28 mm Hg, PaO2 92 mm Hg, HCO3− 18.5 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.38, PaCO2 28 mm Hg, PaO2 92 mm Hg, HCO3− 18.5 mEq/L?
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What imbalance is indicated by the following ABG results: pH 7.53, PaCO2 29.8 mm Hg, PaO2 82 mm Hg, HCO3− 25.6 mEq/L?
What imbalance is indicated by the following ABG results: pH 7.53, PaCO2 29.8 mm Hg, PaO2 82 mm Hg, HCO3− 25.6 mEq/L?
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A patient with ABG results: pH 7.48, PaO2 86 mm Hg, PaCO2 44 mm Hg, HCO3− 29 mEq/L would be expected to have:
A patient with ABG results: pH 7.48, PaO2 86 mm Hg, PaCO2 44 mm Hg, HCO3− 29 mEq/L would be expected to have:
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Study Notes
Acid-Base Balance
- The body needs to maintain a steady balance between acids and bases to achieve homeostasis.
- Health problems such as diabetes, chronic obstructive pulmonary disease (COPD), and kidney disease can lead to an imbalance.
pH
- pH is a measure of H+ ion concentration.
- An increase in H+ concentration leads to acidity, while a decrease in H+ concentration leads to alkalinity.
- The normal pH range of blood is slightly alkaline, between 7.35 and 7.45.
Acid-Base Regulation
- There are three mechanisms to regulate acid-base balance and maintain a pH between 7.35 and 7.45:
- Buffer system
- Respiratory system
- Renal system
Buffer System
- The buffer system is the primary regulator of acid-base balance.
- It acts chemically to change strong acids into weak acids or binds acids to neutralize them.
- The buffer system requires the respiratory and renal systems to be functioning adequately.
Carbonic Acid (H2CO3)/Bicarbonate (HCO3–) Buffer
- This is the major buffer system.
- The reaction is: HCl + NaHCO3 → NaCl + H2CO3.
- The carbonic acid (H2CO3) is broken down into water (H2O) and carbon dioxide (CO2).
- The lungs excrete CO2.
Other Buffer Systems
- Phosphate buffer system
- Protein buffer system
- Hemoglobin buffer system
- Cellular buffer system, which shifts H+ in and out of cells in exchange for potassium.
Respiratory System Regulation
- The respiratory system regulates acid-base balance through the reaction: CO2 + H2O → H2CO3 → H+ + HCO3–.
- The respiratory center in the medulla controls breathing.
- Increased respirations lead to increased CO2 elimination and decreased CO2 in the blood.
- Decreased respirations lead to CO2 retention.
Renal System Regulation
- The renal system conserves bicarbonate and excretes some acid through three mechanisms:
- Secreting free hydrogen ions
- Combining H+ with ammonia (NH3)
- Excreting weak acids
Alterations in Acid-Base Balance
- Imbalances occur when compensatory mechanisms fail.
- Classification of imbalances:
- Respiratory (CO2) or metabolic (HCO3–)
- Acidosis or alkalosis
- Acute or chronic
Blood Gas Values
- Arterial blood gas (ABG) values give objective information about:
- Acid-base status
- Underlying cause of imbalance
- Body's ability to regulate pH
- Overall oxygenation status
Normal Arterial Blood Gas Values
- pH: 7.35 - 7.45
- PaCO2: 35 - 45 mm Hg
- Bicarbonate (HCO3–): 22 - 26 mEq/L
- PaO2: 80 - 100 mm Hg
- SaO2: >95%
- Base excess: + 2.0 mEq/L
Interpretation of ABGs
- Look at each of the values
- Look at pH first
- Use ROME to determine respiratory or metabolic
- Determine if the patient is compensating
- Assess the PaO2 and O2 saturation
Acid-Base Mnemonic—ROME
- Respiratory Opposite (RO): Alkalosis ↑ pH ↓ PaCO2, Acidosis ↓ pH ↑ PaCO2
- Metabolic Equal (ME): Acidosis ↓ pH ↓ HCO3–, Alkalosis ↑ pH ↑ HCO3–
Case Studies
- Jeri, a 22-year-old female, with respiratory acidosis due to hypoventilation secondary to alcohol ingestion.
- Mayna, an 18-year-old female, with respiratory alkalosis due to hyperventilation secondary to anxiety and hysteria.
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Description
Learn about the importance of maintaining a balance between acids and bases in the body to achieve homeostasis, and how health problems like diabetes, COPD, and kidney disease can lead to imbalance.
