38 Questions
Which of the following correctly describes the main buffer systems in the human body?
Bicarbonate, phosphate, and protein buffers
What is the primary compensatory mechanism for metabolic acidosis?
Increased bicarbonate reabsorption in the kidneys
Which condition is characterized by a pH above 7.45 and is considered an alkalotic state?
Metabolic alkalosis
What is a common cause of respiratory alkalosis?
Hyperventilation
Which of the following disorders can result in tissue hypoxia due to inadequate oxygen delivery?
Anemia
What is the main function of kidneys in relation to acid-base balance?
Removing fixed acids from the body
Which of the following is NOT one of the three major acid-base buffer systems in the blood?
Sulfuric acid-Sulfate System
Which buffer system is identified as the major buffer of interstitial fluid?
Bicarbonate buffer system
During respiratory correction of an acid-base imbalance, what triggers an increase in ventilation rate?
Stimulation of peripheral chemoreceptors
How does renal compensation for acidosis primarily occur?
By retaining fixed acids and excreting HCO3
Which of the following statements accurately differentiates between uncompensated respiratory acidosis and uncompensated metabolic acidosis?
Uncompensated respiratory acidosis involves changes in plasma [HCO3-], whereas plasma [HCO3-] is unchanged in uncompensated metabolic acidosis
In the scenario provided, a 48-year-old man presents with decreased LOC and the following arterial blood gas results: pH 7.25, PaCO2 25, PaO2 62, HCO3- 15. What is the most likely cause of these abnormalities?
Diabetic ketoacidosis
When a 65-year-old female with hemorrhagic shock and active GI bleed experiences a decrease in blood pressure following intubation for aspiration prevention, what is the most likely cause of her hypotension?
Decrease in venous return
What is the normal range for pH in the blood?
7.35-7.45
How does hyperventilation affect blood pH?
Causes an increase in blood pH
Which of the following is NOT a cause of respiratory alkalosis?
Hypoventilation
In metabolic acidosis, what is the primary cause?
Loss of bicarbonate ions
What is the consequence of impaired alveolar ventilation in respiratory acidosis?
Acute decrease in blood pH
What does a large anion gap in acidosis indicate?
Increased plasma concentration of anions other than bicarbonate
How does the body compensate for acidosis?
Decreases PaCO2
What is the typical range for the anion gap in the body?
8-12 mEq/L
Which condition could lead to non-anion gap acidosis?
Diarrhea
What can lead to metabolic alkalosis according to the text?
Ingestion of bases
What is the formula for calculating pH in a solution?
pH = - log [H+]
At what pH range does acidosis/acidemia occur in the body?
Below 7.35
Which of the following is a common mechanism for compensating acidosis in the body?
Increased exhalation of CO2 by the lungs
What pH range characterizes alkalosis/alkalemia in the body?
Above 7.45
Under pathologic conditions, what is the allowed pH range in the body?
6.9-7.8
What is the role of the bicarbonate buffer system in maintaining blood pH?
Neutralize excessive amounts of acid to decrease blood pH
How does the renal compensation for alkalosis differ from compensation for acidosis?
Decreased H+ secretion and increased HCO3- reabsorption
Which acidic compounds can contribute to acidosis if ingested excessively?
Acetoacetic acid and b-hydroxybutyric acid
What is the main factor that determines the value of a buffer system in maintaining blood pH?
Availability of the buffer system
How does the isohydric principle relate to the equilibrium of buffer pairs?
It states that all buffer pairs are always in equilibrium regardless of pH changes
What is the effect of renal compensation on H+ secretion during acidosis?
Increased H+ secretion
Which mechanism contributes to the removal of titratable acids like ketoacids from the body?
[HCO3-] reabsorption in peritubular capillaries
In which scenario would renal compensation lead to decreased HCO3- reabsorption?
[HCO3-] reabsorption in peritubular capillaries decreases
How do ketoacids contribute to acid-base imbalances in the body?
[HCO3-] reabsorption decreases
Which process occurs during glutamine metabolism that contributes to acid-base regulation?
Ammonia secreted in exchange for [HCO3-]
Study Notes
Chemistry of Acids, Bases, and Buffers
- An acid is a molecule that releases a hydrogen ion (proton) in solution
- A base is a molecule that can accept a hydrogen ion in solution; a strong base
- A strong acid completely dissociates; a weak acid has a strong conjugate base
pH Regulation
- pH is a measure of the [H+] in a solution, and is expressed by the formula pH = - log [H+]
- Regulation of acid-base balance is equivalent to regulation of [H+] in body fluids
- Body attempts to regulate blood pH to 7.40
- pH limits under pathologic conditions = 6.9- 7.8
- Acidosis/acidemia occurs at a pH < 7.35
- Alkalosis/alkalemia occurs at a pH > 7.45
Buffer Systems of the Body
- Three mechanisms that resist pH changes are:
- Lungs remove volatile acids- ~20,000 mmol CO2/day
- Kidneys remove fixed acids- ~ 100 mEq/day
- Buffers reversibly bind hydrogen ions to minimize changes in H+ concentration/ pH
Bicarbonate Buffer System
- Major buffer system in the body
- H2CO3 + H2O → H+ + HCO3-
- Increased CO2 production leads to increased H+ ions in venous blood, making it slightly more acidic (pH 7.35 vs 7.4)
Phosphate Buffer System
- Weaker than the bicarbonate system
- 2 components – H2PO4- (dihydrogen phosphate- acid) and HPO42- (monophosphate- conjugate base)
- High intracellularly
Respiratory Regulation of Acid-Base Balance
- Respiratory system assists in regulation of pH in terms of [H+]
- Hyperventilation causes respiratory alkalosis - a loss of CO2 [H+], resulting in an increase in blood pH
- Hypoventilation causes respiratory acidosis - an increase of [H+], resulting in a decrease in blood pH
Acid-Base Abnormalities
- Acid-base abnormalities produce changes in pH, PCO2, and plasma bicarbonate
- Respiratory acidosis:
- Causes: Increased CO2 production, Decreased CO2 elimination, Rebreathing
- Consequences: Increased PCO2, Decreased pH
- Respiratory alkalosis:
- Causes: Alveolar ventilation exceeds CO2 production
- Consequences: Decreased PCO2, Increased pH
- Metabolic acidosis:
- Causes: Ingestion, infusion, or overproduction of H+ ions, or a loss of bicarbonate ions
- Consequences: Decreased pH, Decreased HCO3-
- Metabolic alkalosis:
- Causes: Ingestion, infusion, or excessive renal reabsorption of bases, or loss of hydrogen ions
- Consequences: Increased pH, Increased HCO3-
Compensation Mechanisms
- Respiratory compensation:
- Increased ventilation to eliminate excess CO2
- Decreased ventilation to retain CO2
- Renal compensation:
- Increased excretion of fixed acids and conservation of HCO3-
- Decreased excretion of fixed acids and increased excretion of HCO3-
Test your knowledge on comparing uncompensated respiratory acidosis (URA) and uncompensated metabolic acidosis (UMA). Learn about the differences in plasma pH change, compensation mechanisms, and changes in plasma [HCO3-] between the two conditions.
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