Metabolic Alkalosis and Renal Compensation
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Questions and Answers

What happens to bicarbonate reabsorption from tubules during raised pCO2 levels?

More HCO3– are reabsorbed from the tubules in response to raised pCO2 levels.

How is metabolic alkalosis defined biochemically?

Metabolic alkalosis is characterized by an absolute or relative increase in [HCO3–].

What biochemical changes occur during uncompensated metabolic disorders?

There is a disproportionate increase in [H2CO3], along with increased [HCO3–] and total CO2 content.

What role do kidneys play in response to increased pCO2?

<p>The kidneys reabsorb more HCO3– to manage elevated pCO2 levels.</p> Signup and view all the answers

Identify a condition that can cause suppression of respiration affecting CO2 levels.

<p>Brain damage due to trauma is one condition that can suppress respiration.</p> Signup and view all the answers

What happens to urinary NH3 and titratable acidity in compensated metabolic alkalosis?

<p>Urinary NH3 and titratable acidity are both increased.</p> Signup and view all the answers

How does metabolic alkalosis affect the respiratory center (RC)?

<p>Metabolic alkalosis inhibits the respiratory center, leading to shallow and irregular breathing.</p> Signup and view all the answers

What is the primary cause of clinically observed metabolic alkalosis?

<p>The primary cause is an increase in the 'alkali reserve' or excess HCO3–.</p> Signup and view all the answers

What is the effect of decreased ventilation on pCO2 and respiratory compensation?

<p>Decreased ventilation raises pCO2, which stimulates respiratory compensation.</p> Signup and view all the answers

What happens to cation and HCO3– excretion during renal compensation?

<p>Cation and HCO3– excretion increase due to decreased H+-Na+ exchange.</p> Signup and view all the answers

List one compensatory mechanism in response to alkalosis.

<p>Increased alkali excretion is one compensatory mechanism.</p> Signup and view all the answers

How does alkalosis affect urinary acidity?

<p>Urinary acidity decreases and there is a decrease in NH3 formation.</p> Signup and view all the answers

What biochemical changes occur in hypokalaemia during alkalosis?

<p>Increased excretion of K+ can lead to K+ depletion or hypokalaemia.</p> Signup and view all the answers

What characterizes uncompensated metabolic alkalosis biochemically?

<p>It is characterized by disproportionate increases in [HCO3–], pCO2, and total CO2 content.</p> Signup and view all the answers

What occurs in fully compensated metabolic alkalosis regarding [HCO3–] and [H2CO3]?

<p>In fully compensated alkalosis, [HCO3–] and [H2CO3] increase proportionately.</p> Signup and view all the answers

Describe the urinary findings in fully compensated metabolic alkalosis.

<p>Decreases in urinary NH3 and titratable acidity are observed.</p> Signup and view all the answers

What causes metabolic acidosis?

<p>Metabolic acidosis is caused by a reduction in plasma HCO3– leading to a decrease in the pH.</p> Signup and view all the answers

Describe the role of the respiratory center in the primary compensatory mechanism for acidosis.

<p>The respiratory center is stimulated by acidosis, causing deep and rapid breathing to increase ventilation and reduce CO2 levels.</p> Signup and view all the answers

What is the ratio of [HCO3–] to [H2CO3] during metabolic acidosis?

<p>The ratio is decreased from the normal 20:1.</p> Signup and view all the answers

What happens to pCO2 during the primary compensatory mechanism for acidosis?

<p>pCO2 levels decrease due to increased ventilation.</p> Signup and view all the answers

In uncompensated acidosis, what happens to the concentration of H+ ions?

<p>The concentration of H+ ions in the blood increases.</p> Signup and view all the answers

What renal mechanisms are employed during compensatory responses to metabolic acidosis?

<p>Renal mechanisms include conserving cations, increasing NH3 formation, H+ excretion, and HCO3– reabsorption.</p> Signup and view all the answers

What is the difference between compensated and uncompensated phases of acid-base imbalance?

<p>In compensated phase, the body actively corrects the imbalance, while in uncompensated phase, these compensatory mechanisms fail.</p> Signup and view all the answers

Explain the two opposing forces in respiratory compensation during acidosis.

<p>Acidosis stimulates the respiratory center while low pCO2 depresses it, creating a partial compensatory effect.</p> Signup and view all the answers

What are the biochemically characteristic changes in uncompensated metabolic alkalosis?

<p>In uncompensated metabolic alkalosis, there is a disproportionate decrease in [H2CO3] and pCO2, a decrease in [HCO3–], a decrease in CO2 content, an increase in the [HCO3–] : [H2CO3] ratio, and an increase in pH.</p> Signup and view all the answers

How does fully compensated metabolic alkalosis differ from uncompensated?

<p>Fully compensated metabolic alkalosis has low CO2 content with proportionate decreases in [HCO3–] and [H2CO3], and maintains normal limits for the [HCO3–] : [H2CO3] ratio and pH.</p> Signup and view all the answers

What urinary findings suggest normal kidney function during metabolic alkalosis?

<p>In metabolic alkalosis with normal kidney function, urinary NH3 and titratable acidity both decrease.</p> Signup and view all the answers

List two causes of respiratory alkalosis and their mechanisms.

<p>Two causes of respiratory alkalosis are CNS diseases, like meningitis, which stimulate the respiratory center, and salicylate poisoning, leading to hyperventilation.</p> Signup and view all the answers

How does hyperpyrexia influence respiratory rate and relate to metabolic alkalosis?

<p>Hyperpyrexia increases body temperature, resulting in an elevated respiratory rate which can lead to hyperventilation and contribute to the development of metabolic alkalosis.</p> Signup and view all the answers

What is primarily lost from the stomach in cases of excessive HCl loss, leading to alkalosis?

<p>Chloride ions (Cl–) are primarily lost.</p> Signup and view all the answers

What effect does excessive alkali administration have on the body's bicarbonate levels?

<p>It increases bicarbonate (HCO3–) levels due to conversion of administered bases.</p> Signup and view all the answers

How does hyperventilation contribute to respiratory alkalosis?

<p>Hyperventilation causes excessive loss of CO2, leading to decreased levels of carbonic acid (H2CO3).</p> Signup and view all the answers

In respiratory alkalosis, what compensatory mechanism is primarily utilized by the body?

<p>The renal system compensates by excreting bicarbonate (HCO3–).</p> Signup and view all the answers

What is the typical pH ratio associated with a normal bicarbonate to carbonic acid balance?

<p>The typical pH ratio is 20:1 for [HCO3–]/[H2CO3].</p> Signup and view all the answers

What ion retention occurs in the blood as a compensatory response during respiratory alkalosis?

<p>Chloride ions (Cl–) are retained in the blood.</p> Signup and view all the answers

What is one consequence of decreased excretion of NH3 in the urine during respiratory alkalosis?

<p>It contributes to the retention of bicarbonate and alkalosis.</p> Signup and view all the answers

What condition is also referred to as a primary H2CO3 deficit?

<p>Respiratory alkalosis is referred to as a primary H2CO3 deficit.</p> Signup and view all the answers

What biochemical changes characterize an uncompensated state in plasma or blood?

<p>Uncompensated states show a disproportionate decrease in [HCO3–] and [H2CO3], leading to decreased pH and total CO2 content.</p> Signup and view all the answers

Describe the characteristics of a fully compensated acid-base state.

<p>In fully compensated states, [HCO3–] and [H2CO3] decrease proportionately, keeping the [HCO3–]:[H2CO3] ratio and pH within normal limits.</p> Signup and view all the answers

What is the urine pH and acidity when there is an abnormal loss of HCO3–?

<p>The urine pH is acidic, with increased excretion of NH4Cl and NaH2PO4.</p> Signup and view all the answers

List two conditions that can lead to respiratory acidosis due to impaired CO2 elimination.

<p>Emphysema and depression of the respiratory center are two conditions that can impair CO2 elimination.</p> Signup and view all the answers

What compensatory mechanism occurs in response to respiratory acidosis?

<p>The renal mechanism becomes more important, while the respiratory mechanism increases respiratory rate and depth to excrete more CO2.</p> Signup and view all the answers

What leads to an abnormal increase in anions other than HCO3- in acid gain?

<p>Diabetic acidosis, starvation, high fever, and lactic acidosis can lead to an abnormal increase in anions.</p> Signup and view all the answers

How does the [HCO3–]/[H2CO3] ratio change in respiratory acidosis?

<p>The [HCO3–]/[H2CO3] ratio decreases in respiratory acidosis due to increased levels of H2CO3.</p> Signup and view all the answers

What factors may contribute to a decrease in carbon dioxide elimination?

<p>Breathing air with high CO2 percentage and pulmonary conditions that impede CO2 elimination contribute to decreased carbon dioxide excretion.</p> Signup and view all the answers

Flashcards

Metabolic Acidosis

A condition where the blood pH is lower than normal due to an accumulation of acid or a loss of bicarbonate.

Primary Compensatory Mechanism (Metabolic Acidosis)

The body's first line of defense against metabolic acidosis. It involves increased breathing rate and depth to expel CO2, which ultimately reduces carbonic acid levels.

Uncompensated Acidosis

Occurs when the body's ability to compensate for metabolic acidosis fails, leading to a persistent increase in H+ ion concentration.

Secondary Compensatory Mechanism (Metabolic Acidosis)

The process by which the kidneys attempt to correct metabolic acidosis. This includes retaining cations, increasing ammonia production, and enhancing bicarbonate reabsorption.

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Respiratory Acidosis

A condition resulting from a build-up of carbon dioxide, leading to a decrease in blood pH.

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Metabolic Alkalosis

A condition where the blood pH is higher than normal due to an excess of bicarbonate or loss of acid.

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Respiratory Alkalosis

Caused by a decrease in blood CO2 levels due to excessive ventilation.

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Compensated Phase (Acid-Base Imbalance)

A state where the body's attempt to compensate for acid-base imbalance is successful, bringing the blood pH closer to normal.

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Renal mechanism in metabolic alkalosis

The kidneys play a crucial role in compensating for metabolic alkalosis by reabsorbing more bicarbonate ions (HCO3-) from tubules in response to a high pCO2 in the blood.

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Respiratory compensation in metabolic alkalosis

The respiratory center (RC) is inhibited by alkalosis, leading to shallow and irregular breathing. This reduced ventilation causes CO2 retention and increases the level of carbonic acid (H2CO3) in the blood.

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Renal mechanism in respiratory acidosis

The kidneys play a crucial role in compensating for respiratory acidosis by reabsorbing bicarbonate ions (HCO3-) from the tubules in response to a high pCO2 in the blood.

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Respiratory compensation in respiratory acidosis

The lungs play a crucial role in compensating for respiratory acidosis by increasing the rate and depth of breathing (hyperventilation) to expel more CO2 from the body.

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Compensated acid-base disorder

A condition where the body's pH is maintained within a normal range even though there is a disturbance in the acid-base balance.

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Uncompensated acid-base disorder

A condition where the body's pH is not within a normal range, indicating that the body is not adequately compensating for the acid-base imbalance.

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Compensatory Mechanisms in Metabolic Alkalosis

The body's attempts to correct metabolic alkalosis. It aims to reduce bicarbonate levels and increase acid excretion.

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Opposing Forces in Respiratory Compensation

Decreased ventilation raises pCO2, which tends to stimulate the respiratory center. However, alkalosis is a balancing force.

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Renal Mechanism in Alkalosis

The kidneys excrete more bicarbonate, replacing chloride in urine. This is due to decreased hydrogen-sodium exchange.

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Biochemical Characteristics of Uncompensated Alkalosis

The ratio of bicarbonate to carbonic acid is significantly increased, pushing the blood pH higher.

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Biochemical Characteristics of Compensated Alkalosis

The body successfully compensates for metabolic alkalosis. The bicarbonate to carbonic acid ratio and pH return to normal levels.

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Urinary Findings in Alkalosis

The urinary ammonia and titratable acidity decrease.

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Hypokalaemia in Alkalosis

Increased potassium excretion from the distal tubules can lead to potassium depletion in the blood.

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Metabolic Acidosis (Uncompensated)

A decrease in bicarbonate concentration ([HCO3-]) in the blood, leading to a lower pH.

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Metabolic Acidosis (Uncompensated - Compensation)

The body attempts to compensate for the decrease in bicarbonate ([HCO3-]) by also decreasing carbonic acid ([H2CO3]) and carbon dioxide (pCO2).

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Metabolic Acidosis (Uncompensated - Total CO2 and Ratio)

The total amount of CO2 in the blood ([HCO3-]+[H2CO3]), as well as the [HCO3-] : [H2CO3] ratio, decreases.

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Metabolic Acidosis (Urinary Changes)

The urine becomes more acidic to help excrete excess hydrogen ions (H+).

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Respiratory Acidosis (Compensation - Respiratory Mechanism)

Increased CO2 tension (pCO2) stimulates the respiratory center, leading to deeper and faster breathing to eliminate more CO2.

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Respiratory Acidosis (Compensation - Renal Mechanism)

When the body compensates for respiratory acidosis, the kidneys become the primary mechanism for restoring balance.

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Metabolic Acidosis (Causes)

Metabolic acidosis occurs when the body produces too much acid or loses too much base. This can be caused by conditions such as diabetes, starvation, lactic acidosis, and diarrhea.

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Metabolic Alkalosis (Uncompensated)

A type of acid-base imbalance where the blood pH is higher than normal due to a decrease in bicarbonate levels and an increase in the bicarbonate to carbonic acid ratio.

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Metabolic Alkalosis (Fully Compensated)

A type of acid-base imbalance where the body compensates for the metabolic alkalosis by retaining CO2, causing a slight increase in carbonic acid and a decrease in the bicarbonate to carbonic acid ratio.

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Primary Compensatory Mechanism (Metabolic Alkalosis)

Increased respiratory rate and depth are used to expel CO2, leading to a decrease in carbonic acid levels.

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Secondary Compensatory Mechanism (Metabolic Alkalosis)

The kidneys attempt to correct metabolic alkalosis by increasing bicarbonate excretion and enhancing hydrogen ion reabsorption.

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Respiratory Alkalosis (Causes)

A condition where the Respiratory Centre (RC) is stimulated, leading to hyperventilation and a tendency towards alkalosis.

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Causes of Metabolic Alkalosis: Excessive HCl Loss

This occurs when excessive amounts of hydrochloric acid (HCl) are lost from the stomach, often due to conditions like pyloric obstruction or high intestinal blockage. The loss of HCl indirectly leads to the accumulation of base in the blood.

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Causes of Metabolic Alkalosis: Alkali Administration

Taking in too much alkali, like baking soda (sodium bicarbonate) or certain salts, can cause metabolic alkalosis. The body may then convert these substances into bicarbonate, further increasing its alkaline levels.

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Causes of Metabolic Alkalosis: Potassium Deficiency

Potassium deficiency can lead to metabolic alkalosis. Potassium plays a role in regulating acid-base balance, and its lack disrupts this process.

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Mechanism of Respiratory Alkalosis: Hyperventilation

Hyperventilation, a condition where the body breathes rapidly and deeply, leads to the increased loss of CO2 from the blood. This decrease in CO2 results in a lower concentration of carbonic acid (H2CO3), pushing up the pH.

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Compensatory Mechanisms for Respiratory Alkalosis: Renal

The kidneys try to compensate for respiratory alkalosis by excreting more bicarbonate (HCO3-) in urine, reducing its levels in the blood. They also retain chloride (Cl-) to further help balance the pH.

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Features of Respiratory Alkalosis: Similar to Metabolic Alkalosis

Other symptoms and features of metabolic alkalosis may be observed in respiratory alkalosis, as both conditions involve a shift in the blood's pH towards the alkaline range.

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Study Notes

Medical Biochemistry: Acid-Base Imbalance

  • Acid-base imbalance can manifest as acidosis or alkalosis. Acidosis can be metabolic or respiratory, while alkalosis can also be metabolic or respiratory. Compensated or uncompensated phases exist for all types.

Metabolic Acidosis

  • Also known as primary alkali deficit, this is the most common acid-base disturbance clinically.
  • It's caused by a decrease in plasma bicarbonate (HCO3-) with little or no change to the H2CO3 fraction.
  • The ratio [HCO3-]/[H2CO3] = 20/1
  • A lower ratio means decreased pH, leading to metabolic acidosis.

Primary Compensatory Mechanism (Metabolic Acidosis)

  • The respiratory center increases breathing rate (Kussmaul respiration) to eliminate excess CO2 and reduce H2CO3.
  • This restores the [HCO3-]/[H2CO3] ratio towards 20:1, but eventually, reduced pCO2 depresses the respiratory centers.
  • Compensatory mechanisms are only partially effective.
  • In early stages of the deficit, the body is in a state of compensated acidosis. But worsening conditions and untreated conditions can lead to uncompensated acidosis.

Secondary Compensatory Mechanism (Metabolic Acidosis)

  • The kidneys increase the formation and excretion of ammonia (NH3) to secrete excess H+ions.
  • This helps conserve bicarbonate (HCO3-).
  • More H+ is excreted and more K+ is excreted, compared to H+, in the distal tubule.

Biochemical Characteristics (Metabolic Acidosis) - Uncompensated

  • Significant decrease in [HCO3-].
  • Decreased [H2CO3] and pCO2.
  • Decrease in total CO2 content ([HCO3-] + [H2CO3]).
  • Decrease in the [HCO3-]/[H2CO3] ratio.
  • Decreased pH.

Biochemical Characteristics (Metabolic Acidosis) - Fully Compensated

  • Low CO2 content .
  • Proportional decrease in [HCO3- ] and [H2CO3] .
  • [HCO3-]/[H2CO3] and pH are within normal limits

Urinary Findings (Metabolic Acidosis)

  • Acidic urine (pH).
  • Increased excretion of NH4Cl and NaH2PO4.
  • Increased titratable acidity.

Causes (Metabolic Acidosis)

  • Excessive gain of acids (e.g., diabetic acidosis, starvation, high fever, violent exercise).
  • Increased production of acid ions (e.g., lactic acidosis).
  • Ingestion of acidic salts.
  • Renal insufficiency.
  • Impaired acid excretion.
  • Severe diarrhea (loss of bicarbonate).

Respiratory Acidosis

  • Characterized by “primary [H2CO3] carbonic acid excess.”
  • Results from an increase in carbon dioxide (CO2) in the blood (pCO2↑) due to impaired CO2 elimination.
  • Can be caused by breathing air with high CO2, or impaired lung function (e.g., emphysema) or depressed respiratory centers.

Mechanism (Respiratory Acidosis)

  • Impaired CO2 excretion leads to its accumulation, increasing [H2CO3].
  • This lowers [HCO3-] / [H2CO3] ratio, which leads to decreased pH.
  • Respiratory compensation becomes secondary, with renal compensation taking on more importance.

Biochemical Characteristics (Respiratory Acidosis) - Uncompensated

  • Significantly increased [H2CO3] (and pCO2).
  • Increased [HCO3-].
  • Increased total CO2 content.
  • Decreased [HCO3-]: [H2CO3] ratio.
  • Decreased pH

Biochemical Characteristics (Respiratory Acidosis) - Fully Compensated

  • High CO2 content,
  • Proportionate increases in [H2CO3] & [HCO3-],
  • Ratio [HCO3-] : [H2CO3] & pH are within normal limits.

Urinary Findings (Respiratory Acidosis)

  • Increased urinary NH3.
  • Increased titratable acidity.

Metabolic Alkalosis

  • Characterized by “primary alkali excess” resulting in an increase in plasma bicarbonate (HCO3−).
  • Most commonly caused by an absolute or relative increase in the "alkali reserve".

Mechanisms (Metabolic Alkalosis)

  • Excess HCO3− accumulation (e.g., soluble alkali ingestion).
  • This causes increased [HCO3−]/[H2CO3], and consequently an increased pH.

Biochemical Characteristics (Metabolic Alkalosis) - Uncompensated

  • Increased [HCO3-].
  • Increased [H2CO3] (and pCO2).
  • Increased total CO2 content.
  • Increased [HCO3-]: [H2CO3] ratio
  • Increased pH

Biochemical Characteristics (Metabolic Alkalosis) - Fully Compensated

  • High CO2 content.
  • Proportionate increase in [H2CO3] and [HCO3-].
  • The [HCO3-] : [H2CO3] ratio and pH are within normal normal levels..

Urinary Findings (Metabolic Alkalosis)

  • Decreased urinary acidity.
  • Decreased NH3 formation.
  • Decreased titratable acidity.

Causes (Metabolic Alkalosis)

  • Excessive loss of hydrochloric acid (HCl) from the stomach (e.g., pyloric obstruction).
  • Excessive intake of alkali (e.g., NaHCO3, Na and K acetates, lactates or citrates).
  • Potassium deficiency.

Respiratory Alkalosis

  • Characterized by a “primary H2CO3 deficit”, caused by a decrease in [H2CO3], typically from hyperventilation.

Mechanisms (Respiratory Alkalosis)

  • Excessive loss of CO2 (e.g., hyperventilation).
  • Causes a decrease in [H2CO3], and consequently an increase in [HCO3-] : [H2CO3] ratio, which leads to an increased pH.
  • Increased CO2 loss initially depresses respiratory function.

Biochemical Characteristics (Respiratory Alkalosis) - Uncompensated

  • Decreased [H2CO3] (and pCO2).
  • Decreased [HCO3-].
  • Decreased total CO2 content.
  • Increased [HCO3-] : [H2CO3] ratio.
  • Increased pH

Biochemical Characteristics (Respiratory Alkalosis) - Fully Compensated

  • Low CO2 content.
  • Proportionate decrease in [H2CO3] and [HCO3-].
  • [HCO3- : H2CO3] ratio and pH are within normal limits.

Urinary Findings (Respiratory Alkalosis)

  • Decreased NH3 and titratable acidity in the urine.

Causes (Respiratory Alkalosis)

  • Increased respiratory center stimulation (CNS diseases, salicylate poisoning).
  • Hyperventilation due to high body temperature (hyperpyrexia).
  • Lung diseases.

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Description

This quiz explores the biochemical and physiological aspects of metabolic alkalosis, including its definitions, causes, and compensatory mechanisms. It also examines the kidneys' roles in acid-base balance during changes in pCO2 and other disturbances. Test your understanding of this critical metabolic disorder.

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