Section 4

Question 1

T or F: Any change in [H+] is directly related to the ratio of [HCO3-] to [CO2]

Answer 1

True

Question 2

What information does determining the concentration of HCO3- and CO2 provide regarding acid-base imbalances?

Answer 2

Determining the concentration of HCO3- and CO2 provides more information on the source of the acid-base imbalance than simply calculating the concentration of H+ within the solution.

Question 3

What are the two rules of thumb that apply when examining acid-base imbalances before compensation takes place?

Answer 3

Change in pH: Changes in pH caused by the respiratory system result in abnormal [CO2], while changes in pH caused from metabolism result in abnormal [HCO3-].

Change in [HCO3-]:[CO2] ratio: Acidosis occurs when the [HCO3-]:[CO2] ratio falls below 20:1, while alkalosis occurs when the ratio rises above 20:1.

Question 4

What characterizes respiratory acidosis?

Answer 4

Respiratory acidosis occurs when there is a buildup of CO2 in the plasma, leading to a [HCO3-]:[CO2] ratio below 20:1. It is typically caused by hypoventilation, resulting in inadequate removal of CO2 through the lungs.

Respiratory acidosis can be caused by conditions such as emphysema, chronic bronchitis, asthma, severe pneumonia, and even metabolic acidosis.

Question 5

Describe uncompensated respiratory acidosis.

Answer 5

In uncompensated respiratory acidosis, there is an increase in [CO2], leading to the formation of H+ and HCO3-. H+ will lead to acidosis yet there is little change in the [HCO3-]

(While H+ increases, there is little change in [HCO3-] due to its significantly higher concentration compared to [H+])

Question 6

How does the body compensate for respiratory acidosis?

Answer 6

To compensate for respiratory acidosis, chemical buffers immediately absorb extra H+, and the kidneys secrete more H+ while reabsorbing HCO3- and generating new HCO3-. These compensatory mechanisms continue until [HCO3-] elevates enough to restore the ratio to 20:1 and bring the pH back to 7.4.

The respiratory system CANNOT play a role in compensation because it is a respiratory issue that caused it in the first place.

Question 7

Can the respiratory system play a role in compensation for respiratory acidosis?

Answer 7

No, it cannot, because it is a respiratory issue that caused it in the first place.

Question 8

What characterizes respiratory alkalosis?

Answer 8

Respiratory alkalosis occurs when there is an increase in ventilation, leading to a decrease in [CO2] in the plasma below normal levels. It can be caused by conditions such as fever, anxiety, and severe infections.

Question 9

Describe uncompensated respiratory alkalosis.

Answer 9

In uncompensated respiratory alkalosis, the decrease in [CO2] increases the [HCO3-]:[CO2] ratio, resulting in an increased pH. However, there is little change in [HCO3-].

Question 10

How does the body compensate for respiratory alkalosis?

Answer 10

To compensate for respiratory alkalosis, the chemical buffer systems release H+, and the respiratory system responds by decreasing ventilation. ([CO2] and [H+] are the driving forces behind increased ventilation so when both decrease the respiratory center usually responds by decreasing ventilation)

If respiratory alkalosis persists, the kidneys eventually compensate by decreasing H+ secretion and increasing HCO3- secretion until the [HCO3-]:[CO2] ratio is restored to 20:1.

Question 11

It can be caused by hyperventilation:

a) respiratory acidosis
b) respiratory alkalosis

Answer 11

alkalosis

Question 12

It is caused by an increase in the concentration of CO2 in the blood:

a) respiratory acidosis
b) respiratory alkalosis

Answer 12

acidosis

Question 13

It increases the pH of the blood:

a) respiratory acidosis
b) respiratory alkalosis

Answer 13

alkalosis

Question 14

It is seen when the [HCO3-]:[CO2] ratio is below 20:1

a) respiratory acidosis
b) respiratory alkalosis

Answer 14

acidosis

Question 15

It can occur with conditions such as emphysema, chronic bronchitis, asthma, severe pneumonia:

a) respiratory acidosis
b) respiratory alkalosis

Answer 15

acidosis

Question 16

What is metabolic acidosis also known as, and what does it describe?

Answer 16

Metabolic acidosis, also known as non-respiratory acidosis, describes any condition causing acidosis besides that due to excess CO2. It is characterized by a decrease in [HCO3-] and a normal [CO2].

Question 17

What causes the decrease in [HCO3-] in metabolic acidosis?

Answer 17

The decrease in [HCO3-] in metabolic acidosis can be caused by excessive loss of HCO3- or from the buildup of non-carbonic acids, which also decreases [HCO3-] due to buffering.

Question 18

How is the anion gap used to determine the cause of metabolic acidosis?

Answer 18

The anion gap is used to determine the cause of metabolic acidosis. It’s calculated by:
anion gap = [Na+] + [K+] - ([Cl-] [HCO3-])

The resulting gap estimates the amount of non-measured anions, which may include phosphate, citrate, sulfate, proteins, lactate, and keto acids.]

(normally plasma is electro-neutral meaning the number of cations = anions, so we can find non-measured anions through this equation)

Question 19

What does a low anion gap indicate, and what can cause it?

Answer 19

A low anion gap (< 8 mEq/L) is uncommon and usually results from the loss of plasma albumin, such as during hemorrhage.

Question 20

What does a normal anion gap indicate, and what conditions can cause it?

Answer 20

A normal anion gap (8-16 mEq/L) suggests a loss of HCO3-, which can be caused by conditions like diarrhea and some renal diseases. Typically, there is a compensatory increase in [Cl-] to conserve electrical neutrality.

Question 21

What does a high anion gap indicate, and what does it suggest about the metabolic acidosis?

Answer 21

A high anion gap (> 16 mEq/L) indicates that the metabolic acidosis is caused by an increase in unmeasured anions, leading to a decrease in [HCO3-] as it is used up for buffering the acids.

Question 22

What are the four common causes of metabolic acidosis?

Answer 22

Metabolic acidosis, the most frequently encountered type of acid-base imbalance, commonly occurs due to severe diarrhea, diabetes mellitus, strenuous exercise, and uraemic acidosis.

Question 23

How does severe diarrhea contribute to metabolic acidosis?

Answer 23

The digestive juices are rich in HCO3- that is secreted to aid in digestion but later reabsorbed. During diarrhea, this HCO3- may be eliminated before it can be reabsorbed, which causes a drop in [HCO3-], decreasing the buffer capacity of the plasma as well as causing more bicarbonate to dissociate and release H+

Question 24

How does diabetes mellitus contribute to metabolic acidosis?

Answer 24

Without insulin, glucose does not enter most cells, so they revert to fat metabolism to generate ATP.

This causes an increase in keto acids, which raises the anion gap.

Question 25

How does strenuous exercise contribute to metabolic acidosis?

Answer 25

When muscles resort to anaerobic metabolism, excess lactate is produced which raises plasma H+.

The lactic acid will also raise the anion gap

Question 26

How does uraemic acidosis contribute to metabolic acidosis?

Answer 26

Uraemia is severe renal failure. With decreased renal function, the kidneys cannot excrete the excess H+ produced from metabolism so the [H+] increases.

There is generally a loss of HCO3- as well, causing an increased anion gap.

Question 27

What characterizes metabolic acidosis?

Answer 27

Metabolic acidosis is characterized by a decrease in [HCO3-] and a normal [CO2]. This decrease can result from excessive loss of HCO3- or the buildup of non-carbonic acids, which also decreases [HCO3-] due to buffering

Question 28

How does the body compensate for metabolic acidosis?

Answer 28

In metabolic acidosis (except uraemic acidosis) compensation occurs by the buffers taking up the extra H+, the lungs blowing off extra CO2, and the kidneys secreting more H+ while conserving HCO3-.

This compensatory mechanism helps restore acid-base balance.

Question 29

How effective is the respiratory system in compensating for metabolic acidosis, and what is the consequence for some people?

Answer 29

The respiratory system can only partially compensate for metabolic acidosis.

This limitation means that individuals with uraemic acidosis, characterized by decreased kidney function, cannot fully compensate for metabolic acidosis through respiratory mechanisms.

Question 30

What characterizes metabolic alkalosis?

Answer 30

Metabolic alkalosis is characterized by a reduced [H+] caused by a decrease in non-carbonic acids.

In its uncompensated state, it is associated with an increase in [HCO3-] and no change in [CO2], leading to a [HCO3-]:[CO2] ratio above 20:1.

Question 31

What are the primary causes of metabolic alkalosis?

Answer 31

The primary causes of metabolic alkalosis include:

• Hydrochloric acid is secreted into the stomach during digestion. The HCl secretion results in HCO3- being transported into the plasma. This increased plasma [HCO3-] is generally not a problem as most of the secreted H+ will be reabsorbed in the digestive tract and therefore reduce free HCO3-. With vomiting, there is a loss of stomach H+, meaning it cannot be reabsorbed so plasma pH increases and [HCO3-] remains elevated
• ingestion of alkaline drugs, which contain high amounts of HCO3-. The excess gets absorbed in the digestive tract, raising [HCO3-] and reducing plasma H+ by binding it.

Question 32

How does the body compensate for metabolic alkalosis?

Answer 32

To compensate for metabolic alkalosis, the body employs several mechanisms. Initially, chemical buffer systems release H+, ventilation decreases to raise plasma CO2 levels, and if the condition persists, the kidneys reduce H+ secretion and increase HCO3- secretion.

When fully compensated, both [HCO3-] and [CO2] levels are elevated above normal, but the [HCO3-]:[CO2] ratio returns to 20:1.

Question 33

What happens in uncompensated metabolic alkalosis?

Answer 33

In uncompensated metabolic alkalosis, the [HCO3-]:[CO2] ratio is increased due to excess [HCO3-], leading to alkalosis without compensation by other mechanisms.

Question 34

The acid-base status categories for normal are given. Name the same categories for compensated respiratory acidosis.

Normal:
pH = normal
[CO2] = normal
[HCO3-] = normal
[HCO3-]:[CO2] = 20/1

Answer 34

Compensatory respiratory acidosis:
pH = normal
[CO2] = INCREASED
[HCO3-] = INCREASED
[HCO3-]:[CO2] = 40/2 (20/1)

Question 35

The acid-base status categories for normal are given. Name the same categories for UNcompensated respiratory alkalosis.

Normal:
pH = normal
[CO2] = normal
[HCO3-] = normal
[HCO3-]:[CO2] = 20/1

Answer 35

pH = INCREASED
[CO2] = DECREASED
[HCO3-] = normal
[HCO3-]:[CO2] = 20/0.5 (40/1)

Question 36

The acid-base status categories for normal are given. Name the same categories for UNcompensated metabolic acidosis.

Normal:
pH = normal
[CO2] = normal
[HCO3-] = normal
[HCO3-]:[CO2] = 20/1

Answer 36

Uncompensated metabolic acidosis:
pH = DECREASED
[CO2] = normal
[HCO3-] = DECREASED
[HCO3-]:[CO2] = 10/1