WEEK 1: Acid – Base Balance

Question 1

State the importance of acid-base balance.

Answer 1

1. Necessary to sustain life
2. The pH determines
   *Properties of proteins: enzyme activity
   part of the cell structure
   *Permeability of membranes: distribution of electrolytes

Question 2

State the Consequences of fluctuations in pH.

Answer 2

*Changes in excitability of nerve and muscle cells
*Marked influence on enzyme activity
*Changes influence K+ levels in body

Question 3

What is the normal pH kept at?

State the pH levels not compatible to life.

Answer 3

pH is kept between 7.35 and 7.45.
pH levels <7.0 or> 7.8 are not compatible with life.

Question 4

The free hydrogen ion (H+) concentration in body fluids is regulated exquisitely around _____________.

H+flux through the body greatly exceeds this magnitude.

In a 70-kg human being at a basal state, normal metabolic and dietary acid production rate is about 50 to 70 mmoles/d and respiratory volatile acid production at the basal state is around 15,000 mmoles/d, with peak production at maximal exercise reaching 200 mmoles/min.

The flux of H+through the organism over 24 hours is __orders of magnitude greater than the total pool of free H+in total body water (<2μmoles).

Answer 4

The free hydrogen ion (H+) concentration in body fluids is regulated exquisitely around 40 nmol/L (pH 7.40)
H+flux through the body greatly exceeds this magnitude.
In a 70-kg human being at a basal state, normal metabolic and dietary acid production rate is about 50 to 70 mmoles/d and respiratory volatile acid production at the basal state is around 15,000 mmoles/d, with peak production at maximal exercise reaching 200 mmoles/min.
The flux of H+through the organism over 24 hours is 8 orders of magnitude greater than the total pool of free H+in total body water (<2μmoles).

Question 5

What is an electrolyte?

Answer 5

An electrolyte is a substance which develops an electrical charge in the presence of water.

-Cation
-Anion

Question 6

What is an acid?

Answer 6

Electrolyte that forms a hydrogen cation and any anion in the presence of water.

Question 7

Sources of H+ in the body.

Answer 7

*Carbonic acid formation

*Inorganic acids produced during breakdown of nutrients (e.g., HCl, nitric acid)

*Organic acids resulting from intermediary metabolism (e.g., lactic acid, acetic acid)

Question 8

Define a strong and weak acid with examples.

Answer 8

1. Weak acid
   partially ionizes in water.
   H2CO3, lactic acid, citric acid, ketones, aminoacids, fatty acids, uric acid
2. Strong acid
   Totally ionizes in water.
   HCl, sufuric, nitric, phosphoric,

Question 9

What is a base?

Answer 9

A substance that can accept hydrogen ions.

Question 10

Define weak and strong base with examples.

Answer 10

1. Weak base
   do not bind well with hydrogen.
   HCO3-
2. Strong base
   binds well with hydrogen.
   OH-

Question 11

What is pH?

Answer 11

Designation used to express the concentration of H+

Question 12

On a typical Western diet, approximately 15,000 mmol of carbon dioxide and 50 to 100 mEq of nonvolatile acid (mostly sulfuric acid derived from the metabolism of sulfur-containing amino acids) are produced each day.

State two important sulfur-containing amino acids found in proteins.

Answer 12

Two important sulfur-containing amino acids found in proteins are methionine and cysteine.

Question 13

State the different mechanisms in the body that maintain acid-base balance.

What exerts a pivotal role in the excretion of nonvolatile acid and base loads?

Answer 13

Acid-base balance is accomplished by concerted efforts of
1. extracellular and intracellular buffers,
2. highly efficient ventilatory responses,
3. metabolic functions of the liver, and
4. renal ammoniagenic and solute transport mechanisms.

For excretion of nonvolatile acid and base loads, the kidney assumes the pivotal role.

Question 14

State the range of pH.
State the neutral pH.
State the physiologic pH.

Answer 14

Ranges from 0 - 14
Neutral pH (7) (physiological 7.4)

Physiological pH (7.4)

Question 15

Define acidosis and alkalosis.

Answer 15

Acidosis refers to a pH less than 7.35.
Alkalosis refers to a pH greater than 7.45.

Question 16

Which blood is used to determine acid-base status?

Answer 16

NB! Arterial blood is used to determine acid-base status. Normal arterial pH=7.4

Question 17

What are volatile acids?

Answer 17

Can be eliminated as CO2 gas.

Question 18

State the only physiological volatile acid.

What are the others?

Answer 18

Carbonic acid is the only physiological.

Others (Acetic acid formic acid, succinic acid, butyric acid and propionic acid)

Question 19

State the 2 elements that carbonic acid dissociates into.

Which part of the body are volatile acids eliminated?

Answer 19

Carbonic acid dissociates to CO2 and H20.

Volatile acids are eliminated through the lungs.

Question 20

What is a non-volatile acid?

Answer 20

An acid that cannot be eliminated as CO2 gas.

Question 21

State examples of non-volatile acids.

Answer 21

Example
*Lactic acid
*Ketoacids
-Acetoacetate
-3hydroxybutyrate
-acetone

Question 22

What is a buffer?

Answer 22

A buffer is an aqueous solution made of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.

Its pH changes very little when a small amount of strong acid or base is added.

It is used to prevent any change in the pH of a solution.

Question 23

State the 3 functions of buffers.

Answer 23

*Control pH
*Converts a strong acid into a weak one
*Converts a strong base into a weak one

Question 24

What is the Henderson-Hasselbalch equation?

Answer 24

The Henderson-Hasselbalch equation is a mathematical expression that describes the relationship between the pH of a solution, the pKa (acid dissociation constant) of a weak acid, and the concentrations of the weak acid and its conjugate base. The equation is as follows:

pH=pKa+log([A-] / [HA])

pH is the negative logarithm (base 10) of the hydrogen ion concentration in a solution.

pKa is the negative logarithm (base 10) of the acid dissociation constant (Ka) of the weak acid.

[A^-] is the concentration of the conjugate base of the weak acid.

[HA] is the concentration of the weak acid.

Question 25

State the most important buffer which operates both in the lung and the kidney.

Answer 25

Bicarbonate buffer

Question 26

State the components which make the bicarbonate buffer.

Answer 26

Consists of: *H2CO3 and HCO3- CO2 is excreted or retained as needed. HCO3 is excreted or retained as needed.

Question 27

Describe how the Protein Buffer System work.

Answer 27

Proteins carry a negative charge. They can combine with H+.

Question 28

Hemoglobin is an example of the protein buffering system. Describe how it works.

Answer 28

1. As tissues metabolize, they produce carbon dioxide (CO2) as a byproduct. Carbon dioxide can combine with water to form carbonic acid (H2CO3) through the action of an enzyme called carbonic anhydrase. 2.The carbonic acid (H2CO3) formed rapidly dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). 3. Hemoglobin plays a crucial role in buffering the increased hydrogen ions (H+) generated during this process. Hemoglobin can bind to hydrogen ions. The reaction with hemoglobin looks like this: HHb (deoxyhemoglobin) + H+⇌H2O + Hb (oxygenated hemoglobin) When hemoglobin binds to hydrogen ions, it prevents the accumulation of excessive protons in the blood, helping to resist changes in pH. 4. In the lungs, where oxygen levels are higher, hemoglobin releases the bound hydrogen ions, and the bicarbonate ion is converted back to carbon dioxide. The overall reaction in the lungs is the reverse of the initial reaction: HCO3- + H+ ⇌ H2CO3 → CO2 + H2O

Question 29

Describe how the Phosphate buffer system works.

Answer 29

It involves the presence of dihydrogen phosphate (H2PO4-) and hydrogen phosphate (HPO4^2-) ions, which act as weak acids and bases, respectively. Dibasic phosphate HPO4-2 filtered freely at glomerulus, 75% is reabsorbed. 2. HPO4-2 combines with H + to form monobasic phosphate H2PO4- 3. Bicarbonate is reabsorbed as needed

Question 30

Describe the role of the liver in acid-base balance.

Answer 30

Detoxification of ammonia (NH3) in the liver is done via two ways (ammonia is produced during deamination of amino acids. 1. Urea Synthesis: The liver plays a role in the synthesis of urea through the urea cycle. Urea is a nitrogenous waste product formed from the breakdown of proteins and amino acids. The removal of nitrogen in the form of urea helps eliminate excess acids from the body, contributing to acid-base balance. 2. Synthesis of Glutamine: The liver can also detoxify ammonia by incorporating it into the amino acid glutamine. Glutamine synthesis involves the combination of ammonia with glutamate in a reaction catalyzed by the enzyme glutamine synthetase. The resulting glutamine is a relatively non-toxic form of ammonia. Glutamine can be transported to other tissues, such as the kidneys, where it releases ammonia to be used in various metabolic processes or excreted.

Question 31

Describe how the Renal buffer system works.

Answer 31

Kidneys regulate pH via 3 ways. 1. Reabsorption of filtered HCO3- 2. Generating consumed HCO3-by secreting protons (renal acidification) 3.  formation of titrable acid of  H2PO4- / HPO4–2 4. Excretion of ammonia in Urine (as ammonium)

Question 32

Describe the kidney role in ABB.

Answer 32

*Third line of defense *Kidneys require hours to days to compensate for changes in body-fluid pH Control pH of body fluids by adjusting H+ excretion HCO3- excretion (during alkalosis) Ammonia (NH3) secretion (during acidosis)

Question 33

Describe the Cellular Shifts in Buffer System during acidosis and alkalosis.

Answer 33

Acidosis *Potassium leaves the cell *Hydrogen ion enters the cell Alkalosis *Hydrogen leaves the cell *Potassium enters the cell

Question 34

State the time taken by the following to regulate pH. 1. Buffering system 2. Respiratory system 3. Renal system

Answer 34

1. Buffering system within seconds 2. Respiratory system 20-30 minutes 3. Renal system several days

Question 35

Describe the respiratory control of pH.

Answer 35

1. Acidosis respiratory rate increases 2. Alkalosis respiratory rate decreases Response time 20-30 minutes

Question 36

Increased hydrogen ions Decreased bicarbonate ions. Decreased pH. Name the phenomena described above.

Answer 36

Acidosis.

Question 37

Decreased hydrogen ion concentration. Increased bicarbonate concentration Increased pH Name the phenomena described above.

Answer 37

Alkalosis

Question 38

State the normal values for the following. pH pCO2 HCO3- Base Excess pO2 Saturation O2

Answer 38

pH 7.4 (7.35 - 7.45) pCO2 40 (35-45) mmHg HCO3- 24 (22-26) mEq/L Base Excess 0 (-2 to +2 mEq/L) pO2 (75-100 mmHg) Saturation O2 98 %

Question 39

Define anion gap.

Answer 39

Difference between cations and anions.

Question 40

State the formula for calculating anion gap.

Answer 40

Anion Gap= (Sodium− (Chloride + Bicarbonate)) In this equation: *Sodium (Na) represents the concentration of sodium ions in the blood. *Chloride (Cl) represents the concentration of chloride ions in the blood. *Bicarbonate (HCO₃⁻) represents the concentration of bicarbonate ions in the blood.

Question 41

State the units for anion gap.

Answer 41

The anion gap is usually expressed in milliequivalents per liter (mEq/L) or millimoles per liter (mmol/L).

Question 42

What is the normal anion gap?

Answer 42

Normal Value 10 to 12 mEq/L

Question 43

Calculate the anion gap. Na = 145 mEq/L Cl = 104 mEq/L HCO3 = 26 mEq/L

Answer 43

Anion gap = 145 – (104 +26) => AG = 15 mEq/L

Question 44

Describe the anion gap when there is hypoalbuminemia.

Answer 44

Hypoalbuminemia will show low Anion Gap than normal!

Question 45

What Does Anion Gap Tell You?

Answer 45

Anion gap represents the remaining unmeasurable anions in the ECF. phosphates sulfates ketone pyruvate lactate

Question 46

What does an elevated anion gap represent?

Answer 46

Elevated anion gap represents metabolic acidosis. If the anion gap is significantly elevated, it may indicate the presence of unmeasured anions, which could be due to conditions like lactic acidosis, diabetic ketoacidosis, or renal failure.

Question 47

Define oxygen saturation. State the normal oxygen saturation. What is the oxygen saturation dependent on?

Answer 47

Oxygen saturation (SaO2) is a measure of the percentage of hemoglobin (Hb) molecules in the blood that are bound to oxygen. Oxygen Saturation (greater than 95%) Dependent on SAO2

Question 48

Which delivers more oxygen to the tissue? Sat 87% Hgb 15 gm/dl Sat 95% Hgb 10 gm/dl

Question 49

Interpretation of Arterial Blood Gases. State the pH for the following. normal acidosis alkalosis

Answer 49

Look at the pH. normal 7.35 - 7.45 acidosis <7.35 alkalosis >7.45

Question 50

Can arise from either respiratory dysfunction or metabolic disturbances. State the Deviations divided into four general categories.

Answer 50

Respiratory acidosis Respiratory alkalosis Metabolic acidosis Metabolic alkalosis

Question 51

How does respiratory disturbance result in Acid-Base Imbalances?

Answer 51

Respiratory disturbance= retention or removal of CO2

Question 52

Look at the respiratory component. normal pCO2? increased pCO2 -->? decreased pCO2 -->?

Answer 52

Look at the respiratory component. normal pCO2 (35 - 45 mm Hg) increased pCO2 --> respiratory acidosis decreased pCO2 --> respiratory alkalosis.

Question 53

Look at the metabolic component. normal HCO3-? Increased HCO3-? Decreased HCO3-?

Answer 53

Look at the metabolic component normal HCO3- (22 - 26 mm HG) Increased HCO3- metabolic alkalosis Decreased HCO3- metabolic acidosis

Question 54

What is respiratory acidosis?

Answer 54

Result of abnormal CO2 retention arising from hypoventilation, (therefore ↑PCO2 observed)

Question 55

Describe respiratory acidosis under the following: *Ventilation *CO2 *H2CO3 *H+

Answer 55

Hypoventilation increased CO2 increased H2CO3 increased H+

Question 56

State the following Laboratory Values for respiratory acidosis. *pH *pCO2 *HCO3-

Answer 56

Laboratory Values pH < 7.35 pCO2 > 45 mm Hg HCO3- unchanged

Question 57

State the 4 main causes of respiratory acidosis.

Answer 57

Etiologies *Obstructive Lung Diseases *Restrictive Lung Diseases *Hypoventilation *Depression of respiratory center by drugs or disease -narcotics -inappropriate ventilator settings

Question 58

State the 5 main signs and symptoms of respiratory acidosis.

Answer 58

Signs and symptoms *Cyanosis *Shallow breathing *Dyspnea: Dyspnea is a term used to describe the sensation of difficult or labored breathing, often referred to as shortness of breath or breathlessness. *Confusion *Cardiac dysrhythmias: refer to abnormal heart rhythms or irregularities in the heart's electrical activity.

Question 59

What is respiratory alkalosis?

Answer 59

Primarily due to excessive loss of CO2 from body as result of hyperventilation (therefore ↓PCO2 observed)

Question 60

State the 3 aspects of the mechanism of respiratory alkalosis.

Answer 60

Mechanism -Hyperventilation -Low carbonic acid level -Low CO2

Question 61

State the following Laboratory Values for respiratory alkalosis. *pH *pCO2 *HCO3-

Answer 61

Laboratory Values pH > 7.45 pCO2 < 35 mm Hg HCO3- unchanged

Question 62

State the 2 main causes of respiratory alkalosis.

Answer 62

*Hyperventilation -anxiety -panic attacks *Increased respiratory center activity -fever

Question 63

Which part of the tubule and specific cells is involved H+ retention & HCO3- excretion? (Respiratory alkalosis)

Answer 63

During respiratory alkalosis, the type B intercalated cells in the distal convoluted tubule and connecting tubule of the renal tubule play a key role in H+ retention and HCO3- excretion to help maintain acid-base balance in response to changes in respiratory conditions.

Question 64

State the 5 main signs and symptoms of respiratory alkalosis.

Answer 64

Signs and Symptoms -Light headedness -Paresthesia's -Twitching -Chvostek’s sign -Trousseau’s sign Lightheadedness: Hypocalcemia can affect the nervous system, leading to symptoms such as lightheadedness or dizziness. Paresthesia's: Hypocalcemia may cause tingling sensations or numbness, known as paresthesia's. This can occur around the mouth, in the hands, and in the feet. Twitching: Muscle twitching or spasms (fasciculations) can be a symptom of hypocalcemia. Calcium plays a crucial role in muscle contraction, and low levels may lead to increased neuromuscular excitability. Chvostek’s Sign: Chvostek's sign is a clinical sign of hypocalcemia. It is elicited by tapping the facial nerve in the region of the parotid gland, resulting in twitching of the facial muscles, particularly the muscles around the mouth. This response is due to increased neuromuscular excitability. Trousseau’s Sign: Trousseau's sign is another clinical sign of hypocalcemia. It is elicited by inflating a blood pressure cuff on the arm above systolic pressure for a few minutes. This can lead to carpal spasm, where the hand and fingers go into a characteristic position due to increased neuromuscular excitability.

Question 65

State the 2 aspects of Mechanism of metabolic acidosis.

Answer 65

Retention of nonvolatile acids Excessive loss of base

Question 66

What happens to the following during metabolic acidosis? Laboratory: HCO3-, pH,

Answer 66

Laboratory : HCO3-, pH: decreases

Question 67

Why does paCO2 decrease later in metabolic acidosis?

Answer 67

In metabolic acidosis, the primary disturbance is a decrease in bicarbonate ions (HCO3-) in the blood, leading to an acidic pH. To compensate for this acidotic state, the respiratory system responds by increasing the respiratory rate, a compensatory mechanism aimed at reducing the concentration of carbon dioxide (CO2) in the blood. The increase in respiratory rate results in hyperventilation, which, over time, leads to a decrease in the partial pressure of carbon dioxide (PaCO2).

Question 68

State the 3 main causes of metabolic acidosis with increased AG.

Answer 68

Metabolic acidosis with an increased anion gap (AG) occurs when there is an excess of acid in the body, leading to a decrease in blood pH. 1. Lactic acidosis hypoxia, reduced lactic acid degradation. 2. Ketoacidosis diabetes, starvation, alcoholism… 3. Renal acidosis Accumulation of sulphates - Intoxications

Question 69

State the 4 main causes of metabolic acidosis without increased anion gap.

Answer 69

1. Diarrhea and other losses from the GIT 2. Renal tubular acidosis; HCO3-resorption disorders in renal tubule 3. Dilution acidosis administration of large quantities infusion without buffer system? (constant pCO2, HCO3-is quickly diluted) 4. NH4Cl overdose: This type of metabolic acidosis is often termed "hyperchloremic metabolic acidosis" because of the elevated chloride levels. It is characterized by a decrease in bicarbonate concentration without a corresponding increase in the anion gap.

Question 70

State the 2 aspects of the mechanisms for metabolic alkalosis.

Answer 70

Increased levels of HCO3- Decreased levels of H+

Question 71

State the following laboratory values for metabolic acidosis. Laboratory Values pH HCO3-

Answer 71

Laboratory Values pH > 7.45 HCO3- > 26 mEq/L

Question 72

What happens to the following during metabolic alkalosis? Laboratory: HCO3-, BBs, BE, pH NB *Base Excess (BE): *Buffer Bases (BBs):

Answer 72

Laboratory: HCO3-, BBs, BE, pH Base Excess (BE): Base excess is a measure of the amount of excess or deficit of base (primarily bicarbonate) in the blood. It indicates the degree of metabolic acidosis or alkalosis. A negative base excess suggests metabolic acidosis, while a positive base excess suggests metabolic alkalosis. Buffer Bases (BBs): Buffer bases, also known as total buffer base, represent the total concentration of buffers in the blood that can accept or donate protons. It reflects the blood's ability to resist changes in pH. Changes in buffer bases are related to changes in bicarbonate levels and can provide additional information about acid-base status.

Question 73

Why does paCO2 increase later in metabolic alkalosis?

Answer 73

In metabolic alkalosis, the primary disturbance is an excess of bicarbonate (HCO3-) in the blood, leading to an elevated pH. The respiratory system compensates for this alkalosis by decreasing the respiratory drive, resulting in hypoventilation. However, this hypoventilation doesn't lead to an increase in arterial carbon dioxide (PaCO2); rather, it tends to normalize or decrease PaCO2. The reason for this is that, in metabolic alkalosis, the decrease in respiratory rate is a compensatory mechanism aimed at reducing the loss of carbon dioxide (CO2) through ventilation. By hypoventilating, the body retains more CO2, which helps counteract the alkaline shift in pH.

Question 74

State 5 causes of metabolic alkalosis.

Answer 74

*Ingestion of large amounts of sodium bicarbonate *Parenteral administration of NaHCO3 *Vomiting of gastric contents *Nasogastric suctioning *Potassium wasting diuretics -thiazide diuretics -loop diuretics

Question 75

Describe the Potassium Imbalancesin Acidosis at the kidneys.

Answer 75

Kidney In acidosis there is an excess of H+ In acidosis the kidneys preferentially eliminate H+ When a H+ is eliminated a K+ is retained. Increased K+ retention leads to hyperkalemia

Question 76

Describe the Potassium Imbalancesin Acidosis at the cellular.

Answer 76

Cellular In acidosis H+ is buffered in the cell As H+ moves into the cell, K+ moves out of the cell. Increased K+ in the ECF produces hyperkalemia.

Question 77

Describe the Potassium Imbalancesin Alkalosis at the kidneys.

Answer 77

Kidney Alkalosis is related to decreased H+ concentration or increased base. In alkalosis the kidneys preferentially retain H+. When H+ is retained, a K+ is excreted. Increased excretion of K+ leads to hypokalemia.

Question 78

Describe the Potassium Imbalancesin Alkalosis at the cellular.

Answer 78

Cellular H+ moves from the cell to the extracellular fluid. When H+ moves from the cell, it is replaced by a K+. The result is hypokalemia.

Question 79

Describe Calcium Imbalancesin Acidosis.

Answer 79

Causes increased release of Ca++ from plasma proteins. Hypercalcemia

Question 80

Describe Calcium Imbalancesin Alkalosis.

Answer 80

Causes increased binding of Ca++ to plasma proteins. Hypocalcemia

Question 81

Describe the Compensationfor Respiratory Acidosis.

Answer 81

1. Chemical buffers immediately take up additional H+ Which one (s)? 2. The kidneys are the major compensatory mechanism for respiratory acidosis. -The kidneys retain increased HCO3- -Serum HCO3- rises above 26 mEq/L -pH returns to normal

Question 82

Which chemical buffers compensate for respiratory acidosis?

Question 83

Describe the Compensationfor Respiratory Alkalosis.

Answer 83

*The kidneys are the major compensatory mechanism for respiratory alkalosis. *The kidneys excrete more bicarbonate. *The HCO3+ falls below 22 mEq/L *This balances the acid-base ratio.

Question 84

Describe the Compensationfor Metabolic Acidosis.

Answer 84

*The respiratory system is the major compensatory mechanism for metabolic acidosis. *Hyperventilation occurs *CO2 is blown off. *pH returns to normal

Question 85

Describe the Compensationfor Metabolic Alkalosis.

Answer 85

*The respiratory system is the major compensatory mechanism for metabolic alkalosis. *Hypoventilation *pH returns to normal.