Physiology of Acid-Base Balance

Physiology of Acid-Base Balance

Under the guidance of :

Dr. Sandeep Tandon

Professor and Head of Dept. of Pedodontics

Dr.

Ambika S. Rathore Dr. Rinku

Mathur Dr .Shantanu

Jain Dr. Tripti

Sharma Rai

Under the guidance of :

Dr. Sandeep Tandon

Professor and Head of Dept. of Pedodontics

Dr.

Ambika S. Rathore Dr. Rinku

Mathur Dr .Shantanu

Jain Dr. Tripti

Sharma Rai

2

CONTENT:CONTENT:♣ Introduction♣ Acid-Base Balance♣ ph Scale♣ Acidosis and Alkalosis♣ Compensatory Mechanisms♣ Disturbance in acid-base balance♣ Anion Gap♣ Factors affecting acid-base balance in

children♣ Infantile metabolic acidosis

♣ Introduction♣ Acid-Base Balance♣ ph Scale♣ Acidosis and Alkalosis♣ Compensatory Mechanisms♣ Disturbance in acid-base balance♣ Anion Gap♣ Factors affecting acid-base balance in

children♣ Infantile metabolic acidosis

3

IntroductionIntroduction♠Acid-base homeostasis is the

part of human homeostasis concerning the proper balance between acids and bases, in other words, the pH.

♠Chemical and physiologic processes responsible for the maintenance of the acidity of body fluids.

♠Acid-base homeostasis is the part of human homeostasis concerning the proper balance between acids and bases, in other words, the pH.

♠Chemical and physiologic processes responsible for the maintenance of the acidity of body fluids.

4

Acid Base HomeostasisAcid Base Homeostasis Chemical processes: extracellular intracellular buffers

The physiologic processes: the excretion of volatile acids by the lungs and fixed acids by the kidneys

Chemical processes: extracellular intracellular buffers

The physiologic processes: the excretion of volatile acids by the lungs and fixed acids by the kidneys

5

ACID-BASE BALANCEACID-BASE BALANCE

6

ACIDSACIDSAcids can be defined as a proton (H+) donor

Hydrogen containing substances which dissociate in solution to release H+

Acids can be defined as a proton (H+) donor

Hydrogen containing substances which dissociate in solution to release H+

H+OH-

H+

OH-

H+

OH-

H+

OH-

7

ACIDSACIDS• Physiologically important acids include:

–Carbonic acid (H2CO3)–Phosphoric acid (H3PO4)–Pyruvic acid (C3H4O3)–Lactic acid (C3H6O3)

• Physiologically important acids include:

–Carbonic acid (H2CO3)–Phosphoric acid (H3PO4)–Pyruvic acid (C3H4O3)–Lactic acid (C3H6O3)

Lactic acid

Pyruvic acid

Phosphoric acid

8

BASESBASES

9

BASESBASES Bases can be defined as:

♥ A proton (H+) acceptor♥ Molecules capable of accepting a

hydrogen ion (OH-)

Bases can be defined as:♥ A proton (H+) acceptor♥ Molecules capable of accepting a

hydrogen ion (OH-)

H+OH-

H+

OH-

H+

OH-

H+

OH-

10

BASESBASES• Physiologically important bases

include:

–Bicarbonate (HCO3- )

–Biphosphate (HPO4-2 )

• Physiologically important bases include:

–Bicarbonate (HCO3- )

–Biphosphate (HPO4-2 )

Biphosphate

11

pH SCALEpH SCALE

12

• pH refers to Potential Hydrogen• Expresses hydrogen ion concentration in

water solutions.• Water ionizes to a limited extent to form

equal amounts of H+ ions and OH- ions

H2O H+ + OH-

•H+ ion is an acid

•OH- ion is a base

• pH refers to Potential Hydrogen• Expresses hydrogen ion concentration in

water solutions.• Water ionizes to a limited extent to form

equal amounts of H+ ions and OH- ions

H2O H+ + OH-

•H+ ion is an acid

•OH- ion is a base

pH SCALEpH SCALE

13

• Pure water is Neutral♥ ( H+ = OH- )

• pH = 7• Acid

♥ ( H+ > OH- ) • pH < 7

• Base ♥ ( H+ < OH- )

• pH > 7• Normal blood pH is 7.35 - 7.45• pH range compatible with life is 6.8 - 8.0

• Pure water is Neutral♥ ( H+ = OH- )

• pH = 7• Acid

♥ ( H+ > OH- ) • pH < 7

• Base ♥ ( H+ < OH- )

• pH > 7• Normal blood pH is 7.35 - 7.45• pH range compatible with life is 6.8 - 8.0

pH SCALEpH SCALE

OH-

OH-

OH-

OH-

OH-

OH-

H+

H+

H+

H+

OH-

OH-

OH-

OH-OH-

H+

H+

H+

H+OH-

OH-

OH-

H+

H+

H+

H+H+

H+

H+

ACIDS, BASES OR NEUTRAL???

1

2

3

14

pH SCALEpH SCALE• Normal hydrogen ion concentration in

ECF= 38-42 nM/L.• Ph scale- simplify the mathematical

handling of large numbers.

Unit changes in pH represent a tenfold change in H+ concentrations

• Normal hydrogen ion concentration in ECF= 38-42 nM/L.

• Ph scale- simplify the mathematical handling of large numbers.

Unit changes in pH represent a tenfold change in H+ concentrations

pH = log 1 / H+ concentration

15

pH SCALEpH SCALE

Ph of the ECF: 7.40 Ph of the ECF: 7.40

ACIDOSIS ALKALOSISNORMAL

DEATH DEATH

Venous Blood

Arterial Blood

7.3 7.57.46.8 8.0

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Determination of Acid Base Status

Determination of Acid Base Status

Henderson-Hasselbalch equation Normal acid-base ratio= 1:20

ph of arterial blood= indirect method

Henderson-Hasselbalch equation Normal acid-base ratio= 1:20

ph of arterial blood= indirect method

• pH = pK + log HCO3

CO2

• pH = pK + log HCO3

CO2

17

ACIDOSIS / ALKALOSISACIDOSIS / ALKALOSIS

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ACIDOSIS / ALKALOSISACIDOSIS / ALKALOSIS

• Acidosis♠ A condition in which the blood has too much

acid (or too little base), frequently resulting in a decrease in blood pH

• Alkalosis♠ A condition in which the blood has too much

base (or too little acid), occasionally resulting in an increase in blood pH

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♥ Alkalosis♥ Alkalosis

Acidosis / AlkalosisAcidosis / Alkalosis

H+ OH-

©Acidosis

H+ OH-

20

ACIDOSIS / ALKALOSISACIDOSIS / ALKALOSIS• pH changes have dramatic effects on

normal cell function1) Changes in excitability of nerve and

muscle cells2) Influences enzyme activity3) Influences K+ levels

• pH changes have dramatic effects on normal cell function1) Changes in excitability of nerve and

muscle cells2) Influences enzyme activity3) Influences K+ levels

21

Changes in Cell Excitability

Changes in Cell Excitability

pH decrease (more acidic) depresses the central nervous systemCan lead to loss of consciousness

pH increase (more basic) can cause over-excitabilityTingling sensations, nervousness, muscle

twitches

pH decrease (more acidic) depresses the central nervous systemCan lead to loss of consciousness

pH increase (more basic) can cause over-excitabilityTingling sensations, nervousness, muscle

twitches

22

Influences on Enzyme Activity

Influences on Enzyme Activity

pH increases or decreases can alter the shape of the enzyme rendering it non-functional.

Changes in enzyme structure can result in accelerated or depressed metabolic actions within the cell.

pH increases or decreases can alter the shape of the enzyme rendering it non-functional.

Changes in enzyme structure can result in accelerated or depressed metabolic actions within the cell.

23

Influences On K+ LevelsInfluences On K+ Levels

When reabsorbing Na+ from the filtrate of the renal tubules K+ or H+ is secreted (exchanged).

Normally K+ issecreted in muchgreater amountsthan H+

When reabsorbing Na+ from the filtrate of the renal tubules K+ or H+ is secreted (exchanged).

Normally K+ issecreted in muchgreater amountsthan H+

K+

K+K+K+K+K+K+

Na+Na+Na+Na+Na+Na+

H+

24

Influences On K+ LevelsInfluences On K+ Levels

If H+ concentrations are high (acidosis) than H+ is secreted in greater amounts.

This leaves less K+ than usual excreted.

The resultant K+ retention can affect cardiac function and other systems.

If H+ concentrations are high (acidosis) than H+ is secreted in greater amounts.

This leaves less K+ than usual excreted.

The resultant K+ retention can affect cardiac function and other systems.

K+K+K+

Na+Na+Na+Na+Na+Na+

H+H+H+H+H+H+H+

K+K+K+K+K+

25

SOURCE OF HYDROGEN ION

SOURCE OF HYDROGEN ION

H2CO3

H+

HCO3-

CO2 + H2O H2CO3 H+ + HCO3

-

26

Regulation of Acid Base Balance

Regulation of Acid Base Balance

• Two types of acids are produced in the body:

Volatile acids : CO2 produced during the metabolism of carbohydrates and lipids

Non-volatile acids: metabolism of

protein e.g. sulphuric acids

• Two types of acids are produced in the body:

Volatile acids : CO2 produced during the metabolism of carbohydrates and lipids

Non-volatile acids: metabolism of

protein e.g. sulphuric acids

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Compensatory mechanisms

Compensatory mechanisms

1) Chemical Buffers♥ React very rapidly

(less than a second)

2) Respiratory Regulation♥ Reacts rapidly (seconds to minutes)

3) Renal Regulation♥ Reacts slowly (minutes to hours)

4) Intracellular Shifts of Ions

1) Chemical Buffers♥ React very rapidly

(less than a second)

2) Respiratory Regulation♥ Reacts rapidly (seconds to minutes)

3) Renal Regulation♥ Reacts slowly (minutes to hours)

4) Intracellular Shifts of Ions

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Acid-base buffer systemAcid-base buffer system♣ Maintains the pH by binding with

free hydrogen ions.♣ Combination of weak acid and a

base (unprotonated compound).♣ Three major chemical buffer

systems Bicarbonate system Phosphate system Protein system

♣ Maintains the pH by binding with free hydrogen ions.

♣ Combination of weak acid and a base (unprotonated compound).

♣ Three major chemical buffer systems

Bicarbonate system Phosphate system Protein system

29

BICARBONATE BUFFER SYSTEMBICARBONATE BUFFER SYSTEM• This system is most important because

the concentration of both components can be regulated:♥ Carbonic acid by the respiratory

system♥ Bicarbonate by the renal system

• This system is most important because the concentration of both components can be regulated:♥ Carbonic acid by the respiratory

system♥ Bicarbonate by the renal system

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H2CO3 H+ + HCO3-

♠Hydrogen ions generated by metabolism or by ingestion react with bicarbonate base to form more carbonic acid

H2CO3 H+ + HCO3-

♠Hydrogen ions generated by metabolism or by ingestion react with bicarbonate base to form more carbonic acid

HCO3-H2CO3

31

BICARBONATE BUFFER SYSTEMBICARBONATE BUFFER SYSTEMEquilibrium shifts toward the formation of

acid♥ Hydrogen ions that are lost (vomiting)

causes carbonic acid to dissociate yielding replacement H+ and bicarbonate

Equilibrium shifts toward the formation of acid♥ Hydrogen ions that are lost (vomiting)

causes carbonic acid to dissociate yielding replacement H+ and bicarbonate

H+ HCO3-

H2CO3

32

Loss of HCl

Addition of lactic acid

BICARBONATE BUFFER SYSTEMBICARBONATE BUFFER SYSTEM

H+ HCO3-H2CO3H2OCO2 + +

Exercise

Vomiting

33

Na2HPO4 + H+ NaH2PO4 + Na+

Most important in the intracellular system

Na2HPO4 + H+ NaH2PO4 + Na+

Most important in the intracellular system

PHOSPHATE BUFFER SYSTEMPHOSPHATE BUFFER SYSTEM

H+ Na2HPO4+

NaH2PO4Na++

34

♠Regulates pH within the cells and the urinePhosphate concentrations are higher

intracellular and within the kidney tubules.

More phosphate ions are found in tubular fluids

More powerful thanbicarbonate buffer system

♠Regulates pH within the cells and the urinePhosphate concentrations are higher

intracellular and within the kidney tubules.

More phosphate ions are found in tubular fluids

More powerful thanbicarbonate buffer system

PHOSPHATE BUFFER SYSTEMPHOSPHATE BUFFER SYSTEM

HPO4-2

35

PROTEIN BUFFER SYSTEMPROTEIN BUFFER SYSTEM• Proteins are excellent buffers because they

contain both acid and base groups that can give up or take up H+

• Proteins are extremely abundant in the cell• The more limited number of proteins in the

plasma reinforce the bicarbonate system in the ECF

• Proteins are excellent buffers because they contain both acid and base groups that can give up or take up H+

• Proteins are extremely abundant in the cell• The more limited number of proteins in the

plasma reinforce the bicarbonate system in the ECF

36

Hemoglobin buffers H+ from metabolically produced CO2 in the plasma only

As hemoglobin releases O2 it gains a great affinity for H+

Hemoglobin buffers H+ from metabolically produced CO2 in the plasma only

As hemoglobin releases O2 it gains a great affinity for H+

HbO2

O2 O2

O2

37

• H+ generated at the tissue level from the dissociation of H2CO3 produced by the addition of CO2

• Bound H+ to Hb (Hemoglobin) does not contribute to the acidity of blood

• H+ generated at the tissue level from the dissociation of H2CO3 produced by the addition of CO2

• Bound H+ to Hb (Hemoglobin) does not contribute to the acidity of blood

HbO2

O2 O2

O2

38

• As H+Hb picks up O2 from the lungs the Hb which has a higher affinity for O2 releases H+ and picks up O2

• Liberated H+ from H2O combines with HCO3

-

HCO3- H2CO3 CO2 (exhaled)

• As H+Hb picks up O2 from the lungs the Hb which has a higher affinity for O2 releases H+ and picks up O2

• Liberated H+ from H2O combines with HCO3

-

HCO3- H2CO3 CO2 (exhaled)

HbO2

O2 O2

H+

39

RESPIRATORY CENTRE

RESPIRATORY CENTRE

Respiratory centers

Medulla oblongata

Pons

40

CHEMOSENSITIVE AREASCHEMOSENSITIVE AREAS Chemo sensitive areas of the respiratory

center are able to detect blood concentration levels of CO2 and H+

Increases in CO2 and H+ stimulate the respiratory center♣ The effect is to raise

respiration rates ♣ But the effect

diminishes in1 - 2 minutes

Chemo sensitive areas of the respiratory center are able to detect blood concentration levels of CO2 and H+

Increases in CO2 and H+ stimulate the respiratory center♣ The effect is to raise

respiration rates ♣ But the effect

diminishes in1 - 2 minutes

CO2CO2

CO2CO2CO2

CO2CO2

CO2

CO2

41

RESPIRATORY CONTROL OF pHRESPIRATORY CONTROL OF pH

pH rises toward normal

rate and depth of breathing increase

CO2 eliminated in lungs

H+ stimulates respiratory center in medulla oblongata

H2CO3 H+ + HCO3-

H+ acidosis; pH drops

CO2 + H2O H2CO3

cell production of CO2 increases

42

RENAL RESPONSERENAL RESPONSE• The kidney compensates for Acid - Base

imbalance within 24 hours and is responsible for long term control

• The kidney in response:– To Acidosis

• Retains bicarbonate ions and eliminates hydrogen ions

– To Alkalosis• Eliminates bicarbonate ions and retains

hydrogen ions

• The kidney compensates for Acid - Base imbalance within 24 hours and is responsible for long term control

• The kidney in response:– To Acidosis

• Retains bicarbonate ions and eliminates hydrogen ions

– To Alkalosis• Eliminates bicarbonate ions and retains

hydrogen ions

43

ELECTROLYTE SHIFTSELECTROLYTE SHIFTS

cell

H+

K+

AcidosisCompensatory Response Result

- H+ buffered intracellularly

- Hyperkalemia

H+

K+

cell

AlkalosisCompensatory Response Result

- Tendency to correct alkalosis

- Hypo kalemia

-Diabetic ketoacidosis

44

DISTURBANCE OF ACID BASE BALANCE

DISTURBANCE OF ACID BASE BALANCE

♠Four general categories, depending on the source and direction of the abnormal change in H+ concentrations:

♥ Respiratory Acidosis♥ Respiratory Alkalosis♥ Metabolic Acidosis♥ Metabolic Alkalosis

♠Four general categories, depending on the source and direction of the abnormal change in H+ concentrations:

♥ Respiratory Acidosis♥ Respiratory Alkalosis♥ Metabolic Acidosis♥ Metabolic Alkalosis

45

RESPIRATORY ACIDOSISRESPIRATORY ACIDOSIS

46

RESPIRATORY ACIDOSISRESPIRATORY ACIDOSIS• Caused by hyperkapnia due to

hypoventilation– Characterized by a pH decrease and

an increase in CO2

• Caused by hyperkapnia due to hypoventilation– Characterized by a pH decrease and

an increase in CO2

CO2 CO2

CO2

CO2

CO2

CO2CO2

CO2CO2

CO2

CO2 CO2

CO2

pH

pH

47

RESPIRATORY ACIDOSISRESPIRATORY ACIDOSIS

♥ Respiratory acidosis develops when the lungs don't expel CO2 adequately

♥ Emphysema, chronic bronchitis, severe pneumonia, pulmonary edema, and asthma

♥ Respiratory acidosis develops when the lungs don't expel CO2 adequately

♥ Emphysema, chronic bronchitis, severe pneumonia, pulmonary edema, and asthma

48

RESPIRATORY ACIDOSISRESPIRATORY ACIDOSIS♠ Decreased CO2 removal can

be the result of:1) Obstruction of air

passages2) Decreased respiration

(depression of respiratory centers)

3) Decreased gas exchange between pulmonary capillaries and air sacs of lungs

4) Collapse of lung

♠ Decreased CO2 removal can be the result of:1) Obstruction of air

passages2) Decreased respiration

(depression of respiratory centers)

3) Decreased gas exchange between pulmonary capillaries and air sacs of lungs

4) Collapse of lung

49

4) Collapse of lungCompression injury, open thoracic

wound

4) Collapse of lungCompression injury, open thoracic

wound

Left lung collapsed

50

RESPIRATORY ACIDOSISRESPIRATORY ACIDOSIS

◊ breathing is suppressed holding CO2 in body◊ pH = 7.1

H2CO3

HCO3-

2 20:

CO

2CO

2

CO

2CO

2

51

BODY’S COMPENSATION♠ kidneys conserve HCO3

- ions to restore the normal 40:2 ratio (20:1)♠ kidneys eliminate H+ ion in acidic urine

H2CO3

HCO3-

2 30:

HCO3-

H2CO3

HCO3-

H+

+

acidic urine

52

♠ therapy required to restore metabolic balance♠ lactate solution used in therapy is converted to bicarbonate ions in the liver

H2CO3 HCO3-

2 40:

Lactate

Lactate

LIVER

HCO3-

53

RESPIRATORY ALKALOSISRESPIRATORY ALKALOSIS♣ Normal 20:1 ratio is increased

♣ pH of blood is above 7.4

♣ Normal 20:1 ratio is increased♣ pH of blood is above 7.4

H2CO3 HCO3-

20:= 7.4

H2CO

3 HCO3

-

0.5 20:= 7.4

54

RESPIRATORY ALKALOSISRESPIRATORY ALKALOSIS◊ Cause is Hyperventilation

♥ Leads to eliminating excessive amounts of CO2

♥ Increased loss of CO2 from the lungs at a rate faster than it is produced

♥ Decrease in H+

◊ Cause is Hyperventilation♥ Leads to eliminating excessive amounts of

CO2

♥ Increased loss of CO2 from the lungs at a rate faster than it is produced

♥ Decrease in H+

CO

2

CO

2

CO

2

CO

2

CO

2 CO

2

CO

2CO

2

CO

2

CO

2CO

2

CO

2

55

RESPIRATORY ALKALOSISRESPIRATORY ALKALOSIS• Can be the result of:

1) Anxiety, emotional disturbances

2) Respiratory center lesions3) Fever

4) Salicylate poisoning (overdose)

5) Assisted respiration

6) High altitude (low PO2)

• Can be the result of:1) Anxiety, emotional

disturbances

2) Respiratory center lesions3) Fever

4) Salicylate poisoning (overdose)

5) Assisted respiration

6) High altitude (low PO2)

56

Kidneys compensate by:♣ Retaining hydrogen ions♣ Increasing bicarbonate

excretion

Kidneys compensate by:♣ Retaining hydrogen ions♣ Increasing bicarbonate

excretion

H+

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3- HCO3

-

HCO3-

HCO3-

H+

H+

H+

H+H+

H+

H+

H+

H+

H+

57

RESPIRATORY ALKALOSISRESPIRATORY ALKALOSIS

therapy required to restore metabolic balance HCO3

- ions replaced by Cl- ions

H2CO3 HCO3-

0.5 10:

Cl-

Chloride containing solution

58

METABOLIC ACIDOSISMETABOLIC ACIDOSIS Occurs when there is a decrease in the

normal 20:1 ratio♠Decrease in blood pH and bicarbonate

level

Excessive H+ or decreased HCO3-

Occurs when there is a decrease in the normal 20:1 ratio♠Decrease in blood pH and bicarbonate

level

Excessive H+ or decreased HCO3-

H2CO3 HCO3-

1 20:= 7.4

H2CO3

HCO3-

1 10:= 7.4

59

METABOLIC ACIDOSISMETABOLIC ACIDOSIS♣ Acidosis results from excessive loss of HCO3

- rich fluids from the body or from an accumulation of acids.♣ Accumulation of non-carbonic plasma

acids uses HCO3- as a buffer for the

additional H+ thus reducing HCO3- levels

♣ Acidosis results from excessive loss of HCO3-

rich fluids from the body or from an accumulation of acids.♣ Accumulation of non-carbonic plasma

acids uses HCO3- as a buffer for the

additional H+ thus reducing HCO3- levels

Lactic Acid

Muscle Cell

60

METABOLIC ACIDOSISMETABOLIC ACIDOSIS Metabolic acidosis is always

characterized by a reduction in plasma HCO3

- while CO2 remains normal

Metabolic acidosis is always characterized by a reduction in plasma HCO3

- while CO2 remains normal

HCO3-

CO2

Plasma Levels

61

METABOLIC ACIDOSISMETABOLIC ACIDOSISThe causes of metabolic acidosis can be

grouped into five major categories;

1) Ingesting an acid or a substance that is metabolized to acid

2) Abnormal Metabolism3) Kidney Insufficiencies4) Strenuous Exercise5) Severe Diarrhea

The causes of metabolic acidosis can be grouped into five major categories;

1) Ingesting an acid or a substance that is metabolized to acid

2) Abnormal Metabolism3) Kidney Insufficiencies4) Strenuous Exercise5) Severe Diarrhea

62

METABOLIC ACIDOSISMETABOLIC ACIDOSIS Treating the underlying cause of

metabolic acidosis is the usual course of action♥ Control diabetes with insulin or treat

poisoning by removing the toxic substancefrom the blood

♥ Occasionallydialysis is neededto treat severeoverdoses andpoisonings

Treating the underlying cause of metabolic acidosis is the usual course of action♥ Control diabetes with insulin or treat

poisoning by removing the toxic substancefrom the blood

♥ Occasionallydialysis is neededto treat severeoverdoses andpoisonings

63

METABOLIC ACIDOSISMETABOLIC ACIDOSIS

Metabolic acidosis may also be treated directly♥ If the acidosis is mild,

intravenous fluids and treatment for the underlying disorder may be all that's needed

Metabolic acidosis may also be treated directly♥ If the acidosis is mild,

intravenous fluids and treatment for the underlying disorder may be all that's needed

64

METABOLIC ACIDOSISMETABOLIC ACIDOSIS

When acidosis is severe, bicarbonate may be given intravenously♥ Bicarbonate provides

only temporary relief.

When acidosis is severe, bicarbonate may be given intravenously♥ Bicarbonate provides

only temporary relief.

65

METABOLIC ALKALOSISMETABOLIC ALKALOSIS♣ Elevation of pH due to an increased 20:1

ratio May be caused by:

• An increase of bicarbonate • A decrease in hydrogen ions

Imbalance again cannot be due to CO2

Increase in pH which has a non-respiratory origin

♣ Elevation of pH due to an increased 20:1 ratio May be caused by:

• An increase of bicarbonate • A decrease in hydrogen ions

Imbalance again cannot be due to CO2

Increase in pH which has a non-respiratory origin 7.4

66

METABOLIC ALKALOSISMETABOLIC ALKALOSIS A reduction in H+ in the case of

metabolic alkalosis can be caused by a deficiency of non-carbonic acids

This is associated with an increase in HCO3

-

A reduction in H+ in the case of metabolic alkalosis can be caused by a deficiency of non-carbonic acids

This is associated with an increase in HCO3

-

67

METABOLIC ALKALOSISMETABOLIC ALKALOSIS

• Can be the result of:1. Ingestion of Alkaline Substances2. Vomiting ( loss of HCl )

• Can be the result of:1. Ingestion of Alkaline Substances2. Vomiting ( loss of HCl )

68

METABOLIC ALKALOSISMETABOLIC ALKALOSIS• Gastric juices contain large amounts of HCl

• During HCl secretion, bicarbonate is added to the plasma

K+ H+

Cl-

HCO3-

HCl

69

HCl

METABOLIC ALKALOSISMETABOLIC ALKALOSIS

K+H+ Cl-

HCO3-

• The bicarbonate is neutralized as HCl is reabsorbed by the plasma from the digestive tract

H2CO3

70

HCl K+

HCO3-

During vomiting H+ is lost as HCl and the bicarbonate is not neutralized in the plasma

♥ Loss of HCl increases the plasma bicarbonate and thus results in an increase in pH of the blood

Bicarbonate not neutralized

71

H2CO

3HCO3

-

BODY’S COMPENSATION♥ breathing suppressed to hold CO2

♥ kidneys conserve H+ ions and eliminate HCO3

- in alkaline urine

1.25 30

CO2 + H2O

HCO3- + H+

HCO3-

H+

+

Alkaline urine:

72

METABOLIC ALKALOSISMETABOLIC ALKALOSIS

♠ Therapy required to restore metabolic balance

♠ HCO3- ions replaced by Cl- ions

H2CO3 HCO3-

1.25 25:

Cl-

Chloride containing solution

73

ACID – BASE DISORDERSACID – BASE DISORDERS

Clinical State Acid-Base Disorder

Pulmonary Embolus Respiratory Alkalosis

Cirrhosis Respiratory Alkalosis

Pregnancy Respiratory Alkalosis

Diuretic Use Metabolic Alkalosis

Vomiting Metabolic Alkalosis

Chronic Obstructive Pulmonary Disease Respiratory Acidosis

Shock Metabolic Acidosis

Severe Diarrhea Metabolic Acidosis

Renal Failure Metabolic Acidosis

Sepsis (Bloodstream Infection) Respiratory Alkalosis,Metabolic Acidosis

74

CLINICAL EVALUATION OF DISTURBANCES IN ACID BASE

STATUS

CLINICAL EVALUATION OF DISTURBANCES IN ACID BASE

STATUS

75

ANION GAPANION GAP• The term anion gap (AG) represents the

concentration of all the unmeasured anions in the plasma.

• The negatively charged proteins account for about 10% of plasma anions.

Reference range is 8 to 16 mmol/l.

• The term anion gap (AG) represents the concentration of all the unmeasured anions in the plasma.

• The negatively charged proteins account for about 10% of plasma anions.

Reference range is 8 to 16 mmol/l.

Anion gap = [Na+] - [Cl-] - [HCO3

-]

AG = [Na+] + [K+] - [Cl-] - [HCO3

-]

76

Major Clinical Uses of the Anion Gap

Major Clinical Uses of the Anion Gap

♥ To signal the presence of a metabolic acidosis and confirm other findings.

♥ Help differentiate between causes of a metabolic acidosis.

ORGANIC INORGANIC

♥ To assist in assessing the biochemical severity of the acidosis and follow the response to treatment .

♥ To signal the presence of a metabolic acidosis and confirm other findings.

♥ Help differentiate between causes of a metabolic acidosis.

ORGANIC INORGANIC

♥ To assist in assessing the biochemical severity of the acidosis and follow the response to treatment .

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General Factors affecting Acid-Base Balance in Infants

General Factors affecting Acid-Base Balance in Infants♠ Low Bicarbonate depends on Gestational Age♥ lower renal threshold ♥ lower capacity to reabsorb HCO3

-

♣ Very low birth weight babies: bicarbonate levels of 12-16 mmoles/l

♣ Term babies : levels of 20-22 mmol/l.

♠ Low Bicarbonate depends on Gestational Age♥ lower renal threshold ♥ lower capacity to reabsorb HCO3

-

♣ Very low birth weight babies: bicarbonate levels of 12-16 mmoles/l

♣ Term babies : levels of 20-22 mmol/l.

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The rate of metabolism in infants is twice as great in relation to body mass as in adults

Twice as much acid is formed which leads to a tendency toward acidosis

Functional development of kidneys is not complete until the end of the first month

Renal regulation of acid base may not be optimal.

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Low Reserve to excrete an Acid Load

Low Reserve to excrete an Acid Load

♥ Term infants, acid excretion is working near maximum capacity and there is little reserve to deal with acidosis.

♥ Preterm babies less capacity than a term neonate to buffer an acid load.

♥ Term infants, acid excretion is working near maximum capacity and there is little reserve to deal with acidosis.

♥ Preterm babies less capacity than a term neonate to buffer an acid load.

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Other FactorsOther Factors• Growth results in deposition of base in

new bone as the calcium salts in bone are alkaline salts.

• On a weight basis, fixed acid production is higher than in adults.

Neonates and children < 12 months

fixed acid production is 2 to 3 mmol/kg/day).

• Growth results in deposition of base in new bone as the calcium salts in bone are alkaline salts.

• On a weight basis, fixed acid production is higher than in adults.

Neonates and children < 12 months

fixed acid production is 2 to 3 mmol/kg/day).

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Infantile Metabolic Acidosis

 

Infantile Metabolic Acidosis

 Different inborn errors of metabolism cause a metabolic acidosis:

organic acidosis (enzyme defect resulting in accumulation of acidic metabolic intermediates)

lactic acidosis hyperchloraemic acidosis

Feeding difficulties often in association with tachypnoea

Different inborn errors of metabolism cause a metabolic acidosis:

organic acidosis (enzyme defect resulting in accumulation of acidic metabolic intermediates)

lactic acidosis hyperchloraemic acidosis

Feeding difficulties often in association with tachypnoea

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• Lactic acidosis : enzyme defects and present during childhood.

♥ pyruvate carboxylase deficiency♥ fructose-1,6-diphosphatase

deficiency ♥ pyruvate dehydrogenase deficiency.

not an isolated finding as these children have serious dysfunctions of organ systems esp. affecting brain, liver and muscle.

• Lactic acidosis : enzyme defects and present during childhood.

♥ pyruvate carboxylase deficiency♥ fructose-1,6-diphosphatase

deficiency ♥ pyruvate dehydrogenase deficiency.

not an isolated finding as these children have serious dysfunctions of organ systems esp. affecting brain, liver and muscle.

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Other Acid-Base Disorders in Children

Other Acid-Base Disorders in Children

• Insulin dependent diabetes mellitus usually presents during childhood or adolesence.

• Poisoning in children may cause an acid-base disorder

• Insulin dependent diabetes mellitus usually presents during childhood or adolesence.

• Poisoning in children may cause an acid-base disorder

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REFERENCESREFERENCES• Fundamentals of physiology: a human

perspective: Lauralee Sherwood; Fluid and acid base balance; page:453-61

• Essentials of medical physiology: K Sembulingam; Acid base balance:36-47

• Ganong’s Review of Medical Physiology: Renal physiology: 679-682

• Fundamentals of physiology: a human

perspective: Lauralee Sherwood; Fluid and acid base balance; page:453-61

• Essentials of medical physiology: K Sembulingam; Acid base balance:36-47

• Ganong’s Review of Medical Physiology: Renal physiology: 679-682

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THANK YOUTHANK YOU

Presented by:

Dr. Ruby Kharkwal

1st year postgraduate student

Department of Pedodontics

Presented by:

Dr. Ruby Kharkwal

1st year postgraduate student

Department of Pedodontics