DISORDERS OF ACID-BASE BALANCE · 2020. 10. 2. · ALKALAEMIA ALKALOSIS pH of arterial blood < 7,35 ... –stimulation of resp. center fear, anxiety, hysterical fit –hyperventilation

DISORDERS OF

ACID-BASE

BALANCE

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ACID-BASE BALANCE

ISOHYDRIA – stability of H+ concentration

[H+] = 40 nmol/L = 0,00000004 mol/L

pH = - log [H+]

ACID-BASE BALANCE

ISOHYDRIA – stability of H+ concentration

[H+] = 40 nmol/L = 0,00000004 mol/L

pH = - log [H+]

pH → main determinant of physiological & biochemical processesactivity of enzymes varies due to charge and conformation of proteins

effecting activity of transport proteinseffecting molecule distributions across cell membranesalterations in drug dissociation

pH

Physiological value of pH?

pH

pH 7,4 ± 0,05

pH 7,4 pH 7,35

sources of H + :

1. the metabolism of proteins and phospholipids + incomplete metabolism of fatty acids and carbohydrates

→ non-volatile acids (40 mmol/d)

sulfuric acid phosphoric acid

lactic acid ketone bodiesuric acid

• no further dissociation• elimination by kidneys

2. complete metabolism of fatty acids & carbohydrates

→ CO2 (20 000 mmol/d)

ACID-BASE BALANCE

H+ source

fixed acids CO2

CO2 + H2O H 2CO3 H+ + HCO3

–

MECHANISMS FOR MAINTAINING AB BALANCE

1. bicarbonate – carbonic buffer

2. hemoglobin buffer

3. protein buffer

4. phosphate buffer

BUFFERING SYSTEMS:

buffer systems

ECF

bicarbonate

protein

ICF

hemoglobin

phosphate

BICARBONATE –CARBONIC BUFFER

efficient:• biggest in extracellular fluid • open system

BUFFERING SYSTEM:


–

weak acid strong base



–

pH = [HCO3

–][H2CO3]pCO2

Henderson-Hesselbach‘sequation

pH = pK + log [HCO3

–][H2CO3]

pH = pK + log [HCO3

–][H2CO3]

24 mmol/L

1,2 mmol/L6,37,4


CO2 transport

• CO2 diffuse into plasma- 90% in RBC• carbon anhydrase – H2C03 production

(H+, HCO3-)• H+ ion binds to HGB (HGB buffering)

• HCO3- diffuse into plasma• in lung capillaries - ox. HGB

H+ release• H2CO3 synthesis (H2O + CO2)


elimination of H + elimination of non-volatilereabsorption of HCO3

– acidsHPO42- + H + → H2PO4NH3 + H + → NH4+


BICARBONATE –CARBONIC BUFFER: open system

pCO2 HCO3–

↓↑ reabsorption of HCO3–

prox. & distal. tubule– dissociation of H2CO3

H+ elimination into tubular fluidHCO3

– reabsorbed

elimination of CO2

ventilation regulated by respiratory center (med. oblongata)responding via alteration in

frequency & depth

respiratory component onset – minutes

metabolic componentonset – days

H+ + HCO3– H2CO3 CO2 + H2O



ACIDAEMIA ACIDOSIS

ALKALAEMIA ALKALOSIS

pH of arterial blood < 7,35

pH of arterial blood > 7,45

processes resulting in pH decrease

• ↓ serum HCO3–

• ↑ pCO2

processes resulting in pH increase

• ↑ serum HCO3–

• ↓ pCO2

pH = [HCO3

–]

pCO2

pH HCO3– pCO2 compensation

physiological values 7,4 ± 0,05 24± 2 mmol/L5,3 ± 0,5 kPa(40 mmHg)

Metabolic acidosis

Metabolic alkalosis

Respiratory acidosis

Respiratory alkalosis

primary change

compensatory change

hyperventilation

ACID-BASE BALANCE

respiratory compensation of metabolic acidosis:KUSSMAUL BREATHING pattern

ACID-BASE BALANCE

pH = [HCO3

–]

pCO2


physiological values 7,4 ± 0,05 24± 2 mmol/L5,3 ± 0,5 kPa(40 mmHg)

Metabolic acidosis

Metabolic alkalosis


Respiratory alkalosis

primary change

compensatory change

hyperventilation

hypoventilation ?

ACID-BASE BALANCE

ACID-BASE BALANCE

anion deficiency, AG

AG = [Na+] – ([Cl –] + [ HCO3–])

AG = 140 – (104 + 24) = 12 mmol/L (norm 8-12 mmol/L)

albumin, phospate, sulphate, lactate

ANION GAP

accumulation of anions

reaction with HCO3–

AG

METABOLIC ACIDOSIS

pH < 7,35 primary decrease of HCO3–

pH = [HCO3

–]

pCO2


physiological value 7,4 ± 0,05 24± 2 mmol/L 5,3 ± 0,5 kPa(40 mmHg)

Metabolic acidosis

concentration of plasma HCO3

– < 22 mmol/L

DISORDERS OF ACID-BASE BALANCE

pH < 7,35 primary decrease of HCO3–

1. reaction with H + (non-volatile acids) • ↑ intake of substances producing H +

• metabolic production of non-volatile acids

• ↓ excretion of H +

2. ↑ losses of HCO3–

concentration of plasma HCO3

–< 22 mmol/L

METABOLIC ACIDOSIS


intoxication by salicylates – metabolic block

intoxication by inorganic acids

ketoacidosis: insufficient glucose utilization

1. reaction with H + (acids)

METABOLIC ACIDOSIS


intoxication by salicylates – metabolic block

intoxication by inorganic acids

ketoacidosis: insufficient glucose utilization

diabetic: fatty acids oxidation – source H +

hyperkalemiastarvation: (fever with anorexia - mild ketoacidosis)

reduced carbohydrates intake →↓ insulin secretion ↑ glucagon secretion

alcoholic

H+

K+

H+ H+

H+

1. reaction with H + (acids)

METABOLIC ACIDOSIS


lactic acidosis: lactate overproduction

type A: circulatory shock, heart failure, anemia, CO poisoningtype B: organ failure (kidney, liver), malignant tumors

intoxication by methanol, etylene glycol, paraldehyd

METABOLIC ACIDOSIS


2. ↑ losses of HCO3–

hyperchloremic acidosis

severe diarrhea – loss of HCO3–, Na+, K+, H2O

chronic vomiting –loss of duodenal content (pH 7-8,5),loss of HCO3– > gastric acidsaccumulation of Cl-

renal tubular acidosis –↓ H+ excretion & HCO3

– loss

chronic renal insufficiency: ↓ H + excretionloss of functional parts of kidney parenchyma↓ nb of nephrons - SO4

2- , PO43- , organic aids accumulation

normal Anion GAP

METABOLIC ACIDOSIS


METABOLIC ACIDOSIS


K+

H+ H+

H+

compensatory hyperventilation KUSSMAUL BREATHING

↓ pH – stimulation of peripheralreceptors

H+ crossing blood-brain barrier↓ pH - in respiratory center in

medulla oblongata

METABOLIC ACIDOSIS


pH = [HCO3

–]

pCO2


Physiological values 7,4 ± 0,05 24± 2 mmol/L 5,3 ± 0,5 kPa(40 mmHg)

metabolic alkalosis

pH > 7,45 primary increase of HCO3–

concertation of plasma HCO3

– > 26 mmol/L


METABOLIC ALKALOSIS

pH > 7,45 primary increase of HCO3–

concentration ofplasma HCO3

– > 26 mmol/L

1. ↑ concentration of HCO3–

• ↑ intake (IV infusion, oral intake)

• ↓ excretion

2. ↑ loss of acids (hydrochloric acid)


METABOLIC ALKALOSIS

↑ intake:

intravenous infusion

oral intake – huge capacity for elimination in healthy kidneys

blood transfusion – sodium citrate (anticoagulant)

↓ excretion:primary hyperaldosteronismadministration of mineralocorticoids↑ aldosterone –Na + reabsorption, HCO3

– reabsorptionK + & H+ elimination

1. ↑ concentrations of HCO3–


METABOLIC ALKALOSIS

hypochloremic alkalosis:

vomitingremoval of gastric content

loss of gastric acid = loss of HCl

dehydration↓ ECF - RAAS activation –↑ release of aldosterone

→ retention of Na+ a H2O→ loss of H +

2. ↑ losses of acids

normal Anion Gap


METABOLIC ALKALOSIS


METABOLIC ALKALOSIS

K+K+

K+

pH = [HCO3

–]

pCO2


physiological values 7,4 ± 0,05 24± 2 mmol/L 5,3 ± 0,5 kPa(40 mmHg)


pH < 7,36 primary increase in pCO2

pCO2 > 5,8 kPa


RESPIRATORY ACIDOSIS

pH < 7,36 primary increase in pCO2pCO2 > 5,8 kPa

exhaled CO2 < metabolic production

HYPERCAPNIA



ACUTE: failure of ventilation & depression of resp. center

cardiopulmonal failure – sudden failure in ventilation & perfusionpulmonary embolization, heart failure

drugs intoxication (hypnotics, sedatives, morphium) depression of respiratory center

trauma, infection, ischemia of CNS – local damage

CHRONIC: ↓ alveolar ventilation

chronic obstructive pulmonary disease (emphysema, bronchitis)

↓ effective alveolar ventilationsufficient renal compensation: ↑ HCO3

– reabsorptionadaptation to hypoxemia →↑ nb of RBC (erythrocythemia)



pH > 7,44 primary decrease in pCO2

pCO2 < 4,8 kPa

pH = [HCO3

–]

pCO2


physiological values 7,4 ± 0,05 24± 2 mmol/L 5,3 ± 0,5 kPa(40 mmHg)

respiratory alkalosis


RESPIRATORY ALKALOSIS

pH > 7,44 primary decrease in pCO2pCO2 < 4,8 kPa

HYPOCAPNIA

exhaled CO2 > metabolicproduction



CNS DISORDERS

cerebrovascular incidents – hypoxia in area of resp. center

trauma, inflammation, tumors – stimulation of CNS

drugs (salicylates, progesterone) – stimulation of resp. center

fear, anxiety, hysterical fit – hyperventilation due to subjective feeling of air shortage

LUNG DISEASE

gas exchange disorders – ventilation/perfusion imbalance

pulmonary fibrosis, edema, pneumonia, asthma

mountain sickness↓ pO2 stimulation of hyperventilation



MIXED ACID-BASE DISORDERS

acute disorder

chronic disorderCOMPENSATION

metabolic acidosis + metabolic alkalosis

metabolic acidosis + respiratory acidosis

diarrhea + vomiting

circulatory failure: lactic acidosis + respiratory failure

↓HCO3– /↑ HCO3

–

↓HCO3– /↑ pCO2


COMPENSATION OF AB DISORDERS

Uncompensated disorder:• pH – abnormal• HCO3 – conc. or pCO2 - abnormal

Partially compensated disorder:• pH – abnormal• HCO3 – conc. - abnormal• pCO2 – abnormal

Compensated disorder:• pH – normal• HCO3 – conc. – abnormal but neutralized• pCO2 – abnormal but neutralized

Corrected disorder:• pH – normal• HCO3 – conc. – normal (returned to physiological value)• pCO2 – normal (returned to physiological value)



VIDEOs explaining AB disorders

Introduction to Acid-Base Disorders:https://www.youtube.com/watch?v=jWpKJVop6G8

Metabolic acidosis - The Acid-Base Serieshttps://www.youtube.com/watch?v=IF6oF5H43Ac

Metabolic alkalosis - The Acid-Base Serieshttps://www.youtube.com/watch?v=Wf0ruPTmP1o&list=PLN4mLNb7L4VeCRfA7kB2Sj0sYvaxW4KB5&index=4

Respiratory acidosis - The Acid-Base Serieshttps://www.youtube.com/watch?v=wZICSJZOTH4&list=PLN4mLNb7L4VeCRfA7kB2Sj0sYvaxW4KB5&index=3

Respiratory alkalosis - The Acid-Base Serieshttps://www.youtube.com/watch?v=7aPzaVkCjss&list=PLN4mLNb7L4VeCRfA7kB2Sj0sYvaxW4KB5&index=2
https://www.youtube.com/watch?v=jWpKJVop6G8https://www.youtube.com/watch?v=IF6oF5H43Achttps://www.youtube.com/watch?v=Wf0ruPTmP1o&list=PLN4mLNb7L4VeCRfA7kB2Sj0sYvaxW4KB5&index=4https://www.youtube.com/watch?v=wZICSJZOTH4&list=PLN4mLNb7L4VeCRfA7kB2Sj0sYvaxW4KB5&index=3https://www.youtube.com/watch?v=7aPzaVkCjss&list=PLN4mLNb7L4VeCRfA7kB2Sj0sYvaxW4KB5&index=2

DISORDERS OF ACID-BASE BALANCE · 2020. 10. 2. · ALKALAEMIA ALKALOSIS pH of arterial blood < 7,35 ... –stimulation of resp. center fear, anxiety, hysterical fit –hyperventilation

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