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FunMed Physiology > Acid base > Flashcards

Acid base Flashcards

1
Q

what is the acid base balance

A
  • This is the regulation of hydrogen ions
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2
Q

what is measured as pH

A
  • The acid or alkalinity of a solution is measured as pH
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3
Q

the more acidic a solution….

A

the greater the [H+] and the lower the pH

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4
Q

the more alkaline a solution…

A

the lower the [H+] and the higher the pH

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5
Q

write the equation for finding out pH

A 
pH = 1/[H+]
pH = -log10[H+]
[H+] = 10-pH
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6
Q

whats the pH of the ECF

A

7.35-7.45

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7
Q

if plasma levels falls below 7.35 what happens

A

academia which results in acidosis

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8
Q

if plasma levels rise above 7.45

A

alkalemia happens which results in alkalosis

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9
Q

what happens if the pH rises or drops

A

can result in

  • circulatory collapse
  • coma
  • death
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10
Q

why is pH concentration important

A
  • hydrogen ions alter concentration on the operation of many cellular enzymes and function of vital organs, most prominently the brain and the heart, effects tertiary structure and ions move across boundaries that they do not need to
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11
Q

name 4 metabolic sources of Hydrogen ions

A
  • carbohydrates
  • proteins
  • fats
  • DNA
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12
Q

how does acid come from

  1. Carbonhydrates
  2. Protiens
  3. fats
  4. DNA
A
  1. aerobic respiration of glucose leads to carbonic acid, anaerobic respiration of glucose leads to lactic acid
  2. oxidation of sulphur containing amino acids leads to sulfuric acid
  3. incomplete oxidation of fatty acids causes acidic ketone bodies
  4. hydrolysis of phosphoproteins and nucleic acids leads to phosphoric acid
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13
Q

whats the pH of water

A

7 and its neutral

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14
Q

each unit in pH…

A

represents a 10 fold in hydrogen ions e.g..

10-9 = 9pH

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15
Q

name the 3 ways to maintain pH

A
  • chemical buffers
    excretion of an acid
  • respiration regulation
  • renal regulation
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16
Q

How fast does chemical buffers act

A

these react very rapidly (less than a second) and absorb and neutralise the hydrogen ions
- have a range that they act between

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17
Q

why do we need excretion of the acid

A

eventually have to excrete the hydrogen ions oterhwise chemical buffers will run out

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18
Q

what are the two ways that we excrete acids

A

respiration regulation

renal regulation

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19
Q

How fast does respiration regulation work and renal regulation work

A
  • Respiration regulation – reacts rapidly (seconds to minutes)
  • Renal regulation – reacts slowly (hours to days)
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20
Q

where do chemical buffers occur in

A

ICF and ECF

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21
Q

what are the chemical buffers specific to ICF

A
  • Phosphate buffer system

- Protein buffer system including – amino acid buffers, and haemoglobin buffer system (2nd largest)

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22
Q

what are the chemical buffers specific to the ECF

A
  • Carbonic acid bicarbonate buffer system – largest

- Protein buffer systems – these include amino acid buffers and plasma protein buffers

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23
Q

Define a buffer

A
  • A buffer is a solution that can maintain a nearly constant pH if it is diluted or if strong acids or bases are added, a buffer solution consists of a mixture of weak acids and its conjugate base or a weak base and its conjugate acid
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24
Q

how does the phosphate buffer system work

A
  • H+ + HPO42- <=> H2PO4-
  • This system is of minor relevance in the ECF but is important as part of the renal regulation mechanism/in the urine
  • Equal rate of association and disassociation, relative amounts are the same but there is a constant
  • Works in law of mass, needs to reach an equilibrium, law of mass changes principles
  • important in kidney to create hydrogen ions to excrete in the urine
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25
Q

how does protein buffer system work

A
  • Mechanism: acidic and basic side chains can give up or take up H+ therefore acting as a weak acid or base
  • If the pH climbs the carboxyl group of the amino acid acts as a weak acid and donates the hydrogen
  • If the pH drops the amino group acts as a weak base and the amine group accepts a hydrogen
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26
Q

How does the haemoglobin buffer system works

A
  • Can buffer changes in H+ caused by CO2 levels
  • H+ + Hb <=> HHB
  • useful because of carriage to an excretion mechanism
  • In tissues
  • High hydrogen ion concentration causes shift of oxygen dissociation curve to the right to cause oxygen to be released from Hb to tissues and instead H+ binds to Hb
  • CO2 +H20 = H2CO3 = H+ + HCO3-
  • H+ + Hb  HHb
  • In lungs
  • HHB releases H+ and takes up O2, not so much hydrogen because its being released into the lungs as hydrogen can combine with hydrogen carbonate and release carbon dioxide
  • So H+ + HCO3- = H2CO3 = H20 + CO2
  • And the carbon dioxide is exhaled
  • When it gets to the lungs it donates the hydrogen and takes up O2
  • In tissues it accepts hydrogen ion
  • Reversible reaction
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27
Q

How does the bicarbonate/carbon dioxide buffer system works

A
  • Abundant in ECF (extracellular fluid)
  • CO2 + H20 <=> H2CO3 <=> H+ + HCO3-
  • Can buffer H+ from any other source other than CO2
  • This is useful because of carriage to an excretion mechanism
  • It can dissociate to make hydrogen ions and carbonate or can dissociate to make carbon dioxide and water
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28
Q

what solution volume makes up the buffer in the blood

A
  • Bicarbonate 18MmolesH+I-1
  • Haemoglobin 8 MmolesH+I-1
  • Protein 1.7 MmolesH+I-1
  • Phosphate 0.3 MmolesH+I-1
  • Total = 28 MmolesH+I-1
29
Q

How does respiratory regulation remove hydrogen ions and regulate the acid base balance

A

Lungs

  • Help regulate acid-base balance by eliminating or retaining carbon dioxide
  • Changes in pH are rapid and occur in minutes
30
Q

how to the kidneys regulate acid base balance

A
  • The long term regulator of acid base balance
  • Slower to respond – may take hours or days to correct pH
  • Kidneys maintain balance by excreting or conserving bicarbonate and hydrogen ions
  • Amount of bicarbonate is reabsorbed determines how much hydrogen ions are excreted
31
Q

how do you remove hydrogen ions using renal regulation

A

The removal of hydrogen ions in the urine
- Conjugated in the urine with urinary buffers
- Excreted as titratable acids and ammonium
Reabsorption or excretion of the bicarbonate
- This happens from the glomerular filtrate
- Hydrogen ions excreted, buffered by ammonia and phosphate
- Balance of acid/alkaline urine regulates ECF acid base balance

32
Q

what is the long term regulator of acid base balance

A

the kidney

33
Q

what is the equation of Ka

A

Ka = [H+][HCO3-]/[H2CO3]

34
Q

what is the equation to work out hydrogen ion s

A

Ka x [H2CO3]/[HCO3]

35
Q

how do you work out acidity (pH)

A

Bicarbonate/carbon dioxide

36
Q

what are the four things that can go wrong that affects acidity

A
  • Bicarbonate increase
  • Bicarbonate decreases
  • Carbon dioxide increase
  • Carbon dioxide decrease
37
Q

How do you diagnose acid base balance disorder

A
  • Clinical history
  • Physical examination
  • Arterial blood gas analysis
38
Q

what are the two types of disorders that are the cause of acid base disorders

A
  • respiratory acid base disorders

- metabolic acid base disorder

39
Q

what is a respiratory acid base disorder

A

result when abnormal respiratory function causes rise or fall in carbon dioxide in the ECF

40
Q

what is a metabolic acid base disorder

A

generation of organic or fixed acids, anything affecting concentration of bicarbonate ions in ECF

41
Q

what is measured in the arterial blood gas printout

A
  • pCO2
  • pO2
  • pH
  • anion gap
  • Hb saturation is calculated from pO2 - how much of the haemoglobin has oxygen associated with it
  • HCO3 standard HCO3,
42
Q

how do you interpret the set of blood gases

A
  1. Look at the pH
    - If it is above 7.45 it is alkalosis
    - If it is below 7.35 it is acidosis
  2. Check the carbon dioxide which is a respiratory indicator
  3. Check the HCO3 which is a metabolic indicator
  4. Which is primary disorder respiratory or metabolic
    - If the pH is low (acidosis) then look to see if CO2 or HCO3 caused this
    - If carbon dioxide is high = respiratory problem = respiratory acidosis caused this
    - Bicarbonate is low = metabolic problem = metabolic acidosis caused this
    - If the pH is high (alkalosis), then look to see if carbon dioxide or HCO3 caused this
    - Carbon dioxide is low – respiratory problem – respiratory alkalosis
    - Bicarbonate is high = metabolic problem = metabolic alkalosis
43
Q

what does respiratory acidosis result from

A
  • Results from excessive levels of carbon dioxide in the body
44
Q

describe how respiratory acidosis is fixed by homeostasis

A
  1. Homeostasis is disturbed – hypoventilation causing increased pCO2 retention
  2. Stimulation of the arterial and CSF receptors
  3. Respiratory compensation which is increased respiratory rate
  4. Decreases the pCO2
  5. Homeostasis is restored
  6. Or respiratory acidosis, renal compensation or buffer systems that work
45
Q

what causes the mechanism of resrpaitory acidosis

A 
-	Mechanism – hypoventilation or excess carbon dioxide production 
Etiology (due to)
-	COPD - airway obstruction 
-	Neuromuscular disease
-	Respiratory centre depression 
-	Late ARDS
-	Inadequate mechanical ventilation 
-	Sepsis or burns
46
Q

what will you see in the ABG of respiratory acidosis

A
  • pH will fall
  • Carbon dioxide will rise
  • Bicarbonate rise if compensation occurs
  • organic base may increase to compensate
47
Q

What is associated by respiratory alkalosis

A
  • associated with hyperventilation
48
Q

describe the homeostasis of respiratory alkalosis

A
  1. homeostatic is disturbed caused by hyperventilation which causes decrease in pCO2
  2. inhibition of arterial and CSF chemoreceptors
  3. respiratory compensation and decrease respiratory rate
  4. this results in increase carbon dioxide concentration
  5. homeostasis is restored
  6. or buffer systems and renal compensation
49
Q

what are the risk factors of respiratory alkalosis

A
  • extreme anxiety, stress or pain
  • fever
  • overventilation with ventilator
  • hypoxemia
  • CAN trauma or tumor
50
Q

what will you see in respiratory alkalosis ABG

A
  • pH will rise
  • carbon dioxide will fall
  • bicarbonate will fall to compensate
  • Carbon dioxide falls
51
Q

what is the cause of metabolic acidosis

A
  • Excess acid retention – this is the inability to excrete hydrogen ions via kidneys, production of large numbers of fixed/organic acids such as lactate and keto acids
  • Excess bicarbonate loss – e.g. bicarbonate loss due to chronic diarrhoea
  • Toxins – antifreeze
52
Q

what happens in homeostasis is distributed by metabolic acidosis

A

two ways
way number 1
- increased production of hydrogen ions or decrease in hydrogen ion excretion
- this results in decrease pH
- the buffer systems other than carbonic acid- bicarbonate system absorb hydrogen ions
way 2
- bicarbonate ion loss depletion of bicarbonate reserve
- normal generation of metabolic acid
- decrease pH
- increased carbon dioxide saturation
- respiratory compensation which results in increased respiratory rate
- decreased carbon dioxide percentage
decreased pH also result in renal compensation which increases hydrogen ion secretion and decreases HCO3- generation

53
Q

what are the risk factors of metabolic acidosis

A

the conditions that increase acids in the blood

  • renal failure
  • DKA
  • Starvation
  • Lactic acidosis
  • Prolonged diarrhea
  • Toxins
  • Carbonic anhydrase inhibitors such as Diamox
54
Q

what will you see in metabolic acidosis ABG

A
  • pH falls
  • bicarbonate falls
  • carbon dioxide falls to compensate
55
Q

when does metabolic alkalosis occur

A

 Occurs when HCO3- concentrations become elevated
 Caused by retention of carbohydrate
 Or loss of organic acid eg: repeated vomiting

56
Q

what is the homeostasis associated with metabolic alkalosis

A
  1. Homeostatsis is normal
  2. Then distrubted due to loss of hydrogen ions and gain of HCO3-
  3. Increased HCO3- results in renal compensation which generated hydrogen ions and HCO3- secretion
  4. Increases pH – buffer systems other than carbonic acid bicarbonate system donate hydrogen ions
  5. Respiratory compensation – decrease respiratory rate
  6. Results in increase in pCO2
57
Q

what are the risk factors that cause metabolic alkalosis

A 
	Acid loss due to
	vomiting
	gastric suction
	Loss of potassium due to
	steroids
	diuresis
	Antacids (overuse of)
58
Q

what will you see with metabolic alkalosis ABG

A
  • pH will rise
  • bicarbonate rises
  • carbon dioxide rises if compensation takes place
59
Q

what is the anion gap

A

the contribution of unmeasured anions to acidosis

- difference between positive and negative ions

60
Q

what is pH

A
  • Concentration of hydrogen ions in a solution
61
Q

whats the difference between arterial and Venus blood

A
  • arterial blood is low in carbon doxide therefore slightly more alkalotic and a low pH
  • venus blood has more carbon dioxide and is more acidic therefore it is a higher pH
62
Q

How do buffers in general work

A

If there is a higher hydrogen ion concentration the hydrogen ion will combine with the anion salt and form more weak acid therefore the equilibrium will shift left, to decrease hydrogen ion concentration
If there is a higher base concentration, more water will form and more weak acid will dissociate therefore the equilibrium will shift left to increase hydrogen ion concentration and anion salt concentration

63
Q

why can the bicarbonate system not buffer carbon dioxide

A
  • This is because carbon dioxide makes the blood more acidic by forming carbonic acid which dissociates into hydrogen ions and bicarbonate ion therefore the equilibrium shifts to the right rather than left as it should when buffering other sources of hydrogen ions
64
Q

How control carbon dioxide levels

A

How do you control carbon dioxide levels
- Respiration rate
- Depth of respiration
For example
- Increase breathing causes increase in carbon dioxide loss decreases hydrogen ion concentration in the blood and increases pH
- Decrease in breathing causes decrease in carbon dioxide renteion which causes decrease in pH

65
Q

as bicarbonate excretion increases

A

pH decreases

66
Q

as bicarbonate excretion decreases

A

pH increases

67
Q

write down the anion gap equation

A

 Anion Gap = [K+] + [Na+] - [Cl-] + [HCO3-] (plasma concentrations)

68
Q

what are the normal values

A 
Normal values 
pH = 7.35-7.45
pCO2 = 4.7-6.0 kPa
pO2 = >11.0kPa 
HCO3- = 22-26mmol/L
Anion gap = 8-12 mmol/L
69
Q

explain the anion gap

A

Normally there is an equal amount of positive and negative ions in the blood stream,
When an anion gap is high there is too much loss of HCO3- in order to compensate for this there is elevated levels of anions such as lactate, betahydrobutyrate, acetoacetate, phosphate and sulphate, this keeps the body electroneutrality
But these anions are not part of the anion gap calculation therefore a high anion gap results

FunMed Physiology (10 decks)

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