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Integrated Care Phase 1 > Acid Base Balance > Flashcards

Acid Base Balance Flashcards

1
Q

What is the normal range for plasma pH?

A

7.35-7.45

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2
Q

What are the clinical effects off acidaemia?

A

Affects enzyme function

K+ movement out of cells -> hyperkalaemia

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3
Q

How does acidaemia affect enzyme function?

A

Denatures them

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4
Q

What major affect does hyperkalaemia have?

A

Increases cardiac excitability causing arrhythmias

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5
Q

When does acidaemia become severe?

A

Below 7.1

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6
Q

When does acidaemia become life threatening?

A

Below 7.0

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7
Q

What is the main effect of alkalaemia?

A

Causes Ca2+ to come out of solution, so free Ca2+ falls

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8
Q

What is the effect of alkalaemia induced hypocalcaemia?

A

Increased neuronal excitability causing parasthesia and tetany

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9
Q

What is the mortality rate if pH rises to 7.55?

A

40%

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10
Q

How does the body buffer pH?

A

With CO2 and HCO3-

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11
Q

What is normal arterial CO2?

A

5.3 kPa

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12
Q

What equilibrium is there between CO2 and bicarb in the blood?

A

CO2 + H2O H+ + HCO3-

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13
Q

What physiological process is CO2 determined by in the blood?

A

Respiration

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14
Q

Where are the chemoreceptors than internally control CO2 oncentration in the blood?

A

Centrally i.e. in the CNS

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15
Q

When CO2 is disturbed, what is usually responsible?

A

Respiratory disease

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16
Q

Which organ controls HCO3-?

A

The kidneys

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17
Q

When HCO3- is deranged, what is usually responsible?

A

Metabolic or renal disease

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18
Q

What is the equation for blood pH?

A

pH= pK + Log([HCO3-]/(pCO2*0.23))

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19
Q

Why is pCO2 multiplied by 0.23 in that equation?

A

Because 23% of blood co2 is dissolved and therefore available to react with the water to create H+

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20
Q

Is CO2 dissolved in plasma the main source of HCO3-?

A

No, it creates a tiny amount. It is made in RBCs and transported to plasma

21
Q

What is HCO3- largely present with in ECF?

A

Na+ (i.e. it is disociated sodium hydrogen carbonate)

22
Q

How is more HCO3- produced in RBCs?

A

H+ binds to Hb so the equilibrium of the co2/hco3- equation within the rbc shifts to produce more H+ and HCO3-, which is then exchanged for Cl- in the plasma

23
Q

Why is plasma pH alkaline?

A

The large concentration of HCO3- stops nearly all the CO2 reacting so very little H+ is produced (as eqm is pushed to the left)

24
Q

What is pK in the equation?

A

6.1 at body temperature (37 degrees)

25
Q

What Is the normal range for HCO3- in the blood?

A

22-26 mmol/L

26
Q

In the kidneys, where is most HCO3- saved?

A

PCT

27
Q

How is HCO3- saved in the PCT?

A

Na is exchanged for H+. In the lumen, H+ reacts with HCO3- -> CO2 and water which is reabsorbed. Converts back to HCO3- which is transported back to ECF with Na.

28
Q

Where else, apart from the PCT, is HCO3- reabsorbed?

A

DCT and collecting ducts

29
Q

How is HCO3- reabsorbed in the DCT/CDs?

A

H+ is actively excreted whilst bound to ammonia nd phosphate, so no CO2 is formed in the lumen. HCO3- in the cell is then transported out into the ECF in exchange for Cl-.

30
Q

Which AA is converted to ammonium in response to low pH?

A

Glutamine

31
Q

Which ion is H+ exchanged with?

A

K+

32
Q

What happens to K+ in acidosis?

A

Hyperkalaemia as more H+ is pumped out so more K+ is retained

33
Q

What happens to K+ in alkalosis?

A

Hypokalaemia as more H+ is retained so K+ excretion increases in distal nephron

34
Q

What pattern would we see on an ABG of a pt in respiratory acidosis?

A

High pCO2, Normal HCO3-, Low pH

35
Q

What pattern would we see on an ABG of a pt in respiratory alkalosis?

A

Low pCO2, Normal HCO3-, rasied pH

36
Q

What if we saw high co2, high hco3- and a normal pH?

A

Compensated respiratory acidosis

37
Q

How long does compensation take to happen?

A

Usually 2-3 days

38
Q

What is the anion gap?

A

Difference measured between cations and anions due to other anions that are not measured

39
Q

When is the anion gap present?

A

If HCO3- is replaced by other anions, like in metabloic acidosis lactic acid reacts with HCO3- to replace it.

40
Q

How is ventilation stimulated in acidosis?

A

Peripheral chemoreceptors detect pH drop

41
Q

How is metabolic acidosis compensated?

A

Increased respiration to blow off CO2

42
Q

Why cant we compensate metabolic alkalosis with respiration?

A

Can’t reduce breathing rate as need to maintain pO2.

43
Q

What conditions cause respiratory acidosis?

A

COPD, severe asthma, drug overdose, neuromuscular disease

44
Q

What is the difference in chronic conditions?

A

Respiratory acidosis may be compensated already, so pH is nearer to normal range.

45
Q

When do we see respiratory alkalosis?

A

Hyperventilation e.g. anxiety/panic attack

46
Q

What conditions cause metabolic acidosis with an anion gap?

A

DKA, lactic acidosis (exercsising to exhaustion, poor tissue perfusion), and uraemic acidosis in advanced renal failure

47
Q

What conditions cause metabolic acidosis without an anion gap?

A

Renal tubulr acidosis (rare), or severe/persistent diarrhoea

48
Q

In DKA what happens to K+ and why?

A

You would expect it to rise, being acidosis, but due to osmotic diuresis, there is a whole body depletion of K= as it is lost in urine

49
Q

What conditions cause metabolic alkalosis?

A

Severe prolonged vomiting, mechanical drainage of stomach, K+ depletion, mineralocrticoid excess, and certain diuretics such as loop and thiazides.

Integrated Care Phase 1 (8 decks)

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