Simple Acid/Base Disorders Flashcards

1
Q

Simple Acid/base disorder occur if

A

Renal or respiratory functions abnormal

Acid or base load overwhelm the body

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2
Q

What do respiratory disorder affect

A

The Partial pressure of CO2

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3
Q

What do renal disorder affect

A

Bicarbonate concentration

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4
Q

What is important to consider in acid/base disorders

A

dont just occur in isolation and in otherwise healthy individuals need a combination of factors

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5
Q

What occurs in respiratory acidosis

A

an acidosis resulting from reduced ventilation, casusing a retention of CO2

this increases CO2, causing the pH to decrease

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6
Q

What is the causes of respiratory acidosis

A

Acute
- drugs which depress the medullary respiratory centres such as barbiturates and opiates

  • Obstruction of major airway

Chronic
- Lung disease
{Bronchitis, emphysema, asthma}

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7
Q

What is the response to respiratory acidosis to protect the pH

A

Need to Increases HCO3 concentration:

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8
Q

How does HCO3 concentration increase ins response to respiratory acidosis

A

-Increased partial pressure of CO2 (due to retention of CO2) will increase H+ secretion and increase ability to reabsorbs HCO3

  • Acid conditions will stimulate renal glutaminase Increasing NH3+ production so increase the generation of new HCO3 increase reabsorption of
    new HCO3
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9
Q

How do you treat respiratory acidosis

A

Need to correct original disturbance, so only restoration of ventilation can remove primary disturbance

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10
Q

Why in bronchitis which is a case of chronic respiratory acidosis the blood gas values are never normalised but the pH is normal

A

as the underlying disease process prevents the correction of ventilation but because the kidney maintains high (HCO3) the pH is protected

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11
Q

When does problems arise for patients with lung disease

A

so problems arise when patients with lung disease develop renal dysfunction

as lung disease patients have chronic respiratory acidosis, but as long as kidney function is not impaired pH can be maintained at a level compatible with life

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12
Q

Why is there a smaller decrease in pH in chronic respiratory acidosis than in acute respiratory acidosis

A

This is due to the mechanism to raise (HCO3) and balance out the pH,

as renal compensations takes time due to renal glutaminase taking 4-5 days to reach maximum,

So acutely there is a big drop in pH as renal compensation hasn’t kicked in, but chronic there isn’t a great change in pH as is controlled by renal compensation

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13
Q

What is occurs in respiratory alkalosis

A

alkalosis of respiratory origin so must be due to fall in PCO2 and this can only occur through increased ventilation and CO2 blow off

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14
Q

What is the causes of respiratory alkalosis

A

Acute

  • Voluntary hyperventilation
  • Aspirin
  • First ascent to altitude

Chronic
- Long tem residue at altitude

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15
Q

How does altitude increased affect your PCO2

A

decrease Partial pressure of oxygen to <60mmHg(kPa) stimuates peripheral chemoreceptors to increase ventilation, increased ventilation causes fall in PCO2

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16
Q

What is the response to respiratory alkalosis to protect the pH

A

(HCO3) should decreases

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17
Q

How does HCO3 concentration decrease ins response to respiratory alkalosis

A

if decreased PCO2, less H+ is available for secretion

therefore less filtered load of HCO3- is reanbsorbed so HCO3 is lost in the urine

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18
Q

How do you treat respiratory alkalosis

A

Normalise ventilation to correct initial disturbance

19
Q

What occurs in metabolic acidosis

A

An acidosis of metabolic origin due to a decrease in HCO3 concentration

decrease in (HCO3) either due to increased buffering of H+ or direct loss of HCO3

20
Q

What is the causes of metabolic acidosis

A

Increased H+ production

  • ketoacidosis in a diabetic
  • Lactic acidosis

renal failure -Failure to excrete the normal dietary load of H+

Loss of HCO3-
- due to diarrhoea

21
Q

What is the response to metabolic acidosis to protect the pH

A

PCO2 must be decreased

22
Q

How does PCO2 decrease ins response to metabolic acidosis

A

Respiratory regulation, as the acids stimulates the ventilation so the PCO2 falls

23
Q

How is ventilation increased in respiratory compensation

A

Increase ventilation in depth rather than rate

24
Q

What is this type of hyperventilation in respiratory compensation called, what is it a sign of

A

kussmaul breathing

is an established clinical sign of renal failure of diabetic ketoacidosis

25
Q

What problems occur in renal compensation for metabolic acidosis

A

Respiratory compensation delays renal correction

as normally the kidney corrects the disturbance by restoring (HCO3) and getting rid of the H+ ions, but this is a problems as source of H+ ions is from the CO2

but the respiratory compensation has lowered CO2 to protect pH, so smaller fraction of H+ secreted into renal tubule

26
Q

How does renal compensation occur for metabolic acidosis

A

There is a decrease in HCO3 reabsorption Because of the decreased (HCO3)

So only a small fraction of H+ available for HCO3 reabsorption
meaning greater proportion of H+ is available for excretion in the form of tithable acid and NH4 causing an Increase new HCO3 generated

27
Q

What occurs in metabolic alkalosis

A

(HCO3) must have increase through metabolism

28
Q

What is the causes of metabolic alkalosis

A

Vomiting lots of gastric secretion (increase in H+ loss)

Aldosterone excess (Increase in renal H+ loss)

Excess liquorice ingestion (similar to aldosterone - increase renal H+ loss)

Excess administration of HCO3 (in patients with impaired renal function)

Massive blood transfusion (as contains to prevent coagulation, which is covered to HCO3)

29
Q

What is the response to metabolic alkalosis to protect the pH

A

PCO2 will increase

30
Q

what occurs in compensation of metabolic alkalosis

A

respiratory compensation increases PCO2 which drives H+ secretion to maintain pH,

It delays the renal compensation and further exacerbates metabolic alkalosis by adding yet more HCO3 to the plasma

The greatly filtrated load of HCO3 then exceed the level of H+ secretion to reabsorb it (in the presence of CO2) and excess HCO3 is lost in urine

31
Q

What does acute respiratory alkalosis result in, and how is this demonstrated

A

Respiratory alkalosis, decreases the (HCO3),

If (HCO3) is decreased enough can cause metabolic acidosis,

which is shown by increased depth and rate of ventilation

32
Q
What are the 
H+, 
pH, 
PCO2 
(HCO3) 

levels in respiratory acidosis

A

Increased H+
Decreased pH

Increased PCO2 =disturbance
Increased (HCO3) =compensation

33
Q
What are the 
H+, 
pH, 
PCO2 
(HCO3)  

Levels in respiratory alkalosis

A

Decreased H+
Increased pH

Decreased PCO2
= disturbance

Decreased (HCO3)
= compensation

34
Q
What are the 
H+, 
pH, 
PCO2 
(HCO3) 

levels in metabolic acidosi

A

Increased H+
Decreased pH

Decreased (HCO3)
= disturbance

Decreased PCO2
= compensation

35
Q
What are the 
H+, 
pH, 
PCO2 
(HCO3) 

levels in metabolic alkalosis

A

Decreased H+
Increased pH

Increased (HCO3)
= disturbance

Increased PCO2
= compensation

36
Q

How do you determine between cause and effect acid base disorders

A

Check against the pH

37
Q

What must you consider with regulating ECF volume ie bad case of vomiting and acid/base regulation

A

Loss of NaCl and H2O causes Hypovalemia, where the Loss of HCL causes metabolic alkalosis

Even though you lose acid and alkali you become alkalosis due to decreased ECF volume stimulating aldosterone
to exchange Na+ for H+ (as Cl reduced so H= only remaining ion for exchange)

Further causing metabolic alkalosis due to excretion of H+

38
Q

In the case of bad vomiting

What is more important regulation of ECF volume or the pH

A

restoration of volume takes precedence over correction of metabolic alkalosis,

so aim to restore volume and the alkalosis will correct itself

39
Q

What acid base disorder is it usually to measure the anion gap and why

A

Metabolic acidosis, as there is two pattens of metabolic acidosis in terms of anion gap

either no change from normal in metabolic acids ot the anion gap increases

40
Q

What metabolic acidosis has no change in anion gap

A

If the acidosis is due to example to a loss of bicarbonate from the gut, then the reduction of bicarbonate is compensated by an increase in chloride and so there is no change in anion gap

41
Q

What metabolic acidosis causes change in anion gap

A

In lactic or diabetic acidosis, the reduction in bicarbonate is made up by other anions such a lactate, acetoacetate, Beta-OH butyrate, and so the anion gap is increased

42
Q

What are clinical affects of acid/base disorder

A

High acidity will cause hyperkalaemia
(as H+ ions are buffered intracellular in exchange for K+ ions)

wasting of bones - as bone carbonate provides an additional store of buffer

43
Q

What is the treatment for hyperkalaemia

A

Calcium resonium (exchanges Ca2+ rather than K+)

CA gluconate - decreases excitability of heart, stabilises cardiac muscle cell membranes

Insulin (+ glucose if non diabetic) - stimulates uptake of K+

44
Q

What do you need to be careful in hyperkalaemia treatment

A

needs to be careful fro hypokalaemia, so careful monitoring or K+ is essential