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GERR Physiology > Pathophysiology of Acid Base > Flashcards

Pathophysiology of Acid Base Flashcards

1
Q

What’s the biggest source of acid in the body

A

1- carbonic acid produced from cell respiration that is excreted from lungs as gas
2- non-carbonic involatile acid form cell metabolism that is excreted by kidneys

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2
Q

What is the PH calculation

A

PH= 6.1 + log { HCO3- / (0.224xPCO2 ) }

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3
Q

What can cause an acidosis ( think chemicals )

A

Increase in PCO2 ( respiratory) or decrease in bicarbonate ( metabolic )

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4
Q

What results in increase or decrease of PCO2

A

Increase : respiratory acidosis

decrease: respiratory alkalosis

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5
Q

Why would you see some increase in bicarbonate during acute respiratory acidosis

A

Other buffers ( ex: haemoglobin ) buffering Hydrogen ions but there isn’t much of an increase

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6
Q

How is respiratory acidosis compensated

A

With time kidneys compensates for lungs inability to expel CO2 by :
1- Excreting more hydrogen ions
2- Retain bicarbonate ions to act as an alkali to neutralize acidosis

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7
Q

How long does it take till renal compensation develops

A

A few days - week

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8
Q

What if there is an increase of H+ concentration but the PCO2 did not change , explain what that means

A

That indicates that there is something wrong with the respiratory system, and it hasn’t compensated for the metabolic acidosis , meaning this is a mixed respiratory and metabolic acidosis

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9
Q

What happens when there is an increase or decrease in PH

A

increase: alkalosis
decrease: acidosis

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10
Q

What type of acidosis is it if PaCO2 increases , what if HCO3 decreases ?

A

PaCO2: respiratory

HCO3 “ metabolic

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11
Q

How to differentiate between acute or chronic respiratory acidosis

A

Acute : less or no change in bicarbonate

Chronic : increase in bicarbonate

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12
Q

What happens if there is metabolic acidosis and bicarbonate decreases

A

There is a decrease in PaCO2

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13
Q

What is the anion gap

A

Shows if metabolic acidosis is due to carbonic acid only or other acid as well. Gap is anions that haven’t been measured, shows if it is high or normal .

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14
Q

What happens if there is respiratory alkalosis , what about metabolic alkalosis

A

Respiratory : Decrease in PaCO2

Metabolic : Increase in HCO3

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15
Q

How to differentiate between acute or chronic respiratory alkalosis

A

acute : same or increase in HCO3

chronic : decrease in HCO3

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16
Q

What follow metabolic acidosis increase in HCO3

A

Increase in PaCO2

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17
Q

Does acute asthma cause respiratory alkalosis or acidosis and explain how

A

Acute asthma causes irregular bronchoconstriction that causes a mismatch in ventilation and perfusion. This causes hypoxia and hypocapnia which results in respiratory alkalosis .

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18
Q

Does deteriorating asthma cause respiratory alkalosis or acidosis and explain how

A

Deterioration causes fatigue that respiration muscles are unable to keep up and results in hypoventilation. Hypoventilation increases PaCO2 , causes hypoxia and acute respiratory acidosis

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19
Q

What is the treatment of acute asthma , what is it for deteriorating asthma

A

Acute: bronchodilators

Deteriorating : assisted ventilation

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20
Q

How Hyperventilation leads to Respiratory alkalosis

A

1- Anxiety increases ventilation which causes hypocapnia and increases respiratory exchange ratio. Can cause tetany. This all leads to acute respiratory alkalosis
2- if chronic there will be renal compensation and it will be chronic respiratory alkalosis

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21
Q

What is tetany

A

Reduced free ionized calcium in body fluids by increased binding of calcium onto plasma proteins due to the being less occupied by hydrogen ions.

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22
Q

How to treat hyperventilation

A

Reassure and explain , treat cause or underlying disease

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23
Q

How COPD can result in Respiratory alkalosis or acidosis and is it acute or chronic ( Hint: 2 ways )

A

1- ventilation is impaired and there is a ventilation perfusion mismatch . Causes Hypoxia and hypercapnia. Result: chronic respiratory acidosis
2- If there is exacerbations then it will result in further hypoventilation , more hypercapnia and thus an acute on chronic respiratory acidosis

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24
Q

What complications can come from COPD treatment

A

Assisted ventilation can result in too high FIO2 which will result in hypercapnia.

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25
Q

What happens if through assisted ventilation you lower CO2 while renal compensation of rise in bicarbonate still exists

A

Can result inputs hypercapnic metabolic alkalosis

26
Q

How Chronic Kidney disease can result in acidosis or alkalosis ( 2 ways )

A

1- Failure to excrete non-carbonic acids and failure to reabsorb bicarbonate will result in low bicarbonate levels but high anion gap. Result: high anion gap metabolic acidosis
2- failure to excrete potassium causes hyperkalaemia which result sin displacement of hydrogen ions from cells that results in metabolic acidosis

27
Q

How Renal tubular acidosis Type 1 causes metabolic acidosis

A

1- Failure to secrete hydrogen ions due to problem with distal tubular cells. Results in normal anion gap metabolic acidosis.
2- failure to secrete and excrete potassium ions will result in hyperkalaemia and further metabolic acidosis

28
Q

How Renal tubular acidosis Type 2 causes metabolic acidosis

A

Failure to reabsorb bicarbonate in proximal tubule results in normal anion gap metabolic acidosis

29
Q

How to treat renal tubular acidosis

A

Type 1 & 2 : bicarbonate

30
Q

What could happen when renal tubular acidosis is treated with bicarbonate

A

Increased potassium secretion resulting in hypokalaemia. Unusual situation where potassium levels are going down and hydrogen concentration is going up

31
Q

How Diarrhoea can cause acidosis or alkalosis

A

1- Loss of fluids means loss of bicarbonate so there will be a normal anion gap metabolic acidosis
2- if there is loss of potassium then there will be acidosis with hypokalaemia

32
Q

What can cause the unusual combination of acidosis and hypokalaemia

A

1- Diarrhoea
2- Renal tubular acidosis
3- diabetic keto acidosis

33
Q

How is diarrhoea acidosis treated

A

Fluids and electrolytes

34
Q

How Vomiting can lead to alkalosis or acidosis

A

1- loss of gastric acid = metabolic alkalosis
2- loss of potassium results in hypokalaemia and thus further alkalosis
2- loss of fluids results in hypovolaemia which leads to hyperaldosteronism and thus further metabolic alkalosis

35
Q

How does Aldosterone ( hyperaldosteronism ) cause metabolic alkalosis

A

Stimulates sodium bicarbonate pumps in DCT which assists hydrogen ion secretion and thus metabolic alkalosis usually to make up for hypovolaemia

36
Q

In the case of hypovolaemia causing metabolic alkalosis what can result in prolongation of alkalosis and how can it be treated

A

Aldosterone drives sodium bicarbonate reabsorption to try and increase blood volume results in Kidneys unable to excrete excess bicarbonate and thus alkalosis is prolonged.
Fluids need to be given

37
Q

What does hypoaldesteronism cause , acidosis or alkalosis

A

Metabolic acidosis since there is a decrease in hydrogen ion secretion

38
Q

How Diabetic Ketoacidosis leads to metabolic acidosis

A

Low cell glucose results in shift to fat metabolism which overwhelms the mitochondria. Leads to ketone bodies forming and thus a high anion gap metabolic acidosis

39
Q

How does Diabetic Ketoacidosis cause hypokalaemia

A

Ketoacidosis results in potassium coming out of cell which results in hyperkalaemia but once it is treated with insulin potassium could fall , needs to be monitored

40
Q

How does Hepatocellular dysfunction lead to Acidosis or alkalosis

A

1- Abnormal levels of toxins and hormones stimulate respiratory centre which can results in chronic respiratory alkalosis
2- Loss of ability to manufacture albumin ( an acid ) can result in hypoaalbuminaemia leads to metabolic alkalosis
3- abnormal amino acids and other acids can lead to metabolic acidosis

41
Q

How can Salicylate ingestion cause acidosis or alkalosis

A

1- Non-carbonic acid can result in high anion gap metabolic acidosis
2- Stimulate ventilation which leads to hyperventilation that leads to respiratory alkalosis
3- Can be a mix of 1 and 2

42
Q

How do you treat salicylate ingestion causing acidosis or alkalosis

A

Forced Alkaline diuresis that transforms salicylate into ionized form that will be excreted

43
Q

How can IV saline result in metabolic acidosis

A

Excess isotonic saline ( PH 7. ) dilutes bicarbonate which can result in hyperchloraemia that results in metabolic acidosis

44
Q

How can IV saline result in metabolic acidosis

A

Excess isotonic ( sodium chloride ) saline ( PH 7. ) dilutes bicarbonate which can result in hyperchloraemia that results in metabolic acidosis

45
Q

List diseases that can cause respiratory alkalosis ( Hint: 7 )

A

1- Hyperventilation
2- Hypoxia ( reduces PaCO2)
3- Asthma : ventilation perfusion mismatch
4- Pulmonary vascular disease: ventilation perfusion mismatch
5- Liver disease
6- Heart failure : reflex increase in ventilation due to venous congestion
7- Respiratory stimulants : aspirin

46
Q

List diseases that can cause respiratory acidosis ( Hint : 3 )

A

1- Hypoventilation
2- asthma
3- respiratory depressants ( morphine )

47
Q

List diseases that can cause metabolic alkalosis ( Hint : 8 )

A 
1- Gastric secretion lost : vomiting 
2- hyperaldosteronism 
3- Hypovolaemia 
4- hypercapnia 
5- Alkali ingestion : antacids, bicarbonate 
6- Diuretics : aldosterone response causes alkalosis 
7- Seat loss in cystic fibrosis 
8- Hypokalaemia
48
Q

List diseases that can cause metabolic acidosis ( Hint: 9 )

A 
Normal anion cap 
1- renal tubular acidosis 
2- chronic renal disease 
3- diarrhoea 
4- ingestion 
Increases anion gap 
1- chronic renal disease 
2- lactic acidosis 
3- ketoacidosis 
4- liver disease 
5- ingestion of acids : aspiring, methanol , ethylene glycol
49
Q

What happens in lactic acidosis

A

If oxygen supply to cells is diminished then pyruvate accumulates from glycolysis and can’t undergo Krebs due to lack of oxygen. Pyruvate converts to lactic acids which is a non-measured anion.
Happens in exercise and disease

50
Q

Normal arterial blood PH

A

7.4 ( 7.35-7.45)

51
Q

Normal Arterial blood PaCO2

A

5.3 ( 4.6-6.4)

52
Q

Normal arterial blood HCO3

A

24 ( 22-30)

53
Q

Normal Total CO2

A

26 ( 23-31 )

54
Q

Normal arterial blood base excess

A

0 ( -2 - +2)

55
Q

Normal venous blood PH

A

0.05 less than arterial ( 7.35)

56
Q

Normal venous PaCO2 and HCO3

A

1 above arterial blood PaCO2 and HCO3 ( 6.3 & 25 )

57
Q

What would a normal anion gap be

A

Less than 12mmol/L

58
Q

65 year old women with 5 day of progressive confusion.
PH: 7.43
PCO2: 3.7
Bicarbonate: 18

A

Chronic respiratory alkalosis

59
Q 
65 year old women with 5 day of progressive confusion.  Also has painful arthritis 
PH: 7.33
PaCO2 : 3.7 
Bicarbonate : 14 
Anion gap : 18
A

High anion gap metabolic acidosis probably due to aspirin for her arthritis

60
Q

65 woman being treated for UTI develops high fever , shivering and hypotension.

PH: 7.1 
PaCO2 : 5.3 
HCO3: 12 
Base excess: -16 
Albumin: 15 
Sodium : 140 
Potassium : 5 
Chloride : 115 
Anion gap : 13
A

High anion gap metabolic acidosis but PaCO2 is not showing any compensation so she has Mixed high anionic metabolic and respiratory acidosis

61
Q

31 man has severe breathlessness, can’t complete sentence , pulse 120 bpm. Widespread wheeze, oxygen saturation 92%. Gets salbutamol by nebulizer and oxygen

At presentation: 
PH: 7.45 
PCO2: 4.7 
HCO3: 24 
Base excess: + 1 
30 minutes later looks exhausted: 
PH: 7.35 
PCO2: 6 
HCO3: 24 
base excess: - 1.2
A

V/Q mismatch leads to hypoventilation which results in respiratory acidosis

62
Q

Patient on ventilator in ICU .

On admission: 
pH: 7.21
paCO2: 10.7 
HCO3: 31 
BE: +1
24 hours later : 
PH: 7.48 
PaCO2: 5.6 
HCO3: 30 
BE: + 6.6

What has happened

A

Increased ventilation resulting in post hypercapnic metabolic alkalosis

GERR Physiology (18 decks)

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