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Biochemistry And Endocrinology > Blood Gases and Acid-Base Damage > Flashcards

Blood Gases and Acid-Base Damage Flashcards

1
Q

What are physiological roles of hydrogen?

A
  • Influence Mitochondria
  • Protein conformation and function
  • metabolism
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2
Q

Hydrogen ion concentration needs to be tightly regulated - how is this acheived?

A

-production - excretion
- bufferng

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3
Q

What does buffering do?

A

takes up hydrogenionswhenthere’stoo many and releases them when there’s to few.

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4
Q

when would you get carbon dioxide?

A

Tissue respiration, lung exretion

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5
Q

When is lactic acid produced?

A

glycolysis, oxidation or gluconeogenisis

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6
Q

when do you produce ketoacids?

A

ketogenesis, oxidation

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7
Q

what does urea synthesis give you?

A

ureagenesis, oxidation of amino acids

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8
Q

What does carbon dioxide give you when it is dissolved in water?

A

A week acid

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9
Q

what does bicarbonate bind with hydrogen to give?

A

carbonic acid

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10
Q

What does carbonic acid give when it dissociates?

A

carbon dioxide and water

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11
Q

what can hydrogen bind to whihc acs as a buffer forcing bicarbonate to be left out of the cell?

A

haemoglobin

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12
Q

what enters the cell when bicarbonate leaves?

A

chlorine

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13
Q

hydrogen ion homeostasis -what is the pathway of carbon deoxide entering the cell?

A

CO enters RBC and dissociates to give a hydrogen ion which then binds to haemoglobin and leaves bicarbonate to exit the cell and a cloride comes in.

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14
Q

what does hydrogen ion homeostasis help regulate and the haemoglobin do?

A

hydrogen ion concentration and haemoglobin releases oxygen.

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15
Q

what are some other buffering mechanisms?

A

Phosphate
Other proteins
Exchange of intracellular potassium for hydrigen meaning an intracellular shift of H ions ad extracellular shift of potassium.

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16
Q

Hydrogen excretion - this happens through the lungs - what leaves

A

Carbon dioxide is exhaled through the lungs

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17
Q

What limits the excretion of carbondioxide?

A

Lung function and your body having enough bicarbonate

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18
Q

What other way can H ions be excreted?

A

Kidneys in urine

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19
Q

What is the aim of kidneys in getting rid of hydrogen ions?

A

Get rid of as much hydrogen ions as possible but keep bicarbonate

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20
Q

At what speed do people get rid of hydrogen ions depending on how they do it?

A

Buffers - rapid
Lungs - fast
Kidneys - slow

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21
Q

Acid based disorders - what is the relationship of hydrogen ions and ph?

A

pH is the log of hydrogen ions

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22
Q

What is acidosis?

A

High hydrogen ions

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23
Q

What is alkalosis?

A

Low hydrogen ions

24
Q

What can cause either acidosis or alkalosis?

A

Respiratory and metabolic causes
Homeostatic mechanisms will try and compensate

25
Q

What happens when your carbon dioxide rises?

A

You hydrogen ions rise and you get respiratory acidosis

26
Q

What can happen if you get respiratory acidosis? What disease does this give you?

A

Kidneys sense this and start to get rid of hydrogen ions and re absorbing bicarbonate. This can give you compensated respiratory acidosis

27
Q

What would happen if you have low levels of carbon dioxide?

A

H ions decrease and you get respiratory alkalosis

28
Q

What happens if hydrogen ions rise in your blood?

A

You will get rid of carbon dioxide to try and stable these levels (therefore having low Co2 in the body) and develop metabolic acidosis

29
Q

What would happen if you have a bicarbonate excess?

A

Hydrogen falls but co2 high so you get metabolic alkalosis

30
Q

What are causes of respiratory acidosis?

A

Co2 retention leading to high Hydrogen levels caused by malfunction of excretory mechanisms or control

31
Q

Examples of diseases which cause respiratory acidosis?

A

CNS depression or disease/neurological disease - narcotics, stroke, spinal cord lesions, motor neurone disease

Defects in respiratory function:
- Mechanical - myasthenia, thoracic trauma, pneumothorax
- pulmonary disease - restrictive - extensive fibrosis,
- obstructive - chronic bronchitis, severe asthma
- impaired perfusion - massive pulmonary embolism.

32
Q

What are the compensatory response of respiratory acidosis?

A

Kidney retaining more bicarbonate buffer
Renal hydrogen ion excretion

33
Q

Respiratory acidosis - what does this do to your body? Depends on cause (Hypoxi and hypercapnia)

A

Hypoxia - SOB, drowsy, cyanosis
Hypercanpnia - neurological - anxiety, coma, headache, extensor planters, myoclonus
Cardiovascular - systemic vasodilation

34
Q

Respiratory acidosis - biochemistry

A

Increased CO2
High hydrogen ions
Bicarbonate normal or rising

35
Q

Chronic Respiratory acidosis - biochemistry? - no acidosis as kidneys have helped

A

High co2
high hydrogen
Compensatory bicarbonate

36
Q

Acute on chronic Respiratory acidosis - biochemistry? - happens when they no longer have acidosis because of kidney response but then they get Ill and so have it once more

A

High co2
High hydrogen ions
High bicarbonate

37
Q

Respiratory alkalosis - causes?

A

Increased excretion of carbon dioxide

38
Q

Examples of causes of Respiratory alkalosis?

A

Hyperventilation
Stimuli to the respitroh centre -
- Cortisol - pain, fever
- Local - trauma, tumours
- Drugs, toxins, - salicylate, liver failure
- Hypoxaemia - R to L shunts, pulm disease

39
Q

Respiratory alkalosis - what are the compensatory response?

A

Buffering from the kidneys - reduce renal hydrogen ion excretion, lower carbon dioxide leads to reduced renal bicarbonate generation and reduced urinary acidification.

40
Q

Effect of Respiratory alkalosis?

A

Acute hypo apnea
- cerebral vasoconstriction - lightheadedness, confusion, syncope, fits
- fall in ionised calcium - preioral, peripheral, paraesthesia
Cardiovascular
- increased heart rate, chest tightness, angina

41
Q

Respiratory alkalosis - biochemistry - Acute

A

Low carbon dioxide, low hydrogen ions, small decrease in bicarbonate

42
Q

Respiratory alkalosis - biochemistry - chronic?

A

Renal compensation leads to only slightly low hydrogen ions, lower bicarbonate

43
Q

Metabolic acidosis causes?

A

Increased hydrogen ions, decreased hydrogen ions excreted, decreased bicarbonate in blood

44
Q

Metabolic acidosis examples of causes?

A

Increased acid formation -
Ketoacidosis - diabetic
Lactic acidosis - hypoxia
Poisoning - salicylate, methanol
Reduced excretion
Renal failure
Renal tubular acidosis (type 1 and 4)
Loss of bicarbonate buffer
Gastrointestinal - diarrhoea, pancreatic fistula
Renal - renal tubular acidosis type 2

45
Q

Metabolic acidosis - compensatory responses?

A

If kidneys rants an issue then buffering but this leads to a further fall in bicarbonate

Hyperventilation
- hydrogen ions will stimulate chemoreceptors
- kissmaul - deep, sighing
- Lowers carbon dioxide which lowers hydrogen
- limit to how far carbon dioxide can fall
Increased renal hydrogen excretion
As long as renal is okay

46
Q

Metabolic acidosis - biochemistry

A

High Hydrogen ions
Low bicarbonate
Hyperventilation causes low carbon dioxide
High extracellular potassium
Other features depend on underlying cause
Anion gap
- measure positive ions (Na) and (K) and taking away negative ions (Cl) (HCO)
- gap due to proteins, some small anions
- in metabolic acidosis
Gap normal In bicarbonate loss
So raised in increased acid production

47
Q

Metabolic acidosis - effects on body?

A

Cardiovascular - negative inotropic effect (heart issues)
Oxygen delivery -
- right shift of oxyhaemoglobin facilitates O2 delivery
- reduced 2,3-DPG- left shift to the curve impairs delivery
Nervous system - impaired consciousness
Potassium homeostasis
- redistribution of hydrogen ions into cells and makes potassi7m come out of cells.
- plasma potassium rises whist intracellular potassium and total body potassium is
depleted
Bone - chronic acidosis - buffering by bone phosphate leads to decalcification.

48
Q

Metabolic Alkalosis - causes?

A

Excess loss of hydrogen ion, alkali administration

  • characterised by increased bicarbonate levels
    bicarbonate is filtered by the kidneys so for metabolic alkalosis to persist inappropriate renal re absorption of filtered bicarbonate must occur:
    - extracellular volume contraction
    - potassium deficiency
    - Mineralocorticoid excess
49
Q

Metabolic Alkalosis - example causes?

A

Saline responsive
- GI - vomiting, gastric drainage
- urinary - diuretics (esp in CCF), nephrotic syndrome
Saline unresponsive - associated with hypertension - primary hyperaldosteronism, Cushing
- not associated with hypertension - severe potassium depletion, bartters syndrome

50
Q

Metabolic Alkalosis - compensatory mechanisms

A

Buffering - release hydrogen ions
Hypo ventilation- usually incomplete to try and keep carbon dioxide in
Renal bicarbonate excretion increased

51
Q

Metabolic Alkalosis - effects on body?

A

Asymptomatic
Potassium depletion

52
Q

Metabolic Alkalosis - biochemistry

A

Low hydrogen ions,
High bicarbonate
Low carbon dioxide

53
Q

How do you assess acid-base status?

A

Ask history,
Examination (doesn’t give you much)
Near-patient tests - arterial blood gas analysis (blood from artery and put in a machine to measure carbon dioxide, hydrogen ions)

54
Q

Assessment of acid-base - what are some practical aspects of this?

A

delay/temperature
- pCO2, hydrogen ions, bicarbonate may drop after 10 mins at 22C but stable for 60 mins at 0c - so put on ice.
Bubbles/froth
- you could just measure oxygen levels in bubbles not blood

55
Q

How would you approach working out what the patients has once you have all the blood results? Questions to ask yourself

A

What is the pH or Hydrogen ions
What is the carbon dioxide
What is the bicarbonate
Is there any compensation
What is the anion gap

Biochemistry And Endocrinology (16 decks)

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