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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
What happens when your carbon dioxide rises?
You hydrogen ions rise and you get respiratory acidosis
26
What can happen if you get respiratory acidosis? What disease does this give you?
Kidneys sense this and start to get rid of hydrogen ions and re absorbing bicarbonate. This can give you compensated respiratory acidosis
27
What would happen if you have low levels of carbon dioxide?
H ions decrease and you get respiratory alkalosis
28
What happens if hydrogen ions rise in your blood?
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
What would happen if you have a bicarbonate excess?
Hydrogen falls but co2 high so you get metabolic alkalosis
30
What are causes of respiratory acidosis?
Co2 retention leading to high Hydrogen levels caused by malfunction of excretory mechanisms or control
31
Examples of diseases which cause respiratory acidosis?
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
What are the compensatory response of respiratory acidosis?
Kidney retaining more bicarbonate buffer Renal hydrogen ion excretion
33
Respiratory acidosis - what does this do to your body? Depends on cause (Hypoxi and hypercapnia)
Hypoxia - SOB, drowsy, cyanosis Hypercanpnia - neurological - anxiety, coma, headache, extensor planters, myoclonus Cardiovascular - systemic vasodilation
34
Respiratory acidosis - biochemistry
Increased CO2 High hydrogen ions Bicarbonate normal or rising
35
Chronic Respiratory acidosis - biochemistry? - no acidosis as kidneys have helped
High co2 high hydrogen Compensatory bicarbonate
36
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
High co2 High hydrogen ions High bicarbonate
37
Respiratory alkalosis - causes?
Increased excretion of carbon dioxide
38
Examples of causes of Respiratory alkalosis?
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
Respiratory alkalosis - what are the compensatory response?
Buffering from the kidneys - reduce renal hydrogen ion excretion, lower carbon dioxide leads to reduced renal bicarbonate generation and reduced urinary acidification.
40
Effect of Respiratory alkalosis?
Acute hypo apnea - cerebral vasoconstriction - lightheadedness, confusion, syncope, fits - fall in ionised calcium - preioral, peripheral, paraesthesia Cardiovascular - increased heart rate, chest tightness, angina
41
Respiratory alkalosis - biochemistry - Acute
Low carbon dioxide, low hydrogen ions, small decrease in bicarbonate
42
Respiratory alkalosis - biochemistry - chronic?
Renal compensation leads to only slightly low hydrogen ions, lower bicarbonate
43
Metabolic acidosis causes?
Increased hydrogen ions, decreased hydrogen ions excreted, decreased bicarbonate in blood
44
Metabolic acidosis examples of causes?
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
Metabolic acidosis - compensatory responses?
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
Metabolic acidosis - biochemistry
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
Metabolic acidosis - effects on body?
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
Metabolic Alkalosis - causes?
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
Metabolic Alkalosis - example causes?
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
Metabolic Alkalosis - compensatory mechanisms
Buffering - release hydrogen ions Hypo ventilation- usually incomplete to try and keep carbon dioxide in Renal bicarbonate excretion increased
51
Metabolic Alkalosis - effects on body?
Asymptomatic Potassium depletion
52
Metabolic Alkalosis - biochemistry
Low hydrogen ions, High bicarbonate Low carbon dioxide
53
How do you assess acid-base status?
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
Assessment of acid-base - what are some practical aspects of this?
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
How would you approach working out what the patients has once you have all the blood results? Questions to ask yourself
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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