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Physiology 1 Flashcards

1
Q

Normal aortic pressures?

A

120/80 mmHg

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2
Q

Normal LV pressures?

A

121/0 mmHg

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3
Q

Normal LA pressures?

A

8-10 mmHg

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4
Q

Normal RV pressures?

A

25/0 mmHg

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5
Q

Normal RA pressures?

A

0-4 mmHg

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6
Q

Physiological hydrogen ion concentration? (ie. pH 7.4)

A

40 nM/L

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7
Q

Usual pH of gastric juices?

A

pH 1-3

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8
Q

Usual pH of Urine?

A

pH 5-6

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9
Q

Usual pH of arterial blood?

A

pH 7.38-7.42

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10
Q

Usual pH of venous blood?

A

pH 7.37

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11
Q

Usual pH of CSF?

A

pH 7.32

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12
Q

Usual pH of pancreatic fluid?

A

pH 7.8-8.0

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13
Q

Why is tight pH control important for physiological function?

A
  1. Needed for normal fuctioning of mitochondrial proton pump and thus oxidative phosphorylation and production of ATP
  2. Needed to maintain structural integrity and function of enzymes and proteins.
  3. Affects HbO2 dissociation curve.
  4. Affects ionic flux
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14
Q

H+ concentration at pH 7.0?

A

100 nM/L

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15
Q

Approx how many moles of CO2 is produced daily by metabolism?

A

13-15 mol

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16
Q

Approx how many moles of fixed acids is produced daily by muscle protein metabolism?

A

50-80 mmol

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17
Q

Which systems act as a defence against acidaemia?

A
  1. Buffers (rapid, seconds)
  2. Respiratory (fast, minutes)
  3. Renal (slower, hours)
  4. Hepatic (slower, hours)
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18
Q

pK of HCO3?

A

pK 6.1

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19
Q

pK of Hb? (histidine)

A

pK 7.8

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20
Q

pK of amino- and carboxyl- proteins?

A

pK 7.4

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21
Q

pK of PO4?

22
Q

What is the Henderson-Hasselbalch equation?

A

pH = pK + Log10 [A-] / [HA]

23
Q

What are the main physiological buffer systems?

A
  1. Bicarbonate
  2. Phosphate
  3. Proteins
  4. Carbonate
24
Q

Where is the main site of action of phosphate as a buffer?

A

Renal tubules

25
Q

Most significant contributor to intracellular buffering?

A

Hb (histidine residues)

75% of all intracellular buffering

26
Q

Location of CO2 chemoreceptors?

A

Medulla and carotid bodies

27
Q

Define control effectiveness

A

The ability (or efficiency) of a homeostatic mechanism to resist a change in the parameter it controls. eg. lungs have 50-75% control effectiveness and therefore will compensate 5-7.5 nmol of a 10 nmol change in [H+]

28
Q

Through which mechanisms do the kidneys affect acid base balance?

A
  1. H+ secretion
  2. HCO3- filtration
  3. HCO3- generation
29
Q

Where and how is H+ secreted in the kidneys?

A

Collecting tubules

Via primary and secondary active transport

30
Q

What are the three main urinary buffers?

A

Bicarb
Phosphate
Ammonia

31
Q

How does the liver contribute to acid-base balance?

A
  1. CO2 production
  2. Metabolism of organic acid anions
  3. Production of plasma proteins
  4. Metabolism of ammonium
  5. Ureagenesis
32
Q

Summarise ureagenesis

A

Amino acid metabolism -> HCO3- and NH4+

2NH4+ + 2HCO3- -> Urea + CO2 + 3H2O

33
Q

Chemical structure of urea?

34
Q

What are the products of anaerobic metabolism?

A

ATP
Lactate
Water

35
Q

What is the definition of hyperlactataemia?

A

> 2 mmol/L

36
Q

Definition of lactic acidosis?

A

> 5 mmol/L and pH <7.35

37
Q

What is the normal lactate:pyruvate ratio?

38
Q

What does a lactate:pyruvate ratio of >10:1 indicate?

A

Tissue hypoxia

39
Q

Anion gap calculation?

A

([Na] + [K]) - ([Cl] + [HCO3])

40
Q

Causes of high anion gap acidosis?

A

CATMUDPILES

C: CO, CN
A: Alcoholic/starvation ketoacidosis
T: Toluene
M: Methanol, Metformin
U: Uraemia
D: DKA
P: Pyroglutamic acidosis, paracetamol, phenformin, propylene glycol, paraldehyde
I: Isoniazid, Iron
L: Lactate
E: Ethylene glycol
S: Salicylates
41
Q

Causes of normal anion gap acidosis? (aka. Hyperchloraemic acidosis)

A

CRAG (chin-rubbing anion gap)

C: Chloride excess
R: Renal tubular acidosis
A: Addison’s, Acetazolamide, Ammonium
G: GI losses of bicarb

42
Q

Causes of low anion gap?

A

V rare. HP BLIP

H: Hypoalbuminaemia (most common)
P: Paraproteins

B: Bromide
L: Lithium
I: Iodine
P: Polymyxin B (antibiotic)

43
Q

What does standard bicarb measure?

A

Bicarb corrected to normal temp and CO2 level

44
Q

Define base excess

A

The amount of acid or base required to bring a sample of blood to pH 7.4 in presence of normal PaCO2 (5.33 kPa)

45
Q

Compare and contrast the alpha-stat and pH-stat approaches to pH management

A

Refer to management of the hypothermic patient

Alpha-stat postulates that due to the constant buffering effect of imidazole/histidine intracellularly at low temperatures, intracellular pH is maintained and therefore does not need to be corrected.

pH-stat approach suggests that the Rosenthal correction factor should be used to alter parameters, advocating respiratory acidosis to maintain a ‘normal’ pH.

No clear evidence exists for the advantage of one over the other.

46
Q

How does ureteric transplant cause acidosis?

A

Urinary chloride is exchanged for HCO3 in the colon, causing hyperchloraemic acidosis.

47
Q

Outline Stewart’s acid-base theory

A

Dependent variables produce effects (through water dissociation):
H+
pH
HCO3-

Independent variables act as controllers:
PCO2
Net strong ion charge (SID)
Total weak acid

48
Q

What is a normal strong ion difference?

A

40-42 mEq/L

49
Q

What are the ‘strong ions’?

A

Na, K, Ca, Mg, Cl, Lactate

50
Q

According to Stewart’s Theory, what happens with an increase in SID?

A

pH will increase (alkalosis)

Primary FRCA (34 decks)

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