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Chemical pathology > C2&3 > Flashcards

C2&3 Flashcards

(54 cards)

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1
Q

What are the sources of water intake?

A

food, drink, metabolic water

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2
Q

What are the sources of water output?

A

kidneys, skin, lungs, GIT (stool)

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3
Q

What is the normal body water content?

A

60% of total body weight, decreases with age

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4
Q

How is total body water calculated (TBW)?

A

60% x total body weight

- e.g. 70kg x 60% = 42L TBW

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5
Q

What are the 2 fluid compartments that water is distributed between?

A
  • Intracellular fluid compartment (ICF)

- Extracellular fluid compartment (ECF)

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6
Q

How is water distributed between the 2 fluid compartments?

A
  • ECF: 45% of TBW

- ICF: 55% of TBW

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7
Q

What is the role of sodium in the body?

A
  • It is the predominant cation in the ECF, and influences distribution and movement of water between the ECF and ICF
  • Determines osmolality, ECF volume, blood volume, and blood pressure
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8
Q

How is sodium maintained?

A

By the the Na-K-ATPase pump, which keeps K in the ICF and Na in the ECF

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9
Q

What is the main source of sodium intake?

A

salt (NaCl): 100-200 mmol/day

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10
Q

How is sodium absorbed?

A

Most absorbed via GIT, via active transport

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11
Q

How is sodium excreted?

A

90% in the urine, stool, sweat

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12
Q

What are the mechanisms of water homeostasis?

A
  • ADH
  • ANP
  • RAAS system
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13
Q

Explain what happens when the water content in the blood drops below normal? (in terms of ADH)

A
  • Salt is eaten/sweating
  • Water content of blood becomes too low
  • osmoreceptors detect this, and pituitary releases ADH
  • High volume of water is reabsorbed by kidney and small volume of concentrated urine is passed to bladder
  • So, high volume of water is passed to the blood and the water content becomes normal again
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14
Q

Explain what happens when the water content in the blood rises above normal? (in terms of ADH)

A
  • Too much water drunk
  • Water content of blood becomes too high
  • osmoreceptors detect this, and pituitary releases little ADH
  • Low volume of water is reabsorbed by kidney and large volume of dilute urine is passed to bladder
  • So, low volume of water is passed to the blood and the water content becomes normal again
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15
Q

What does RAAS stand for?

A

Renin-angiotensin-aldosteron

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16
Q

When is the RAAS system activated?

A

dehydration, NA+ deficiency or heamorrhage

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17
Q

What is the goal of the RAAS system?

A

To decrease blood volume and blood pressure

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18
Q

Explain the mechanism of the RAAS system

A
  • Juxtoglomerular cells of kidneys detect (dehydration, NA+ deficiency, haemorrhage)
  • Kidneys secrete renin
  • Angiotensin I become angiotensin II
  • Angiotensin II acts on adrenal cortex to secrete aldosterone
  • Aldosterone acts on kidneys: increased Na+ and water reabsorption, increases K+ excretion in urine
  • Leads to an increase in blood volume and blood pressure to normal levels
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19
Q

What does ANP stand for?

A

Atrial natriuretic peptide

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20
Q

How is the homeostasis of the ECF disturbed?

A

ECF volume increases (fluid/salt)

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21
Q

What happens when the ECF homeostasis is disturbed?

A

Blood volume increases and atrial distension

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22
Q

What triggers and increases ANP release?

Study These Flashcards
A

A disruption in the ECF homeostasis: blood volume increase and atrial distension

23
Q

What does and increased ANP release do?

Study These Flashcards
A
  • decreases aldosterone
  • decreases ADH
  • decreased thirst
  • leads to increased water and Na+ loss
24
Q

What are the basic water disorders?

Study These Flashcards
A
  • dehydration

- fluid overload

25
What causes dehydration?
- Water loss due to decreased intake or increased output | - Water and Na loss: extra-renal, renal
26
Name disorders or conditions that cause an increased water output
- Diabetes insipidus - Osmotic diuresis - Excess sweating
27
Name renal causes of water and Na loss
- Decreased aldosterone - Addison's disease - Diuretics
28
Name extra renal causes of water and Na loss
- bleeding - diarrhoea - vomiting - burns
29
What is Diabetes insipidus?
- A disease that causes decreased ADH secretion or ADH resistance - This decreased absorption of water at collecting ducts - Large volumes of dilute urine - hypotonic fluid loss
30
What is isotonic dehydration?
When water loss is equal to Na loss
31
What is hypertonic dehydration?
When water loss if greater than Na loss
32
What is hypotonic dehydration?
When isotonic fluid loss is replaced with pure water
33
What causes fluid overload?
- Water overload: increased water intake or decreased water output - Water and Na overload: iatrogenic or increased aldosterone - Na overload: increased intake, iatrogenic, develop hypernatraemia
34
What causes a decreased output of water?
- renal failure | - inappropriate ADH secretion (SIADH)
35
Name a condition that causes water and Na overload
Oedema
36
What is oedema a sign of?
cardiac failure, renal failure, liver cirrhosis
37
How can your intake of Na become too high?
When sea water is consumed in near drowning
38
What are iatrogenic causes of Na overload?
hypertonic saline IV
39
What does SIADH stand for?
Syndrome of inappropriate ADH secretion
40
What is SIADH?
- When ADH is secreted in the presence of a decreased serum osmolality and hypervolaemia - Water is reabsorbed in collecting ducts: small volume of concentrated urine - The retained water is shared by the ECF and ICF
41
What are causes of SIADH?
pulmonary disease, pneumonia, TB, intracranial head injury, meningitis, tumours secreting ADH ectopic production esp. in bronchial tumours, pain, trauma, and surgery
42
What condition can SIADH cause?
cerebral oedema, which leads to decreased consiousness
43
What is oedema?
- When fluid leaks from the vascular compartment to the interstitial compartment - This decreased IV volume causes increased aldosterone secretion which causes Na and water retention
44
What are the causes of oedema?
- decreased vascular oncotic pressure (low albumin) | - increased vascular hydrostatic pressure
45
What are the basic sodium disorders?
- Hypernatraemia - Hypenatraemia - Pseudohyponatraemia
46
What are the signs and symptoms of hypernatramia?
thirst, hypertension, pitting oedema, agitation, convulsions, dyspnoea, respiratory arrest
47
What are the causes of hypernatraemia?
Water loss, Na and water loss, Na overload
48
What are the consequences of hypernatraemia?
decreased ICF -> cells shrink -> brain haemorrhage
49
What are the signs and symptoms of hyponatraemia?
muscle weakness, lethargy, confusion, hypotension, tachycardia
50
What causes hyponatraemia?
water overload, water and Na overload, Na and water loss followed by water intake only, dilution due to glucose, pseudohyponatraemia
51
What are the consequences of hyponatraemia?
increased ICF -> cells swell -> brain oedema
52
What is pseudohyponatraemia?
- False low Na measurement due to presence of increased lipids or proteins in specimen - Normally serum consists of 93% aqueous phase and 7% solid phase - Seen if using Indirect ISE method of measurement - Direct ISE method not affected (so more effective) - Identified by high osmolal gap
53
What is the osmolal gap?
Difference between determined osmolality and calculated osmolality
54
Why is the osmolal gap important?
- When calculated and measured is not the same | - Osmolal gap will increase in presence of volatile substances in blood &alcohol or methanol poisoning

Chemical pathology (6 decks)

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