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Path - Chempath > Sodium and Fluid balance > Flashcards

Sodium and Fluid balance Flashcards

1
Q

What is normal range for Na?

A

135-145

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2
Q

What is hyponatraemia range?

A

Na <135

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3
Q

What is the pathogenesis of hyponatraemia?

A

The problem is not salt loss
It is EXCESS WATER compared go the salt
As such you must always treat for the excess water, not the salt

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4
Q

What hormone controls water balance in the kidneys?

A

ADH

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5
Q

What is the function of ADH

A

It promotes water retention by inserting Aquaporin 2 channels into the collecting duct cells

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6
Q

What are physiological triggers to ADH secretion?

A

high urine osmolality (salt)

low blood volume)

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7
Q

What is the first step in the management of hyponatraemic patients?

A

ASSESS VOLUME STATUS

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8
Q

What are clinical features of hypovolaemia?

A 
Tachycardia, postural hypotension 
Dry mucous membranes 
Reduced skin turgor 
Confusion, drowsiness
Reduced urine output 
Low urine Na
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9
Q

What must you be aware of as urine findings if the patient is on diuretics?

A

They will have HIGH Na regardless

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10
Q

What are clinical features of hypervolaemia?

A

Raised JVP
Bibasal crackles
Peripheral oedema

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11
Q

What are causes of hypovolaemic hyponatraemia?

A

Diarrhoea, vomiting
Diuretics
Salt losing nephropahthy

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12
Q

How does hypovolaemic hyponatraemia occur?

A

With D&V > excess water loss > low perfusion pressure
This is detected by baroceptors > increase ADH production > increased water reabsorption
So more water is reabsorbed, and there is more water compared to salt

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13
Q

What are causes of euvolaemic hyponatraemia?

A

Hypothyroidism
Adrenal insufficiency
SIADH

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14
Q

How does hypothyroidism cause hyponatraemia?

A

Reduced cardiac congtractility > reduced BP detected by baroceptosr > more ADH > more water

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15
Q

What are causes of hypervolaemic hyponatraemia?

A

Cirrhosis
Cardiac failure
Renal failure

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16
Q

Summarise urinary sodium in the three hyponatraemias

A

Hypo/hypervolaemic: LOW

euvolaemic: high

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17
Q

What is SIADH

A

Syndrome of inappropriate ADH

caused by inappropriately released ADH e.g. CNS pathology, lung pathology,drugs, tumours, surgery,

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18
Q

What is plasma and urine osmolality in SIADH?

A

Plasma osmolality: low

Urine osmolality: HIGH

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19
Q

How do you treat hypovolaemic hyponatraemia?

A

Volume replacement with 0.9% SODIUM CHLORIDE

20
Q

How do you treat euvolaemic hyponatraemia?

A

Fluid restrict + treat underlying cause

21
Q

How do you treat hypervolaemic hyponatraemia?

A

Fluid restrict + treat underlying cause

22
Q

What is clinical presentation of severe hyponatraemia’

A

Reduced GCS
Seizures
Seek expert help (to treat with 3% hypertonic saline)

23
Q

What must you be aware of when correcting hyponatraemia?

A

CENTRAL PONTINE MYELINOLYSIS

So do not correct serum sodium too rapidly

24
Q

what are symptoms of CENTRAL PONTINE MYELINOLYSIS

A 
quadriplegia 
dysarthria
dysphagia 
seizures
coma 
death
25
Q

What drugs do you use to treat SIADH, if fluid restriction is insufficient?

A

Demeclocycline

Tolvaptan

26
Q

What serum level defines hypernatraemia?

A

Serum Na >145

27
Q

What is hypernatraemia caused by?

A

Unreplaced water LOSS - should not happen as patient should feel thirsty and drink to compensate. So only occurs in elderly/fasting/can’t keep up with losses

  • GI losses (nausea, vomiting)
  • Sweat losses
  • Renal losses (osmotic diuresis, diabetes insipidus, Conn’s)
28
Q

How do you treat hypernatraemia?

A

5% DEXTROSE (fluid replacement)

Treat underlying cause

29
Q

How do you treat someone with hypovolaemic hypernatraemia?

A

0.9% saline (for hypovolaemia)

5% dextrose (for hypernatraemia)

30
Q

what is the difference between osmolaRity and osmolaLity

A 
Osmolarity = calculated from blood test using FORMULA
Osmolality = measurement of particles in solution, using MACHINE
31
Q

What is the formula for osmolarity??

A

2(Na + K) + urea + glucose

32
Q

what occurs in Gilbert’s syndrome?

A

Reduction in UDP glucuronyl transferase activity to 30%

33
Q

what occurs in Crigler Najjar syndrome?

A

Complete deficiency of UDP glucuronyl transferase

34
Q

What are causes of SIADH

A

CNS pathology (/meningitis, encephalitis, absecess)
Lung pathology (pneumonia, TB)
Drugs (SSRI, TCA; opiate, PPI, carbamazepine)
Tumour (non small cell lung cancer, breast cancxer)
Surgery

35
Q

What does Conn’s do

A

Tumour causing excess production of Aldosterone > excess salt retention and K+ excretion

also low renin levels (as it is suppressed by aldosterone)

36
Q

How do you test for conn’s

A

Aldosterone to renin ratio

37
Q

How do you test for diabetes insipidus

A

water deprivation test

+ add desmopressin

38
Q

what must you look at to check if it is TRUE hyponatraemia

A

serum OSMOLALITY

39
Q

What do high/normala/low serum osmolality indicate in the context of hyponatraemia?

A

High osmolality: glucose/mannitol infusion
Normal osmolality: spurious, drip arm sample, pseudohyponatraeemia
Low osmolality: true hyponatraemia

40
Q

what electrolyte imbalance can occur following TURP^

A

HYPONATREMIA

from irrigation absorbed through the damaged prostatte

41
Q

How do glucose/mannitol in blood cause hyponatraemia?

A

Glucose and mannitol are osmotically active
they can draw water from the cells into the plasma
this dilutes down the sodium

42
Q

what are causes of hypontraemia post surgery?

A

overhydration with hypotonic IIV fluids

Transient increase in ADH due to stress of surgeyr

43
Q

what are the different neurological impacts of HYPOnatraemia vs HYPERnatraemia rapid correction

A

HYPOnatraemia: cerebral pontine myelinolysis aka locked in syndrome

HYPERNATRAEMIA: cerebral oedema

44
Q

explain symptoms of diabetes insipidus

A

hypernatraemia (lethargy, thirst, irritaability, confusion, coma, fits)
polyuria, polydipsia

45
Q

what are causes of cranial diabetes insipidus

A

surgery, trauma, tumours

LACK OF ADH

46
Q

what are causes of nephrogeniuc diabetes insipidus

A

receptor defect (insensitivity to ADH)
thiazide diuretic
inherited channelopathies
lithium, demeclocyclinee, hypercalcaemia

47
Q

Explain T4 renal tubular acidosis

A

ALDOSTERONE DEFICIENCY/RESISTANCE

causes acidosis and hyperkalaemia

Path - Chempath (23 decks)

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