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Nephrology > Regulation and Disorders of Salt and Water - Gyamlani > Flashcards

Regulation and Disorders of Salt and Water - Gyamlani Flashcards

1
Q

What percent of weight is TBW?

A

60% males

50% females

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2
Q

As a core principle, what is water balance regulated by?

A

Plasma osmolality

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3
Q

As a core principle, what is Na balance regulated by?

A

Plasma volume

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4
Q

What is total body sodium proportional to?

A

TBW

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5
Q

What is an equation for plasma osmolarity?

A

2*Na + glucose / 18 + urea / 2.8

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6
Q

What is a normal plasma Na?

A

140 mEq / L

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7
Q

What is the effect of hypovolemia on EABV, ECFV, plasma volume, and CO?

A

EABV - decreased
ECFV - decreased
Plasma volume - decreased
CO - decreased

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8
Q

What is the effect of CHF on EABV, ECFV, plasma volume, and CO?

A

EABV - decreased
ECFV - increased
Plasma volume - increased
CO - decreased

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9
Q

What is the effect of cirrhosis on EABV, ECFV, plasma volume, and CO?

A

EABV - decreased
ECFV - increased
Plasma volume - increased
CO - increased

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10
Q

What are sensors of plasma osmolality?

A

Hypothalamic osmoreceptors?

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11
Q

What are effectors of plasma osmolality regulation?

A

ADH

Thirst

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12
Q

What is manipulated through osmoregulation?

A

Urine osmolality

Water intake

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13
Q

What are sensors of EABV?

A

Macula densa
Afferent arteriole
Atria
Carotid sinus

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14
Q

What are effectors of EABV regulation?

A 
RAS
Aldosterone
ANP
Norepinephrine
ADH
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15
Q

What is manipulated through volume regulation

A

Urine Na

Thirst

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16
Q

What stimulates RAS?

A

Decreased sodium
Decreased ECFV
Decreased arterial pressure

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17
Q

What stimulates aldosterone?

A

Increased AT II

Increased plasma potassium

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18
Q

What are the actions of AT II?

A

Vasoconstriction

Increased Na absorption in PT

19
Q

What are the actions of aldosterone?

A

Increased Na reabsorption in DT

Increased K secretion

20
Q

What are the actions of atrial natriuretic peptide (ANP)?

A

Increased Na excretion

Afferent arteriolar vasodilation

21
Q

What is the result of hypertonic stimulation of hypothalamic receptors?

A

Increased thirst

Increased AVP

22
Q

Where is the thirst center located?

A

Third ventricle

23
Q

What stimulates the thirst center?

A

Increased ECF osmolality
Volume depletion / Decreased EABV
Angiotensin II

24
Q

What stimulates vasopressin / AVP / ADH?

A 
Increased ECF osmolality
Volume depletion / Decreased EABV
Angiotensin II
Pain
Nausea / Vomiting
Medications
25
Q

Where is AVP formed and released?

A

Formed - Hypothalamus

Released - Posterior pituitary

26
Q

Is sodium or water typically pathologic in hyponatremia?

A

Mostly water imbalance

27
Q

What is the first thing you should do when working up a hyponatremic patient?

A

Assess volume status

28
Q

Describe the underlying mechanism of hypovolemic hyponatremia.

A

Sodium depletion with reduction in ECFV and secondary water retention due to non-osmotic stimulation of vasopressin.

29
Q

What are common mechanisms of sodium loss in hypovolemic hyponatremia?

A 
Renal (U Na > 20 mEq / L)
Parenchymal disease affecting tubular handling of sodium
Mineralocorticoid deficiency
Persistent solute diuresis (glucosuria)
Diuretic therapy

Extrarenal
Vomiting / Diarrhea
Burns
Hemorrhage

30
Q

What are signs of sodium depletion?

A

Orthostatic BP
Poor skin turgor
Disproportionate increase in BUN:creatinine (prerenal azotemia)
Reduced urine sodium excretion

31
Q

Describe the underlying mechanism of euvolemic hyponatremia.

A

Water retention due to altered regulation of vasopressin (SIADH)

32
Q

What causes SIADH?

A

Pulmonary / CNS disorders
Malignancy
Pain / nausea
Drug-induced water retention (anti-psychotics)

33
Q

What are the diagnostic criteria for SIADH?

A

Decreased serum osmolarity (100 mosm/kg)
Euvolemia
Elevated U Na

34
Q

Describe the underlying mechanism of hypervolemic hyponatremia.

A

Retention of both sodium and water (greater water)

35
Q

What are common causes of hypervolemic hyponatremia?

A

CHF
Hepatic cirrhosis
Nephrotic syndrome
Renal disease

36
Q

What are symptoms of hyponatremia?

A

Nausea / malaise
Headache, lethargy, obtundation
Seizures, coma
*Chronic - few symptoms

37
Q

What can be caused by correcting hyponatremia too quickly?

A

Cerebral Demyelination Syndrome

38
Q

How do you treat hypo-, eu-, and hyper- volemic hyponatremia?

A

Hypo - Isotonic saline
Eu - water restrict / 3% NS / Diuretic
Hyper - Na restrict / Diuretic

39
Q

What is the equation for water excess?

A

.6 ( Wt ) * ( 1 - SNa / 140 )

40
Q

What does U osm < 300 mOsm/kg signify in hypernatremia?

A

Dysfunction ADH

Diabetes insipidous

41
Q

What does U osm > 500 mOsm/kg signify in hypernatremia?

A

Extra-renal water loss
Sodium ingestion/infusion
Decreased osmotic diuresis

42
Q

What are the symptoms of hypernatremia?

A 
Lethargy
Weakness
Irritability
Seizure
Coma
Death
43
Q

How do you treat hypo-, eu-, and hyper- volemic hypernatremia?

A

Hypo - Isotonic saline until hypovolemia resolved
Eu - Replace water (and ADH if dysfunctional)
Hyper - Remove Na

Nephrology (18 decks)

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