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Renal > SM 214 Hypernatremia > Flashcards

SM 214 Hypernatremia Flashcards

1
Q

How do changes in tonicity make people feel sick?

A

Changes in tonicity cause changes in cell shape, which lead to sickness

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2
Q

What is the surrogate marker of tonicity?

A

Serum Sodium = Effective mOsm/Total Body Water

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3
Q

What determines transmembrane water flow?

A

Effective osmols on either side of a membrane

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4
Q

What is it hard to measure tonicity?

A

Ineffective mOsms

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5
Q

What is hypernatremia often called?

A

Dehydration

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6
Q

Can you be dehydrated and volume deplete?

A

Yes

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7
Q

Where are the baroreceptors?

A

Carotid Bodies and the Aortic Arch

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8
Q

What are the portions of urine volume?

A

Isotonic with plasma and electrolyte free portions

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9
Q

What does the electrolyte free water clearance tell us?

A

How much water is lost through the kidneys (or isn’t lost)

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10
Q

What determines how much salt is reclaimed from the urine?

A

Signaling on the levels of salt in the bloodstream determine how much water to keep via the release of ADH (or, alternatively, not releasing ADH)

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11
Q

What makes up the medullary gradient?

A

Na, Cl, and Urea up to 1200 mOsm’s

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12
Q

How does urine osmolarity relate to urine volume?

A

Low urine volume suggests high urine osmolarity and vice versa

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13
Q

What triggers thirst?

A

A rise is plasma osmolarity detected by osmoreceptors in osmoreceptors

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14
Q

What do osmoreceptors detect to release ADH?

A

Plasma tonicity is detected by osmoreceptors, not osmolarity

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15
Q

What signals other than tonicity can cause ADH release?

A

Severe volume loss, pain, nausea

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16
Q

Which signal is ADH release more sensitive to, changes in tonicity or changes in volume?

A

ADH release is more sensitive to changes in tonicity early, but at severe volume depletion, ADH release is controlled by the volume depletion and continues to be released even if tonicity is normalized

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17
Q

What are the symptoms of hypertonic hypernatremia?

A

Seizures, Coma, Thirstiness

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18
Q

What determines the severity of symptoms with hypertonic hypernatremia?

A

The rate of change in increase in serum sodium osmolarity

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19
Q

How does hypertonicity effect the brain?

A

Immediately, water flows out of neurons and into the hypertonic ECF

It quickly begins accumulating electrolytes in neurons to restore volume

It slowly accumulates organic molecules, to raise tonicity and restore volume

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20
Q

What happens if too much water is added too quickly to a hypernatremic patient?

A

Cerebral edema

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21
Q

Which produces cellular dehydration, volume depletion or hypertonicity?

A

Hypertonicity

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22
Q

What is lost in volume depletion?

A

Water and NaCl

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23
Q

Does dehydration tend to produce volume depletion?

A

Typically, no, because a lot of water would need to be lost to cause hypertonicity and the resulting volume depletion is incompatible with life

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24
Q

How does volume depletion effect diuresis?

A

Volume depletion = lower GFR = less diuresis

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25
Q

What are the two ways to develop hypertonic hypernatremia?

A

You receive hypertonic salt or you suffer persistent water losses that are not replaced by intake

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26
Q

What causes persistent hypertonic hypernatremia?

A

Absent thirst or access to water

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27
Q

What populations tend to have hypertonic hypernatremia?

A

People in nursing homes with low access to water

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28
Q

What are the 3 types of hypertonic hyprnatremia?

A

Hypertonic Na gain, polyuric or non-polyuric

29
Q

What are examples of hypertonic Na gain?

A

Drinking sea water
Hypertonic feeding - TPN
Primary aldosteronism

30
Q

What is the effect of acute hypertonic Na gain?

A

Water is drawn from the ICF to the ECF, causing brain shrinkage and elevation of EABV

31
Q

What causes non-polyuric hypertonic hypernatremia?

A

Volume deplete patinets in:

Hypodipsia
Fever, sweating
Vomiting
Diarrhea

32
Q

What is primary hypodypsia?

A

People who genetically don’t want water

33
Q

Do fever and sweating produce hypertonic or hypotonic cells?

A

Fever and sweating produces hypotonic losses and causes a hypertonic state in the body

34
Q

What type of GI losses cause hypernatremia?

A

Vomiting or osmotic diarrhea, but not secretory diarrhe abecause it is isotonic

35
Q

How does failure to replace water drive up hypenatremia?

A

Volume is lost without volume replacement

36
Q

How are polyuric hyponatremia’s divided?

A

Polyuric hyponatremia is broadly classified as solute diuresis and pure water diuresis

37
Q

Does hyperkalemia cause diabets insipdus?

A

Yes

38
Q

How does nephrogenic diabetes insipidus indirectly cause hypercalcemia?

A

Damage to the kidneys prevents filtation of calcium

39
Q

What genetic mutations predispose nephrogenic diabets insipidus?

A

V2R (X-linked) and AQPD2

40
Q

How should Na intoxication with neurologic symptoms be treated?

A

Administer D5W, but don’t let serum Na fall too fast

41
Q

How is sodium serum corrected for a high serum glucose?

A

Serum Na + (Glucose - 100)/100*2; need to correct because hyperglycemia draws water into ECF and lowers Serum Na

42
Q

How should hypernatremia due to sweating or GI losses be treated?

A

Treat with 0.9% saline + potassium to replace the salt and potassium losses

43
Q

How should central Diabetes Insipidus be treated?

A

2mg Desmopressin every 12 hours until the polyuria resolves, then switch to intranasal desmopressin

44
Q

How is nephrogenic DI treated?

A

Combination of low Na/protein diet, thiazide diuretics, and NSAIDS

45
Q

How do you calculate the osmolarity of a solute?

A

Concentration of a solute * number of ions per solute

46
Q

What is a normal urine output?

A

There isn’t one; it’s just the amount needed to get rid of the solute generated by diet and metabolism

47
Q

What is the formula for urine volume?

A

Urine Volume = Solute Intake Conc / Average Urine Conc

48
Q

What is solute diuresis?

A

A diuresis that aims to excrete large amounts of solute, which drag some water along with it, to produce urine of high osmolarity

49
Q

What is water diuresis?

A

A diuresis that aims to excrete large amounts of water, with some solute in it that was not removed, to produce urine of low osmolarity

50
Q

How do solute diuresis compare to water diuresis?

A

Salt diuresis = get rid of solute but due to high flow rate, less time to remove water, so Uosm > Posm

51
Q

How do water diuresis compare to solute diuresis?

A

Water diuresis = get rid of excess water, but due to high flow rate, not enough time to remove all solute, but Uosm < Posm

52
Q

How does diabetes insipidus cause glycosuria and polyuria?

A

Glucose filtration exceeds PCT reabsorptive capacity
Glucose conc rises in the tubule, drawing water
Increased water decreases sodium conc in tubule
Less sodium is able to be taken up the NKKC in TALH
Interstial gradient is lost and dilute Glucose containing urine is produced

53
Q

Why is polyuria caused by diabetes insipidus?

A

Excess glucose in the urine draws out water causing more frequent urination

54
Q

How does diabetes insipidus disrupt the interstial medullary gradient?

A

More water in the urine to quench glucose lowers the effective sodium concentration, preventing the NKKC from reabsorbing sodium and setting up the corticomedullary gradient

55
Q

How does the loss of ADH in diabetes insipidus effect urine osmolarity?

A

Urine osmolarity decreases in a dose response to the withdrawal of ADH

56
Q

What organ secretes ADH?

A

The Posterior Pituitary

57
Q

How does Central Diabetes Insipidus respond to Desmopressin?

A

Uosm rises by more than 100%

58
Q

How does Nephrogenic Diabetes Insipidus respond to Desmopressin?

A

No increase in Uosm

59
Q

What can cause combined loss of water and solute that leads to hypernatremia?

A

Extra-renal conditions: gastroentiritis, vomiting, sweating

60
Q

What can cause renal loss of water that leads to hypernatremia?

A

Renal loss leading to hypernatremia includes: CKD, DM, and diuretics

61
Q

What can cause free water loss that leads to hypernatremia?

A

Central Diabetes Insipidus and increased Insensible Losses

62
Q

What causes Central Diabetes Insipidus?

A

Inadequate production of ADH

63
Q

Is Central Diabetes Insipidus acquired or genetic?

A

Both

64
Q

What causes Nephrogenic Diabetes Insipidus?

A

Tubular unresponsiveness to ADH

65
Q

Is Nephrogenic Diabetes Insipidus acquired or genetic?

A

Both

66
Q

What is a potential iatrogenic cause of Hypernatremia?

A

Hospitalization with hypertonic fluid infusions

67
Q

What responses does hypernatremia trigger?

A

Increased Sodium concentration raises plasma osmolality, triggering an increase in thirst and ADH release

68
Q

Describe the urine in Diabetes Insipidus?

A

Urine is dilute: Uosm < Posm

Normal urine volume

69
Q

How long should it take to correct hypernatremia?

A

48 hours to avoid cerebral edema and seizures

Renal (19 decks)

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