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Renal > Hyponatremia > Flashcards

Hyponatremia Flashcards

1
Q

What is the main cause of feeling “sick” when there are acute changes in tonicity?

A

changes in cell shape and size

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2
Q

What are effective osmols?

A

solutes that are trapped on one side of the cell membrane, which cause movement in total H2O to compensate for changes in tonicity

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3
Q

Alcohol and urea are what kind of osmols?

A

ineffective - they cross the cell membrane

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4
Q

Is tonicity estimated or measured?

A

estimated

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5
Q

is osmolarity estimated or measured?

A

measured

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6
Q

How do you calculate estimated osmolarity?

A

(NaX2) + (glucose/18) + (urea/2.8)

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7
Q

What is a normal serum osmolarity?

A

285 mOsms/L

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8
Q

A decrease in total body water would cause hyper/hypotonicity and hyper/hyponatremia?

A

hypertonicity and hypernatremia

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9
Q

An increase in total body water would cause hyper/hypotonicity or hyper/hyponatremia?

A

hypotonicity and hyponatremia

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10
Q

Do osmoreceptors respond to plasma tonicity or osmolarity?

A

plasma tonicity = by degree of stretch of the cell membrane under changing tonicity

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11
Q

What signaling in the posterior pituitary causes ADH release?

A

osmoreceptors + tonicity, AngII, volume depletion, nausea, pain, sedation, and drugs

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12
Q

How is electrolyte free water clearance calculated?

A

solute excretion/urinemOsm * (1- UNA+ UK/SNA)

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13
Q

At low osmolalities, what is true of the relationship between solute excretion and the water excretion ceiling?

A

at low osmolalities, excretion is much lower compared to other osmolalities at the same water volume ??

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14
Q

With or without ADH, what is true of the relationship between urine concentration and solute excretion?

A

solute excretion increases as urine concentration drops, regardless

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15
Q

What are the 3 types of hyponatremia?

A

isotonic/artifactual hyponatremia
hypotonic hyponatremia
hypertonic hyponatremia

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16
Q

What type of hyponatremia would be caused by hypergammaglobulinemia, hypertriglyceridemia, or hyperchylomicronemia?

A

artifactual/isotonic hyponatremia

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17
Q

What causes hypertonic hyponatremia?

A

addition of new effective osmoles to the ECF, causing water to flow out into the ECF and dilute Na

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18
Q

When do symptoms of hypotonic hypernatremia begin?

A

when SNa drops below 125 mEq/L

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19
Q

What are the symptoms of hypotonic hyponatremia, in order of appearance?

A 
nausea
fatigue
headache
lethargy
somnolence
coma 
seizures
20
Q

What determines the number and severity of classic hypotonic hyponatremia symptoms, prior to the start of seizures?

A

rate of change in hypotonicity - if very quickly, seizures will appear without the other symptoms

21
Q

When is aggressive treatment for hypotonic hyponatremia started?

A

when SNa is below 118 mEq/L regardless of symptoms

22
Q

What is the immediate/rapid adaptation of the brain to hypotonic hyponatremia?

A

loss of sodium, potassium and chloride

23
Q

what is the slow adaptation of the brain to hypotonic hyponatremia?

A

loss of organic osmolytes

24
Q

HOw quickly should SNa increase when treating hypotonic hyponatremia?

A

< 8 mEq/L/day

25
Q

What happens if SNa increases too quickly when treating hypotonic hyponatremia?

A

osmotic demyelination

26
Q

What type of hypotonic hyponatremia would be caused by addisons diseases, vomiting/diarrhea, diuretic agents, osmotic diuresis, sweating, or 3rd spacing?

A

volume depletion, (increased H2o and decreased TB sodium relative to each other)

27
Q

What type of hypotonic hyponatremia would be caused by psychogenic polydipsia, potomania, thiazides, SIADH, or a reset osmostat?

A

euvolemic (increased water but normal TB Na)

28
Q

What type of hypotonic hyponatremia would be caused by cirrhosis, nephrosis, and renal/heart failure?

A

edema (increased water and sodium)

29
Q

What kind of euvolemic hyponatremia would be caused by low ACTH, T4, CNS issues, pulmonary issues, malignancy, ecstasy, drugs or post op complications?

A

SIADH

30
Q

What is the main cause in volume depleted or volume overloaded hypotonic hyponatremia?

A

oliguria due to reduced EABV and persistent aldosterone/ADH/ATII followed by excessive TB intake relative to effective osmoles

31
Q

What causes hyponatremia in psychogenic polydipsia?

A

water intake exceeds the mechanical limits of the kidney to excrete water, leading to dilution of Na

32
Q

What effect does alcohol have on ADH release? what can this cause?

A

inhibits it, causes increased urine volume beyond what can be excreted , especially in the setting of low solute intake

33
Q

When does thiazide induced hyponatremia occur?

A

usually 2 weeks after starting the drug

34
Q

What is a normal SNa in an individual with hyponatremia who is taking thiazide diuretics?

A

127-130 mEq

35
Q

If a patient has heart disease, liver disease, edema or orthostasis, can they be diagnosed with syndrome of inappropriate ADH secretion?

A

nope

36
Q

Define SIADH

A

Uosm is inappopriate for Posm (ie. too high ) due to excessive ADH release

37
Q

What is the urine Na in SIADH?

A

it can be any value - it will just reflect the dietary intake

38
Q

what is the BUN and uric acid level in SIADH?

A

usually low

39
Q

What is reset osmostat?

A

the set point for osmoreceptors is lower, looks like SIADH except that patients excrete water load

40
Q

When is reset osmostat commonly seen?

A

during pregnancy

41
Q

What is the safest approach for treating hypotonic hyponatremia?

A

water restriction

42
Q

if the spot Una + Uk/SNa is over 1, should you give water to a hyponatremic patient?

A

nope

43
Q

if the spot Una + Uk/SNa is 0.5 to 1, should you give water to a hyponatremic patient?

A

500 ml/day

44
Q

if the spot Una + Uk/SNa is less than 0.5, should you give water to a hyponatremic patient?

A

restrict to 1000 ml/day

45
Q

When can oral V2 receptor antagonists be used?

A

to raise tonicity in SIADH and CHF but NOT liver failure

46
Q

When should limited administration of 3% saline be given?

A

during acute intoxication with symptoms of cerebral edema - goal is NOT to get SNa to normal

47
Q

What should you avoid doing in treating SIADH?

A

giving normal saline UNLESS there are loop diuretics as well

Renal (28 decks)

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