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ABIM > Nephro-Fluids and Electro > Flashcards

Nephro-Fluids and Electro Flashcards

1
Q

What are the two main things that maintain plasma osmolality?

A

thirst and ADH

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2
Q

Hyponatremia

A

serum sodium <136

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3
Q

What are the first tests to order or things to consider when evaluating hyponatremia?

A

plasma and urine osmolality, urine sodium, and assessment of volume status

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4
Q

What is ADH doing in hyponatremia?

A

ADH independent (normal): tea and toast, beer pottomania, psychogenic polydipsia, renal failure

ADH Dependent: hypovolemic, hypervolemic, euvolemic

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5
Q

What causes pseudohyponatremia?

A

high lipids or high proteins

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6
Q

When you have hyponatremia, what do you measure first? How does this send you through the algorithm?

A

You measure urine osmolality first. A Uosm >100 suggests ADH is playing a role (so consider, hypo/euv/hypervolemic)

If urine osm is <100 then it is the teatoast/beerpoto/psychogenic polydipsia that you have to think about

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7
Q

Causes of hypovolemic hyponatremia with Una <20 and Una >20. What happens to ADH?

pg 11

A
  • ADH is stimulated, or elevated

Una <20: vomiting, diarrhea, burns
Una >20: diuretic therapy, renal salt wasting, adrenal insufficiency, cerebral salt wasting

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8
Q

Causes of euvolemic hyponatremia with Una <20 and Una >20

pg11

A

Una >40: exclude hypothyroidism, glucocorticoid deficiency, SIADH, define cause o fit

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9
Q

Causes of hypervolemic hyponatermia with Una <20 and Una >20

pg11

A

*Basically despite high total body water and total body sodium, they are elevated at the same time and kidney senses decreased arterial volume of sodium so ADH given

Una < 20: CHF, cirrhosis, nephrosis
Una >20: acute and chronic kidney failure

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10
Q

What is the most common causes of euvolemic hyponatremia?

A

SIADH

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11
Q

How fast should you correct hyponatremia? Why?

A

Brain cells adapt to chronic hypontonicity and so if you correct too fast then you can cause neuronal damage leading to osmotic demyelination

don’t correct more than 8 points in 24 hours

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12
Q

How should acute SYMPTOMATIC hyponatremia be treated?

A

hypertonic saline with no more than 8 point correction in 24 hours… remember this is only if it is symptomatic!!

Loops diuretics may also help increase free water excretion

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13
Q

How is CHRONIC hyponatremia treated?

A

Usually hypervolemic hyponatremia and usually involves correcting the underlying disorder (renal failure-dialysis, CHF, cirrhosis), sodium and free water restriction, and diuretic therapy

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14
Q

What is first line therapy for EUVOLEMIC hyponatremia (SIADH)

A

(1) treatment of underlying cause and free water restriction
(2) loop diuretics, oral salt supplementation, followed by oral demeclocycline
(3) vasopressin antagonists (tolvaptin, conivaptan)

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15
Q

What is hypernatremia

A

Serum sodium >146

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16
Q

Why do elderly ppl often get hypernatremia?

A

Decreased thirst and or diminished access to fluids

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17
Q

What are the causes of hypernatremia besides decreased thirst?

A

Insensible water losses: heat, fever, exercise, severe burns, mechanical ventilation, osmotic diarrhea, secretory diarrheas

Renal water loss: osmotic diuresis due to hyperglycemia, post obstructive diuresis, or drugs (contrast, mannitol), central or nephrogenic DI

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18
Q

What should you ask when evaluating hypernatremia?

A

thirst, polyuria, diarrhea? document fluid intake and output (strict Is and Os)

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19
Q

How should people with nephrogenic DI be treated?

A

if desmopressin sensitive–calculate free water deficit and correct over 24-48 hours

you can use 1/2 normal saline

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20
Q

How do you treat hypernatremia?

A

It’s either caused by sodium gain or water loss

For euvolemic and hypervolemic hypernatremia you use a loop diuretic and 5% dextrose

For hypovolemic hypernatremia, you correct the free water loss

21
Q

What is hypokalemia?

A

Serum potassium <3.5

22
Q

What can occur when potassium goes <2.5?

A

Rhabdo can occur and ascending paralysis with respiratory failure

23
Q

What are the top four reasons for hypokalemia?

pg 15

A

Pseudohypokalemia
Intracellular shift
Inadequate K intake (rare)
Excessive K loss

24
Q

What are the steps to working up hypokalemia?

pg 15

A
  1. serum K if low, then…
  2. spot urine K
  3. ->If urine K is <20 (low) then this is because of GI loss
    - —> if urine K is >20, then you need to work up the reason for renal loss of sodium
  4. Check blood pressure
  5. THis, then takes you through the potassium algorithm, based on whether you have high or low blood pressure
25
Q

low serum sodium, urine sodium >20, HIGH BP

pg 15

A

Check renin.

Low renin–> check aldosterone
High renin–> RAS, renin secreting tumor, malignant hypertension, scleroderma renal crisis

Low renin, low aldosterone-> apparent mineralocorticoid excess, Liddle syndrome, 11-B-HSD deficiency, congenital adrenal hyperplasia, Cushing syndrome, licorice

Low renin, high aldosterone-> primary hyperaldosteronism, glucocorticoid remediable hyperaldosteronism

26
Q

low serum sodium, urine sodium >20, LOW/NORMAL BP

pg 15

A

Check acid-base.

Metabolic acidosis–> RTA, toluene, diabetic ketoacidosis

Metabolic alkalosis–> check urine Cl

Low urine Cl (<20): vomiting, nonreabsorbable anion, NG suction
High urine Cl (>20): Diuretics, Bartter syndrome, Gitelman syndrome, amino glycoside toxicity, MG deficiency

27
Q

Medications that cause a transient shift of potassium from the extracellular compartment into cells

A 
Epinephrine
Decongestants
Bronchodilators
Theophylline
Caffeine
Insulin
Respiratory/metabolic alkalosis
28
Q

What is hypokalemic periodic paralysis?

A

It is a rare familial or acquired disorder characterized by flaccid generalized weakness from a sudden intracellular potassium shift caused by strenuous exercise or a high carb meal

29
Q

What does urine potassium loss >20 suggest?

A

suggests excessive urinary losses

30
Q

What does urine potassium <20 suggest?

A

It suggests cellular shift, decreased intake, or extra renal losses

31
Q

What are causes of pseudohypokalemia?

A

Lab drawing error

32
Q

What is hyperkalemia

A

Serum potassium >5

33
Q

What is the first thing you need to do when working up hyperkalemia?

A

You get an EKG

34
Q

What are the EKG changes of hyperkalemia?

A

Peaked T waves, as hyperkalemia progresses, there is prolongation of the PR interval, loss of P waves, and eventual widening of the QRS with a sine wave pattern that can precede asystole

35
Q

What are the causes of hyperkalemia?

A

Pseudohyperkalemia–AML
Extracellular shift
Increased K intake
Decreased K excretion (most common)

36
Q

Drugs that cause hyperkalemia?

A

digoxin toxicity, succinylcholine, beta blockers somatostatin

37
Q

Common causes of hyperkalemia from extracellular shift?

A 
metabolic acidosis
insulin deficiciency 
rhabdomyolysis
tumor lysis
hemolysis
hyperosmolarity
hyperkalemic periodic paralysis
38
Q

Causes of pseudohyperkalemia

A

Blood malignancies
having a tourniquet on for too long
venipuncture issues

39
Q

What are the three causes of hyperkalemia due to decreased potassium excretion?

A
  • Impaired aldosterone action
  • Decreased urine flow or sodium delivery to distal nephron (volume depletion, heart failure)
  • Kidney failure (AKI, CKD, ESRD)
40
Q

How does aldosterone resistance cause hyperkalemia?

A

Medications: amiloride, triamterene, spironolactone, eplerenone, pentamidine, trimethoprim

Tubulointerstitial disease

Gordon syndrome

Defective mineralocorticoid receptor

41
Q

How does aldosterone deficiency cause hyperkalemia?

A

medications: NSAIDS, COX-2 inhibitors, calcineurin inhibitors, ACEI/ARBS

Diabetes mellitus

HIV

Urinary tract obstruction

Aging

Heparin

Ketoconazole

Adrenal insufficiency

Congenital enzyme defects

42
Q

How do you manage severe hyperkalemia with EKG changes?

A

This requires immediate stabilization of the myocardial cell membrane, rapid shifting of potassium intracellularly, and total body potassium elimination.

  • -Give IV calcium for membrane stabilization (give multiple times if needed)
  • Insulin or high dose beta adrenergic agonists (albuterol)
  • sodium bicarb can be given in the setting of a metabolic acidosis UNLESS it is DKA
43
Q

What is the time of onset for these hyperkalemia drugs:

  • IV calcium
  • 10 units of insulin
  • beta agonists
A
  • IV calcium: 30-60 minutes
  • 10 units of insulin: 10-20 minutes (duration is 4-6h)
  • beta agonists: 3-5 minutes and lasts 1-4 hours
44
Q

How is potassium removed from the body?

A

Loop diuretics+saline infusion
sodium polystyrene sulfonate
hemodialysis

45
Q

Longterm treatment of hyperK, like with ESRD? What about with Endo disorders?

A

low K diet, correct underlying cause, diuretics.

If there is an endocrine cause, like hypoaldosteronism… then you need fludrocortisone too?

46
Q

How does hypophosphatemia occur? What patients have this?

A

<3

alcoholics, malnutrition, critical illness

47
Q

What is fanconi syndrome?

A

it is a hypophosphatemia with a type 2 (proximal) RTA with urine los of bicarb, phosphaturia, glucosuria, aminoaciduria

48
Q

Management of hypophos?

A

IV phos, monitor phos and calcium every 6h

49
Q

What is the most common causes of hyperphos? How is it managed chronically?

A

CKD and AKI.

Managed by dietary phosphate restriction and phosphate binders

ABIM (58 decks)

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