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Nephrology > potassium > Flashcards

potassium Flashcards

1
Q

potassium

A

-Most abundant intracellular cation
-Intracellular:Extracellular ~ 38:1
-Plasma concentration: 3.5-5mmol/L
-Intracellular concentraion: 150mmol/L

-Total body potassium: 3500-4500mmol
-Total Extracellular K+: 30-70 mmol

-Na+K+ATPase pump sets up membrane potentials and is key to neuromuscular function
-Increased by: higher intracellular Na
-Decreased by: Digoxin toxicity, CHF, CRF

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2
Q

basics of lab medicine involved with hyperkalemia

A

-sources of specimens:
-venous blood
-arterial blood
-urine

-“The result is only as good as the specimen provided”
-Location of the draw
-Avoid drawing from a limb with an IV
-If necessary, stop IV for 30 mins and draw venous blood distal to IV site
-Decrease risk of hemolysis!!
-Use as large bore needle as possible- Limitations
-Recognizing a suboptimal blood draw

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3
Q

potassium: GI

A

-10% of K excretion
-Average Western diet 40-120mmol/day
-90% of K+ consumed is absorbed
-GI loss of potassium(10%) increased in:
-renal failure -> up to 50-60%
-diarrhea with large volume
-oral intake -> GI absorp -> extra-renal adaption -> renal loss = K balance

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4
Q

potassium: muscle

A

-muscles hold a large amount of K
-rhabdomyolysis -> huge release of K
-crush injury trauma -> release K

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5
Q

potassium: renal excretion

A

-90% of K is excreted via kidney (10% colon)
-Assuming a typical 100mmol intake and normal renal function:
-Filtered K+ = GFR x [K+serum] = 100 x 4 = 400mmol
-Passive reabsorption in the proximal convoluted tubule and Loop of Henle = 90%
-Active secretion in distal convoluted tubule and the cortical collecting duct by Principal cells

-Secretion/reabsorption is increased or decreased based on potassium concentrations and aldosterone!

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6
Q

potassium balance: renal

A

-aldosterone - increase K secretion
-hyperkalemia - increase K secretion
-distal urinary flow - enhance K excretion
-hypokalemia - reabsorption K increased

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7
Q

hyperkalemia causes

A

-sample error- asymptomatic pt -> redraw
-potassium shift
-decreased excretion
-excessive K intake

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8
Q

hyperkalemia: etiology K shift

A

-Rhabdomyolysis- crush injury
-Hemolysis
-Burns
-Strenuous exercise
-Sepsis
-Hypertonicity-K follows the flow
-Insulin deficiency

-Metabolic acidosis-Will be covered in acid-base lecture

-Pharmaceuticals:
-Digoxin
-Beta-antagonists
-Succinylcholine
-arginine

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9
Q

effects of exercise on K

A

-easy walking pace- +0.4 plasma elevation
-moderate exercise- +0.7
-strenuous exercise- + 2.0
-with beta blocker- + up to 4
-exercise effect will decrease with training
-dont memorize numbers
-beta blocker increases K by blocking it from going back into the cell
-cardiac rehab is needed for pts with prior MI and taking a beta blocker

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10
Q

hyperkalemia: decreased excretion

A

-Renal failure
-Interstitial nephritis
-Sickle cell disease

-Hypoaldosteronism
-Type IV RTA
-Diabetic nephropathy
-Heparin
-End stage AIDS
-Adrenal insufficency

-Pharmaceuticals
-ACE inhibitors
-Trimethoprim
-NSAIDs
-Spironolactone
-Triamterene
-pentamadine

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11
Q

hyperkalemia: etiology excessive intake

A

-ingestion
-iatrogenic*- most dangerous tool you will have may often be ur pen
-accidently overprescribe K

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12
Q

hyperkalemia symptoms

A

-None
-Weakness
-Palpitations
-Constipation
-Normal exam
-Pulse Irregular rhythm
-Decreased/absent bowel sounds
-Muscle weakness

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13
Q

hyperkalemia dx and labs

A

-Hyperkalemia is made by getting the result from the lab = >5mmol/L

-Associated labs/tests:
-BUN/Creatinine
-Serum glucose
-EKG!!!!!
-Urine: Potassium and creatinine

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14
Q

hyperkalemia EKG

A

-peaked T waves

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15
Q

hyperkalemia fraction

A

-Fractional excretion of potassium(FEK)

	  urine K/serum K
----------------------------  x 100%
	urine cre/serum cre

-FEK < 10% = renal cause
-FEK > 10% = extrarenal cause

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16
Q

transtubular potassium gradient

A

-Trans-tubular potassium gradient

Urine potassium x serum osmolarity ----------------------------------------------------
Serum potassium x urine osmolarity

-Gradient < 6-8 indicates renal cause
-Gradient > 8 indicates extrarenal cause
-Caveat: Chronic renal failure can have > 8

17
Q

hyperkalemia tx

A

-Ultimately, finding the cause and correcting the cause or compensating for it is the long term goal!
-ex. hyperaldosteronism state -> no cure -> try to compensate

-However, QUICK correction of potassium abnormality is needed due to its importance in action potentiation (cardiac)
-If hyperkalemia is suspected, do not delay treatment to find the cause

18
Q

acute treatment hyperkalemia

A

-1st option- calcium gluconate- does not fix K at all…it stabilizes membranes and prevents cardiac affect -> immediate to 2 hours

-now that it is stable -> you want to move K out of blood so you can use:
-glucose and insulin- shift K into cell -> mins- 3-4 hours
-albuterol nebulized (beta 2 agonist)- shift K into cell -> mins-1-2 hours
-albuterol is going to increase HR -> give benzo with it to calm the pt

-now we want to get rid of K:
-diuretics (furosemide)- removal renal - lasts 6 hours
-kayexalate (sodium polystyrene sulfonate)- GI tract loss (via fluid loss) -> several hours

-if pt is in renal failure/acid base disorder/tx didnt work:
-hemodialysis- remove through artificial filtration -> as needed

19
Q

hyperkalemia chronic tx

A

-Dietary restriction
-Removal of iatrogenic causes
-Loop diuretics
-Treatment of the route cause
-Fludrocortisone in hyporeninemic hypoaldosteronism

20
Q

hypokalemia

A

-Renal potassium loss
-Potassium shift favoring intracellular
-Decreased potassium intake
-Typically coupled with another cause
-Extrarenal potassium loss
-Sample error

21
Q

hypokalemia- etiology renal potassium loss

A

-Inc. aldosterone effect*
-Hyperaldosteronism
-Renovascular HTN
-Cushing’s syndrome
-german Licorice
-Congenital anomaly
-11beta or 17alpha hydroxylase deficiency

-Inc. flow at distal nephron
-Diuretics(furosemide or thiazide diuretics)

-Hypomagnesemia

-Renal Tubular Acidosis
-Fanconi syndrome
-Interstitial nephritis
-Metabolic alkalosis

-Genetic Disorders (study this)
-Bartter’s syndrome
-Liddle’s syndrome

22
Q

hypokalemia- etiology K shift into cells

A

-Insulin excess (maybe during DKA tx)
-Postprandial
-Iatrogenic cause

-Alkalosis(Respiratory or Metabolic)
-Beta-adrenergic excesses
-Hypokalemic periodic paralysis

23
Q

hypokalemia- etiology extrarenal loss

A

-Vomiting and/or diarrhea
-Villous adenoma
-Zollinger-Ellison syndrome

24
Q

hypokalemia S&S

A

-Symptoms
-None
-Muscle cramps
-Fatigue
-Weakness
-Constipation

-Blood pressure
-Inc with aldosteronism
-Dec with Gitelmans
-Dec with diuretic abuse

-Irregular heart rates
-Paralysis
-Decreased bowel sounds

25
Q

hypokalemia dx and lab

A

-Diagnosis is made by obtaining a lab result finding of K <3.5 mmol/L

-Other tests to aid in dx and tx
-BUN/Creatinine
-Glucose
-Magnesium
-EKG
-ABG
-24 hour urine potassium

26
Q

hypokalemia ekg

A

-can cause cardiac arrest

27
Q

hypokalemia- urinalysis

A

-24 hour urine
-<30 mmol = extrarenal cause
->30 mmol = renal cause

-Using Transtubular potassium gradient
-<2 = nonrenal cause
->3 = renal cause

28
Q

bartter’s syndrome

A

-Hypokalemia
-Increased urine output
-Normal renal function
-Increased urine ions:
-Calcium
-Potassium
-Sodium
-Magnesium
-Chloride

29
Q

gitelmans syndrome

A

-Hypokalemia
-Normal urine output
-Normal renal function
-Increased urine ions:
-Potassium
-Sodium
-Magnesium
-Chloride

-Dec’d urine calcium

30
Q

hypokalemia tx

A

-If patient is stable, focus on treating the underlying cause
-Evaluate diet for intake
-Evaluate medications that waste K
-Potassium replacement

-if pt not improving and Mg is low! -> magnesium replacement !

31
Q

hypokalemia tx K replacement

A

-Candidate for potassium replacement
-Hypokalemia
-Patient unable or unwilling to eat low Na diet
-Patient with nausea, vomiting, diarrhea
-Patient unable to stop diuretic or laxative
-Patient with drug-related hypokalemia

32
Q

hypokalemia tx potassium replacement

A

-Regardless of deficit, 40-100mmol/day is typically effective
-Oral replacement is preferred if an option (avoids overshooting)
-If IV is only option (vomiting):
-Rate and site of IV is most important
-Potassium should be suspended in saline (if you give with dextrose…stimulates insulin…pushing K into cell)
-Cannot give faster than 40mmol/hr (faster causes arrest)
-20-40mmol/hr requires cardiac monitoring
-K is irritating to venous structures

33
Q

hypokalemia tx Mg replacement

A

-Consider magnesium deficiency in cases of hypokalemia refractive to treatment and:
-CHF
-Digoxin toxicity
-Chemo:Cisplatin
-Loop Diuretics

34
Q

hypokalemia tx follow up

A

-In emergency situations:
-Check the electrolytes every 1-2 hours or as conditions change

-In stable situations:
-Check 4-6 hours after treatment as conditions change
-Then check daily, or if conditions change

-In Outpatient setting:
-Often will check weekly until stable then monthly or quarterly depending on patient compliance

Nephrology (8 decks)

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