Renal: Potassium

Front 1

key role of potassium in the body

Back 1

regulates RMP

Front 2

potassium distribution is regulated by

Back 2

Na/K ATPase, which pumps Na out and K into cells

Front 3

intracellular potassium level

Back 3

140 (98% of total body potassium is intracellular)

Front 4

extracellular potassium level

Back 4

3.5-5

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Things that can cause hyperkalemia

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artifact, redistribution, decreased renal excretion

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artifact

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hemolysis, leukocytosis, thrombocytosis (500K+), increased tourniquet time

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Things that cause redistribution from ICF >> ECF

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AIDS: metabolic Acidosis, insulin defic/hyperglycemia, Drugs (digoxin, nonselective beta blockers), hyperkalemic periodic paralysis

Front 8

hyperglycemia and insulin

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K+ follows water moving out of cells in response to high ECF tonicity; insulin encourages cellular uptake of K

Front 9

digitalis and nonselective beta blokers

Back 9

block Na/K ATPase

Front 10

Potassium reabsorption in the nephrob

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600-700 mEq filtered daily and 60-70% reabsorbed in PCT, 20-30% in loop of henle

Front 11

Where excreted K+ comes from

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secreted from CD - usually 70mEq per day but can be up to 280.

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Things that increase CD secretion of K+

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increased flow of tubular fluid (osmotic diuresis) ; increased lumen negativity, aldosterone

Front 13

role of osmotic diuresis

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more water means K+ concentration in lumen is less, favoring secretion

Front 14

role of lumen negativity

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promotes efflux into lumen; if more Na is reabsorbed, the lumen is more neg and K+ secretion favored

Front 15

role of aldosterone

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induces expression of Na+ channels on apical surface of principle cells, leading to more uptake, making lumen more neg. Also induces expression of K+ channels on apical membrane of principle cells, promoting excretion

Front 16

Hyperkalemia

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serum K > 5

Front 17

risk factors for hyperkalemia

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eGFR <20; DM, HIV, CHF, older pts, meds

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signs/sx of hyperkalemia

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ascending muscle weakness, EKG changes, arrhythmia, paralysis

Front 19

what happens to K in diabetic ketoacidosis

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hyperkalemia b/c high glucose pulls water/K+ out of cells and insulin is low, so less cellular uptake

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Plan:

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assess EKG, consider redistribution if no major sx

Front 21

EKG changes

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As serum K rises, see peaked T wave w/ short QT, followed by long PR and QRS, decreased p wave amplitude, then see sinoventricular pattern. EMERGENCY

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Things that decrease renal excretion of K

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Renal failure, low flow (hypovolemia), distal RTA

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NSAIDS/Cox inhib, beta blockers, DM and HIV

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inhibit renin, so less K+ secretion

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ACE Inhib, ARB, heparin

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ACE inhib block Angio II, ARB and heparin lower aldo >> so less K+ secretion

Front 25

Amiloride

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Blocks ENAC >> tubule more positive, so less K+ secretion

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Spironolactone

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K-sparing diuretic; decrease aldo >> less k+ secretion

Front 27

Intake and hyperkalemia

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high intake could cause hyperkalemia in setting of kidney defect, like RAAS problem or low GFR

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Treating symptomatic hyperkalemia

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treat promptly and provide continuous cardiac monitoring. Must stabilize MP, enhance uptake, decrease total body K

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IV Ca chloride/Ca gluconate

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Stabilize membrane potential. give every 5 min until EKG returns to baseline (contraindicated in pt w. digitalis tox)

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IV insulin

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enhances cellular uptake; give w/ nebulized albuterol

Front 31

therapy to decrease total body K

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dialysis, sodium polystyrene

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treating mild dz

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dietary changes - restrict to 2500 mg/day (60mEQ) avoid contributing meds.

Front 33

hypokalemia

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serum K <3.5

Front 34

diff dx for low serum K

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redistribution, kidney/GI losses, decreased intake

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signs and sx of low serum K

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abnormal skeletal/cardiac muscle function, usually when level dips below 3. See arrhythmia, muscle cramps, ascending weakness, resp weakness, paralysis, glucose intolerance, impaired urinary concentration. See U waves on EKG.

Front 36

most common cause of low serum K

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diuretics

Front 37

things that can cause redistribution: ECF to ICF

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B2 agonists, epineph, insulin, systemic alkalosis, barium intox, hypokalemic periodic paralysis, treating DKA

Front 38

urine potassium-creatinine ratio

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(urine K+ x 100 ) / urine Cr

Front 39

treating hypokalemia - large deficit

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give IV potassium chloride, avoid glucose and bicarb.

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treating asx

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potassium citrate for those w/ concurrent met acidosis due to RTA

Front 41

loop diuretics

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block Na/K/2Cl reabsorption in loop of henle

Front 42

bartter's deficiency

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looks like a loop diuretic; see hypoK, hypoCl, high renin, high aldo, metabolic alkalosis

Front 43

thiazides

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block Na/Cl reabs in DCT

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Gitelman's

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presents like thiazide

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what these diuretics do

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impair Na uptake and induce hypovolemia >> increase Aldosterone (also transient increase in flow) leads to more K secretion

Front 46

24hr urine K <20; Urine K/Cr <13

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think diarrhea, prior diuretics, decreased intake, redistribution

Front 47

24hr urine K >30, urine K/Cr >20

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think diuretics