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Potassium Disorders. Jerry Hladik, MD UNC-Chapel Hill. Case 1. A 62 year old male presents to the emergency room with a 2 day history of weakness. His recent history is significant for gouty arthritis for which he was taking over the counter ibuprofen. 106 76 7.8 15 10. 100. - PowerPoint PPT Presentation

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  • Potassium DisordersJerry Hladik, MDUNC-Chapel Hill

  • Case 1A 62 year old male presents to the emergency room with a 2 day history of weakness. His recent history is significant for gouty arthritis for which he was taking over the counter ibuprofen. 106 76 7.8 15 10 100140 104 10 4 24 1100Normal Values

  • Case 2A 56 year old female presents with a 2 day history of weakness. On physical exam she is diffusely weak and is unable to sit up. The blood pressure is 210/105 mmHg. There is no edema. 96 20 1.9 32 1.4100140 104 10 4 24 1100Normal values

  • OutlinePotassium distribution in the ECF and ICF and factors that alter K distribution.

    Renal tubular potassium regulation and excretion

    Differential diagnosis of hyperkalemia and hypokalemia

  • Physiologic Effects of PotassiumMajor determinant of the resting membrane potentialHypokalemiamay precipitate cardiac arrhythmiasHyperkalemia life threatening cardiac conduction disturbances and arrhythmias

  • 3Na+2K+ATPaseTranscellular K+ DistributionK+cell = 140-160 mEq/LK+e = 4-5 mEq/L

  • Relationship Between [K+]serum and Total Body Potassium in 70 kg Adult Serum[K+]mEq/LTotal Body PotassiumNormal-150 mEq+150 mEq23456

  • Potassium DistributionECFICF3920 mEq80 mEq98%2%

  • Potassium Content in Fruits and Vegetables Amount of PotassiumMilligramsmEqPotato with skin 844 mg203 Oz. Dried Fruit796 mg2010 Dried Prunes 626 mg161 Banana 451 mg11Tomato254 mg6.51 Kiwi252 mg 6.58 Oz. Glass of 250 mg6.5 Orange Juice 1Grapefruit 158 mg4

  • A 24 y.o male returns home to visit his mother. For breakfast she serves orange juice (of which he drinks 3 large glasses), and a bowel of fruit comprised of 2 bananas, 1 grapefruit, and 1 kiwi.

    What would happen to the serum potassium concentration if all of the ingested potassium remained in the extracellular space?

    Ingested Potassium = 52 mEqExtracellular Potassium = 80 + 52 = 132 mEqSerum K Concentration = 132 mEq/15 L = 8.8 mEq/L !

  • Components of Potassium HomeostasisIntakeECFICFDistributionExcretion90% Kidney10% ColonInsulinAldosterone

  • Renal Tubular Potassium HandlingFiltered load600-700 mEqper dayK+ Reabsorption60-70%K+ Reabsorption20-30%K+ SecretionUrinary Excretion90mEq/day

  • Urinary Potassium ExcretionNormal kidneys have the capacity to excrete 500-600 mEq per day (average K+ excretion 40-100 mEq/day).

    The key site of renal potassium excretion regulation occurs at the cortical collecting duct.

  • Cortical Collecting Duct - Principle CellsNa+K+3Na+2K+AldosteroneR-AldoCl-PeritubularcapillaryTubular lumenATPaseNa+

  • Cortical Collecting DuctATPaseATPaseATPaseTubular lumenPeritubularCapillaryPrinciple CellIntercalated CellK+H+OH- + CO2HCO3-TCl-H2OH+3Na+2K+Cl-K+Na+ATPase3Na+2K+R-AldoNH3NH3H+ +NH4+Na+Aldosterone

  • Mechanisms Leading to HyperkalemiaImpaired entry into cells

    Increased release from cells

    Decreased urinary excretion

  • Hyperkalemia Redistribution: ICFECF3Na+2K+ATPaseK+H+GlucoseInsulinDigoxin-blockersCell injury

  • Factors that Impair Urinary K+ ExcretionCollecting duct lumen relatively more electropositiveDecreased flow and sodium delivery to the CCDDecreased aldosterone production or activity

  • Effect of AmiloridePredict changes in the following:

    Relative lumen chargeRenal K+ excretionSerum potassiumRenal H+ excretionArterial pHAldosteroneTubular lumen

  • Hyperkalemia: Decreased Renal ExcretionVolume depletion decreased flow in CCDDecreased renin-AII-aldo productionNSAIDS reninACEI AIIHeparin aldosterone productionSpironolactone aldosterone activity Inhibition of CCD Na+ channelAmiloride, triamterene, trimethoprim, pentamidine

  • ECG Changes due to Hyperkalemia

  • ECG Changes of HyperkalemiaSerum K+ (mEq/L)ECG9 Sinoventricular V-fib

    8 Atrial standstill Intraventricular block

    7 Tall T wave. Depressed ST segment

    6 Tall T wave. Shortened QT interval

  • Effect of i.v. Ca2+ on Membrane Potentials in Hyperkalemia-90-60-300+30EmEtNormal K+eEtEmi.v. CalciumEmEt K+e

  • Treatment of HyperkalemiaTherapyMechanism of ActionCalciumStabilization of Membrane Potential

    InsulinIncreased K+ entry into CellsBeta-2 AgonistsBicarbonate(if pHa

  • Differential Diagnosis of HypokalemiaIncreased entry into cells

    Inadequate intake or GI losses

    Urinary losses

  • 3Na+2K+ATPaseK+Hypokalemia: Redistribution: ECFICFInsulin-2 agonistsAlkalosis

    Barium poisoningHypokalemic periodic paralysis

  • Factors that Enhance Urinary K+ ExcretionLumen of CCD more electronegative

    Enhanced flow and sodium delivery to the CCD

    Increased aldosterone

  • Thiazide DiureticsLoop diureticsNa+K+2Cl--BloodLumenLoop diureticsNa+Cl-Thiazide diureticsSites of Action of DiureticsLumenBlood(Defect = Bartters)(Defect = Gitelmans)

  • Interpretation of Urinary K+ in the Setting of Hypokalemia GI Losses or priorRenal K Loss orDiuretic TherapyCurrent DiureticUse

    24o Urine K < 20 mEq > 30 mEq

    FeK < 6 % > 10 %

  • Serum [HCO3-]UpHU[Cl-]353025207.05.54.0503010Generation PhaseLate Maintenance PhaseVolume DepletionMetabolic Alkalosis in VomitingEarly Maintenance Phase

  • Effect of Gastric Loss of HCl, Na+/H2O (Volume)Predict changes in the following:

    1. Relative lumen charge2. Renal K+ excretion3. Serum potassium4. Renal H+ excretion5. Arterial pHHCO3-

  • Na+ balance -200200Days24681012141618Urine [Na+]mEq/L101520ECF Vol(L)1821Mean arterialPressure 100 11090150AldosteroneAldosterone Escape

  • Urine Na+ and Cl- in the Differential Diagnosis of Metabolic Alkalosis and HypokalemiaUrine ElectrolytesNa+Cl-Condition (meq/L)VomitingAlkaline urine>15
  • Case 2A 56 year old female presents with a 2 day history of weakness. On physical exam she is diffusely weak and is unable to sit up. The blood pressure is 210/105 mmHg. There is no edema. 96 20 1.9 32 1.4100140 104 10 4 24 1100Normal values

  • Case 2 ContinuedUrine [Na+] = 75 mEq/LUrine [Cl-] = 100 mEq/LFeK = 20%

    What is the most likely diagnosis?

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