POTASSIUM

  • major intracellular cation in the body

    • 20x greater inside the cell than outside the cell

  • 2% of total body potassium circulation in the plasma

Collection of Specimen & handling

Platelets—not a cell, but a fragment from megakaryocytes

Platelets contain potassium

Psuedohyperkalimia - falsely increase in K+ level

  • always bantayan sa K+ and increase level instead of decrease

  • When clumping and coagulation occur, tend to release the potassium contained and increase the K+ levels in serum.

    • K+ maybe 0.1-0.5 mmol/L higher

      • K+ in serum is higher than in plasma

        • THROMBOCYTOSIS - high platelets count

  • Increase platelet count = increase K+

    • Heparin

  • situation where K+ shift occurs

    • prolong tourniquet application

    • fist benching

  • In vitro hemolysis

    • 3-30% increase in K+

  • Storage:

    • Whole Blood sample

      • Room temperature

METHODS

  • Colorimetric Methods

    • Lockhead and Purcell Method

      • Potassium (react)→ Sodium Cobatinirate = Sodium potassium cobaltinitrite

        • combination type of reaction

        • w/ addition of phenol (color developer) = blue

          • spectrophotometrically

  • Ion selective electrode (ISE)

    • Indicator electrode

      • come in contact with the specimen

        • have change always in potential

    • What does the indicator electrode measure?

      • activity of potassium

    • electrochemical techniques of sodium

      • Potentiometry

    • valinomycin

      • antibiotics

      • use or added so that ISE is selective for K+

PACKAGE INSERT

  • Na- Tetraphenylborate + K+ →k- Tetraphenylborate + Na+

    • Turbidimetric method

      • photometrically measured

  • 578 nm (570-620nm).

    • Wavelength

  • Potassium Standard concentration

    • 5 mmol/L

  • Reagent and standard is ready to use

  • sealed reagents are stable up to the expiry date

  • stored at 2-8c

  • protected from the light

  • Once opened stable up to 4 weeks

    • avoid contamination

  • turbidity or precipitation in any kit indicates deterioration

    • must be discarded

  • Volumes:

    • K+ reagent

      • 1000ul

    • Standard

      • 25ul

    • Sample

      • 25ul

  • incubation time

    • 5mins @ room temp.

  • Duration of test

    • 10mins @ 578 nmn

  • formula:

    • K+ conc. (mmol/L) = Ab sample / Ab Standard x5

    • mmol/L →N (meq/L)

      • multiply by 1

  • Reference range

    • 3.6 - 5.5 mmol/L

    • 3.6 - 5.5 N (meq/L)

  • Linearity

    • 14mmol/L

  • Dilution

    • Normal Saline Solution