Electrolytes PDF

ELECTROLYTES Clinical Chemistry 2 - Laboratory  Major Compartments for Fluids Intracellular Fluid (ICF) Extracellular Fluid (ECF) Inside the cell Outside the cell Most of body fluid...

ELECTROLYTES Clinical Chemistry 2 - Laboratory  Major Compartments for Fluids Intracellular Fluid (ICF) Extracellular Fluid (ECF) Inside the cell Outside the cell Most of body fluid Intravascular fluid - within (63%) blood vessels (5%) Decreased in Interstitial fluid – between elderly cells and blood vessels (15%) Transcellular fluid – CSF, pericardial, synovial  ELECTROLYTES Ions capable of carrying an electric charge Fluid always contains equal numbers of cations and anions ○ Electroneutrality - Balance of charges Dissociation of solutes into charged particles (ions) depends on ○ chemical composition of the compound ○ Concentration of other charged particles in the medium Rodriguez (2018)  Electrolytes in Body Fluid Compartments Intracellular Fluid Extracellular Fluid Potassium Sodium Magnesium Chloride Phosphorus Bicarbonate  FUNCTIONS Volume and osmotic regulation (Na, Cl, K) Myocardial rhythm and contractility (K, Mg, Ca) Important cofactors in enzyme activation (Mg, Ca, Zn) Regulation of ATPase ion pumps (Mg) Neuromuscular excitability (K, Ca, Mg) Production and use of ATP from glucose (Mg, PO4) Maintenance of acid-base balance (HCO3-, K, Cl) Replication of DNA and the translation of mRNA Rodriguez (2018)  SODIUM “Natrium” Most abundant cation in the ECF (90%) Plasma concentration depends greatly on the intake and excretion of water Reference value: 135 – 145 mmol/L Threshold value: 160 mmol/L (hypernatremia) 120 mmol/L (hyponatremia) CSF sodium: 136 – 150 mmol/L  Determination of Sodium Specimen: ○ Serum, plasma ○ False ↓ with marked hemolysis Chemical Methods (outdated – large sample requirements and lack of precision) Flame Emission Spectrophotometry ○ Dilute sample with deionized water 1:100 or 1:200 ○ Std: Li and Cs (preferred) ○ measurement of excited ions [sodium (yellow)]  Determination of Sodium AAS (Atomic Absorption Spectrophotometry) ISE (Ion Selective Electrode) – routinely used ○ Glass ion-exchange membrane ○ Two types of ISE measurement based on sample preparation: Direct measurement –undiluted sample Indirect measurement – diluted sample Colorimetry (Albanese Lein Method)  POTASSIUM “Kalium” major intracellular cation Single most important analyte in terms of abnormality – life threatening Reference value: 3.5 – 5.2 mmol/L Threshold critical value: 6.5 mmol/L (hyperkalemia); 2.5 mmol/L (hypokalemia)  Determination of Potassium Specimen: ○ Serum, plasma (heparin) - preferred, 24-hour urine ○ False ↑ with marked hemolysis Flame Emission Spectrophotometry ○ Dilute sample with deionized water 1:100 or 1:200 ○ Std: Li and Cs (preferred) ○ measurement of excited ions [potassium (violet)]. Colorimetry (Lockhead and Purcell) AAS (Atomic Absorption Spectrophotometry) ISE (Ion Selective Electrode) – method of choice ○ Valinomycin membrane  CHLORIDE Major extracellular anion – chief counter ion of sodium in ECF Only anion that serves as an enzyme activator Sweat chloride – diagnostic for cystic fibrosis Reference value: 98 – 107 mmol/L  Determination of Chloride Specimen: ○ Serum, plasma (lithium heparin), 24-hour urine ○ False ↓ with marked hemolysis (dilution) Mercurimetric Titration (Schales and Schales) ○ S-Diphenylcarbazone – indicator ○ HgCl2 = end product (blue violet)  Determination of Chloride Specimen: ○ Serum, plasma (lithium heparin), 24-hour urine ○ False ↓ with marked hemolysis (dilution) Spectrophotometric Methods ○ Mercuric Thiocyanate (Whitehorn Titration Method) = reddish complex ○ Ferric Perchlorate = colored complex  Determination of Chloride ISE (Ion Selective Electrode) – most commonly used ○ Electrodes with AgCl membranes (ion exchange membrane – tri-n-octylpropylammonium chloride decanol) Coulometric Amperometric Titration – Cotlove Chloridometer  CALCIUM Most abundant ion in the body 3rd most abundant in the blood 99% (bone), 1% (blood) TOTAL CALCIUM Reference value: 8.6 – 10 mg/dL (adult) 8.8 – 10.8 mg/dL (child) IONIZED CALCIUM Reference value: 4.6 – 5.3 mg/dL (adult) 4.8 – 5.5 mg/dL (child)  Determination of Calcium Specimen: ○ Serum, plasma (dry lithium heparin) - preferred, 24-hour urine ○ False ↑ with marked hemolysis Flame Emission Spectrophotometry EDTA Titration Method (Bachra, Dawer, and Sobel) Ion Selective Electrode (Liquid-membrane) Atomic Absorption Spectrophotometry – reference method Colorimetric Method – Ortho-Cresolpthalein Complexon Dyes ○ Dye: Arzone III ○ Mg2+ inhibitor: 8-hydroxyquinoline (chelator)  Determination of Calcium Precipitation and Redox Titration ○ Clark Collip Precipitation – end product: Oxalic Acid (pink color) CaC2O4 + H2SO4 → oxalic acid (H2C2O4) H2C2O titrated with KMNO4 → pink color ○ Ferro and Ham (Precipitation with Chloranilic Acid) Ca+2 + Sodium chloranilate → Ca Chloranilate Ca Chloranilate + EDTA → Chloranilic acid  INORGANIC PHOSPHORUS Omnipresent in distribution 75% (bones), 15% (ECF) in the form of inorganic phosphate Inversely related to calcium and PTH Essential for the insulin-mediated entry of glucose Reference value: 2.7-4.5 mg/dL (adult) 4.5 – 5.5 mg/dL (child)  Determination of Inorganic Phosphorus Specimen: ○ Serum, plasma (lithium heparin) ○ False ↑ with hemolysis Ammonium phosphomolybdate complex (340 nm) ○ Fike-Subbarow Method Most commonly used method  MAGNESIUM Intracellular cation 2nd to potassium Forms: ○ Free Mg2+ (Ionized form) – 50% (Physiologically active) ○ Protein-bound Mg2+ - 30% ○ Complexed with ions – 15% Reference value: 1.2 – 2.1 mEq/L  Determination of Magnesium Specimen: ○ Serum, plasma (lithium heparin), 24-hour urine ○ False ↑ with hemolysis AAS (reference method) ISE Dye-Lake Method – Titan Yellow Dye (Clayton Yellow or Thiazole Yellow) Fluorometric Method  Determination of Magnesium Colorimetric Methods ○ Calmagite Method Mg2+ + Calmagite → Reddish-violet (532 nm) ○ Formazen Dye Method Mg2+ + Dye → Colored complex (660 nm) ○ Methylthymol Blue Method Mg2+ + Chromogen → Colored complex  BICARBONATE 2nd most abundant anion in ECF Buffers excess hydrogen by combining with acid Composed of undissociated NaHCO3, carbonate, and carbamate Reference value: 21-28 mEq/L (venous blood – plasma or serum)  Determination of Bicarbonate Specimen: ○ Serum, plasma (heparin), 24-hour urine ○ False ↓ if left uncapped (↓ 6 mmol/L per hour) ISE (Clark Electrode) Enzymatic Method ○ Phosphoenolpyruvate carboxylase and dehydrogenase THANK YOU!