Electrolytes

• Electrolytes

  Inorganic substances that dissociate into ions
• Functions of electrolytes

  • Control the osmosis water between the fluid compartments
  • Maintain acid-base balance
  • Production of action potentials
  • Cofactors for enzymes
  • Maintenance of electrical neutrality
• Cations

  • Sodium
  • Potassium
  • Calcium
  • Magnesium
• Anions

  • Chloride
  • Bicarbonate
  • Phosphate
• Sodium

  • Most abundant extracellular cation
  • Intracellular - Extracellular Ratio: 1:12
  • Fluid balance
  • For the normal distribution of water and osmotic pressure in the ECF compartment
• Osmolality


  Number of mol/kg
• Osmolarity


  Number of mol/L
• Sodium regulatory mechanism

  1. Anti Diuretic Hormone (ADH)

  2. Aldosterone

  3. Renin Angiotensin Aldosterone System (RAAS)

  4. Atrial Natriuretic Peptide (ANP)
• Conditions associated with sodium

  • Hyponatremia
  • Hypernatremia
• Reference ranges (sodium)

  • Serum: 135-145 mmol/L (135-145 mEq/L)
  • CSF: 136-150 mmol/L (136-150 mEq/L)
  • Urine: 40-220 mmol/day (40-220 mEq/day)
• Conversion of mmol/L to mEq/L

  (value in mmol/L × valence of that ion)
• Specimen considerations (sodium)

  • Serum or Plasma
  • Sodium heparin
  • Hemolyzed sample shouldn't be used
• Analytical techniques (sodium)

  • Ion Selective Electrode (ISE)
  • Flame Emission Spectroscopy (FES)
  • Spectrophotometry
  • Colorimetric
  • Atomic Absorption Spectroscopy (AAS) - Gold Standard
• Potassium Kalium

  • Most abundant intracellular cation
  • Important for nerve impulse transmission and action potential
  • Deficiency or excess may affect both cardiac skeletal muscle
  • Intracellular - Extracellular Ratio: 23:1
  • Present in the serum in minimal amount because it is present inside the cell
  • Most important electrolyte for cardiac motility
  • Levels are controlled by Aldosterone
• Conditions associated with potassium

  • Hypokalemia
  • Hyperkalemia
• Specimen considerations (potassium)

  • Diurnal variation may not be followed
  • Fasting is not required
  • Serum, plasma, and urine
  • Artifactual Hyperkalemia/Pseudohyperkalemia
• Very high potassium levels can stop the heartbeat
• Reference ranges (potassium)

  • Serum: 3.8-5.5 mmol/L
  • Urine: 25-125 mmol/day
• Analytical techniques (potassium)

  • Ion selective electrode (ISE)
  • Flame emission spectroscopy (FES)
  • Spectrophotometric techniques
  • Atomic absorption spectroscopy (AAS)
• Conditions associated with chloride (Cl-)

  • Hypochloridemia
  • Hyperchloridemia
• Reference ranges (chloride)

  • Serum: 98-106 mmol/L
  • Urine: 110-250 mmol/day
  • Sweat: 5-45 mmol/L
• Specimen considerations (chloride)

  • No hemolyzed sample
• Analytical techniques (chloride)

  • Mercurimetric titration
  • Mercuric Thiocyanate Methods
  • Coulometric - Amperometric titration
• Chloride (Cl-) analytical techniques

  • Ion selective electrode (ISE)
  • Flame emission spectroscopy (FES)
  • Spectrophotometric techniques
  • Atomic absorption spectroscopy (AAS)
• Conditions associated with chloride (Cl-)

  • Hypochloridemia
  • Hyperchloridemia
• Hypochloridemia

  • Metabolic alkalosis
  • Respiratory acidosis
• Hyperchloridemia

  • Metabolic acidosis
  • Respiratory alkalosis
• Chloride (Cl-) reference ranges

  • Serum: 98-106 mmol/L
  • Urine: 110-250 mmol/day
  • Sweat: 5-45 mmol/L
• Specimen consideration for chloride (Cl-)

  No hemolyzed sample (may cause Pseudohyperchlorodemia)
• Analytical techniques for chloride (Cl-)

  • Mercurimetric titration (Schales and Schales)
  • Mercuric Thiocyanate Methods (Whitehorn titration technique, Skegg's modification)
  • Coulometric – Amperometric titration (Cotlove Chloridometer)
  • Ion selective electrode (Silver chloride electrode)
• Sweat has sodium and chloride electrolytes, but chloride only is the only one measured using sweat
• Sweat chloride determination

  It detects Cystic Fibrosis (also known as Mucoviscoidosis, viscous secretions affect internal organs, very well concentrated electrolytes increase Na, Cl)
• Importance of sweat chloride determination: it detects that in patients with cystic fibrosis, the chloride level present is equal or greater than 60 mmol/L
• Reference values for sweat chloride

  • Normal: 5-45 mmol/L
  • Gray zone: 46-59 mmol/L
  • Cystic fibrosis: Equal or greater 60 mmol/L
• How sweat specimen is collected

  Gibson and Cooke: Pilocarpine iontophoresis technique (Pilocarpine nitrate is a diaphoretic and sialogogic substance, specimen is collected using gauze pads, Cotlove technique is used after collection)
• Calcium

  5th most abundant mineral in the body, 98% is in the skeleton in the form of hydroxyapatite crystals, the remaining 2% is distributed 1% intracellular and 1% extracellular, around 1% is exchangeable in the plasma
• Functions of calcium

  • Blood coagulation (as a Clotting Factor)
  • Neuromuscular conduction
  • Cardiac and skeletal muscle excitability
• Regulatory mechanisms for calcium

  • Parathyroid Hormone (PTH)
  • Vitamin D
  • Calcitonin
• Forms of calcium in the blood

  • Free or Ionized (50%)
  • Protein-Bound (40%)
  • Complexed with Anions (10%)
• Ionization of calcium in the blood is pH dependent (if environment becomes more acidic, ionized calcium is higher; if environment becomes more basic/alkaline, ionized calcium is lower)