Electrolytes

• Passive transport


  Does not require ATP for the movement of molecules
• Active transport


  Requires energy for the movement of molecules
• Difference between the cations and anions routinely measured in serum
• Cations and Anions are equal
• [Na + K] - [Cl + HCO3]

  Reference range: 10-17 mmol/L
• Inorganic substances


  Dissociate into ions
• Inorganic substances


  Tiny substances, atoms, elements that exist in the body fluids
• Abnormalities in their values can cause significant disease
• Sodium


  Most abundant extracellular cation
• Sodium


  Intracellular-Extracellular ratio: 1:12
• Sodium


  For the normal distribution of water and osmotic pressure in the ECF compartment
• Around 2/3 of the body fluid is inside the cells (ICF), and 1/3 is outside the cells (ECF)
• Sodium


  Considered as the "Principal Osmotic Particle in the Plasma"
• Normal plasma osmolality


  280-300 mOsm/kg
• In a normal plasma osmolality value, half of which is due to sodium
• Sodium


  Maintains normal osmotic pressure by maintaining plasma osmolality
• If osmolality is decreasing, water is loss
• Electrolytes


  Control the osmosis of water between the fluid compartments
• Electrolytes


  Maintain acid-base balance
• Electrolytes


  Cofactors for enzymes
• Potassium

  Production of action potentials
• Electrolytes


  Maintenance of Electrical Neutrality
• Where Sodium goes, Water follows
• Osmolality


  No. of osmoles of a solute in kg of solvent
• Osmolarity


  No. of osmoles of a solute in a liter of solvent
• Anti-diuretic hormone (ADH)


  It indirectly regulates water absorption
• Aldosterone


  Hormones produced from adrenal cortex in response to the simulation of Renin-Angiotensin-Aldosterone-System (RAAS) or in response to a low blood pressure
• Atrial Natriuretic Peptide (ANP)

  • Marker for Congestive Heart Failure (CHF)
  • In response to the secretion of ANP due to high blood pressure and will undergo NATRIURESIS (sodium excretion in the urine)
  • With heart problems, without problems in blood pressure, this is produced normally in response to those conditions
  • With a normal heart, ANP is produced when the blood pressure gets high
• Causes of Hypernatremia


  • Dehydration
  • Cushing's syndrome
  • Insulin therapy
  • Profused sweating
  • Diarrhea (without adequate fluid replacement)
  • Diabetes insipidus (& ADH secretion is deficient)
• Sodium reference ranges


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


  (Value in mmol/L x valence of that ion)
• Sodium is a monovalent ion
• Specimen consideration for sodium

  • Serum or Plasma (Serum is preferred)
  • Sodium heparin as an anticoagulant in plasma can be a source of contamination
  • Hemolyzed sample should not be used
• Methods for sodium measurement

  • Ion Selective Electrode (ISE) - Direct ISE and Indirect ISE
  • Flame Emission Spectroscopy (FES)
  • Spectrophotometry
  • Colorimetric - Albanese Lein method, Maruna Trinder method, Enzymatic approach of Albanese Lein and Maruna Trinder
  • Atomic Absorption Spectroscopy (AAS) - GOLD STANDARD
• Potassium


  • Most abundant intracellular cation
  • Important for nerve impulse transmission and action potential
  • Deficiency or excess may affect both cardiac and 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
• Causes of Hypokalemia


  • Alkalosis
  • Insulin therapy
  • Severe malnutritional deficiency
  • Electrolyte loss in GIT and Urinary
  • Renal losses
• Causes of Hyperkalemia


  • Acidosis
  • Cell damage
  • Acute and Chronic Renal failure
  • Mineralocorticoid (Aldosterone) deficiency
• Potassium specimen consideration


  • Diurnal variation may not be followed
  • Fasting is not required
  • Serum, plasma, and urine is used as a sample
  • Artifactual Hyperkalemia/Pseudohyperkalemia - high platelet count
• Potassium


  To alter the alkalosis condition
• Insulin therapy


  Diabetic patients are at risk of having hypokalemia because Potassium enters their cells as an action of insulin