Electrolytes

• Electrolytes


  Ions capable of carrying an electric charge (+/-)
• Types of electrolytes


  • Cations
  • Anions
• Cations


  • Have positive charge
  • Migrate toward the cathode
• Cations


  • Mg2+
  • Ca2+
  • Zn2+
  • Na+
  • K+
• Hyponatremia


  <135 mmol/L
• Hypernatremia


  High sodium concentration
• Anions


  • Have negative charge
  • Migrate toward the anode
• Anions


  • Cl-
  • HCO3-
  • PO4-
• Functions of electrolytes


  • Volume and osmotic regulation
  • Myocardial rhythm and contractility
  • Important cofactors in enzyme activation
  • Regulation of ATP ion pumps
  • Maintenance of acid-base balance
  • Neuromuscular excitability
  • Blood coagulation
  • Production and use of ATP from glucose
• 40-75% is the average water content of the human body
• Excess fluid


  Suppresses ADH
• Lack of fluid


  Stimulates ADH
• Extracellular Fluid (ECF)


  Fluid outside the cells, represents 1/3 of total body
• Intravascular ECF (plasma)


  93% water, inside the veins
• Interstitial fluid


  Water around the cells, 7% of ECF
• Intracellular Fluid (ICF)


  Water within the cells, represents 2/3 of total body water
• ADH (Antidiuretic Hormone)


  Also known as AVP (Arginine Vasopressin Hormone)
• Sodium (Natrium)


  Major extracellular cation (90% of all extracellular cations), outside of the cell, principal osmotic particle outside the cell
• Reference values for sodium: 135-145 mmol/L
• Hypernatremia


  Sodium concentration >145 mmol/L, report immediately
• Hyponatremia


  Sodium concentration <120 mmol/L, report immediately
• Causes of hypernatremia


  • Excess water loss
  • Decreased water intake
• Causes of hyponatremia


  • Excess water loss
  • Increased water retention
  • Water imbalance
• Methods of sodium determination

  • Flame Emission Photometer
  • Ion Selective Electrode
  • Atomic Absorption Spectrophotometry
  • Colorimetry
• Potassium (Kalium)


  Major intracellular cation (only 2% circulates in plasma), single most important analyte in terms of an abnormality being immediately life threatening
• Reference value for potassium: 3.5-5.2 mmol/L
• Factors affecting potassium levels

  • Hemolysis
  • Muscular activity
  • Prolonged contact of serum and red cells
  • Prolonged tourniquet application
  • High bicarbonate levels
• Causes of hyperkalemia


  • Decreased renal excretion
  • Extracellular shift
  • Increased intake
  • Artifactual
• Causes of hypokalemia


  • Gastrointestinal loss
  • Intracellular shift
  • Renal loss
• Magnesium


  Second most abundant intracellular cation, 4th most abundant cation, essential cofactor of more than 300 enzymes, involved in cardiovascular and neuromuscular functions
• Reference value for magnesium: 1.2-2.1 mEq/L
• Forms of magnesium


  • Free or ionized (55%)
  • Complexed with ions (15%)
  • Bound to proteins (30%)
• Causes of hypermagnesemia


  • Decreased excretion
  • Increased intake
• Causes of hypomagnesemia


  • Decreased intake
  • Decreased absorption
  • Increased excretion
• Chloride


  Major extracellular anion (counterpart of Na in extracellular fluid), promotes maintenance of osmolality, blood volume and electric neutrality, only anion to serve as an enzyme activator
• Reference value for chloride: 98-107 mmol/L
• Factors affecting chloride levels

  • Hemolysis
  • Reduced intake
  • Increased excretion
• Bicarbonate


  2nd most abundant anion in the ECF, accounts for 90% of total CO2 at physiologic pH, buffers excess hydrogen by combining with acid, major component in buffering system of blood
• Reference value for bicarbonate: 21-28 mEq/L (venous blood plasma or serum)
• Calcium


  Present almost exclusively in the plasma, involved in blood coagulation, enzyme activity, excitability of skeletal and cardiac muscle, maintenance of BP