Download Electrolytes

Electrolytes
Electrolytes
Electrolytes are anions or cations
Functions of the electrolytes
• Maintenance of osmotic pressure and water
distribution
• Maintenance of the proper pH
• Regulation of the proper function of the heart
and other muscles
• Involvement in oxidation –reduction reactions
• Cofactors for enzymes
Sodium
Sodium ions are the major cations of extracellular
fluid
Clinical significance:
• Hyponatremia (decreased plasma Na concentration)
- Unusual losses due to excessive sweating,
prolonged vomiting, or persistent diarrhea
- Renal loss due to diuretics, deficiency of
aldosterone, or severe polyuria
- Excessive retention of water (dilutional type)
due to chronic cardiac failure, hepatic cirrhosis,
nephrotic syndrome and malnutrition .
NB : Pseudohyponatremia is analytical artifact
that may be seen with lipemic specimens
• Hypernatremia (increased plasma Na concentration)
due to:
Eg: - Parenteral therapy with saline solutions
- Hyperaldosteronism
Specimens:
Serum, heparinized plasma, whole blood, sweat, urine,
feces, or gastrointestinal fluids may be assayed .
Stored at 2 to 4 C or frozen for delayed analysis
Determination of sodium in body fluids :
• Electrochemically with an ion-selective
electrode (ISE)
• Flame emission spectrophotometry (FES)
• Spectrophotometric methods
Reference Intervals : 136 to 145 mmol/L
Potassium
Potassium is the major intracellular cation
Clinical significance:
• Hypokalemia (decreased plasma K concentration)
- decrease intake eg : starvation
- redistribution of extracellular K into intracellular fluid
eg: with insulin therapy , alkalosis
- increase loss of K: ♦ GI loss (vomiting, or diarrhea)
♦ renal loss (diuretics eg:thiazides)
• Hyperkalemia (increase plasma K concentration)
- IV infusion of K
- Transfer of intracellular K into extracellular fluid occur
in cases of dehydration, acidosis, or severe burns .
- Decreased excretion of K in acute renal failure or end
stage renal failure
Specimens : for serum or plasma assay of K must be
collected in such a way as to minimize hemolysis
(release of K from erythrocytes can increase the serum
level )
Determination of potassium in body fluids :
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Atomic absorption spectroscopy
Electrochemically with an ion-selective electrode (ISE)
Flame emission spectrophotometry (FES)
Spectrophotometric methods
Reference Intervals :
- For serum of adults
- For serum of newborns
3.5 to 5.1 mmol/L
3.7 to 5.9 mmol/L
•
Chloride
Chloride is the major extracellular anion
Hypochloremia (decreased plasma Cl concentration)
Is observed in salt-losing nephritis as associated
with chronic pyelonephritis
Hyperchloremia (increased plasma Cl concentration )
Occurs with dehydration, renal tubular acidosis,
and acute renal failure
Determination of chloride in body fluids
Specimens :
chloride is measured in serum or plasma, urine,
and sweat
• Spectrophotometric Methods
• Ion-Selective Electrode Methods
Bicarbonate (total carbon dioxide)
Clinical Significance :
• Alterations of HCO3- and CO2 dissolved in plasma are
characteristic of acid-base imbalance
• When acid-base imbalance is suspected, evaluation of
blood gases and pH is required .
- Increase in CO2 occur in metabolic alkalosis due to:
eg: severe vomiting
hypokalemic states
- Decrease in CO2 are seen in:
eg: renal failure
Methods for The determination of serum or
plasma total carbon dioxide
The first step in many automated methods is the
acidification of the sample to convert the various
forms of CO2 in plasma to gaseous CO2
• Enzymatic method
• Direct ISE method