ELECTRONEUTRALITY
| Na+ + K+ + 7 = Cl– + HCO3- + 25 |
ANION GAP: difference between unmeasured anions and unmeasured cations
| AG = Na+ – (Cl– + HCO3-) | AG = Na+ + K+) – (Cl– + HCO3-) |
| Ref. range: 7-16 mmol/L | Ref. range: 10-20 mmol/L |
| Information |
| Sodium |
- Most abundant cation in the ECF
- Has the greatest influence in serum osmolality
- Aldosterone: responsible for the reabsorption in tubules
- Atrial natriuretic factor: blocks secretion of both aldosterone & renin
- Hyponatremia is the most common electrolyte disorder
- ~for every 100mg/dL increase in blood glucose, there is a decrease by 1.6 mmol/L of serum sodium
| Hypernatremia | Hyponatremia | | Excessive water loss | Increase water retention | | Water intake is decreased | Water imbalance | Increase Na+
intake/retention | Sodium loss |
Methods: - Flame Emission Photometry (FEP) – yellow
- ISE – glass aluminum silicate
- AAS
- Colorimetry – Albanese Lein
|
| Potassium |
- Major intracellular cation
- Regulates ICF volume regulation and H+ concentration
- contraction of the heart and excitability of mucles
| Hyperkalemia | Hypokalemia | | Extracellular shift | Renal loss | | Increased intake | GI loss | | Renal excretion is decreaed | Intracellular shift | Artifactual (eg. Hemolysis,
thrombocytosis) | Intake is decreased |
Methods: - FEP – violet
- ISE – valinomycin gel
- AAS
- Colorimetry – Lockhead and Purcell
|
| Chloride |
- Major extracellular anion
- Only anion that serves as an enzyme activator
- Sweat chloride: diagnosis for cystic fibrosis
| Hyperchloremia | Hypochloremia | | GI loss | Hyperparathyroidism | | Diabetic ketoacidosis | Low reabsorption of HCO3 | | Low Na+ levels | | | Mineralocorticoid excess & deficiency | |
Methods: - Mercurimetric method: Schales and Schales (indicator: diphenylcarbazone)
- Coulometric amperometric titration: Cotlove chloridometer
- Colorimetry ISE – electrodes with AgCl membranes
|
| Calcium |
- Ion that is the most abundant in the body
- 3rd most abundant in blood
- 99% (bone) and 1% (blood)
- PTH: promotes bone resorption
- Calcitonin: promotes bone deposition
- Vitamin D3: promotes intestinal absorption of calcium
Methods: - Clark & Collip Precipitation (titration with KMnO4)
- FEP
- AAS – reference method
- ISE – liquid membrane
|
| Magnesium |
- 2nd major cation in ICF
- 4th most abundant ion in the body
- 2nd mostly affected by hemolysis (after potassium)
Methods: - AAS – reference method
- Colorimetry – Calmagite (reddish-violet)
- Dye method – Titan yellow
|
| Bicarbonate |
- 2nd most abundant ECF anion
- Acts as buffer
- Diffuses out of the cell in exchange for chloride
- Increased levels: alkalosis, vomiting, hypokalemia
- Decreased levels: acidosis
Methods: - ISE – Clark electrode
- Enzymatic method: Phosphoenolpyruvate carboxylase & dehydrogenase
|
| Phosphorus |
- Unstable ion
- Inversely proportional to calcium and PTH
- Best preserved by acidic filtrate
|
| ELECTROLYTES | FUNCTION |
| HCO3, K, Cl | Acid-Base Balance |
| Ca, Mg | Blood coagulation |
| Mg, Ca, Zn | Cofactors in enzyme activation |
| K, Mg, Ca | Myocardial rhythm and contractility |
| K, Ca, Mg | Neuromuscular excitability |
| Mg, PO4 | Production and use of ATP from glucose |
| Mg | Regulation of ATPase pumps |
| Na, K, Cl | Volume and osmotic regulation |
