Electrolytes – Part 4 – Sodium and Potassium (Na+ and K+), ECG changes
- This test is done on the serum of the patient.
- No special preparation is needed.
- Sodium and Potassium are Stable in blood at room temperature for one hour and in Serum at 2° C to 8 °C for 24 hours.
- Other references say that stability is one week at room temperature or 1°C to 4 °C.
- The plasma may be used (heparinized).
- Avoid hemolysis which has a dilution effect.
- No preservative is needed for the urine sample.
- Avoid sodium heparin.
- For electrolyte imbalance evaluation and monitor therapy.
- In diuretic therapy to find the K+ level.
- In dehydration to know the level of Na+ and K+.
- In severe vomiting and diarrhea to find the level of Na and K+.
- Potassium is very important in serious patients and patients with diuretic therapy and heart medication.
- Sodium: 136 to 145 meq/L
- Potassium : 3.5 to 5.5 meq/L
- Sodium is the major extracellular cation with a serum level of 140 mEq/L and the intracellular level is 5 mEq/L.
- Extracellular osmolality depends upon sodium.
- The sodium level in the blood depends upon the dietary intake and excretion by the kidney.
- The loss in the sweating of sodium is minimal.
- Aldosterone regulates sodium by increasing reabsorption of sodium and decreasing its loss by kidneys.
- Antidiuretic hormone ADH controls the resorption of water at distal tubules, and effect sodium serum level by dilution or concentration.
- Physiologically sodium and water are interrelated. If body water increases then sodium level will be diluted and decreases in amount.
- If the water contents of the body decreases then sodium will increase in the blood.
- Dietary sodium 90 to 250 mEq/L is needed to maintain the sodium level.
- Hyponatremia when the sodium level is less than 125 mEq/L
- Hyponatremia symptoms are a weakness.
- Hyponatremia level when falls below 115 mEq/L, then the patient goes into confusion and lethargy. This condition may progress to stupor and coma if the sodium level keeps on lowering.
- Hypernatremia leads to dryness of mouth, thirst, agitation, restlessness, hyperreflexia, mania, and convulsions.
- Drugs increasing sodium level are anabolic steroids, antibiotics, corticosteroids, cough medications, laxatives, methyldopa, estrogen, and oral contraceptives.
- Drugs leading to decreased levels are diuretics, sodium-free I/V therapy, ACE inhibitors, captopril, sulphonylureas, haloperidol, nonsteroidal anti-inflammatory drugs, and vasopressin.
- Potassium is the major intracellular cation with a concentration of 150 mEq/L and the extracellular is 4 mEq/l.
- Potassium is important to maintain the membrane electrical potential, especially in the neuromuscular tissues.
- The potassium amount is small in the serum, so the even small change in concentration have significant changes.
- Potassium is excreted by the kidney but this is not resorbed by the kidneys.
- If there is a deficiency in the intake of potassium in the diet, or by I/V therapy, then there will be a drop in the potassium level.
- Potassium has an important role in protein synthesis and maintenance of oncotic pressure.
- Potassium also maintains the cellular electrical neutrality.
- The kidney can shift potassium for hydrogen ions concentration to maintain physiological pH.
- Serum potassium concentration depends upon:
- Aldosterone increases the loss of potassium.
- Sodium is reabsorbed and potassium is lost.
- Alkalosis lower sodium by causing the shifting of potassium into the cell. While acidosis tends to raise potassium by shifting by reversing the shift.
Hypokalemia When there is a decreased level of potassium that will lead to:
- Decreased contraction of the muscles ( smooth, skeletal, and cardiac ).
- There are weakness and paralysis.
- There is hyporeflexia.
- There is ileus.
- There is an increased sensitivity to digoxin.
- There are cardiac arrhythmias.
- There is a flattened T wave and prominent U wave.
Hyperkalemia will lead (Sign/Symptom) to:
- Nausea and vomiting.
- Intestinal colic and diarrhea.
- ECG shows a peaked T wave and widened QRS complex.
- There are depressed ST segments.
Drugs leading to increased potassium levels are:
- Antineoplastic medicines.
- Isoniazid INH.
- Potassium-sparing diuretics.
Drugs leading to decreased potassium level are:
- Glucose infusion.
- Aminosalicylic acid.
- Note: Sodium and potassium discussed separately.