Electrolytes

Potassium (K⁺)

Sample for Potassium (K⁺)

1. This is done on the serum of the patient.
   1. Separate serum as soon as possible.
2. Plasma can be used, but it gives slightly lower values.
3. A random sample may be taken.
4. Serum or plasma is stable for one week at room temperature or 1°C to 4 °C.

Precautions for Potassium (K⁺)

1. Avoid hemolysis which may increase the value.
2. Avoid prolonged tourniquet or repeated fist clenching during venipuncture, increasing potassium value.
3. Increased value of platelets or white blood cell counts will increase value. 
4. EDTA should not be used because it contains K⁺.
5. Serum or plasma should be separated within 3 hours to prevent leakage of the K⁺ from the blood cells.
6. Incomplete separation of serum and clot.
7. Excess food intake or rapid potassium I/V therapy.
8. Drugs with high potassium contents, like penicillin G.
9. Transfusion of the old stored blood.

Indications for Potassium (K⁺)

1. Potassium is part of electrolytes estimation.
2. Potassium is advised in all serious patients.
3. Potassium is advised in patients with the treatment of diuretics or heart medication.

Pathophysiology of Potassium (K⁺)

1. Potassium is the main electrolyte of intracellular fluid.
2. About 2 to 3 grams of potassium is ingested in the food and excreted in the form of salts.
3. The intestine rapidly absorbs potassium salts.
   1. There is very little effect on the plasma level.
   2. After the body needs potassium is excreted through the kidneys

4. The daily potassium intake is 40 to 150 meq/day, and the average is 1.5 meq/Kg body weight.
5. The intracellular Potassium is 150 meq/L and in the blood is just approximately 4 meq/L

6. This intracellular and extracellular potassium ratio is very important to maintain membrane electrical potential.
7. Potassium is the primary buffer system in the cells.
8. The main concentration of potassium is within the cell, almost 90%.
9. A very small amount is present in the blood and bone.
10. When the cells are damaged, potassium is released into the blood and may give rise to increased value.

Excretion of Potassium:

1. 80 to 90% of Potassium is excreted by the glomeruli in the urine (filtered at the glomerulus).
2. Reabsorbed passively in the proximal tubules and actively in the thick ascending loop of Henle.
3. Secreted or actively reabsorbed in the distle convoluted tubules or collecting ducts, depending upon the potassium blood level

4. A lesser amount of 10 to 20% is excreted in the sweat and stool.
5. Potassium’s role in the body is vital.

The site of K+ loss	K+ loss
Urine	40 to 120 meq/L
Stool	5 to 10 meq/L
Sweat	0 to 20 meq/L

6. Kidneys do not conserve potassium, so potassium may be deficient in the case of decreased intake.
7. A normal adult needs 80 to 200 meq /day of potassium in the diet.

Potassium concentration depends upon the following:

1. Hormonal effect where aldosterone and, to some extent, glucocorticoids increase Renal Potassium loss.
2. Absorption of Sodium,  When Sodium is reabsorbed, then Potassium is lost.

The functions of Potassium (K+):

1. Most potassium is found within cells (intracellular), which significantly influences the conduction of electrical impulses in cardiac and skeletal muscles.
2. Potassium plays a vital role in the following:
   1. Nerve conduction.
   2. Muscular function.
   3. Osmotic pressure.
   4. Protein synthesis.
   5. Acid-base balance.
   6. In numerous enzyme reactions of carbohydrate and protein metabolism.
   7. Cardiac output, heart muscle contraction, and the rate are controlled by potassium, calcium, and magnesium.
   8. Potassium deficiency on ECG shows the presence of a U wave.

Potassium (K⁺) role in acid-base balance:

1. H⁺ ions are substituted for Potassium and Sodium in the renal tubules.
2. Potassium is more important than sodium.
3. Potassium bicarbonate (K⁺HCO₃^–)  is the only intracellular inorganic buffer.
4. In Potassium deficiency, in other words, there is a decrease in HCO₃^–, so pH will be relatively acidic.
5. Now the respiratory center is stimulated by low pH and lowering of pCO₂ through hyperventilation.

Alkalosis:

Hypokalemic alkalosis:

1. Lower the serum Potassium by shifting the K into cells.
2. The excess excretion usually sees this of potassium loss by the kidneys into the urine, usually seen in excessive use of some diuretics that cause potassium and sodium loss.
3. When excess potassium is lost in the urine, intracellular potassium diffuses from the cells to replace some of that being lost from plasma.
4. Sodium (Na⁺) and hydrogen (H⁺) ions move into the cells to replace the K⁺ that have moved out.

Acidosis: 

Hyperkalemic acidosis:

1. In acidosis, potassium K+ moves from the cells into the blood. This is a reverse phenomenon.
2. Release from the cells is greater than excretion from the kidneys. This occurs in acidosis and anoxia.

Hyperkalemia (Increased concentration of K⁺ in the blood):

1. This is due to the following:
   1. Increased potassium is released into the blood.
   2. Or due to the kidney, which cannot excrete the potassium.
   3. Or due to low urine output

Hypokalemia (Decreased concentration of the K⁺ in the blood):

1. This is due to potassium loss in vomiting, diarrhea, GIt fistula, and diuretics.
2. Aldosterone increase leads to a decrease in potassium.

Signs and Symptoms of Potassium (K⁺):

1. The S/S depends upon the concentration of the K⁺ in the blood.
2. Potassium level <2.5 meq/L 
   1. There will be tachycardia.
   2. There is increased muscular irritability.
      1. There are specific cardiac conduction defects.
      2. There is a stoppage of the heart in the systole.
   3. There is a flattened T – wave.
   4. The end result will be cardiac arrest.
3. Potassium level <3.0 meq/L
   1. There are marked neuromuscular symptoms.
4. Hyperkalemia
   1. There is mental confusion.
   2. There is a weakness.
   3. There is a tingling sensation.
   4. Flaccid paralysis of limbs.
   5. There is a weakness in the respiratory muscles.
   6. There is bradycardia.
   7. There are prolonged PR and QRS intervals.
   8. There is a peaked T- wave.

Critical values are:

1. Potassium level >6.5 meq/L
   1. There is peripheral vascular collapse.
   2. Inhibit muscle irritability.
   3. Ultimately cardiac arrest and stoppage of a heartbeat.
2. Potassium level <2.5 meq/L
   1. Cardiac electrical activity can be seriously altered with arrhythmias.
3. The potassium level of 10.0 meq/L
   1. It is fatal to the patient’s life and stops the cardiac activity.

NORMAL Potassium (serum)

Source 1

Age	meq/L
Premature cord blood	5.0 to 10.2
Premature 48 hours	3.6 to 6.0
Newborn cord	5.6 to 12.0
Newborn	3.7 to 5.9
Infant	4.1 to 5.3
Child	3.4 to 4.7
Adult	3.5 to 5.1

• To convert to SI units x 1.0 = mmol/L

Source 2

• Adult =  3.5 to 5.0 meq/L
  Child = 3.4 to 4.7 meq/L
• Infants = 4.1 to 5.3 meq/L.
• Newborn = 3.9 to 5.9 meq/L.
• Urine       =  25 to 125 meq /day.
• CSF = 2.2 to 3.3 meq/L

Hyperkalemia or increased serum Potassium level was seen in:

1. Increased dietary uptake.
2. Acute and chronic renal failure.
3. Addison’s disease.
4. Decreased Aldosterone and hypoaldosteronism.
5. Hemolysis.
6. Transfusion of hemolyzed blood.
7. Uncontrolled diabetes mellitus.
8. Metabolic acidosis.
9. In Burns, accidents, surgery, chemotherapy, and DIC.
10. Kidney transplant rejection.
11. Decreased excretion of potassium in the urine:
    1. Renal failure.
    2. Acidosis.
    3. Adrenocortical insufficiency.              

Changes in ECG of hyperkalemia, There are the following changes:

1. T -wave is elevated.
2. P -wave is flattened.
3. Cardiac arrest may occur without warning of any other changes.
4. Nearly all cases of acidosis are associated with hyperkalemia.

Hypokalemia or decreased Potassium level is seen in:

1. 1. Decreased dietary intake.
   2. Dehydration.
   3. Acidosis.
   4. An increased gastrointestinal loss like diarrhea and vomiting.
   5. Excessive sweating.
   6. Starvation and malnutrition.
   7. Cystic fibrosis.
   8. Severe burns.
   9. Respiratory alkalosis.
   10. Renal tubular acidosis.
   11. Respiratory alkalosis.
   12. Diuretics.
   13. Hyperaldosteronism.
   14. Cushing syndrome.
   15. Trauma due to surgery or burns.
   16. Gastrointestinal losses like vomiting, nasogastric tube, diarrhea, and villous adenoma.
   17. Renal losses like diuretics, antibiotics (ampicillin-B and carbenicillin), hypomagnesemia, renal tubular acidosis, mineralocorticoid excess, congenital adrenal hyperplasia, and Cushing’s syndrome.
   18. There may be transcellular shifts like alkalosis and correction of diabetic ketoacidosis.

Changes in ECG in hypokalemia are the following changes:

1. T – waves are depressed.
2. P – wave has peaked.
3. ST – depression.
4. U- wave is prominent.

Nonrenal potassium loss causes:

Definition of nonrenal potassium loss:

1. These patients have hypokalemia, and urinary potassium is <25 meq/24 hours or <15 meq/L due to extra-renal causes.
2. The causes are:
   1. Vomiting.
   2. Diarrhea due to infections, malabsorption, or radiation.
   3. Neoplasms like villous adenomas of the colon and Zollinger-Ellison syndrome.
   4. Excessive spitting in neurotic patients.
   5. Excessive sweating.
   6. Cystic fibrosis.
   7. Excessive burns.
   8. Respiratory alkalosis.
   9. Accidental absorption of barium compounds.
   10. Dietary deficiency.

Pseudohyperkalemia is characterized by the following:

1. There are raised potassium and no clinical changes in the patient as cardiac excitability.
2. The ECG can confirm this.
3. In these patients, no treatment is needed, and in fact, this may be harmful.
4. In such cases, the potassium may be released in the following conditions:
   1. In vitro hemolysis.
   2. In vitro clot formation.
   3. Thrombocytosis.
   4. Leukocytosis.
   5. Due to tourniquet use.

Potassium (K⁺)  level in blood and urine in various conditions:

Various clinical conditions	Potassium (K+) level in the blood	Potassium (K+) level in urine
Diarrhea	Decreased	Normal or decreased
Dehydration	Increased	Increased
Malabsorption	Decreased	Decreased
Starvation	Decreased	Increased or normal
Excessive sweating	Normal	Normal
Pyloric obstruction	Decreased	Normal
Congestive heart failure	Normal	Normal
Pulmonary emphysema	Normal	Normal
Acute renal failure	Increased	Decreased
Chronic renal failure	Normal or decreased	Increased
Renal tubular acidosis	Decreased	Increased
Primary aldosteronismm	Decreased	Increased
Adrenal cortical insufficiency	Increased	Normal or decreased
Diabetic acidosis	Normal or increased	Increased
Diabetes inspidus	Normak	Normal
Thiazide diuretics	Decreased	Increased
Mercurial diuretics	Decreased	Increased
Diamox (Acetazolamide)	Decreased	Increased

• Note: Please see more details in Electrolytes.

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