Major intra and extracellular ions

Introduction:

The fluids of the body are solutions of both inorganic & organic solutes. The concentration balances of the various components are maintained in order for the cells & tissues to have a constant environment. If there is imbalance & the body itself cannot correct it, certain products are used by a physician like electrolytes, acids & bases, blood products, amino acids, proteins etc.

The electrolytes concentration will vary with a particular fluid compartment. The three compartments are:

1. Intracellular fluid (45-50% of body weight)

2. Interstitial fluid (12-15% of body weight)

3. Plasma fluid (4-5% of body weight)

These 3 compartments are separated each other by membranes that are permeable to water and many organic and inorganic solutes. They are nearly impermeable to macromolecules such as proteins and are selectively permeable to Na+, K+, and Mg2+

Calcium:

About 99% required for bone formation. Remaining portion is used for blood clotting, neurohormonal functions, muscle contraction & other biochemical processes. Also necessary for release of acetylcholine.

Calcium cations give rise to muscle contractions & it is associated with cyclic AMP. Muscle becomes flaccid when calcium is removed. Deleterious effect of hyperpotassemia on the heart may be due to excessive potassium displacing calcium from cardiac muscle.

Necessary for blood clotting. Here citrate is added to whole blood.

Hypercalcaemia occurs in

1. Hyperparathyroidism2. Hypervitaminosis D3. Some bone neoplastic diseases

Symptoms are fatigue, anorexia, constipation, muscle weakness & cardiac irregularities. If the condition persists, calcium may deposit in kidneys & blood vessels. intestinal absorption of calcium may be reduced by forming sulphate or phosphate salts of calcium or forming complex with EDTA.

Hypocalcemia occurs in

• Hypoparathyroidism• Hypovitaminosis D• Osteoblastic metastasis• Steatorrhea (presence of excess fat in

feces)• Cushing’s syndrome• Acute pancreatitis• Acute hyperphosphatemia

If calcium level falls enough, hypocalcemic tetany may result.

Hypocalcemic tetany:

An abnormal condition characterized by periodic painful muscular spasms and tremors, caused by faulty calcium metabolism and associated with diminished function of the parathyroid glands.

Lack in calcium causes osteoporosis. If the condition progresses, the bones become weaker & more fragile. The possible reasons are:

1. Decreased calcium absorption due to diet or some problems associated with intestinal calcium absorption2. Vitamin D deficiency or reduced level of active metabolite 1, 25 dihydroxy cholecalciferol3. Increased sensitivity to parathyroid hormone especially in post menopausal women4. Bone dissolution

Chloride:

Major extracellular ion and is responsible for proper hydration, osmotic pressure & cation-anion balance in extracellular compartment

Hypochloremia caused by-

1. Salt losing nephritis associated with chronic pyelonephritis leading to lack of tubular reabsorption of chloride

2. Metabolic acidosis in diabetes mellitus & renal failure causing excess acid production leading to replacement of chloride by acetoacetate & phosphate

3. Prolonged vomiting with loss of chloride as gastric HCl

Hyperchloremia caused by-

Dehydration Excess chloride intake

Renal damage

Congestive heart failure

Sodium:

It is the principal cation in the extracellular fluid compartments. It is responsible for maintaining normal hydration and osmotic pressure.

Excess sodium is excreted by kidneys & approx 80-85% are reabsorbed. Kidney releases renin that is a proteolytic enzyme. It cleaves a linear protein & forms angiotensin I. this is again cleaved into angiotensin II which stimulates adrenal cortex to secrete aldosterone & finally this aldosterone increases reabsorption of sodium.

A prostaglandin has also been implicated in the hormonal control of the tubular reabsorption of sodium.

Hyponatremia caused by

Extreme urine loss as in diabetes insipidus Metabolic acidosis Addison’s disease Diarrhea & vomiting Kidney damage

Hypernatremia caused by

Dehydration Excessive sodium intake Certain brain injury Hyperadrenalism (Cushing’s syndrome)

Sometimes if the body is unable to eliminate excess sodium & the concentration starts to increase, water is retained in the tissues to maintain osmotic balance. Edema results & the patient takes a puffy appearance with swelling in the lower extremities. The build-up of fluids puts an added burden on the heart which may be aggravated if the heart is already diseased. Treatments are diuretics, low sodium diet etc.

In temporary conditions, elimination of salts and salted foods will greatly reduce the edema and concurrent weight problems. Sodium free salt substitutes (Neocurtasal® ) can be used to enhance the favour of the food. It contains a mixture of potassium chloride, glutamic acid, potassium glutamate, calcium silicate, and tribasic calcium phosphate.

Potassium:

It is the major intracellular cation present in a concentration approximately 23 times higher than the concentration of potassium in the extracellular fluid compartments.

Hypokalemia can result from:

Vomiting

Diarrhea

Burns

Hemmorhage

Diabetic coma

Intravenous infusion of solution lacking in potassium

Over use of thiazide diuretics and Alkalosis

This hypokalemia can cause:

Change in myocardial function

Flaccid and feeble muscle and

Low blood pressure

Hyperpotassemia or hyperkelmia is less common and usually occurs during certain types of kidney damage.

Hypopotassemia and heart:

Heart is particularly sensitive to the potassium concentration. During hypopotassemia there are alterations in the electrocardiogram and distinct histological change in the myocardium.

An increase potassium concentration also results in change in the ECG and causes the heart muscle to become flaccid with possible cessation of the heart beat (potassium arrest).

It is thought that potassium may be displacing calcium in the cardiac muscle and decrease in calcium exhibit similar result.

Electrolytes used for replacement therapy

Sodium replacement

Occurs as colorless crystals or white crystalline powder having a saline taste. Freely soluble in water, glycerin & slightly soluble in alcohol.

Uses

Isotonic solutions are used as wet dressings, for irrigating body cavities & tissues & as injections when body fluids or electrolytes have been depleted

Hypotonic for maintenance therapy when patients are unable to take fluid or nutrients orally for 1-3 days

Hypertonic when there is loss of sodium in an excess of water. These injections should be given slowly in small volumes (200-400ml)

Dose:

Oral-1g 3 times dailyIv infusion-1 liter of a 0.9% solutionTopically to wounds and body cavities, as a0.9% soluiton for irrigation

Preparations

Sodium chloride injection Bacteriostatic NACL injection Sodium chloride solution Sodium chloride tablet Dextrose and sodium chloride injections Sodium chloride and Dextrose

Potassium Replacement therapy:

Occurs as a colorless, elongated, prismatic or cubical crystal or as a white granular powder.

Potassium chloride is the drug of choice for oral replacement of Potassium preferably as a solution. It is irritating to the gastrointestinal tract and solutions must be well diluted

The USP requires that the tablet must be enteric coated but several authorities do not recommend the use of tablets due to the possibility of small bowel ulceration and absorption is undependable.

In addition it is used-

1. In the treatment of familial periodic paralysis ( a recurring, rapidly progressive, flaccid paralysis).

2. Meniere’s syndrome (disease of the inner ear which include dizziness, and noise in the ear.

3. As an antidote in the digitalis intoxication

4. As an adjunct to drugs used in the treatment of myasthenia gravis ( a progressive, sever muscle weakness).

When given orally, KCl is mixed with fruit or vegetable juice to mask the saline taste

Dose:

Usual dose: 1 g four times daily

Usual dose range: 500 mg to 8 g daily

Occurrence:

Potassium chloride injection

Potassium chloride Tablets

Ringer’s injection (contains 0.03% KCl)

Lactate Ringer’s solution

Lactate potassic Saline injection

Calcium replacement:

Occurs as white, hard odorless granules that are hygroscopic. Freely soluble in water, & alcohol. Its irritating to veins & should be injected slowly. Rapid injection may cause burning sensation, peripheral vasodilation & a fall in BP.

Ringer’s injection-contains 0.033% CaCl2.2H2O, iv infusion 1 liter

Lactated ringer’s injection- contains 0.02% CaCl2.2H2O, iv infusion 1 liter

Electrolyte combination therapy:

Electrolyte combination therapy is of two types:

Fluid maintenance therapy

Electrolyte replacement therapy

Maintenance therapy is given intravenously to supply normal requirements for water & electrolytes to patients who cannot take them orally. These solutions usually contain 5% dextrose. This minimizes the build up of those metabolites that are associated with starvation: urea, phosphate & ketone bodies.

The composition of maintenance therapy is:

Ingredients mEq/L

Sodium 25-30

Potassium 15-20

Chloride 22

Bicarbonate 20-23

Magnesium 3

Phosphorus 3

Replacement therapy is given when there is heavy loss of water & electrolytes as in prolonged fever, severe vomiting & diarrhea.

This is of two types:

Rapid initial replacement solution

Subsequent replacement solution

The composition of rapid initial replacement solution is:

Ingredients mEq/L

Sodium 130-150Potassium 4-12

Chloride 98-109Bicarbonate 28-55

Calcium 3-5

Magnesium 3

The composition of subsequent replacement solution is:

Ingredients mEq/L

Sodium 40-121

Potassium 16-35

Chloride 30-103

Bicarbonate 16-53

Calcium 0-5

Magnesium 3-6

Phosphorus 0-13

Some official combination electrolyte infusions are:

Ringer’s injection

Lactated ringer’s injection

Oral electrolyte solutions

Oral rehydration therapy

Oral rehydration therapy (ORT) is a simple treatment for dehydration associated with diarrhea. ORT consists of a solution of salts and sugars which is taken by mouth. It is used around the world, but is most important in the developing world, where it saves millions of children a year from death due to diarrhea.

Concentrations of ingredients in ORS

Ingredients g/L

Sodium chloride (NaCl) 2.6

Glucose, anhydrous (C6H12O6)

13.5

Potassium chloride (KCl) 1.5

Trisodium citrate, dihydrate Na3C6H5O7•2H2O

2.9