Fluid And Electrolyte Balance-Intracellular fluid-Extracellular fluid-nterstitial fluid

 

Fluid And Electrolyte Balance

 

·         Intracellular fluid: Intracellular fluid (ICF) is found within cells. It contributes mainly 40% of the total body weight. ICF is essential for normal cell function and provide a medium for metabolic processes.

·         Extracellular fluid: Extracellular fluid is located outside the cells. It accounts for approximately 20% of total body weight.

·         Interstitial fluid: Interstitial fluid is present between the spaces in most of the cells of the body. It contributes approximately 15% of the total body weight in the body.

·         Intravascular fluid: It is called plasma and is present within the arteries, veins and capillaries. It contributes approximately 5% of the total body weight.

·         Transcellular fluid: Transcellular fluid is present in urine, digestive secretions, perspiration and cerebro spinal, pleural, synovial, intraocular, gonadal and pericardial fluids.

·         Osmosis: Osmosis is the movement of solvent molecules through their selectively permeable membrane into an area of higher solute concentration and its main aim is to equalize the solute concentrations on the both sides.

·         Diffusion: Diffusion is defined as the spread of particles through random movement from regions of higher concentration to regions of lower concentration is called diffusion.

·         Filtration: Filtration is the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass is called filtration.

·         Active transport: active transport is the movement of a substance against its concentration gradient from low concentration of high concentration.

·         Metabolic water: Metabolic water is the water created inside living organism through the oxidation of energy substrate in food. In human, 300 mL of water is generated as a result of oxidation of glucose in body.

·         Electrolytes: Electrolytes are minerals/elements involved in essential processes in one body. Major electrolytes in our body are: Na, K⁺, CI, HCO₃.

 

INTRODUCTION

 

            Homeostasis is the body’s tendency to maintain a state of physiologic balance of constantly changing conditions. Normal physiologic is processes depend on a relatively stable state in the internal environment of the body. The fluid and electrolyte composition, and pH of both intracellular and extracellular spaces must remain constant to maintain health and life.

            Fluid and electrolyte balance mechanism maintain the composition and distribution, movement of fluid and electrolyte in the body.

 

Body Fluid Composition

 

            The composition of the body fluid is water and various dissolved substances and total body water constitute, about 60% of the total body weight. This amount varies with age, gender and the amount of fat. The total body water decreases with aging such as in people above the age of 65 years, the body water may decrease from 45% to 50% of total body weight.

Water

 

The main component of body fluid is water. The water present in the body is never plain water but electrolytes are also present in it. When the body loses water then it loses electrolytes as well. Sodium is the principal electrolytes of extracellular fluid while potassium is the main electrolyte in intracellular spaces. The ion concentration in intracellular and extracellular fluids is maintained by the balance between intake of water and the output of water in the body.

 

Functions Of Water To Maintain Normal Cellular Functions

 

·         Water is an essential constituent of all cell of body.

·         Water provides medium for transportation and exchange of nutrients in body.

·         Water is essential for metabolic reactions within the cell. It provides a medium for metabolic reactions.

·         Water assists in regulating body temperature of the body.

·         Water is a valuable solvent in which various substances such as electrolytes, hormones, enzymes and vitamins are carried from one place to another and is acts as lubricant too.

·         Water form a part in body tissues, e.g. the amniotic fluid surround and protect the fetus during pregnancy.

·         Water helps in maintaining the form and texture of tissues.

·         Water helps for maintenance of acid-base balance is body.

 

Distribution of water in body:

 

Insensible water losses:

            Total body water (TBW) – 60% of body weight (BW) in Males

-          50% of BW in females

-          80% of BW in infants

 

Distribution – 60% BW (40% - Intracellular Fluid (ICF) + 20% - Extracellular fluid (ECF) plasma (5% BW) + Interstitial fluid 15%) 

 

            Electrolytes in ECF – (Na⁺ /C1-/HCO₃, Glucose, O₂, fatty Acid)

 

Requirement Of Daily Water In Body:

 

For the maintenance of normal fluid balance, it is necessary that body water intake and output should be approximately equal.

 

In India, the average fluid intake and output is usually about 2,500 mL in 24 –hour period.

 

Minimum six to eight glasses of water is recommended to keep one active. The consumption of water depends upon climate condition, standard of living, physical activities and habits of people. Water should be consumed at regular intervals.

 

 

Sources of Water	Daily Requirement of water (mL)
Beverages and liquid food	1,500 – 1,750 mL
Water content of solid food	600-900 mL
Metabolic water	300-350 mL
Total	2,400-3,000 mL

 

Daily output of water:

 

Daily output through	Fluid loss (mL)
Urine	1,200-1,500
Skin	700-900
Lungs	400
Feces	100-200
Total	2,400-3,000

 

Daily Intake and Output of Water:

 

Intake of water:

 

There are three major sources of water:

 

·         Beverages and liquid food: It includes tea, coffee, milk shakes, fruit juices and soup which are largely made up of water.

·         Water content of solid food: It includes fruits vegetables and water used for cooking food.

·         Metabolic water: It is synthesized in body as a result of oxidation of fat, protein and carbohydrates. Total water intake varies widely from 1,500 mL to 6,000 mL.

 

Regulation of Water Metabolism:

 

·         Regulation of fluid gain

·         Regulation of fluid loss

 

Regulation of fluid Gain

 

Three hormones play main role in the maintenance of fluid volume in the body. These are:-

·         Antidiuretic  hormone (ADH)

·         Aldosterone

·         Atrial natriuretic peptide (ANP)

 

The water intake is regulated by the thirst reflex which stimulates the person to drink water. Dehydration occurs in the body when the water loss is greater than water gain. Dehydration stimulates the thirst reflex in three ways:

·         The amount of salivation drops resulting in a dryness of mucosal membrane of mouth and pharynx.

·         The increase in blood osmotic pressure which stimulates the osmo receptors of hypothalamus in brain.

·         Fall in blood volume.

 

Regulation of Fluid Loss:

The water is lost from body due to:

·         The insensible water losses from lungs and skin.

·         The water that accompanies undigested food residues in feces.

 

Water is lost by:

·         Kidney excrete 900-1200 mosm pf solutes to maintain blood homeostasis.

·         Urine solutes that must be out from body in form of water.