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REVIEW- FLUID AND ELECTROLYTES

Pabitra Sharma

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Review… Water present in the body is body water.

Water of the body together with its dissolved solute is called body fluid

The distribution of total body water is as follows:

Muscle(50%), Skin( 20%), Blood( 10%), other organ( 20%) Total body water depends upon age, sex

and degree of obesity

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Role of body fluid Essential constituent of all cells Serves as transport medium of nutrient

and excretory products Acts as medium of cellular reaction Valuable solvent for vitamins, enzymes,

electrolyte even fat Thermoregulation Cellular integrity

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Water balanceDaily intake Fluids ingested 2100ml From metabolism- 200 mlDaily output Insensible (skin) -350ml Insensible( lungs) -350ml Sweat- 100ml Faces- 100ml Urine -1400ml

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Factor affecting water balance Thirst mechanism Condition of kidney Temperature and humidity Endocrine gland Hypothalamus Electrolyte diet

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Water Balance contd… (Positive)

Liver damages Hypothyroidism Using drugs Changes in dietary habit balance Growing period Pregnancy Recovery from disease

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Water Balance contd… Negative

Vomiting, diarrhoea and hemorrhage Burns Excessive salivation NPO Unconscious state Hypo function of adrenal gland diseases

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Body fluids Intra cellular – fluid occupied inside the

cells. Intracellular fluid is found inside the bi-layered plasma membrane in which cellular organs are suspended and chemical reaction takes place

Extracellular- fluid in the spaces outside the cells including interstitial fluid, plasma and trans cellular fluid of the body

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Trans cellular- specialized ECF or another small compartment of fluid. It is the fluid separated from plasma by epithelium. This compartment includes: Synovial, Peritoneal ,Pericardial, Intraocular, CSF

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Body Fluid Distribution

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women have less water than men if they are the same weight…..??? The water content of adipose tissues is

less than that of muscle, while Women have more adipose tissues at the

effects of feminine hormone

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Composition and function of ICF

Composition Electrolyte, protein, cholesterol,

phospholipids, neutral fatFunction Provides fluid media within the cells for

chemical reaction Buffering action

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Composition and functions of ECF

Composition Electrolyte, Glucose, Fatty acid, amino acid, chemical

messenger, oxygen and other nutrients, ureaFunctions Establishes the milieu interior Provides nutrients to the cells Removes metabolic waste materials from immediate

cellular environment It brings to the cells hormones that co-ordinate the

functions of widely separated cells Buffering action

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Fluid movement Solute- the substance that dissolved solvent- substance in which solute is

dissolved Osmolality-Concentration of solute per

kg of water Osmolarity- concentration of solute per

liter of solution Solution substances that dissolved in

other substances

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Fluid movement Fluid and solute constantly move within

the body, which allows the body to maintain homeostasis

Fluids along with nutrients and waste products constantly shift within the body’s compartment from the cell to the interstitial spaces, to the blood vessels and back again

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Fluid movement Contd…. Types of transportA. Active transportB. Passive transport- Diffusion- Osmosis- filtration

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Active Transport Particles to travel in the reverse direction

across the membrane and have particles travel from an area of LOW concentration to an area of HIGH concentration, but in order to counteract the force of diffusion the cell must expand energy, this process is called Active Transport

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Active Transport Contd… Active transport is the movement of

material through a membrane Against a concentration gradient. Active transport require energy

The energy for active transport comes from ATP(Adenosine Triphosphate) , generated inside mitochondria

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Active Transport Contd… This process requires specialized protein,

which are carrier protein to bind with particles and transport it.

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Passive Transport DiffusionThe movement of molecules from a area in which they are highly concentrated to a area in which they are less concentrated.

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Diffusion Contd… There is greater concentration of free waterMolecules outside the cell diffusion process

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Diffusion process

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osmosis Osmosis is the spontaneous net movement of

solvent molecules through a partially permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides

Osmosis provides the primary means by which water is transported into and out of cells

Difference in concentration between solutions on either side of semi permeable membrane called Osmotic gradient 

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Osmosis Contd….. For osmosis potential water molecule

have to move is called osmotic potential. Distilled water has the highest potential ( Zero)

When water has another substance dissolved in it , the water molecules have have less potential to move. Then the osmotic potential is called negative.

The osmotic potential of a cell is known as its water potential. For a animal cell the water potential is the osmotic potential of the cytoplasm.

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Osmosis Contd… Osmole- Measures of solution’s ability to create osmotic

pressure and thus affect movement of water- Proportional to the number of osmotic particles

formed in solution Osmolality- - When the concentration of a solution is

expressed in osmoles per kilogram of water, the osmolar concentration of a solution is referred to as its osmolality

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Osmosis Contd…. In normal condition, the osmolality of

plasma =interstitial fluid= intracellular fluid=280-310mmol/l

The osmolality is determined mainly by: In ECF: Na and CL(80%)( in clinical

practice, serum osmolality can be estimated by doubling serum sodium)

In ICF- K+(50%)

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Osmosis Contd…. In animal cells, the water potential is equal

to the osmotic potential o the cytoplasm, but this is different in plant cell

Plant cell have a cell wall, which exerts an inwards pressure when the cell in turgid. This is known as pressure potential

The water potential of an animal cell is equal to the osmotic potential of the cytoplasm plus the cell wall pressure

W.P=O.P+P.P

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Osmosis Contd…..Osmotic pressure Pull that draws solvent through the membrane to

the more concentrated side Determined by the number of particles instead of

the mass of the solute in the solutionIt can be: Crystal osmotic pressure- formed by a lot of small

molecular weight material, such as electrolyte, glucose, BUN, and so on

Colloid osmotic pressure- formed by large molecular weight materials such as protein.

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Calculation of osmolality Osmolality – 2Na+Glucose/18 + BUN/2.8 Glucose + urea= plasma Osmolality Effective osmolality (tonicity)- 2Na+

Glucose/18

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Oncotic pressure Oncotic pressure, or colloid osmotic

pressure is a form of osmotic pressure exerted by blood plasma proteins. It usually tends to pull water(fluids) in to circulatory system(capillaries)

It is the opposing force to hydrostatic pressure

Its normal value is about 20-25mmof Hg

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Contd…. Capillary oncotic pressure(COP)-

pressure that pulls fluids back into the capillary

Tissue oncotic pressure (TOP)- pressure that pulls fluids out of the capillary as a result of free proteins attracting fluids.

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Hydrostatic Pressure Hydrostatic pressure is the pressure exerted by the

fluid against the containerCapillary Hydrostatic pressure (HP)(Capillary blood pressure)- tends to force fluids through capillary wall- Greater at atrial end ( 35mm of hg) than venuleend ( 17)Interstitial fluid hydrostatic pressure- Pressure that would push fluid into vessels- Usually assumed to be zero because of lymphatic

vessels

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Mechanism in fluid exchange The forces which govern this exchange

of fluid between the plasma and the interstitial fluids are

- Hydrostatic pressure due to fluid tension with in circulation

- The colloid osmotic pressure of the plasma proteins

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Mechanism in fluid exchange Contd…

The hydrostatic pressure is much higher in the capillaries than in the tissues spaces and tends to drive fluid out of the capillaries by filtration

The osmotic pressure is much higher in the blood plasma than in the interstitial fluid and tends to draw back into the capillaries by osmosis

These two forces act on opposite direction

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While the osmotic pressure is uniform throughout the capillaries length, the hydrostatic pressure falls from the arterial to the venular end. At the arterial end of the capillary the hydrostatic pressure is greater than the colloid osmotic pressure and therefore, fluid tends to pass out of the capillaries. At the venule end of the capillaries, the hydrostatic pressure is less than the colloid osmotic pressure and therefore, H2o is reabsorbed into the capillaries at this end of the capillaries.

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Contd… For every 100 calories metabolized, the

body loses about 65ml water in the urine, 40 ml by sweating , 15ml by lungs and about 5ml in the feces, whereas it gain 15ml from metabolic processes.

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Electrolyte Cation (Positively charged ins) of human fluids A positively charged ion or electrolyte;

Sodium, Potassium, Magnesium (ECF) Sodium, Potassium, Magnesium (ICF)

Anion A negatively charged ion or electrolyte;

chloride, bicarbonate, phosphate, sulfate Protein and organic acids (ECF). Chloride,

bicarbonate, Phosphate and protein (ICF)

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Electrolyte Electrolyte are the electrically charged

minerals that when dissolved in water or another solvent, forms or dissociated into ions ( electrically charge particles conduct electric current)

Electrolyte are distributed through out fluid compartment of the body. The solution is known as electrolyte solution.

Common electrolyte are bases, acid and salts

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Electrolyte balance Electrolyte balance ( charged minerals)

in the fluids helps distribute the fluids Inside and outside the cells., thus

ensuring the appropriate water balance and acid-base balance to support all life processes.

Excessive losses of fluids and electrolyte disturb these balances, and the kidneys play a key role in restoring homeostasis.

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Electrolyte contd… Substances can cross the membrane

because of the membrane’s property of being partially permeable • That is it is permeable to some substances and not to others.

 Some substances are able to move into the cell and some are allowed out.

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Sodium Chief electrolyte of ECF that moves easily between

intravascular and interstitial spaces and moves across cell membranes by active transport

Influential in many chemical reactions in body, particularly nervous and muscle tissue cells

Controls and regulates volume of body fluids; maintains water balance through out the body

Primary regulator of ECF volume and influences ICF Participates in generation and transmission of nerve

impulses Essential electrolyte in sodium-potassium pump Normal extracellular concentration: 135 – 145 mEq/L

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Potassium Major cation of ICF working in reciprocal fashion with sodium

(excessive intake of sodium results in excretion of potassium, vice versa)

Chief regulator of cellular enzyme activity and cellular water content

Plays vital role in such processes as transmission of electric impulses, particularly nerve, heart, skeletal, intestinal, and lung tissue; protein and carbohydrate metabolism.

Adequate quantity, usually in well-balanced diet Food sources include bananas, peaches, kiwi, figs, dates,

apricots, oranges, prunes, melons, raisins, broccoli, potatoes, meat and dairy products- excreted primarily by kidneys, however, there are large amounts in GI secretions and some in perspiration and saliva- normal range for serum: 3.5 – 5 mEq/L

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Calcium Most abundant electrolyte, with up to 99% of

total found in iodized form of bones and teeth Close link between concentrations of calcium

and phosphorus- necessary for nerve impulse transmission and blood clotting-

Catalyst for muscle contraction- needed for vitamin B12 absorption and its use by body cells

Acts as catalyst for most cell chemical activities

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Calcium Contd… necessary for strong bones and teeth determines thickness and strength of cell

membranes adult avg. daily requirement about 1 g, higher

amts. according to body wt. required for children and pregnant and lactating women- 1,500 mg/day recommended consumption for older adults,

particularly postmenopausal women and men older than 65

sources include milk, cheese, and dried beans, some present in meats and vegetables.

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Magnesium Most cation found within body cells –

heart, bone, nerve, and muscle tissues 2nd most important cation in ICF Important for metabolism of

carbohydrates and proteins- important for many vital reactions involving enzymes

Necessary for protein and DNA synthesis, DNA and RNA transcription, and translation of RNA

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Magnesium Maintains normal intracellular levels of

potassium Helps maintain electrical activity in

nervous tissue and muscle membranes Adult daily avg. requirement about 18

– 30 mEq, with children requiring larger amts.

Found in most foods, but especially in vegetables, nuts, fish, whole grains, peas and beans

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Chloride Chief extracellular anion, found in blood, interstitial

fluid, and lymph and in minute amounts in ICF Acts with sodium to maintain osmotic pressure in

blood- plays a role in body’s acid-base balance Has important buffering action when oxygen and

carbon dioxide exchange in red blood cells Essential for production of hydrochloric acid in

gastric juices- found in foods high in sodium, dairy products, and meat-

Deficit leads to potassium deficit, and vice versa- normal serum levels: 95 – 105 mEq/L

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Bicarbonates Anion that is major chemical base buffer

within body- found in both ECF and ICF Essential for acid-base balance; bicarbonate

and carbonic acid constitute body’s primary buffer system

losses possible via diarrhea, diuretics, and early renal insufficiency

Excess possible via over ingestion of acid neutralizers, such as sodium bicarbonate

Normal levels range between 25 – 29 mEq/L. 

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Phosphate Major anion in body cells Buffer anion in both ICF and ECF Helps maintain body’s acid-base balance Involved in important chemical reactions

in body (necessary for many B vitamins to be effective, helps promote nerve and muscle action, plays a role in carbohydrate metabolism)

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Phosphate Important for cell division

and transmission of hereditary traits- avg. daily requirements similar to calcium

Found in most foods but especially in beef, pork, and dried peas and beans

Inversely proportionate to calcium - - increase in one results in decrease of the other- normal range: 2.5 – 4.5 mEq/L

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Normal value Sodium 35-145mEq/l Potassium (k+) 3.5-5.0mEq/l Ionized Calcium (Ca++) 4.5- 5.5mg/dl Calcium (Ca ++) 8.5- 10.5mg/dl Bicarbonate (HCO3) 24-30mEq/l Chloride( Cl-) 95-105mEq/l Magnesium 9Mg++) 1.5-2.5mEq/l Phosphate (PO4) 2.8- 4.5 mg/dl

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Fluid Tonicity

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Isotonic (240-340 mOsm) Solution has the same solute

concentration or osmolality as normal blood plasma (290 mOsm) and other body fluids

Solution stays where it is infused, inside the blood vessels

Expand the intravascular compartment, it does not affect the size of the cell and solution helps to maintain body fluid balance.

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RL 273 mOsm/lRinger’s 309 mOsm/l

NS 308 mOsm/l

D5 252 mOsm/l

Intra lipids 10% 280- 300 mOsm/l

D5 ¼ NS- 5% Dextrose and .2 NaCl

320 mOsm/l

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Hypotonic solution Solution has lower osmolality than serum

(< 240 mOsm/L) Solution causes a fluid shift out of the

blood vessels into the cells and interstitial spaces

Solution hydrates cells while reducing fluid in the circulatory system

e.g – ½ NS- 0.45 NaCl)

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Hypertonic solution Solution has an osmolality higher than

serum > 340 mOsm/L Causes the solute concentration of the

serum to increase pulling fluid from the cells and the interstitial compartment into the blood vessels

Reduces the risk of edema, stabilize blood pressure and regulates urine outputs

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D 10 505 mOsm/L D 50 1700 mOsm/LD5 ½ NS 406 mOsm/LD5NS 559 mOsm/L

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Group of fluids

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Crystolloids Are isotonic and remain isotonic in the

vasculature and are therefore effective volume expanders for a short period of time

Ideal for patient who need fluid volume replacement

examples- RL,NS

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Colloids Used to increase vascular volume

rapidely drawing fluid from the interstitial and intracellular compartment into the vascular compartment

They work well in reducing edema( pulmonary and cerebral) while expanding the vascular compartment

Examples- albumin, manintol, dextran etc