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INTRODUCTION

Body is formed by solids and fluids. The fluid part is more than 2/3

of the whole body. Water forms most of the fluid part of the body.

In human beings, the total body water varies from 45 to 75% ofbody weight. In a normal young adult male body contains 60-65%

of water and 35-40% of solids. In a normal adult female, the water is

50-55% and solids are 45-50%. In females, the water is less because

of more amount of subcutaneous adipose tissue. In thin persons,

water content is more than in obese persons. In old age, water

content is decreased due to increase in adipose tissue. The total

quantity of body water in an average human being

Weighing about 70 kg is about 40 litres.

COMPARTMENTS OF BODY FLUIDS

Total water in the body is about 40 litres. It is distributed into two major

fluid compartments namely :

1. Intracellular fluid (ICF) forming 55% of the total body water

(22litres).2. Extracellular fluid (ECF) forming 45% of the total body

water( 18 litres).

Extracellular fluid is divided into 5 subunits:-

1) Interstitial fluid and lymph

2) Plasma

3) Fluid in bones

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a

4) Fluid in dense connective tissue like cartilage

5) Transcellular fluid that includes:

a. Cerebrospinal fluid

b. Intraocular fluid

c. Digestive juicesd. Serous fluid- intra pleural fluid

- Pericardial fluid

- peritoneal fluid

e. Synovial fluid in joints and

f. Fluid in urinary tract

The volume of Interstitial fluid is about 12 liters. The volume of plasma

is about 2.75 liters. The volume of other subunit of extracellular is about

3.25 liters. Water moves between different compartments.

COMPOSITION OF BODY FLUIDS

Body fluids contains water and solids. Solids are organic and inorganic.

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Organic substances-

Organic substances are glucose, amino acids, proteins, enzymes, fatty

acids, lipids and hormones.

Inorganic substances-Inorganic substances present in body fluids are sodium, potassium,

calcium, magnesium, chloride, bicarbonate, phosphate and sulfate.

Extracellular fluid contains large quantity of sodium, chlorides,

bicarbonate, glucose, fatty acids and oxygen.

PH of extracellular fluid is 7.4

Intracellular fluid contains large quantities of potassium, magnesium,

phosphates, sulfates, proteins.

PH of intracellular fluid is 7.0

ELECTROLYTE

Electrolyte is defined as any substance containing free ions that make

the substance electrically conductive. Example- sodium, chloride,magnesium, phosphate, sulfate etc.

REGULATION OF ELECTROLYTES AND FLUIDS

There are four rules of regulation of fluids and electrolyte:-

1) All homeostatic mechanisms for fluid composition respond to

changes in the ECF.

- Receptors monitor the composition of plasma and CSFand triggers neural and endocrine mechanisms in response

to change.

- Individual cells cannot be monitored and thus ICF has no

direct impact.

2) No receptors directly monitor fluid or electrolyte balance

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- only plasma volume and osmotic concentration are

monitored which give an direct measure of fluid or electrolyte levels.

3) water follows salt

- cells cannot move water by active transport.

- water will always move by osmosis and this movementCannot be stopped.

4) The body`s content of water or electrolyte rises and loss to and from

the environment.

- Too much intake = high content in the body.

- Too much loss= low content in the body.

PRIMARY REGULATORY HORMONE

a. Antidiuretic Hormone(ADH)-Osmoregulators in the hypothalamus monitor the ECF and release ADH

in response to high osmotic concentration( low water, high solute.)

Increase in osmotic concentration causes increase in ADH levels.

Primary effects of ADH:-

a) It stimulate water conservation at kidneys.

b) It stimulate thirst.

b.Aldosterone-It is released by the adrenal cortex to regulate sodiumabsorption and

potassium loss in the DCT and collecting system in the kidney.

Retention of sodium will result in water conservation.

Aldosterone is released in response to :

a) high potassium or low sodium in the ECF( e.g. renal circulation)

b) activation of renin- angiotensinogen system due to a drop in blood

pressure or blood volume.

c) Decline in kidney filtrate osmotic concentration at the DCT.

Natriuretic peptides- It is released in response to stretching of heart wall.

It function to reduce thirst and block release of ADH and aldosterone

resulting in diuresis.

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The above diagram shows how the regulation of sodium ion levels in theextracellular fluid take place in the case of drop in the blood pressure.

Here, there is decrease in the blood pressure leading to increased renin

secretion from kidney and secretion of angiotensinogen which is

converted into angiotensinogen1 and later into angiotensinogen2 which

in turn stimulate aldosterone secretion from adrenal cortex. Aldosterone

stimulates sodium ions and promotes water reabsorption in the kidney.

An increase in the blood pressure in the right atrium of the heart causes

increased secretion of atrial natriuretic hormone which increases the

sodium ion secretion and water loss in the form of urine.Below the diagram is showing how the electrolyte regulation takes

place in the body with increased blood pressure and how the hormones

maintain it to the normal.

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CONCENTRATION OF BODY FLUIDS

The concentration of body fluids is measured by three ways-

1) OSMOLALITY:- it determines the distribution of water among

different compartments of extracellular and intracellular compartments.

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It is expressed as number of particles per kg of solvent. In other words it

is the concentration of osmotically active substances in the solution.)

2) OSMOLARITY:-

It is expressed as the number of osmoles / litre of solution.When osmolality of ECF increases, water moves from ICF to ECF.

When osmolality of ECF decreases water moves from ECF to ICF.

Water movement continues until osmolality of these two fluid

compartment becomes equal.

3) TONICITY:-

It refers to relative concentration of solute particle inside a cell with

respect to concentration outside the cell.when RBC are placed in-

A) ISOTONIC RBC placed in isotonic solution neither gain nor lose

water because of osmotic equilibrium between inside and outside cell

membrane. eg; 0.9% Nacl solution and 5% glucose.

B) HYPERTONIC - In RBC ,water moves out of cells resulting in

shrinkage of cells(crenation) eg-2%Nacl.

C)HYPOTONIC- In RBC, water moves into the cells resulting in

swelling and rupture of cells. eg- 0.3%Nacl.

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REGULATION OF BODY FLUIDS:

The body fluids mainly regulate by the following processes:

1) Diffusion

2) osmosis

3) Filtration4) Active transport

1) DIFFUSION-It is also known as passive transport i.e. no external

source of energy is required by which molecules moves from areas of

high concentration to areas of low concentration. it is the movement of

substances along the concentration or electrical gradient or both is

known as diffusion.eg- swimming in direction of water flow in river. It

is also known as downhill movement. It doesnt require energy.It is of two types- simple diffussion

- facilitated diffussion

Simple diffusion occurs through the lipid bilayer and the rate of

diffusion is directly proportional to the lipid solubility. No carrier

protein binding.

Facilitated diffusion requires interacting carrier protein with the

molecules.

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2) OSMOSIS- --It is the passive flow of the solvent.Process of movement

of water caused by a concentration difference of water

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3) FILTRATION - It is the movement of water and solutes from an

area of high hydrostatic pressure to an area of low hydrostatic

pressure.

4) ACTIVE TRANSPORT- When a cell membrane moves molecules

or ions uphills against a concentration gradient, the process isknown as active transport. eg- sodium potassium pump.

It is the movement of substances against chemical or electrical or

both gradient is known as active transport. Eg swimming in opposite

direction to water flow. It is also known as uphill transport and

requires energy in the form of adenosine tri phosphate. It occurs with

help of carrier protein as in case of facilitated diffusion. Each carrier

protein carry only one substance known as uniport pump. If more

than one substance is known as antiports/ symport.

Mechanism of active transport- when the substance to be transported

across cell membrane it combines with carrier protein of cell membrane

leading to formation of protein complex. This complex move towards

the inner surface of cell membrane. The substance is then released from

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carrier protein and the carrier protein moves back to outer surface of cell

membrane.

Substances transported by active transport are in two form-

Ionic form- sodium, choride, calcium, potassium.Eg; sodium potassium pump for distribution of sodium and potassium

across cell membrane. It transport sodium from inside cell to outside and

potassium from outside intio the cells.

Non ionic form- glucose, amino acids, urea.

Diagram showing active and passive transport.

ACID BASE BALANCE

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ACID- is a substance that liberates hydrogen ions. (Donor)

BASE- is a substance that accepts hydrogen ions. (Acceptor)

In healthy person PH of ECF=7.4 and varies from 7.38and 7.42

Maintenance of acid base status is important

As even a slight change in Ph causes serious threats to physiologicalfunction.

REGULATION OF ACID BASE BALANCEThere are three different

mechanism :

a) Acid base buffer system which binds hydrogen ions.

b) Respiratory mechanism which eliminates carbon dioxide.

c) Renal mechanism which excretes hydrogen ions and conserves the

bicarbonate ions.Acid base buffer is fastest one and it can readjust ph within seconds.

Respiratory mechanism adjust the ph in minutes.

Renal mechanism is slower and it takes few hours to few days to bring

ph back to normal. It is the most powerful mechanism than others.

DETERMINATION OF ACID BASE STATUS

It is difficult to measure by direct method.

Indirect method can be calculated by Henderson hasselbalch equation.To determine ph of fluid the concentration of bicarbonate ions and

carbon dioxide dissolved in fluid are measured.

PH= PK+ LOG HCO3_ / CO2

ACID BASE BUFFER SYSTEM

It is of three types:-

a) Bicarbonate buffer system

b) Phosphate buffer system

c) Protein buffer system

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Above diagram showing the types of acid base buffer system that occur

in the ICF and ECF.

The bicarbonate buffer system is not very powerful because the pk of

bicarbonate is 6.1 while the ph of ECF is 7.4 as there is large difference

between them.

While the phosphate buffer system is comparatively more powerful as

the pk value is 6.8 and the ph of ICF is 7.1 as there is less difference.

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ACID BASE DISTURBANCES

The acid base disturbances are-

-Respiratory Acidosis

-Respiratory Alkalosis-Metabolic Acidosis

-Metabolic Alkalosis

The clinical manifestation, lab findings and the management is given in

the table.

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SIGNIFICANCE OF BODY FLUIDS

1. In Homeostasis :-

Body cells survive in the fluid medium or milieu interieur.

Term Milieu interieur given in 19th century by french physiologist

Claude bernard.

Growth and functions of cells depend upon the availability of minerals

like glucose, amino acids, lipids, oxygen in proper quantities in internalenvironment. The maintenance of internal environment is called as

HOMEOSTASIS.

The term homeostasis is given by the Harvard profecessor Walter b

menon. Homeostasis is of two types positive feedback mechanism and

the negative mechanism.

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) IN TRANSPORT MECHANISM:

Water forms an important medium through which various enzymes,

hormones, minerals, vitamins are carried from one part to another part of

body.

3) IN METABOLIC REACTIONS:Water inside the cells forms the medium for metabolic reaction

necessary for growth and functional activities of the cells.

4) IN TEMPERATURE REGULATION

Fluid plays a vital role in maintanence of normal body temperature

MEASUREMENT OF VOLUME OF BODY FLUIDS

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It is measured by Indicator dilution method or dilution method.

Principle:- A known quantity of substance or dye is administered into

body fluid compartment. After administration it is mixed thoroughly and

sample of fluid is drawn to determine the concentration of markersubstance.

substances whose concentration can be determined by calorimeter or

radio active substances are used as marker substances.

Formula to measure volume of fluid

V= M/C

Where V is volume of fluid compartnent

M is mass or quantity of marker substances.

C is the concentration of marker substance in sample fluid.Correction factor some amount of marker substance is lost through

urine during distribution.

Volume= Amt of substance injected- Amt of

substance excreted/ concentrationn of sustance in sample of

fluid.

USES OF INDICATOR DILUTION METHOD

It is used to measure ECF volume, plasma volume and total body water.

Marker substances used to measure total body water are Deuterium

oxide

- Tritium oxide

Substances used to measure Extracellular fluid Radio active sodium,

chloride, bromide, sulfate thiosulfate.

- Non metabolizable saccharides like inulin, mannitol, sucrose.

Substances used to measure plasma volume

- radio active 131i- Evan`s blue (T- 1824)

MEASUREMENT OF INTRACELLULAR FLUID VOLUME

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The volume intracellular fluid cannot be measured directly. It is

calculated as

ICF volume= total body water- ECF volume

MEASUREMENT OF INTERSTITIAL FLUID VOLUMEIt is calculated as:

Interstitial fluid volume= ECF volume- plasma volume

APPLIED PHYSIOLOGY

FLUID VOLUME DEFICIT

( HYPOVOLEMIA)Mild:- 2% of body weight loss

Moderate:- 5% of body weight loss

Severe:- 8% of body weight loss

Pathophysiology results from loss of body fluids and occurs more

rapidly when coupled with decreased fluid intake

Clinical manifestation:--Acute weight loss

-Decrease skin turgor

-Oliguria

-Concentrated urine

- Postural hypotension

- Weak, rapid, heart rate

- Flattened neck veins

- Increased temperature

- Decreased central venous pressure

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Management

-Fluid replacement therapy & continued fluid maintenance.

Fluid Volume Excess (Hypervolemia)

- An increase in the interstitial fluid volume of about 2 L or more due to

increase transudation of fluid from capillaries 2 to:

-Increased HP [pregnancy, CHF]

-Decreased OP [malnutrition, end-stage liver disease, nephrotic

syndrome]

An excess of water in the ECC w/ a normal amount of solute or adeficient amount of solute

It occurs in prolonged and excessive diuresis, forcing hypotonic fluids

to produce diuresis in the presence of renal impairment

fluid overload from increased production of adrenal corticoid hormones

(Cushings syndrome)

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Clinical manifestations edema, distended neck veins, crackles,

tachycardia, increased blood pressure, increased weight

Management

--Restrict fluids to lower fluid volume-Diuretics or hypertonic saline

-Continuous assessments to prevent skin breakdown

Record daily weight of the patient.

Electrolyte Balance:

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-Electrolyte balance is important because:-total electrolyte concentrations directly affect waterbalance

- concentrations of individual electrolytes can affect cellfunctions-The two most important electrolytes are sodium andpotassium:1) Sodium Balance (normal blood values: 130-145 mEq/L*)-Na+ is the dominant cation in the ECF

-90% of the ECF osmotic concentration is due to sodiumsalts:NaCl and NaHCO3-The total amount of Na+ in the ECF is due to a balancebetween Na+ uptake inthe digestive system and Na+ excretion in urine andperspiration

The overall sodium concentration in body fluids rarely

changes because water always moves to compensate:e.g. high sodium levels in the blood will cause retentionof waterto maintain the same Na+ concentration, but this resultsina high blood volume (this is why salt is bad forhypertensive patients)-Minor gains and losses of Na+ in the ECF are

compensated by water in the ICFand later adjusted by hormonal activities:-ECF volume too low

renin-angiotensin system is activated toconserve water and Na+-ECF volume too high

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natriuretic peptides released: blockADH and aldosterone resulting in water and Na+ loss

Normal range 135 to 145 mEq/L

Hyponatremia

Sodium level less than 135 mEq/L

It may be caused by vomiting, diarrhea, sweating, diuretics, etc

Clinical manifestations- Poor skin turgor

- Dry mucosa

- Decreased saliva production

- Orthostatic hypotension

- Nausea/abdominal cramping

- Altered mental status

MANAGEMENT:-- Sodium replacement

- water restriction

- Ringer lactate solution, isotonic solution(0.9%)- in cases who

cannot eat or drink.

Hypernatremia

Sodium level is greater than 145 mEq/L

- Can be caused by a gain of sodium in excess of water or by a loss of

water in excess of sodium

Pathophysiology

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Fluid deprivation in patients who cannot perceive, respond to, or

communicate their thirst.

Mostly affects very old, very young, and cognitively impaired

patients

Clinical manifestations

Thirst

Dry, swollen tongue

Sticky mucous membranes

Flushed skin

Postural hypotension

MANAGEMENT

Diuretics given in sodium excess

Administration of hypotonic sodium solution(0.3 to 0.45%)

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Potassium

It is a major Intracellular electrolyte about 98% of the bodys

potassium is inside the cells. It Influences both skeletal and cardiac

muscle activity.

Normal serum potassium concentration 3.5 to 5.5 mEq/L.

-K+ is the dominant cation in the ICF (98% of the totalbody K+ is inside cells)-The concentration of K+ in the ECF depends onabsorption in the GI vs.excretion in urine

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-The exchange pump at the kidney tubules secrete K+ (orH+) in order toreabsorb Na+-The rate of tubular secretion of K+ in the kidney is

controlled by three factors:1. Changes in the K+ concentration of the ECF

K+ in ECF = K+ secretion2. Changes in blood pHat low pH, H+ is used for Na+ reabsorption instead of K+at the

exchange pump pH in ECF = K+ secretion3. Aldosterone levels

aldosterone = Na+ reabsorption and K+ secretion

Hypokalemia

Causes:

Diarrhea, diuretics, poor K intake, stress, steroid administration.

Manifestation:-

1)Skeletal muscle weakness2)Constipation

3)Irregular, weak pulse

4)Orthostatic hypotension

5)Numbness (paresthesia)

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6)ECG changes ( ST elevation)

Nursing interventions:

-Encourage high K foods-Monitor ECG results

-Dilute KCl can cause

-cardiac arrest occurs if given IV

Administering IV Potassium

-It Should be administered only after adequate urine flow has been

established. Decrease in urine volume to less than 20 mL/h for 2 hours is

an indication to stop the potassium infusion

IV K should not be given faster than 20 mEq/h

Hyperkalemia

Serum Potassium greater than 5.5 mEq/L

- It is more dangerous than hypokalemia because cardiac arrest is

frequently associated with high serum K+ levels.

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Causes:

- Decreased renal potassium excretion as seen with renal failure

and oliguria

- High potassium intake

- Renal insufficiency- Shift of potassium out of the cell as seen in acidosis

Clinical manifestations:

-Skeletal muscle weakness/paralysis

-ECG changes

-such as peaked T waves,

-widened QRS complexes

-Heart block

Medical/Nursing Management :- Monitor ECG changes telemetry

- Administer Calcium solutions to neutralize the potassium

- Monitor muscle tone

- Give Kayexelate

- Give Insulin

Calcium

-More than 99% of the bodys calcium is located in the skeletal system

The normal serum calcium level is 8.5 to 10mg/dL and needed for

transmission of nerve impulses. Intracellular calcium is needed for

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contraction of muscles.Extracellular needed for blood clotting. Itis needed for tooth and bone formation and needed for maintaining

a normal heart rhythm.

Hypocalcemia

The Serum Calcium level less than 8.5 mEq/L

Causes- Vitamin D/Calcium deficiency

- Hyperparathyroidism

- Pancreatitis

- Renal failure

Clinical Manifestations

- Tetany and cramps in muscles of extremities

Definition A nervous affection characterized by intermitent tonic

spasms that are usually paroxysmal and involve the extremities

.

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Trousseaus sign carpal spasms

Chvosteks sign cheek twitching

Medical/Nursing management

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- IV or orally Calcium Carbonate or Calcium Gluconate

- Encourage increased dietary intake of Calcium

- Monitor neurological status

Hypercalcemia>10mg/dl)

Causes :

- Hyperparathyroidism

- Prolonged immobilization

- Thiazide diuretics

- Large doses of Vitamin A and D

-

- Clinical manifestations :- Muscle weakness, nausea and vomiting

- Lethargy and confusion

- Constipation

- Cardiac Arrest (in

- hypercalcemic crisis,

- level 17mg/dL or

- higher)

Medical/Nursing Management

- Eliminate Calcium from diet

- Corticosteroids drugs decreases the intestinal absorbtion of

calcium.

- Increase fluids (IV or Orally)

- Calcitonin

- used to lower serum calcium level

- useful for pts with heart disease or renal failure

- reduces bone resorption

- increases deposit of calcium and phosphorus in the bones

- increases urinary excretion of calcium and phosphorus

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Magnesium

It Helps maintain normal muscle and nerve activity. It Exerts

effects on the cardiovascular system, acting peripherally to

produce vasodilation.Thought to Normal serum magnesium level

is 1.5 to 2.5 mg/dl. It have a direct effect on peripheral arteriesand . arterioles.

Hypomagnesemia

Causes- (Mg< 1.5mg/dl)

- Chronic Alcoholism

- Diarrhea


- Neuromuscular irritability

- Positive Chvosteks and Trousseaus sign

- ECG changes with prolonged QRS, depressed ST segment, and

cardiac dysrhythmias

- May occur with hypocalcemia and hypokalemia


- IV/PO Magnesium replacement, including Magnesium Sulfate

- Give Calcium Gluconate if accompanied by hypocalcemia

- Monitor for dysphagia, give soft foods

-Measure vital signs closely

-Foods high in Magnesium: Green leafy vegetables

Hypermagnesemia

Causes- Renal failure

- Untreated diabetic ketoacidosis

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- Excessive use of antacids and laxatives


- Flushed face and skin warmth

- Mild hypotension

Phosphorus

- Normal serum phosphorus level is 2.5 to 4.5 mg/dL

- Essential for the function of muscle and red blood cells,

maintanence of acid-base balance, and nervous system

- Phosphate levels vary inversely to calcium levels

- High Calcium = Low Phosphate

- Causes

- Most likely to occur with overzealous intake or administration ofsimple carbohydates

- Severe protein-calorie

- malnutrition (anorexia or alcoholism)

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- Muscle weakness

- Seizures and coma

- Irritability- Fatigue

- Confusion

- Numbness


- IV Phosphorus in severe cases.

- Monitor phosphorus levels- Increase oral intake of phosphorus rich foods

Hyperphosphatemia

Serum Phosphorus level greater than 4.5 mg/dl

Causes- Renal failure

- Chemotherapy

- Hypoparathyroidism

- High phosphate intake


- Tetany

- Muscle weakness

- Similar to Hypocalcemia because of reciprocal relationship

CONCLUSION

Stabilizing ECF and ICF involves

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1. Fluid balance

2. Electrolyte balance

3. Acid base balance

so, the minimium water requirement for fluid replacement for 70 kg

human in temperate zone is 3 litre /day and in tropical zone is 4.1litre/day.

REFERENCES

Essentials of medical physiology-Ksembulingam and P

sembulingam.

Textbook of medical physiology- Guyton, Hall.

Fluer strand physiology- A Regulatory Approach Macmillan. Fluid and Electrolyte disorders Dr. c.k pandey

Indian J. Anaeth2003, 47(5) 380-387.

Amy warenda czura, Ph.D

Nutrients in drinking water WHO 2003 Report

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