Chapter 8, Part 2 Water Balance 1. Key Concepts Water compartments inside and outside of cells maintain a balanced distribution of total body water. The.

Chapter 8, Part 2Chapter 8, Part 2Water Balance

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Key ConceptsKey Concepts

Water compartments inside and outside of cells maintain a balanced distribution of total body water.

The human body forms one continuous body of water contained by a protective envelope of skin.

Water moves to ALL parts of the body.

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Key ConceptsKey Concepts

Humans can live 1 month w/o foodHumans can live only 6 days w/o waterBody weight is over ½ waterMale body: 60% - 65% waterFemale body: 50% - 54% waterInfants body: 75% waterPremature infants: 80% water

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Fluid compartmentsFluid compartments

Intracellular Fluid◦Fluid inside cells◦Adults = 65% of body water is intracellular

Extracellular Fluid◦Fluid outside cells◦Adults = 35% of body water is extracellular◦Interstitial (between cells), intravascular (in

blood vessels), lymph (immune system)

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Fluid CompartmentsFluid CompartmentsCopyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 5

Body Water FunctionsBody Water Functions

Solvent◦Basic liquid solvent for all chemical

processes within the bodyTransport

◦Nutrients carried through the body in water-based fluids (e.g., blood, secretions)

Thermoregulation◦Maintains stable body temperature

Body lubricantGives body shape and form

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Body Water RequirementsBody Water Requirements

Include water in food and beverages◦Usual = 80% from fluids◦20% from foods

Dependent upon activity level◦Water is lost as sweat◦More water is needed for increased metabolic

demand in physical activityFunctional losses

◦Disease process affects water requirements, ie: vomiting, diarrhea, fever, diuretic use

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Body Water Requirements, cont’dBody Water Requirements, cont’d

Metabolic needs◦1000 ml of water necessary for every 1000

kcal in the dietAge

◦Infants need 700 to 800 ml of water per day◦3 cups

◦Adults need 2000ml to per day to maintain hydration (food and beverage)

◦8-12 cups

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Other Dietary FactorsOther Dietary Factors

Dehydration◦Excessive loss of total body water◦>2% total body weight loss (>20% fatal)◦Thirst, headache, dizziness, decreased UO,

dry mouth, low BP, kidney failure◦Special concern in the elderly – decreased

thirst sensation, low intakeWater intoxication (excess intake, can

cause hyponatremia – low Na) Elderly, psych pts., use of psychotropic drugs,

prolonged extreme exercise

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Percentage of Body Weight LossPercentage of Body Weight LossCopyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 10

Water BalanceWater Balance

80% water from beverages◦Skim milk = 91% water

4 cups/day water from foods◦Lettuce, celery, vegetables, fruits

Water Losses◦1. Sensible: perspiration, urine, feces◦2. Insensible: lungs, skin

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Water BalanceWater Balance

Daily Weight = single most important indicator of fluid balance

1 kg = 2.2 lbs.Intake and Output should be almost equal

in healthy individualExcessive fluid volume: hypervolemia, I > O, edema, respiratory distressInsufficient fluid volume: dehydration,

hypovolemia, O > I, Low BP

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ElectrolytesElectrolytes

Small, inorganic substances that break apart in a solution and carry an electrical charge (ions)

Cation + charge, Na, K, Ca, MgAnion – charge, Cl, HCO3, PO4, SO4Maintain electrochemical processes and

balance between extracellular/intracellular fluid

Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 13

Organ Systems Involved in Body Organ Systems Involved in Body Water BalanceWater Balance

Gastrointestinal circulation◦Water from blood plasma is continually

secreted into the gastrointestinal tract.◦In the latter portion of the intestine, most water

and electrolytes are reabsorbed into the blood.

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Organ Systems Involved in Body Organ Systems Involved in Body Water Balance, cont’dWater Balance, cont’d

Renal circulation◦Kidney - filters the blood (“cleans the blood”) to

help maintain water balance and electrolyte balance

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SummarySummary

The human body is approximately 50% to 60% water (men have more)

Primary functions of water are to give form and structure to body tissue, provide a water environment for cells to work, and control body temperature

Body water is distributed within the intracellular and extracellular compartments

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