Intravenous Therapy Module Fluid and Electrolyte Balance

Intravenous Therapy Module

Fluid and Electrolyte Balance

Body Fluids

Comprise 45-77% of the body’s weight

Vary depending on

Age

Lean body mass

sex

Body Fluids

Contain these dissolved substances

Electrolytes

Gases

Nonelectrolytes

Body Fluids

Divided into two main compartments

Intracellular (ICF)

Extracellular (ECF)

Body Fluids

ICF – fluid within the cells (64-70%)

ECF – all fluid outside the cells (30-36%) Intravascular fluid (plasma)

Interstitial fluids (fluid surrounding tissue cells and includes lymph)

Water as a Percentage of Body Weight

Water

Compartment Infant %

Adult

Man %

Adult

Woman %

Elderly

Person %

Extracellular

Intravascular 4 4 5 5

Interstitial 25 11 10 15

Intracellular 48 45 35 25

Total-body water 77 60 50 45

Source: Taylor, Lillis & LeMone, page 1273.

ElectrolytesElectrically charged ions which are

dissolved in a solution positive charged ions – cations negative charged ions – anions

Homeostasis requires an equal number of total cations and anions When not in balance, the person is at risk

for alterations in health

Electrolyte Composition of Body Fluids According to Compartment

0

20

40

60

80

100

120

140

160

Na K Ca

Mg

HC

O3 Cl

PO

4

Sul

fate

Mill

eq

uiva

lent

s p

er

lite

r

PlamaInterstitial fluidCellular fluid

Cations Anions

Electrolytes

Major intracellular electrolytes Potassium – major cation of ICF; has a

reciprocal relationship with sodium

Magnesium – 2nd. Most important cation in ICF; mostly found in cells of heart, bone, nerve and muscle tissues

Phosphate – Major anion in body cells; acts as a buffer anion in both ICF and ECF

Sulfate – anion found primarily within cells and is associated with cellular protein

ElectrolytesMajor extracellular electrolytes

Sodium – Chief electrolyte of ECF; moves across cell membranes by active transport

Chloride – Chief extracellular anion; found in blood, interstitial fluid, and lymph

Bicarbonate – the major chemical base buffer within the body; found in both ECF and ICF

Fluid and Electrolyte Movement

Transportation of materials between the fluid compartments is accomplished through

Osmosis

Diffusion

Active transport

Filtration

Osmosis

Major method of transporting water

Water shifts and thus balance depends on osmosis

Water passes from an area of lesser concentration to one of greater concentration

Osmolarity Concentration of particles in a solution

Osmolarity of plasma (275-310 mOsm/L)

3 types of solutions Isotonic – same osmolarity as plasma Hypotonic – less osmolarity than plasma Hypertonic – greater osmolarity than plasma25 30 35

DiffusionTendency of solutes and gases to move

throughout a solvent

Solute and gases move from an area of greater concentration to an area of lower concentration

O2 and CO2 exchange in the lung’s alveoli and capillaries by diffusion

Active Transport

Requires energy for the movement of substances through a cell membrane

Moves from an area of lesser concentration to an area of higher concentration

Amino acids, glucose, Na+, K+, Ca2+, H, Cl-, PO4- and Mg2+ are believed to use

active transport

Filtration

Moves from an area of high pressure to one of lower pressure

Controls the movement of body fluid between the intravascular and interstitial space through two opposing forces Colloid osmotic pressure (oncotic pressure) Hydrostatic pressure

Filtration PressureDifference between

Colloid osmotic pressure (certain substances which have a high molecular weight hold fluid in the vessels)

example: plasma proteins

AND Hydrostatic pressure (force exerted by a

fluid against the container wall)

example: pressure of plasma and blood cells in the capillaries

Filtration

Facilitates fluid exit from the arterioles (+ pressure) into the interstitial compartment and eventually into the venules (- pressure)

Also involved in the proper functioning of the glomeruli of the kidneys

Body Water Balance

Result of physiologic homeostatic responses to

Fluid gains (oral intake & cellular catabolism)

Fluid losses (urine, evaporation from the skin, vapor loss through the lungs, and feces)

Thirst

Major regulator of intake

Stimulated by receptors in the CNS

Individuals ingest fluids when these receptors are activated

Illness, an altered LOC, or a depressed thirst response (as in the aged) may resultin hypovolemia – Fluid Volume Deficit

Kidneys

Primary organ of fluid balance Excrete end products of cellular

metabolism Eliminate excess fluids

Normally filter 170L of plasma daily in the adult

Kidneys

Must produce a minimum of 500-600 mL of urine to clear the blood of wastes

Usual daily amount of urine production varies from 1-2 liters

Urine Production

Influenced by two hormonal regulatory systems

Antidiuretic hormone (ADH) – stored and released by the pituitary gland

Aldosterone – mineral corticoid secreted by the adrenal cortex

Antidiuretic HormoneMaintains osmotic pressure of the cells

by controlling renal water retention or excretion When osmotic pressure of the ECF is >

cells – ADH secretion is increased, causing renal retention of water

When osmotic pressure of the ECF is < cells – ADH secretion is decreased, causing renal excretion of water

Antidiuretic Hormone

HemorrhageDecreased

cardiac outputTrauma

PainFearSurgerydehydration

Other conditions that can stimulate the secretion of ADH (retention of water)

Antidiuretic Hormone

Morphine

Barbiturates

Nicotine

Some anesthetics

Some tranquilizers

Drugs that increase the secretion of ADH

Antidiuretic HormoneCan be inhibited by

Alcohol

Decreased concentration of ECF

Hypervolemic states

AldosteroneRegulated by renin-angiotension system

When blood flow to the kidney is decreased, the glomerulus of the nephron releases the enzyme renin

Circulating renin converts a plasma protein in the liver into the vasoconstrictor angiotensin I

When angiotensin I enters the lungs, it is converted into antiotensin II

Angiotensin II stimulates the adrenal cortex to increase aldosterone secretion

Leads to ECF volume expansion

Aldosterone

Regulates fluid volume by stimulating the kidneys to reabsorb Na+ and water

Na+ is exchanged for K+ or H+ K+ and H+ are thus affected by

aldosterone

Aldosterone

Secretion is increased in response to

Decreased Na+

Increased extracellular K+

Hypovolemia

Stress states

Assessment of Fluid and Electrolyte Status

Comparison of total I & O Urine volume and

concentration Skin and tongue turgor Degree of moisture in oral

cavity Body weight Thirst Neuromuscular irritability

Tearing and salivation Appearance and

temperature of skin Facial appearance Edema Vital signs Neck and hand vein filling Results of hemodynamic

monitoring

Source: Metheny, N. (2000). Fluid and Electrolyte Balance.

Quick Assessment Guide for Fluid Imbalance

Body System Assessed

Fluid Volume

Excess

Fluid Volume

Deficit

NeurologicChanges in orientation; Confusion

Cardiovascular

Bounding pulse;

Increased pulse rate;

Jugular vein distention;

Overdistended hand veins that are slow to empty (>3s)

Decreased pulse rate;

Decreased BP;

Narrow pulse pressure;

Slow hand filling (>3s)

Respiratory

Moist crackles;

Respiratory rate > 20 bpm;

Dyspnea

Pulmonary edema Lungs clear

Source: Phillips, L. (2001). Manual of I.V. Therapeutics (3rd. Edition), Philadelphia: F. A. Davis



Fluid Volume

Excess

Fluid Volume

Deficit

Integument

Warm, moist skin;

Fingerprinting over sternum

Decreased turgor over sternum and forehead;

Decreased skin temperature

EyesPeriorbital edema (suggests significant fluid retention)

Dry conjunctive;

Sunken eyes;

Decreasing tearing

MouthSticky, dry mucous membranes




Fluid Volume

Excess

Fluid Volume

Deficit

Lips Dry, cracked

TongueExtralongitudinal furrows

Body Weight

Mild: <5% over normal;

Moderate: 5% to 10% over normal;

Severe: >15% over normal

Mild: <5% less than normal;

Moderate: 5% to 10% less than normal;

Severe: >15% less than normal


References

Phillips, L. Manual of I.V. Therapeutics, 3rd edition. Philadelphia, F. A. Davis Co., 2001.

Smith, S., Duell, D., and Martin, B. Clinical Nursing Skills, 5th edition. Upper Saddle River, Prentice-Hall, Inc., 2000.

Taylor, C., Lillis, C., and LeMone, P., Fundamental of Nursing, 4th

edition. Philadelphia, Lippincott Co., 2001.

Documents

Intravenous Therapy Module Fluid and Electrolyte Balance