intravenous therapy module fluid and electrolyte balance
TRANSCRIPT
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
Quick Assessment Guide for Fluid Imbalance
Body System Assessed
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
Source: Phillips, L. (2001). Manual of I.V. Therapeutics (3rd. Edition), Philadelphia: F. A. Davis
Quick Assessment Guide for Fluid Imbalance
Body System Assessed
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
Source: Phillips, L. (2001). Manual of I.V. Therapeutics (3rd. Edition), Philadelphia: F. A. Davis
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.