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 Compartment Infant % Adult Man % Woman % Elderly Person % Extracellular Intravascular 4 5 Interstitial 25 11 10 15 Intracellular 48 45 35 Total-body water 77 60 50 Source: Taylor, Lillis & LeMone, page 1273.

Electrolytes Electrically 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

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

Electrolytes Major 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

Diffusion Tendency 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 Pressure Difference 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 result in 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 Hormone Maintains 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 Other conditions that can stimulate the secretion of ADH (retention of water) Hemorrhage Decreased cardiac output Trauma Pain Fear Surgery dehydration

Drugs that increase the secretion of ADH Antidiuretic Hormone Drugs that increase the secretion of ADH Morphine Barbiturates Nicotine Some anesthetics Some tranquilizers

Antidiuretic Hormone Can be inhibited by Alcohol Decreased concentration of ECF Hypervolemic states

Aldosterone Regulated 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 Deficit Neurologic Changes 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 Deficit Integument Warm, moist skin; Fingerprinting over sternum Decreased turgor over sternum and forehead; Decreased skin temperature Eyes Periorbital edema (suggests significant fluid retention) Dry conjunctive; Sunken eyes; Decreasing tearing Mouth Sticky, 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 Deficit Lips Dry, cracked Tongue Extralongitudinal 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.