Fluid, Electrolyte, and Acid-Base Balance

Functions of Water in the Body

Transporting nutrients to cells and wastes from cells Transporting hormones, enzymes, blood platelets,

and red and white blood cells Facilitating cellular metabolism and proper cellular

chemical functioning Acting as a solvent for electrolytes and

nonelectrolytes Helping maintain normal body temperature Facilitating digestion and promoting elimination Acting as a tissue lubricant

Two Compartments of Fluid in the Body

Intracellular fluid (ICF) — fluid within cells (70%)

Extracellular fluid (ECF) — fluid outside cells (30%) Includes intravascular and interstitial

fluids

Variations in Fluid Content

Healthy person — total body water is 50% to 60% of body weight

An infant has considerably more body fluid and ECF than an adult More prone to fluid volume deficits

Sex and amount of fat cells affect body water Women and obese people have less body

water

ELECTROLYTES

Terminology Ions Electrolytes Cations Anions Non-electrolytes Solvents Solutes

Electrolytes

Ions Cations — positive charge Anions — negative charge

Homeostasis — total cations equal to total anions

Fluid Balance

Solvents — liquids that hold a substance in solution (water)

Solutes — substances dissolved in a solution (electrolytes and non-electrolytes)

FLUID AND ELECTROLYTE MOVEMENT

Osmosis – Fluid passes from areas of low solute concentration to areas of high solute concentration

Diffusion – tendency of solutes to move freely from areas of high concentration to low concentration (down hill)

Active Transport – requires energy to move through a cell membrane from area of lesser concentration to one of greater concentration

Filtration – passage of fluid through a permeable membrane. Movement is from high to low pressure

COMMON ELECTROLYTES

Sodium (Na++)Functions Regulates volume of body fluids Maintains water balance Regulates ECF Influences ICF Generation and transmission of nerve

impulses Sodium-Potassium pump

POTASSIUM (K+)

Major cation in ICF Reciprocal to sodium Functions

Regulates cellular enzyme activity and water content

Transmission of nerve and muscle impulses Metabolism of proteins and carbohydrates Regulation of acid-base balance by cellular

exchange with H+

CALCIUM (Ca++)

Most abundant electrolyte in body 99% found in bones and teeth Functions Nerve impulse transmission and blood

clotting Catalyst for muscle contraction Thickness and strength of of cell

membranes

MAGNESIUM (Mg++)

Second most important cation in ICF Functions

Metabolism of carbohydrates and proteins Vital enzyme actions Protein and DNA synthesis Maintaining intracellular levels of Potassium Maintain electrical activity in nervous tissue and

muscle tissue membranes

CHLORIDE (Cl-)

Chief extracellular anion Functions

Works with sodium to maintain osmotic pressure of blood

Regulates acid-base balance Buffering action during O2/CO2 exchange Production of Hydrochloric acid in

digestion

BICARBONATE (HCO3-)

Major chemical base buffer Found in ECF and ICF Function

Essential for acid base balance. Works with carbonic acid to make up the body’s acid base buffer system

PHOSPHATE (PO4-)

Major anion in body cells Buffer in ICF and ECF Functions

Maintains body’s acid-base balance Cell division and transmission of heredity Chemical reactions use of Vit B, CHO

metabolism, nerve and muscle action

OTHER ELECTROLYTES

Sulfate Anion ICF Excreted in the kidney

Lactic acid Anion Facilitates diffusion to and from

capillaries

Osmolarity of a solution

Isotonic — same concentration of particles as plasma

Hypertonic — greater concentration of particles than plasma

Hypotonic — lesser concentration of particles than plasma

Source of Fluids for the Body

Ingested liquids Food Metabolism

Fluid Losses

Kidneys — urine Intestinal tract — feces Skin — perspiration Insensible water loss

Fluid Imbalances Involves either volume or distribution of water

or electrolytes Hypovolemia — deficiency in amount of water

and electrolytes in ECF with near normal water/electrolyte proportions

Dehydration — decreased volume of water and electrolyte change

Third-space fluid shift — distributional shift of body fluids into potential body spaces

Fluid Volume Excess Hypervolemia — excessive retention of

water and sodium in ECF Overhydration — above normal amounts

of water in extracellular spaces Edema — excessive ECF accumulates in

tissue spaces Interstitial-to-plasma shift — movement of

fluid from space surrounding cells to blood

Electrolyte Imbalances

Hyponatremia and hypernatremia Hypokalemia and hyperkalemia Hypocalcemia and hypercalcemia Hypomagnesemia and

hypermagnesemia Hypophosphatemia and

hyperphosphatemia

Nursing Assessments

Identify patients at risk for imbalances. Determine a specific imbalance is

present and its severity, etiology, and characteristics.

Determine effectiveness of plan of care.

Parameters of Assessment

Nursing history and physical assessment

Fluid intake and output Daily weights Laboratory studies

Lab Studies to Assess for Imbalances

Complete blood count Serum electrolytes Urine pH and specific gravity Arterial blood gases

Risk Factors for Imbalances

Pathophysiology underlying acute and chronic illnesses

Abnormal losses of body fluids Burns Trauma Therapies that disrupt fluid and

electrolyte balance

Nursing Diagnoses Related to Imbalances

Excess fluid volume Deficient fluid volume Risk for imbalanced fluid volume

Expected Outcomes

Maintain approximate fluid intake and output balance (2500mL intake and output over 3 days)

Maintain urine specific gravity within normal range (1.010 to 1.025)

Practice self-care behaviors to promote balance

Implementing

Dietary modifications Modifications of fluid intake Medication administration IV therapy Blood and blood products replacement TPN

Administering Medications

Mineral-electrolyte preparations Diuretics Intravenous therapy

Intravenous Therapy

Vascular access devices Peripheral venous catheters Midline peripheral catheter Central venous access devices Implanted ports

Vein Site Selection

Accessibility of a vein Condition of vein Type of fluid to be infused Anticipated duration of infusion

HOMEOSTASIS

PROCESS OF MAINTAINING A STABLE STATE UNDER VARIABLE CONDITIONS

MECHANISMS OF HOMEOSTASIS

Kidneys Cardiovascular system Lungs Adrenal Glands Thyroid Gland Parathyroid Gland Gastrointestinal tract Nervous system

Primary Organs of Homeostasis

Kidneys normally filter 170 L plasma, excrete 1.5 L urine.

Cardiovascular system pumps and carries nutrients and water in body.

Lungs regulate oxygen and carbon dioxide levels of blood.

Primary Organs of Homeostasis, continued

Adrenal glands help body conserve sodium, save chloride and water, and excrete potassium.

Thyroid gland increases blood flow in body and increases renal circulation.

ACID – BASE BALANCE

Acid contains hydrogen atoms that can be released Acidosis too many circulating H+ ions

Base accepts hydrogen atoms Alkalosis not enough H+ ions in the ECF

pH is the unit of measure used to describe acid base balance

Buffer prevents ECF from becoming too acidic or too alkaline

BUFFER SYSTEMS

Carbonic Acid-Sodium Bicarbonate System

Phosphate Buffer System Protein Buffer System

IMBALANCE IN ACID – BASE BALANCE

Respiratory Alkalosis Deficit in carbonic acid in the ECF

Respiratory Acidosis Excess in carbonic acid in the ECF

Metabolic Alkalosis Excess of bicarbonate in the ECF

Metabolic Acidosis Deficit of bicarbonate in the ECF

EXERCISE #1 For the patient with hyperkalemia related to

decreased renal excretion secondary to potassium conserving diuretic therapy” an appropriate expected outcome would be which of the following?

a) Bowel motility will be restored within 24 hours after beginning supplemental K+

b) ECG will show no cardiac arrhythmias within 48 hours after removing salt substitutes, coffee, tea and other K+ rich foods from the diet

c) ECG will show no cardiac arrhythmias within 24 hours after beginning supplemental K+

d) Bowel motility will be restored within 24 hours after eliminating salt substitutes, coffee, tea, and other K+ rich foods from the diet

EXERCISE #2

Which of the following nursing diagnoses would you expect to find based on the effects of fluid and electrolyte imbalance on human functioning?

a) Constipation related to immobilityb) Pain related to surgical incisionc) Altered thought processes related to cerebral

edema, including mental confusion and disorientation

d) Health risk for infection related to inadequate personal hygiene

EXERCISE #3

A nurse who diagnoses a patient as having “fluid volume excess” related to compromised regulatory mechanisms (kidneys) may have been alerted by which of the following symptoms?

a) Muscular twitching

b) Distended neck veins

c) Fingerprinting over sternum

d) Nausea and vomiting

EXERCISE #4

Pumping uphill would describe which of the following means or transporting materials to and from intercellular compartments?

a) Osmosis

b) Diffusion

c) Filtration

d) Active transport