Chapter 39: Fluid, Electrolyte, & Acid-Base Balance

Interstitial fluids

fluid that surrounds tissue cells & includes lymph

Nursing Diagnoses Related to Imbalances

• Excess fluid volume • Deficient fluid volume • Risk for imbalanced fluid volum

Total Body Fluid Representing

50%-60% of Body Weight of Normal Adult= Cell Fluid: 35-40% of body weight Extracellular Fluid: 15-20% of body weight Plasma: 5% of body weight Interstitial Fluid: 10-15% of body weight

Transporting Body Fluids

Cell membranes are semipermeable, allowing some, but not all, solutes to pass through the cell membranes. • Osmosis: water (the solvent)passes from an area of lesser solute concentration to greater concentration until equilibrium is established • Diffusion: tendency of solutes to move freely throughout a solvent ("downhill") • Active transport: requires energy for movement of substances through the cell membrane from the lesser solute concentration to the higher solute concentration ("uphill") • Filtration: passage of fluid through a permeable membrane from the area of higher to lower pressure

Electrolytes

Ions : An atom or molecule carrying an electrical charge - Cations: positive charge - • Major cations in body fluid: Sodium, Potassium, Calcium, Hydrogen, and Magnesium ions - Anions: negative charge - • Major anions in body fluid: Chloride, Bicarbonate, and Phosphate. - Nonelectrolytes - molecules in the body that remain intact without a charge • Urea and Glucose • Homeostasis: total cations equal to total anions Measured in terms of their chemical combining power, or chemical activity. - Milliequivalent (mEq) unit of measure that describes the chemical activity of electrolytes. - When electrolytes are not in balance, the person is at risk for alterations in health.

3rd usually (Compartments of Fluid in the Body)

minor compartment is the Transcellular fluid - Includes Cerebrospinal, Pericardial, Synovial, Intra Ocular, and Pleural fluids, Sweat and Digestive secretions

Kidneys

regulate extracellular fluid (ECF)

Water % of Body Weight (MAN)

Extracellular Intravascular 4 Interstitial 11 Intracellular 45 Total Body Water 60

Water % of Body Weight (FEMALE)

Extracellular Intravascular 5 Interstitial 10 Intracellular 35 Total Body Water 50

Water % of Body Weight (ELDERLY PERSON)

Extracellular Intravascular 5 Interstitial 15 Intracellular 25 Total Body Water 45

Water % of Body Weight (INFANT)

Extracellular Intravascular 4 Interstitial 25 Intracellular 48 Total Body Water 77

Human Body Fluid Lost

Fluid lost from body is through - Sensible • Can be measured • Example: urination, defecation, wounds - Insensible loss • Can not be measured or seen • Example: evaporation through skin, lungs - Fluid output are 2,500 to 2,900 ml/day

Potassium (K+): major cation of ICF; the normal serum concentration of potassium: 3.5-5.0 MEq/L

Functions: controls intracellular osmolality; Regulator of cellular enzyme activity; role in the transmission of electrical impulses in nerve, heart, skeletal, intestinal, & lung tissue; protein and carbohydrate metabolism; and cellular building; regulation of acid-base balance by cellular exchange with H+ Sources & Losses: adequate quantities via a well-balanced diet, leading food sources: fruits and vegetable, dried peas and beans, whole grains, milk, meats. Lost via stool, sweat, emesis. GI secretions contain potassium in large quantities, so can be lost through vomitus. Regulation: regulated by aldosterone. Eliminated by the kidneys (no effective method of conserving potassium). Additional regulation via transcellular shift between the ICF and ECF compartments

Chloride (Cl-) major ECF anion; normal serum level of chloride: 97-107 mEq/L

Functions: major component of interstital and lymph fluid; gastric and pancreatic juices, sweat, bile, and saliva. Acts with sodium to maintain the osmotic pressure. Role in the body's acid-base balance; combines with hydrogen ions to produce hydrochloric acid Sources & Losses: enters body via GI tract. almost all chloride in diet comes from salt. found in foods high in sodium, processed foods. Regulation: normally paired with sodium; excreted and conserved with sodium by the kidneys. regulated by aldosterone alongside sodium. low ppotassium level leads to low chloride level.

Bicarbonate (HCO3-) an anion thath is the major chemical base buffer within the body; found in bith ECF and ICF; normal serum bicarbonate level: 25-29 mEq/L

Functions: regulates acid-base balance Sources & Losses: losses possible via diarrhea, diuretics, and early renal insufficiency. excess possible via overingestion of acid nertalizers, such as sodium bicarbonate. Regulation: bicarbonate levels regulated primarily by the kidneys. bicarb readily available as a result of co2 formation during metabolism

Sodium (Na+): cheif electrolyte of ECF; the normal of serum concentration of sodium: 135-145 mEq/L

Functions: regulates extracellular fluid volume; Na+ loss or gain accompanied by a loss or gain of water, affects serum osmolality, role in muscle contraction & transmission of nerve impulses, Regulation of acid-base balance as sodium bicarbonate. Sources & Losses: noramlly enters the body through the gastrointestinal tract from dietary sources, such as salt added to processed foods, sodium preservatives added to processed foods. Lost from gastrointestinal tract, kidneys, and skin. Regulation: transported out of the cell by the sodium-potassium pump, regulated by renin-angiotensinaldosterone system, eliminated and re-absorption regulated by the kidneys, sodium concentration affected by salt and water intake.

Phosphate (PO4-) major ICF anion; a buffer anion in both ICF and ECF; normal serum phosphate level: 2.5-4.5 mg/dL

Functions: role in acid-base balance as a hydrogen buffer. promotes energy storage; carb, protein, and fat metabolism. bone and teeth formation. regulation of hormone and coenzyme activity. role in muscle and red blood cell function. Sources & Losses: enters body via GI tract. sources include all animal products (meat, poultry, eggs, milk, bread, ready-to-eat cereal) Absorption is diminished by concurrent ingestion of calcium, magnesium, and albumin Regulation: eliminated by kidney. regulation by parathyroid hormone and by activated vitamin D. phosphate and calcium are inversely proportional; an increase in one results in a decrease in the other.

Calcium (Ca2+) most abundant electrolyte in the body; 99% of body calcium is stored in bone; 1% inside cells; 0.1 % in ECF; normal total serum calcium level ; 8.6-10.2 mg/dL; normal ionized serum calcium level: 4.5-5.1 mg/gL

Functions: role in blood coagulation and in transmission of nerve impulses. Helps regulate muscle contraction and relaxation. Activates enzymes that stimulate essential chemical reactions in the body. Major component of bones and teeth. Sources & Losses: absorbed from foods in the presence of noraml gastric acidity and vitamin D. Lost via feces and urine. Sources include milk, milk products, and cheese; dried beans; fortified orange juice; green, leafy vegetables; small fish with bones; and dried peas and beans. Regulation: primarily excreted by GI tract; lesser extent by kidneys. Regulated by parathyroid hormone and calcitonin. high serum phospate results in decreased serum calcium level; low serum phosphate leads to increased serum calcium.

Magnesium (Mg2+) second most abundant ICF cation after potassium; normal serum concentration of magnesium: 1.3-2.3 mEq/L

Functions:metabolism of carbs and proteins. activator for many intercellular enzymes. role in neuromuscular function. Acts on cardiovascular system, producing vasodilation. Sources & Losses: enters the body via GI tract. magnesium found in green, leafy vegetables; nuts; seafood; whole grains; dried peas and beans; cocoa. Lost via urine with use of loop diuretics. Regulation: eliminated by kidneys. regulated by parathyroid hormone.

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 • Gender and amount of fat cells affect body water; women and obese people have less body water - Capillary walls and cell membranes separate the intracellular and extracellular compartments The combined increase of fat and loss of muscle results in reduced total body water; after the age of 60, total was is about 45% of body weight.

Human Body Fluid Intake

Obtain water from: - Ingested liquids (provides the largest amount normally taken into the body), food, and by products of metabolism - Fluid intake regulated primarily by the thirst mechanism • Thirst control center is located within hypothalamus and is simulated by intracellular dehydration

Body fluids

Primary is water-MOST important nutrient of Life

Major Electrolytes/Chief Function

Sodium: controls and regulates volume of body fluids • Potassium: chief regulator of cellular enzyme activity and water content • Calcium: nerve impulse, blood clotting, muscle contraction, B12 absorption • Magnesium: metabolism of carbohydrates and proteins, vital actions involving enzymes • Chloride: maintains osmotic pressure in blood, produces hydrochloric acid • Bicarbonate: body's primary buffer system • Phosphate: involved in important chemical reactions in the body, cell division, and hereditary traits

Fluid Balance

Solvents: liquids that hold a substance in solution - Example: Water is the primary solvent in the body. • Solutes: substances dissolved in a solution - Example: Electrolytes and nonelectrolytes • The body produces balance by shifting fluids and solutes between the ECF and the ICF. • Mechanisms responsible for regulating this shift of fluids and transporting materials to and from intracellular compartments include organs and body systems, osmosis, diffusion, active transport, and capillary filtration.

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

Principles of Fluids and Electrolytes

Vital to Life Involved in almost every cellular reaction & function Chemical reactions that occur depend on balance of acid and base

Extracellular fluid (ECF)(Compartments of Fluid in the Body)

fluid outside cells (30%) of total body water or 20% of the adult's body weight. Includes intravascular and interstitial fluids

Intracellular fluid (ICF) (Compartments of Fluid in the Body)

fluid within cells (70%) of total body water or 40% of the adult's body weight

Intravascular fluid (plasma)

the liquid component of the blood (fluid found within the vascular system)

Vein Site Selection

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

Acid-Base Balance (pH)

• Acid: substance containing hydrogen ions that can be liberated or released • Base: substance that can trap hydrogen ions

Nursing Process for Fluid, Electrolyte, and Acid-Base Balance

• Assessing • Diagnosing • Outcome Identification and Planning • Implementing • Evaluating - Read Chapter 39 pages 1484-1517

Major Homeostatic Regulators of Hydrogen Ions

• Buffer systems - Carbonic acid-sodium bicarbonate - Phosphate - Protein • Respiratory mechanisms • Renal mechanisms

Lab Studies to Assess for Imbalances

• Complete blood count • Serum electrolytes, blood urea nitrogen, and creatinine levels • Urine pH and specific gravity • Arterial blood gases

Implementing

• Dietary modifications • Modifications of fluid intake • Medication administration • IV therapy • Blood and blood products replacement • TPN • Allaying patient anxiety as needed • Appropriate patient and family teaching

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 • Hypochloremia and hyperchloremia

Nursing Assessments

• Identify patients at risk for imbalances. • Determine that a specific imbalance is present and its severity, etiology, and characteristics. • Determine the plan of care, nursing diagnoses or collaborative problems. • Identify specific outcomes and associated interventions. • Determine effectiveness of the plan of care.

Fluid Imbalances

• Involve 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

Primary Organs of Homeostasis

• Kidneys normally filter 170 L of plasma and excrete 15 L of urine. • The cardiovascular system pumps and carries nutrients and water in body. • Lungs regulate oxygen and carbon dioxide levels of the blood. • Adrenal glands help the body conserve sodium, save chloride and water, and excrete potassium. • The pituitary gland stores and releases ADH.• The thyroid gland increases the blood flow in the body and increases renal circulation. • The nervous system inhibits and stimulates mechanisms influencing fluid balance. • Parathyroid glands regulate the level of calcium in ECF. • The GI tract absorbs water and nutrients that enter the body through this route.

Expected Outcomes

• Maintain approximate fluid intake and output balance (2,500-mL intake and output over 3 days). • Maintain urine specific gravity within normal range (1,010-1,025). • Practice self-care behaviors to promote balance.

Administering Medications

• Mineral-electrolyte preparations • Diuretics • Intravenous therapy

Parameters of Assessment

• Nursing history and physical assessment • Fluid intake and output • Daily weights • Laboratory studies

Acid-Base Imbalances

• Occur when carbonic acid or bicarbonate levels become disproportionate - Respiratory acidosis: primary excess of carbonic acid in ECF - Respiratory alkalosis: primary deficit of carbonic acid in ECF - Metabolic acidosis: proportionate deficit of bicarbonate in ECF - Metabolic alkalosis: primary excess of bicarbonate in ECF

Osmolarity of a Solution

• Osmosis • The concentration of particle in a solution, or its pulling power, is referred to as the osmolarity of a solution. - Isotonic: same concentration of particles as plasma (between 275 and 295 mOsm/L) - Hypertonic: greater concentration of particles than plasma (greater than 295 mOsm/L) • Water moves out of the cell and drawn into the intravascular compartment, causing the cell to shrink - Hypotonic: lesser concentration of particles than plasma (less than 275 mOsm/L) • Water moves out of the intravascular space and into intracellular fluid, causing cells to swell and possibly burst.

Filtration

• Passage of fluid through a permeable membrane - Fluid move from an area of high pressure to one of lower pressure. - Capillary filtration - results from the force of blood "pushing" against the walls of the capillaries. • Hydrostatic pressure is the "pushing" force. - Reabsorption is the process that acts to prevent too much fluid from leaving the capillaries no matter how high the hydrostatic pressure • Plasma proteins, particularly albumin, facilitate this reabsorption process by pulling the fluid back into the capillaries ... • Colloid osmotic pressure the pulling force/oncotic pressure - Filtration pressure is the difference between colloid osmotic pressure and blood hydrostatic pressure.

Risk Factors for Imbalances

• Pathophysiology underlying acute and chronic illnesses • Abnormal losses of body fluids • Burns • Trauma • Surgery • Therapies that disrupt fluid and electrolyte balance

Active Transport

• The process that requires energy for the movement of substance through a cell membrane, against the concentration gradient - From an area of lesser solute concentration to an area of higher solute concentration. - Adenosine triphosphate (ATP) stored in the cell, supplies energy for solute movement in and out of the cell. • Active transport is affected by characteristics of the cell membrane, specific enzymes, and concentrations of ions. * Pump Mechanism = pumping uphill

Diffusion

• The tendency of solutes to move freely throughout a solvent. - Solute moves from an area of higher concentration to an area of lower concentration - downhill ; until equilibrium is established - Gases move by diffusion • Example: Oxygen and carbon dioxide exchange in the lungs' alveoli and capillaries

Administering Blood and Blood Products

• Typing and cross-matching • A, B, AB, and O type blood • Rh factor • Selecting blood donors • Initiating transfusion • Transfusion reactions - See Table 39-13 **** - **See Reaction/Signs and Symptoms/ NURSING ACTIVITY

Intravenous Therapy

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