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 Ions atom or molecule carrying an electric charge Capable of breaking into electrically charged ions when dissolved in a solution Ions with a positive charge Ions with a negative charge Molecules that don’t break down into an electrical charge Liquids that hold a substance in solution water is primary in body Substances that are dissolved in a solution electrolytes and non-electrolytes

Electrolytes Ions Homeostasis — total cations equal to total anions 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 Osmolarity – concentration of particles in a solution. Pulling power Isotonic same concentration as plasma Hypertonic higher concentration of particles than plasma Hypotonic lower concentration of particles than plasma Gases ie. Oxygen and CO2 water bottle Filtration arterioles positive pressure push fluid out to cells. Veins neg pressure pull fluid into vessels. Intake vs Output. Should balance in general. 400cc insensible (nonmeasurable Loss)

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 Sources foods RDA is 2400 mg or 1tsp Lost in urine and feces Regulation ECF concentration 135-145 meqs/L Reabsorbed by kidneys stimulated by aldosterone

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+ Sources/losses RDA 50-100meq needed to maintain balance Foods fruit, meat, dairy, some vegies such as broccoli Eliminated in kidney no means of reabsorption Also found in gastric secretions Regulation sodium pump Aldosterone triggers K+ excretion Normal is 3.5-5 meq/l

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 Source RDA 1gm for adults 1500 mg/day in post menopausal women and persons over 65 More for children per body weight Mild cheese dairy dried beans Use is simulated by vit D promotes absorption and limits excretion Excreted in urine, feces, bile, sweat, digestive secretions Regulation: Parathyroid hormone acts on bnes and teeth to release Ca in blood and kidneys to increase reabsorption Calcitonin hormone releases by the thyroid glands opposite effect of PTH

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 Sources rda is 18-30 meq Vegetables nuts fish whole grains, peas and beans Regulates Absorbed by intestine eliminated by kidneys Lab values 1.3-2.1 meq

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 Source Unknown rda Dairy and meat Regulation, Paired with sodium Excreted and conserved by the kidneys Found in dairy and meat Deficits are associated with potassium deficits Nl 95-105 meq/l

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 Source results of carbon dioxide formation during metabolism Nl levels 25-26 meq Regulated by the kidneys

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 RDA similar to CA++ Found in most foods but mostly in beef, pork, dried peas and beans Metabolized like Ca++ Regulated by Parathyroid hormone Inversely proportional to Ca++ Nl range is 2.5-4.5

OTHER ELECTROLYTES Sulfate Lactic acid Anion ICF Excreted in the kidney Lactic acid 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 Natremia hyper because of osmotic pressure, fluids move from the cells leaving them without enough fluid deficient or excess in ECF Kalemia deficient or excess in ECF hypo muscle weekness and leg cramps Hyper slows conduction cardiac arrest Calcemia hypo takes Ca++ from bones osteomalacia soft bones numbness and tingling muscle cramps tetany Hyper excess in ECF cardiac arrest Magnesium hypo results in hypo kalemia hyper seen in end stage renal failure

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

PROCESS OF MAINTAINING A STABLE STATE UNDER VARIABLE CONDITIONS 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 Table 45-2 page 1280 Kidneys filter170L of plasma qd excrete only 1.5 L urine retain or eliminate electrolytes master chemists of the body. Regulate b/p C-v system pump and carry nutrients Lungs regulate O2 and CO2 levels maintain acid base balance Adrenal secrete aldosterone helps body to retain sodium, chloride and water and excrete potassium. Thyroid throxine increases blood flow in the body to increase glomerular filtration in the kidney Parathyroid hormone regulates ca++ in the ECF GI tract absorbs water and nutrients Nervous system osmoreceptors are sensitive to changes in ECF and send messages to approp spot to maintain homeostasis. Thalmus gland to stimulate thirst, pituitary gland to release or inhibit ADH for fluid regulation.

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 Buffers either bind H+ or release it. Regulate ECF to keep as normal as possible. pH range is 7.35 –7.45 too high or too low = death see figure 45-7 on page 1281 Sodium bicarb/carbonic acid buffers up to 90% most significant in the system. Exist n body in a 20:1 ration of HCO3- tp H2CO3 Phosphate buffer in ICF converts sodium phosphate base to sodium phosphate acid in the kidneys Protein and hemoglobin in plasma can combine with free h+ ions to act as buffer Lungs respirations increase and decrease to retain or eliminate CO2 Kidneys excrete or retain bicarbonate and H+ atoms depending on body needs

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 Lab test are on arterial blood supplies Measured in partial pressure to PaO2 is partial pressure of the arterial oxygen PaCO2 SaO2 or “sats” are the Saturation of O2 in the blood Respiratory disturbances kidney compensate. For metabolic disturbances lungs compensate Page 1284 - 1285

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? Bowel motility will be restored within 24 hours after beginning supplemental K+ ECG will show no cardiac arrhythmias within 48 hours after removing salt substitutes, coffee, tea and other K+ rich foods from the diet ECG will show no cardiac arrhythmias within 24 hours after beginning supplemental K+ Bowel motility will be restored within 24 hours after eliminating salt substitutes, coffee, tea, and other K+ rich foods from the diet Answer.b

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? Constipation related to immobility Pain related to surgical incision Altered thought processes related to cerebral edema, including mental confusion and disorientation Health risk for infection related to inadequate personal hygiene Answer: c.

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? Muscular twitching Distended neck veins Fingerprinting over sternum Nausea and vomiting Answer: b

EXERCISE #4 Pumping uphill would describe which of the following means or transporting materials to and from intercellular compartments? Osmosis Diffusion Filtration Active transport