Fluid, Electrolyte, and Acid-Base Balance

Physiology of Fluid and Acid-Base Balance The body normally maintains a balance between the amount of fluid taken in and the amount excreted. Homeostasis is the maintenance of this balance in response to changes in the internal and external environments.

Physiology of Fluid and Acid-Base Balance Fluid Compartments Cells Blood vessels Tissue space (interstitial space) Space between the cells and blood vessels

Fluid Compartments Two Types of Body Fluids Intracellular fluid (ICF) is fluid within the cell. Extracellar fluid (ECF) Intravascular fluid (within blood vessels) Interstitial fluid (between cells; fluid that surrounds cells)

Solute: Substance dissolved in a solution. Solvent: Liquid that contains a substance in solution. Permeability: Capability of a substance, molecule, or ion to move across a membrane. Cells have semi-permeable membranes that allow fluid and solutes to pass into and out of the cell. Blood vessels have semi-permeable membranes that bathe and feed the cells.

Body Water Distribution Water represents 45% to 75% of the body’s total weight. About two-thirds of the body fluid is intracellular. One-third of body fluid is extracellular. One-fourth of this fluid is intravascular. Three-fourths is interstitial fluid.

Functions of Body Water Water acts as a solvent for essential nutrients. Water transports nutrients and oxygen from the blood to the cells. Water removes waste material and other substances from the cells and returns it to the blood for excretion by the body. Gives shape and form to cells. Regulates body temperature. Acts as a lubricant in joints. Cushions body organs.

FLUID REQUIREMENTS SourcesLosses Water1500 mlUrine1500 ml Food800 mlStool200 ml Oxidation300 mlSkin500 ml Resp. Tract400 ml Total2600 mlTotal2600 ml

Electrolytes Compounds that, when dissolved in water or another solvent, form or dissociate into ions Sodium (Na+) Potassium (K+) Calcium (Ca2+) Magnesium (Mg2+)

ELECTROLYTES IN BODY FLUID COMPARTMENTS INTRACELLULAREXTRACELLULAR POTASSIUMSODIUM MAGNESIUMCHLORIDE PHOSPHOROUSBICARBONATE

Normal Laboratory Values Sodium meq/L Potassium meq/L Chloride meq/L Bicarbonate22-28 meq/L Calcium9-11 mg/dL Phosphate mg/dL Glucose mg/dL BUN8-18 mg/dL Creatinine mg/dL Osmolality (P) mOsm/kg Osmolality (U) mOsm/kg

Electrolytes Promote normal neuromuscular excitability. Maintain body fluid osmolarity. Regulate acid base balance. Distribute body fluids between fluid compartments.

Extracellular fluid contains the largest quantities of sodium, chloride, and bicarbonate ions, and small quantities of potassium and calcium. Intracellular fluid contains only small quantities of sodium and chloride, almost no calcium ions, and large quantities of potassium.

Movement of Body Fluids Physiological forces affect the transport of molecules of water, foods, gases, wastes, and ions. Maintain a balance between extracellular and intracellular fluid compartments. Diffusion Osmosis Active Transport Hydrostatic Pressure Filtration Colloid Osmotic Pressure

Diffusion – movement of particles down a concentration gradient. Osmosis – diffusion of water across a selectively permeable membrane Active transport – movement of particles up a concentration gradient ; requires energy

Regulators of Fluid Balance Fluid and Food Intake and Loss Skin Lungs Gastrointestinal Tract Kidneys

Acid-Base Balance Acid-base balance refers to the homeostasis of the hydrogen ion concentration in extracellular fluid. An acid is a substance that donates hydrogen ions. A base is a substance that accepts hydrogen ions.

The pH symbol indicates the hydrogen ion concentration of body fluids to 7.45 is the normal pH range of extracellular fluid. Acidity increases as the pH decreases. Alkalinity decreases as the pH increases. Buffer Systems Two or more chemical compounds that prevent marked changes in hydrogen ion concentration when either an acid or a base is added to a solution

Respiratory Regulation of Carbon Dioxide in Extracellular Fluid Increased carbon dioxide levels in extracellular fluid increase rate and depth of respirations so that more carbon dioxide is exhaled. Decreased carbon dioxide levels depress respirations to maintain carbon dioxide.

Renal Control of Hydrogen Ion Concentration The kidneys control extracellular fluid pH by removing hydrogen or bicarbonate ions from body fluids. When the kidneys excrete more bicarbonate ions, the urine becomes more alkaline. When the kidneys excrete more hydrogen ions, the urine becomes more acidic.

Factors Affecting Fluid and Electrolyte Balance Age Adult, 60% water Child, 60% to 77% water Infant, 77% water Embryo, 97% water In the elderly, body water diminishes because of tissue loss.

Factors Affecting Fluid and Electrolyte Balance Lifestyle Stress Exercise Warm or humid environment Diet

Disturbances in Electrolyte and Acid-Base Balance In illness, one or more of the homeostatic regulating mechanisms may be affected, or the imbalance may become too great for the body to correct without treatment. Sodium is the primary determinant of extracellular fluid concentration. Alterations in sodium concentration can produce profound effects on the central nervous system and circulating blood volume.

Electrolyte Disturbances Hyponatremia is a deficit in the extracellular level of sodium. The ratio of water to sodium is too high (a hypo-osmolar state). Water moves out of the vascular space into the interstitial space, causing edema.

Electrolyte Disturbances Hypernatremia is an excess of sodium in the extracellular fluid. The ratio of sodium to water is too high (hyperosmolar state). Extracellular osmotic pressure pulls fluid out of the cells into the extracellular space, causing edema.

Electrolyte Disturbances Potassium The normal range of extracellular potassium is narrow ( mEq/L). Small deviations cause serious or life- threatening effects on physiologic functions. A reciprocal relationship exists between sodium and potassium.

Electrolyte Disturbances Hypokalemia is a decrease in the extracellular level of potassium. Gastrointestinal disturbances and the use of potassium wasting diuretics, laxatives, corticosteroids, and antibiotics place the client at risk for hypokalemia.

Electrolyte Disturbances Hyperkalemia is an increase in the extracellular level of potassium. Three major drug groups may cause hyperkalemia. Potassium-sparing diuretics Central nervous system agents Oral and intravenous replacement potassium salts

Electrolyte Disturbances Calcium Essential for normal bone and teeth formation Critical factor in normal blood clotting Maintenance of normal nerve and muscle excitability Hypocalcemia is a decrease in the extracellular level of calcium. Hypercalcemia is an increase in the extracellular level of calcium.

Electrolyte Disturbances Magnesium Coenzyme in the metabolism of carbohydrates and proteins Mediator in neuromuscular activity Hypomagnesemia is a decrease in the extracellular level of magnesium and usually occurs with hypokalemia and hypocalcemia. Hypermagnesemia refers to an increase in the extracellular level of magnesium.

Electrolyte Disturbances Phosphate Main intracellular anion Appears as phosphorus in the serum. Similar to calcium in that Vitamin D is needed for its reabsorption from the renal tubules. Hypophosphatemia is a decreased extracellular level of phosphorus. Hyperphosphatemia is an increased extracellular level of phosphorus.

Electrolyte Disturbances Chloride and water move in the same direction as sodium ions. A loss of chloride can be compensated for by an increase in bicarbonate. Hypochloremia is a decrease in the extracellular level of chloride. Gastrointestinal tract losses because of the acid content of gastric juices (hydrogen chloride), placing the client at risk for metabolic alkalosis Hyperchloremia usually occurs with dehydration, hypernatremia, and metabolic acidosis.

Acid-Base Disturbances Laboratory Data Arterial blood gases Blood pH Bicarbonate ion concentration Sodium, potassium, chloride levels Respiratory Acidosis (Carbonic Acid Excess) Respiratory Alkalosis (Carbonic Acid Deficit) Metabolic Acidosis (Bicarbonate Deficit) Metabolic Alkalosis (Bicarbonate Excess)

Assessment Health History Clients receiving certain treatments, such as medications and IV therapy Data specific to fluids Physical Examination Daily weight Vital signs Intake and output Edema Skin turgor

Assessment Physical Examination Buccal (oral) cavity Eyes Jugular and hand veins Neuromuscular system Diagnostic and Laboratory Data Hemoglobin and hematocrit indices With severe dehydration and hypovolemic shock, the hematocrit is increased. Overhydration reduces the hematocrit by dilution.

Laboratory Data Osmolality Measurement of the total concentration of dissolved particles (solutes) per kilogram of water Serum osmolality Urine osmolality Diagnostic and Laboratory Data Urine pH Serum albumin

Deficient Knowledge Dehydration is one of the most common and most serious fluid balances. Information obtained from a client’s health history may indicate the client’s level of understanding and perception of alterations in fluid, electrolyte and acid-base balance.

Planning and Outcome Identification Expected outcomes for clients with fluid imbalances include outcomes relative to interventions. Achievement of the goals and the client’s expected outcomes indicates resolution of the problem.

Implementation Monitor Daily Weight Measure Vital Signs Measure Intake and Output Provide Oral Hygiene Initiate Oral Fluid Therapy Nothing by Mouth Restricted Fluids Forced Fluids Maintain Tube Feedings Monitor Intravenous Therapy

Implementation Monitor Intravenous Therapy Administration of fluids, electrolytes, nutrients, or medications by the venous route when fluid losses are severe or the client cannot tolerate oral or tube feedings

Intravenous Therapy Parenteral Fluids Hypotonic Isotonic Hypertonic Equipment Administration Set Health Hazard Intravenous Filters

Intravenous Therapy Equipment Needles and venous peripheral-short catheters Butterfly needles Intracath Angiocatheter Peripheral intravenous (PI) Heparin locks (intermittent venous locks) Equipment Needle-Free System Vascular Access Devices (VAD) Various catheters, cannulas, infusion ports that allow for long-term IV therapy or repeated access to the central venous system

Intravenous Therapy Preparing an Intravenous Solution Initiating IV therapy Vein finder Administering IV Therapy Flushing Regulating IV solution flow rates Calculation of flow rates Flow Control Devices Manual flow-control devices Electronic infusion devices

Intravenous Therapy Managing IV Therapy Hypervolemia Infiltration Phlebitis Intravenous dressing change

Intravenous Therapy Discontinuation of Intravenous Therapy Blood Transfusion Whole blood and blood products Initial assessment and preparation Administering whole blood or a blood component Safety measures

Complementary Therapy Herbs and certain foods Naturopathic health care practitioners Considerations for using complementary therapies with traditional medications