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

Sources Losses

Water 1500 ml Urine 1500 ml

Food 800 ml Stool 200 ml

Oxidation 300 ml Skin 500 ml

Resp. Tract 400 ml

Total 2600 ml Total 2600 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

INTRACELLULAR EXTRACELLULAR

POTASSIUM SODIUM

MAGNESIUM CHLORIDE

PHOSPHOROUS BICARBONATE

Normal Laboratory Values

Sodium 135-145 meq/LPotassium 3.5-5.0 meq/LChloride 95-105 meq/LBicarbonate 22-28 meq/LCalcium 9-11 mg/dLPhosphate 3.2-4.3 mg/dLGlucose 70-110 mg/dLBUN 8-18 mg/dLCreatinine 0.6-1.2 mg/dLOsmolality (P) 280-295 mOsm/kgOsmolality (U) 50-1200 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.

7.35 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 (3.5-5.0 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