Fluid & ElectrolyteBasics2013 www.pocketprofnursing.comby Pocket Prof Apps

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HomeostasisBody fluids are in constant motion transporting nutrients, electrolytes, and oxygen to cells while carrying away waste products

Many disease and treatments affect this balance

WaterMore important to life than any other nutrientCarries nutrients and waste productsParticipates in metabolic reactions, food digestionSolvent for minerals, vitamins, glucoseLubricant and cushion for the joints, eyes, spinal cordAids in regulation of body tempMaintains blood volume60% of an adults body weight (more in a child, less in the elderly)Found in foods (but not in alcohol)Daily need is about 2000 mL1 liter of water weighs 1 kg

Fluid Intake and LossIntake sourcesLiquids (1500 mL/day)Solid foods (800 mL/day)Metabolism (300 mL/day)Fluid loss routesKidney (1200-1500 mL/day)Skin (500-600 mL/day)Lungs (400 mL/day)GI tract (100-200 mL/day)Drainage from fistulas/drains, GI suction, salivation

IntakeOutputMeasurableMeasurable Oral fluid, tube feedings Urine Parenteral fluid Emesis Enemas Feces Retained irrigation fluid Drainage from body cavitiesNot MeasurableNot Measurable Solid foods Sweating Metabolism Vaporization through lungs

ElectrolytesChemicals dissolved in the body fluid, distribution affects fluid balanceRegulated by intake, output, acid-base balance, hormones, and cell integritySodium Major extracellular electrolyteControls and regulate water balancePotassiumMajor intracellular electrolyteHelps maintain intracellular water balanceTransmit nerve impulses to muscles and contract skeletal and smooth muscles

F&E LabsSodium (Na) 135-145Determines whether water is retained, excreted, or movedImbalances cause neuro problemsPotassium (K) 3.5-5.0Increased with poor kidney functionDecreased with excessive urination, diarrhea, vomitingImbalances cause cardiac problemsChloride (Cl) 96-106Works with sodium to maintain osmotic pressureIncreased with poor kidney functionDecreased with excessive vomiting or diarrhea

F&E LabsCalcium (Ca) 9.0-10.5Transmission of nerve impulses, heart and muscle contractions, blood clotting, formation of teeth and boneRequires Vit D for absorptionPhosphate (PO4) 3.0-4.5Balance is intertwined with calciumOther testsBUN 6-20Creatinine 0.6-1.3Hematocrit 42-52% (males), 37-47% (females)Total protein, albumin

Lab Normals Magic 4

ElectrolyteRangeMagic 4Potassium3.5 5.54Chloride98 106104Sodium135 - 145140pH7.35 7.457.4pCO235 4540HCO322 2624

FYI Hematocrit normal is 3 times the hemoglobin (10-14 is normal)

Osmolarity and OsmolalityIndicates the water balance of the bodySerum osmo is 285 - 295 mOsm/kgHigh is water deficit (concentrated)Low is water excess (dilute)Urine osmo is 50-1200 mOsm/kg (avg - 500-800 mOsm/kg)Together are used to determine what is causing a sodium imbalance

Distribution of body fluids & ElectrolytesIntracellular (2/3) K+, PO4-

Extracellular (1/3) Na+, Cl-Interstitial (lymph) and transcellular (cerebrospinal, pleural, peritoneal, synovial fluids)Intravascular (blood plasma)

Regulation of Fluid & Electrolyte MovementDiffusionFiltrationOsmosisActive Transport

Regulation of Water Balance

Fluid SpacingFirst spacingNormalSecond spacingEdemaThird spacingAscitesBurn edema

IV FluidsIsotonicNSD5WLRHypertonic3% NSD51/2NSD10WHypotonic1/2NSPlasma Expanders

Gerontologic considerationsPercent of body weight of water is decreasedStructural changes in the kidney and decreased renal blood flowDecreased GFRDecreased creatinine clearanceLoss of ability to concentrate urine and thus conserve waterDecrease in renin and aldosteroneIncrease in ADH and ANPLoss of subcutaneous tissueDecrease in thirst mechanismMusculoskeletal changesMental status changesIncontinence

Assessment ConsiderationsHistory nutrition, I/Os, insensible losses, use of diuretics/laxatives, weight changes, kidney or endocrine disorders, LOC, mental status, depression, eating disorders, alcohol intakePhysical hydration status, skin turgor, mucous membranes, I/OsDx tests electrolyte levels, BUN, glucose, creatinine, pH, bicarb, osmolality, Hgb, Hct, urine dipstick, urine pH, urine specific gravity

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This is a review of the basics of Fluid & Electrolytes. Another video will be available for Fluid & Electrolyte Disorders.

Please note our standard disclaimer in the small print to the left. It basically states that we do everything we can to provide accurate, up-to-date information. However, this video is not designed to replace your professors information, but instead to supplement.*Homeostasis really means constant stability Human body works best when some conditions are kept within a narrow range of normal Iggy book; esp temp, electrolytes, pH, blood volume; our body has mechanisms in place to control homeostasis (ie. sweating and vessel dilation when we are in hot temps)

In terms of fluid volume/composition, homeostasis is very important for the body amount of water or electrolytes can affect the functioning of all cells, tissues, and organs

Body fluids are in constant motion transporting nutrients, electrolytes, and oxygen to cells while carrying away waste products

Imbalances can be caused by illness, altered fluid intake, prolonged vomiting or diarrhea (ie. metastatic breast cancer causes hypercalcemia, chemo is given which causes nausea/vomiting which causes decreased sodium so IV fluids are given but they cause fluid overload)

Goal is for intake and output to be equal (taking into account losses through skin, resp, GI, and renal systems)

*Water is the primary fluid in the body and is more impt to life than any other nutrient, we can survive only a few days without water because most physiologic processes occur only in a watery environment, water delivers electrolytes & nutrients and carries away wastes, its a solvent, a lubricant, & a cushion for our joints and eyes, it helps us regulate body temp and certainly helps us to maintain blood volume

Water balance is affected by age, gender, muscle mass (has more water), fat cells (have no water); 60% of an adults body weight is water, more in a child and less in the elderly Why is this important? These populations are at higher risk of F&E imbalances (elderly have less total body water, obese have less total body water than a lean person of the same weight, women have less total body water than men)

Daily need is 2000-3000 mL (remember needs are increased with conditions like fever, increased metabolism, etc.), found in foods too (not alcohol - acts as a diuretic so it dehydrates you)

1 Liter of water weights 1 kg Why is this important? Sudden change in weight is a good indicator of fluid volume

*Intake is regulated through the thirst drive (triggered by a rising blood osmolarity or a decreasing blood volume) (thirst doesnt work for everyone ie. pt in a coma), we also get fluids from metabolic processes - intake comes as 60% fluid, 30% food, 10% metabolic water

Output kidney loss is closely regulated and adjustable; What is the minimum amt of urine per day to get rid of waste? 400-600 mL; kidneys concentrate or dilute the urine as needed 60% urine, 28% insensible (lungs, skin), 8% sweat, 4% feces

Insensible water loss is important b/c it can be significant (ie. trauma, burns, extreme stress, fever); tachypnea; mechanical ventilation; ulcerative colitis

Think about intake and output and what is (should be) measurable and what isnt gives you a new perspective*Electrolytes are chemicals dissolved in body fluids and their distribution affects fluid balance, they are commonly measured in mEq and include salts, acids, bases, and some proteins have more osmotic power (non-electrolytes do not have an electrical charge and dont dissociate in water and include glucose, lipids, creatinine, and urea)

Normal range of electrolytes is very narrow, even small changes can cause major problems; we get most of our electrolytes from food and the kidneys control most excretion or reabsorption

Sodium Major extracellular electrolyteControls and regulate water balancePotassiumMajor intracellular electrolyteHelps maintain intracellular water balanceTransmit nerve impulses to muscles and contract skeletal and smooth muscles

*Are blood draws from the ECF or the ICF? ECF

Serum electrolytes substances (acids, bases, salts) that circulate in the blood and control things such as muscle contraction, cardiac function; BMP measures 4 common electrolytes and 2 indicators of kidney function Na, K, Cl, HCO3, BUN, creatinine

Chloride exchanges with HCO3, hangs out with Na in the ECF, when there is acidosis it cant be reabsorbed (increases), buffers acid-base imbalances*A change in phosphate levels will cause an equal and opposite change in calcium levels and vice versa

BMP includes glucose, Ca, electrolytes (Na, K, CO2, CL), BUN, creatinine (kidney function)CMP all of the above plus albumin, total protein, liver enzymes (ALP, ALT, AST, bilirubin)*This is just a quick way to try to keep some of these normal ranges straight in your head dont memorize ranges (memorize the middle number)*The terms are often used interchangeably, osmolarity is particles/L and osmolality is particles/kg and is really just a slightly different calculation, you will hear both terms and most labs are reported as osmolality; more importantly pay attention to serum versus urine

Measures the concentration of dissolved particles, mostly determined by sodium, glucose, and BUN - osmo is a solute(Na, K, glucose, urea, etc.) to water ratio

Urine osmo tells us the concentrating ability of the kidneys and if there is a problem with ADH, it is a more accurate calculation of urine concentration than specific gravity

Urine high concentrated - too little water (dehydration) or high levels of salt or sugar or damage to the kidneys (high levels of urine) or DIUrine low dilute - too much water (overhydration) or low level of salt or SIADH

Comparing serum osmo with urine osmo helps determine how well the kidneys are working to remove water and electrolytes from the blood and determines what is really causing a sodium imbalance (fluids or kidneys) normal ratio is 1:3 urine to serum, can also use urine and serum osmo to help determine what is causing a water/sodium imbalance; as one rises or lowers, the other should too

So, lets look at a little more patho to further understand osmo*Water is divided into two spaces ICF (fluid inside the cells) and ECF (fluid outside of the cells)

Cells must maintain a balance of 2/3 body fluids inside the cell (intracellular) and 1/3 body fluid outside the cell, if too much water enters then the cell can rupture, if too much water leaves then the cell dehydrates and collapses; movement of major minerals controls the movement of water (if a negative ion moves in then a positive ion has to move out); as electrolytes move, so does water

ECF if where we do our blood draw and get our lab values this includes the interstitial, transcellular, and intravascular fluids; Interstitial fluids is the fluid between cells (sometimes called the third space) blood, lymph, bone, connective tissue, and transcellular fluids (transcellular is an area enclosed by a membrane (ie. CSF, pleural, peritoneal, joint space), intravascular fluids is the blood plasma within the blood vessels

Osmolality of all body fluids are supposed to be equal so changes in solute concentrations are quickly followed by osmotic changes (usu. in the ECF), also a change in electrolytes will cause acid-base problems If ECF is hypertonic, water moves from ICF to ECF If ECF is hypotonic, water moves from ECF to ICF (into the cells)

*Fluids and electrolytes constantly shift from compartment to compartment to facilitate body processes such as tissue oxygenation, acid-base balance, and urine formation. Because cell membranes separating the body fluid compartments are selectively permeable, water can pass through them easily. However, most ions and molecules pass through them more slowly. Fluids and solutes move across these membranes by four processes: osmosis, diffusion, filtration, and active transport.Filtration differences in water volume, ie. hydrostatic pressure; usu. happens at the tissue capillary level from capillaries to interstitial fluid, ie. edema; water-pushing (hydrostatic) pressure moves fluids thru the membranes (cell & vessel walls)

Diffusion Like melting a lump of sugar into a cup of water, impt in transport of gases; sometimes requires the assistance of a transport system (facilitated diffusion ie. insulin and glucose); similar to filtration but more about movement of particles than movement of fluid (also includes gas transport & electrolytes) Osmosis movement of water (only) between two compartments separated by a semipermeable membrane, we use this when we talk about hypertonic/isotonic/hypotonic fluids, causes cells to shrink or swell; thirst is an example, sweating causes the cells to shrink and makes us thirsty

Active transport molecules have to move against the concentration gradient requiring active energy and a transport system (pump), sodium-potassium pump requiring ATP which move 2 substances at the same time in opposite directions against concentration gradients, requires, used to control cell volume and intracellular concentration

*Fluids maintain blood volume which maintains blood pressure Kidneys are the major regulatory organ of fluid balance, hypothalmus stimulates thirst, endocrine system also helps control F&E balance with the pituitary releasing ADH and the adrenal cortex releasing aldosterone, even the heart gets involved by releasing natriuretic peptides

Kidneys releases renin when the juxtaglomerular cells sense low sodium or low blood volume, this begins the RAAS (renin-angiotension-aldosterone system

Kidneys also have the adrenal cortex which senses low serum osmo or low sodium and releases aldosterone which causes the body to retain sodium in the blood and excrete potassium in the urine; because sodium causes osmotic (water-pulling) pressure water will try to follow sodium; all of this ultimately increases serum osmo (aldosterone protects Na balance by preventing Na loss since water follows Na it also helps with water balance)

Hypothalamus senses high serum osmo or high Na and stimulates thirst (which doesnt help if someone is in a coma) and the release of ADH (vasopressin secreted by the pituitary), ADH works opposite of aldosterone causing the body to retain water and concentrate the urine which decreases serum osmo, it also mildly constricts blood vessels raising the BP (ADH is an example of negative feedback as water level decreases, ADH increases)

Baroreceptors in the right atrium of the heart sense high volume and secretes natriuretic peptides (secreted by the atria and ventricles of the heart - ANP (atria) or BNP (brain from the ventricles of the heart); this stops the RAAS and causes the kidney to stop reabsorbing sodium and increase glomerular filtration which causes increased urine output (with a high sodium in the urine) decreasing blood volume and blood osmolarity, it also dilates the blood vessels

*When capillary or interstitial pressures change, fluid can shift from one compartment to another (albumin causes return of fluid to the vascular compartment from the tissue spaces decreased protein levels cause 3rd spacing)Fluid shifts if capillary or interstitial pressures are altered (ie. Edema, dehydration)First spacing normal distribution of fluid in ICF and ECFSecond spacing abnormal accumulation of interstitial fluid (ie. Edema)Third spacing fluid accumulation in part of body where it is not easily exchanged with ECF (trapped ie. Ascites, sequestration with peritonitis, edema with burns) fluid is trapped and unavailable for use

Plasma to interstitial fluid movement (edema) is caused by:increased venous hydrostatic pressure so nothing can get into the capillary (ie. Fluid overload, heart failure, liver failure, varicose veins, restrictive clothing, tourniquets)Decreased plasma oncotic pressure so fluid cant be drawn back into the capillary (ie. Low protein, renal problems, malnutrition)Increased interstitial oncotic pressure so capillary walls are damaged and proteins accumulate (ie. Trauma, burns, inflammation)

Interstitial fluid to plasma movement is caused by:-Administration of colloids, dextran, mannitol, hypertonic solutions-Increased tissue hydrostatic pressure (ie. SCDs, TED hose)

**Isotonic crystalloids; equal to body fluid, keeps fluid in the intravascular volume without causing a fluid shift from one compartment to the other; usually used for replacement or maintenance fluids (D5W if given rapidly will become hypotonic b/c dextrose is rapidly metabolized into water and carbon dioxide)

Hypertonic thicker than body fluid, shifts fluid into the blood plasma by moving fluid from tissue cells; causes cells to shrink; usually used for replacing electrolytes, hyponatremia (watch for wet breath sounds, sodium levels)

Hypotonic thinner than body fluid, shifts fluid from intravascular to the tissue cells; usually used for hydrating cells (enlarging them) but can deplete the circulatory system

Plasma Expanders - Albumin exerts colloid osmotic or oncotic pressure, which tends to keep fluid in the intravascular compartment by pulling water from the interstitial space back into the capillariesColloids volume expanders, dextran solutions, amino acids, hetastarch, plasmanate Dextran is not a substitute for whole blood because it doesnt have any products that can carry oxygen Hetastarch is isotonic and can decrease platelet and hematocrit counts and is contraindicated in bleeding disorders, CHF, renal dysfunction Plasmanate can be used instead of plasma or albumin to replace body protein Blood and blood products whole blood, packed RBCs, plasma, albumin Lipids fat emulsion solutions, indicated when IV therapy lasts longer than 5 days

% of body weight of water is down to 45-50% (less than normal adult) b/c of decreased muscle mass, puts them at greater risk for dehydration

Kidney changes - Decrease in renin/aldosterone means the body cant retain sodium or excrete potassium, Increased ADH means more water is reabsorbed, Increased ANP means more sodium and water are excreted which lowers blood volume and blood pressure

Loss of subcu tissue means increased loss of moisture through the skin and skin turgor assessment is inaccurate (instead use Is/Os and daily wts)

Musculoskeletal changes may mean an inability to hold a glass

Mental status changes may mean confusion or disorientation

Incontinence may cause older adults to intentionally decrease their fluid intake

*Remember that skin turgor is done on the sternum, forehead, or back of hand, not good assessment for elderly****