Fluid & Electrolyte

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Fluid & Electrolyte

Study Guide

Fundamentals of Nursing

Fluid, electrolyte, and acid-base balances are necessary to maintain health and function in all body systems. These balances are maintained by the intake and output of water and electrolytes and regulation by the renal and pulmonary systems. Imbalances may result from many factors, including illnesses, altered fluid intake, or prolonged episodes of vomiting or diarrhea. Acid-base balance is necessary for many physiological processes, and imbalances can alter respiration, metabolism, and the function of the central nervous system.

Homeostasis – state of equilibrium naturally maintained by the adaptive responses of the body, many disease and treatments can affect fluid and electrolytes (i.e metastatic breast cancer)

Water – essential nutrient, more important to life than any other nutrient, body needs more water each day than any other nutrient, can survive only a few days without water, minerals help the body maintain an appropriate balance and distribution of water, 60% of an adult’s body weight, more in a child; Water sources – water itself and other beverages, fruits and veggies have up to 90% water, meats and cheeses contain 50%, water is also generated during metabolism, caffeine can be counted towards total intake, alcohol acts as a diuretic and dehydrates you; daily water need – 2000 ml/day average, 15 ml/pound, increase by 15% if pt has fever; serum osmolality tells us the water balance of the body (275 – 295) (dilute – concentrated); infants and elderly are a higher risk of fluid problems

Carries nutrients and waste products

Maintains the structure of large molecules

Participates in metabolic reactions and food digestion

Serves as a solvent for minerals, vitamins, amino acids, glucose

Acts as a lubricant and cushion around joints, eyes, spinal cord

Aids in regulation of normal body temp

Maintains blood volume

Osmolality – tells us the water balance of the body and concentration of body fluid, normal for serum (different for urine) is 275 – 295, if less is hypoosmolar or dilute (result of excess water intake or fluid overload caused by an inability to excrete excess water, if more is hyperosmolar or concentrated (caused by severe diarrhea, increased salt and solutes (protein) intake, inadequate water intake, diabetes, ketoacidosis or sweating)


Cations – positively charged (remember t in positive and cation), transmit nerve impulses to muscles and contract skeletal and smooth muscles (K, Na, Ca, Mg)

Anions – negatively charged (remember n in negative and anion), attached to cations (CL, HCO3, PO4, SO4)

Always have to be kept in balance, if a positive leaves, then another positive must come in or a negative must also leave

Distribution of Body Fluids/Electrolytes

Intracellular – most prevalent electrolytes are K+, PO4 -

Extracellular – most prevalent electrolytes are Na+, Cl-

Interstitial (lymph)

Intravascular (blood plasma)

Transcellular (cerebrospinal, pleural, peritoneal, synovial fluids)

Mechanisms Controlling Fluid & Electrolyte Movement

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.

Osmosis –

Diffusion –

Filtration –

Active transport -

Fluid Spacing

Fluid shifts if capillary or interstitial pressures are altered (ie. edema, dehydration, see pg 335 in Lewis)

First spacing – normal distribution of fluid in ICF and ECF

Second 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)

Regulation of Water Balance

Kidneys are the major regulatory organ of fluid balance, most reliable measure of fluid volume status is daily weights, another important reliable measurement is strict Is & Os done by measuring and recording all liquid intake and output during a 24 hour period – intake includes all liquids by mouth, IV, feeding tube and blood; output includes all urine, vomitus, drainage from wounds or other tubes, diarrhea, gastric suctions)

Fluid Intake (Hypothalmus) - when the blood becomes concentrated (having lost water but not the dissolved substances in it – ie. eating something salty) the mouth gets dry and the hypothalamus initiates drinking behavior, but thirst lags behind the body’s need; can also be stimulated with hypovolemia from excessive vomiting or hemorrhage, thirst is decreased in the elderly

Hormonal Control (Pituitary) – releases ADH which causes the body to retain water; (also called vasopressin) whenever BP or blood volume falls too low or extracellular fluid becomes too concentrated they hypothalamus signals the pituitary gland to release ADH, this is a water conserving hormone that stimulates the kidneys to reabsorb water, so the more water you need the less your kidneys excrete decreasing urine output temporarily which also triggers thirst; stress, nausea, nicotine and morphine can also stimulate ADH release (SIADH causing the kidneys to reabsorb water and not excrete it in the urine) (Fig 16-10, pg 336, Lewis)

Hormonal Control (Adrenal Cortex) – releases aldosterone which causes the body to retain sodium and excrete potassium, when sodium is reabsorbed water follows

Hormonal Control (Kidney) - primary organ for regulating fluid and electrolyte balance by adjusting urine volume and urinary excretion of electrolytes, renin is released causing the body to retain sodium; cells in the kidney release renin in response to low blood pressure causing the kidneys to reabsorb sodium, sodium reabsorption is always accompanied by water retention which restores blood volume and BP, also causes production of angiotensin which constricts blood vessel and raises BP, renal function is decreased in the elderly leading to increased risk of F&E problems (ie. can’t concentrate urine)

Regulation of Fluid Output

Cells – must maintain a balance of 2/3 body fluids inside the cells and 1/3 body fluids outside cells, if too much water enters then the cell can rupture, if too much water leaves cells can dehydrate and collapse; to control the movement of water, the cells direct the movement of the major minerals

If an anion enters the fluid, a cation must accompany it or another anion must leave so that electrical neutrality is maintained, it’s a good bet that whenever sodium and potassium ions are moving, they are going in opposite directions; everywhere sodium goes, water follows

Electrolytes attract water, some electrolytes reside outside cells (sodium, chloride) and some inside cells (K, Mg, PO4, SO4), cell membranes are selectively permeable (they allow passage of some molecules but not others), whenever electrolytes move across the membrane water follows, proteins attract water and help to regulate fluid movement, regulation occurs mainly in the GI tract and the kidneys

Water loss occurs through 4 organs

Kidneys – 1200-1500 ml (in urine)

Skin – 500-600 ml (sensible and insensible, increases with fever, burns, sweating)

Lungs – 400 ml (through act of breathing)

GI tract – 100-200 ml (in feces), can be large area of loss through vomiting or diarrhea

Regulation of Electrolytes

Sodium – most abundant in ECF, imbalances will cause a change in osmolality, affects the water distribution between ICF and ECF, transmission of nerve impulses, regulation of acid-base balance, movement of potassium, sodium leaves through urine, sweat, feces; kidneys are primary regulator of sodium balance, serum sodium reflects the ratio of sodium to water so it can explain a water imbalance, sodium imbalance or a combo of the two

Potassium – most abundant in ICF, moves into cells with formation of new tissues and leaves the cell during tissue breakdown, most common cause of imbalance is use of potassium-wasting diuretics such as thiazide and loop diuretics, kidneys are the primary route of potassium loss, factors that cause sodium retention cause potassium loss in the urine, necessary for transmission and conduction of nerve impulses and for contraction of skeletal, cardiac and smooth muscles; very narrow normal range, too little or too much can lead to cardiac arrest, poorly stored in the body so must give it daily, diet is our primary source of potassium, bananas and dried fruits are higher in potassium than oranges and fruit juices; extremely irritating to the GI and intestinal tract so give with a full glass of fluid, IV potassium must be diluted in IV fluids, cannot be given as a bolus or push, always must be diluted or can cause cardiac arrest

Calcium – located mostly in the bone, necessary for bone/teeth formation, blood clotting, transmission of nerve impulses, muscle contractions, taken in by diet but must have Vitamin D to absorb calcium

Magnesium – needed to prevent overexcitability of muscles

Phosphate – primary anion in ICF, essential to function of muscles, RBCs and nervous system

Chloride – primary anion in ECF, always follows sodium, regulated by diet and kidneys

Bicarbonate – found in both ECF and ICF, plays a big role in acid-base balance, regulated by the kidneys

Regulation of Acid-Base Balance

For cells to work properly, metabolic processes must maintain a balance between acids and bases; the two physiologic buffers in the body are the lungs (which work the quickest) and the kidneys, there are also chemical and biologic buffers in the body

Acid - < 7.35

Neutral – 7.4

Alkaline - > 7.45

CO2 – regulated by the lungs

HCO3 – regulated by the kidneys

Calculating acid-base balance (the other way to do this is by using ROME which we distributed earlier this semester)

Determine acid-base balance (pH) - if low it’s acidosis, if high it’s alkalosis

Determine cause of acid-base balance

CO2 (respiratory) - if high it’s acidosis, if low it’s alkalosis

Are both the pH and CO2 the same (acidosis or alkalosis)? If so, it’s respiratory acidosis or alkalosis (whatever matches with the pH), if not then the respiratory system is only compensating and is not the primary cause of the imbalance

HCO3 (metabolic) - if high it’s alkalosis, if low it’s acidosis

Are both the pH and the HCO3 the same (acidosis or alkalosis)? If so, it’s metabolic acidosis or alkolosis (whatever matches with the pH), if not then the metabolic system is only compensating and not the primary cause of the imbalance

| |pH |CO2 (respiratory) |HCO3 (metabolic) |

| |(7.35 - 7.45) |(35 – 45) |(22 – 26) |

|High |Alkalosis |Acidosis |Alkalosis |

|Low |Acidosis |Alkalosis |Acidosis |

|Normal |Normal |Normal |Normal |

Acid-Base Disorders

Respiratory Acidosis – low pH, high CO2

Causes – hypoventilation from respiratory causes (pneumonia, respiratory failure) or non-respiratory causes (drug overdose, head injury, obesity)

Symptoms – confusion, dizziness, lethargy, headache

Respiratory Alkalosis – high pH, low CO2

Causes – hyperventilation from respiratory causes (asthma, pneumonia) or non-respiratory causes (anxiety, fever, exercise, head injury, infection, salicylate overdose)

Symptoms – dizziness, confusion, rapid breathing, numbness and tingling of the extremities

Metabolic Acidosis – low pH, low HCO3

Causes – starvation, diabetic ketoacidosis, renal failure, lactic acidosis, use of aspirin or ethanol

Symptoms – headache, lethargy, confusion, rapid and deep breathing, abdominal cramps

Metabolic Alkalosis – high pH, high HCO3

Causes – vomiting, GI suction, electrolyte imbalances, use of diuretics or antacids

Symptoms – dizziness, numbness and tingling of extremities, muscle cramps, tetany

Electrolyte Imbalances

Sodium and chloride are the most easily lost because they are the primary extracellular electrolytes, lost through sweating, bleeding or excretion

Hyponatremia (low sodium) – water excess or loss of sodium, most common electrolyte disorder in the US, occurs frequently in the seriously ill; when there is too little sodium in the tissue fluids water moves into the cells, usually not a problem because tissues will expand but in the brain there is no room for expansion, most symptoms of hyponatremia are related to the brain’s inability to expand in the cranium

Causes - water overload, kidney failure, trauma, CHF (congestive heart failure), fresh water drowning, overadministration of hypotonic fluids, taking water pills (diuretics)

Signs/Symptoms - muscle weakness, confusion, headaches, abdominal cramps, nausea, vomiting, seizures, can progress to coma, first symptoms are in the CNS as brain cells swell

Treatment – usually can not be fixed by adding sodium to the diet, can give NS (3% normal saline) to increase sodium content in the vascular fluid, if caused by fluid excess will need fluid restriction

Hypernatremia (high sodium) – water deficit, causes hyperosmolality which causes a shift of water out of the cells leading to cellular dehydration, occurs with water loss or sodium gain

Causes – renal failure, can result from consuming certain drugs (cortisone, cough meds, some antibiotics), excessive salt ingestion, decreased fluid intake, osmotic diuretics (Mannitol), hyperglycemia

Signs/Symptoms – thirst, hyperreflexes, flushed skin, elevated body temp, elevated BP, rough dry tongue, lethargy, seizures, excessive sweating

Treatment – treat the underlying cause (ie. decreased water – water replacement, D5W; increased sodium – salt free IV fluids, diuretics, decreased sodium intake), sodium restriction, avoid high sodium foods (ie. _____________), seizure precautions, have to reduce sodium slowly to avoid swelling in the brain

Hypokalemia (low potassium) – the body is more sensitive to small changes in potassium levels than any other serum electrolyte, very important for cardiac function

Causes – excessive vomiting, suctioning, vomiting, diarrhea, medications (diuretics, laxatives, insulin), alkalosis (causes exchange of H+ for K+), beta adrenergic stimulation, rapid cell building (ie. B12 or erythropoietin to increase RBCs)

Signs/symptoms – weakness, nausea, vomiting, dysrhythmias, constipation, low BP, increased pulse, increased digoxin toxicity, muscle weakness and paralysis, muscle cramping, rhabdomyolosis, hyperglycemia, diuresis

Treatment – for slightly low levels encourage foods high in potassium (fruit juice, citrus fruits, dried fruits, bananas, nuts, veggies), cardiac monitor, watch for digitalis toxicity, must have good urine output (>600 ml/day) before giving any potassium supplements, never give potassium IV push, always must be diluted and given as a drip

Hyperkalemia (high potassium) - the body is more sensitive to small changes in potassium levels than any other serum electrolyte, very important for cardiac function; can get false high results if lab specimen is not drawn or handled properly

Causes – kidney failure is most common cause, use of salt substitutes or potassium supplements, receiving old or improperly administered blood, cell destruction (ie. crush injuries, burns, hemolysis), acidosis, hypoxia, exercise, catabolic state (ie. severe infection)

Signs/symptoms – diarrhea, apathy, weakness, confusion, numbness to hands/feet, slow pulse, cardiac arrhythmias, cramping leg pain, abdominal cramping

Treatment – cardiac monitor, give kayexalate (either orally or as enema), calcium gluconate, glucose & insulin IV (helps move potassium into cells), teach client to avoid foods high in potassium (cantaloupe, bananas, apricots, broccoli, salt substitutes)




Fluid volume imbalances are typically accompanied by electrolyte imbalances; sudden body weight change is an excellent indicator of overall fluid volume loss or gain (1 liter = 2.2 lbs or 1 kg)

Fluid volume excess – overhydration, hypervolemia

Causes – congestive heart failure (CHF), renal failure, excessive sodium intake, excess water intake, SIADH (syndrome of inappropriate antidiuretic hormone), interstitita to plasma fluid shift

Signs/symptoms – rapid weight gain, edema, high BP, increased urine output (if kidneys normal), neck vein distention, bounding pulses, crackles in the lungs, shortness of breath, decreased level of consciousness

Lab values – decreased hematocrit, decreased BUN, increased sodium, increased osmolality

Treatment – use of diuretics, fluid restriction, sodium restriction, monitor daily weight and strict Is & Os, no IV fluids

Fluid volume deficit – dehydration, hypovolemia

Infants, clients with neurological or psychological problems, and some older adults who are unable to perceive or respond to the thirst mechanism are at risk for dehydration

Causes – vomiting, diarrhea, hemorrhage, sweating, fever, dehydration, use of diuretics, administration of hypertonic solutions or tube feedings, heat exhaustion/stroke, plasma to interstitial fluid shift

Signs/symptoms – low BP, high pulse, dry mouth, thirst, rapid weight loss, confusion, lethargy, low urine output

Lab values – urine specific gravity > 1.030, increased hematocrit (except in hemorrhage) increased BUN, decreased sodium, decreased osmolality

Treatment – replace fluid loss with isotonic fluids, monitor daily weight and strict Is & Os, give balanced solutions (ie. LR, NS if rapid volume is needed)

IV Therapy

Nurse must know about the different types of solutions, equipment and skills needed to start an IV, how to regulate the infusion rate, how to identify and correct problems an discontinue an IV

IV Solutions (Fig 16-7, pg 334, Lewis)

Isotonic – solutions with same osmolarity as blood plasma, expands the body’s fluid volume without causing a fluid shift from one compartment to another, very similar to ECF and ICF (ie. 0.9% sodium chloride – NS, D5W, LR, Ringer’s solution), D5W when given rapidly or continuously will become hypotonic because it is metabolized quickly

Hypertonic - a solution of higher osmotic pressure that pulls fluid from cells causing them to shrink (ie. 3% NS, D5½NS, D10W)

Hypotonic solution - a solution of lower osmotic pressure, moves fluid into the cells, causing them to enlarge (ie. 0.45% sodium chloride – ½NS)

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 capillaries; Colloids – volume expanders, dextran solutions, amino acids, hetastarch, plasmanate, dextran is not a substitute for whole blood because it doesn’t 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

IV Equipment

Use of a pump to control volume is critical with children, clients with cardiac or renal problems and critically ill clients – even with use of a pump nurses are still responsible for ensuring that equipment is working correctly, if not seeming to be working properly always check the IV site first for infiltration, patency, restrictive IV dressing, position if the client’s extremity, if the site is good trace the line up to the pump looking for kinks, knots, clots, air in the tubing, empty bag, bag hung to low

IV Initiation

Most common site is hand and arm, use of the foot is common in children but contraindicated in adults due to risk of thrombophlebitis

Venipuncture is contraindicated in areas of infection, infiltration, thrombosis, arm on the side of a mastectomy, arm with a dialysis graft

Place IVs at the most distal point to allow the use of proximal sites later if needed

No more than 2 attempts at IV insertion should be made by a single nurse

If an IV is alarming occluded, check for _________, calculating what is left in the bag

IV Maintenance

Keep the system sterile – clean ports with alcohol before accessing, use shortest amount of tubing necessary

Change solutions, tubing, dressing – maintain sterility when changing

Assist the client with self-care so as to not disrupt the system

IV Complications

Infiltration – pallor, coolness, swelling; treat by removing IV, elevate extremity, wrap with warm, moist towel for 20 minutes

Phlebitis – pain, swelling, warmth, redness up the vein; treat by removing IV, warm, moist heat

Lab Normals

The Magic 4’s (a quick way to try to keep all of these normals straight)

Electrolyte Range Magic 4

Potassium 3.5 – 5.5 4

Chloride 98 – 106 104

Sodium 135 – 145 140

pH 7.35 – 7.45 7.4

pCO2 35 – 45 40

HCO3 22 – 26 24

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


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