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The Body and Water

  • Men are bout 60% water

  • Women are about 50% water

  • older adults are about 50% water

  • infants are about 80% water

  • Fat cells contain less water than other cells

  • water is split between ICF and ECF

Body fluid compartments

  • Body water is distributed in three types of areas seperated by membranes

  • In the cells: intracellular fluid

  • in the blood vessels: intravascular fluid

  • between the tissue spaces: interstital fluid

Body fluid compartments

  • ICF: 2/3 of fluid 40% tbw of adult

  • ECF: 1/3 of fluid (1/3 in plasma, 2/3 between cells) 17-20% tbw

  • Transcellular: fluid in cerebrospinal space, GI tract, pleural space, synovial space (not reabsorbed)

Functions of body water

  • Transport of oxygen, nutrients, and lytes

  • excretion: used in elimination of waste

  • regulation of body temp and hydration

  • lubrication for joints, mucous production and aids in digestion

Fluid I/O

  • Intake: liquid 1000ml, Food 800-1000ml, oxidation of food 300ml

  • Output: skin 300-500ml*, Lungs 400-500ml*, Urine 1000-5000ml

  • * are insensible losses that cannot be measured

Definitions related to fluid and fluid movement

  • Homeostasis: state of eqilibrium (the goal of every cell)

  • membrane: a layer or tissue that seperates two compartments, organ or lining

  • permeability: the capability of a substance, molecule, or ion to pass thru a membrane

  • Some membranes are semi permeable or impermeable


  • movement of a substance thru a permeable membrane

  • large molecules move more slowly

  • simple diffusion require no eternal energy

  • facillitated diffusion: some molecules diffuse slowly into a cell and require a carrier molecule to aid in the speed of passage

  • substances move down the concentration gradient

Active transport

  • a process in which a molecule moves against the concentration gradient

  • requires energy in the form of ATP

  • Na/K pump


  • the movement of water between two compartments seperated by a membrane permeable to water but not solutes

  • water determies the final concentration gradient

  • a semi permeable membrane prevents the movement of some but not all solutes

Osmotic Pressure
The amount of pressure needed to stop the osmotic flow of water. water moves from less concentrated areas to greater concentrated areas to a point then stops. pressure is determined bu the concentration of solutes in a solution


  • Osmolality: measurement of milliosmoles of solute per volume (mOsm/L)

  • Osmolarity: measure of the osmotic force of the solute per unit of weight (mOsm/kg)

  • Serum osmoality determines the pull of the serum, approx 290 mOsm/L

Tonicity, Solvents, Solutes

  • Tonicity: the efect of a fluid on cellular volume

  • Solvent: the liquid in which solutes are dissolved

  • Solute: the substance which is dissolved in a solvent

Hypotonic/Hyperosmolor fluids

  • Fluids are less concentrated than the cells interior

  • also known as "free water"

  • a solution with less than 240 mOsm of solute

  • It causes fluid to move into the cell

  • These fluids are used for hydration, but may cause the cell to swell and eventually burst

  • They aid the kidneys in eliminating solutes

  • Often used to correct hypernatremia

  • plasma sodium should be diluted slowly

Isotonic/iso-osmolar fluids

  • They have the same osmolarity as the cell interior therfore, fluid does not move into the cell

  • 240-340 mOsm

  • used to increase the vascular bed/ intrvascular space

  • Approx 1/3 stays intravascular

  • used to treat hypovolemia

  • D5W: not to be used in excessive amounts (turns hypo after dextrose is processed)

  • 0.9 NS: only provides NaCl, may be used to expand the extracellular compartment if circulation is insufficient (hypovolemia)

  • LR: contains multiple lytes to approximate concentrations as found in the plasma, used initially in hypovolemia and burns (check renal function, risk for increased lytes)

Hypertonic/ Hyperosmolar fluids

  • have a higher level of solutes than found within the cells interior

  • >340 mOsm

  • can pull fluids from inside the cell causing them to shrink

  • can be used as maintenance fluids or long term nutrition

  • D5/45: commonly used as a maintenance fluid

  • D10/W: supplies 340cal/L and is used for nutrition

  • D5/0.9: replaces some nutrition and may be used as a volume expander (when used for hypovolemia the level of dextrose infused is a concern)

IV fluid classifications

  • Crystalloids: can be hypo, iso, or hyper

  • colloids: volume expanders, they function like a plasma protein (albumin, hespan, hetastarch, dextran

  • blood products: used to replace blood loss

Hydrostatic and oncotic pressures

  • Hydrostatic pressure: the force fluid within a compartment "pushing pressure" it is the force that pushed water out of the vascular system at the capillary bed

  • oncotic pressure (colloid oncotic pressure): this is the pressure exerted by the colloids (proteins) in a solution. proteins attract water this can be thought of as pulling pressure


  • proteins are nitrongenous compounds that are essential to all living things

  • plasma proteins are: albumin, globulin, and fibrinogen

  • serum proteins are albumin and globulin

  • albumin constitutes about 50% of blood proteins

  • gllbulin is a simple protein


  • edema is a swelling of tissues and develops from increased hyrdrostatic pressure

Fluid spacing

  • First spacing is the normal distribution of fluid between ICF and ECF

  • Second spacing is the abnormal accumulation of fluid in the interstitial space eg. edema

  • Third spacing is fluid accumulating within a portion of the body which is not easily exchanged with rest eg. ascities,

Regulation of water balance

  • thirst: osmoreceptors signal inadequate intake of fluid

  • regulated by the hypothalamus

  • stimulated by an increase in ECF and and the drying of mucous membranes

  • causes an intake of fluid that moves from the GI tract to the bloodstream

Antidiuretic hormone (ADH)

  • hypothalamus senses decreased blood volume and increased serum osmolality

  • The posterior pituitary gland secretes ADH into the bloodstream

  • ADH acts on the kidneys at the distal renal tubule to retain water

  • water retention boosts blood volume and decreases serum osmoality


  • Decreased blood flow or Na to the kidneys causes the juxtaglomerular cells to secrete renin

  • renin moves to the liver and converts agniiotension into angiotension I

  • angiotension I moves to the lungs where it is converted into angiotension II (a powerful vasoconstrictor)

  • angiotension II moves to the adrenal glands to stimulate aldosterone production

  • Aldosterone initiates active transport of Na from the distal tubules and collecting ducts into the bloodstream

  • Water follows Na

Atrial Naturetic Peptide (ANP)

  • ANP is stored in the atria of the heart and responds to stretching of the atiria

  • As the atria stretch ANP is released which supresses renin levels, decreases aldosterone prduction, increases glomerular filtration which increses water and Na excretion, decreases ADH release, causes vasodilation

What is the purpose IV therapy?

  • To maintain

  • to catch up

  • to keep up

  • nutrition

Possible nursing diagnosis related to fluids

  • fluid volume in excess more than body requirements

  • fluid volume deficit less than body requirements

Fluid volume excess S/S

  • pulmonary edema

  • dyspnea

  • crackles in bases

  • JVD

  • bounding pulse

  • edema

  • weight gain

  • neruologic changes (d/t decreased Na)

  • labs: decreased serum albumin, Na, osmoality

Etiologies of fluid volume deficit

  • Inadequate fluid intake

  • increased solute intake (salt, sugar, protein)

  • severe vomiting or diarrhea

  • sweating from fever or increased metabolic demand

  • hemorrhage

  • burns

  • ascities

Fluid volume deficit s/s

  • dry mucous membranes: moderate

  • tenting skin: moderate

  • complaints of thirst: mild

  • Decreased BP and strength of peripheral pulses: severe

  • decreased urinary ouput: moderate-severe

  • labs: increased serum BUN, Na moderate-severe


  • Fluid and electrolye imbalances can occur in most pt''s with major illness due to disruption of the homeostatic imbalance

  • In most instances more than one imbalance occurs in the same pt

  • An electrolyte is an element or compound that dissociates into ions and provides for cellular reactions

Sodium Na
  • Normal Range 135-145 mEq/L
  • Sodium is the major regulator in maintaining the concentration and volume of extracellular fluid
  • Sodium affects the water distrbution between ECF and ICF
  • Important for the transmission of nerve impulses
  • Mainly absorbed by the GI tract
  • Daily intake is typically more than requirements
  • The kidneys regulate fluid shifts by excreting sodium or retaining it via aldosterone in the tubules
  • Water follows sodium
  • Na imbalances are typcially associated with imbalances in the ECF
  • It is an alectrolyte that is associated with the neurological system
  • Na/K pump regulates polarization and depolarizaion
Hypernatremia Etiologies
  • Water loss d/t: fever, dehydration, diabetes insipidus, osmotic diuresis
  • Sodium Gain d/t: IV hypertonic NaCl, IV sodium bicarb, primary hyperaldosteronism, ingestion of too much sodium
Hypernatremia Clinical Manifestations
  • Na >145 mEq/L
  • intense thirst, dry swollen tongue
  • restlessness, anorexia
  • vomiting, agitatin, twitching
  • seizures, coma, weakness
  • lethargy, confusion, hypotension
  • twitching hyperreflexia, ataxia, tremors

  • With too much sodium in your system you get hyperosmolarity

  • The prmary defense against this is thirst

  • Hypothalamus is stimulated and the individual gets something to drink

  • not an issue in a relatively healthy adult

Hypernatremia Treatment
  • Treat the underlying cause: vomiting diarrhea, Gi suction, overuse of diuretics, Hemorrhages
  • If dehydration is the cause slowly rehydrate with D5W. If rehydration happens too quickly cerebral edema can result.
Hyponatremia Etiologies
  • Water excess: hypo-osmoality with a shft of water into the cells
  • Too much "free water" d/t SIADH, CHF
  • Sodium losses: GI losses, diatthea, vomiting, NG suction, burns, wound drainage, renal losses d/t adrenal insufficiency
Hyponatremia Clinical Manifestations
  • Na <135 mEw/L
  • Irritability, confusion, nausea, vomiting, anorexia
  • Primarily neurological symptoms
  • Disorientation, change in LOC, muscle twitching, ataxia, seizures, coma
Hyponatremia Treatment
  • Mild: fluid restriction, oral sodium replacement, potato chips
  • If related to hypovolemia, IV 0.9 NS
  • Severe: ICU with infusion of 3%-5% saline, monitor for fluid overload
Nursing considerations for sodium imbalances
  • Monitor I/O
  • Daily weight: most sensitive measure of fluid status
  • Assessment of skin turgor
  • V/S including LOC, hypo/hypertension
  • Keep pt safe, monitor position changes for orthostatic hypotension
  • Na is the electrolyte of neurological disfunction
  • Normal range 3.5-5 mOsm/L
  • Potassium is the major ICF electrolyte
  • It is critical for many cellular and metabolic functions
  • Promotes cellular growth and cardiac function
  • It moves into the cell during the formation of new tissue and leaves the cell during breakdown
  • The kidneys are the primary route for loss of potassium
  • Vital for the transmission and conduction of nerve impulses
  • Factors that disrput the equilibrium between ICF and ECF often manifest as clinical problems related to potassium (beta-blocker therapy, elevated digoxin levels)
  • Potassium may move from the ECF to ICF following: insulin administration, alkalosis, rapid cell building, DTs
  • important in the contractin of skeletal muscle
Hyperkalemia Etiologies
  • Intake of too much potassium
  • Renal impairment is the most common
  • Potassium sparing diuretics (aldactone)
  • ACE inhibitors due to taxing renal function (meds ending in -pril)
  • severe metabolic acidosis
  • Shift of potassium from ICF to ECF
  • Burn injuries, trauma, crush injuries
Hyperkalemia Clinical Manifestations
  • Serum potassium > 5 mEq/L
  • Iritability
  • anxiety
  • nausea
  • abd cramping
  • diarhhea
  • weakness of lower extremities
  • irregular pulse
  • ECG changes: tall peaked t waves, blocks, asystole
Hyperkalemia treatment
  • Eliminate oral and IV sources of potassium
  • Increase elimination of potassium thru: loop diuretics, dialysis, kayexalate (enema)
  • Force potassium into the cell: insulin with a glucose chaser, IV sodium bicarb (requires a dedicated line), IV calcium gluconate
Hypokalemia Etiology
  • Abnormal loss of potassium from a shift from ECF to ICF
  • usually renal losses from diuretics
  • GI tract emesis, diarrhea
  • elevated aldosterone levels save Na, but lose K
  • Low Mg levels
  • severe metabolic alkalosis
Hypokalemia Clinical Manifestations
  • fatigue
  • muscle weakness
  • leg cramps
  • nausea
  • vomiting
  • decreased reflexes
  • weak, irregular pulse
  • polyuria
  • hyperglycemia
  • digoxin toxicity
  • ECG changes: flattened T wave, bradycardia
Hypokalemia Treatment
  • Replacement of potassium (only given if urine output is at least 0.5 ml/kg/hr
  • IV potassium should be given slowly, not to exceed 10-20 mEq/hr
  • IV potassium is irritating to the vein, a central line should be used when possible
Nursing considerations: potassium
  • Pt teaching: foods high in K (orange juice, bananas, beans, broccoli, carrots, lima beans, potatoes, beef, chicken, turkey, chocolate, sunflower seeds)
  • take medications as directed (potassium, diuretics, digoxin)
  • Normal range 9-11 mg/dL
  • Ca is obtained from ingested food
  • 30% absorbed in the GI tract
  • 99% of body's Ca is combined with phosphorus
  • bones serve as a readily available source of Ca
  • Ca and phosphorus have an inverse relationship
Calcium-- Forms of Ca in the body
  • Free/ionized
  • bound to protein (albumin)
  • Complexed with phosphate, citrate, or carbonate
  • Ca balance is controlled by PTH, calcitonin, and Vit D
  • Ca is important in the contraction of the cradiac muscle
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