fluid volume depletion and excess

what is homeostasis?

maintaining a stable balance of fluids, electrolytes, and acid-base status

what four things are body fluids essential for?

• transporting oxygen, nutrients, and waste products

• regulating body temperature

• maintaining blood volume and blood pressure

• supporting normal cellular function

what are electrolytes?

charged particles (ions) that regulate fluid balance, nerve impulses, and muscle contraction

what is total body water (TBW)?

approximately 50-60% of adult body weight; varies with age, sex, and body composition

what are the two types of extracellular fluid?

intravascular and interstitial

what is intravascular fluid?

fluid within blood vessels (plasma)

what is interstitial fluid?

fluid between cells (tissue)

older adults have ___ total body water

less; increases vulnerability to fluid imbalances

what is diffusion?

movement of solutes from high to low concentration

what is osmosis?

movement of water across a semipermeable membrane toward the higher solute concentration

what is osmolality?

concentration of dissolved particles in a fluid; influences water movement

what is the major determinant of extracellular fluid osmolality?

sodium (Na+)

what are the two types of fluid movement between blood vessels and tonicity?

hydrostatic pressure and oncotic pressure

what is hydrostatic pressure?

pushes fluid out of capillaries into tissues

what is oncotic pressure?

plasma proteins (especially albumin) pulling fluid into capillaries

what is tonicity?

• how IV solutions affect cell size

• isotonic, hypotonic, and hypertonic

what is an isotonic solution?

no net water movement → cells stay the same size

what is a hypotonic solution?

water moves into cells → cells swell

what is a hypertonic solution?

water moves out of cells → cells shrink

what are the five major mechanisms for regulating fluid balance?

kidneys, ADH, RAAS, ANP, and thirst

how do the kidneys regulate fluid balance?

regulate sodium and water excretion

how does ADH regulate fluid balance?

• increases water reabsorption → fluid retention

• ADH retains water

how does RAAS (aldosterone) regulate fluid balance?

• increases sodium reabsorption (water follows) → increased blood volume and BP

• aldosterone retains sodium

how does ANP (atrial natriuretic peptide) regulate fluid balance?

promotes sodium and water excretion → decreased blood volume and BP

how does thirst regulate fluid balance?

encourages fluid intake when the body needs water

which fluid balance maintenance systems increase blood volume and BP?

ADH and aldosterone

which fluid balance maintenance system decreases blood volume and BP?

ANP

what are fluid volume disorders?

changes in extracellular fluid volume due to sodium and water loss or retention

what are the two types of fluid volume disorders?

fluid volume depletion and fluid volume excess

what is fluid volume depletion?

loss of sodium and water → decreased ECF volume

what is fluid volume excess?

retention of sodium and water → increased ECF volume

what are sodium concentration disorders?

changes in osmolality that cause water to shift between cells and extracellular fluid

what are the two types of sodium concentration disorders?

hyponatremia and hypernatremia

what is hyponatremia?

low sodium → water shifts into cells → cellular swelling

what is hypernatremia?

high sodium → water shifts out of cells → cellular shrinking

what is fluid volume depletion?

• hypovolemia

• loss of sodium and water → decreases extracellular/intravascular fluid volume

what may severe fluid volume depletion cost?

hypovolemic shock due to inadequate tissue perfusion

what are common causes of fluid volume depletion?

excessive fluid loss, inadequate fluid intake, and third spacing

what is third spacing?

• fluid shifts from blood vessels into tissues

• ex: sepsis, burns, liver failure

what is the pathophysiology of hypovolemia?

loss of fluid → decreased circulating blood volume → decreased cardiac output and tissue perfusion

what are compensatory responses for hypovolemia?

increased HR, vasoconstriction, and ADH/RAAS activation

what are early findings of hypovolemia?

thirst, tachycardia, oliguria, dizziness

what are progressive/severe findings of hypovolemia?

orthostatic hypotension, AMS, signs of shock

what are laboratory findings of hypovolemia?

• increased BUN due to decreased blood flow to the kidneys

• increased urine specific gravity

• possible electrolyte abnormalities

what is the treatment goal of hypovolemia?

• restore circulating volume and tissue perfusion

• treat underlying cause of fluid loss

how do you treat mild fluid volume depletion?

oral fluid and electrolyte replacement

how do you treat moderate to severe fluid volume depletion?

IV isotonic crystalloids (0.9% Normal Saline or Lactated Ringer’s)

what are nursing priorities for hypovolemia?

• monitor BP, HR, urine output, and mental status

• assess for improvement in perfusion and signs of fluid overload

what are crystalloids?

IV solutions containing water and small dissolved substances

what are the uses of crystalloids?

replace fluid losses, maintain hydration, and correct fluid/electrolyte imbalances

what are the types of crystalloids?

isotonic (0.9% NS, LR), hypotonic (0.45% NS), hypertonic (3% NS), and D5W

what does 0.9% NS do?

expand ECF and ICF volume

what does hypotonic NS do?

provide water that can move into cells

what does hypertonic NS do?

draw water from cells into ECF

what does D5W do?

• it is isotonic in the IV bag, but acts as free water after glucose metabolism

• physiologically hypotonic

what are nursing considerations for crystalloids?

• monitor I&Os, daily weights, electrolytes, and signs of fluid overload

• use in caution in clients with heart or kidney dysfunction

what is the mechanism of lactated ringer’s?

replaces fluid and electrolytes; lactate helps buffer acidosis

what are the uses of lactated ringers?

hypovolemia, burns, trauma, and surgery

wha are precautions for lactated ringers?

heart/kidney dysfunction; fluid overload

what are adverse effects of normal saline?

hyperchloremic metabolic acidosis

what are adverse effects of lactated ringers?

fluid overload; electrolyte disturbances

what are nursing considerations for lactated ringers?

monitor I&Os, BP, lung sounds, edema, and electrolytes

what are nursing considerations for normal saline?

it is used with blood administration only!!

what is a precaution of D5W?

it is not appropriate for initial fluid resuscitation in hypovolemia or shock

what is hypervolemia?

excess sodium and water retention → increased ECF volume

what are common causes of hypervolemia?

kidney dysfunction and HF

what are clinical manifestations of hypervolemia?

rapid weight gain, jugular vein distention, dyspnea, orthopnea, crackles, and decreased oxygen saturation

what is a severe complication of hypervolemia?

pulmonary edema

what are signs of pulmonary edema?

pink, frothy sputum

whats the treatment goal of hypervolemia?

reduce excess fluid volume and treat the underlying cause

what are management options for hypervolemia?

• sodium and fluid restriction when indicated

• diuretics (such as furosemide)

what are nursing considerations for hypervolemia?

• monitor I&Os, daily weights, BP, lung sounds, and edema

• monitor electrolytes, especially potassium

• assess respiratory status

what are the four major mechanisms of edema?

• increased hydrostatic pressure

• decreased oncotic pressure

• increased capillary permeability

• impaired lymphatic drainage

what is the distribution of edema?

unilateral or bilateral/generalized edema

what is bilateral/generalized edema commonly associated with?

heart, kidney, or liver disease

what is unilateral edema associated with?

localized obstruction or DVT

what are severe complications of edema?

pulmonary, cerebral, or airway edema may be life threatening

what are the treatment goals of edema?

treat the underlying cause, reduce swelling, and prevent complications

what are management options for edema?

• sodium restriction and diuretics

• elevate

• compress

• pulmonary, cerebral, or airway edema requires immediate intervention

what are nursing considerations for edema?

• monitor daily weights, I&Os, BP and edema

• monitor kidney function and electrolytes

• diuretics: monitor for hypotension and potassium abnormalities

what is free water deficit?

body doesn’t have enough water relative to sodium → intracellular dehydration