chapter 35 hydration and homeostasis

1st semester

electrolytes

substances that develop an electrical charge when dissolved in water

nonelectrolytes

other substances that do not conduct electricity

osmolality

concentration of solute per kg of water (concentration of solution). normal is 275-295 mOsm/kg of water (270-300)

solvent

substance in which the substance is dissolved (usually water) 

solute

the substance dissolved

osmolality and osmolarity

used interchangeably

isotonic

same osmolality as blood

examples of isotonic solutions

normal saline (NS) and lactated ringers (LR)

hypotonic

lower osmolality than blood. will cause water to move into cells (cells will swell). “hippo”

hypertonic

higher osmolality than blood. will cause water to move out of cells (cells will shrink).

example of hypotonic solution

½ NS

examples of hypertonic solution

3% NS and D5W

hydrostatic pressure

pushes fluid out of vessel into tissue space

osmotic pressure

pulls fluid into vessels

intracellular fluid (ICF)

• all fluids within body cells

• 40% of body weight

• high in K+/low in NA+

• most (2/3) of the body’s H2O is in the ICF

extracellular fluid (ECF)

• all fluid outside of cells

• 1/3 of body’s H2O is in ECF

• more prone to loss

• high in NA+/low in K+

• divided into 3 smaller compartments:

  • interstitial- fluid in spaces between cells

  • intravascular- fluid in arteries/veins

  • transcellular- CSF, pleural fluid, peritoneal, GI secretions

cations

positively charged electrolyes

anions

negatively charged electrolytes

cation in ICF

K+

cation in ECF

NA+

anion in ICF

PO4³- (phosphorus)

anion in ECF

CL- (chloride)

Diffusion

a solute in a solution moves from an area of higher concentration to lower concentration that results in equal distribution (gas exchange in lungs).

Filtration

water and diffusible substances move across a membrane in response to hydrostatic pressure.

Osmosis

movement of solvent (fluid) across a semipermeable membrane from lower to higher concentration (IVF administration)

active transport

movement of molecules or ions from an area of lower concentration to a level of higher concentration Na+ - K+ - ATPase Pump). external energy is required.

regulation of fluid intake

• thirst mechanism

• osmoreceptors

average adult daily fluid intake

2200-2700 mL (approximately 800-1000 mL through solid foods)

regulation of hormones

ADH stored in posterior pituitary gland

• Angiotensin 1

• Angiotensin 2

• Aldosterone

Natriuretic peptides- hormone from the heart. increases urination by blocking aldosterone.

regulation of fluid output

• insensible loss

• sensible loss

• kidney

  • 1500 mL/day

  • 30-50 mL/hr

• skin (500-600 mL)

• lungs (300 mL)

• gastrointestinal (feces) (100-200 mL)

sensible loss

• can be measured

• urine

• stool

• NG output

• skin (perspiration)

insensible loss

• hard to measure, hard to see, continuous

• occurs through skin (evaporation), lungs, GI

• increases with fever

released by the liver

angiotensin

released by the kidneys

renin

released by the adrenal cortex

aldosterone

fluid and electrolyte imbalance

• common in most patients with illness

• directly caused by illness or disease

• may be the result of therapeutic measures such as IV fluid replacements or diuretics

• chronic medical conditions, surgery

  • sometimes more at risk

gerontologic considerations

• structural changes in kidneys decrease ability to conserve water

• hormonal changes lead to decrease in ADH and ANP

• loss of subcutaneous tissue leads to increased loss of moisture

• reduced thirst mechanism results in decreased fluid intake

• nurse must assess for these changes and implement treatment accordingly

sodium (cation)

• 135-145 mEq/L

hyponatremia

low sodium

hypernatremia

high sodium

signs and symptoms of hyponatremia

signs and symptoms of hypernatremia

potassium (cation)

3.5-5 mEq/L

signs and symptoms of hypokalemia

signs and symptoms of hyperkalemia

hypokalemia

low potassium

hyperkalemia

high potassium

calcium (cation)

8.5-10.5 mg/dl

hypocalcemia

low calcium

hypercalcemia

high calcium

signs and symptoms of hypocalcemia

signs and symptoms of hypercalcemia

magnesium (cation)

1.6-2.6 mEq/L

hypomagnesemia

low magnesium

hypermagnesemia

high magnesium

signs and symptoms of hypomagnesemia

signs and symptoms of hypermagnesemia

fluid disturbances

• FVD

• FVE

organs that contribute to fluid loss

• kidneys

• skin

• lungs

• GI tract

sodium

• major ECF cation

• primary regulator of fluid volume, important for brain health

• kidney reabsorbs

potassium

• major ICF cation

• muscle contraction, cardiac conduction

• kidneys eliminate

• regulated by diet and kidneys

• dialysis patients should limit due to impaired kidney function and inability to excrete

foods with Na+

foods with K+

calcium

• essential for blood clotting

• bone health; nerve transmission; cardiac function; muscle contraction

• insufficiency leads to osteoporosis

• dietary sources: dairy, sardines, whole grains, leafy greens

magnesium

• 1% is in blood 

• 99% is in bones

• ICF; bone; many cellular functions- muscle contraction, cell metabolism, NM excitability

• alcoholism leads to low levels

• dietary sources: almonds and other nuts, cooked spinach, soy

phosphorus is found as ____ in the body

phosphate

Treatment for hyponatremia

• Provide sodium replacement as ordered

• The Na+ must not be increased by 12 mEq

• Provide water restriction

• I&O, daily weights, seizure precautions

Treatment for hypernatremia

• Administer hypotonic IV solutions

• Administer diuretics

Treatment for hypokalemia

• IV or PO replacement

• NEVER administer by IV push (only as IV/IVPB). Only time it is pushed is on death row!

• Cardiac monitoring

• Encourage potassium rich foods

Treatment for hyperkalemia

• Cardiac monitoring

• IV calcium gluconate

• Administration of insulin

• Kayexelate

• Possible hemodialysis

• Avoid potassium rich foods

Treatment for hypocalcemia

• Oral or IV supplement

• Seizure precautions

• Increase calcium in diet

Treatment for hypercalcemia

• Avoid calcium antacids

• Increase fluids

• Diuretics

• Possible dialysis

• Prevent fractures

Treatment for hypomagnesemia

• PO or IV Mg supplements

• Increase Mg in diet

Treatment for hypermagnesemia

• Diuretics

• Stop magnesium antacids

• IV fluids

• Monitor DTRs

Which population is more at risk for fluid volume deficits?

Elderly

Hypovolemia

Loss of ECF and electrolytes

Dehydration

• Loss of water alone, with increased solutes concentration

  • Dry skin, dry mucus membranes, weight loss

  • Non-elastic skin turgor (skin tenting)

  • Decreased urine output and blood pressure (hypotension)

  • Increased heart rate (tachycardia); rise in temperature, weak pulse

  • Elevated BUN, creatinine, HCT, and urine specific gravity (renal system)

Treatment for deficient fluid volume

Oral and IV fluid (isotonic) replacement

Nursing management of fluid volume deficit

• I&O: measure all fluids that enter and leave the body

• Lab values: check electrolytes, CBC, and urine-specific gravity

• Cardiovascular: assess for hypotension and weak pulses

• Respiratory: assess respiratory system and tissue perfusion

• Assess: check orientation, vision, hearing, reflexes, and muscle strength

• Daily weights: check for weight changes

• Oral and skin care: check for skin breakdown and good oral care

• Watch closely for developing complications!

Hypervolemia

• excessive retention of sodium and water

  • Elevated blood pressure (more volume than needed), bounding pulse, JVD

  • Pale, cool skin (fluid goes to extracellular space)

  • Edema/ascites

  • Crackles/dyspnea

  • Weight gain (fluid buildup)

  • Hemodilution causes BUN, HCT, & urine specific gravity to decrease

Treatment for hypervolemia

Restrict sodium and fluids, consider diuretics

Ascites

Fluid in abdomen

How is pitting edema rated?

+1,+2,+3,+4

Routes for intake

• Oral

• NG tube

• Jejunostomy feeding (tube)

• IV fluids

Ways to measure output

• Urine

• Diarrhea

• Vomitus

• Gastric suction

• Blood

• Wound drainage

• Tube drainage

Lab studies

• Electrolytes

• CBC

  • hematocrit (elevated with dehydration)

• Creatinine

• BUN

• Urine specific gravity (decreased in fluid overload)

• Serum osmolality

• Urine osmolality

Main extracellular cation

Sodium

Your patient’s blood volume is low due to hemorrhage. What finding would you expect to see?

Increased heart rate

What type of patient is at risk for fluid volume excess?

Renal failure

Which assessment finding would you report as indicative of fluid volume excess?

Moist rales (crackles)

Neuro function is affected by dehydration. How would an elderly client present?

Altered mental status