chap. 35 - body fluids & electrolytes

body fluids functions

• transport nutrients to cells + wastes from cells

• transport hormones, enzymes, blood platelets, RBC, WBC

• facilitate cellular metabolism + proper cellular chemical functioning

• act as solvent for electrolytes + non-electrolytes

• help maintain body temp.

• facilitate digestion + promote elimination

• act as tissue lubricant

intracellular fluid (ICF)

fluid within cells

• 70% total body water

• 40% adults body weight

extracelullar fluid (ECF)

all fluid outside cells

• 30% total body water

• 20% adults body weight

• includes:

  • vascular (intravascular)

  • interstitial compartments

  • transcellular fluid compartment

vascular (intravascular)

fluid or plasma — liquid components of blood

interstitial fluid

fluid that surrounds tissue cells + includes lymph

transcellular fluid

includes cerebrospinal, pericardial, synovial, intraocular, pleural fluids, sweat, digestive secretions

third spacing

fluids move into an area that makes it physiologically unavailable

• occurs in peritoneal or pericardial space

what causes third spacing?

• severe infection

• trauma

• low plasma protein

• obstruction

• organ failure

• pancreatitis

• lymphatic blockage

third spacing symptoms

• low BP

• edema

• electrolyte imbalance

• feeling faint or dizziness

variations in fluid content

varies depending on age, body fat, biologic sex

• infants have more total body fat + ECF than adults

  • increased risk for fluid volume deficits b/c ECF is more easily lost than ICF

• women have less body fluid than men b/c women have more body fat

• older adults (after 60) have less percentage (45%) of body fluid

fluid balance

body obtains water from ingested fluids, food, as a byproduct of metabolism

• fluid intake via ingestion regulated by thirst mechanism in hypothalamus

• stimulated by dehydration, decreased blood volume

• water = end product of oxidation that occurs during metabolism of food especially carbs, fats, proteins

• average — fluid intake = 2,600 mL/day (1,500 mL from ingested liquids + 800 mL from ingested food + 300 mL from metabolic oxidation)

fluid loss

• sensible loss

• insensible loss

• average — 2,600 mL/day (1,500 mL from urine from kidneys + 400 mL from lungs + 600 mL from skin + 100 mL from feces via GI tract)

sensible loss

fluid lost during urination, defecation, wounds

• can be measured

insensible loss

fluid lost from evaporation through skin + water vapor from lungs during respiration

• cannot be measured or seen

electrolytes

substances that are capable of breaking into particles (ions)

• ions - atom or molecule carrying electrical charge

  • cations - ions w/ positive charge

  • anion - ions w/ negative charge (chloride, bicarbonate, phosphate — important in metabolism)

total cations normally = to total anions, maintaining homeostasis

non-electrolytes

molecules in body that remain intact + have no charge (urea, glucose)

ECF electrolytes

sodium, chloride, calcium, bicarbonate

ICF electrolytes

potassium, phosphorus, magnesium

osmosis

water passes from area of lesser solute concentration and more water → area of greater solute concentration and less water — until equilibrium reached

• volume of more concentrated solution increases

• volume of less concentrated (weaker) solution decreases

• major method of transporting body fluids

diffusion

tendency of solutes to move freely throughout solvent

• solute moves from area of HIGHER concentration → to area of LOWER concentration — until equilibrium reached

• gasses move by this method

• ex: gas exchange of oxygen + carbon dioxide in the lungs alveoli and capillaries

active transport

process that requires energy for movement of substances through a cell membrane, against concentration gradient

• area of LESSER solute concentration → to area of HIGHER solute concentration

• adenosine triphosphate (ATP) is stored in cells + supplies energy fro solute movement

• substances = amino acids, glucose, ions of sodium, potassium , hydrogen, calcium

capillary filtration

passage of fluid through a permeable membrane

• fluids move from area of HIGH PRESSURE → to area of LOW PRESSURE

• results from force of blood “pushing” against walls of capillaries

• “pushing” force = hydrostatic pressure

normal serum (blood) osmolality

280 mOsm/L

isotonic solution

solution that has osmolarity = to serum (blood)

• fluid remains in intravascular compartment w/o any net flow across the semipermeable membrane

hypotonic solution

solution that has less osmolarity than plasma

• due to low osmolality, the solution in the intravascular space moves out of the space and into ICF — causes cells to swell + burst

hypertonic solution

solution that has a greater osmolality then plasma

• water moves out of cells + is drawn into intravascular compartment — causes cells to shrink

isotonic IV fluid

total osmolality close to that of ECF — replace ECF

• 1st line resuscitation fluid

• 0.9% NaCl; lactated ringer’s

• has same osmolality as blood solutions → both sides of semipermeable membrane are = in concentration

  • expands ECF + ICF volume

  • expands blood volume w/o causing a shift from 1 compartment to another

• treats fluid volume deficit from:

  • hemorrhage

  • severe vomiting + diarrhea

  • heavy drainage from GI suction

  • fistulas + wounds

hypotonic IV fluid

[solution name] to plasma — replace ICF

• 0.33% NaCl; 0.45% NaCl → both 1/3 strength of NS

• a solution of lower osmotic pressure moves fluid into cells — causes cells to expand

  • shift ECF to ICF w/ decrease in ECF

• DO NOT USE for patients w/ increased intracranial pressure risk or 3rd spacing risk — increases fluid to brain cells + 3rd space

• can WORSEN existing hypovolemia + hypotension — fluid pulled out of IVC

• treats:

  • cellular dehydration (DKA)

  • HYPERnatremia (high Na+ serum) → dilutes plasma

hypertonic IV fluid

[solution name] to plasma

• 5% dextrose in LR solution

• a solution of higher osmotic pressure; pulls fluid from cells — causes cells to shrink

  • shift ICF to ECF w/ decrease ICF

• fosters normal BP + good urinary output (often use postoperatively)

• NOT USED for renal or cardiac disease → severe fluid volume overload + pulmonary edema!!!

• treats:

  • severe HYPOnatremia

  • syndrome of inappropriate antidiuretic hormone (SIADH) → high levels of hormone causing fluid retention

  • cerebral edema

hypothalamus

amount of fluid the body desires is monitored by thirst response

• controlled by [structure name]

• thirst receptors (osmoreceptors) continuously monitor serum osmolality

• if it rises → thirst mechanism triggered

pituitary regulation

[structure name] releases ADH in response to increasing serum osmolality

• causes renal tubules to retain H2O

• as water is retained in vascular space → vascular volume + BP increase

CV system

pumps fluid + nutrients throughout body

• secretes atrial natriuretic peptide (ANP) — hormone that regulates BP + sodium secretion

• when blood volume or BO is elevated to inhibit reabsorption of Na + H2O → decrease fluid volume + BP

lungs

regulate fluid by releasing water as vapor w/ every exhalation

small intestine

absorbs 85% to 95% of fluid from ingested food + delivers it to vascular system

kidneys

regulates fluid output

• filters 170 -180 L of plasma daily

• nephron receptors sense low osmolality + [organ] secretes renin — enzyme that helps control BP + healthy levels of Na & K

• released into bloodstream when BP drops too low

hypovolemia (fluid volume deficit)

loss of both H2O + electrolytes (mainly Na+) from ECF — isotonic fluid loss

what causes hypovolemia?

• severely decreased intake of H2O + salt

• increased output

  • loss of blood/plasma — hemorrhage, burns

  • GI losses — vomiting, diarrhea, tubes

  • renal losses — diuretic, diseases

  • profuse sweating/diaphoresis

• third spacing fluid shift → fluid shift out of vascular space into interstitial or transcellular spaces

  • pleural, peritoneal, pericardial areas, joint cavities, the bowel

hypovolemia: cardiovascular assessment

• decreased BP + orthostatic hypotension

• diminished peripheral pulses — quality 1+ (thready)

• tachycardia

• flat neck veins when supine

• elevated hematocrit (Hct) — hemoconcentration

hypovolemia: GI assessment

• thirst

• decreased motility; diminished bowel sounds

• possible constipation

hypovolemia: neuromuscular assessment

• decreased CNS activity — restlessness, confusion, lethargy

• possible fever

• skeletal muscle weakness

• hyperactive DTR

hypovolemia: renal assessment

• decreased output — oliguria, anuria

• increased urine specific gravity → normal SG = 1.015 -1.025

• weight loss

hypovolemia: integumentary assessment

• dry mouth, oral mucosa, skin

• poor turgor

• sunken eyeballs

• third-spacing signs — swelling in abdomen, low urine output, tachycardia weight gain, electrolyte imbalance, decreased body temp.

hypovolemia: respiratory assessment

increased RR (tachypnea)

hypovolemia interventions

• prevention

• oral rehydration therapy (fluid containing Na+)

• IV therapy

• monitor electrolytes — possible supplement treatment

• medications — antiemetics, antidiarrheals

• monitor HR + BP — postural BP changes

• monitor respiration, renal, GI status

• assess for signs of hypovolemic shock

• assess skin + maintain skin integrity

• monitor daily weights (most effective) + strict I&O

hypervolemia (fluid volume excess)

excessive retention of water + sodium in ECF in intravascular compartments

what causes hypervolemia?

• excessive water + sodium intake (PO or IV)

• malfunction of kidneys (renal failure)

• failure of the heart to pump (CHF)

edema

excessive ECF in interstitial spaces

• can be seen around eyes, fingers, ankles, sacral spaces

• can accumulate in or around body organs

• graded from 1-4

• types of edema:

  • localized

  • generalized → anasarca

  • third spacing → ascites, pitting edema, pulmonary edema

hypervolemia: cardiovascular assessment

• elevated pulse + bounding

• elevated BP

• distended neck + hand veins

• ventricular S3 gallop

hypervolemia: GI assessment

• increased motility

• stomach cramps

• N/V

hypervolemia: neuromuscular assessment

• altered LOC

• headache

• skeletal + muscle twitching

hypervolemia: renal assessment

• weight gain

• increased urine output

hypervolemia: integumentary assessment

• periorbital edema

• pitting or non-pitting edema

hypervolemia: respiratory assessment

• dyspnea/SOB

• tachypnea

• crackles

hypervolemia interventions

• low sodium diet

• decrease water intake

• diuretics — furosemide, bumetanide

• IV hypertonic therapy — albumin

• avoid constricting clothing

• exercise

• TEDS, pneumatic compression stockings

• protect from injury

• keep skin clean + dry

• increase protein intake

• semi-fowlers postion

• accurate I&O

• DAILY WEIGHTs

• monitor electrolytes

sodium (Na) range

135-145 mEq/L

sodium (Na)

role in muscle contraction + transmission of nerve impulses

• chief electrolyte in ECF + regulates ECF volume

• normally enters through GI tract

• lost from GI tract, kidneys, skin

• sources = table salt, soy sauce, processed food, canned products, cured pork

hyponatremia

sodum deficit; <135 mEq/L

• decrease in sodium causes fluid to move by active transport from less concentrated ECF to ICF — causes cells to swell

whats causes hyponatremia?

• diuretics

• GI fluid loss

• excessive hypotonic solutions (D5W) IV fluids

hyponatremia s/s

• confusion

• lethargy

• edema

• muscle craps

• dry skin

• weakness

• N/V

• severe:

  • increased intracranial pressure

  • muscle twitching

  • hyperreflexia

  • coma

  • seizures

  • death

hyponatremia treatment

• for NA loss = replace sodium — usually IV NS

• for water gain = restrict fluid

• for neuro signs/severe = 3% or 5% NS IV slowly to prevent fluid overload

• TREAT THE CAUSE

hyponatremia interventions

• monitor I&O

• monitor sodium levels

• increase oral sodium intake

• seizure precautions

hypernatremia

excess of sodium in ECF; >145 mEq/L

• fluid moves from cells, leaving cells w/o sufficient fluid — causes cells to shrink

what causes hypernatremia?

• excess water loss or excess sodium intake

• fluid deprivation

• lack of fluid consumption

• diarrhea

• insensible water loss — hyperventilation, burns

hypernatremia s/s

• thirst

• elevated temp.

• dry mouth

• restlessness

• severe:

  • hallucinations

  • irritability

  • lethargy

  • seizures

  • permanent brain damage

hypernatremia treatment

• for water loss = D5W IV, 0.45% NS to prevent swing to hyponatremia

• for excess sodium = restrict sodium intake

• TREAT THE CAUSE

hypernatremia interventions

• monitor I&O

• monitor serum levels

• monitor vital signs + LOC

• restrict sodium

• increase water intake

potassium (K) range

3-5-5.0 mEq/L

potassium (K)

regulates conduction of cardiac rhythm

• transmits electrical impulses in multiple body systems

• major cation of ICF

• assists / acid-base balance

• excreted by kidneys

• sources = bananas, oranges, figs, dates, potatoes, spinach, meats, dairy products

hypokalemia

potassium deficit in ECF; <3.5 mEq/L

• when there is a drop in K in ECF, K leaves cells, creating intracellular potassium deficiency

what causes hypokalemia?

• GI loss

• anorexia or bulimia

• diuretics

hypokalemia s/s

• muscle weakness

• leg cramps

• fatigue

• N/V

• decreased GI motility

• dysrhythmias

• elevated U waves + flattened T waves

hypokalemia treatment

administer potassium supplements (PO or IV)

hypokalemia interventions

• monitor I&O

• monitor potassium levels

• repeat K levels post replacement

• monitor urine output

• encourage foods high in potassium

hyperkalemia

excess of K in ECF; >5 mEq/L

what causes hyperkalemia?

• renal failure

• medications — KCL, heparin, ACE inhibitors, NSAIDS, potassium sparing diuretics

• major trauma

hyperkalemia s/s

• muscle weakness

• nausea

• diarrhea

• abdominal cramps

• cardiac dysrhythmias

• peak T waves

• prolonged PR interval
  flattened P waves

• depressed ST segment

• dangerous = cardiac arrest

hyperkalemia treatment

• 10% calcium gluconate → stabilize cardiac cell membranes

• IV insulin + dextrose → facilitates uptake of glucose into cells — intracellular shift of K into cells

• loop diuretics

• dialysis

hyperkalemia interventions

• monitor potassium levels

• restrict potassium intake

• monitor vital signs

• cardiac monitoring

potassium administration factors

• check urine output

• monitor IV site for phlebitis

• place on cardiac monitor ir >10 mEq/hr

• infuse via infusion pump

• assure of adequate mixing of K in solution

• monitor for elevated K levels

• monitor for decreased Na levels

• NEVER administer potassium by slow IV push method

calcium (Ca) range

8.5-10.5 mg/dL

calcium (Ca)

role in transmission of nerve impulses + blood coagulation & regulates muscle contraction/relaxation

• major component of bones + teeth

• excreted by GI tract

• absorbed from foods + vitamin D

• sources = milk, milk products, dark green leafy vegetables, small fish w/bones, beans

hypocalcemia

calcium deficit in ECF; <8.5 mg/dL

what causes hypocalcemia?

• inadequate Ca intake

• impaired Ca absorption

• excessive Ca loss

• vitamin D deficiency

hypocalcemia s/s

• numbness + tingling of fingers, mouth, feet

• tetant

• diarrhea

• muscle cramps

• seizures

• laryngospasm

• positive trousseau’s

• positive chvostek’s

hypocalcemia treatment

replace calcium — IV calcium gluconate

hypocalcemia interventions

• seizure precautions

• emergency airway equipment

• Ca + vitamin D rich diet/supplements

• monitor serum calcium levels

trousseau’s sign

sign of latent tetany

• inflate manual BP cuff around upper arm to a pressure higher than patients baseline SBP for 3 mins

• positive = flexion & adduction of fingers + wrists

chvostek sign

twitch of facial muscles that occurs when patients cheek is tapped

• test elicits atypical reaction of cranial nerve VII (facial nerve)

• gently tap cheek 2 cm. in front of ear, over facial nerve

• positive = twitching of mouth + periorbital muscles on side that was tapped

hypercalcemia

excess Ca in ECF; >10.5 mg/dL

• severe = >15 mg/dL — EMERGENCY

what causes hypercalcemia?

• cancer

• hyperparathyroidism

• prolonged immobilization

• excess calcium supplements

hypercalcemia s/s

• muscle weakness

• N/V

• constipation

• bone pain

• polyuria

• renal calculi

• polydipsia

• confusion

• lethargy

• slurred speech

• bradycardia

hypercalcemia treatment

• IV therapy — NS or IV phosphate

• loop diuretics

• dialysis

hypercalcemia interventions

• limit dietary Ca intake

• increase fluid intake to prevent kidney stones

• monitor for kidney stones

• avoid calcium-based antacids

• encourage fiber intake

magnesium (mg) range

1.3-2.3 mEq/L

magnesium (mg)

metabolism of carbohydrates + proteins — acts on cardiovascular system, producing vasodilation

• most abundant intracellular cation after potassium

• enters body via GI tract

• lost via urine w/ use of loop diuretics — eliminated by kidneys

• sources = green leafy vegetables, nuts, whole grains

hypomagnesemia

magnesium deficit in ECF; <1.3 mEq/L

what causes hypomagnesemia?

• nasogastric suction

• diarrhea

• chronic alcohol use

• tube feedings or parenteral nutrition

• sepsis

• diabetic ketoacidosis (DKA)

hypomagnesemia s/s

• muscle weakness

• tremors

• tetany

• seizures

• cardiac arrhythmias

• change in mental staus

• hyperactive DTR

• respiratory paralysis

hypomagnesemia treatment

IV magnesium sulfate

hypomagnesemia interventions

• offer magnesium rich foods

• monitor for dysphagia

• avoid alcohol intake

• seizure precautions