fluid + electrolyte balance Flashcards
three fluid compartments of the body
- intravascular (fluid in blood vessels)
- intracellular (fluid in cells, most body fluid is here)
- extracellular (interstitial fluid between cells - blood, lymph bone, connective tissue, water, transcellular fluid)
what is it?
third-spacing
extracellular fluid is trapped in a body space (pericardial, abdominal, peritoneal, joint cavity, bowel, abdomen, soft tissues) from trauma or burns
trapped fluid is a volume loss + unavailable for normal physiological processes
what is it and what causes it?
edema
accumulation of fluid in interstitial space from alterations in oncotic pressure, hydrostatic pressure, capillary permeablility, or lymphatic obstruction
- localized is from trauma (accident, surgery, local inflammatory process, burns)
- generalized is from cardiac + renal conditions or liver failure
what are the processes that move fluid?
body fluid transport
- diffusion: solute/dissolved substance moves from high to low concentration
- osmosis/osmotic pressure: solvent moves from low to high concentration
- filtration: movement of solutes and solvents from high to low pressure
- hydrostatic pressure: force exerted by weight of solution
- osmolalility/osmotic pressure: number of osmotically active particles, concentration of solution (plasma is 275-295 mOsm/kg)
solution types
high, equal, low concentrations
- isotonic : equal concentration on both sides of membrane
- hypotonic : lower osmolality than body fluids - hypotonic to cells
- hypertonic : higher osmolality than body fluids)
what is it?
active transport
movement of molecules or ions against concentration
substances transported actively: sodium, potassium, calcium, iron, hydrogen, amino acids
sources of fluid intake
ingested liquid, foods, water formed by oxidation of foods
sources of fluid loss
skin, expired air from lungs, kidneys, GI tract
isotonic dehydration
water loss = electrolyte loss (hypovolemia)
decreased blood volume and perfusion
caused by:
* not enough intake
* fluid shift
* excessive loss of isotonic body fluids
hypertonic dehydration
more water is lost than electrolytes, water moves out of cells into plasma (makes cells shrink)
caused by:
- too much sweating
- hyperventilation
- ketoacidosis
- prolonged fevers
- diarrhea
- early kidney disease
- diabetes insipidus
hypotonic dehydration
more electrolytes lost than water, water moves into cells (makes cells swell)
caused by:
- chronic illness
- excessive fluid replacement
- kidney disease
- chronic malnutrition
isotonic overhydration
too much isotonic fluid in extracellular space, hypervolemia or circulatory overload
caused by:
- IV therapy
- kidney disease
- long term corticosteroid therapy
hypertonic overhydration
too much sodium
caused by:
- excessive sodium intake
- hypertonic saline
- excessive sodium bicarb
hypotonic overhydration
water intoxication, all fluid compartments expand and electrolytes dilute
caused by:
- early kidney disease
- heart failure
- syndrome of inappropriate ADH secretion
- replacing isotonic fluid loss with hypotonic fluids
- irrigation of wounds and body cavities with hypertonic fluids
function + how it’s regulated
potassium
- fluid balance (main ICF ion)
- acid-base balance
- nerve impulse transmission (maintains resting membrane potential)
- maintains normal cardiac rhythms
- muscle contraction
~ mostly regulated by kidneys
normal = 3.5 - 5.0 mmol/L
causes + interventions
hypokalemia
causes:
* meds (diuretics, corticosteroids, albuterol)
* too much aldosterone
* vomiting/diarrhea
* wound drainage (mostly GI)
* prolonged NG suction
* excessive sweating
* kidney disease (can’t reabsorb)
* fasting/NPO
* potassium movement into cells (alkalosis, hyperinsulinism)
interventions:
* supplements (oral can cause nausea/vomiting on empty stomach)
* IV administration (can cause phlebitis)
causes + interventions
hyperkalemia
causes:
* excessive intake
* potassium-sparing (retaining) diuretics
* kidney disease
* adrenal insufficiency
* movement of potassium out of cells (tissue damage, acidosis, hyperuricemia, hypercatabolism)
interventions:
* potassium-excreting diuretics (if renal function is good)
* if renal function impaired - give sodium polystyrene sulfonate (promotes GI absorption of sodium and potassium excretion)
* if K+ is critically high - IV calcium (to avert myocardial excitability) or dialysis
* hypertonic glucose with insulin to move potassium into cells
pseudohyperkalemia can occur due to methods of blood collection and cell lysis, new specimen would be needed
function + regulation
sodium
- water balance (regulates the ECF osmotic forces/blood pressure)
- nerve impulse conduction
- acid-base balance
~ regulated by aldosterone (promotes sodium/water reabsorption + potassium excretion)
normal = 135 - 145 mmol/L, accounts for 90% of ECF cations
causes + interventions
hyponatremia
causes:
* increased excretion (excessive sweating, diuretics, vomiting/diarrhea, wound drainage, kidney disease, low aldosterone)
* not enough intake (NPO, fasting, low-salt)
* dilution of serum sodium (excessive ingestion or irrigation with hypotonic fluids, freshwater drowning, syndrome of inappropriate antidiuretic hormone secretion, hyperglycemia, heart failure)
interventions:
* IV sodium chloride
* osmotic diuretics for water excess
* monitor neuro status for osmotic demyelination if hyponatremia is corrected too fast
causes + interventions
hypernatremia
causes:
* decreased sodium excretion (corticosteroids, Cushing’s, kidney disease, hyperaldosteronism)
* increased intake
* not enough water (NPO, fasting)
* increased water loss (increased metabolism, fever, hyperventilation, infection, too much sweating, diarrhea, diabetes inspidus)
function + regulation
calcium
- bone/tooth formation
- blood clotting cofactor
- nerve impulses
- muscle contraction
~ regulated by parathyroid hormone, vitamin D, calcitonin (act together to control calcium absorption/excretion)
normal serum: 2.25 - 2.75 mmol/L
causes + interventions
hypocalcemia
caused by:
* GI tract can’t absorb (lactose intolerance, celiac, Crohn’s, lack of vitamin D, end-stage kidney disease)
* increased excretion (kidney disease, diarrhea, wound drainage)
* conditions that decrease ionized fraction of calcium (hyperproteinemia, alkalosis, calcium binders, pancreatitis, hyperphosphatemia, parathyroid gland removal)
interventions:
* supplements
* aluminum hydroxide (reduces phosphorus = countereffect of increasing calcium)
* vitamin D helps intestines absorb calcium
causes + interventions
hypercalcemia
caused by:
* too much calcium/vitamin D intake
* decreased excretion (kidney disease, thiazide diuretics)
* increased bone resorption (hyperparathyroidism, hyperthyroidism, malignancy that destroys bone, immobility)
interventions:
* diuretics to increase calcium excretion
* medications that stop calcium resorption from bone (phosphorus, calcitonin, biphosphonates, prostaglandin synthesis inhibitors)
* monitor for fracture, urinary stones
function + regulation
magnesium
- cofactor for many enzymes
- nerve impulse transmission
- muscle contraction
~ absorbed by intestines + eliminated by kidneys
normal: 0.74 - 1.07 mmol/L
causes + interventions
hypomagnesemia
caused by:
* not enough intake (vomiting, diarrhea, celiac, Crohn’s)
* increased excretion (diuretics, chronic alcohholism)
* intracellular movement (hyperglycemia, insulin, sepsis)
interventions:
* magnesium sulfate IV (oral can cause diarrha)
causes + interventions
hypermagnesemia
caused by:
* increased intake (antacids/laxatives containing magnesium)
* renal insufficiency
interventions:
* calcium gluconate IV (antidote for Mg overdose)
* calcium chloride
* diuretics
function + regulation
phosphate
- bone formation
- muscle contraction (provides energy as ATP)
- acid-base balance
~ regulated by parathyroid hormone, vitamin D, calcitonin (act together to control absorption/excretion)
normal: 0.97 - 1.45 mmol/L
causes + interventions
hypophosphatemia
caused by:
* malnutrition/starvation
* increased excretion (hyperparathyroidism, malignancy, magnesium/aluminum hydroxide based anatacid)
* intracellular shift (hyperglycemia, respiratory alkalosis)
interventions:
* phophorus supplement with vit D
* phosphorus IV
causes + interventions
hyperphosphatemia
caused by:
* decreased renal excretion
* tumor lysis syndrome
* increased intake
* hypoparathyroidism
interventions:
* phosphate-binding meds to increase excretion
