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