homeostasis and fluid balance

what is intracellular fluid (ICF)?

fluid inside cells

what is extracellular fluid (ECF)?

all fluid outside cells

diffusion, osmosis, active transport function

shift fluid and electrolytes between compartments

who regulates how fluid moves?

kidneys

lungs

endocrine system

renin-angiotensin system (RAAS)

how do kidneys regulate?

filter blood

control water/waste retention vs. excretion

fluid and electrolyte balance

how do the lungs regulate?

regulate pH during respiration (O2 in, CO2 out)

how does the endocrine system regulate?

releases hormones regulating metabolism, glucose, stress, and fluid balance

how does the renin-angiotensin system (RAAS) regulate?

hormone pathway that maintains stable BP and fluid volume

what is the purpose of electrolytes?

create the osmotic gradients and electrical charges that move water and drive nerve/muscle function

list the 7 essential electrolytes

sodium

potassium

calcium

chloride

magnesium

phosphate

bicarbonate

sodium function

most abundant in ECF

fluid balance, nerve signals, muscle contraction, osmosis

potassium function

most abundant in ICF

nerve signaling, muscle contraction, heart function

calcium function

bone mineralization, muscle contraction, clotting, nerve transmission

chloride function

fluid balance, nerve signals, muscle contraction

regulated by the kidneys

magnesium function

helps K+ move in/out of the cells

ATP metabolism

muscle relaxation

phosphate function

key ATP component

enzymatic function

DNA/RNA formation

bicarbonate function

maintains acid-base balance by regulating blood pH

🍌fluid intake routes

oral intake is primary (liquids + high-water foods)

also IV routes and enteral feeding

🍌what is fluid intake affected by?

age

diet

environment

medications

social determinants of health

🍌fluid distribution

capillaries are the main exchange site (diffusion and osmosis)

lymphatic system returns excess interstitial fluid to bloodstream

🍌fluid excretion route

urine; also bowel, skin, lungs (sensible vs. insensible loss)

🍌hormones associated with fluid excretion

ADH: INC water reabsorption

aldosterone: INC sodium reabsorption

ANP: promotes excretion; opposes ADH and aldosterone

effects of hypovolemia in the cardiovascular system

DEC BP, DEC cardiac output

effects of hypervolemia in the cardiovascular system

INC BP, heart works harder

effects of hypovolemia in the renal system

DEC perfusion

concentrated urine

risk of AKI (acute kidney injury)

effects of hypervolemia in the renal system

edema

dilute urine

risk of CKD (chronic kidney disease)

effects of hypovolemia in the neurological system

DEC cerebral perfusion → confusion, dizziness

effects of hypervolemia in the neurological system

cerebral edema → INC ICP (intracranial pressure)

effects of hypovolemia in the respiratory system

thick secretions

risk of atelectasis

effects of hypervolemia in the respiratory system

pulmonary edema

risk of hypoxia

🍌how is acid-base homeostasis acheived?

kidneys and lungs work together to keep blood pH stable

🍌kidneys function in acid-base homeostasis

conserve or excrete hydrogen ions and bicarbonate

🍌lungs function in acid-base homeostasis

regulate CO2 levels, which drive carbonic acid formation

🍌assessing fluid status

history (age, diagnoses, medications, diet, activity, bowel/bladder patterns)

physical exam (vital signs, respiratory + cardiac findings, edema, skin turgor, mucous membranes)

I&O (intake and output) + labs (careful measurement plus lab results complete the picutre)