Fluid and Electrolytes

determinants of BP homeostasis

cardiac output, vascular resistance, blood viscosity, fluid volume

humans are what percentage of water

55

fat is what percentage of water

10

muscle is what percentage of water

75

rank tissues from least to most amount of water

bone, fat, muscle, blood

categories of fluid management

cellular fluid transport, compartmental fluid transport, total body fluid management

definition of cellular fluid transport

how individual cells maintain homeostasis of fluid volume and electrolyte concentration through control of solutes/solvent concentrations across cell membranes

types of cellular transport

active and passive

characteristics of active cellular transport

requires ATP, needs a pump

characteristics of passive cellular transport

no energy expenditure or ATP required, based on concentration gradient

processes used by kidney to balance fluid and electrolytes

simple diffusion and osmosis (passive processes)

characteristics of simple diffusion

movement of solutes, movement down concentration gradient, through permeable membrane

goal of passive cellular transport

equilibrium of fluid and electrolytes

determinants of the speed of diffusion

steepness of concentration gradient, size of solute molecule, temperature

characteristics of osmosis

solvent moves, through semi-permeable membrane, down osmotic pressure gradient

hypertonic solution

higher solute concentration relative to the inside of the cell (causes shrinkage)

hypotonic solution

lower solute concentration relative to the inside of the cell (causes swelling)

cause of hemolysis

cell is placed in a hypotonic solution and takes in water which causes it to swell and burst

what determines the flow of fluid in and out of cells

the tonicity of the fluid

tonicity of intravenous fluids

isotonic (0.9%)

situations where active cellular transport is required

solute molecule is too large, contains an electrical charge, moving against the gradient

primary active transport

integral protein pump powered by ATP

examples of primary active transport pumps

sodium/potassium pump, proton pump

function of sodium/potassium pump

keeps intracellular low Na and high K to allow for nerve impulse transmissions

function of proton pumps

establish the concentration gradients to maintain stomach scidity

compartmental fluid transport

maintenance of homeostasis between intracellular/extraceellular and intravascular/interstitial space

solute concentration in intracellular fluid

low sodium and high potassium

types of extracellular fluid

intravascular, interstitial, transcellular

interstitial fluid

fluid between cells that is not in vessels

transcellular fluid

pathologic fluid in a potential body space (ex: pericardium)

solute concentration in extracellular fluid

high sodium and low potassium

percentage of body water in intracellular and extracellular spaces

intra: 40%, extra: 20% (interstitial: 14%, plasma: 5%)

function of interstitial fluid

provides a reserve to support the circulatory system when there is a hemorrhage or circulatory collapse

what determines the direction the intravascular/interstitial fluid shift

hydrostatic and osmotic pressure

hydrostatic pressure

force exerted by the fluid inside capillaries against the wall (actual BP)

oncotic pressure

type of osmotic pressure exerted by the presence of proteins in the intravascular space

colloid oncotic pressure

force exerted by albumin and other proteins in the blood vessels

what causes reabsorption

higher relative amounts of solutes in the intravascular space will draw fluids in

filtration

movement of fluid out of vascular space into interstitial space

reabsorption

movement of fluid out of interstitial space into the vascular space

vascular permeability

damage to endothelium allows for heightened leaking into the interstitial tissue

lymphatic drainage

promotes reabsorption of excess interstitial tissue fluid accumulation

edema

excess bodily fluid often visible/palpable in the interstitial tissues

causes of edema

increased capillary hydrostatic pressure, decreased colloid osmotic pressure, increased capillary permeability, lymphatic disruption (things that favor filtration)

things that increase hydrostatic pressure

gravity, heat, hypertension

things that decrease colloid osmotic pressure

starvation, burns, liver and renal failure

things that increase capillary permeability

inflammatory reactions

cause of lymphedema

lymphatic system is damaged, blocked, or not developed

causes of transcellular fluid accumulation

low oncotic pressures (liver failure → low albumin), high hydrostatic pressure (heart failure → high intravascular pressure)

total body fluid management

maintenance of homeostasis of effective circulating volume (fluid intake/output balance)

daily baseline intake requirements

women: 3 L, men: 4 L

where does the body lose water

kidney filtration and urine (also GI tract, skin, lungs)

characteristics of sodium

largest cation, mostly in extracellular fluid, driven by Na/K pump

effective circulating volume

blood volume contained within the entire circulatory system

how is ECV maintained

monitoring and feedback systems

ECV feedback effectors

sympathetic nervous system and hormone paths

ECV feedback receptors

baroreceptors in the atrium, pulmonary vessel walls, aortic arch, and carotid sinushorm

hormones that help kidneys eliminate water

ANP

hormones that help kidneys retain water

renin-angiotensin-aldosterone, ADH

function of ANP

lowers circulatory volume and pressure

function of renin-angiotensin-aldosterone system

increase sodium absorption which leads to water retention

function of ADH

increase blood volume and blood pressure

definition of electrolytes

minerals in the blood that carry an electric charge

function of electrolytes

balance blood acidity, muscle function, nerve conduction, control amount of water

parts of basic metabolic profile (BMP)

electrolytes: Na, K, Cl, HCO3; kidney: BUN, CR; glucose

function of sodium

acid-base balance, contributes to function of nervous and muscular system

location of potassium

contained in intracellular compartment

function of potassium

conducts nerve impulses and excites cardiac muscle

effects of derangement of potassium

muscle cramping, dysrhythmia

effects of derangement of sodium

confusion, lethargy, seizures, lightneadedness, edema, heart failure

types of calcium

bound/un-ionized (40%) and free/ionized (60%)

where is bound calcium

bound to circulating albumin

where is unbound calcium

participates in cellular function

what controls the calcium level

parathyroid, calcitonin, kidney retention/elimination

function of parathyroid hormone

stimulates osteoclasts to breakdown bone and release calcium to raise levels

function of calcitonin

inhibits osteoclasts to tone down calcium levels

function of vitamin d

converted into calcitrol by UV radiation which increases calcium absorption