fluid and electrolyte
capillary oncotic pressure
(pulling water into the capillary)
Capillary hydrostatic pressure
(pushing water out of capillary)
total intake of water
2,500 mL
Normal serum osmolarity
275 to 295 milliosmoles/liter (mOsm/L)
Antidiuretic hormone (ADH) is triggered by:
A drop in BP or blood volume A rise in blood osmolarity (increased concentration) Causes kidneys to reabsorb more water resulting in: higher vascular volume; and low output of concentrated urine
Cardiac peptides
Atrial Natriuetic Peptide (ANP) Brain Natriuetic Peptide (BNP)
Transcellular
CSF, GI, ocular, etc., can become pathological as in ascites "third space"
Starling forces- out:
Capillary hydrostatic pressure Interstitial oncotic pressure
ANP lowers blood volume and BP by:
Causing vasodilation by direct effect on blood vessels and suppression of renin-angiotensin system Decreasing aldosterone release by adrenal glands, causing increased urinary excretion of sodium and water Decreasing ADH release by pituitary gland, causing increased urinary excretion of water Increasing glomerular filtration rate, increasing rate of urine production and water excretion
Starling's Law of the Capillaries
Filtration (net fluid movement into or out of the capillary) is determined by the difference between the forces favoring filtration and those opposing it (tug of war) Interstitial hydrostatic pressure pushes water into the capillary and Interstitial oncotic pressure pulls water out of the capillary (this is very low pressure- little movement of water) Capillary hydrostatic pressure (pushing water out of capillary) and capillary oncotic pressure (pulling water into the capillary)
Age related considerations
Full term baby 80% water Older adult 40% water
Atrial Natriuetic Peptide (ANP)
Hormone released as a result of atrial stretch
Brain Natriuetic Peptide (BNP)
Hormone released with ventricles as a result of ventricular stretch
Movement of fluids
Hydrostatic pressure Osmotic pressure
ICF
Intracellular fluids
Renin-Angiotensin-Aldosterone System
Hypovolemia (low blood pressure) into kidney renin out of kidney angiotensin 1 angiotensin 2 -retention of Na+ by kidney via aldosterone -water retention by kidney (via Na+ uptake and vasopressin -salt appetite -increased drinking (via subfornical organ) -increased blood pressure
ISF
Interstitial fluids
IVF
Intravascular fluids
Fluid regulation body systems
Kidney Sodium (mainly) and other electrolyte levels Antidiuretic hormone (ADH) Stimulates water conservation and the thirst center Aldosterone Controls Na+ absorption and K+ loss along the descending convoluted tubules and Collecting duct Natriuretic peptides (ANP and BNP) Reduce thirst and block the release of ADH and aldosterone Baroreceptors Proteins and Starlings forces in the capillary
Oncotic pressure
Oncotic pressure, also called 'colloid osmotic pressure', is the 'pulling force', pulling fluids from the surrounding tissue into the capillaries. It's the result of a difference in the concentration of solutes in the fluid inside the capillaries as opposed to outside them.
Fluid and electrolyte movement
Osmosis - (osmotic/oncotic pressure) Diffusion Hydrostatic pressure Filtration Active transport
Starling Forces- in:
Plasma oncotic pressure Interstitial hydrostatic pressure
Aldosterone
Released and inhibited by feedback loop as part of renin-angiotensin-aldosterone system
Renal regulation of fluids
Renin activation of RAAS Solute concentration and dilution Protein conservation Acid-base balance Waste excretion
Antidiuretic hormone (ADH) is inhibited by
Rise in BP or blood volume Drop in blood osmolarity (decreased concentration) Causing the kidneys to excrete more water in the urine. Resulting in: Lower vascular volume; and High output of dilute urine
What is the major solute in plasma?
Sodium (so can estimate 2 x serum sodium = osmo)
Solution
The liquid
hydrostatic pressure
Think of hydrostatic pressure as the 'pushing force', pushing the fluid out of the capillaries. It's the result of the actual pressure of the fluid on the capillary walls.
TBW
Total Body Water
Urine Constituents output? contains? pH?
Urine output = 1-2 L/day Protein free Contains: Electrolytes Glucose Bicarbonate Urea Creatinine pH = 4.6-8.0 is normal
BNP lowers blood volume and BP by:
Vasodilating arteries and veins Decreasing release of aldosterone Causing diuresis with excretion of both sodium and water
As fluid leaves the capillaries as a result of hydrostatic pressure...
albumin and other large proteins cannot pass through the capillary walls. This results in a greater concentration of solutes inside the capillaries, and the oncotic pressure rises, pulling more water into the capillaries.
Water follows sodium d/t osmosis, thus
aldosterone has an indirect effect on water
Blood Urea Nitrogen (BUN) and Glucose
also contribute to osmolarity
Extracellular Fluid (ECF) volume depends cheifly upon
concentration of sodium ions
An increase in Na+ in plasma? Thus we will have:
fluid will be pulled from interstitial and intracellular compartments into plasma. hypervolemia (plasma) compartment hypovolemia or dehydration of the interstitial and intracellular compartments
Whenever the oncotic pressure is greater than the hydrostatic pressure
fluid will enter the capillaries.
Whenever hydrostatic pressure is greater than oncotic pressure...
fluid will leave the capillaries.
A decreases in Na+ in plasma? Thus we will have:
fluid will move from plasma into interstitial and intracellular compartment. hypovolemia (of plasma) compartment hypervolemia of interstitial and intracellular spaces
Neutral balance
input = output
Positive balance
input > output
Negative balance
input< output
Interstitial oncotic pressure
pulls water out of the capillary (this is very low pressure- little movement of water)
Interstitial hydrostatic pressure
pushes water into the capillary
Adrenal Gland hormone that conserves sodium (NA+) in the body by causing the kidneys to:
retain sodium; and excrete potassium (K+)
Fluid compartments
separated by semi permeable membranes
Solute
substance dissolved in a liquid
Osmolarity
the concentration of solute in a fluid (mostly sodium) per KILIGRAM of WATER