1750: Fluid & Electrolytes
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Body fluid distribution:
What amount is intracellular and what amount is extracellular (interstitial, intravascular)
60% of total weight
- Within this fluid:
- Intravas: 2/3 (plasma)
- Interstitial: lymph fluid
- Extra: 1/3
What are some functions of water?
- Chemical processes
- Lubrication & Insulation
Total Fluid Volume.
What is it influenced by?
Amt of body fat
- Gender (Females < Men)
- Age (older adults < younger adults)
- Amount of body fat (women > men = less water)
What are the values for:
- Mg++: 1.5-2.5 mEq/L
- HPO4-: 2.5-4.5 mEq/L
- K+: 3.5-5.0 mEq/L
- Ca++: 8.5-10.5 mEq/L
- Cl-: 95-108 mEq/L
- Na+: 135-145 mEq/L
- HCO3-: 22-26
Major Functions of Electrolytes.
Which electrolytes aid in maintaining:
acid base enzyme reactions
nerve conduction or neuromuscular reactions?
Fluid balance: Na, Cl-serum osmol.
Acid-Base regulation: Cl-, HCO3-
- Facilitate enzyme reactions: Mg-protein & DNA synthesis in cells.
- Phosphorus: chemical actions; Ca++
- Nerve conduction or neuromuscular reactions:
- K+: HEART function
- Ca++: cardiac, neuromuscular
Movement of fluids in the body.
Name some small versus large solutes and if they move easily or difficult.
What do large molecules need?
Small: O2, CO2, ions. Move easily.
Large: protein, glucose. Move w/ more difficulty; NEEDS active transport.
What is Osmosis?
Only solvent (fluid) moves from low solute to high solute (low->high concentration)
What is Tonicity AND what does it promote?
e.g., hyper, hypo, iso -tonic
Ability of solutes (electrolytes) to cause an osmotic DRIVING force; promotes movement of water.
Oncotic pressure versus Osmotic pressure
(what molecules cause the pressure?)
AKA: Colloid Osmotic Pressure (COP)
Oncotic pressure caused by albumin (protein); in a BV's plasma (ECF/intravas) that usually pulls water (fluid) into the circulatory system (e.g., peripheral edema).
It helps move water from interstitial to intravascular compartments.
Osmotic pressure: pressure needed to move fluid across the membrane.
What is it? What moves?
What does the rate depend on? (3)
Random movement of molecules from higher concentration to lower concentration.
*movement of solutes.
- Rate depends on:
- Size: large slower than smaller
- Concentration: high -> low
- Temp: hotter = faster
What is it?
What pressure is used?
Water&solutes move together across the membrane from higher -> lower pressure.
Hydrostatic pressure: exerts on BV walls.
To achieve homeostasis, which 3 pressures need to be functioning?
Briefly explain Hydrostatic VS Osmotic pressures.
Osmotic (pull force), Oncotic (aka COP), and hydrostatic pressure (BP push force).
Hydrostatic pressure is caused by the flow of blood through vessels; it is the "push" force from within on the vessel walls.
Osmotic pressure is the pressure exerted on the vessel from the OUTSIDE (pull force) by the interstitial fluid. At the arteriole (closer to the heart) end of a vessel, hydrostatic pressure is greater than osmotic pressure, so fluid from the vessel leaks out. Thus, as you approach the venus end of that vessel, since fluid leaked out of the vessel before (and because you are farther away from the heart), the osmotic pressure is now greater than the hydrostatic pressure, so most of the fluid is pulled back into the vessel (intravascular space).
Fluid & Electrolyte Regulation.
Primary regulators for intake: Kidneys; thirst (center located in hypothalamus)
Output: What 3 outputs (mechanisms) regulate the output?
Explain their functions.
Input: thirst (center located in hypothalamus)
- ADH - Holds urine; secreted by posterior pituitary gland (Na+/H2O absorption)
- RAAS - restore blood via Na+ and H2O retention.
- Ex: Low BP = released Renin and converts angiotensinogen to angiotensin I. ACE converts I to II causing vasoconstriction and promotes Na+ & H2O retention.
Atrial Natriuretic Factor:hormone found in atrium released in response to increased blood volume & stretching of atrial walls --> promotes Na+ excretion resulting in water loss also (diuretic).
Intake & Output.
Adults need how many mL/day?
Adults need 2,500 mL/day.
Urine 1 mL/kg/hr
Age-related variations in fluids & electrolyte balance.
Peds vs Elders?
- immature organs
- rapid respirations
- Large body surface
- Metabolic Rate
- *Unreliable thirst mechanism
- Decreased organ function
- ADH response less reliable
- Impact of chronic disease
Men & women contain what % of HCT?
Urine specific gravity
- HCT: men: 40-54%; women 35-47%
- Serum electrolytes:
- Urine specific gravity: 1.010-1.030
- (1.010: high solvent/low solute; 1.030 = high solute/low solvent)
- BUN: 10-20 mg/dL
- Creatinine: 0.7-1.4 mg/dL
Serum osmolality is indicated by which electrolyte (solute)?
Indicates Na+ concentration.
BUN and Creatinine.
What are they byproducts of and what do they determine regarding organs?
BUN is a Blood Urea Nitrogen in which urea is a byproduct of protein metabolism.
Creatinine is a byproduct of muscle contractions.
Both are excreted in the urine.
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