• NURS 8022 Fluids - Exam 3 Study Guide, University of Cincinnati, Main Campus

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NURS 8022 Fluids - Exam 3 Study Guide, University
of Cincinnati, Main Campus

Water Movement
 Osmosis
o Movement of water down concentration gradient
 Osmolality
o Concentration of molecules per weight of water
o Controls osmosis
 Osmotic Forces
o Amount of hydrostatic pressure (pushing) required to oppose the
osmotic movement of water
o Determined by thickness of plasma membrane, size of molecules,
concentration molecule gradient, solubility of molecules to membrane
 Sodium is most abundant in ECF
o Responsible for osmotic balance of ECF
 Potassium responsible for osmotic balance of ICF
 Proteins in ICF cannot diffuse out of cell so osmotic equilibrium is maintained by active
transport
 Changes in osmolality transfers water from one compartment to the other
until equilibrium is reached
 Filtration
o Movement of fluid from capillary into interstitial space
 Reabsorption
o Movement of fluid from interstitial space into capillary
 Forces that determine filtration or reabsorption
o Capillary hydrostatic pressure (blood pressure)
 Facilitates outward movement of water from capillary to interstitial space
o Capillary oncotic pressure (plasma)
 Attracts water from interstitial space back to capillary
o Interstitial hydrostatic pressure
 Facilitates inward movement of water from interstitial space into the
capillary
o Interstitial oncotic pressure
 Attracts water from the capillary into the interstitial space
 Starling hypothesis
o Net filtration is equal to forces favoring filtration minus the forces opposing
filtration
 Forces favoring filtration/opposing reabsorption
o Capillary hydrostatic pressure (blood pressure)
o Interstitial oncotic pressure (water pulling)
 Forces opposing filtration/forces favoring reabsorption
o Capillary oncotic pressure (water pulling)
o Interstitial hydrostatic pressure

,  Major forces for filtration and reabsorption are those within the capillary
o Capillary hydrostatic pressure (filtration)
o Capillary oncotic pressure (reabsorption)
 Arterial end of capillary
o Hydrostatic pressure > interstitial oncotic pressure = water filters into interstitial
space FILTRATION
 Venous end of capillary
o Capillary oncotic pressure > interstitial hydrostatic pressure = fluids move into
circulation REABSORPTION
 Integrity of capillary membrane is essential in capillary filtration of fluid

Fluids and patho of edema
 Accumulation of fluids in interstitial spaces
 Causes
o  capillary hydrostatic pressure (venous obstruction)
o  plasma oncotic pressure (diminished production of albumin)
o  capillary permeability (inflammation and immune response)
o Lymph obstruction (lymphedema)
o Sodium retention
 Pathophysiology
o  forces favoring fluid filtration from the capillaries or lymphatic channels into
tissues
 Manifestations
o Localized
 Limited to site of trauma or specific organ system
o Generalized
 Dependent edema
o Weight gain, swelling, puffiness, limited movement of affected area
 Third spacing
o Fluid moves to interstitial space, pleural space, pericardial space
o Not available for metabolic processes or perfusion