4.1 - Fluid Imbalances Flashcards
What are the Fluid Compartments in the Body
- total body fluid is distributed through 2 compartments
- water is primary component - 60%
1) Intracellular
- fluid inside cells
- 40% of body weight
- high in potassium
Functions: maintains cell structure, allows for metabolic processes, and provides medium for cell rxns
2) Extracellular
- fluid outside of cells
- 20% of body weight
- high in sodium
- divided into 3 compartments:
1. Intra-vascular - fluid inside blood vessels
2. Interstitial - fluid surrounding cells
3. Transcellular - fluid in cavities (CSF fluid)
What is the Role of Fluid
1) temp regulation (sweating, respiration)
2) lubrication - for joints
3) shock-absorption: protects organs/tissues
4) transportation - brings nutrients to cells
5) chemical rxns: solvent for rxns to occcur
How does Fluid Move?
- cell membranes are selectively permeable: allow water and small solutes, not plasma proteins
Aquaporins: specialized channel that allows passage of water
- prevents passage of ions/solutes
What are the forces moving fluid?
1) Osmolality
- influences water movement between compartments
2) Osmotic Forces
- pressure exerted by solutes that drive water across semi-permeable membrane
3) Starling Forces
a. Hydrostatic pressure (PUSHES)
- pushes fluid from blood vessels into interstitial fluid
b. Oncotic pressure (PULLS)
- pulls fluid from interstitial space into blood vessels
4) Capillary Exchange
- fluid moves between blood and tissues
- influenced by hydrostatic and oncotic pressure, and cap permeability
What is Net Filtration
- balance of forces that determine movement of fluid
Forces Favouring Filtration
1) Capillary Hydrostatic Pressure:
- pushes fluid out of capillaries and into tissue
2) Interstitial Oncotic Pressure
- pulls fluid out of capillaries into interstitial space
Forces Favouring Reabsorption
1) Capillary Oncotic Pressure
- pulls water from tissues into capillaries
2) Interstitial Hydrostatic Pressure
- pushing fluid from interstitial space into capillaries
4 Imbalances of Fluid Compartments
1) Edema
- too much fluid in interstitial space
2) Third Spacing
- too much fluid in transcellular spece
3) Hypovolemia
- too little fluid in intravascular space
4) Hypervolemia
- too much fluid in intravascular space
Causes of Edema
1) Increased Cap hydrostatic pressure
- more fluid pushed out of capillaries into tissue
2) Increased cap permeability
- more fluid leaks into tissues
3) Lymphatic obstructions
- blocks drainage of fluid from blood into tissues
4) Decreased plasma oncotic pressure
- reduced amount of fluid being pulled unto the blood
Structural Alterations
1) Localized Edema
2) Generalized edema - whole body swelling
3) Non-pitting
- interstitial fibrosis
- protein-rich fluid
4) Pitting Edema
- indentation with pressure
5) Circulatory Effects
- increased fluid in tissues mens less blood volume
- decreased blood volume triggers RAAS to conserve more water
- aldosterone increases reabsorption of water and sodium which worsens fluid retention
- angiotensin II causes vasoconstriction to increase BP and promotes fluid leaking out of blood
Clinical Significance
- impaired mobility
- skin breakdown
- pressure ulcers
- decreased fluid function: bc of fluid accumulating around organs
Cause of Third Spacing
1) infection and sepsis
2) trauma burns
3) surgery
- cause inflammation and increase cap permeability
4) Kidney disease
5) Heart failure
6) Pancreatitis
7) Malnutrition
- influence hydrostatic and oncotic pressure
Pathogenesis of Third Spacing
1) Increased cap hydrostatic pressure
- pushed out of capillaries into 3rd space
2) Decreased plasma oncotic pressure
- less fluid is being pulled in to bluid; accumulates in third space
3) Increased cap permeability
- more leaks out of caps into space
Structural Changes of Third Spacing
Ascites
- fluid accumulation in the peritoneal cavity
Pleural Effusion
- fluid accumulation in pleural cavity
Pericardial Effusion
- fluid accumulation in pericardial cavity
Clinical Significance of Third Spacing
1) decreased blood volume -
- fluid in 3rd space is not available for circulation
2) organ dysfunction - excessive fluid can impair organs
3) infection - ascites, peritonitis
Types of Solutions
1) Isotonic
- contents of solutes in extracellular and intracellular fluid is equal
2) Hypotonic
- extracellular fluid < intracellular fluid
3) Hypertonic
- extracellular fluid > intracellular fluid
Fluid Volume Deficits
Isotonic
- water and sodium are lost in = portions
Hypotonic
- more WATER LOST (in extracellular fluid)
-more sodium
- water moves from intracellular to intravascular compartment
- causes cell dehydration
Hypertonic
- more SODIUM LOST (less sodium)
- water moves from intravascular space into interstitial space
- cell swelling
