NR283 Pathophysiology Exam 2
Comprehensive Study Guide
1. Fluid, Electrolyte, and Acid-Base Homeostasis
Fluid Compartments and Distribution
The human body is approximately 60% water, divided into two primary compartments:
• Intracellular Fluid (ICF): Fluid located inside the cells; stores the majority of the body's
fluid.
• Extracellular Fluid (ECF): Includes intravascular fluid (plasma in capillaries),
interstitial fluid (between cells), and transcellular fluids (e.g., cerebrospinal fluid).
Mechanisms of Fluid Balance
• Thirst Mechanism: Located in the hypothalamus; osmoreceptors detect changes in fluid
volume and concentration to promote intake.
• Antidiuretic Hormone (ADH): Controls fluid exit via urine by promoting water
reabsorption in the kidney tubules.
• Aldosterone: Increases blood volume by promoting the reabsorption of sodium and
water in the kidneys while excreting potassium.
• Atrial/B-type Natriuretic Peptide (ANP/BNP): Released by cardiac muscle in response
to increased pressure; promotes the excretion of water and sodium while retaining
potassium.
Movement of Fluids and Pressure
• Hydrostatic Pressure: A "pushing" pressure that moves fluid out of the vessels and into
the interstitial space.
• Osmotic (Oncotic) Pressure: A "pulling" pressure, largely regulated by plasma proteins
like albumin, that draws fluid into the vessels from the interstitial space.
, Fluid Volume Imbalances
Compensation
Condition Causes Clinical Manifestations
Mechanisms
Increased ADH
Blood loss, severe Low blood pressure, tachycardia secretion,
diarrhea, inadequate (fast/weak pulse), decreased increased
Hypovolemia
intake, diuretic use, skin turgor, dry mucous aldosterone, thirst
(Dehydration)
excessive sweating, membranes, confusion, lethargy, activation,
vomiting. decreased urine output. increased heart
rate.
Kidney failure, heart
High blood pressure, bounding
failure, liver failure,
pulse, edema (pitting/anasarca), Increased urine
Hypervolemia increased sodium
Jugular Vein Distention (JVD), output (if kidneys
(Fluid Excess) intake, excessive IV
weight gain, pulmonary are functional).
fluids, blood
congestion (shortness of breath).
transfusions.
Special Populations at Risk for Dehydration:
• Infants: High surface area to volume ratio, inability to communicate needs, and
dependence on others for fluid.
• Older Adults: Forgetting to drink enough fluid and loss of the thirst mechanism.
Edema Pathophysiology
Edema is the accumulation of fluid in the interstitial space caused by:
1. Increased Capillary Hydrostatic Pressure: Prevents fluid return; pushes fluid out (e.g.,
heart failure).
2. Decreased Capillary Osmotic Pressure: Low plasma proteins (albumin) due to liver
failure or malnutrition prevent fluid from being pulled back into the vessel.
3. Increased Capillary Permeability: Occurs during inflammation or anaphylactic
reactions (histamine release), allowing proteins and fluid to leak into the interstitial space.
4. Lymphatic Obstruction: Tumors or lymph node removal prevent fluid return to
circulation.
Comprehensive Study Guide
1. Fluid, Electrolyte, and Acid-Base Homeostasis
Fluid Compartments and Distribution
The human body is approximately 60% water, divided into two primary compartments:
• Intracellular Fluid (ICF): Fluid located inside the cells; stores the majority of the body's
fluid.
• Extracellular Fluid (ECF): Includes intravascular fluid (plasma in capillaries),
interstitial fluid (between cells), and transcellular fluids (e.g., cerebrospinal fluid).
Mechanisms of Fluid Balance
• Thirst Mechanism: Located in the hypothalamus; osmoreceptors detect changes in fluid
volume and concentration to promote intake.
• Antidiuretic Hormone (ADH): Controls fluid exit via urine by promoting water
reabsorption in the kidney tubules.
• Aldosterone: Increases blood volume by promoting the reabsorption of sodium and
water in the kidneys while excreting potassium.
• Atrial/B-type Natriuretic Peptide (ANP/BNP): Released by cardiac muscle in response
to increased pressure; promotes the excretion of water and sodium while retaining
potassium.
Movement of Fluids and Pressure
• Hydrostatic Pressure: A "pushing" pressure that moves fluid out of the vessels and into
the interstitial space.
• Osmotic (Oncotic) Pressure: A "pulling" pressure, largely regulated by plasma proteins
like albumin, that draws fluid into the vessels from the interstitial space.
, Fluid Volume Imbalances
Compensation
Condition Causes Clinical Manifestations
Mechanisms
Increased ADH
Blood loss, severe Low blood pressure, tachycardia secretion,
diarrhea, inadequate (fast/weak pulse), decreased increased
Hypovolemia
intake, diuretic use, skin turgor, dry mucous aldosterone, thirst
(Dehydration)
excessive sweating, membranes, confusion, lethargy, activation,
vomiting. decreased urine output. increased heart
rate.
Kidney failure, heart
High blood pressure, bounding
failure, liver failure,
pulse, edema (pitting/anasarca), Increased urine
Hypervolemia increased sodium
Jugular Vein Distention (JVD), output (if kidneys
(Fluid Excess) intake, excessive IV
weight gain, pulmonary are functional).
fluids, blood
congestion (shortness of breath).
transfusions.
Special Populations at Risk for Dehydration:
• Infants: High surface area to volume ratio, inability to communicate needs, and
dependence on others for fluid.
• Older Adults: Forgetting to drink enough fluid and loss of the thirst mechanism.
Edema Pathophysiology
Edema is the accumulation of fluid in the interstitial space caused by:
1. Increased Capillary Hydrostatic Pressure: Prevents fluid return; pushes fluid out (e.g.,
heart failure).
2. Decreased Capillary Osmotic Pressure: Low plasma proteins (albumin) due to liver
failure or malnutrition prevent fluid from being pulled back into the vessel.
3. Increased Capillary Permeability: Occurs during inflammation or anaphylactic
reactions (histamine release), allowing proteins and fluid to leak into the interstitial space.
4. Lymphatic Obstruction: Tumors or lymph node removal prevent fluid return to
circulation.
