Body Fluids Flashcards
How much of total body weight is water?
~ 60%
Best way to track fluid status?
body weight
-over days to weeks
Other important factors in monitoring fluid status
- careful hx
- physical exam
- serum and urine electrolytes
How do you assess fluid status?
- systolic BP
- orthostatic hypotension
- urine output
- 24 hr urine sodium
- skin turgor
- cap refill
- breath sounds
- mucus membranes
- serum sodium
What is normal systolic bp?
70 + 2 x age
Wha is normal urine output?
1-2 L
Conditions related to abnormal urine sodium levels
- diabetes insipidus (low ADH; oliguria)
- SIADH (syndrome of inappropriate antidiuretic hormone) (high ADH; fluid overload)
What causes crackling breath sounds?
fluid overload; i.e pulmonary effusion/edema
How do body fluids affect serum sodium levels?
- increased volume = hyponatremia
- decreased volume = hypernatremia
Tx of dehydration in hospitalized patients
- 20cc/kg in bolus
- check for euvolemia, bp, breath sounds before giving more
starling forces (4)
- capillary hydrostatic force
- capillary osmotic force
- tissue hydrostatic force
- tissue osmotic force
capillary hydrostatic force
- systolic bp
- drives fluid out of vasculature
capillary osmotic/oncotic pressure
- derived from dissolved substances in blood (albumin)
- keeps fluid inside vasculature
osmolality
- solute concentration in the serum derived from dissolved particles
- measured in osmoles/kg of water
What is normal osmolality?
285-295 mosm/kg
How do you calculate osmolality?
2(Na mEq/L) + (glucose/18) + (BUN/2.8)
Major ion that influences osmolality
Na+
hypovolemia
- decrease in total body water
- dehydration
- replace in all 3 spaces
hypervolemia
- increase in total body water
- intravascular: venous pooling
- over time, excess fluid goes to extracellular tissue causing edema
euvolemia
- appropriate total body water
- doesn’t mean there are no problems
causes of increased interstitial fluid (5)
- increased osmotic pressure of interstitial fluid
- decreased intravascular oncotic pressure
- increased venous hydrostatic pressure
- obstruction of lymph drainage (lymphadema)
- increased endothelial permeabilty
What can cause increased osmotic pressure of interstitial fluid?
increase in total body sodium:
- excessive salt intake
- increased retention of Na by kidneys
- decreased Na excretion
- reduced renal profusion
What is a sign of end stage renal failure?
Reduced renal profusion -> hyperkalemia -> generalized edema
Causes of decreased oncotic pressure of plasma proteins
- failure of albumin synthesis (like in liver disease, malnutrition, Crohn’s, bariatric surgery)
- excessive albumin loss (like in glomerulopathy and enteropathy)
Cause of generalized edema
- increased tissue osmotic pressure
- decreased intravascular oncotic pressure
Cause of localized edema
- increased venous hydrostatic pressure
- obstruction of lymph drainage (lymphadema)
- increased indothelial permeability
Cause of increased venous hydrostatic pressure
interference w/ or obstruction to venous blood flow
-ex: DVT
Symptoms associated w/ DVT
- swelling
- pain
- redness
What can cause obstruction of lymph drainage?
- lymphatic obstruction
- cancer
- scarring (radiation)
- parasitic disease
- lymphadenectomy
Causes of increased endothelial permeability
- inflammation (wheel and flare)
- immunologic reactions
- tissue injury
What determines the clinical significance of edema?
- severity
- location
- rapidity of development
- underlying cause
Edema is also called what?
third spacing (not in blood vessels or cells)
transudate
- edema that develops from imbalances in normal hemodynamic forces
- low protein
- low specific gravity
example causes of transudate
- CHF: increased intravascular hydrostatic pressure
- liver disease: decreased albumin synthesis, obstruction of portal veins
- renal disease: excessive albumin loss or Na intake
- GI disorders: protein malabsorption or protein losing enteropathies
exudate
edema caused by endothelial damage or alteration of vascular permeability
- high protein
- high specific gravity
example causes of exudate
- inflammatory/immunologic disorders
- infections (cellulitis)
- ALWAYS have inflammatory component
pitting edema
- edema w/ no blockage to lymph channels
- excess fluid readily leaves area w/ light pressure (back into lymph channels)
Characteristics of pitting edema
- inflammatory mediators
- excess Na+
- decreased plasma albumin
lymphedema
- does not pit (nowhere to go)
- blockage to lymph channels
example causes of lymphedema
- infection w/ parasite
- neoplasm
- mechanical obstruction of lymph channel
common disorders associated w/ edema
- heart failure
- liver disease
- renal disease
- GI disease
- inflammation/immunologic
What is congestive heart failure?
- decreased cardiac output (systolic bp)
- causes hypoxia and congestive effects on organs and tissues other than heart
- accumulation of fluid in venous system
Clinical manifestations of left-sided heart failure
- easy fatiguability
- SOB or DOE (dyspnea on exertion)
- PND (paroxysmal nocturnal dyspnea)
- orthopnea
- cough
What is left sided heart failure?
- left ventricle is unable to maintain adequate cardiac output
- causes backup in lungs leading to pulmonary edema
- kidneys stimulate retention of Na and water
What is right sided heart failure?
- right side of heart is unable to maintain adequate ventricular output to lungs
- causes venous backup
- increased pulmonary arterial pressure (pulmonary htn)
cor pulmonale
right-sided heart failure that is the result of pre-existing left heart failure
What is the most common cause of right heart failure?
cor pulmonale
example causes of right heart failure
- scarring of right heart
- damages lungs unable to pump blood (interstitial lung disease)
- cor pulmonale
consequences of right heart failure
- engorgement and distention of neck veins leading to cerebral congestion and hypoxia, irritability, restlessness, stupor
- passive congestion of liver
- portal HTN leading to ascites and congestive splenomegaly
- dependent pitting edema
- increased body weight
causes of liver disease
- cirrhosis
- hepatocellular damage
complications of liver disease
- decreased synthesis of plasma protein
- decrease ease of blood flowing through liver
- portal vein has increased in hydrostatic pressure
- pooling of blood in portal venous circulation
examples of renal disease that cause edema
- glomerulopathy
- tubular dysfunction
- SLE attacking kidneys
nephrotic syndrome
- holes in filtration membrane allows protein loss through excretion
- causes anasarca (widespread swelling of skin caused by edema into extracellular space)
complications of renal disease
- loss of plasma protein
- increased Na retention
- anasarca
examples of GI diseases that can cause edema
- starvation
- malabsorption
- enteropathy
complications of GI disease
- plasma protein deficiency
- decreased intravascular osmotic pressure
- increased interstitial fluid (edema)
inflammatory/allergic cause of edema
- inflammatory cells leave vascular space
- release mediators of inflammation
- capillaries become leaky
- fluid accumulates where there is loss of connective tissue (exudate)
*review steps of how kidney’s compensate for heart failure
- decreased CO
- decreased renal blood flow
- kidneys perceive hypovolemia
- kidney produce renin
- activation of ACE
- conversion of angiotensin I to II
- release of aldosterone
- increased retention of Na and K
- increased water retention
- increased BP
- decreased renin production
