Renal 1 Flashcards
Constant (2)
of body fluid compartments are essential
for homeostasis:
volume and stable composition
Constant volume and stable composition
of body fluid compartments are essential
for homeostasis:
“A frequent problem in treating seriously
ill patients is…
maintaining adequate fluids
in one or both of the intracellular and
extracellular compartments.”
Water in =
Water out
Electrolytes in =
Electrolytes out
pH =
7.4
Fluid distribution in the body influences — concentrations
electrolyte
Electrolyte concentrations influence
fluid distribution in the body.
Na+
–Imbalance changes
vascular and total body
volumes
K+
–Imbalance alters
cardiac and neural functions
Ca++
–Imbalance alters (3)
skeletal muscle, cardiac, neural function and bone structure
H+ (mainly from metabolism)
–Imbalance alters
multiple systems
Total body water
volume is
42L,
~60% body
weight (kg)
Plasma & Interstitial fluid mix rapidly (except proteins): (2)
- Hydrostatic and colloid osmotic pressure via capillary pores is
main force. - Bulk flow
Fluid distribution between ICF & ECF determined by osmotic effect
of small solutes acting across cell membrane: (2)
- Na+ and Cl- (other anions) ≈ 90% of total ECF osmolarity
- K+ and other ions ≈ 90% of total ICF osmolarity.
Cell membrane: (2)
- high permeability to H2O;
- relative impermeability to small solutes (Na+, Cl- & other
electrolytes) .
Cell volume is at the
mercy of
ECF tonicity
ECF (2) Constantly
Challenged
Osmolarity and
Volume
Daily life (2)
Eat and drink
Do not eat and drink
skipped
Conditions/Illnesses (4)
Vomiting, diarrhea Burns and other causes of skin loss Heat-induced sweating Renal disease
Composition and volume of ECF change determines
composition and volume of fluid replacement
The kidneys regulate body
fluid volume and composition
by controlling (2)
ECF volume and
composition.
Edema
• Too much water in
tissues.
— edema
much more common
than —.
Extracellular
intracellular
Intracellular Edema
Causes: (3)
- Hyponatremia.
- Decreased metabolism (blood flow): Na+/K+
pump failure. - Inflammation (infection, burns) – increased
membrane permeability and leakage.
— is the most important cation in the body
Na
Na salts make ip >—% of osmotically active solute in the ECF
90
Na (and hence ECF volume) is highly
regulated
too little ECF leads to (3)
volume contraction, hypotension and organ hypoperfusion
too much ECF leads to (4)
edema, ascites, pleural effusions, hypertension
Hyponatremia (3)
[Na+]ECF is below normal (<142 mOsm/L)
Na+ input < Na+ output
H2O input > H2O output
Hyponatremia types (3)
- Hyponatremia-dehydration
- Hyponatremia-overhydration
- Hyponatremia–low solute intake
Most common electrolyte
disorder in clinical practice
May account for —% of
hospitalized patients.
Hyponatremia
20-25
- Hyponatremia-dehydration (2)
- Increased NaCl loss
- Vomiting, diarrhea; renal disease, diuretics; Addison’s disease
(aldosterone deficiency).
- Hyponatremia-overhydration (2)
- Excess H2O retention
- Inappropriate ADH secretion, H2O Toxicity
- Hyponatremia–low solute intake (2)
- Decreased NaCl intake
- Extreme diets
Chronic Hyponatremia (5)
Gradual decrease in [Na+]ECF This stimulates transport of Na+, K+, and organic solutes out of the cells This causes water diffusion out of the cells With chronic hyponatremia, the brain swelling is attenuated by the transport of solutes from the cells. Must correct [Na+]ECF slowly to avoid osmotic demyelination
Acute hyponatremia (4)
Rapid decrease in [Na+]ECF
Caused by loss of Na+ or excess H2O
H2O into the cells
Swelling of the brain tissue.
Increased interstitial fluid volume (swelling) caused
by: (2)
Increased capillary filtration (most common;
congestive heart failure)
Failure of lymphatics to return interstitial fluid to
circulation (lymphedema)
Kf α
(SA)(Membrane Permeability)
Filtration Rate =
Kf ((Pc + Piif) – (Pif + Pic ))
Common Causes of Extracellular Edema (3)
Capillary permeability
Increased capillary hydrostatic pressure
Decreased capillary colloid osmotic pressure
Capillary permeability (3)
–Inflammation (infection, immune reactions)
–Burns
–Ischemia
Increased capillary hydrostatic pressure (2)
–Heart failure (generalized vs left heart failure)
–Renal disease
Decreased capillary colloid osmotic pressure (2)
–Renal loss (nephrotic syndrome)
–Liver disease
“Potential spaces” – (4)
pleural, pericardial,
peritoneal, synovial cavities.
Lining membranes are highly —.
permeable
Lymphatic drainage important for
clearing fluid
and proteins.
Ascites is an example of “—.”
effusion