Body Fluid Compartments Flashcards
Renal function
Excretion (urea, blood, nitrogen, creatininate)
Regulation of H2O and electrolyte balance
Regulation of body fluid pH
Regulation of arterial BP (regulation of Na balance…change is change in ECF volume)
Renin-angiotensin-aldosterone system…increase in angiotensin 2…increase i nvasoconstriction.
Increase in aldosterone—-decreased urinary Na excretion
Erythrocyte production
Decreased O2 delivery to kidneys…increase EPO…increase erythrocytes
Sites - peritubular fibroblasts and endothelial cells
Regulation - transcription factor - hypoxia inducible factor-1 (HIF-1)
Normal O2 - HIFalpha degraded
Low O2 - HIFa and B dimerize…means increase in EPO trancription and translation
Regulation of vitamin D activity
Vitamin D—-25-OH vitamin D (liver)—-1,25(OH)2vitamin D (kidney)
Site - proximal tubule cells via 1 alpha-hydroxylase
Enzyme is very heavily regulated
Gluconeogenic capcity
decreased plama glucose…increased renal proximal tubule glucose biosynthesis
Metabolic acidosis HYperkalemia Uremic toxicity Sodium/H2O imbalance Ca/PO4 imbalance PLasma protein imbalance Anemia Immune system
pH<7.4
Plasma K>4
Azotemia - increased plasam creatinine and BUN
Change in fluid volume leads to change in BP
Decreased vitamin D…decreased calcium…increase bone fracterues
Edema - excess fluid deposition in interstitial spsce
Decreased EPO synthesis
Immune - needs to be swimming in ECF environment in order to work properkly
Renal functinal reserve capacity
Body homeostasis can be maintained until renal function decreases to 20% of normal
Pre-renal failure
Intra-renal failure
Post-renal failure
ARF - reversible
Pre - decreased renal blood flow leads to decreased GFR
Intra- acute tubular necrosis - ischemia./toxin induced
Post - urinary tract obstruction
Chronic reanl failure and ESRD
CHronic - irreversible, usually progressive renal injury…most common diabetes
ESRD - GFR<10% of normal
Permenanet renal replacement therapy needed for ESRD but supply
Dialysis principle
Across articifical membrane (hemo) or capillaries (peritoneal)
Blood flow through upper compartment…dialysis fluid flows in the counter direction through the lower compartment (renewed)
Renal failure dialysis (think K+ and creatinine)
Will have increase plasam creatinine and K+ in renal failure
With lower creatinine/K+ concentrations in the dialysis fluid, both diffuse from plasma to the dialysate
Over the course of the tx period, plasam creatinine, and K+ restored to normal
Renail failure dialysis (HCo3-)
Decreased in renal failure (met acid)
With higher concentration in dialysis fluid…will diffuse from dialysate to plasma
Over course of tx, HCO3 returned to normal
Renal failure dialysis - fluid accumulation
WIth lower HS pressure and high osmotic pressure in dialysate
Water moves from plasma to dialysate
Over course, EC fluid volume resotred toward normal
Hemodialysis
Blood pumped through external artificial dialyzer
3X week for 3-4 hours a piece
Peritoneal dialysis
FLuid in peritoneal cavity…peritoneum acts as dialysis memmbranes
Chrnic ambulatory peritoneal dialysis - fluid exchanged 4-6X per day
Higher risk of infection
You can keep doing this yourself
Limitation of intermittent hemodialysis
Between sessions - body weight increases due to rentention of water
Plasma creatinine increases
Kidneys “rpcoess” plasam continuously to try to minimize compostion changes
Total body water depends on
Gender dependence…higher percentage iin males because of more muslce and less fat
Age - water content decrease with age as muscle decreases and adipose increases
Water distribution
2/3 IC and 1/3 EC
ECF - 75% interstitial fluid, 25% plasma, transcelular - 5% of BW
Solute content of ECF and ICF
Cations - ECF = Na
ICF = K (due to membrane Na-K-ATPase)
Anions - ECF - Cl-/HCO3-
ICF- organic phaophates and proteins
PLasma and interstitual fluid compositions
ECF/ICF osmolarities
Similar except plasma has more protein and therefore more Ca/Mg
ECF and ICF osmolarities are identical
How to measure osmolarity
Posm = 2*Na+(glucose/18)+(BUN/2.8)
Dilution principle
Add known amount of measurable substance X to unknown volume
Mix until substance distriutes through the fluid
Fluid volume = amount of X added/concentration at equilibrium
Application of dilution principle to body fluid volumes
Marker substances distributed in compartments to be measured
Volume should include plasma volume
Any losses quantifiable
SAME marker must be used pre and post tx
Sodiium space/iulin space defines the marker used to measure
Compartment volume = (amount of X given)-amount of X lost divided by conentrationf X at equibilirum
ECV
Plasma volume
Total body water
ECV - radiolableed sodium, sucrose, mannitol, inulin
PV - iodinated albumin, T-1824 (evans blue)
Total body water - tritiated water, heavy water, antipyrine
Indirect volume measurements (Interstitial volume and intracellular volume)
Cannot take a sample of fluid from volume of interest
Interstitial volume = ECV-PV
ICV = Total body water-ECF
Fluid exhcnage between interstitium and intracellular space
Role of osmotic pressure
Disrupted by ingesiton of water, dehydration, IV infusions, fluid losses
To asses impact of an insult…at equilibirium osmolaritires of extra and intra fluid must be equal…shifts result from H2O movememnt ONLY
Addition of water
ECF volume increases and as a consequence the ECF osmolarity decreases…H2O flows from ECF to ICF…ECF volume decreases and ICF volume increases and as a consequence the ECF osmolarity increases and ICF osmolarity decreases
Once ECF/ICF osmolarities equalize, there is NO NET flux of H2O
Addition of hypertonic NaCl
Hypotonic NaCl
Loss of water
ICV decrease and ECV increase…both osmolarities increase
Both osmolarities decrease and both volumes increase
Both volumes decrease and both osmolarities increase
