Fluid and Electrolyte BalanceFluid and Electrolyte Balance balance.pdf · · 2011-10-31Fluid and...
Transcript of Fluid and Electrolyte BalanceFluid and Electrolyte Balance balance.pdf · · 2011-10-31Fluid and...
Ch 34: Control of Body Fluid Osmolality and VolumeCh 2 : Homeostasis of Body Fluids
Fluid and Electrolyte BalanceFluid and Electrolyte BalanceFluid and Electrolyte BalanceFluid and Electrolyte Balance
Myoung Kyu Park MD. PhD.Department of PhysiologySungkyunkwan University School of Medicine
Fluid and Electrolyte BalanceFluid and Electrolyte Balanceu d a d ect o yte a a ceu d a d ect o yte a a ce1. Distribution and measurement of body fluid compartmentsy p2. Compartmental fluid balance and compositions3. Systemic fluid balance : water intake & output4 Regulation mechanism of extracellular fluid volume4. Regulation mechanism of extracellular fluid volume5. Electrolytes balance
Body FluidBody FluidBody FluidBody FluidYoung men Young WomenYoung men Young Women
60% of body weight60% of body weight
50% of body weight50% of body weight
cf. water content ; fat tissue (10%), other tissues (70-75%)
Body Fluid CompartmentsBody Fluid Compartments70 kg man
Intracellular fluid (ICF) Extracellular Fluid (ECF)
40% 28L 15% 5%340%, 28L 10.5L 3.5L
interstitial Fluid Plasma 1-3%(ISF) Plasma
1/32/3 transcellularfluid
(ECF, 14L)
Total Body Water (42L)
60%
(ECF, 14L)CSFAquaous humorSynobial fluid
60%
Measurement of body fluid compartmentsMeasurement of body fluid compartments
Camount Substance Methods
TBW Tritiated water and D2O
V =amount
ECF sulfate, inulin, manitol
Plasma radioiodinated serum albumin, Evans blue
I t titi l ECF l l lV = concentration
Interstitial ECF vol – plasma vol
ICF TBW – ECF vol
Electrolyte Composition of the Body FluidsElectrolyte Composition of the Body FluidsElectrolyte Composition of the Body FluidsElectrolyte Composition of the Body Fluids
2 Osmolarity determines fluid volumes1. Key ions determine fluid volumes2.Osmolarity determines fluid volumes
Electrolyte composition between ICF and ECF is different but the osmolarity is the same
OsmECF = OsmICF
Electrolyte composition between ICF and ECF is different, but the osmolarity is the same
Osmotic Pressure determines Cell Volumes (ICF)( )
Hypertonic solution Isotonic solution Hypotonic solution
Solution glucose(g/dL) Na+ K+ Ca2+(mEq/L) Cl- lactate osmolarity(mOsm/L)
5% dextrose 5.0 Isotonic (278)10% dextrose 10.0 hypertonic (556)5% dextrose 5.0 154 hypertonic (586)in 0.9% saline
half strength 77 77 hypotonic (154)half strength 77 77 hypotonic (154)saline(0.45%)
normal saline 154 154 isotonic (308)(0.9%)
Lactated Ringer's 130 4 3 109 28 isotonic (274)solution
Importance ofImportance of ECFECF volumevolumeImportance of Importance of ECFECF volumevolume
ICF ISF Plasma
ISF is a diffusion medium between plasma and ICF.
Maintenance of ECF volumeis essential for the adequacy of the circulation.
[N +] ECF l
ECF volume is determined by mainly Na+ concentration
[Na+] ECF vol.
cf. cell memb. permeability
Evolutionary changes
j ll fi hsponges jellyfish
earthworm
Cariovascular system
separated from ECF
T bP
separated from ECF
TubesPump
HemoglobinRBC
concentratedand packed
Systemic circulation - High Pr, High Resis
RBCand packed
Pulmonary circulation - Low Pr, Low Resis
Two Important FactorsTwo Important FactorsTwo Important FactorsTwo Important Factors70 Kg man
Fl id V lFluid Volume Osmolarity
hyper-volemia hyper-osmolaritydemyelination
hypertensionedema
290 mOsm42 L
hypo-volemia hypo-osmolarity
swelling of brain cellsnausea, malaise, headache, confusion, lethargy, seizures, and coma
swelling of brain cellshypotensionshock
Shifts of water between compartmentsShifts of water between compartments
Add pure waterNormal300 mOsm
ysm
olal
ity
ECFICF
os
2/3 (28L) 1/3 (14L)
volume
2/3 (28L) 1/3 (14L)
Darrow-Yannet Diagram
Addition of Pure Water SIADH (ADH)Addition of Pure Water hyposmotic vol expansionProt conc.
HCt
300 mOsm
HCt
tysm
olal
it
ECFICF
os
volume0 28 42 L
Shifts of water between compartments(b) Add pure water(a) Normal hyposmotic vol expansion
Prot conc.
HCt
SIADH (ADH)
ECFICF ICF ECFos
mol
arity
HCt
(c) Add isotonic saline (0 9%NaCl) (d) Add pure NaClvolume
o
hyperosmotic vol expansion(c) Add isotonic saline (0.9%NaCl) (d) Add pure NaCl
isosmotic vol expansionProt conc.
0.9% saline IV
hyperosmotic vol expansionProt conc. HCtBP
ICFICF ECF ECFHCtBP
isosmotic vol contraction isosmotic vol contractionDiarrhea Hemorrage
hyperosmotic vol contractionSweating (hypotonic)
Prot conc. HCtBP
Prot conc. HCtBP
Prot conc.
HCt
ICF ISF Plasma
Fluid balance between ISF and Plasma : Starling's law
illcapillary
hydrostatic pressure osmotic pressure hydrostatic pressurey32 mmHg
p22 mmHg
y p12 mmHg
arterialend
venousend
Net Flow
(+10 mmHg) (-10 mmHg)
Oncotic proteins – albumin, globulin, fibrinogen
Disorders of Fluid BalanceDisorders of Fluid BalanceDisorders of Fluid BalanceDisorders of Fluid BalanceEtiology : liver, cardiovascular or renal disease, hormonal imbalance, or accidents
plasma-to-interstitial shift / plasma-to-transcellular space shift
Accumulation of fluid in interstices or connective tissues or transcellular spacesdue to increased hydrostatic pressure or decreased osmotic pressure (third space)
Edema, hydrothorax (pleural effusion), hydropericardium (pericardial effusion), hydroperitoneum (ascites)hydroperitoneum (ascites)
Edema: Increased hydrostatic pressureIncreased hydrostatic pressure
CHF, liver cirrhosis, constrictive pericarditis, venous obstruction, heat Reduced plasm osmotic pressure
nephrotic syndrome, Liver cirrhosis Lymphatic obstruction
inflamatory, neoplasmic, postsurgical Sodium Retention – pitting edema
Excessive salt intake Increased RAA systemExcessive salt intake, Increased RAA system Inflammation
Fluid and Electrolyte Balance
Maximum 4L/h
W t B lW t B lWater BalanceWater Balance
(at rest)habit
Water intake Water outputconstant
OsmICF effective circ. bl vol.
Thirst (emergency) KidneyCell vol. change
in ant HT osomoreceptor
baroreceptors in CV sys.
renin
hypothalamus
cortex ADHp
yp
cf. CHF – thirst feelingCirrhosis
Thirst : control mechanism for fluid intakeThirst
2
emergency mechanism controlled by hypothalamus i ti
PeripheralVolume
receptorsHigh threshold
conscious sensation
Osmoreceptorcells
Hypothalamus1
supraoptic nucleus
High threshold
ADH
paraventricular nucleusLow threshold
ADH
Posteriorpituitary
Release of ADHintocapillaries
Regulation of ECF VolumeRegulation of ECF Volumegg
OsmICFeffective circ. bl vol.5-10 % change
High pressure baroreceptors•carotid sinus & body
i h & b d
g
•organum vasculosum of the lamina terminalis
Circumventricular organs
•aortic arch & body•justaglomerular apparatus
(afferent arteriole)
of the lamina terminalis•subfornical organ
Low pressure baroreceptors Hypothalamus•supraoptic nucleus•atrial receptors – ANP
•artium, ventricle, pulmonary vein
•supraoptic nucleus•paraventricular nucleus
ADH(AVP)
FourFour Regulatory Pathways controlling Regulatory Pathways controlling g y y gg y y gECFECF volumevolume
1. Renin-Angiotensin-Aldosterone Axis2 Renal Sympathetic activation2. Renal Sympathetic activation3. Arginine Vasopressin (ADH)4 Arterial Natriuretic Peptide (ANP)4. Arterial Natriuretic Peptide (ANP)
1. Renin-Angiotensin-Aldosterone Axis
effective arterial blood volume
(Lung)
1. Renin-Angiotensin-Aldosterone Axis
AldosteroneAldosterone
principal cell
2. Renal Sympathetic activation
1 increases renal vascular resistance
Enhanced activity of the renal sympathetic nerves
1. increases renal vascular resistance2. enhances renin release from granule cells3. increases tubule reabsorption of Na+
Granular cells
RenalnervesAfferent
arteriole
H2O and Na+ retension
P i l
Bowman’s capsule
Urinary space
Thickascendinglimb
Proximaltubule
Maculedensa
Glomerularcapillaries
Efferentarteriole
Extraglomerularmesangial cells
3. Arginine Vasopressin (ADH)
Antidiuretic Hormone (ADH)
hi h th h ld thirst Factors to release ADH1. stretch receptors in heart LA
and Pul Vein
2 Pr in carotid sinus and
low threshold
high thresholdOsmoreceptors
thirst 1
2. Pr. in carotid sinus and aortic arch
3. kidney-granular cells – renin- angiotensin II
2
Raise plasma
Vasopressin – high conc of ADH by more than 10% loss of blood volume
Raise plasma osmolality shrink hypothal. osmoreceptors ADH cells
ADH release
Control of Secretion of Antidiuretic Hormone (ADH)
Osmolality Volume
set pointset point
• Continuous control of ADH level over the set point (278mOsm) and under the 10%• Continuous control of ADH level over the set point (278mOsm) and under the -10% change in circulating blood volume
• Osmolarity and effective circulating blood volume work together and reinforce each other
Cellular mechanisms of ADH action
1. Insertion2. Expression
AQP2AQP2
Water AbsorptionWater AbsorptionADH
Diabetes insipidus – ADH deficiency (nephrogenic or neurogenic)20 L/day urine
Systemic responses to changes in blood osmolarity and volume
4. Atrial Natriuretic Peptide (ANP)
ANP t i•ANP - atrium•BNP - ventricle•Urodilantin - kidney
BNP / urodilantin
vasodilation
Feedback Control of Effective Circulating Volume
Na+ ion
• determines ECF volume
• generates electrical activities
• supplies energy for cellular transport
Na+
Na+ Transport GFR = 180 L/day, PNa+ = 142 mM Filtered Load = 25,500 mmole/day (1.5kg) Diet 120 mmole/day
ADH
Paracellular pathway
Transcellular pathway
Regulation of Na+ Transport
100
33
8
3
0.4
cortex
medulla
67%
25%
5 %
3 %
Na/K/2Cl transporter
Na cotransporter
Na/H exchanger
Solvent drag
Na channels
Na-Cl transporter
Na channels
1. Glomerulotubular balance
2. Aldosterone
3. Sympathetic nerves
1. Decrease RBF & GFR
2. Release renin
3. Stimulate tubular Na+ reabsorption (activates NHE3 & Na pump)
4. Arginine vasopression –ADH
5. Atrial Natriuertic Hormone
1. increase RBF & GFR
2. inhibit Na reabsorption in
the medulla
6. PG, bradykinin, & dopamine
inhibit Na+ reabsorption
1
2 3
4
5
5
4
inhibition
stimulation
H2O channels
Sodium Balancemajor factor determining ECF Vol.
Sodium in diet100 - 300 mEq/dayINPUT
Extracellular fluid
95%small
Gastrointestinallosses (diarrheavomiting)
Skin (sweat,burns,hemorrhage)
KidneysOUTPUT
vomiting)hemorrhage)
positive Na+ balance ECF vol. generalized edema
High intake hypertension
Renal Responses to Na+ intakewater intake ECF Wt gain
( 198 )
Higher Na+ intake pos. sodium balance increase excretion restore equal balance
(Walser, 1985, Kidney Int)
• hypernatremia > 148 mEq/Lhyperaldosteronism sweatinghyperaldosteronism, sweatingburns, diabetes indipidus, diarrhea
• hyponatremia < 135 mEq/Ldiuretics, hypoaldosteronismSIADH, CHF, RF
Kidney FailureUremia (urine in blood)
Lack of erythropoietin anemia
Plasma urea creatinine and uric acid azotemia
( )
Lack of vitamin D activation bone disease
Increased ECF hypertension yp
Decreased H+ secretion metabolic acidosis
decreased GFR hyperkalemia decreased GFR hyperkalemia
ERDS: End State Renal Disease, GFR <10% of Normal
From dialyzerT di l
Superficialvein Hemodialysis: pump y
To dialyzer blood through dialyzer; more efficient than peritoneal dialysis
ArteriovenousfistulaRadial
artery
p y
Bubble trap
F h di l i
Dialyzer membrane
Fresh dialyzingsolution
Used dialyzingsol tion
Constanttemperat re bath
(c) 2003 Brooks/Cole - Thomson Learningsolutiontemperature bath