1. Fluid & Electrolytes Flashcards
What is the total body water in an adult male
42L in 70kg
60% Total body weight
Body Compartments
Exist in collections as compartments
ICF / ECF
- membrane side ->
ECF divided into
ISF
Itranvascular
CT / bone
transcellular
Transceullar
what
whats included
Virtual compartment - diverse group small fluid clollection
Transport activity / epithelail spaces
2.5% TBW
CSF Joint fluid aqeous Bile Bowel Body cavity urine
What controls distrubiton water
- Water can cross most - ease - solutes cant
Water moves until osmolality equal
ECF - easier sample
ECF osmality - controlls distrub TBW ECF/ICF
Osmoal ECF increased - net water movement out
Continue until ICF equals
- Na is major cation in ECF
Must asoc anion opposite equal total charge
Na & oblig anion - 86% osmality & 92% tonicty
Innefctive osmoles not counted
Distib EC & ICF - determ by Na in ECF - indirectly by controls of ECF na
Additional mechanisms @ local level
Cells can regulate intracellular solute
- allows adjust volume against tonicity
Local control - esp important in brain
eg neurones can produces extra osomole when bol decrease d/t extra hypertonicty - draw water back in
Conrol of TBW
Miantained fairly constant from day to day
Thirst ADH mechaninsm
Thirst afffect input & adh regulates output
Sesnsor - intergrator & effector
Closed loop changes - have effects monitored by sesnosr
Sensors:
Osmoreceptors
Volume receptor
High pressure barorectoprs
Central Controller
Hypothalamus
Effectors
Thirst ADH
Osmoreceptors
Special cell in hypothalamus - repson tonicity chagne
exact detail - ?
Neurone firing response volume
‘osmo=sodium’ - change balance - change tonicity
Volume receptors
Low pressure barorecptor - stretch wall large veins & RA
Mon volume - easses CVP
High pressure barorectpor
Cartoid sinus & arch - abp - affect if IV change - large affect systemic bp
No single antamoically discrete water balance - hypothalamus
Overall coordinates water balance
SOsmorectpor
other receptor - input pathway
Effector - controlled parts hypotahlamus
Thirst
Physiological urge drink
Hypertonictiy
hypovolame
hypotension
ang II
THirst centre hypothal - baclup - stimulate water when inadeq
Non regulatory - habit beahicour social
regulatory - backup
ADH
What is
Where prod
secreted
Nonapetide -
Prod - hypotahlamus &
secreted - posterior pituitary
acts kidney - increase h2o reabsoprtion
Increase reabsoprtion = decr plasma Na
Increase IV volume
Compeltes loop in negative feedback - control
fall tonicty rise vol sense
ADH Approp reg renal exretion reponse ecf tonicty / IV volume
How does ADH Act kidney
Si[rptoc & pv nucelie hypothal
Secret granules adh axons - [ppsteroor pituitary
Stimuli: Increased tonicty hyypovol hypotension AGII Stress Drugs - chlorproamide, barbituate, nicotine, morphine
Short t/12 15min
inact liver & kidney
Acts cortical & medullary CD
Two major cell types
Princial cell - Na.K
Intercalated cells - h ion
ADH combinces w/ V2 receports on BL membrane of principal cells - CD
Act AC & cAMP
- second messnegre
Cytoplsms fuse w/ luincal membrane - h2o channel - incor - water reabs down osmotic drag
when no adh - luminal membrane imprerable
Nature of water channels in vesicles
Aquaporin 2 - water cannel -
Present in membrane of vesicles - chennls inserted apical membra ne camp - removed when camp falls
What cell memebrane in the body are not permeable to water
Water crosses most easily - some low - functional require
- BLadder epithelium
- AscLOH - Na & cl transport out can produce hypotoinic
- Cortical & medullary CD in absence ADH - hypotinic urine
Principle in measure of body fluid compartments
Volme of ditrubtion of tracer - distrub only compartment measure - dilution principle’
Vol = amt/conc
Tracer - non tox rapid distrib & confined comparment
How colume ecf mesure
Ionics - br so4
Crystalloids inulin mannitol
Ionic tracers small - distrubite throught ecf - tracers also enter
ECF over est using ionic
Crystalloids - larger - not diffused thru ecf
Do not enter cells - lack full equal distrib = higher plsama conc - ecf under estimated w/ tracer
How is blood volume measure
plasma
Probs using Venous blood - est HCT
Indirectly - separate measure of
Hct
+
Plasma vol
PLASMA VOL - calc VD thru intvasc -
- dye Evans blue
- RadioIodine
BLOOD VOLUME
= Plasma vol x 100 / (100 - Hct)
or
Radiochromium labelled red cell as tracer
Effect of pregnancy on blood volume RC mass & plasma volume
All increase - differ amohts Blood volume 40-45% by term Plasma 50% Result in haemodiln Hb falls - phys anaemia preg = increase in RCM 250mls - 18% without supplemts
intracellular volume what is
23L - 55% of 42l TBW
Outline factors controlled ICF
- Tonicity
Water free movement - ecf tonicity change - - Concentration of colloid - non diffusible
set up Gibbs-Donnan effect - - Na main extra-cell cation - excluded cell -
a low permeability
b active extrusion sodium pump
Non diffusible - set up Gibbs-Donnan equil - tend extra-cell excess anion v intracell - cause water out
Second gibbs donnan equil - oppose action of first - intracell colloid
= balance - double donnnan - stable volume
Pump blcok - cell swell and rutpure
How do cells repsond to change in extracell tonicty
If acute change - cell vol change padily - equil
hypetnonicty - dehydration
hypo - cell swell
Mannitol - infused - increase ec tonicty & decrease celrebral cell volume
Cells - mechanisms minimse disurtion
alter intracellular solute
gain/ lose solute - change vol minimised
hypetonictiy - gain solute ecf or increase intra cell solute
Brain – meatnbolic alter o intracell particles - idogenic osmoles increase tonicty - draw water
chronic hyuptonicty - tolerated betetr acute
General - cells posses capacity lose gain solute - vary tonicty olume min change
Source ex cell or intra`1
What are colliigative properties
Colligative properties of a solution
Depend only on particle concetration - osmalility
Number particle per unit volume - iompratant and not type
Colligative properties are
Vapour pressure depression
frezing point depression
BP elavation
Osmotic pressure
What is osmositc presure
Meausre osmotic tendency for water to cross membrane
Hydrosatitc pressure - measure of osmolality of solution - ‘osmotic pressure’
Depened partilce concentration
What is total osmotic pressure of plsams
For osmalitly of 287mosm/lf - plasma osmotic pressure 5545mmHg -7.3atm
How is it calculated - vant hoff eqn
Molality
Molaity - no moles of solute per kg solvent - mole si amt sub
Number particles of sub pressent - 1 mole 10x23 particles avaogradors no
osmolality
Number of osmoles of solute per kg of solvent - 1 osm cont avogadros no no distinct about particles - amny types
Normal osmalitly of ECF
285-290 mosm /kg
Is Osmolaity same in ICF
Weater cross easily - osmotic gradient no continue - water will move
Osmolarity
Number of osmoles per litre of of soltion - alter by temp cahnge - expansion
cause 1l water = 1kg - numerical value almost same -
Tonicity
effective osmolaity of solitoon
Importance -
Water crosses nearly all cell membranes easily
Most solutes do not cross cell membranes easily
some do - urea
if added - water leak back - - no change across membrane ultimately
Osmolality needs to be corrected for type of solute - most do not cross - and edffective at exerting osmotic force -
some do n ot cross and ineffective at exerting force
Tonicity
Measusre only particles exerting osmotic force - effective osmolatiy - part of total osmolaity due to effective osmoles
Improtant detgermin fluid distrb accross membrane - allow solute cross membrea
osmorec - hupoyahl - respon to tonicty not osmolaltiy - omsol easy ,easure
Glucose & osm oles
Glucose can cross easily -
fat/muslce - facil insulin
not effective osmole
tONICTY ESTIMATEDD - OSMO - CONC UREA +_ GLUC
daibetics - insulin absent - effective osmole - exert osmotic effect accross membrane
hyperglycameia - can cause hypetonictiy
5% dex isosm - first infused - glucsoe taken and metabolised - infusion 5% - pure water
If urea crosses why is it effect at cerebral dehydrating
Urea crosses BBB solwer than water - increase d/t hypetonic w/draw water brain - decrease icp
Oncotic pressure
What is it
What size are they
Why is it improtant
Colloid osmotic pressure = component total osmolality d/t colloids
L
Large MW >3000 daltons
plasma - protein major colloids
typiocal value for plasma oncotic 25-28mmHg
0.5% total plasma pressur osmotic pressure
Why is it improtant - role capillary fluid dynamics - starlings
Capil membrane - imperm protein - ermeable most others
proteins only effective solutes - retain water & circ volume - plasma oncotic pressure only force retain intravascular volume
Vant Hoff
Why is the actual pressure higher
- Calculated ~15mmHg
- propt conc 0.9mOsm
Actual value - 25mmHg -
1 Gibbs donnan
2 Excluded volume
Net neg charge on protien - large - non readily diffusable
Retneon increase Na in plasma - gibbs donnan - net inc 0.4
Donnan excess pressure
Ret Na not bound Albumin - excess particles
Excluded boume effect
Large size of protein - van hoff ideal soluton - col ovvupy large mol wt protein signif adittiioanl factor discrep
How is oncoptic pressure measured
Oncometer - Two chambers - semi perm membrane - permeable to water - all solutes except mol wt >30000
Pressure measured trasnducer
Which protein calc most to osmotic
Albumin ~75%
Pl protein considered albumin glob fibro
Alb 45g/l
Net neg charge - major [prt responsible
Sudden decrease in plsama oncotic
Increased loss h20
Factors protect agianst oedema when albumin low
Increase lymph flow - remove ecvess ISF & return circulation
Inc ISF = Inc tissue hydrostaitc 0 further oppose excess filtration
Decrease insttestil protein - decrease albumin - decrease interstitial oncotic
Est Plasma Osm
2 Na + Glu + Ur
Sodium - typical value plasma
140 (135-145)
Intra cellular
12 - muscle
red cell 20
Why low
Na pump
3 Na out cell 2 K in
Sodium permeability
Low - prevents re renty
ISF Na
Should this be by the gibbs donnan?
140
Plasma consistant water 93% solids 7%
Solids - protein
Gibbs donnan causes Na plsam water than Na isf by 6 or 7
Gibbs donnnan causes Na in plsama water high than ISF by 6 or 7
Na is presesnt only in water component - measured whole. - decrease samll amt
‘Plasma solids effect’
Decreased measuredd Na same magnitude in Na - plasma Na d/t gibbs donnan
Result is measure Na as sameq
Why does the plasma Na only cotriubte to 0.4 of oncotic
Actual na in plsams water is only 7 mmols increase
Not only change electro conc
Cl lower plsama water & higher ISF - Gibbs donn
Na & cl - highest con plsama & isf -
Net change in ion not jkust na
diff increase 0.4 plsama - net increase osmolaity d/t gibbs donan 0.4 mOsm - overall protein 1.3mOsm
Net increase is only 0.5 0 fall in total anion cocnc offest rise Na
What is NaCl conc in plasma
0 - dissoc in ions
No undoss
Strong electoyle
How much sodium in the body
Tot body 60mmls/kg
4000-42000 adult male
ECF 50
Bone 45
ICF
Exchangeable Na 70%
If drop in ECF vol
Drop in Bp Drop in glo cap pressure Drop GFR Drop Na filter Increased tubular absoption Na - aldo
Pottasium - total body pottasium
40-45mmols/kg
ICF 90%
ECF 2%
Bone 8%
Bone - stable not read mobil can say 98% Intracell 2% excell
How total body K measure
Radioactive pottasium isotope
Functions of Pottasium
x5
Major component itracell tonicty
Na pump - all membr
Membrane potential
Regulation intracell processess
NM excitability
What are ECG change a/w hyperK
Decrease in RMP - hyperexcitability & reduced conduction velocity
typical progress Increase t wave Short Q-T Prolong P-R P wave flatter Progressive wide QRS Sine wave - VF / ASystole
How Rx
seveirty - absolute level & rate rise
- IV calcium - severe
plasma levele not alter bu inmcrease Ca - stabilise myocardial membrane - decrease excite
decrease risk serious arryh - Glucose & insulin
K move intracellular - Na bic
Decrease K - moving intracell & restore transmembrane K grad - Resonium
Ion exchange resin po / rectal - resin exchange 1 mmol kfor 1 mmol Na
Exchange occurs in Colon - PO slow - Dialysis
Preferred option severe CRF & ARF - Rx & cause
How much insulin
50mls 50% w/ 10u insulin aeffective
should decrease 1-*2 mmols 30 mins - persist for 2-3h
Dose can be prepeated
Redist K intracell - not cause excretion
What is reference range for Mg
0.7-4 mmol
1% - ECF - total amount 10mmols
40% protein bound
Functions of Mg
Cofactor in metabolism
action nerves muscle
Major intracell cation
Catalyst or cofactor
activating over300 sep enzyme body
Mg depend enzymes - calying phosphate tfer
thaimaonn pyrophos cof actor
Req sodium pump oxidtaive phsoprylation & all recation involving ATP - impratnt all cells without exception
Effects on nerves & muscles
Contrasted to those of calicum
Reduce nerve & muslce membrane excirtablity - sim calcium less powerfull
antagonitc - transmiiter release at cholin & adrenergic juncitopn
& exciate contract coupling
tmiter & excitrae cotract inhib mg
Clin effects - portetial NMB
Action SM - sim to skeletal & cardiac
effect - admin - vasodiln
Mg - def casposam & precp angina
Phsiolog bloc NDMA
Hypermag at plsam level
<4 asympto
Early - n/vb/drowsy
High levels - nmj & CVs
NM transiion impair - decrease deep tendon - resp paralysi
Minor ecg - ffrom CHB-> asystole
Monitoring - deep tendon reflex
Rx calcium gluctonaite
Hypomg
Myocolonus adbo pain htn angina tdp reentry arryhtmia
Use mg
Crease normal impulse propagation conditons Anaglesic asthma eclamspia Hypotens relax vessel -
Gibbs Donnan equilibrum
Semipermeable membrane - separates 2 soln - 1 soln non diffus anion / cation - dsitrb other diffusable cation & anion altered
Wquil products Na & Cl on each membrane - equal
Soln
Gibbs Donnan factor - univalent cations - 0.95
na In ISF 0.95 x Na plasma water - gibbs donnan factor anion is 1.05
Euil stable state
No - based ions distributing accorss embrane until elec & chemical gradients balanced - not stable unless fixed - quil stable - uneqal conc on 2 side - osmotic gradient - eleads water removal - upset queil
Divalent ion Ca & Mg
Colpiacted - protein bind - only conc - free ion used
divalted 0.9 cation
divalent anion 1.1
Gibbs Donnan effect improtant?
Stability cell volume
- non diff protein & organic phospahte - balanced - non iddusable na in ISF
Dynamic balance reposnilb eof rstability cell veolume
Plsama onctoic pressure - alter distrb other on - net increase ion in plsama - signif increase effective vlue plsama oncotic pressure in blood
Small contriobuion RMP
Lymph - How does ISF enter term lypahtic
Lmyph - ISF enter lympathic vessle
Lymph capul - present all tissue excepti cartil bm & CNS
Blind ending & flap valves - adjacent dentohelial - functional valve - entry of ISF - prevent eturn to tinsterstiom
Nearly all pass thru LNode - bvefore reutn to venous
Returns via thoraic duct drains in toc circ at junction L SC & LIJ & R lymph duct
What makes lymph flow
Intrinsic - walls ^ valves
Extrinsice - external pressure
Larger - sm in walls vavles -unidirect
Flows external pressure - copress vessels - flap valves between endothelial - capillary - rpevent return lymph to intsetitum - major soruce external pressure musclular contract & pulsation in neighbouring vessl
Functions
Rtuen of protein & excess frlud tio circ from ISF
Transport fat from sml intestin
Immunoligcal role
Remova bacteria - macrophage in glands (RES)
Role lympahtics lympthcyte cirtualtion throught blood & lymph
Role nodes - activated proliofarate contact antigent
Removal preotins keep ISF protein conc low
Maintains oncotic pressure gradient
Sinusioids - lined macropghages of RES = phagoctyose bacteria / cell debri
Nodes contain lymphocytes - prolif exposure antigent
Protein concentration of lymph
Low compared plasma - same as ISF- derived
20g/l
Hepatic can be up to 60
Liver 50% total body lymph rest - hepeatic sinusiod - permeable - protein leave circulation
Liver lymph causes thjoraic duct pteo conc 50g l
Diff between ISF & Lymph
Lymph is ISF - entered lymph channel
Thoracic duct hogher protein - protein rich hpeatic lymph
Thoracic duct drains into curlation @ junction L SC & IJ
How much lymph day
2mls/,om 120 hr 3l day
Total increase w/ exercise - actual amt variable
net filtration at arterial end - 20mls/min - 18mls min returns venous circulation
10% of all fluid - returns to cirulation lymph
What perecent retuns circulation via thoracic duct
83% 120mls/hr - include 100mls thoraic duct
Why is lymph milky?
High fat content - drain bowel after meal
What is the role lympahtic in fat aborsption
90% fat absorebed gut -extreuded ep cell isf - central lacteal vessels in villi
Fat form special globules - chlymicrons
respons milky appearance lymoh - cause milky appear plasma after fatty meal
Pass circulation via thoacic duct - not pass throuhg portal
Normal skin blood flow
_ factors control skin blood flow - skin requires for 2 reasons
Normal skin blood flow 300mls /min
1 metabolism - nutrients /waste removal
2 temperature regulation
Nutritive skin blood flow low - main factor - need heat loss
10x normal under heat stress
Increased sweat & evaporative loss
Increase loss warm skin rad conduction convection
Evap = effective heat loss gram water loss 0.58 kclas
‘insensible water loss’
Water passses thru skin - transepidraml diffusion - lost by evaporation skin suface
Evaportive water loss resp tract ventilation
insensible - unaware
Loss pure water
Loss not prevent
800mls day 400 + 400
Heat loss significant 464kcls - 25% basal heat
How is insens loss differe sweating
Solute free- only water
sweat solute - electolytes
Insne loss skin - water diffused thru skin
Sweat - glands
What is sweating - role
Secretion sweat gland skin - major role - increased heat loss situation stress Losses occur - water electolytes heat
Fluid loss occur with sweating
Eccrine sweat gland impraont sympthtic cholinergic (musc) innerv
hypotahlmus control = thermosense neuor hypothl - sense core
Fluid loss - extreme 2000mls / hour - max
Po replace
Solute loss
Na swat 30-65
depend allimitasion
na decrease aldo
Acclimitasion of sweting
adapting change - sweat mech cold to hot - max rate increase na decrease
benef loss heat
effective heat loss
very fective 1l evap skin = 580kclas
ecap skin heat low occur
if wiped or abosred towl - only water loss no heat loss
ambient temp & hmuidty imprat - det rate evap & thus loss
high humidity - marekdly decrease rate
signifcant of wsweating ill patient
Ill - body temp reising increase hyptoahl set point 0 skin dry & patient shivery
Set point decreaes stop shiver - sweat
causes heat los and fall temp
temp fall - anti pyretics not necc - fever will subside
What are the effects of insuing of 1L 3N saline
Very hypteoinc x3 paslam
fluid shifts
Na limit distrub ecf
water cross to osmolar grad
water drawn cell 0 until tonicty same both side
increase ecf vol 2.1 l - quater intravascular
Osmolatily increase above threholdblood bol increase
increased osmalt - sens osmrec hypothal - stim adh to retain water
thirst increase
increaevolume - lower livel snstiiivty - effect volurectpor inhib adh - allow water
volume stimuli less sesn more ptoent osmotic
Effect on Na- vol expan stim secr ANF
secretion aldo inhib cause of decrease renin & AgII
ANF also inhib renin
Final outcome - natriresis &e xcretion excess water - increased osmolaity - incraesed adh inhib rate exretion water
decrease ICF volume - effects brain - confsuion obrundation derebral dellular dehyradtion & hypetonicty - effects will probedom clin effects - function unlikely aeffect
