Les HôpitauxUniversitairesde STRASBOURG
The role of acute hemodialysis in pediatric intensive care :
new technological advanceson line equipments : tools or toys?
M. Fischbach
Children Dialysis Unit
Strasbourg - France
Les HôpitauxUniversitairesde STRASBOURG
• Intermittent hemodialysis techniques especially in case of either
major hemodynamic instability or « too shortened » dialysis times
(acute osmotic changes), and overall logistic factors (implication of
the nephrological team), could adversely affect the quality of an
acute intermittent dialysis procedure, therefore continuous
hemodialysis (hemofiltration) are often advocated as « superior ».
• Nevertheless slow low efficiency on line HDF offers a
«nephrological» dialysis prescripiton, with a magnitude of
individually adapted prescription as often needed for a critically ill
patient hemodinamically instable and hypercatabolic (on-line
dialysis tools equipment especially, continuous determination of the
blood volume),
acute hemodialysis: continuous or intermittent ?
Les HôpitauxUniversitairesde STRASBOURG
Slow low efficiency dialysis : a new gold standard ?
• Today ARF is generally one feature of a multiorgan dysfunction syndrome in critically ill children, usually hemodinamically instable and hypercatabolic
• The choice of renal replacement modality either CVVHD or sustained low efficient hemodialysis, should consider the dual need : * hyghly efficacious elimination of uremic toxins *and concomitant gentle volume removal
Technology insight: tretment of renal failure in the intensive care unit with extended dialysis. D Fliser, Jt Kielstein.Nature Clinical Practice Nephrology.2006:32-9
Les HôpitauxUniversitairesde STRASBOURG
Slow low efficiency dialysis : a new gold standard ?
• Conventional hemodialysis with a low dialysate flow and a long duration (8 or more hours): « gentle » ultrafiltration and « progressive » osmotic changes
• Easy to perform, available material, discontinuous/intermittent, reasonable team demand
• Slow UF rate per hour (zero balance UF prior dialysis connection) : optimal vascular tolerance
• Low K per hour : optimal osmotic tolerance, but sufficient treatment dose (hypercatabolic patients)
• High Kt/V : good prognostic/outcome factor
• Highly efficient membranes : chance of recovery, biocompatibility
• Dialysate : bicarbonate as buffer, glucose, NaD, K, Ca2+
Technology insight: tretment of renal failure in the intensive care unit with extended dialysis. D Fliser, Jt Kielstein.Nature Clinical Practice Nephrology.2006:32-9
Les HôpitauxUniversitairesde STRASBOURG
During the past decades many improvement in hemodialysis technology occured :
• Volumetrically control of the ultrafiltration,even the availability of profiled UF/NaD
• Bicarbonate dialysate buffer
• Smaller lines and membranes for infants
• Biocompatible membanes (highly efficient)
• Hemodiafiltration on line with ultrapure dialysate, (reduced continuous inflammation: microCRP)
• And on line equipments…..
Les HôpitauxUniversitairesde STRASBOURG
On line equipments : power tools for (acute) hemodialysis
• Blood volume monitoring : « vascular refilling capacity »
• Blood thermal monitoring : isothermic dialysis (thermoneutral), cool
temperature dialysis, regional blood flow redistribution risk
managment (vasoconstriction)
• Profiled prescriptions: UF total and rate (continuous/intermittent),
NaD (high or low dialysate concentrations)
• Urea clearance (OCM : on line clearence measurement) and
dialysis dose measurement, dialysis efficiency/osmotic risk
Les HôpitauxUniversitairesde STRASBOURG
Slow low efficiency on line HDF
• Access : veino veinous, catheter • Membrane biocompatibility: high permeability, chance of recovery• Anticoagulation : low MW, but either free in predilution mode or
citrate Na conducted • Dialysate flow modulable and, base : bicarbonate (+ acetate)• Replacement fluid (pre/postdilution): bicarbonate (+ acetate)• Solute clearance mechanism : diffusion and convection• Duration : 6-12 hours• Tools/ toys : BVM, BTM, UF and Na modelling, predilution (mixed
pre-post), Kt/Vurea on linemeasurement, change from sequential UF, to HF, to HD, to HDF, to pre or/and post dilution (without changing the dialysis set)
• Cost : water quality, membrane, dialysis and replacement fluids
Les HôpitauxUniversitairesde STRASBOURG
Blood flow and catheter size (diameter)
Radius : 1 mm Blood flow 1
Radius : 0,5 mm Blood flow 1/16
Radius : 0,25 mm Blood flow 1/32
Poiseuille law : QB = x r 4
Flow through a tube varus with the 4th
power of it radius
A single but large lumen catheter offers for small children a better flow compromise than a double small lumen catheter
Les HôpitauxUniversitairesde STRASBOURG
Dialysis membranes : practical parameters
• Type of membrane : biocompatibility• Initial blood volume need, ie area related, quality
of blood restitution, heparin demand• Molecular permeability : maximal clearance for
urea (osmotic risk) and other uremic toxins, ie phosphate and cytokins+++
• Hydraulic permeability : possibility of use for HF or HDF procedure ; back filtration risk
• Cost, need (purification molecular spectrum) , diuresis recovery hope
Les HôpitauxUniversitairesde STRASBOURG
The dialysate : adaptable, and « ultra »pure
• Dialysate flow : low flow should be available (300ml/min or less)
• Bicarbonate buffered (controlled alkalinisation, concentration flexible)
• Low calcium level (1.25 mmol L-1) becomes the standard for chronic
dalysis, but for acute HD higher concentrations (1. 75 mmol L-1) are
more appropriated (cardiac inotropic impact)
• Adaptable concentration of sodium (132 to 150), kalium (not a too
important blood/dialysate gradient due to the cardiac arythmia risk)
• Glucose concentration at physiological level
• Dialysate quality control is required (germs and endotoxins), if highly
permeable membranes are used (of course in on-line HDF
configuration) : ultrapure dialysate+++
Les HôpitauxUniversitairesde STRASBOURG
Ultrapure dialysate
• Improved nutritional status (Schefftel H et al. NDT 2001)
• Reduced inflammation, AGE accumulation, amyloidosis (corporel tunnel syndrome) (Gerdeman A et al. NDT 2002)
• Lowered cardiovascular mortality (Lederer SR et al. Nephron 2002)
• Preserved renal residual function Schefftel H et al. NDT 2002) : renal recovery ???
Les HôpitauxUniversitairesde STRASBOURG
Principles of blood purification
• Diffusive Process (HD) : low MW uremic toxins removal i.e.urea
• Convective mass transport (HF) : middle Mw uremic toxins removal i.e.phosphate
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
HD
HF
HDF
Les HôpitauxUniversitairesde STRASBOURG
Blood purification dialysis modalities :
diffusion versus convection
Diffusive Process
(hemodialysis)
Membrane area
Mass transport coefficient
Concentration gradient
Blood flow x extraction coefficient ci - co
KHD = QB x ci
i, o : in outlet solute concentrations
Convective mass transport(hemofiltration)
Ultrafiltrate flow (QUF)Hydraulic permeabilityTransmembrane pressure (TMP ; mmHg)Sieving coefficient (S)*
2 CUF
*S = ci+co
CUF : ultrafiltrate solute concentration
KHF = QUF x S (postdilution)
QB x QUF
KHF = x S (predilution) QB - QUF
Les HôpitauxUniversitairesde STRASBOURG
Simultaneous purification: diffusion process and
convection mass transport i.e. hemodiafiltration
KHDF = KHD + x QUF x 0.46
KHDF = KHD (1 - QUF x S/QB) + KHF (Granger)
with QUF x S = KHF and QB = Kmax
KHD x KHF QHDF = KHD + KHF- Kmax
one minute of dialysis « is equal» to two minutes of purification, one of HD and another one of HF
If KHF is equal to Kmax then QHDF= KHD
Les HôpitauxUniversitairesde STRASBOURG
HDF versus HD : advantages
• Hemodynamic stability over the session
* increased tolerance to weight loss, and blood pressure
control improvement (hemofiltration effect)
* osmotic stability, compartment preservation,
peripheral vascular resistances, myocardial contractility
• Optimal blood purification capacities both for urea and
inflammatory/catabolic agents
• Optimized hemocompatibility : bicarbonate dialysate, synthetic
membrane, retrofiltration control, ultrapure dialysate
• Individual adaptadive prescription : easy switch from HDF to
HF to HD to sequential « isolated » UF (isoosmotic)
Les HôpitauxUniversitairesde STRASBOURG
Hemodiafiltration : pre/post dilution
Substitution solution
QB in QBout
pre-dilution post-dilution
Addition of substitution solution in HDF can be made before thefilter , predilution mode, or after the filter , postdilution mode
In HDF addition of substitution solution can be made before the filter called predilution mode, or after the filter, postdilution mode
Les HôpitauxUniversitairesde STRASBOURG
Hemodiafiltration modalities
• Conventional HDF: :
substitution fluid (bags) with « balanced »
compensation, not more applied (cost)
• High flux hemodialysis i.e. internal HDF : highly
permeable membranes with retrofiltration due to the
high hydraulic permeability coefficient
• On line HDF : substitution fluid produced from the
ultrapure dialysate +++
Les HôpitauxUniversitairesde STRASBOURG
During the past decades many improvement in hemodialysis technology occured :
on line equipments , tools or toys ?
• BVM +++ , relative blood volume variation (reduction), hypotensive riks, dry weight adjustment
• BTM, controlled « cooled » dialysis, reduced thermic dialytic loss
• Modelling of the UF rate and sodium in the dialysate (NaD): individual patients profiles
• Ionic dialysance : on-line KT/V determination, vascular access blood flow measurement
BVM
KT/V
Les HôpitauxUniversitairesde STRASBOURG
Hypotension : a multifactorial event, dialysis impacted
• Cardiac rythm, and contractility : *dialysate Ca++, *optimal purification (cytokines)
• Vascular resistances : *bicarbonate dialysate, *temperature control…
• Blood volume : *preservation, despite need for weight loss, *ultrafiltration versus plasma refilling from the interstitial space
Les HôpitauxUniversitairesde STRASBOURG
During the past decades many improvement in hemodialysis technology occured :
tools or toys ?
• BVM +++ , relative blood volume variation (reduction), hypotensive riks, dry weight adjustment
• BTM, controlled « cooled » dialysis, reduced thermic dialytic loss
• Modelling of the UF rate and sodium in the dialysate (NaD): individual patients profiles
• Ionic dialysance : on-line KT/V determination, vascular access blood flow measurement
BVM
Les HôpitauxUniversitairesde STRASBOURG
Non-invasive monitoring of Hematocrit (NIVM) : principle
• Red cell volume « remains constant » during dialysis
changes (bleeding ?)
• Hematocrit and intravascular volume changes are
inversely proportional
Hct0 x BV0 = Hctx x BVx 5% Hct = 15% BV Δ BV % = 100 x (BV0 - BVx/BV0) = 100 x (Hctx - Hct0)/ Hct0
Les HôpitauxUniversitairesde STRASBOURG
Should relative blood volume (RBV) changes be routinely measured during dialysis session ?
Basile C. Nephrol Dial Transplant 2001; 16:10-22
The answer is definitively yes, at least obviously in the case of
hypotension prone patients for the following reasons :
• Hypotensive episode occurrence decreases
• Non invasive method, and relatively inexpensive
• Possibility of further developments : automatic retrocontrol
biofeedback technology, information about real hematocrite?
• BV decrease should be limited (?) to less than 15% ( 5% Ht
increase ) per dialysis session
• BV refilling capacity should be analysed, to optimize ultrafiltration
prescription
Les HôpitauxUniversitairesde STRASBOURG
0
5
10
15
0 60 120 180 240
TD (min)
1
3
4
2
BV % Routine use of NIVM for
chronic dialysis:
• helps to achieve the target dry
weight,
• reduces both the risk of chronic fluid overload and the
need for antihypertensive medication,
• lead to decrease the intradialytic symptomatology,
• And perhaps, allows better residual diuresis preservation
Blood volume monitoring to achieve target weight in pediatric hemodialysis patients
Michael M, Brewer ED, Goldstein SL.Pediatr Nephrol 2004; 19:432-7
Les HôpitauxUniversitairesde STRASBOURG
Non-invasive intravascular monitoring (Ht) in the pediatric
population Jain SR et al. Pediatr Nephrol 2001; 16:15-18
• UFR with BV change < 8 % per hour is safe in the 1st hour and
4 % thereafter (NaD 140 mmol/L ; no profile neither NaD nor UF)
• no more than 12 % over a whole session :
*time for plasma refilling occurence ,
*recruitment of the « interstitial » water,
*preservation from cellular water shift
• dBV/Dt = UFR – PRR
0
5
10
15
0 60 120 180 240
TD (min)
1
3
4
2
BV %
Les HôpitauxUniversitairesde STRASBOURG
« Blood volume, Ht » monitoring allows an on line assessment of the
balance between
• ultafiltrate rate and volume
• vascular refilling capacity
• cellular water shift
d BV/dt = UFR – PRR
if PRR is able to compensate UFR,
vascular compartment will be preserved
Les HôpitauxUniversitairesde STRASBOURG
vascular : oncotic (proteins) pressure
extracellular : osmotic (Na) pressure
intracellular : osmotic gradient (urea dysequilibrium)
d BV/dt = UFR – PRR
compartment « water »shifts :
vascular
ultrafiltration
UF rate,volume
urea
Les HôpitauxUniversitairesde STRASBOURG
Compartment shitfs , water and solutes, extracellular (vascular, interstitial) and cellular
compartments : multifactorial
Pressures : hydrostatic ; osmotic crystalloid (Na , urea , glucose) ; osmotic colloid(proteins)
Wall permeability : membranes vessels , cells
Regional blood flow : *cardiac flow , *peripheral vascular resistances (hypovolemia, acidosis, cooled dialysate….) *extra/intra cellular functional compartments
Les HôpitauxUniversitairesde STRASBOURG
Ultrafiltration tolerance : rate(ml/h) more than total
amount(ml/session)BV preservation,hemoconcentration : osmotic colloid pressure enhancement (proteins,Na,nutrition…)PRR,water shift from the interstitial to the vascular compartment facilitated by : *low/intermittent UF ; *oncotic vascular pressure ; *degree of interstitial repletion (water/Na overload);
*Na(dialysate/blood/interstitial)Water shift from the cells to the extracellular compartment due to the osmotic «cristalloid »gradient ( urea , Na , ,glucose , PVR )Patient whole condition : cardiac output, nutrition,catabolism…
Les HôpitauxUniversitairesde STRASBOURG
factors affecting plasma refilling capacity: dBV/Dt = UFR – PRR
• Individual state of hydratation (interstitial compliance, water and Na)
• Dialysate sodium concentration (osmotic)
• Plasma protein concentration (oncotic)
• Capillary permeability, cardiovascular reactivity, dialysate composition and temperature, urea reduction rate...
Les HôpitauxUniversitairesde STRASBOURG
Continuous blood volume monitoring and ultrafiltration control
Lopot et al, Hemodial Int 2000; 4:8-14
Type 1 constant BV, flat line throughout
the whole dialysis
Type 2 constant BV during a first part of
dialysis followed by a roughly linear
decrease
Type 3 linear decrease of BV from
dialysis start until the end with a
constant declining slope
Type 4 linear decrease of BV with a
variable declining slope
0
5
10
15
0 60 120 180 240
TD (min)
1
3
4
2
BV %
Les HôpitauxUniversitairesde STRASBOURG
Continuous blood volume monitoring and ultrafiltration control
Lopot et al, Hemodial Int 2000; 4:8-14
Type 1 : constant BV throughout
the whole dialysis or nearly flat
line or « BV water gain »
• PRR is able to fully compensate
UFR
• Fluid overload in the interstitial
space
• Dry weight adjustment need
(inferior vena cava diameter)
0
5
10
15
0 60 120 180 240
TD (min)
1
3
4
2
BV %
Les HôpitauxUniversitairesde STRASBOURG
Continuous blood volume monitoring and ultrafiltration control
Lopot et al, Hemodial Int 2000; 4:8-14
Type 3 or 4 : linear decrease of BV
with an individually variable slope
• Avoid a whole session decrease of
more than 15% BV (Ht 5%) high risk
for clinical intolerance
• Don ’t change DW without adapted
dialysis prescription (UFR, NaD, TD)
0
5
10
15
0 60 120 180 240
TD (min)
1
3
4
2
BV %
Les HôpitauxUniversitairesde STRASBOURG
d BV/dt = UFR – PRR
• if PRR is able to compensate UFR there will be no
change in BV, low hypotensive risk , «adequate»
tissular perfusion
• BV behavior gives more informations on the
appropriatness of the «UF rate» than on the «total UF
volume» achieved
• BV changes over time allows to test the plasma
refilling capacity, that is the BV profile induced by
UF=0,the water shift capacity from the interstitium to
the vascular or to the cellular space
d BV/dt = UFR – PRR
Les HôpitauxUniversitairesde STRASBOURG
Normal decrease of BV, at dialysis initiation, usually 5 to 8 % during a « short » time i.e. 5 to 30 minutes, this phenomena could be « controlled » and limited if needed :
• Fill the patient before filling the extracorporeal space• Limit the extracorporeal blood space• Fill the extracorporeal space with « blood » before patient connection, or better don’t flush the extracorporeal space before connection to the patient
Dialysis start : BV usually decrease
Les HôpitauxUniversitairesde STRASBOURG
• UFR induces BV change : dBV/Dt = UFR – PRR
• In case of a to important decrease of BV ( change of 8 % or more in the 1st hour ), the ability of plasma refilling occurrence should be tested (stop UF, note BV behavior)
• In case of plasma refilling occurence, that is water transfer
from the interstitial space to the vascular space, UF can be prolonged, no or low risk of hypotension episode
Les HôpitauxUniversitairesde STRASBOURG
Plasma refilling rate is influenced by :
• changes in UF : rate, profile (intermittent+++)• NaD increase : water shift from the interstitial to the vascular compartment ( transiet effect and, sodium « charge »risk) • Dialysate cooling (vasoconstriction, balanced by compartment purification)• Urea clearance reduction (less intracellular water shift)
Les HôpitauxUniversitairesde STRASBOURG
UF reserve capacity
• overloaded patient, • excess of compensatory factors for BV preservation, to high NaD ?
Les HôpitauxUniversitairesde STRASBOURG
• BVM over the dialysis session should be performed routinely in almost all children (each session)
• BVM allows an objective perception of compartment water recruitment for ultrafiltration (vascular refilling)
• BVM gives more information on UF rate than on UF total amount tolerance
• BVM could help for a more objective dialysis prescription
- session duration, -NaD,TD,
-UFprofile , - URR , dry weight goal
Les HôpitauxUniversitairesde STRASBOURG
During the past decades many improvement in hemodialysis technology occured :
tools or toys ?
• BVM +++ , relative blood volume variation (reduction), hypotensive riks, dry weight
• BTM, controlled « cooled » dialysis, reduced thermic dialytic loss
• Modelling of the UF rate and sodium in the dialysate (NaD): individual patients profiles
• Ionic dialysance : on-line KT/V determination, vascular access blood flow measurement
BVM
KT/V
Les HôpitauxUniversitairesde STRASBOURG
Blood thermal monitoring
• Thermal balance control : isothermic dialysis,
thermoneutral dialysis (catabolism)
• Cool temperature dialysis, warmed dialysis :
– Blood pressure preservation, vasoconstriction
– Regional blood flow redistibution, share of compartmental
purification/limitation
Les HôpitauxUniversitairesde STRASBOURG
Total body water: urea « mere » container, pools of
distribution• Intracellular 2/3 ; extracellular 1/3 : notion of
two body compartments (cellular wall)
• Skin, muscle, osseous tissues accounts for
80% TBW, despite receiving only 20% cardiac
blood outflow : notion of two circulatory
compartments (regional blood flow )
Les HôpitauxUniversitairesde STRASBOURG
Dialysate temperature modelling in children on hemodiafiltration : conflicting impacts on
hemodynamic stability versus dialysis efficiencyM. Fischbach et al. J Am Soc Nephrol 2001; 12:A2317
• There is a beneficial role of cooled dialysate in
promoting hemodynamic stability
• Cooling induces vasoconstriction i.e. a
potential factor of thermally induced decrease
in regional blood flow with compartmental
disequilibrium ; conversely a warmed dialysate
should optimized regional blood flow
improving urea removal (regional blood flow
theory, Schneditz)
Les HôpitauxUniversitairesde STRASBOURG
Haemodiafiltration with standard temperature dialysate (37°C) in children induces an energy loss
M. Fischbach et al. J Am Soc Nephrol 2001; 12:A1687
Begin End
Tcentral 36.90.18* 37.30.24*
Tax 36.10.22** 35.40.15**
Energy transfer
KJ (kilojoules)
ND -12431
The usually prescribed dialysate temperature of 37°C didn ’t allowed for children thermoneutral haemodiafiltration
Les HôpitauxUniversitairesde STRASBOURG
URR%
TD profiled TD fixed (37°C)
first hour
Session
49+12
736
35+9*
638**
Energy transfer per session
KJ
- 6724
-124131***
TD profiled : first hour 38°C (TD) second hour ET = 0 (TD) third hour 36°5 C
M. Fischbach et al. J Am Soc Nephrol 2001; 12:A2317
Effect of profiled dialysate temperarure
Les HôpitauxUniversitairesde STRASBOURG
During the past decades many improvement in hemodialysis technology occured :
tools or toys ?
• BVM +++ , relative blood volume variation (reduction), hypotensive riks, dry weight adjustment
• BTM, controlled « cooled » dialysis, reduced thermic dialytic loss
• Modelling of the UF rate and sodium in the dialysate (NaD): individual patients profiles
• Ionic dialysance : on-line KT/V determination, vascular access blood flow measurement
BVM
KT/V
Les HôpitauxUniversitairesde STRASBOURG
Sodium of the dialysateDiffusion, high NaD : - from dialysate to vascular , then to the interstitial compartment, with a « transiet » gradient between the vascular/interstitial compartments : potential « vascular water shift » -but Na «storage» in the interstitial space, with induction of interstitial oedema, and extra/intra cellular osmotic gradient (preservation from celluar « oedema »)
Convection, high interstitial Na: (cellular wall impermeability) generates water shift (intra to extra ; free Na water) and solute shift (convective cellular wash out), « counterbalanced » by intracellular urea « retention »
Les HôpitauxUniversitairesde STRASBOURG
Ultrafiltration and sodium modeling : an efficacious trick, but could be at risk
• Able to limit dialysis morbidity, vascular instability
• Allow optimized ultrafiltration, in case of hypotension despite fluid
overload : intermittent UF should be appied +++ (refiling time)
• Risk of enhanced interdialytic weight gain, positive sodium balance
with interstitial oedema in case of too high, inadapted NaD
• Impact on purification : tissue perfusion, cellular washout
• 144 mmol/l is the « normal » plasma Na concentration :
NaD should be adapted to the evolutive, individual patient needs
Les HôpitauxUniversitairesde STRASBOURG
During the past decades many improvement in hemodialysis technology occured :
tools or toys ?
• BVM +++ , relative blood volume variation (reduction), hypotensive riks, dry weight adjustment
• BTM, controlled « cooled » dialysis, reduced thermic dialytic loss
• Modelling of the UF rate and sodium in the dialysate (NaD): individual patients profiles
• Ionic dialysance : on-line KT/V determination, vascular access blood flow measurement
BVM
KT/V
Les HôpitauxUniversitairesde STRASBOURG
Urea dialysis dose : Kt x Vurea
• K : blood flow, dialyzer membrane capacity
• t : uremic toxins kinetics, single or double pool (intra-extra
cellular ; regional blood flow), multicompartmental : diffusibility
of the toxins
• Vurea :
– Urea pool
– Total body water : hydratation and nutrition
– V, is the volume of distribution of urea, total body water calculated
from gender specific normograms, it is also a surrogate of nutrition
Les HôpitauxUniversitairesde STRASBOURG
Estimating TBW in children on the basis of height and weight : a reevaluation of the formulars of Mellits and CheekMorgenstern B, Mahoney D, Warady B, JASN 2002; 13:1884-8
• Infants 0 to 3 m (n = 71) : 0.887 x (Wt)0.83
• Gender specific normograms :
–Children 3 mo to 13 yr (n =167) : TBW = 0.0846 x 0.95[if female] x (Ht xWt)0.65
–Children > 13 yr (n = 99) : TBW = 0.0758 x 0.84[if female] x (Ht x Wt)0.6
Anthropometric prediction of TBW in children on PD Morgenstern B, Wuhl E, Sreekumaran NK, Warady B, Schaefer F.JASN 2005
• Gender specific normograms:
–Males : TBW=0.086x(heightxweight)0.680-0.21xweight
–Females : TBW=0. 112x(heightxweight)0.658_-0. 328xweight
Les HôpitauxUniversitairesde STRASBOURG
Urea dialysis dose : Kt x Vurea
• Urea « osmotic » clearance has a direct impact on intracellular water shift (osmotic sydrome), be not too fast : vascular stability, neurological tolerance
• Kt x Vurea of 0.15 per hour , is sufficient to reach a
dialysis dose of 1.5 over a 10 hours dialysis session
• Potassium clearance is nearly 80% of Kt x Vurea
• Effect of time per se on final outcome : intermittent is not necessary too short dialysis time, it should be strongly influenced by the need to optimize vascular volume status and to preserve cellular space
Les HôpitauxUniversitairesde STRASBOURG
On line equipments : power tools for acute hemodialysis
not too tricky tricks• Blood volume continuous monitoring (BVM) : refilling capacity test, secured
and optimized UF
• Blood thermal monitoring (BTM) : vascular stability, regional blood flow
potential impact
• HDF procedure : allowed sequential UF, HF, HD, adapted to the individual
patient needs, and evolution; on-line HDF provide for the restitution-
hemofiltration fluid (possibility for adapted sodim concentration)
• Profiled prescriptions: UFrate at the best intermittent (refilling time), NaD not
too high (interstitial storage,oedema)
• Clearance and dialysis dose measurement, dialysis efficiency: slow (urea
osmotic tolerance) but controlled purification (potassium gradient)
Les HôpitauxUniversitairesde STRASBOURG
Steep wise initial prescription : massive fluid overload with interstitial
oedema, coma• HDF predilution, QUF2/3 of QB (osmotic « stability »),• Osmotic gradients :
* plasma oncotic pressure (maintain « albuminemia »), * cristalloid gradient (NaD but will move in the interstitium)
• UF rate (weight loss about 0.5 to 1% BW per hour in the acute phase) under BVM control, BV reduction limited to 10/15%
• Vascular instability or preservation of BV : * reduce dialysate temperature, * limit « urea » osmotic clearance, * profile intermittent UF, but limit interstitial sodium « charge » (NaD)
Les HôpitauxUniversitairesde STRASBOURG
• Slow low efficiency dialysis : a new gold standard • On line equipments : power tools for acute hemodialysis
MERCI