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The role of acute hemodialysis in pediatric intensive care : new technological advances on line equipments : tools or toys? M. Fischbach Children Dialysis.

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Presentation on theme: "The role of acute hemodialysis in pediatric intensive care : new technological advances on line equipments : tools or toys? M. Fischbach Children Dialysis."— Presentation transcript:

1 The role of acute hemodialysis in pediatric intensive care : new technological advances on line equipments : tools or toys? M. Fischbach Children Dialysis Unit Strasbourg - France

2 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 ?

3 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

4 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, Na D, K, Ca 2+ 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

5 During the past decades many improvement in hemodialysis technology occured : Volumetrically control of the ultrafiltration,even the availability of profiled UF/Na D 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…..

6 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

7 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/V urea 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

8 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 : Q B = x  r 4 Flow through a tube varus with the 4 th power of it radius A single but large lumen catheter offers for small children a better flow compromise than a double small lumen catheter

9 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

10 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+++

11 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 ???

12 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

13 Blood purification dialysis modalities : diffusion versus convection Diffusive Process (hemodialysis) Membrane area Mass transport coefficient Concentration gradient Blood flow x extraction coefficient c i - c o K HD = Q B x c i i, o : in outlet solute concentrations Convective mass transport (hemofiltration ) Ultrafiltrate flow (Q UF ) Hydraulic permeability Transmembrane pressure (TMP ; mmHg) Sieving coefficient (S)* 2 C UF *S = c i +c o C UF : ultrafiltrate solute concentration K HF = Q UF x S (postdilution) Q B x Q UF K HF = x S (predilution) Q B - Q UF

14 Simultaneous purification: diffusion process and convection mass transport i.e. hemodiafiltration K HDF = K HD + x Q UF x 0.46 K HDF = K HD (1 - Q UF x S/Q B ) + K HF (Granger) with Q UF x S = K HF and Q B = K max K HD x K HF Q HDF = K HD + K HF - K max one minute of dialysis « is equal» to two minutes of purification, one of HD and another one of HF If K HF is equal to K max then Q HDF = K HD

15 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)

16 Hemodiafiltration : pre/post dilution Substitution solution Q B inQ B out pre-dilutionpost-dilution Addition of substitution solution in HDFcan bemadebeforethe filter,predilutionmode, orafterthefilter,postdilutionmode In HDF addition of substitution solution can be made before the filter called predilution mode, or after the filter, postdilution mode

17 He modiafiltration modalities ConventionalHDF: : 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 +++

18 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

19 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

20 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

21 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

22 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

23 TD (min)  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

24 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 (Na D 140 mmol/L ; no profile neither Na D 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 TD (min)  BV %

25 « 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

26 vascular : oncotic (proteins) pressure extracellular : osmotic (Na) pressure intracellular : osmotic gradient (urea dysequilibrium) d BV/dt = UFR – PRR compartment « water »shifts : vascularvascular ultrafiltration UF rate, volume urea

27 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

28 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…

29 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...

30 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 TD (min)  BV %

31 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) TD (min)  BV %

32 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, Na D, T D ) TD (min)  BV %

33 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

34 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

35 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

36 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)

37 UF reserve capacity overloaded patient, excess of compensatory factors for BV preservation, to high NaD ?

38 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, - Na D,T D, - UFprofile, - URR, dry weight goal

39 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

40 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

41 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 )

42 Dialysate temperature modelling in children on hemodiafiltration : conflicting impacts on hemodynamic stability versus dialysis efficiency M. 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)

43 Haemodiafiltration with standard temperature dialysate (37°C) in children induces an energy loss M. Fischbach et al. J Am Soc Nephrol 2001; 12:A1687 The usually prescribed dialysate temperature of 37°C didn ’t allowed for children thermoneutral haemodiafiltration

44 T D profiled : first hour38°C (T D )second hourET = 0 (T D ) third hour 36°5 C M. Fischbach et al. J Am Soc Nephrol 2001; 12:A2317 Effect of profiled dialysate temperarure

45 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

46 Sodium of the dialysate  Diffusion, high Na D : - 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 »

47 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 Na D Impact on purification : tissue perfusion, cellular washout 144 mmol/l is the « normal » plasma Na concentration : Na D should be adapted to the evolutive, individual patient needs

48 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

49 Urea dialysis dose : Kt x V urea 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 V urea : –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

50 Estimating TBW in children on the basis of height and weight : a reevaluation of the formulars of Mellits and Cheek Morgenstern B, Mahoney D, Warady B, JASN 2002; 13: Infants 0 to 3 m (n = 71) : x (Wt) 0.83 Gender specific normograms : –Children 3 mo to 13 yr (n =167) : TBW = x 0.95 [if female] x (Ht xWt) 0.65 –Children > 13 yr (n = 99) : TBW = 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) xweight –Females : TBW=0. 112x(heightxweight) 0.658_ xweight

51 Urea dialysis dose : Kt x V urea Urea « osmotic » clearance has a direct impact on intracellular water shift (osmotic sydrome), be not too fast : vascular stability, neurological tolerance Kt x V urea 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 V urea 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

52 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), Na D not too high (interstitial storage,oedema) Clearance and dialysis dose measurement, dialysis efficiency: slow (urea osmotic tolerance) but controlled purification (potassium gradient)

53 Steep wise initial prescription : massive fluid overload with interstitial oedema, coma HDF predilution, Q UF 2/3 of Q B (osmotic « stability »), Osmotic gradients : * plasma oncotic pressure (maintain « albuminemia »), * cristalloid gradient (Na D 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 » (Na D )

54 Slow low efficiency dialysis : a new gold standard On line equipments : power tools for acute hemodialysis MERCI


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