2. AKI affects 5% of hospitalized patients
Leads to increased mortality and morbidity
NEED OF THE HOUR
3. Principles
All forms : movement of solute or water or both across semipermeable membrane
Fluid removal : Ultrafiltration
Solute removal : diffusion and convection
4. Ultrafiltration
Process of fluid removal across SP membrane
Removal by application of hydrostatic pressure or osmotic pressure
Most machines use : hydrostatic pressure
5. Solute clearance
Removal of solute across semipermeable membrane
By Diffussion : movement of solute from High conc to Low Conc
By Convection : SOLVENT DRAG : Solute swept via SP Membrane by moving stream
of UF
6. Hemodialysis : Removal of water and solutes by diffusion across conc. Gradient
Adequate clearance of small molecules : Urea(60) & Creatinine (113)
Hemofiltration : NO DIFFUSSION … NO DIALYSATE USED … ONLY CONVECTIVE
TRANSPORT
Insufficient for solute removal
Better for MIDDLE SIZED MOLECULES : cleared by convective transport
7.
8. Adsorption
1. Molecular adherence to the surface or interior of the membrane
2. This mechanism is used in:
SCUF
CVVH
CVVHD or CVVHD with ultrafiltration
CVVHDF
9. Small molecules easily pass through a membrane driven by diffusion and
convection.
Middle and large size molecules are cleared primarily by convection.
Semi-permeable membrane remove solutes with a molecular weight of up to
50,000 Daltons.
Plasma proteins or substances highly protein—bound will not be cleared.
10. Sieving Cofficient
Ability of a substance to pass from the blood compartment of hemofilter to fluid
compartment across SP membrane
Depends upon MW and protein binding of a substance
1: free passage of substance
0 : Unable to pass
11. Substance Sieving Coeff
Na 0.97-1
K 0.92
Ca 0.7
Albumin <0.01
Urea 0.7-1.06
Creat 0.7-1.04
Myoglobin 0.55
12. KT/V
A number used to quantify hemodialysis and peritoneal dialysis treatment
adequacy.
K - dialyzer clearance of urea
t - dialysis time
V - volume of distribution of urea, approximately equal to patient's total body water
Kt/V target is ≥ 1.3 HD
In peritoneal dialysis the target is ≥ 1.7/week.
13. Example,
Infusing four 2 liter exchanges a day, and drains out a total of 9 liters per day, then
they drain 9 × 7 = 63 liters per week.
If the patient has an estimated total body water volume V of about 35 liters,
then the weekly Kt/V would be 63/35, or about 1.8.
14. Requisites of Ideal RRT
1. Control Volume overload
2. Control Electrolyte disturbances
3. Control acid base disturbances
4. Provides clearance of solutes
5. Associated with minimal complications : Hypotension Bleeding
15. Types of RRT : Basis of Duration
Intermittent
3-4 hrs
IHD PD IUF
Continuous
24 hrs
CVVH CVVHD CVVHDF SCUF PD
Hybrid
Few to 24
hrs
SLED
16. Choice of Modality
Based on four factors
1. Patient’s age & size
2. Cardiovascular status
3. Vascular access is available / Conditon of peritoneal membrane
4. Available expertise
17.
18. Indications of RRT
Fluid overload
Uremic encephalopathy
Hyperkalemia persistent
Severe metabolic acidosis
Hyper or hyponatremia
19. Peritoneal dialysis
Simple & safe
Vascular access not required
Advantage for small children
No anticoagulation
CONS:
Excessive ultrafiltration lead to significant hemodyanamic instability
Insertion of catheter : expertise
Infections : catheter related
20. Cathetors
Non Cuffed Rigid acute cathetor : max upto 72 hours : Infection
Tenkckhoff catheter – Single cuffed(Bedside) , double cuffed(Surgically)
21. Proximal Cuff : Implanted in Pre peritoneal space , Holds catheter in place
Distal Cuff : In SC tissue , Acts as barrier to infection
22. Blockage by the omentum is always a risk with PD catheters.
If the catheter is to be placed surgically then consideration should be given to
partial omentectomy
In patients who are having a PD catheter inserted under general anesthetic a
cephalosporin antibiotic (20 mg/kg) should be given as a single intravenous dose
up to 1 h prior to implantation of the catheter .
Any subsequent accidental contamination should result in the use of prophylactic
antibiotics, e.g., cefuroxime 125 mg/l in the dialysate for 48 h.
23. PD solutions
PH 5.8
Dextrose 1.5-4.25
Na 130
K 0
Cl 100
Buffer Lactate : 35-40Meq/l
HCO3 : 25 or 34Meq/l
Mg 1.5
Ca 3.0
24. Practical Considerations
Dialysis fill volumes of 10–20 ml/kg (300–600 ml/m2) should be used initially,
depending on the body size and cycle in and out, until the dialysate becomes clear.
PD with 1-h (10-30-20) should be used during the first 24 h.
Shorter cycles can be considered initially if hyperkalemia needs urgent treatment.
25. To be adjusted with increasing dwell times and cycle fill volume (if no leakage
problems) until desired fill volume (800–1,200 ml/m2) achieved
Adequate ultrafiltration and biochemical control to be achieved
26. Commence with the lowest concentration of glucose solution possible (1.36%),
with stepwise increments.
Care is needed if 3.86% glucose solution is required as
(1) rapid ultrafiltration can occur (especially in infants)
(2) hyperglycemia may develop (especially in septic and multi-organ failure patients)
leading to hyperosmolarity and loss of effective ultrafiltration
27. Heparin (500 units/l) should be added to the dialysis fluid to prevent fibrin
deposition and to improve peritoneal solute permeability
HCO3 :to be used in :
Lactic acidosis
Asepsis required
Part A : 60 ml Na HCO3 plus 440 ml 5% Dx
Part B : 500 ml NS
Mix Part 1 part of A and 2 parts of B
Contains 40 meq/l of HCO3
28. Use Y transfer sets : Prevents Peritonitis
Fluid Overload : 1. rapid cycles 2. increase glucose Conc (Inc UF)
Increase Solute Removal : Increase Dwell time
Target : Not more than 5-10% of wt loss
29. Additives in PD
Heparin 500U /L
K Hypokalemia
2-4 meq/l
Insulin 3-4U/L for 1.5 % Dx
5-6U/L for 2.5% Dx
7-10U/l for 4.25% Dx
30. Most slutions use glucose : Hyperinsulinemia , Hyperlipidemia , Peritoneal damage
Long term PD : Dx Solutions can cause cellular and morphological changes in PM –
angioneogenesis or Submeothelial fibrosis
Alternatively icodextrin can be used : absorbed in lymphatic channels at slow rate and
allows sustained UF over a longer dwell , Prolonged UF profile (Baxter)
Equivalent to 3.86% Dx , metabolised to amylase .
Biocomatible as iso osmolar , lacks Glucose
31. Osmotic agents
Icodextrin Prolonged UF profile but slow , less
effects
Glucose Rapid UF
More damage to PM
Amino acids Less acidity , more biocompatible , no
glucose . Also lits protein loss
32. Methods to increase dialysis adequacy
Continuous equilibrated PD : Larger fill volume – 40-45ml/kg , long dwell times 2-6
hours
Tidal PD : maintain atleast 30 % of fill volume (15ml/kg) throughout the dialysis
session . Increases solute clearance
Automated PD : One time connection , less infection , warming , keeps record
33. Maintanenace PD : types
Types Advantages Disadvantages Patient
selection
Issues
NIPD : Short
Nocturnal Cycle
with daytime
dwell
Preservation of
membrane
No day time
glucose
Decreased
Middle
molecule
clearance
High Urine
output
Anuria
CCPD : Short
Nocturnal
Cycles with day
time dwells
Inc UF and
solute
clearance
May require
daytime
exchange
Low Urine
output
High glucose
absorption
CAPD : Daytime
and night time
cycles
Complete
equilibration
Risk of
peritonitis ,
high glucose
absorption
Cost effective Recurrent
peritonitis
34. Three types of UF failures
Type 1 : Rapid solute transport : shorten dwell time , more frequent excahnges
Type 2 : Impaired Solute Transport : increases Dwell time
Type 3 : decreased lymphatic absorption : avoid large volume of dialysate
35. Complications and limitations
Leakage : use tenckhoff catheter
Hypothermia : warm PD solutions
Malposition , kinking , omental wrapping , fibrin clot : Heparin , urokinase
Sick infant : vasoconstriction of mesenteric vessels , poor UF
Inadequate solute removal
Peritonitis : Cloudy effluent , pain and fever
An effluent count of >100 leuco/ml (after 2 hours of dwell) with 50% neutrophils
Stiff catheter 48-72 hours affair !!
37. Equipment
Water system: An extensive purification system is absolutely critical for hemodialysis.
Dialysis patients are exposed to vast quantities of water, which is mixed with dialysate
concentrate to form the dialysate, even trace mineral contaminants or bacterial
endotoxins can filter into the patient's blood.
Filtered and temperature-adjusted and its pH is corrected by adding an acid or base.
Softened. Next the water is run through a tank containing activated charcoal to adsorb
organic contaminants.
Primary purification is then done by forcing water through a membrane with very tiny
pores, a so-called reverse osmosis membrane
38. Dialyzer
The dialyzer is the piece of equipment that actually filters the blood.
Almost all dialyzers in use today are of the hollow-fiber variety.
A cylindrical bundle of hollow fibers, whose walls are composed of semi-permeable
membrane, is anchored at each end into potting compound (glue).
blood compartment & dialysate compartment
39. Membrane and flux
Dialyzer membranes come with different pore sizes.
Smaller pore size are called "low-flux" and those with larger pore sizes are called "high-flux."
Some larger molecules, such as beta-2-microglobulin, are not removed at all with low-flux dialyzers;
the trend has been to use high-flux dialyzers
cellulose or synthetic materials, using polymers such as polyarylethersulfone, polyamide,
polyvinylpyrrolidone, polycarbonate, and polyacrylonitrile
Synthetic membranes can be made in either low- or high-flux configuration, but most are high-flux
Less proinflammatory cytokines
40. Dialyzer size and efficiency
K0A - the product of permeability coefficient and area
Larger membrane area (A) will usually remove more solutes than a smaller dialyzer,
especially at high blood flow rates
However slow blood flow in children will take lot of time to fill larger membrane
area dialyzer
Surface area of dialyzer should be equal to surface area of the child
41. Hemodialysis utilizes counter current flow, the dialysate is flowing in the opposite
direction to blood flow in the extracorporeal circuit.
Counter-current flow maintains the concentration gradient across the membrane at
a maximum and increases the efficiency of the dialysis.
Fluid removal (ultrafiltration) is achieved by altering the hydrostatic pressure of the
dialysate compartment, causing free water and some dissolved solutes to move
across the membrane along a created pressure gradient.
43. Anticoagulation
Heparin : loading dose of 20u/kg followed by infusion of 10u/kg/hr
ACT to be monitored , kept between 140-170 sec
LMWH : cleared via kidney , longer half life in AKI patients
Citrate : Chelates Calcium leads to regional anticoagulation , less systemic SE
Solutions:
1. Trisodium citrate (Na 440meq/l )
2. ACD A : (Na 220) – more commonly used to prevent Hyper Na
Rate is 1.5 X BFL(ml/min)
Cal. Chloride continuos infusion : citrate flow rate X 0.4
Maintain circuit ionized calcium between 0.2-0.4 & patient’s 1.1-1.3
44. Others
1. No anticoagulation – thrombocytopenia , coagulopathies , liver failure
2. Periodic saline slushes to prevent clotting
3. Danaproid : LMW heparinoid
4. Argatroban : direct thrombin inhibitor
5. Fondaparinux : anto factor Xa inhibitor
45. Tubing
Short as possible
Extracorporeal blood volume <10% blood volume otherwise priming
Arterial segment : ports for sampling , anticoagulation , predilution
Venous segment : port for post dilution
Monitors for pressure monitoring
Air trapping and removal
Pumps
Available in 3 sizes : neonatal 25 ml , Pediatric 75 ml , adult 127 ml
46. Hemodialysis
Highly effective in acute settings
Can accomplish Isolted UF also
Vascular Acess
1. Permanent : Arteriovenous Fistula or Arteriovenous graft
2. Acute : IJV or femoral vein
3. Subclavian to be avoided : risk of venous stenosis
47. Neonate 7F
3-6 kg 7F DL
6-15 Kg 8F DL
15-30 kg 9F DL
>30 Kg 10-12.5 F DL
51. The first session should not exceed 2–3 h, but the standard time is usually 4 h.
Longer sessions are advisable to avoid too-rapid ultrafiltration and disequilibrium
syndrome
52. Complications
Thrombosis , stenosis and infection : Cathetor related
Hypotension : Smaller BV in children : Slower UF rate , Saline / Albumin infusion
Hypothermia
Dialysis Disequilibrium syndrome : Acute cerebral oedema
Can be prevented by decreasing dialysis time , reducing blood flow rates
Patients where UREA is high : administer mannitol at start of HD
53. Target Urea reduction around 30-40% to prevent acute shift of osmoles
After 3-4 HD , Full HD prescription to be started
Ist Cycle 30% Urea
clearance
KT/V – 0.7 Low Surface are
& shorter time
dialysis
2nd cycle 70% 1.0
Later on 100% 1.2
54. Drug removal
> 25% of administered drug removal is considered significant
Leads theraupetic compromise
Extra dose can be given
55. CRRT
IHD not well tolerated in hemodyanamically unstable patients .
CRRT allows slow rate of fluid removal and solute exchange
Pros :
1. Less HD instability
2. Better tolerance to UF
3. Removal of Immunomodulatory substances as in sepsis
4. Less effect on ICT
Cons
1. Expensive
2. Requires expertise
57. CVVH
CAVH can have complications : Hemorrhage , Embolisation , Infection
So CVVH is preffered CRRT
Dialysate is not required in hemofiltration
BFR : 0-10 kg – 50ml/min , 11-20 kg – 80-100 ml /min , 21-50 kg – 150ml/min
4-5ml/kg/min
Only Convective clearance across membrane
58. Initial net UF rate to be 1-3% of patients Blood volume /hour
Replacement fluid rates to be determined by desired net fluid loss
Actual fluid removal rate – desired net hourly fluid removal + IV /oral intake – all
outputs
60. Site of replacement of fluid
Predilution : prior to hemofilter .
1. Useful if large volume of ultrafiltrate to be removed , increased hydrostatic
pressure
2. Prevents hemoconcentration
3. Improves life of the filter
Post dilution : Post filter , more solute clearance , less life of the filter
62. CVVHD
Dialysate runs through membrane
Diffusion is primary method of solute clearance
Total amt of fluid removed less than the CVVH
Clearance is directly proptionate to dialysate flow rate (2l/m2/hr)
BFR – 4-5 ml/kg/min
No replacement fluid in this modality
64. CVVHDF
CVVH is not adequate for solute clearance
Dialysate used for diffusive solute clearance
Diffusion plus convection clearance
BFR : 4-5ml/kg/min
Dialysate Flow rate : 2L /m2/hr
65. Requires the use of a blood, effluent, dialysate and replacement pumps.
Both dialysate and replacement solutions are used.
Plasma water and solutes are removed by diffusion, convection and ultrafiltration.
66.
67. SLEDD : Slow low efficiency diffusion HD
Uses HD machine to offer CRRT
BFR : 100-200ml/min
Dialysate flow rates : 100-300ml/min
Pros : avoids expense of CRRT , less HD instability , avoids disequilibrium , less need
of anticoagulation
Cons : poorer clearance of small and middle molecules as compared to CRRT
69. SCUF
Mainly to manage fluid overload without diffusive process
Better tolerated Hemodyanamcally
No dialysate
No replacement fluid
Used where fluid removal is priority !!
71. Prescription
Case 12 yr old boy with snake envenomation . Received 20 vials of ASV and
Clotting time has normalized . Puffy & edematous . UO is 50 ml in 36 hrs
BP – 100/70 mm hg , wt at admission is 30 kg Ht : 140cm .. BSA 1m2
Urea 170 , creat : 3.1 , Na : 128 , K 6.5
Modality of choice ???
72. Access ??
Dialyzer ??depends on surface area : ist hemodialysis – low surface area , shorter
time (2hrs ) !! Synthetic dialyser !!
15 kg F3
15-30kg F4
30-45 kg F5
45-60kg F6
>60Kg F8
73. Tubing : calculate total blood volume , Size depends on age !!
Extracorporeal BV <10% … otherwise needs priming ??
Priming solution :saline , 5% albumin , PRC
Dialysate composition – Bicarbonate buffered , glucose conc at physiological value
BFR : 5-7ml/kg/min
74. Dialysate Flow : 300-500ml/min or 2X BFR
UF : 10ml/kg/hr
Anticoagulation
Duration of dialysis
75. Prescription looks like !!
1st dialysis Full dose Dialysis
Access CVC CVC
Tubings 78ml 78ml
Dialyser Avoid high efficiency High flux high efficient
Dialysate High Na Conc 2-3 meq
higher than plasma
Standard dialysate
BFR 5-7 5-7 ml.kg/min
UF rate 10ml/kg/hr 10ml/kg/hr
Anticoagulation Heparin Heparin
Time 2 hrs 4hrs