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Continuous renal
replacement
therapy
SAMIR EL ANSARY
Continuous Renal Replacement Therapy
(CRRT)
Is an extracorporeal blood purification therapy
intended to substitute for imp...
Requirements for CRRT
A central double-lumen veno-venous
hemodialysis catheter
An extracorporeal circuit and a
hemofilte...
Indications
• CRRT is better tolerated by
hemodynamically unstable patients
because fluid volume, electrolytes and pH
are ...
• Hemodynamically unstable patients with the
following diagnoses may be candidates for
CRRT:
 fluid overload
acute renal...
Principals of CRRT
• Vascular access.
• Semi-permeable membrane.
• Transport mechanism.
• Dialysate and replacement fluid.
I- Vascular access
• Internal jugular.
• Subclavian.
• Femoral.
Access Location
• Internal Jugular Vein
–Primary site of
• Femoral Vein
–Patient immobilized, the femoral vein
is optimal ...
Choosing the right catheter
• The length of the catheter chosen will
depend upon the site used
– Size of the catheter is i...
II- Semi-permeable membrane
• The basis of all blood purification
therapies.
• Water and some solutes pass through
the mem...
II- Semi-permeable membrane
• 2 types: cellulose and synthetic.
• Synthetic membranes allow clearance
of larger molecules ...
Molecular size: Both molecule size and pore size determine the solute flow
through the semi-permeable membrane.
A membrane that has large pore size.
Molecular Weights
(Dalton)
100000
50000
10000
5000
1000
500
100
50
Albumin (55000 – 60000)
Beta 2 Microglobulin (11800)
In...
III- Transport mechanisms
a) Ultrafiltration
• The passage of water through a
membrane under a pressure gradient.
• Drivin...
Here is a visual example of how ultrafiltration works. On the blood side of the
hemofilter you have a positive pressure gr...
b) Convection
• Movement of solutes through a membrane by
the force of water “solvent drag”.
• The water pulls the molecul...
To better understand this phenomenon, think of a quiet stream as compared to a raging
river. The stream could never shift ...
This visual will provide you with a better understanding of how convection works.
From the picture you can see a faucet wh...
c) Adsorption
Adsorption is the removal of solutes from the
blood because they cling to the membrane.
Think of an air filt...
some molecules will attach to the membrane surface. While other molecules
may permeate the membrane, but become stuck with...
d) Diffusion
Diffusion is the movement of a solute across a membrane
via a concentration gradient. For diffusion to occur,...
The patients blood contains a high concentration of unwanted solutes that can be
effectively removed by diffusion. Diffusi...
IV- Dialysate and replacement
fluid
Dialysate is any fluid used on the
opposite side of the filter from the
blood during b...
Replacement fluid
• Used to increase the amount of convective
solute removal in CRRT.
• Replacement fluids do not replace
...
The decision to infuse replacement fluids
before or after the filter is made by the
physician.
Replacement fluids administ...
The downside of pre-filter replacement
fluids is that they invalidate post-filter lab
draws; the lab results will
show the...
Modalities of
CRRT
Slow Continuous Ultrafiltration
(SCUF)
• The primary indication for SCUF is fluid
overload without uremia or significant
e...
Slow Continuous Ultrafiltration
(SCUF)
• The amount of fluid in the effluent bag is the
same as the amount removed from th...
SCUF
• Blood flow: 80 – 200 ml/min
• Duration
• Ultrafiltration: 20-100 ml/hr (or total
volume)
• Anticoagulation
• NO dia...
Continuous Veno-venous Hemofiltration
(CVVH)
• An extremely effective method of solute removal
and is indicated for uremia...
Continuous Veno-venous Hemofiltration
(CVVH)
• Solutes can be removed in large quantities while
easily maintaining a net z...
CVVH
• Blood flow:80 – 200 ml/min
• Duration
• Ultrafiltration: 20-100 ml/hr
• RF: 1000 – 2000 ml/hr , pre or post filter
...
Continuous Veno-venous Hemodialysis
(CVVHD)
• Effective for removal of small to medium sized
molecules.
• Solute removal o...
CVVHD
• Blood flow:80 – 200 ml/min
• Duration
• Ultrafiltration: 20 -100 ml/hr
• Anticoagulation
• Dialysate: 600 – 1800 m...
Continuous Veno-venous Hemodiafiltration
(CVVHDF)
• The most flexible of all the therapies, and
combines the benefits of d...
Continuous Veno-venous Hemodiafiltration
(CVVHDF)
• Amount of fluid in the effluent bag equals
the fluid removed from the ...
CVVHDF
• Blood flow: 80 – 200 ml/min
• Duration
• Ultrafiltration: 20-100 ml/hr
• Anticoagulation
• Dialysate: 600 – 1800 ...
Anticoagulation & CRRT
• Low-dose pre-filter unfractionated
Heparin: any dose less than 5 units/kg/hour.
• Medium-dose pre...
Anticoagulation & CRRT
• Regional unfractionated Heparin: a pre-
filter dose of 1500 units/hour of Heparin,
with administr...
No Anticoagulation
• Platelet count < 50,000/mm3
• INR > 2.0
• aPTT > 60 seconds
• Actively bleeding or with an active ble...
Complications of CRRT
• Bleeding
• Hypothermia
• Electrolyte imbalance
• Acid-base imbalance
• Infection
• Dosing of medic...
Continuous Renal Replacement Therapy
CRRT
WHAT
Is CRRT
HOW
To use CRRT
HOWTo use CRRT
• Dose of CRRT.
• Anticoagulation and
CRRT.
• Nutrition and CRRT.
• Drug doses in CRRT.
When to start CRRT
Better outcomes are
associated with early CRRT
initiation
Renal recovery may be better after CRRT than IHD for ARF.
Mortality was not affected significantly by RRT mode.
IHD Vs CRRT
DOSE of CRRT
• The concept of RRT dose is As is the
case for antibiotics, vasopressors, anti-
inflammatory drugs, mechanical
ventilatio...
Efficiency (K)
• The volume of blood cleared of a given solute
over a given time.
(mL/min, mL/hr, L/hr, L/24 hrs, etc.)
• ...
Intensity (Kt)
• Defined as: The product of K X time.
• (Kt: mL/min X 24 hrs, L/hr X 4 hrs, etc.)
• Kt is more useful than...
Efficacy (Kt/V)
• The effective outcome resulting from the
administration of a given treatment dose to a
given patient.
• ...
Limitations
• The marker solute cannot and does not
represent all of the solutes that accumulate in
renal failure.
• Its k...
Anticoagulation
and CRRT
Why ?
• Prevent clotting of the circuit.
• Preserve filter performance.
• Optimize circuit servival.
• Prevent loss of blo...
Ideal anticoagulant
• Should prevent filter clotting without
inducing hemorrhage.
• Should have a short half-life, and act...
Anticoagulation & CRRT
• Low-dose pre-filter unfractionated
Heparin: any dose less than 5
units/kg/hour.
• Medium-dose pre...
Anticoagulation & CRRT
• Regional unfractionated Heparin: a pre-
filter dose of 1500 units/hour of Heparin,
with administr...
Current Opinion
• 5000 – 20000 U of UFH added to the
priming solution.
• Continuous infusion of 3-5 u/kg/hr.
• 50 – 100 % ...
Regional anticoagulation
using Citrate
• Pre-filter citrate inhibits coagulation
by chelating Ca+
• As a result iCa decrea...
Metabolic effects of citrate
Argatroban
 Argatroban loading dose of 100 µ/kg
 Followed by maintenance infusion rate
( µ/kg/min)
 Maintenance infusio...
 Argatroban loading dose of 100 µ/kg
 Followed by maintenance infusion rate ( µ/kg/min)
 Maintenance infusion calculate...
What’s the point ?
• Anticoagulation during CRRT should be
individualized.
• The first goal should be the safety of the
pa...
Nutrition
and CRRT
Nutrition Implications of ARF
• ARF causes anorexia, nausea, vomiting,
bleeding
• ARF causes rapid nitrogen loss and lean ...
Nutrient Requirements in ARF
• Calories: 25-45 kcals/kg dry weight or
REE
• Protein: about 10-16 g amino acids lost
per da...
Nutrient Requirements in ARF
• CHO: ~60% total calories; limit to 5
mg/kg/min; peripheral insulin resistance may
limit CHO...
Vitamins in ARF
• Vitamin A: elevated vitamin A levels are known
to occur with RF
• Vitamin B – prevent B6 deficiency by g...
Minerals in ARF
• ↑ potassium, magnesium, and phos occur often
due to ↓ renal clearance and ↑ protein
catabolism
• ↓ potas...
Fluid in ARF
• Depends on residual renal function, fluid
and sodium status, other losses
• Usually 500 mL/day + urine outp...
Drug dosing in
CRRT
• only the drug in the central
compartment ( plasma ) is available for
extracorporeal removal
• drugs with a large Vd have...
Factors determining
extracorporeal drug removal
a) Pharmacological
• Molecular weight.
• Volume of distribution.
• Plasma ...
Factors determining
extracorporeal drug removal
b) Technical
• Membrane.
• Diffusion.
• Convection.
• Adsorption to membra...
contious Renal replacement therapy
contious Renal replacement therapy
contious Renal replacement therapy
contious Renal replacement therapy
contious Renal replacement therapy
contious Renal replacement therapy
contious Renal replacement therapy
contious Renal replacement therapy
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contious Renal replacement therapy

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prof Dr Samir Alansary
ain shams uni.

Published in: Health & Medicine

contious Renal replacement therapy

  1. 1. Continuous renal replacement therapy SAMIR EL ANSARY
  2. 2. Continuous Renal Replacement Therapy (CRRT) Is an extracorporeal blood purification therapy intended to substitute for impaired renal function over an extended period of time and applied for or aimed at being applied for 24 hours a day.
  3. 3. Requirements for CRRT A central double-lumen veno-venous hemodialysis catheter An extracorporeal circuit and a hemofilter A blood pump and a effluent pump. With specific CRRT therapies dialysate and/or replacement pumps are required.
  4. 4. Indications • CRRT is better tolerated by hemodynamically unstable patients because fluid volume, electrolytes and pH are adjusted slowly and steadily over a 24 hour period rather than a 3 – 4 hour period.
  5. 5. • Hemodynamically unstable patients with the following diagnoses may be candidates for CRRT:  fluid overload acute renal failure chronic renal failure life-threatening electrolyte imbalance major burns with compromised renal function drug overdose
  6. 6. Principals of CRRT • Vascular access. • Semi-permeable membrane. • Transport mechanism. • Dialysate and replacement fluid.
  7. 7. I- Vascular access • Internal jugular. • Subclavian. • Femoral.
  8. 8. Access Location • Internal Jugular Vein –Primary site of • Femoral Vein –Patient immobilized, the femoral vein is optimal and constitutes the easiest site for insertion. • Subclavin Vein –The least preferred site
  9. 9. Choosing the right catheter • The length of the catheter chosen will depend upon the site used – Size of the catheter is important in the pediatric population. • The following are suggested guidelines for the different sites: – RIJ= 15 cm – LIJ= 20 cm – Femoral= 25 cm
  10. 10. II- Semi-permeable membrane • The basis of all blood purification therapies. • Water and some solutes pass through the membrane, while cellular components and other solutes remain behind.
  11. 11. II- Semi-permeable membrane • 2 types: cellulose and synthetic. • Synthetic membranes allow clearance of larger molecules and are the primary type used in CRRT. • Filters are changed when they become contaminated, clogged or clotted.
  12. 12. Molecular size: Both molecule size and pore size determine the solute flow through the semi-permeable membrane.
  13. 13. A membrane that has large pore size.
  14. 14. Molecular Weights (Dalton) 100000 50000 10000 5000 1000 500 100 50 Albumin (55000 – 60000) Beta 2 Microglobulin (11800) Inulin (5200) Vit B12 (1355) Aluminium/Desforoxamine complex (700) Glucose (180) Uric Acid (168) Creatinine (113) Phosphate (80) Urea (60) Potassium (35) Phosphorus (31) Sodium (23)
  15. 15. III- Transport mechanisms a) Ultrafiltration • The passage of water through a membrane under a pressure gradient. • Driving pressure can be +ve (push fluid through the filter), or –ve (pull fluid to other side of filter). • Pressure gradient is created by effluent pump.
  16. 16. Here is a visual example of how ultrafiltration works. On the blood side of the hemofilter you have a positive pressure gradient. on the fluid side of the hemofilter you have a negative pressure gradient. The effluent pump applies pressure on the membrane causing the fluid to move from the positive pressure gradient to the lower pressure gradient.
  17. 17. b) Convection • Movement of solutes through a membrane by the force of water “solvent drag”. • The water pulls the molecules along with it as it flows through the membrane. • can remove middle and large molecules, as well as large fluid volumes. • maximized by using replacement fluids.
  18. 18. To better understand this phenomenon, think of a quiet stream as compared to a raging river. The stream could never shift a boulder, but the powerful raging river could easily drag a boulder downstream. So it is with convection; the faster the flow through the membrane, the larger the molecules that can be transported
  19. 19. This visual will provide you with a better understanding of how convection works. From the picture you can see a faucet which represents replacement solution. The top faucet is an example of pre-filter dilution, which means that the replacement solution mixes with the blood as it enters the filter. The bottom faucet is an example of post-filter dilution and is delivered as the blood is returning to the patient. Now the effluent pump is removing ultrafiltration (just like SCUF), or patient plasma water and replacement solution.
  20. 20. c) Adsorption Adsorption is the removal of solutes from the blood because they cling to the membrane. Think of an air filter. As the air passes through it, impurities cling to the filter itself. Eventually the impurities will clog the filter and it will need to be changed. The same is true in blood purification. High levels of adsorption can cause filters to clog and become ineffective
  21. 21. some molecules will attach to the membrane surface. While other molecules may permeate the membrane, but become stuck within the fibers. It is believed that inflammatory mediators are effectively removed via adsorption.
  22. 22. d) Diffusion Diffusion is the movement of a solute across a membrane via a concentration gradient. For diffusion to occur, another fluid must flow on the opposite side of the membrane. In blood purification this fluid is called dialysate. When solutes diffuse across a membrane they always shift from an area of higher concentration to an area of lower concentration until the solute concentration on both sides of the membrane is equal.
  23. 23. The patients blood contains a high concentration of unwanted solutes that can be effectively removed by diffusion. Diffusions key mechanism is to move a solute from a higher concentration gradient to a lower concentration gradient. For example, let us assume the blood in the filter has a high concentration of potassium molecules and on the fluid/dialysate compartment has a low concentration of potassium. The potassium gradually diffuses through the membrane from the area of a higher potassium concentration to the area of a lower potassium concentration until it is evenly distributed.
  24. 24. IV- Dialysate and replacement fluid Dialysate is any fluid used on the opposite side of the filter from the blood during blood purification. As with traditional hemodialysis therapy, the dialysate is run on the opposite side of the filter, countercurrent to the flow of the patient’s blood. The countercurrent flow allows a greater diffusion gradient across the entire membrane, increasing the effectiveness of solute removal. Typical dialysate flow rates are between 600 – 1800 mL/hour.
  25. 25. Replacement fluid • Used to increase the amount of convective solute removal in CRRT. • Replacement fluids do not replace anything. • Fluid removal rates are calculated independently of replacement fluid rates. • The most common replacement fluid is 0.9% Normal Saline. • Can be pre or post filter.
  26. 26. The decision to infuse replacement fluids before or after the filter is made by the physician. Replacement fluids administered pre- filter reduce filter clotting and can be administered at faster rates (driving higher convection) than fluids administered post- filter.
  27. 27. The downside of pre-filter replacement fluids is that they invalidate post-filter lab draws; the lab results will show the composition of the replacement fluid rather than that of the effluent.
  28. 28. Modalities of CRRT
  29. 29. Slow Continuous Ultrafiltration (SCUF) • The primary indication for SCUF is fluid overload without uremia or significant electrolyte imbalance. • The main mechanism of water transport is ultrafiltration. • Other solutes are carried off in small amounts, but usually not enough to be clinically significant.
  30. 30. Slow Continuous Ultrafiltration (SCUF) • The amount of fluid in the effluent bag is the same as the amount removed from the patient. • Fluid removal rates are typically closer to 100 mL/hour. • No dialysate or replacement fluid is used.
  31. 31. SCUF • Blood flow: 80 – 200 ml/min • Duration • Ultrafiltration: 20-100 ml/hr (or total volume) • Anticoagulation • NO dialysate, NO replacement fluid
  32. 32. Continuous Veno-venous Hemofiltration (CVVH) • An extremely effective method of solute removal and is indicated for uremia or severe pH or electrolyte imbalance with or without fluid overload. • Particularly good at removal of large molecules, because CVVH removes solutes via convection, • Many theories exist regarding the removal of pro-inflammatory mediators by CVVH.
  33. 33. Continuous Veno-venous Hemofiltration (CVVH) • Solutes can be removed in large quantities while easily maintaining a net zero or even a positive fluid balance in the patient. • The amount of fluid in the effluent bag is equal to the amount of fluid removed from the patient plus the volume of replacement fluids administered. •No dialysate is used.
  34. 34. CVVH • Blood flow:80 – 200 ml/min • Duration • Ultrafiltration: 20-100 ml/hr • RF: 1000 – 2000 ml/hr , pre or post filter (up to 3 lit/hr). • Anticoagulation • NO dialysate
  35. 35. Continuous Veno-venous Hemodialysis (CVVHD) • Effective for removal of small to medium sized molecules. • Solute removal occurs primarily due to diffusion. • No replacement fluid is used. • Dialysate is run on the opposite side of the filter. • Fluid in the effluent bag is equal to the amount of fluid removed from the patient plus the dialysate.
  36. 36. CVVHD • Blood flow:80 – 200 ml/min • Duration • Ultrafiltration: 20 -100 ml/hr • Anticoagulation • Dialysate: 600 – 1800 ml/hr (up to 3 lit/hr). • NO replacement fluid
  37. 37. Continuous Veno-venous Hemodiafiltration (CVVHDF) • The most flexible of all the therapies, and combines the benefits of diffusion and convection for solute removal. • The use of replacement fluid allows adequate solute removal even with zero or positive net fluid balance for the patient.
  38. 38. Continuous Veno-venous Hemodiafiltration (CVVHDF) • Amount of fluid in the effluent bag equals the fluid removed from the patient plus the dialysate and the replacement fluid. • Dialysate on the opposite side of the filter and replacement fluid either before or after the filter.
  39. 39. CVVHDF • Blood flow: 80 – 200 ml/min • Duration • Ultrafiltration: 20-100 ml/hr • Anticoagulation • Dialysate: 600 – 1800 ml/hr (up to 3 lit/hr). • Replacement fluid: 1000-2000 ml/hr, pre or post filter (up to 3 lit/hr).
  40. 40. Anticoagulation & CRRT • Low-dose pre-filter unfractionated Heparin: any dose less than 5 units/kg/hour. • Medium-dose pre-filter unfractionated Heparin: a dose between 8-10 units/kg/hour. • Systemic unfractionated Heparin is administered intravenously and titrated to achieve an activated partial thromboplastin time (aPTT) ordered by the physician, for patients who have another indication for heparinization, such as. DVT
  41. 41. Anticoagulation & CRRT • Regional unfractionated Heparin: a pre- filter dose of 1500 units/hour of Heparin, with administration of Protamine post- filter at a dose of 10-12 mg/hour. • Low-molecular-weight Heparins • Prostacyclin: rarely used (expensive, hypotension) • Citrate: infused pre-filter, Ca must be replaced.
  42. 42. No Anticoagulation • Platelet count < 50,000/mm3 • INR > 2.0 • aPTT > 60 seconds • Actively bleeding or with an active bleeding episode in the last 24 hours • Severe hepatic dysfunction or recent liver transplantation • Within 24 hours post cardiopulmonary bypass or extra-corporeal membrane oxygenation (ECMO)
  43. 43. Complications of CRRT • Bleeding • Hypothermia • Electrolyte imbalance • Acid-base imbalance • Infection • Dosing of medications
  44. 44. Continuous Renal Replacement Therapy CRRT WHAT Is CRRT HOW To use CRRT HOWTo use CRRT
  45. 45. • Dose of CRRT. • Anticoagulation and CRRT. • Nutrition and CRRT. • Drug doses in CRRT.
  46. 46. When to start CRRT Better outcomes are associated with early CRRT initiation
  47. 47. Renal recovery may be better after CRRT than IHD for ARF. Mortality was not affected significantly by RRT mode. IHD Vs CRRT
  48. 48. DOSE of CRRT
  49. 49. • The concept of RRT dose is As is the case for antibiotics, vasopressors, anti- inflammatory drugs, mechanical ventilation, etc. • In chronic kidney disease, urea often has been used as a marker molecule. • The amount (dose) of delivered RRT can be described by various terms: efficiency, intensity, frequency, and clinical efficacy.
  50. 50. Efficiency (K) • The volume of blood cleared of a given solute over a given time. (mL/min, mL/hr, L/hr, L/24 hrs, etc.) • During RRT, K depends on solute molecular size and diffusivity, transport modality (convection or diffusion), and circuit operational characteristics such as blood flow rate, ultrafiltration rate, dialysate flow rate, and membrane and hemodialyzer type and size.
  51. 51. Intensity (Kt) • Defined as: The product of K X time. • (Kt: mL/min X 24 hrs, L/hr X 4 hrs, etc.) • Kt is more useful than K in comparing various RRTs. • Nevertheless, equal Kt products may lead to different results if K is large and t is small or if K is small and t is large.
  52. 52. Efficacy (Kt/V) • The effective outcome resulting from the administration of a given treatment dose to a given patient. • V: is the volume of distribution of the marker molecule in the body. • Kt/V is a dimensionless number(e.g., 3 L/hr X 24 hrs/45 L = 72 L/45 L = 1.6)
  53. 53. Limitations • The marker solute cannot and does not represent all of the solutes that accumulate in renal failure. • Its kinetics and volume of distribution are also different from other solutes. • Finally, its removal during RRT is not representative of the removal of other solutes. • This is true for both end-stage renal failure and acute renal failure.
  54. 54. Anticoagulation and CRRT
  55. 55. Why ? • Prevent clotting of the circuit. • Preserve filter performance. • Optimize circuit servival. • Prevent loss of blood due to circuit clotting.
  56. 56. Ideal anticoagulant • Should prevent filter clotting without inducing hemorrhage. • Should have a short half-life, and action limited to extracorporeal circuit. • Should be easily monitored. • Should have No systemic side effects. • Should have an antidote.
  57. 57. Anticoagulation & CRRT • Low-dose pre-filter unfractionated Heparin: any dose less than 5 units/kg/hour. • Medium-dose pre-filter unfractionated Heparin: a dose between 8-10 units/kg/hour. • Systemic unfractionated Heparin is administered intravenously and titrated to achieve an activated partial thromboplastin time (aPTT) ordered by the physician, for patients who have another indication for heparinization, such as. DVT
  58. 58. Anticoagulation & CRRT • Regional unfractionated Heparin: a pre- filter dose of 1500 units/hour of Heparin, with administration of Protamine post- filter at a dose of 10-12 mg/hour. • Low-molecular-weight Heparins • Prostacyclin: rarely used (expensive, hypotension) • Citrate: infused pre-filter, Ca must be replaced.
  59. 59. Current Opinion • 5000 – 20000 U of UFH added to the priming solution. • Continuous infusion of 3-5 u/kg/hr. • 50 – 100 % prolongation of aPTT. • Incidence of bleeding varied between 0 – 50 %
  60. 60. Regional anticoagulation using Citrate • Pre-filter citrate inhibits coagulation by chelating Ca+ • As a result iCa decreases. • An iCa concentration below 0.35 mmol/L is required to inhibit coagulation.
  61. 61. Metabolic effects of citrate
  62. 62. Argatroban  Argatroban loading dose of 100 µ/kg  Followed by maintenance infusion rate ( µ/kg/min)  Maintenance infusion calculated by: 2.15 – 0.06 X APACHE II score
  63. 63.  Argatroban loading dose of 100 µ/kg  Followed by maintenance infusion rate ( µ/kg/min)  Maintenance infusion calculated by: 2.15 – 0.06 X APACHE II score  In critically ill patients with HIT and necessity for CRRT , APACHE II can help to predict the required argatroban maintenance dose for anticoagulation.  This predictor identifies decreased argatroban dosing requirements.  Resulting in effective and safe CRRT. Argatroban
  64. 64. What’s the point ? • Anticoagulation during CRRT should be individualized. • The first goal should be the safety of the patient. • Attention should be paid to non- pharmacological means of prolonging filter life (blood flow, wide pore cath, pre-filter replacement fluid).
  65. 65. Nutrition and CRRT
  66. 66. Nutrition Implications of ARF • ARF causes anorexia, nausea, vomiting, bleeding • ARF causes rapid nitrogen loss and lean body mass loss (hypercatabolism) • ARF causes ↑ gluconeogenesis with insulin resistance • Dialysis causes loss of amino acids and protein • Uremia toxins cause impaired glucose utilization and protein synthesis
  67. 67. Nutrient Requirements in ARF • Calories: 25-45 kcals/kg dry weight or REE • Protein: about 10-16 g amino acids lost per day with CRRT –Acute HD: 1.2-1.4 g/kg; acute PD: 1.2- 1.5 g/kg; CRRT: 1.5-2.5 g/kg
  68. 68. Nutrient Requirements in ARF • CHO: ~60% total calories; limit to 5 mg/kg/min; peripheral insulin resistance may limit CHO – In CWHD(F) watch for CHO in dialysate or replacement fluids • Fat: 20-35% of total calories; lipid clearance may be impaired
  69. 69. Vitamins in ARF • Vitamin A: elevated vitamin A levels are known to occur with RF • Vitamin B – prevent B6 deficiency by giving 10 mg pyridoxine hydrochloride/day • Folate and B6: supplement when homocysteine levels are high • Vitamin C: < 200 mg/day to prevent ↑ oxalate • Activated vitamin D • Vitamin K: give Vitamin K especially to pts on antibiotics that suppress gut production of K
  70. 70. Minerals in ARF • ↑ potassium, magnesium, and phos occur often due to ↓ renal clearance and ↑ protein catabolism • ↓ potassium, mg and phos can occur with refeeding • CRRT pts can have ↓ K+, phos • Mg deficiency can cause K+ deficiency resistant to supplementation • Vitamin C, copper, chromium lost with CVVH
  71. 71. Fluid in ARF • Depends on residual renal function, fluid and sodium status, other losses • Usually 500 mL/day + urine output • Fluid replacement needs can be ↑ with CRRT
  72. 72. Drug dosing in CRRT
  73. 73. • only the drug in the central compartment ( plasma ) is available for extracorporeal removal • drugs with a large Vd have less access to the hemofilter or dialyzer • Extracorporeal treatmentdeeper compartments the rate of extracorporeal removal the rate of transfer between the peripheral and central compartment. Extracorporeal removal
  74. 74. Factors determining extracorporeal drug removal a) Pharmacological • Molecular weight. • Volume of distribution. • Plasma protein binding. • Drug charge (Gibbs-Donnan effect). Gibbs-Donan effect ( the behavior of charged particles near a semi-permeable membrane to sometimes fail to distribute evenly across the two sides of the membrane )
  75. 75. Factors determining extracorporeal drug removal b) Technical • Membrane. • Diffusion. • Convection. • Adsorption to membrane.

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