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Principles of hemodialysis final 2017

Principles of hemodialysis final 2017

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Principles of hemodialysis final 2017

  1. 1. Dr. Osama El-Shahat Consultant Nephrologist Head of Nephrology Department New Mansoura General Hospital (international) ISN Educational Ambassador
  2. 2.  Basics of hemodialysis: ◦ Definition. ◦ Technique of hemodialysis: ◦ Main principles:  Diffusion.  Osmosis.  Filtration.  Convection. ◦ Varieties of hemodialysis.
  3. 3.  When a semi permeable membrane is placed between different solutions the solutes move across this membrane until they reach equilibrium  This is the theory by which dialysis is based on
  4. 4. blood membrane dialysate
  5. 5. directiondialysatebloodsolute To DxzerohighUREA To DxzerohighOTHER TOXINS NO135-140135-140Sodium To Dx1.4-3.0Above 5Potassium To Dx0.5-1.0Above 1Magnesium +/-180 (10)+/-140 (8)glucose NO100-119100-119chloride +/-5-6 mg/dl 2.5-3 mEq/L 4.5-5 mg/dl 2-2.5mEq/L Ionized Calcium
  6. 6.  Dialysate delivered at a rate of 500ml/min ◦ 120 liters of dialysate / 4-hour session!!  Concentrated solutions mixed with water  Usually 1:34 or 1:40  Conductivity is a measurement of electric conductivity of Na to check if dilution is correct  With proper dilution conductivity = 13-15  Serious hyponatremia or hypernatremia occurs if dilution is incorrect
  7. 7.  H+ neutralized by Na HCO3 in the body  Acetate ◦ Transformed in LIVER to HCO3 (10-15 min) ◦ BUT is a potent vasodilator  Hypotension especially with liver disease  Acetate intolerance in high flux dialyzers  Bicarbonate ◦ Immediately neutralizes H+ ◦ BUT precipitates Calcium salts (CaCO3)  Should be delivered separately as NaHCO3  Short life span of machine  Needs a strong post dialysis acid rinse (citric acid)
  8. 8.  Attempts are made to increase the surface area of contact between dialysate and dialyzer ◦ The Hollow fiber ◦ The parallel plate dialyzer
  9. 9.  Types ◦ Surface area. ◦ Low flux vs high flux. ◦ Biocompatibility. ◦ Technique of manufacture including hemo- adsorption.
  10. 10.  Cellulose membrane (Cuprophan) ◦ Is the first membrane to be used ◦ Contains free hydroxyl radicals ◦ They are bio-incompatible (BIC)  They are able to activate complement a inflammatory reaction a chronic inflammation a protein catabolism + anorexia + malnutrition a Cardiovascular accidents  Cause dialysis related Amyloidosis  Increased incidence of infection  Rapid loss of residual kidney function ◦ Cuprophan is BIC BUT this effect can be abolished after 2nd use!!!
  11. 11.  Substituted Cellulose ◦ Chemically bonding the free hydroxyl group  Cellulose di acetate  Cellulose Triacetate ◦ Addition of a synthetic material to cellulose  Hemophane (semi synthetic)  Synthetic modified cellulose (SMC)  Synthetic material ◦ Contains no cellulose  Polysolphone  PMMA  PAN
  12. 12.  There is no definite techniques for biocompatibility measurement  There is no clear evidence for its superiority except in AKI
  13. 13.  Ability of the dialyzer to clear urea from blood  The more clearance the better the dialyzer  Clearance can be calculated in vivo= Qb x [BUN ART – BUN VEN] BUN ART  Clearance is closely related to the surface area of HF
  14. 14.  HF with a high urea clearance ◦ They contain pores bigger in number and size ◦ Must be with bicarbonate dialysis ◦ They perform more adequate dialysis ◦ Clearance of bigger molecules toxins e.g. (B2 microglobulin) ◦ expensive
  15. 15.  The number of ml/hour of water the dialyzer can remove for every 1 mm Hg rise in TMP  E.g. a HF with KUF of 1 can remove 100ml/hour with TMP of 100  For volumetric machines HF with KUF above 4 should be used to give accurate results
  16. 16.  The more the patient’s weight the larger surface area (and clearance) you need  Patients with increased weight gain (volume overload) need a dialyzer with high KUF  Much debate is present with use of biocompatible membrane EXCEPT in AKI  High Flux dialyzer gives a better adequacy but is expensive
  17. 17.  ESRD patients are frequently oliguric  If excess water is ingested a accumulation of water in body a edema, hypertension, pulmonary edema  To remove water a Ultrafiltration  Addition of hydrostatic force a squeezing out water from dialysate!!!  may be –ve (machine UF)  Or +ve (partial venous clamping)  The net force is reflected by the transmembrane pressure (TMP)
  18. 18. 500 ml/min 700 ml/min +ve pressure -ve pressure TMP
  19. 19.  Definition: extracorporeal removal of waste products from the blood of patient who has poorly functioning kidneys with replacement of some materials deficient in the patient.
  20. 20.  Difussion: The process by which particles, atoms or molecule move from area of higher concentration to lower concentration across semipermeable membrane. Factors affecting : Concentration gradient MW of solutes.
  21. 21. Problems with conventional diffusive hemodialysis  Excessive cardiovascular mortality  Insufficient removal of middle molecules  Insufficient removal of phosphate  High risk of intradialytic hypotension  Suboptimal dialysate quality  Chronic inflammation and protein-energy wasting
  22. 22.  Filtration: Is movement of fluid through a filter as a result of hydraulic pressure. In hemodialysis, ultrafiltration , is movement of water from blood under pressure gradient effect.
  23. 23.  Convection: Transfer of heat and solute by physical circulation or or movement of parts of gas or liquid.  Countercurrent circulation
  24. 24. Hemoperfusion therapy (DHP) is a method of treatment to eliminate causal substances of disease in the blood by adsorption that takes place by passing the blood directly through an adsorbent. DHP is characterized by a simple extracorporeal blood circuit and easy operation. Activated charcoal, and either polymyxin B or hexadecyl alkyl compound immobilized adsorbents, are clinically available at present. The DHP using activated charcoal is mainly applied in cases of intoxication with either toxic substances or a drug overdose. Hemodialysis or plasma exchange is also applied in these situations. .
  25. 25. Application of either DHP, hemodialysis or plasma exchange is done according to the characteristics of the toxins or drugs. DHP using PMX is applied in cases of septic shock, and its efficiency is suggested to be due to the removal of anandamide in addition to endotoxins in the blood. DHP using BM-01 is applied to a specific disease, dialysis related amyloidosis, for the purpose of elimination of β2- microglobulin.
  26. 26.  Varieties of hemodialysis techniques: ◦ Conventional hemodialysis. ◦ Online hemodiafilteration. ◦ SLEDD. ◦ CRRT. ◦ Hemo-adsorption.
  27. 27. Mode of therapy Principle method of solute clearance CVVH Convection CVVHD Diffusion CVVHDF Convection & Diffusion SCUF Ultrafiltration (fluids)
  28. 28. HDF is a blood purification therapy combining diffusive and convective solute transport using a high-flux membrane characterized by an ultrafiltration coefficient greater than 20 mL/h/mm Hg/m2 and a sieving coefficient (S) for β2- microglobulin of greater than 0.6. Convective transport is achieved by an effective convection volume of at least 20% of the total blood volume processed. Appropriate fluid balance is maintained by external infusion of a sterile, non-pyrogenic solution into the patient's blood.
  29. 29.  Kt/V is 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, so that one can be sure that the delivered dose is at least 1.2. In peritoneal dialysis the target is ≥ 1.7/week.
  30. 30. ©
  31. 31. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013  Accumulation Of Waste products ◦ Urea, creatinine, others ◦ Hyperkalemia (increased potassium) ◦ Acidosis  Water intoxication ◦ Volume overload, pulmonary edema  Endocrinal Manifestations ◦ Anemia ◦ Osteodystrophy ◦ Hypertension
  32. 32. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013  Main basics:
  33. 33. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013
  34. 34. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013  Osmosis: Movement of the solvent through semipermeable membrane from area of low solute content to area of high solute content and the difference between them is called osmotic pressure gradient. This pressure is affected by two powers, concentration of solutes on both sides and the hydraulic pressure which can increase or decrease the movement of the fluid.
  35. 35. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013
  36. 36. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013
  37. 37. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013 Post-dilution haemodiafiltration Ultrafiltration followed by infusion of replacement fluid Pre-dilution haemodiafiltration Infusion of replacement fluid followed by ultrafiltration Mid-dilution haemodiafiltration Infusion of replacement fluid at the mid-point of ultrafiltration (post-dilution followed by pre- dilution) Mixed-dilution haemodiafiltration Infusion of replacement fluid before and after ultrafiltration (pre-dilution followed by post- dilution)
  38. 38. © ESNT-CNE 2nd Course, Cairo Jan 2-5, 2013 IHD SLEDD CRRT Name Intermittent hemodialysis Slow low efficacy daily dialysis Continuous renal replacement therapy Mechanism &mol. removed HD mostly LMW Small & middle with HD/F Small &middle with CVV HDF Use Ambulatory CRF Critically ill CRF/ AKI Critically ill CRF/AKI Blood flow rate 300-500 ml/min 200-300 ml/mi 50-200 ml/min DFR 500-800 ml/min 1-2 L/h 2-3 L/h Efficiency high Moderate low HD stability Poor Good good Duration 3-4hx3t/w 6-12 h/d Continuous Anticoagulant Not needed According According DDS May occur N/A N/A Toxicology &drugs Risk of rebound Unclear Slower removal logistics Less complicated Higher cost, low Ph costly

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