Spotlight on general principles of hemodialysis Mohammed Wahba Lect. Of int. medicine &nephrology MNDU

Agenda: Basics of hemodialysis: Definition. Main principles: Diffusion. Osmosis. Filtration. Convection. Technique of hemodialysis: Varieties of hemodialysis.

Basics of hemodialysis: 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.

Basics of hemodialysis: Main basics:

Basics of hemodialysis: 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. Temperature.

Basics of hemodialysis:

Basics of hemodialysis: 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.

Basics of hemodialysis:

Basics of hemodialysis: 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.

Basics of hemodialysis:

Basics of hemodialysis: Convection: Transfer of heat and solute by physical circulation or or movement of parts of gas or liquid.

Basics of hemodialysis: Countercurrent circulation

Technique of hemodialysis:

Technique of hemodialysis:

Technique of hemodialysis:

Technique of hemodialysis:

Technique of hemodialysis:

Technique of hemodialysis: 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.

Technique of hemodialysis: Filters: Surface area. Low flux vs high flux. Biocompatibility. Technique of manufacture including hemo- adsorption.

Technique of hemodialysis: Varieties of hemodialysis techniques: Conventional hemodialysis. Online hemodiafilteration. SLEDD. CRRT. Hemo-adsorption.

Technique of hemodialysis: 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 -Internal back-filtration with potential translocation of bacterial DNA -Chronic inflammation and protein-energy wasting

On-line HDF: 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.

Modes of controlled haemodiafiltration 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)

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 DDS May occur N/A Toxicology &drugs Risk of rebound Unclear Slower removal logistics Less complicated Higher cost, low Ph costly

Hemo-adsorption. 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. 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.

Hemo-adsorption.