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Extracorporeal techniques
- 1. Presented by: ArjanAryal 5th PharmD
- 2. Patients with ESRDor who have been intoxicated due to overdose of a drug may require supported treatment to remove accumulated drugs. Methods: Dialysis Hemofiltration Hemoperfusion. Objective: Rapidly remove undesirable drugs and metabolites without disturbing the fluid and electrolyte balance in the patient.
- 3. Artificial Process,acculmulation of drug removed by diffusion into dialysis fluid. Two Methods: Peritoneal Dialysis. Hemodialysis.
- 4. Helps toclean the blood and remove excess of water in the body – peritoneal Membrane in the abdomen. A catheter inserted in peritoneal cavity, dialysis fluid enters into the peritoneal cavity via tube -> filters blood and remove waste products from the body. Two Types CAPD(Continous Ambulatory Peritoneal Dialysis))) APD (Automated Peritoneal Dialysis)
- 5. Fluid flowsin and out of the body using gravity. Over time, waste and fluid build up in the blood which slowly float across into peritoneal membrane by diffusion and exchange remove dialysis fluid from the peritoneal cavity and replaces with new fluid. To be done everyday 1 Exchange takes 30 mins.
- 6. Solution isclear. Check the solution type and % is correct. Expiration date has not passed. Volume is correct. No leaks after gentle squeezing.
- 7. Machine doesthe exchange Done by Dialysis team or taught to use . FLUID AND DIALYSIS SOLUTION Important to achieve right balance of water in body. Determined in 3 ways. Weight BP Swelling Dialysis Solution Dianeal (1.5%, 2.5%, 4.25%) Neutroneal (1.1 %) Extraneal (7.5%) PRECAUTION Infection
- 8. Process thatuses artificial kidney to remove waste products through the process called diffusion. Artificial kidney contains a number of tubes with a semi permeable lining, suspended in a tank filled with dialysing fluid.
- 9. 1. •One line connectedto artery which is connected to one end of dialysis where blood is collected from patient for filtration. 2. •Waste Product from the blood passes into dialysing fluid by diffusion. 3. •Purified Blood is pumped back into the vein which is connected to other end of dialysis device.
- 10. Heparin isused to prevent blood clotting during dialysis. It is much more effective method for rapid removal of drug ( overdose , poisoning) and preferred method in ESRD. Dialysis may be required from every 2 days to 3 times a week, one dialysis period is of 2-4 hrs depending on patient’s size, weight and renal function. CHARACTERISTICS OF DIALYSING MACHINE Higher Blood flow rate. Permeable dialysis membrane. High Transmembrane pressure. Important notes.
- 11. •Insoluble or fatsoluble drugs are not solubilized.( eg glutethimide – a water insoluble drug.) Water Solubility •Tightly bound protein are not dialysed. (eg propranolol) Protein Binding •Mol Wt less than 500 are dialysed. ( eg Vancomycin is poorly dialysed ) Molecular Weight Drugs with large volume of distribution •Widely distributed drugs are dialysed slowly, drug concentrated in tissues are difficult to remove by dialysis.
- 12. In dialysisinvolving uremic patient receiving drug for therapy, drug is removed depending on the flow rate of the blood to the dialysis machine which is described by the term Dialysance. Defined by the equation : ClD = Q(Ca –CV) Ca where, Ca = Drug Concentration in arterial blood. CV =Drug Concentration in Venous blood. Q= Rate of Blood flow to kidney. ClD = Dialysance.
- 13. Removing thedrugs by passing the blood from the patient through an adsorbent material and back to the patient. Molecules which have greater affinity for the materials will be removed.
- 14. Useful inaccidental poisoning and drug overdose. Materials use: ◦ Activated Charcoal (both polar and non polar drugs) ◦ Amberlite resins (non polar organic molecules).
- 15. Affinity ofthe drug for the absorbent. Surface area of the absorbent. Absorptive capacity of the absorbent. Rate of blood flow through the absorbent. Equilibrium rate of the drug from the peripheral tissue into the blood.
- 16. An alternativeto hemodialysis and hemoperfusion. A process by which fluid, electrolytes, small molecular weight substances are removed from the blood using hollow artificial fibre. Loss of water and electrolytes takes place, that leads to production of ultrafiltrate. As a result equal volume of fluid is replaced.
- 17. Synthetic, highflux(permeability), hollow fibre membrane. Pore size 50000 da High Surface Area ( 0.6-1.2 m2). Notes • Flow rate of 20-35 ml/kg/hr is usually required. • No benefit shown with higher flow rate, more expensive. • Although higher flow rate may be used if rapid solute clearance is necessary.
- 18. Hemodialysis involves diffusionacross a semipermeable membrane Where as Hemofiltration is a convection process with loss of water Due to ultrafiltration accompanied by convicted loss of salts.
- 19. The clearanceof the drug depends on sieving coefficient and ultrafiltration rate. The sieving coefficient reflects the solute removal ability during hemofiltration. When S=1 solute passes freely through the membrane whereas is S=0 solute is retained in plasma. S is constant and independent of blood flow , so Cl=S * Ultrafiltration rate The Concentration of the drug in the ultrafiltrate is also equal to the unbound drug concentration in the plasma , so, amount of drug removed is given as : Amount removed = CP + ∞ * rate of ultrafiltration