DIALYSIS MACHINE

DIALYSIS MACHINE

OBJECTIVE OF THE STUDY Describe how dialysis is used to treat kidney failure.Types of dialysis. Give a detailed explanation of kidney dialysis in terms of diffusion and concentration gradients.Detail explanation about main parts of dialysis machine Describe what happens during kidney dialysis. List some of the drawback of kidney dialysis machine.Describe problems with HD and PD.

CAUSES OF RENAL FAILURE DiabetesUntreated high blood pressure Inflammation Heredity Chronic infection Obstruction Accidents

Treatment OptionsNo TreatmentMonitoring & PredialysisControl symptomsPreserve Residual Renal FunctionControl rising BP (Antihypertensive)Control Renal Bone Disease (Ca2+, Vit. D)Prevent/Treat Anaemia (Erythropoietin, Blood)DialysisRenal Transplantation

INTRODUCTION

Dialysis(fromGreekdialusis, meaningdissolution,dia, meaningthrough, andlysis, meaningloosening or splitting) is a process for removing waste and excess water from theblood, and is used primarily as anartificial replacementfor lostkidney functionin people with renal failure.

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Dialysis may be used for those with an acute disturbance in kidney function (acute kidney injury, previously acute renal failure), or progressive but chronically worsening kidney functiona state known aschronic kidney diseasestage 5 (previously chronic renal failure or end-stage renal disease).

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The latter form may develop over months or years, but in contrast to acute kidney injury is not usually reversible, and dialysis is regarded as a "holding measure" until a renal transplantcan be performed, or sometimes as the only supportive measure in those for whom a transplant would be inappropriate.

BACKGROUND HISTORY

Dr.Willem Kolff, a Dutch physician, constructed the first working dialyzer in 1943 during theNazi occupation of the Netherlands.Due to the scarcity of available resources, Kolff had to improvise and build the initial machine usingsausage casings,beverage cans, awashing machine, and various other items that were available at the time.

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Over the following two years, Kolff used his machine to treat 16 patients suffering fromacute kidney failure, but the results were unsuccessful. Then, in 1945, a 67-year-old comatose woman regained consciousness following 11 hours of hemodialysis with the dialyzer, and lived for another seven years before dying of an unrelated condition. She was the first-ever patient successfully treated with dialysis.

PRINCIPLE

Dialysis works on the principles of thediffusionof solutes andultrafiltrationof fluid across asemi-permeable membrane. Diffusion is a property of substances in water; substances in water tend to move from an area of high concentration to an area of low concentration.Blood flows by one side of a semi-permeable membrane, and a dialysate, or special dialysis fluid, flows by the opposite side.

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A semipermeable membrane is a thin layer of material that contains holes of various sizes, or pores. Smaller solutes and fluid pass through the membrane, but the membrane blocks the passage of larger substances (for example, red blood cells, large proteins). This replicates the filtering process that takes place in the kidneys, when the blood enters the kidneys and the larger substances are separated from the smaller ones in theglomerulus.

How does a Dialysis Machine work?

Path which blood takes:

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How the waste substances in the blood such as urea is removed from the blood?

They are removed from the blood in the dialyzer. In the dialyzer, the blood with waste products will flow past one side of a semi-permeable membrane. On the other side of this membrane, there is a special substance called dialysate, which pulls waste from blood. The waste such as urea will pass through the membrane.

What is inside a Dialyzer?Dialysate is a solution that pulls waste from blood.

Types Of Dialysis

Haemodialysis (HD)Peritoneal Dialysis (PD)They work on similar principles: Movement of solute or water across a semipermeable membrane (dialysis membrane)

Haemodialysis (HD)It involvesdiffusion of solutes across a semipermeable membrane. Hemodialysis utilizescounter current flow, where the dialysate is flowing in the opposite direction toblood flowin theextracorporeal circuit. Counter-current flow maintains the concentration gradient across the membrane at a maximum and increases the efficiency of the dialysis.

PERITONEAL DIALYSIS

In peritoneal dialysis, a sterile solution containing glucose (called dialysate) is run through a tube into theperitoneal cavity, theabdominal body cavity around theintestine, where the peritoneal membrane acts as a partially permeable membrane. The peritoneal membrane or peritoneum is a layer of tissue containing blood vessels that lines and surrounds the peritoneal, or abdominal, cavity and the internal abdominal organs (stomach, spleen, liver, and intestines).

CONT.Diffusion and osmosis drive waste products and excess fluid through the peritoneum into the dialysate until the dialysate approaches equilibrium with the body's fluids. Then the dialysate is drained, discarded, and replaced with fresh dialysate.

Mechanism used for purification

Dialysis machine filter unwanted minerals from blood by two means:By Diffusion By Ultrafiltration

Diffusion

InLatin, "diffundere" means "to spread out".Movement of solute across semipermeable membrane from region of high concentration to one of low concentration

The process of diffusion 1.

2. Blood cells are too big to pass through the dialysis membrane, but body wastes begin to diffuse (pass) into the dialysis solution.

3. Diffusion is complete. Body wastes have diffused through the membrane, and now there are equal amounts of waste in both the blood and thedialysis solution.

Ultrafiltration

Made possible by osmosisMovement of water across semipermeable membrane from low osmolality to high osmolalityOsmolality number of osmotically active particles in a unit (litre) of solvent

The process of ultrafiltration in PD1.

2. Blood cells are too big to pass through the semi-permeable membrane, but water in the blood is drawn into the dialysis fluid by the glucose.

3. Ultrafiltration is complete. Water has been drawn through the peritoneumby the glucose in the dialysis fluid. There is now extra water in the dialysis fluid which need to be changed.

Main Parts of a Kidney Dialysis Machine

Dialysis Membrane(sometimes referred to as simply a "dialyzer) :- Hemodialysisuses a cellulose-membrane tube immersed in fluid, whereasperitoneal dialysisuses the lining of the patient's abdominal cavity (peritoneum), as a dialysis membrane.

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Dialysate :- The dialysate (solution) has the same solute concentrations as those in ordinary plasma. Therefore if the patient's blood plasma containsexcessconcentrations of any solutes, these will move into the dialysate, and if the blood plasmalacks the ideal concentration of any solutes, these will move into the patient's blood. Conversely, the dialysate fluid does not contain any waste products such as urea - so these substances in the patient's blood move down the concentration gradient into the dialysate.

CONT.Anticoagulant:-Heparin is the usual anticoagulant that is added to the patient's blood as it enters the dialysis machine (in order to prevent the blood from clotting as it passes through the machine). Preventing the blood from clotting should, in turn, prevent any blood clots from blocking the filtration surface of the system. However, heparin is not added during the final hour of dialysis in order to enable the patient's blood clotting activity to return to normal before he/she leaves.

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Pumps:-Peristaltic pumps are commonly used for driving the various higher volume fluids in the machine: blood, dialysate, water, and saline. This type of pump is very convenient because it does not touch the fluids directly. Instead, a section of flexible tubing runs through the pump mechanism where it is compressed by rollers to push the fluid forward.

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Valves:-Several valves with electronic actuation are needed in the machine to allow variable mixing ratios. Various implementations are possible from simple opened/closed valves driven by solenoids to precision variable-position valves driven by stepper motors or other means.

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Sensors:-Dialysis machines require many different types of sensors to monitor various parameters. Blood pressure at various points in the extracorporeal circuit, dialysate pressure, temperature, O2saturation, motor speed, dialyzer membrane pressure gradient, and air are all monitored for proper values during dialysis

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Cleaning system:- Between patient sessions, any reused components must be sterilized. One approach is to heat water or saline to a high sterilizing temperature and then run it through the machine, both through the extracorporeal circuit and through the dialysate circuit.

RECENT DEVELOPEMENT

Researchers are developing wearable artificial kidney for dialysis patients which provides continuous dialysis 24 hours a day seven days a week, reported as upcoming paper in the Clinical Journals of the American Society of Nephrology (CJASN)The device essentially a miniaturized dialysis machine ,worn as a belt weights about 10 pounds and is powered by two nine volt batteries .Because patients dont need to be hooked up to a full size dialysis machine ,they are free to walk ,work or sleep while undergoing continuous ,gentle dialysis that more closely approximates normal kidney function.

ADVANTAGE OF THE WAK

Steady state metabolic and fluid control.Reduce the need for phosphate-binder, erythropoietin and hypertension medicine.Peritoneal base dialysis, hence bloodless.In-situ regeneration of spent dialysate in perpetuityFarewell to heavy dialysate bag storage , handling and disposal Easy to travel to walk and to live.Dont need to visit dialysis facilities weekly.Enhance lifestyle of the patient.

What happens during kidney dialysis?Blood enters machine from body (under pressure from radial artery).Pump (some diagrams show a roller pump) controls pressure and flow rate.Anticoagulant added to prevent clotting. Blood passes through dialysis membrane (equivalent tokidney nephrons).Bubble Trap removes any gas bubbles from blood.Blood is filtered then returned to the patient's radial vein

DRAWBACK OF DIALYSIS MACHINE

It is difficult to control the diffusion of substances in a dialysis machine as well as in a kidney so people on dialysis often have to carefully control their fluid intake and diet.Dialysis can involve a patient going to hospital up to three times a week and being connected up to the dialyser for about four hours at a time. This could have a large impact on a persons lifestyle.

PROBLEMS WITH HEAMODIALYSIS

Rapid changes in BPfainting, vomiting, cramps, chest pain, irritability, fatigue, temporary loss of visionFluid overload esp. in between sessionsFluid restrictions more stringent with HD than PDHyperkalaemia esp. in between sessions

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Loss of independenceProblems with access poor quality, blockage etc. Infection (vascular access catheters)Pain with needlesBleeding from the fistula during or after dialysisInfections during sessions; exit site infections; blood-borne viruses e.g. Hepatitis, HIV

PROBLEMS WITH PERITONEAL DIALYSIS

Responsibility:-Some kidney patients get tired of the responsibility of doing their peritoneal dialysis every day.Body image:-Some peritoneal dialysis patients find it difficult to accept a permanent PD catheter. They worry that the catheter may affect their sexual activity and their relationship with their partner.

CONT.Fluid overload:-Fluid overload occurs when there is too much fluid in the body.Dehydration:-Dehydration occurs when there is too little fluid in the body. It can be caused by excess fluid loss due to diarrhea or sweating.Discomfort:-Some PD patients find that having the dialysis fluid in their abdomen is uncomfortable.Poor drainage:-is poor drainage of the dialysis fluidamong new patients.The most common causes are: constipation and Catheter displacement.Leaks:-In some patients, the peritoneal dialysis fluid leaks out around the catheter exit site.

CONCLUSION

Dialysis involves diverting the blood through artificial kidney machine that cleans and returns it to the body. During this process the blood is purified by two principles (i.e. diffusion and ultrafiltration) through a semipermeable membrane. This semipermeable membrane can be cellulose membrane(in case of HD) or it can be peritoneal membrane(in case of PD).

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In relation with this process of diverting the blood through artificial kidney there is some limitations that have to be considered in order to perform safe purification process. Generally this machine gives hope for patients who have renal failure.

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