Renal dialysis

RENAL DIALYSIS.
RRT
Renal Replacement Therapy.
Dialysis is the artificial process of eliminating waste (diffusion) and unwanted water (ultra filtration) from the blood.

Dialysis is a procedure that cleans and filters the blood. It rids the body of harmful wastes and extra salt and fluids. It also controls blood pressure and helps our body keep the proper balance of chemicals such as potassium, sodium, and chloride. �
Dialysis is a Greek word meaning "loosening from something else".

1. RENAL DIALYSIS OR renal replacement therapy(RRT) By: Dr. ZEEL NAIK

2. Dialysis is the artificial process of eliminating waste (diffusion) and unwanted water (ultra filtration) from the blood. Dialysis is a procedure that cleans and filters the blood. It rids the body of harmful wastes and extra salt and fluids. It also controls blood pressure and helps our body keep the proper balance of chemicals such as potassium, sodium, and chloride. Dialysis is a Greek word meaning "loosening from something else". INTRODUCTION

3. RRT is indicated in a patient with AKI when kidney function is so poor that life is at risk. RRT is urgently indicated in AKI to : Remove uraemic toxins where severe symptoms are apparent, for example, impaired consciousness , seizures , pericarditis and rapidly developing peripheral neuropathy. Remove fluid resistant to diuretics, for example , pulmonary edema . Correct electrolyte and acid-base imbalances, for example, hyperkalaemia greater than 6.5 mmol/L where there are ECG changes, increasing acidosis (pH < 7.1 or serum bicarbonate < 10 mmol/L) despite bicarbonate therapy. To correct fluid overload. INTRODUCTION

4. The types of RRTs used in clinical practice for AKI and with the addition of kidney transplantation for ESRD secondary to CKD are: Hemodialysis Peritoneal Dialysis Haemofiltration Hemodiafiltration. TYPES

5. Although the basic principles of these replacement therapies are same, clearance rates, that is, the extent of solute removal, vary. In all types of dialysis, blood is presented to a dialysis solution across some form of semi-permeable membrane that allow free movement of low molecular weight compounds. The processes by which movement of substances occur are : Dialysis

6. Diffusion : Diffusion depends upon concentration differences between blood and dialysate and molecular size. Water and low molecular weight solutes( up to molecular weight of about 10,000) move through pores in the semi-permeable membrane to establish equilibrium. Smaller molecules can be cleared from blood more effectively as they move more easily through pores in the membrane. E.g. Hemodialysis. Dialysis

7. 2. Ultrafiltration : A pressure gradient (either positive or negative) across a semi-permeable membrane will produce a net directional movement of fluid from relative high to low pressure regions. The quantity of fluid dialysed is the ultrafitration volume. E.g. Hemodialysis. 3. Convection : Any molecule carried by ultra filtrate may move passively with the flow of convection. Larger molecules are cleared more effectively by convection. E.g. Haemofiltration , Hemodiafiltration Dialysis

8. Dialysis CAN • Remove waste products (e.g. urea, creatinine, phosphorus, etc.) • Remove excess water • Correct high or imbalanced levels of potassium, chloride, sodium, etc. in the blood Dialysis CAN’T • Automatically regulate blood pressure • Produce hormones like Erythropoetin (EPO) • Regulate normal calcium levels Most frequently used for patients who have kidney failure, but may also be used to quickly remove drugs or poisons in acute situations. Dialysis

9. DIALYSATE The composition of dialysate used varies according to clinical need. A standard solution aims to allow a net outflow of potassium from the blood, at a rate below that to create hypokalaemia , and a net inflow of calcium. Two fluids are used in dialysis. The dialysis fluid or dialysate and the other fluid being blood. Dialysate is the fluid and solutes in a dialysis process that flow through the dialyzer, do not pass through the membrane, and are discarded along with removed toxic substances after leaving the dialyzer.

10. Sodium 130.0 - 145.0 Potassium 0 - 3.0 Calcium 0 - 2.0 Magnesium 0 - 1.2 Acetate/Lactate 32.0 - 45.0 Chloride 90.0 - 120.0 Glucose 0 - 12.0 A typical composition would be: mmol / l Bicarbonate 32.0-35.0 pH 7.5-7.7 Hemodialysate : Peritoneal dialysate : pH 5.5 sodium 141-145.0 calcium 1.7-2.0 magnesium 0.7-1.2 chloride 97-101 lactate 41-45

11. Types

12. HEMODIALYSIS The blood goes through a machine that has special filters. The blood comes out of the patient through a catheter (a flexible tube) that is inserted into the vein. The filters do what the kidney's do; they filter out the waste products from the blood. The filtered blood then returns to the patient via another catheter. The patient is, in effect, connected to a kind of artificial kidney. Hemodialysis usually lasts about 3 to 4 hours each week. The duration of each session depends on how well the patient's kidneys work, and how much fluid weight the patient has gained between treatments. This is a method that is used to achieve the extracorporeal removal of waste products such as creatinine and urea and free water from the blood when the kidneys are in a state of renal failure.

13. HEMODIALYSIS Hemodialysis can be performed in either intermittent or continuous schedules. The latter regimen is preferable in the critical care situation, providing 24 hour control and minimising swings in blood volume and electrolyte composition that are found using intermittent regimens. The capital cost of Hemodialysis is considerable , requires specially trained staff and is seldom undertaken outside a renal unit. Hemodialysis can be used in patients who have recently undergone abdominal surgery in whom peritoneal dialysis would be ill advised.

14. PERITONEAL DIALYSIS In Peritoneal dialysis, special fluid is instilled through a permanent catheter in the lower abdomen. A thin membrane, called the peritoneum, lines the walls of the peritoneal cavity and covers all the organs contained in it. Dialysis fluid is introduced to the peritoneal cavity through a catheter placed in the lower part of the abdomen. Here the peritoneum serves as the dialysis membrane. The peritoneal cavity can often hold more then 3 litres , but in clinical practice only 1.5 – 2.5L of fluid are used.

15. Fluid is removed by ultrafiltration driven by an osmotic pressure gradient. When the dialysis fluid is drained from the abdominal cavity, it contains waste products and excess fluid extracted from the blood. The concentration of this osmotic agent is chosen to give just the fluid removal needed. In most cases glucose is used to create the osmotic pressure. An osmotic pressure gradient is applied by the addition to the dialysis fluid of an osmotic agent which will “suck” fluid from the blood.

16. There are 2 principle types of peritoneal dialysis: Continuous ambulatory peritoneal dialysis- this requires no machinery and can be done by the patient or a caregiver. The dialysate passes from a plastic bag through the catheter and into your abdomen. The dialysate stays in your abdomen with the catheter sealed for four to six hours. After that time, you drain the solution back into the bag. Then you refill your abdomen with fresh solution through the same catheter. The process of draining the dialysate and replacing fresh solution takes 30 to 40 minutes. Continuous cyclic peritoneal dialysis- - a machine does the dialysis fluid exchanges. It is generally done during the night while the patient sleeps. This needs to be done every night. Each session lasts from ten to twelve hours.

17. PROCEDURE One important step before starting regular hemodialysis sessions is preparing a vascular access, which is the site on your body where blood is removed and returned during dialysis. To maximize the amount of blood cleansed during hemodialysis treatments, the vascular access should allow continuous high volumes of blood flow. A vascular access should be prepared weeks or months before you start dialysis. The early preparation of the vascular access will allow easier and more efficient removal and replacement of your blood with fewer complications.

18. AV fistula: Its made by connecting an artery directly to a vein, frequently in the forearm. Connecting the artery to the vein causes more blood to flow into the vein. As a result, the vein grows larger and stronger, making repeated needle insertions for hemodialysis treatments easier.

19. AV graft: If you have small veins that won’t develop properly into a fistula, you can get a vascular access that connects an artery to a vein using a synthetic tube, or graft, implanted under the skin in your arm. The graft becomes an artificial vein that can be used repeatedly for needle placement and blood access during hemodialysis . A graft doesn’t need to develop as a fistula does, so it can be used sooner after placement, often within 2 or 3 weeks.

20. Venous catheter: A venous catheter is a tube with two channels branching out at one end. The tube is inserted into one of the large central veins in the neck so that the tip with two channels hangs outside the body, resting on the chest. A venous catheter can be used immediately after it's inserted. The dialysis machine is connected to each of the channels — one to drain blood out of the patient and into the dialysis machine so the blood can be filtered. The second channel returns the filtered blood back to the patient.  

21. Dialysis adequacy A few signs and symptoms of not getting enough dialysis are: Poor appetite Weakness and tiredness Itchy skin Mettalic taste in the mouth Swelling in the hands and feet Difficulty in breathing especially during exercising Inadequate dialysis can be extremely serious. It is important to pay attention to these symptoms and to act on them quickly.

22. Haemofiltration Haemofiltration is an alternative technique to dialysis where simplicity of use , fine fluid balance control and low cost have ensured its widespread application in the treatment of AKI. A similar arrangement to Hemodialysis is employed, but dialysis fluid is not used. The hydrostatic pressure of the blood drives a filtrate, similar to interstitial fluid, across a high-permeability dialyzer by ultra filtration. During haemofiltration, a patient's blood is passed through a set of tubing (a  filtration circuit ) via a machine to a semi permeable membrane(the  filter ) where waste products and water (collectively called  ultra filtrate ) are removed by convection. Replacement fluid is added and the blood is returned to the patient. Solute movement with haemofiltration is governed by convection rather than by diffusion. With haemofiltration, dialysate is not used. Instead, a positive hydrostatic pressure drives water and solutes across the filter membrane from the blood compartment to the filtrate compartment, from which it is drained. Solutes, both small and large, get dragged through the membrane at a similar rate by the flow of water that has been engendered by the hydrostatic pressure. Thus convection overcomes the reduced removal rate of larger solutes (due to their slow speed of diffusion) seen in Hemodialysis. Haemofiltration can be intermittent or continuous .

23. Haemodiafiltration Hemodiafiltration is a technique that combines the ability to clear small molecules, as in Hemodialysis , with large-molecule clearance of haemofiltration. It is combination of Hemodialysis and haemofiltration. It is more expensive than traditional Hemodialysis, but does offer potential benefits.

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