DIALYSIS
Dialysis is a process used to remove unwanted fluid and waste product from the body when the kidneys are unable to do so because of impaired function or when toxins or poisons must be removed immediately to prevent permanent or life-threatening damage.
Dialysis refers to the diffusion of solute molecules through a semipermeable membrane, passing from the side of higher concentration to that of lower concentration [The purpose of dialysis is to maintain the life and well-being of the Pt.] It is a substitute for some kidney excretory functions but does not replace the kidney's endocrine and metabolic functions.
Indications
1. To remove waste products
2. To correct fluid and electrolyte imbalance:
3. To treat drug overdoses.
HAEMODIALYSIS
Haemodialysis is a process of cleansing the blood of accumulated waste products. It is used for patients with end-stage renal failure or for acutely ill Patients who require short-term dialysis.
These Patients must undergo dialysis treatment for the rest of their lives (usually 3 times a week for 4 hours per treatment) or until they receive a successful kidney
Requirements For Haemodialysis
1. Access to the Patients circulate
2. A dialyzer with a semi permeable membrane (the artificial kidney)
3. An appropriate dialysate bath
Access to the Patients Circulation
- A-V shunt (arteriovenous shunt)- [can be placed wherever an artery and vein are close together). The silastic tubing is placed in the radial artery and the adjacent vein, but the ankle can also be used.
- It is used only temporarily while the Patient awaits maturation of a newly created fistula or graft.
- The tubing from the artery and vein exits the skin and joins with a connecting piece to form a closed are when dialysis is performed, the connector is removed and the tubing coming from the artery is inserted into tubing going to the artificial kidney.
- Tubing from the artificial kidney is inserted into the venous segment of the shunt.
- The blood then can pass from the Patients vascular system through the artificial kidney filtering system, and back again into the Patients’ blood vessels (vein). The blood is traveling via a blood pump from 200-300 ml/min. depending on the Patients size, the condition of the blood vessels being used and the overall condition of the Patients vascular system)
- The shunt is cleaned before each dialysis with antiseptic solution, after which a dry sterile dressing is applied and secured with a stretchable gauze bandage.
- The Patient is instructed to observe the shunt several times a day [for evidence of clothing) and to avoid wearing a watch or Jewellery or carrying a handbag over the shunt arm.
- Avoid use of tourniquet for venipuncture and application of pressure cuff.
Complications
Infection and haemorrhage [can separate at the connection site. It is also a visible reminder of the patient’s disability.
FISTULA: The fistula is created surgically by connecting or joining (anastomoses) an artery to a vein, either, side-to-side, end-to-side or end to end.
It takes 4-6 weeks to be ready for use.
It gives time for healing to take place and for the venous segment to dilate in order to accommodate 2 large-bore (14-gauze/16-gauze) needles.
GRAFT: A graft is created by a autologous saphenous vein or from polytetrafluorethylene (PTFE), OTFE
Grafts are usually placed in the forearm, upper arm or upper thigh.
Ready to use in 2-3 weeks.
PRINCIPLES OF HEMODIALYSIS
[The objectives of haemodialysis are to extract toxic nitrogenous substances from the blood and to remove excess water.
- Heparin added to the blood, prevents clothing."
- Blood passes by means of a pump, through the [artificial kidney machine to the semi permeable membrane or] artificial kidney.
- Dialysate bath flows on the other side of the membrane...
- Toxins and wastes in the blood are removed by diffusion moving from an area of greater concentration in the blood to an area of lesser concentration in the dialysate excess water is removed from the blood by osmosis.
- Blood and dialysate do not mix. Dialysate is composed of all the important electrolytes [in their ideal extra cellular concentrations]. [The electrolytes in the blood can be brought under control by proper adjustment of the dialysate bath]
[The removal of water can be controlled by creating a desired gradient (ultra filtration)). The body's buffer system is maintained by the addition of acetate, which is diffused from the dialysate into the Patient and metabolizes to form bicarbonate.
- Purified blood is returned to the body through the Patients vein.
- During dialysis, the Patient, the dialyzer and the dialysate bath require constant monitoring to detect numerous complications – e.g. Air embolism, [inadequate or excessive ultrafiltration] blood leaks, contamination and shunt or fistula complications, hypotension, [rapid removal of vascular volume), muscle cramps [too rapid removal of Na and H₂O1
[The dialyzer primed with saline solution. Saline solution is infused into Patient as the blood fills the dialyzer circuit. Dialysate is warmed to body temperature. Blood propelled through dialyzer by a blood pump at the flow rate 200-500 ml/min, while the dialysate circulates in the opposite direction-300-900 ml/min.
Nursing Management
1. Vital signs are checked every 30-60 mins.
2. Constant monitoring of hemodynamic status, electrolytes and acid -base balance, as well as maintenance of sterility and a closed system.
3. Usually performed by a specially trained nurse.
4. Dietary management-restriction or adjustment of protein, sodium, potassium or fluid intake
[Many drugs are excreted wholly of in part by the kidneys). Patients requiring drug therapy (cardiac glycosides, antibiotics. antiarrhythmic agents, antihypertensive agents)] are monitored closely to ensure that blood and tissue level of these drugs are maintained without toxic accumulation
Haemo Filtration/Continuous Arteriovenous Haemo Filtration (CAVH)
- It temporarily replaces kidney function.
- Used for Patients with fluid overload [secondary to oliguric renal failure] or those Patients whose kidneys are unable to handle their. acute high metabolic or nutritional needs.
- Blood is circulated through a small volume, low-resistance filter by the pressure of the Patient's own arterial pressure.
- Excess fluids, electrolytes and nitrogenous waste products are removed by ultrafiltration.
