Dialysis Machine.

DIALYSIS

A normal kidney performs both filtration and cleaning process in the human body. It filters the impurities from the blood and removes extra toxins, excess water and other chemicals from the body. The kidney also helps in regulating blood pressure and other elements like sodium, potassium and bicarbonate in the body. It also provides vitamin D.

Dialysis is a procedure carried out in individuals having kidney failure (i.e a condition in which the kidney’s ability to remove toxins and excess fluid from the body fails). This procedure uses a machine to remove excess waste, fluids and salt from the body and to keep the patient’s body in balance.

Types of Dialysis

There are two types of dialysis

1. Hemodialysis 
2. Peritoneal dialysis

Hemodialysis

Hemodialysis is the most commonly used method. This consists of an artificial kidney (dialyser) which removes wastes and excess fluids from the blood. During hemodialysis, the surgeon performs an operation to remove the blood from the patient’s body and allow it to enter into the dialysis machine. This artificial kidney purifies the blood and it is then returned back to the body.

Arteriovenous (AV) fistula is most commonly preferred for long term treatments. AV fistula is a surgical connection made between the artery and vein. Impure blood is removed from the surgical site through a catheter for filtration and purified blood is entered into the body.

If the blood vessel does not support adequate blood flow, then the surgeon connects a plastic tube or catheter for easier flow of blood. This type is known as the AV graft. Another method called vascular access catheter is also performed. In this method, the catheter is inserted into the large vein in the neck. The process of hemodialysis lasts up to 3 to 5 hours and it is done three times per week. It also depends upon the patient’s condition on how much waste is accumulated in the body. Patient’s must undergo hemodialysis in hospitals and dialysis centres.

Peritoneal Dialysis

Peritoneal dialysis can be performed by the individual at home. It consists of a dialysate, catheter and a drainage bag. The catheter is inserted into the peritoneum (a membrane covering the abdomen). 

Dialysate is then passed through the catheter and it enters the abdomen. This dialysate absorbs excess waste and fluids from the blood and then it is allowed to drain. It gets collected in the drainage bag. This process takes only a few hours and is done five to six times a day. One can undergo this method even when sleeping or walking. Peritoneal dialysis is done to patients having acute renal failure which lasts up to a short span of time and recovers automatically.

Peritoneal dialysis is otherwise performed in three ways:-

1. Continuous ambulatory peritoneal dialysis (CAPD) – This method is performed several times a day. During this process, the patient must be awake. This method does not need any machine.

2. Continuous cycling peritoneal dialysis (CCPD) – In this method, a machine is used for sending the dialysate into the peritoneum and also for removing the drainage from the abdominal cavity. This must be performed only when the patient falls asleep.

3. Intermittent peritoneal dialysis (IPD) – This is similar to CCPD, but it takes a longer time and is performed in the hospital.

Risks of Hemodialysis:-

• It causes low blood pressure
• Anaemia
• Difficulty in sleeping
• Muscle cramps
• Bloodstream infections or sepsis

Risks of Peritoneal Dialysis:-

• A weakening of abdominal muscles
• Hernia
• Stomach pain
• Infections in the abdominal cavity

Deciding to Stop Dialysis

Before the conclusion, one must discuss with the doctor about stopping dialysis that he/she is undergoing. Without proper advice from the surgeon, one must not come to the conclusion because it may cause any serious harm.

Dialysis Machine

A Dialysis machine is a therapeutic device used in the process of dialysis for removing excess waste and for purifying the blood. Blood is removed from the patient’s body and is allowed to enter the dialyser (artificial kidney) in the machine. An anticoagulant (heparin injection) is present in order to prevent the blood from clotting. The dialyser is a semipermeable membrane which consists of dialysate( a mixture of water and electrolytes). Blood is purified in the dialyser and is pumped back to the body. Excess amount of urea and salt from the blood is removed by the dialyser. 

The dialysate maintains the blood at a particular temperature. This is because a higher temperature will damage the blood components. 

If the temperature rises in the machine, safety cut valve is used to switch off the heater. However, before allowing the blood to enter into the patient body, the blood is warmed by the heater. Therefore, the temperature is maintained between 36 – 42 degree Celsius. For controlling the temperature in the machine, it consists of a thermostat and a proportional controller. 

This controls the power given to the heater. Pressure in the dialysis is monitored by the transducer. Negative pressure in the dialysate is created by the effluent pump. Therefore, if pressure raises, the effluent pump goes off. Dialysis machine also consists of a blood leak detector to monitor any leakage in the tubings or any other part of the machine. After completing the purification process, the used dialysate enters into the waste-collecting tank. Purified blood passes through the patient body.

Principle of Dialysis

The main principle of dialysis is based on diffusion and ultrafiltration. 

In Diffusion, fluid flows from high concentration to low concentration through a semi-permeable membrane. In this process, impurities from blood diffuse into the dialysate, whereas electrolytes and other minerals diffuse into the blood from the dialysate. Therefore, purified blood is allowed to enter into the body and the dialysate is pumped out.

Ultrafiltration is the process of removing excess fluid from the body from positive to a negative pressure gradient (i.e high to low pressure). Here, blood comes under positive pressure, dialysate come under negative pressure.

Components& Functions of the Dialysis Machine.

• Blood Pump & Tubings – A blood pump is used to pump blood from the body to the dialysis machine

• Syringe – A drug called heparin is used in the injection. This is used to prevent blood clotting.

• Dialyser – Dialyser is also known as an artificial kidney. It is filled with a combination of water and electrolytes called dialysate. In this dialyser, blood is filtered and purified.

• Pressure Monitor – Arterial pressure monitor: This is used to detect the pressure between the blood coming from AV fistula and blood pump.

• Venous Pressure Monitor - This part usually measures positive pressure in the system. Low blood flow or any other disconnection in the circuit represents low venous pressure.

• Sensors – Sensors are used for monitoring various parameters in the circuit. This includes parameters like blood pressure, dialyser pressure gradient, temperature, Oxygen saturation etc.

• Air Detector – Air detector is used near the venous pressure line. This is used to detect any air leakage or the presence of any air molecules in the blood entering the patient’s body.

• Alarms – Alarms are used to prevent errors occurring in the functioning of the machine. This is used to detect blood flow, blood pressure, temperature, a mixture of dialysate.

Hemodialysis Catheter

A hemodialysis catheter is used to exchange blood from the patient to the dialysis machine. The catheter is of two types: with cuff and without a cuff. Catheter without cuff is used only for a shorter time (in peritoneal dialysis). The catheter consists of two openings. Red coloured opening indicates removing of arterial blood from the patient’s body into the machine. Blue colour indicates venous opening where purified blood is allowed to pass through the patient.

How to Prepare for Hemodialysis:-

Before performing dialysis treatment, the surgeon advises the patient to undergo a minor surgery called AV fistula or AV graft. This surgery is done before 3 to 4 weeks prior to the dialysis treatment. The time is given to heal the operated site. Vital functions of the patient’s body are also monitored during the treatment. They will monitor the height, weight, body temperature and other chronic conditions like blood pressure and diabetes are measured.

What Happens if There is a Power Failure During Dialysis:-

During a power failure, the dialysis machine stops working. Lights will turn OFF, and an alarm indicates power failure in the machine. The blood pump is operated by hand either to return the blood immediately or to keep the blood in circulation (incase if the machine gets power soon.) Once the blood is returned to the patient, the circuit must be disconnected. And the surgeon will ask the patient to come for another day. If the power is ON immediately after a power cut, the system will be able to resume the filtration process.

Problems and Troubleshooting:-

• Be sure to keep the machine clean and safe. Thoroughly clean the droplets, stains of blood as soon as possible to prevent infections.

• The person may be infected when operating the machine. So be careful when handling disposable products.

• Be sure the water, dialysate concentrate is good in quality in order to enhance performance and safety.

• Confirm whether all cable connections are correct and safe to prevent electric shocks.

• Do not operate the machine with wet or bare hands. Always use gloves to prevent infections.

Maintenance:-

• Calibration must be done regularly to the dialysate pump and blood pump.

• Preventive maintenance should be done to avoid equipment breakdown.

• Accurate timing must be maintained for ultrafiltration rate.

• Clean and disinfect the machine after using on each patient.

• Clean the machine from top to bottom using disinfectant cloths/wipes.

• Install the machine in a place where it is free from moisture 

• Check the power supply

• Check the earth connections properly

Risks and Troubleshooting

Troubleshooting the machine should be done by qualified personnel.

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Article Prepared By:-

       

 👉 Sumitha Ramadass

    

Reference

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