Hemodialysis is a medical procedure that serves as a life-sustaining treatment for individuals whose kidneys are no longer functioning adequately. It involves using a machine to filter waste products and excess fluid from the blood. This process helps maintain the body’s internal balance and is a common form of renal replacement therapy.
Understanding the Need
Healthy kidneys perform several essential functions, including filtering waste products and excess water from the blood, balancing minerals, and regulating blood pressure. When kidney function declines significantly, often due to conditions like diabetes or high blood pressure, the body can no longer effectively remove these waste products and fluids. This severe decline is known as end-stage renal disease (ESRD) or kidney failure.
The accumulation of waste products and excess fluid can lead to serious health issues, a condition called uremia. Symptoms of this buildup include fatigue, swelling, nausea, and shortness of breath. Hemodialysis becomes necessary to prevent these toxic substances from reaching dangerous levels, helping to control symptoms and extend life.
The Hemodialysis Process
Hemodialysis involves circulating a patient’s blood outside their body through a specialized machine that acts as an artificial kidney. This machine contains a filter called a dialyzer, composed of a semi-permeable membrane. Blood flows through one side of this membrane, while a cleaning solution known as dialysate flows in the opposite direction on the other side.
The dialyzer works on the principle of diffusion: waste products and excess fluid, highly concentrated in the blood, move across the semi-permeable membrane into the dialysate, which has lower concentrations. Important blood components like blood cells and proteins are too large to pass through the membrane and remain in the blood. The dialysate contains specific levels of minerals and electrolytes to balance these substances in the blood. After filtration, the cleaned blood is returned to the patient’s body, while the used dialysate, now containing the removed waste, is discarded. This continuous circulation allows the machine to process the body’s entire blood volume multiple times during a single session.
Vascular Access
To perform hemodialysis, reliable access to the patient’s bloodstream is necessary for blood to flow to and from the dialysis machine at a high rate. This is achieved through a surgically created vascular access, typically placed weeks or months before dialysis begins for healing and maturation. There are three main types of vascular access: arteriovenous (AV) fistula, AV graft, and central venous catheter.
An AV fistula is the preferred option for long-term hemodialysis due to its lowest risk of infection and clotting, and longest lifespan. It is created by surgically connecting an artery directly to a vein, usually in the arm. This increases blood flow and pressure in the vein, causing it to enlarge and strengthen, making it suitable for repeated needle insertions.
If a fistula cannot be created, an AV graft is an alternative, using a synthetic tube to connect an artery to a vein. Grafts can be used sooner than fistulas but have a higher risk of infection and clotting. A central venous catheter, a tube inserted into a large vein in the neck or chest, is typically used for temporary access, especially when immediate dialysis is needed or while a fistula or graft matures. Catheters carry the highest risk of infection and are not recommended for long-term use.
Living with Hemodialysis
Hemodialysis treatments are performed three times a week, with each session lasting three to five hours. During the procedure, patients sit or recline, often using the time for activities like reading or watching television. Common experiences during or after treatment include fatigue, low blood pressure, or muscle cramps. Low blood pressure can occur if too much fluid is removed too quickly, sometimes accompanied by nausea or dizziness. Muscle cramps are also common.
Living with hemodialysis involves significant lifestyle adjustments, particularly concerning diet and fluid intake. Patients limit fluid consumption to about four to five 8-ounce cups daily, depending on urine output and weight gain between sessions. This restriction prevents excessive fluid buildup, which can lead to complications like high blood pressure and shortness of breath.
Dietary modifications include limiting foods high in sodium, potassium, and phosphorus, as these minerals can accumulate to harmful levels when kidneys are not functioning. Some patients receive hemodialysis in a dedicated clinic, while others may be trained to perform treatments at home, offering more flexibility and potentially more frequent or longer sessions. Home hemodialysis machines are smaller and designed for easier use.