Hemodialysis
Hemodialysis, also spelled haemodialysis, or simply dialysis, is a process of filtering the blood of a person whose kidneys are not working normally. This type of dialysis achieves 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 kidney failure. Hemodialysis is one of three renal replacement therapies. An alternative method for extracorporeal separation of blood components such as plasma or cells is apheresis.
Hemodialysis can be an outpatient or inpatient therapy. Routine hemodialysis is conducted in a dialysis outpatient facility, either a purpose-built room in a hospital or a dedicated, stand-alone clinic. Less frequently hemodialysis is done at home. Dialysis treatments in a clinic are initiated and managed by specialized staff made up of nurses and technicians; dialysis treatments at home can be self-initiated and managed or done jointly with the assistance of a trained helper who is usually a family member.
Medical uses
Hemodialysis is the choice of renal replacement therapy for patients who need dialysis acutely, and for many patients as maintenance therapy. It provides excellent, rapid clearance of solutes.A nephrologist decides when hemodialysis is needed and the various parameters for a dialysis treatment. These include frequency, length of each treatment, and the blood and dialysis solution flow rates, as well as the size of the dialyzer. The composition of the dialysis solution is also sometimes adjusted in terms of its sodium, potassium, and bicarbonate levels. In general, the larger the body size of an individual, the more dialysis they will need. In North America and the UK, 3–4 hour treatments given 3 times a week are typical. For some patients, nephrologists may suggest an incremental approach, especially for those with substantial residual kidney function at the time of dialysis initiation. With "incremental hemodialysis", the initial dialysis prescription begins with fewer and/or shorter sessions per week—usually one or two 3 hour session—and gradually increases frequency and duration as kidney function declines. Four sessions per week may be prescribed for larger patients, as well as patients who have trouble with fluid overload.
There is growing interest in short daily home hemodialysis, which is 1.5 – 4 hr sessions given 5–7 times per week, usually at home. There is also interest in nocturnal dialysis, which involves dialyzing a patient, usually at home, for 8–10 hours per night, 3–6 nights per week. Nocturnal in-center dialysis, 3–4 times per week, was first described more than 40 years ago, and is offered at some dialysis units.
Adverse effects
Disadvantages
- Restricts independence, as people undergoing this procedure cannot travel around because of supplies' availability
- Requires more supplies such as high water quality and electricity
- Requires reliable technology like dialysis machines
- The procedure is complicated and requires that care givers have more knowledge
- Requires time to set up and clean dialysis machines, and expense with machines and associated staff
Complications
Fluid shifts
Hemodialysis often involves fluid removal, because most patients with renal failure pass little or no urine. Side effects caused by removing too much fluid and/or removing fluid too rapidly include low blood pressure, fatigue, chest pains, leg-cramps, nausea and headaches. These symptoms can occur during the treatment and can persist post treatment; they are sometimes collectively referred to as the dialysis hangover or dialysis washout. The severity of these symptoms is usually proportionate to the amount and speed of fluid removal. However, the impact of a given amount or rate of fluid removal can vary greatly from person to person and day to day. These side effects can be avoided and/or their severity lessened by limiting fluid intake between treatments or increasing the dose of dialysis e.g. dialyzing more often or longer per treatment than the standard three times a week, 3–4 hours per treatment schedule.Access-related
Since hemodialysis requires access to the circulatory system, patients undergoing hemodialysis may expose their circulatory system to microbes, which can lead to bacteremia, an infection affecting the heart valves or an infection affecting the bones. The risk of infection varies depending on the type of access used. Bleeding may also occur, again the risk varies depending on the type of access used. Infections can be minimized by strictly adhering to infection control best practices.Venous needle dislodgement
Venous needle dislodgement is a fatal complication of hemodialysis where the patient experiences rapid blood loss due to a faltering attachment of the needle to the venous access point.Anticoagulation-related
is the most commonly used anticoagulant in hemodialysis, as it is generally well tolerated and can be quickly reversed with protamine sulfate. Low-molecular weight heparin is however, becoming increasingly popular and is now the norm in western Europe. Compared to UHF, LMWH has the advantage of an easier mode of administration and reduced bleeding but the effect cannot be easily reversed. Heparin can infrequently cause a low platelet count due to a reaction called heparin-induced thrombocytopenia. The risk of HIT is lower with LMWH compared to UHF. In such patients, alternative anticoagulants may be used. Even though HIT causes a low platelet count it can paradoxically predispose thrombosis. When comparing UHF to LMWH for the risk of adverse effects, the evidence is uncertain as to which treatment approach to thin blood has the least side effects and what is the ideal treatment strategy for preventing blood clots during hemodialysis. In patients at high risk of bleeding, dialysis can be done without anticoagulation.First-use syndrome
First-use syndrome is a rare but severe anaphylactic reaction to the artificial kidney. Its symptoms include sneezing, wheezing, shortness of breath, back pain, chest pain, or sudden death. It can be caused by residual sterilant in the artificial kidney or the material of the membrane itself. In recent years, the incidence of first-use syndrome has decreased, due to an increased use of gamma irradiation, steam sterilization, or electron-beam radiation instead of chemical sterilants, and the development of new semipermeable membranes of higher biocompatibility. New methods of processing previously acceptable components of dialysis must always be considered. For example, in 2008, a series of first-use type of reactions, including deaths, occurred due to heparin contaminated during the manufacturing process with oversulfated chondroitin sulfate.Cardiovascular
Long term complications of hemodialysis include hemodialysis-associated amyloidosis, neuropathy and various forms of heart disease. Increasing the frequency and length of treatments has been shown to improve fluid overload and enlargement of the heart that is commonly seen in such patients.Vitamin deficiency
can occur in some patients having hemodialysis.Electrolyte imbalances
Although a dialysate fluid, which is a solution containing diluted electrolytes, is employed for the filtration of blood, haemodialysis can cause an electrolyte imbalance. These imbalances can derive from abnormal concentrations of potassium, and sodium. These electrolyte imbalances are associated with increased cardiovascular mortality.Mechanism and technique
The principle of hemodialysis is the same as other methods of dialysis; it involves diffusion of solutes across a semipermeable membrane. Hemodialysis utilizes counter current flow, where the dialysate is flowing in the opposite direction to blood flow in the extracorporeal circuit. Counter-current flow maintains the concentration gradient across the membrane at a maximum and increases the efficiency of the dialysis.Fluid removal is achieved by altering the hydrostatic pressure of the dialysate compartment, causing free water and some dissolved solutes to move across the membrane along a created pressure gradient.
The dialysis solution that is used may be a sterilized solution of mineral ions and is called dialysate. Urea and other waste products including potassium, and phosphate diffuse into the dialysis solution. However, concentrations of sodium and chloride are similar to those of normal plasma to prevent loss. Sodium bicarbonate is added in a higher concentration than plasma to correct blood acidity. A small amount of glucose is also commonly used. The concentration of electrolytes in the dialysate is adjusted depending on the patient's status before the dialysis. If a high concentration of sodium is added to the dialysate, the patient can become thirsty and end up accumulating body fluids, which can lead to heart damage. On the contrary, low concentrations of sodium in the dialysate solution have been associated with a low blood pressure and intradialytic weight gain, which are markers of improved outcomes. However, the benefits of using a low concentration of sodium have not been demonstrated yet, since these patients can also develop cramps, intradialytic hypotension and low sodium in serum, which are symptoms associated with a high mortality risk.
Note that this is a different process to the related technique of hemofiltration.