Dialysis removes the waste products and extra fluid from your blood by filtering them through a membrane/filter, similar to the way healthy kidneys would. During dialysis, blood is on one side of the membrane/filter and a special fluid called dialysate (containing water, electrolytes, and minerals) is on the other. Small waste products in your blood flow through the membrane/filter and into the dialysate. Removal of dangerous substances from the body when the kidneys are impaired; then we need a renal replacement function to assist is removal of dangerous materials that may endanger the life of those patients. Dialysis can be done by different techniques (1); different forms of dialysis are available as hemodialysis (artificial kidney machine); hemofiltration (either as continuous arteriovenous CAVH— in urgent or catastrophic conditions as during war –or continuous veno-venous CVVH ) or it can be through peritoneal dialysis. renal transplantation is the final best modality of renal replacement. (2)
Principles of dialysis:
Hemodialysis = solute passively diffuses down concentration gradient
Dialysate flows countercurrent to blood flow.
Urea, creatinine, K move from blood to dialysate
Ca and bicarb move from dialysate to blood.
Hemofiltration: uses hydrostatic pressure gradient to induce filtration / convection plasma water + solutes across membrane.
Hemodiafiltration: combination of dialysis and filtration.
Convective transport of small and middle molecular weight solutes in same direction as water. Usually requires substitution fluid to prevent excess fluid removal.
Although the use of pump-driven veno-venous circuits increases the technical complexity of therapy (3), the elimination of the hazards of prolonged arterial cannulation and the provision of higher solute clearances make these the preferred modes of therapy. Theoretically, convective therapies (hemofiltration) provide greater clearance of higher molecular weight solutes than diffusive therapies (hemodialysis); however, no studies have demonstrated an association between the mechanism of solute transport and clinical outcomes.
Larger particles, like red blood cells, remain in your blood. In this way, your blood is cleaned.
Indications for RRT-renal replacement therapy:
Acute management of life-threatening complications of AKI-(acute kidney injury):
A: Metabolic acidosis (pH less than 7.1)
E: Electrolytes — Hyperkalemia (K >6.5 meq/L) or rapidly rising K)
I: Ingestion — Certain alcohol and drug intoxications
O: Refractory fluid overload
U: Uremia, ie. pericarditis, neuropathy, decline in mental status.
In hemodialysis, blood is pumped out of your body to an artificial kidney machine, and returned to your body by tubes that connect you to the machine. In peritoneal dialysis, the inside lining of your own belly acts as a natural filter.
Ultrafiltration: In hemodialysis water is removed by hydrostatic ultrafiltration which is a pressure phenomenon. The pressure on the dialysate side is lowered and water moves from a place of higher pressure to one of lower pressure, i.e., out of the plasma.
Sequential dialysis techniques (i.e. pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability.
There are three different types of peritoneal dialysis:
- Continuous ambulatory peritoneal dialysis (CAPD): Does not require a machine. Exchanges, often referred to as “passes,” can be done three to five times a day, during waking hours.
- Continuous cyclic peritoneal dialysis (CCPD): Requires the use of a special dialysis machine that can be used in the home. This type of dialysis is done automatically, even while you are asleep.
- Intermittent peritoneal dialysis (IPD): Uses the same type of machine as CCPD, but treatments take longer. IPD can be done at home, but it is usually in the hospital.
Peritoneal Dialysis: Possible Complications
Possible complications of peritoneal dialysis include an infection of the peritoneum, or peritonitis, where the catheter enters the body. Peritonitis causes fever and stomach pain. A dietitian will help plan your diet during peritoneal dialysis, so we can ensure you are choosing appropriate meals. During dialysis:
- You may have different protein, salt and fluid needs.
- You may have different potassium restrictions.
- You may need to reduce your calorie intake, since the sugar in the dialysate may cause weight gain.
Hemodialysis is can be performed at home or in a dialysis center or hospital by trained healthcare professionals. During the procedure, we will:
- Surgically place a special type of access, called an arteriovenous (AV) fistula, usually in your arm. We will need to join an artery and a vein together. (We may also insert an external, central intravenous (IV) catheter, but is less common for long-term dialysis.)
- Connect you to a large hemodialysis machine.
- The machine drains the blood, bathes it in a special dialysate solution to remove waste substances and fluid and then returns it to your bloodstream.
As in dialysis, in hemofiltration one achieves movement of solutes across a semi-permeable membrane. However, solute movement with hemofiltration is governed by convection rather than by diffusion. With hemofiltration, dialysate is not used. (4)
Sustained low efficiency dialysis (SLED) is increasingly used as a renal replacement modality in critically ill patients with acute kidney injury (AKI) and hemodynamic instability. SLED may reduce the hemodynamic perturbations of intermittent hemodialysis, while obviating the resource demands of CRRT.New researches for dialysis options continue to increase for patients whether they choose at home peritoneal dialysis or at home hemodialysis.
New advances in vascular access in hemodialysis patient’s lifeline makes life-saving hemodialysis treatments possible.(5) Two types of hemodialysis vascular access designed for long-term use include the arteriovenous fistula (AVF) and the AV graft (AVG). A third type of vascular access—the central venous catheter (CVC)—is primarily intended for short-term use due to the number of complications related to this type of access.Both the AVF and the AVG have significantly better outcomes and less complications than the CVC. An important goal is minimizing or eliminating the length of time that these patients are exposed to the CVC as their access. In the recent past there have been two new techniques developed that have demonstrated the potential to aid in reaching this goal.
- Percutaneous Fistula Creation – Recently, percutaneous anastomosis devices have been developed as an alternative to surgical fistula creation, and early studies demonstrate promising results.
- Bioengineered Blood Vessels – Bioengineered blood vessels have been created from human cells and may help reduce the reliance on CVC’s as a form of hemodialysis access.
Complications of hemodialysis: (6)
While hemodialysis treatment can be efficient at replacing some of the kidney’s lost functions, you may experience some of the related conditions listed below, although not everyone experiences all of these issues. Your dialysis team can help you deal with them.
Low blood pressure (hypotension). A drop-in blood pressure is a common side effect of hemodialysis, particularly if you have diabetes. Low blood pressure may be accompanied by shortness of breath, abdominal cramps, muscle cramps, nausea or vomiting.
Muscle cramps. Although the cause is not clear, muscle cramps during hemodialysis are common. Sometimes the cramps can be eased by adjusting the hemodialysis prescription. Adjusting fluid and sodium intake between hemodialysis treatments also may help prevent symptoms during treatments.
Itching. Many people who undergo hemodialysis have itchy skin, which is often worse during or just after the procedure.
Sleep problems. People receiving hemodialysis often have trouble sleeping, sometimes because of breaks in breathing during sleep (sleep apnea) or because of aching, uncomfortable or restless legs.
Anemia. Not having enough red blood cells in your blood (anemia) is a common complication of kidney failure and hemodialysis. Failing kidneys reduce production of a hormone called erythropoietin which stimulates formation of red blood cells. Diet restrictions, poor absorption of iron, frequent blood tests, or removal of iron and vitamins by hemodialysis also can contribute to anemia.
Bone diseases. If your damaged kidneys are no longer able to process vitamin D, which helps you absorb calcium, your bones may weaken. In addition, overproduction of parathyroid hormone — a common complication of kidney failure — can release calcium from your bones.
High blood pressure (hypertension). If you consume too much salt or drink too much fluid, your high blood pressure is likely to get worse and lead to heart problems or strokes.
Fluid overload. Since fluid is removed from your body during hemodialysis, drinking more fluids than recommended between hemodialysis treatments may cause life-threatening complications, such as heart failure or fluid accumulation in your lungs (pulmonary edema).
Inflammation of the membrane surrounding the heart (pericarditis). Insufficient hemodialysis can lead to inflammation of the membrane surrounding your heart, which can interfere with your heart’s ability to pump blood to the rest of your body.
High potassium levels (hyperkalemia). Potassium is a mineral that is normally removed from your body by your kidneys. If you consume more potassium than recommended, your potassium level may become too high. In severe cases, too much potassium can cause your heart to stop. Velphoro(sucroferric oxyhydroxide) is a novel, non-absorbable iron-based phosphate binder with high binding potency. A starting dose of three pills a day is approved for use in chronic kidney disease patients on dialysis. In two years of real-world data, treatment with Velphoro increased the number of dialysis patients able to reach recommended levels of serum phosphorus with half the number of pills (four to five) compared to the most common phosphate binder (eight to nine pills per day).
Access site complications. such as infection, narrowing or ballooning of the blood vessel wall (aneurysm), or blockage ― can impact the quality of your hemodialysis. Follow your dialysis team’s instructions on how to check for changes in your access site that may indicate a problem.
Amyloidosis. Dialysis-related amyloidosis develops when proteins in blood are deposited on joints and tendons, causing pain, stiffness and fluid in the joints. The condition is more common in people who have undergone hemodialysis for more than five years.
Depression. Changes in mood are common in people with kidney failure.
Patients with acute kidney injury may need hemodialysis only for a short time until kidneys recover.Some research suggests that home dialysis is linked to:Better quality of life,Increased well-being;Reduced symptoms and less cramping, headaches and shortness of breath;Improved appetite, sleeping patterns, energy level and ability to concentrate. Both Peritoneal dialysis (PD) and hemodialysis (HD) are dialysis options for end-stage renal disease patients in whom preemptive kidney transplantation is not possible. The selection of PD or HD will usually be based on patient motivation, desire, geographic distance from an HD unit, physician and/or nurse bias, and patient education. Unfortunately, many patients are not educated on PD before beginning dialysis. Most studies show that the relative risk of death in patients on in-center HD versus PD changes over time with a lower risk on PD, especially in the first 3 months of dialysis. The survival advantage of PD continues for 1.5-2 years but, over time, the risk of death with PD equals or becomes greater than with in-center HD, depending on patient factors. Thus, PD survival is best at the start of dialysis. Patient satisfaction may be higher with PD, and PD costs are significantly lower than HD costs. Advances in dialysis technologies in recent times has highly simplified the home hemodialysis allowing it to be performed in the comforts of patients’ home. Development of smaller dialysis machine that can be placed on a nightstand; and simpler blood tubing and dialyzer connections, has resulted in increasing number of patients choosing this modality of dialysis to preserve their independence and high functional status. Though the typical duration for individual patient varies, these forms of dialysis can be tailored for an individual’s needs with 5-6 times a week frequency for dialysis with each individual session duration ranging from 3-6 hours. The shorter versions called short daily hemodialysis (SDHD) whereas the longer versions are typically performed at night and thus called nocturnal hemodialysis (NHD). The typical home hemodialysis allows a much higher clearance compared to other forms of dialysis and thus gives greater freedom in terms of dietary restriction and life style choices. no single type of dialysis (home Vs In-center dialysis, or Hemo Vs peritoneal dialysis) is superior to others in terms of hard clinical endpoints e.g. mortality or cardiovascular deaths. However, home dialysis modalities (both PD and HHD) provide significant advantages in multiple outcome parameters important to the management of patients with ESRD namely quality of life, freedom of travel, greater liberty from dietary restrictions, preservation of residual kidney function.