Physiology 2

INTRODUCTION Dialysis is a method of removing toxic substances (impurities or wastes) from the blood when the kidneys are unable to do so. The kidneys function as filters for the blood, removing waste products. They also: regulate body water, maintain electrolyte balance and ensure that the blood pH remains between 7.35 and 7.45.Dialysis replaces some of the functions for kidneys that aren't working properly. It removes contaminants from the blood that could, and eventually would, lead to death if the kidney is not functioning(Mark, F.R et,al). Since dialysis is not a constant process, it cannot monitor body functions as do normal kidneys, but it can eliminate waste products and restore electrolyte and pH levels on an asneeded basis. Dialysis is most often used for patients who have kidney failure, but it can also quickly remove drugs or poisons in acute situations. This technique can be lifesaving in people with acute or chronic kidney failure(.Zbylut, K.I ,et,al) PROCESS IN DIALYSIS Hemodialysis uses a machine filter called a dialyzer or artificial kidney to remove excess water and salt to balance the other electrolytes in the body, and to remove waste products of metabolism. Blood flows through tubing into the machine, where it passes next to a filter membrane. A specialized chemical solution (dialysate) flows on the other side of the membrane. The dialysate is formulated to draw impurities from blood through the filter membrane. Blood and dialysate never touch in the artificial kidney machine. For this type of dialysis access to the blood vessels need to be surgically created so that large amounts of blood can flow into the machine and back to the body(Tolkoff , N). Surgeons can build a fistula, a connection between a large artery and vein in the body, usually in the arm, that causes a large amount of blood flow into the vein. This makes the vein large and its walls thicker so that it can tolerate repeated needle sticks to attach tubing from the body to the machine. Fistula takes long to mature enough, significant planning is required if hemolysis is considered an option. If the kidney failure happens acutely and there is no time to build a fistula, special catheters may be inserted into large blood vessels of the arm, leg or chest. The catheters may be left in place up to three weeks.( Raymond, C.P).

TYPES OF DIALYSIS 1

There are two main types of dialysis: hemodialysis and peritoneal dialysis. Hemodialysis uses a special type of filter to remove excess waste products and water from the body. Peritoneal dialysis uses a fluid that is placed into the patient's stomach cavity through a special plastic tube to remove excess waste products and fluid from the body. During hemodialysis, blood passes from the patient's body through a filter in the dialysis machine, called a "dialysis membrane." For this procedure, the patient has a specialized plastic tube placed between an artery and a vein in the arm or leg (called a "gortex graft"). Sometimes, a direct connection is made between an artery and a vein in the arm. This procedure is called a "Cimino fistula." Needles are then placed in the graft or fistula, and blood passes to the dialysis machine, through the filter, and back to the patient. In the dialysis machine, a solution on the other side of the filter receives the waste products from the patient. Peritoneal dialysis uses the patient’s own body tissues inside of the belly (abdominal cavity) to act as the filter. The intestines lie in the abdominal cavity, the space between the abdominal wall and the spine. A plastic tube called a "dialysis catheter" is placed through the abdominal wall into the abdominal cavity. A special fluid is then flushed into the abdominal cavity and washes around the intestines. The intestinal walls act as a filter between this fluid and the blood stream. By using different types of solutions, waste products and excess water can be removed from the body through this process. COMPLICATIONS OF DIALYSIS Even though the safety of the hemodialytic procedure has improved greatly over the years, the procedure is not without risks. Common problems are listed below. Hypotension A decrease in blood pressure is the most frequent complication reported during hemodialysis. When fluid is removed during hemodialysis, the osmotic pressure is increased and this prompts refilling from the interstitial space. The interstitial space is then refilled by fluid from the intracellular space. Excessive ultrafiltration with inadequate vascular refilling plays a major role in dialysis induced hypotension. The immediate treatment to hypotension is to discontinue dialysis and place the patient in a trendelenburg position. This will increase cardiac filling and may increase the blood pressure promptly( Mitch, W.E.,.et.al) Cramps In the majority of hemodialysis patients, cramps occur toward the end of the dialysis procedure after a significant volume of fluid has been removed by ultrafiltration. The 2

immediate treatment for cramps is directed at restoring intravascular volume through the use of small boluses of isotonic saline. Prevention of cramps has been attempted with the prophylactic use of quinine sulfate at least 2 hours prior to dialysis(Raymond, C.P et,al).

Arrhythmia Patients on maintenance hemodialysis are at risk of cardiac arrhythmias. They occur predominately in association with hemodialysis or may occur in the interdialytic period. Both acute and chronic alterations in fluid, electrolyte, and acid-base homeostasis may be arrhythmogenic in these patients. Hemolysis Hemolysis may result from a number of biochemical and toxic insults during the dialysis procedure. The half-life of red blood cells in renal failure patients is approximately one half to one third of normal and the cells are particularly susceptible to membrane injury(Raymond, C.P.,et,al) Hypoxemia A fall in arterial PO2 is a frequent complication of hemodialysis that occurs in nearly 90% of patients. The drop ranges from 5 to 35 mm Hg, and reaches its peak between 30 - 60 minutes after beginning dialysis. Patients on mechanical ventilators with constant minute volume and inspired oxygen concentration can still develop hypoxemia during hemodialysis(Mitch, W.E.,et,al). Ischemia of the index finger. Occasionally the arteriovenous fistula results in radial-to brachiocephalics teal, leave inadequate blood supply to the fingers. This risk is especially common in diabetic patients. Perforation of the bladder on insertion of peritoneal catheter. Bladder perforation can be a complication of blind insertion of a peritoneal catheter. It is recognized by the sudden appearance of glucose-positive “urine” on instillation of the first bag of dialysate. Instillation of radiographic contrast medium confirms the diagnosis. Tunnel abscess in patient undergoing continuous ambulatory peritoneal Dialysis 3

Pericatheter infections are a common source of peritonitis. Sometimes, the findings are more subtle than in this case. Prompt treatment with antibiotics is indicated. If the infection fails to respond, removal of the catheter is indicated2. Mitch, W.E., et,al). THE DIALYSIS DISEQUILIBRIUM SYNDROME (DDS) Dialysis disequilibrium syndrome is a central nervous system disorder developing in uremic patients, when treatment is started with rapid intensive hemodialysis and when there is a concomitant severe metabolic acidosis. The symptoms are attributed to cerebral edema, due to a brain-to-plasma urea gradient, caused by delayed urea diffusion from the brain to the blood. Addition of urea to the dialysate was shown to prevent the development of cerebral edema in rats, despite rapid dialysis. Classically, DDS arises in individuals starting hemodialysis due to chronic renal failure and is associated, in particular, with high solute removal dialysis. However, it may also arise in fast onset, i.e. acute, renal failure in certain conditions( Mitch, W.E.,et,al) DIAGNOSIS OF DIALYSIS DISEQUILIBRIUM SYNDROME Clinical signs of cerebral edema, such as focal neurological deficits, papilledema and decreased level of consciousness, if temporally associated with recent hemodialysis, suggest the diagnosis. A computed tomography of the head is typically done to rule-out other intracranial causes(Mitch, W.E et,al). TREATMENT OF DIALYSIS DISEQUILIBRIUM SYNDROME Dialysis must be discontinued until the seizure and vital signs have been stabilized. Antiepileptic drug (AED) therapy may help to reduce seizures. A drug not removed by dialysis should be selected. Most often, phenytoin is used. It is effective for tonic-clonic and partial seizures, and it can be given intravenously in loading doses to maintain a desired plasma concentration (e.g., after hemodialysis). Therapy begins with a loading dose of intravenous phenytoin. After dialysis, additional intravenous loading doses of phenytoin may be administered, if necessary. Hypocalcemic seizures may be controlled with calcium gluconate(Mitch, W.E.,. et,al) Avoidance is the primary treatment.DDS is a reason why hemodialysis initiation is usually done gradually, i.e. it is a reason the first few dialysis sessions are shorter than is typical in an end-stage renal disease patient. Rapid decrease of blood urea level during first conventional dialysis treatment with no change during second and third treatment using urea containing dialysate and progressive decline of metformin level during these treatments(. Mitch, W.E et,al),. 4

A prescription for dialysis by a nephrologist will specify various parameters for a dialysis treatment. These include frequency (how many treatments per week), 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 and potassium and bicarbonate levels. In general, the larger the body size of an individual, the more dialysis he/she will need(Mark, F.R.,et,al).

REFERENCES 1. Mark, F.R., Diaz-Buxo, B.V.M., Piraino, I.R., and Mohamed, K.O.2000. Dialysis disequilibrium syndrome Fundamentals: dialysis disequilibrium syndrome diagnosis and management.7th edition. Benjamin/ Cummings, New Zealand.Pp798-801. 2.

Mitch, W.E., and Villoca, G.H.2007.Dialysis: processes and treatment.5th edition.

Academic press, New York. Pp131-433. 3.

Raymond,

C.P.,

Krediete,

M.D.,

Salzer,

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Williams,P.Y.2003.Peritonial Dialysis Fundamentals: Peritoneal Health.9 edition. Parsons and sons. Russia. Pp 677-789. 4. Tolkoff-Rubin, N., Goldman, L., and Ausiello, D.2003.Treatment of renal failure.3rd edition. Saunders elsevier publishing, Philadelphia. Pp 55-133. 5

5. Zbylut, K.I., Twardowski, Y.U., and Crabtree, S.T.2005.Hemodialysis treatment and complications. 11th edition. Preston hall inc. California. Pp123-125.

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