This document summarizes treatment modalities for the renal system, focusing on dialysis. It describes the two main types of dialysis: peritoneal dialysis (PD) and hemodialysis (HD). For PD, it outlines the process of catheter placement in the peritoneum and how cycles of fluid exchange occur across the peritoneal membrane. For HD, it describes how blood is pumped through an external dialyzer to remove waste via diffusion, osmosis, and ultrafiltration across a semi-permeable membrane. Complications of each method are also summarized.
3. “Dialysis is the movement of fluid and molecules across a semipermeable membrane from one
compartment to another. “
Dialysis is a technique in which substances move from the blood through a
semipermeable membrane and into a dialysis solution (dialysate).
It is used to correct fluid and electrolyte imbalances and to remove waste
in renal failure.
The two methods of dialysis available are Peritoneal dialysis (PD) and
Hemodialysis (HD).
In PD the peritoneal membrane acts as the semipermeable membrane.
In HD an artificial membrane (usually made of cellulose-based or synthetic
materials) is used as the semipermeable membrane and is in contact with the
patient's blood.
4. Indication
Dialysis is begun when the patient's uremia can no longer be adequately managed
conservatively.
Generally dialysis is initiated when the GFR is less than 15 ml/min.
This can vary widely in different clinical situations, and based on the patient's
clinical status.
Certain uremic complications, including
Uremic Encephalopathy
Peripheral Neuropathies
Uncontrolled hyperkalemia
Pericarditis
Accelerated hypertension, indicate a need for immediate dialysis.
5. Principles of Dialysis
The principles of diffusion, osmosis, and ultrafiltration are involved in dialysis
Diffusion:
It is the movement of solutes from an area of greater concentration to an area of lesser
concentration.
In renal failure, urea, creatinine, uric acid, and electrolytes (potassium, phosphate) move from the
blood to the dialysate with the net effect of lowering their concentration in the blood.
Osmosis
It is the movement of fluid from an area of lesser to an area of greater concentration of solutes.
Glucose is added to the dialysate and creates an osmotic gradient across the membrane, pulling
excess fluid from the blood.
6. Ultrafiltration (water and fluid removal) :
It results when there is an osmotic gradient or pressure gradient across the membrane.
In PD, excess fluid is removed by increasing the osmolality of the dialysate (osmotic gradient)
the addition of glucose.
In HD, the gradient is created by increasing pressure in the blood compartment (positive
or decreasing pressure in the dialysate compartment (negative pressure).
Extracellular fluid moves into the dialysate because of the pressure gradient.
The excess fluid is removed by creating a pressure differential between the blood and the
solution with a combination of positive pressure in the blood compartment or negative pressure
the dialysate compartment.
8. The prototype of the catheter that is used was developed by Tenckhoff in 1968 and
is made of silicone rubber tubing.
The catheters are about 60 cm long and have two Dacron cuffs on the
subcutaneous and peritoneal portions of the catheter that act as anchors and
prevent the migration of microorganisms down the shaft from the skin.
Within a few weeks, fibrous tissue grows into the Dacron cuff, holding the catheter
in place and preventing bacterial penetration into the peritoneal cavity.
The tip of the catheter rests in the peritoneal cavity and has many perforations
spaced along the distal end of the tubing to allow fluid to flow in and out of the
catheter.
9.
10.
11. The technique for catheter placement varies.
Although it is possible to place a permanent catheter in the peritoneal cavity at the bedside with a
trocar, it is usually done via surgery so that its placement can be directly visualized, minimizing
potential complications.
Preparation of the patient for catheter insertion includes emptying the bladder and bowel,
weighing the patient, and obtaining a signed consent form.
12. In the nonsurgical (bedside) approach, an area approximately 2 cm below the umbilicus is numbed with a
local anesthetic, and a small stab wound is made.
A stylet is inserted, and the abdomen is distended with dialysis solution.
The catheter is then placed into the peritoneal cavity.
When the patient feels pressure in the rectal area and has the urge to defecate, the catheter is in place.
In the surgical approach, a midline umbilical incision is made, and a small puncture is made to one side of
and below this incision.
The distal end of the catheter is placed in the peritoneum, and it is tunneled under the skin to the
puncture site.
The tunnel helps prevent peritonitis.
After the catheter is inserted, the skin is cleaned with an antiseptic solution, and a sterile dressing is
applied.
13. The catheter is connected to a sterile tubing system and secured to the abdomen with tape.
The catheter is irrigated immediately with heparinized dialysate (usually 500 ml) to clear blood from
it.
Prophylactic antibiotics may also be instilled.
The irrigations may continue for 12 to 24 hours using small volumes of dialysate.
This procedure helps prevent catheter occlusion that can lead to poor drainage and inflow.
The patient needs instructions on keeping the dressing dry, avoiding accidentally pulling the
catheter, and receiving follow-up care.
Before the start of PD, it is preferable to allow a waiting period of 7 to 14 days for proper sealing of
the catheter and for tissue to grow into the cuffs.
However, some centers start dialysis 5 to 7 days after catheter insertion.
About 2 to 4 weeks after catheter implantation, the exit site should be clean, dry, and free of redness
and tenderness
14. Dialysis Solutions and Cycles
Dialysis solutions are available commercially in 1- or 2-L with glucose concentrations of 1.5%, 2.5%, and
4.25%.
The electrolyte composition is similar to that of plasma. Using dry heat, the dialysis solution is warmed to
body temperature to increase peritoneal clearance, prevent hypothermia, and enhance comfort.
The three phases of the PD cycle are
Inflow (fill),
Dwell (equilibration)
Drain.
The three phases are called an exchange.
The patient dialyzing at home will receive about four exchanges per day.
An acutely ill hospitalized patient may receive 12 to 24 exchanges per day.
During inflow, a prescribed amount of solution, usually 2 L, is infused through an established catheter over
about 10 minutes.
The flow rate may be decreased if the patient has pain.
After the solution has been infused, the inflow clamp is closed before air enters the tubing.
15. Next part of the cycle is the dwell phase, or equilibration, during which diffusion and osmosis occur
between the patient's blood and the peritoneal cavity.
The duration of the dwell time can last 20 to 30 minutes to 8 or more hours, depending on the
method of PD.
Drain time takes 15 to 30 minutes and may be facilitated by gently massaging the abdomen or
changing position.
The cycle starts again with the infusion of another 2 L of solution.
16. Peritoneal Dialysis Systems
Two types of PD currently being used are automated peritoneal dialysis (APD) and continuous
ambulatory peritoneal dialysis (CAPD).
Automated Peritoneal Dialysis.
An automated device called a cycler is used to deliver the dialysate for APD.
The automated cycler times and controls the fill, dwell, and drain phases.
The machine cycles four or more exchanges per night with 1 to 2 hours per exchange.
Alarms and monitors are built into the system to make it safe for the patient to dialyze while
sleeping.
17.
18. Continuous Ambulatory Peritoneal Dialysis
CAPD is carried out manually by exchanging 1.5 to 3 L (usually 2 L) of peritoneal dialysate at least 4
times daily, with dwell times of 4 to 10 hours.
For example, one schedule starts the exchanges at 7 am, 12 noon, 5 pm, and 10 pm.
In this procedure the person instills 2 L of dialysate from a collapsible plastic bag into the peritoneal
cavity through a disposable plastic tube.
Technical advances in CAPD systems allow the bag and line to be disconnected after the instillation
of the fluid, decreasing the risk of peritonitis.
After the equilibration period, the line is reconnected to the catheter, the dialysate is drained from
the peritoneal cavity, and a new 2-L bag of dialysate solution is infused.
It is critical in PD to maintain aseptic technique to avoid peritonitis.
Several tubing connections and devices are commercially available to help maintain an aseptic
system.
19. Complications of Peritoneal Dialysis
Exit Site Infection
Peritonitis.
Abdominal Pain.
Outflow Problems
Hernias
Lower Back Problems: Increased intraabdominal pressure can cause or aggravate lower back pain.
Bleeding
Pulmonary Complications
Protein Loss: The peritoneal membrane is permeable to plasma proteins, amino acids, and
polypeptides. These substances are lost in the dialysate fluid. The amount of loss may be as much as
5 to 15 g/day.
20. Carbohydrate and Lipid Abnormalities :
Dialysate glucose is absorbed via the peritoneum and may be as much as 100 to 150 g/day.
Continuous absorption of glucose results in increased insulin secretion and increased plasma insulin
levels.
The hyperinsulinemia stimulates hepatic production of triglycerides.
Encapsulating Sclerosing Peritonitis and Loss of Ultrafiltration: Encapsulating
sclerosing peritonitis is a term applied to the development of a thick fibrous
membrane that surrounds and compresses the bowel for unknown reasons.
22. In 1943, Willem Kolff in the Netherlands performed the first successful dialysis on a human using a
rotating-drum dialyzer.
He initiated dialysis treatment in the United States in 1948.
Tremendous technologic advances have been made in HD since then, allowing for safer, shorter
treatments using sophisticated equipment.
23. Vascular Access Sites
Obtaining vascular access is one of the most difficult problems associated with HD.
To carry out HD, a very rapid blood flow is required, and access to a large blood vessel is essential.
The types of vascular access in current use include arteriovenous fistulas (AVFs) and grafts (AVGs),
temporary and semipermanent catheters, subcutaneous ports, and shunts.
24. Internal Arteriovenous Fistulas and Grafts
In 1966 the was introduced.
An AVF is created most common use of the subcutaneous internal arteriovenous native (using the
person's own blood vessels) fistula only in the forearm with an anastomosis between an artery (usually
radial or ulnar) and a vein (usually cephalic).
The fistula provides for arterial blood flow through the vein.
The arterial blood flow is essential to provide the rapid blood flow required for HD.
The increased pressure of the arterial blood flow through the vein makes the vein dilate and become
tough, making it amenable to repeated venipuncture in approximately 4 to 6 weeks, although it is
recommended that the AVF be placed at least 3 months prior to the initiation of hemodialysis.
The vein is accessed using two large-gauge needles.
25. Native fistulas have the best overall patency rates and least number of complications (e.g.,
thrombosis, infections) of all vascular accesses.
Several reasons have been identified for the infrequent placement of AVFs, including late referrals;
lack of surgical expertise; less surgery reimbursement, although the procedure is more complicated
and time consuming than the placement of a graft.
However, AVFs may not be possible in patients with a history of severe hypertension, peripheral
vascular disease, diabetes, prolonged IV drug use, or previous multiple IV procedures in the forearm.
For these individuals a synthetic graft is usually required.
26. Arteriovenous grafts
Arteriovenous grafts (AVGs) are made of synthetic materials (polytetrafluoroethylene [PTFE], Teflon)
and form a “bridge” between the arterial and venous blood supplies.
Grafts are placed under the skin and are surgically anastomosed between an artery (usually
and a vein (usually antecubital).
An interval of 2 to 4 weeks is usually necessary to allow the graft to heal, but some centers may use
earlier.
The graft is accessed using two large-gauge needles and the graft material is self-healing, closing
over puncture sites with sufficient pressure to also stop the bleeding when needles are removed.
27. The needles used are 14 to 16 gauge and are inserted into the fistula or graft to obtain vascular
access.
One needle is placed to pull blood from the circulation to the HD machine, and the other needle is
used to return the dialyzed blood to the patient.
The needles are attached via tubing to dialysis lines.
Normally, a thrill can be felt by palpating the area of anastomosis, and a bruit can be heard with
a stethoscope.
The bruit and thrill are created by arterial blood rushing into the vein.
29. The dialyzer is a long plastic cartridge that contains thousands of parallel hollow tubes or fibers.
The fibers are the semipermeable membrane made of cellulose-based or other synthetic materials.
The blood is pumped into the top of the cartridge and is dispersed into all of the fibers.
Dialysis fluid (dialysate) is pumped into the bottom of the cartridge and bathes the outside of the
fibers with dialysis fluid.
Ultrafiltration, diffusion, and osmosis occur across the pores of this semipermeable membrane.
When the dialyzed blood reaches the end of the thousands of semipermeable fibers, it converges
into a single tube that returns it to the patient.
30. Procedure
To initiate chronic dialysis in a patient with an AVG or AVF, two needles are placed in the fistula or
graft.
If the patient has a catheter, the two blood lines are attached to the two catheter lumens.
The needle closer to the fistula or the red catheter lumen is used to pull blood from the patient
and send it to the dialyzer with the assistance of a blood pump.
The dialyzer and blood lines are usually primed with up to 1000 ml of saline solution to eliminate
air from the system.
Heparin is added to the blood as it flows into the dialyzer because any time blood contacts a
foreign substance, it has a tendency to clot.
When the blood enters the extracorporeal circuit, it is propelled through the top of the dialyzer by
a blood pump at a flow rate of 200 to 500 ml/min, while the dialysate (warmed to body
temperature) circulates in the opposite direction at a rate of 300 to 900 ml/min.
Blood is returned from the dialyzer to the patient through the second needle or blue catheter
lumen.
34. 1. Hypotension:
It occurs during HD primarily results from rapid removal of vascular volume (hypovolemia),
decreased cardiac output, and decreased systemic intravascular resistance.
The drop in BP during dialysis may precipitate light-headedness, nausea, vomiting, seizures, vision
changes, and chest pain from cardiac ischemia.
The usual treatment for hypotension includes decreasing the volume of fluid being removed and
infusion of 0.9% saline solution (100 to 300 ml).
If a patient experiences recurrent hypotensive episodes, a reassessment may have to be done of dry
weight and BP drugs.
BP drugs should be held before dialysis if there are frequent episodes of hypotension during dialysis.
35. 2. Muscle Cramps.
Painful muscle cramps are a common problem.
They result from rapid removal of sodium and water or from neuromuscular hypersensitivity.
Treatment includes reducing the ultrafiltration rate and infusing hypertonic saline or a normal saline
bolus.
36. 3. Loss of Blood.
Blood loss may result from
Blood not being completely rinsed from the dialyzer,
Accidental separation of blood tubing,
Dialysis membrane rupture,
Or bleeding after the removal of needles at the end of dialysis.
If a patient has received too much heparin or has clotting problems, there can be significant
postdialysis bleeding.
It is essential to rinse back all blood, to closely monitor heparinization to avoid excess
anticoagulation, and to hold firm pressure on access sites until the risk of bleeding has passed.
37. 4. Hepatitis.
The causes of hepatitis B and C in dialysis patients include blood transfusions or the lack of
adherence to precautions used to prevent the spread of infection.
As blood is now screened for hepatitis B and C, blood is an unlikely source of infection.
The incidence of hepatitis B has decreased with frequent testing for hepatitis B surface antigen in
patients, isolation of dialysis patients who are positive for hepatitis B, the use of disposable
equipment, the hepatitis B vaccine, and infection control precautions.
All patients and personnel in dialysis units should receive hepatitis B vaccine.
38. 5. Sepsis.
Sepsis is most often related to infections of vascular access sites.
Bacteria can also be introduced during the dialysis treatment as a result of poor technique or
interruption of blood tubing or dialyzer membranes.
Bacterial endocarditis can occur because of the frequent and prolonged access to the vascular
system.
Aseptic technique is essential to prevent this problem.
Nurses must monitor patients for signs and symptoms of sepsis such as fever, hypotension, and an
elevated WBC.
39. 6. Disequilibrium Syndrome.
Disequilibrium syndrome develops as a result of very rapid changes in the composition of the
extracellular fluid.
Urea, sodium, and other solutes are removed more rapidly from the blood than from the
cerebrospinal fluid and the brain.
This creates a high osmotic gradient in the brain resulting in the shift of fluid into the brain, causing
cerebral edema.
Manifestations include nausea, vomiting, confusion, restlessness, headaches, twitching and jerking,
and seizures.
The rapid changes in osmolality may cause muscle cramps and worsen hypotension.
Treatment consists of slowing or stopping dialysis and infusing hypertonic saline solution, albumin,
or mannitol to draw fluid from the brain cells back into the systemic circulation.
It is more commonly observed in the initial treatment of the patient when the BUN level is high.
First dialysis treatment sessions are purposely short with limited total solute removal to prevent this
rare syndrome.
41. Continuous renal replacement therapy (CRRT) is an alternative method for treating ARF.
It provides a means by which uremic toxins and fluids are removed, while acid-base status and
are adjusted slowly and continuously from a hemodynamically unstable patient.
The patients selected are usually those who do not respond to dietary interventions and
agents.
CRRT is contraindicated if a patient has life-threatening manifestations of uremia (hyperkalemia,
pericarditis) that require rapid resolution.
Various types of CRRT are available, differentiated by whether arterial and/or venous access is required
and if a blood pump is needed.
Due to technologic advances with automated and volumetric equipment that includes a blood pump,
CRRT most commonly uses the venovenous approaches of continuous venovenous hemofiltration
and continuous venovenous hemodialysis (CVVHD).
42. Several features of CRRT differ from HD
It is continuous rather than intermittent. Large volumes of fluid can be removed over days (24 hours
to >2 weeks).
Solute removal can occur by convection (no dialysate required) in addition to osmosis and diffusion.
It causes less hemodynamic instability (e.g., hypotension).
It does not require constant monitoring by a specialized HD nurse but does require a trained
intensive care unit (ICU) nurse.
It does not require complicated HD equipment, but a blood pump is needed for venovenous
therapies.
43. Vascular access for CVVH or CVVHD is achieved through the use of a double-lumen catheter
placed in the femoral, jugular, or subclavian vein.
A highly permeable, hollow fiber hemofilter removes plasma water and nonprotein solutes, which
are collectively termed ultrafiltrate.
The ultrafiltration rate (UFR) may range from 0 to 500 ml/hr.
Under the influence of hydrostatic pressure and osmotic pressure, water and nonprotein solutes
pass out of the filter into the extracapillary space and drain through the ultrafiltrate port into a
collection device.
The remaining fluid continues through the filter and returns to the patient via the return port of
the double-lumen catheter.
44. Types of CRRT
Therapies Abbreviation Purpose
Venous Access
Therapies
Continuous venovenous ultrafiltration CVVU Solute loss via convection
Continuous venovenous hemofiltration CVVH CVVH
Solute loss via convection; hemodilution
using replacement fluid
Continuous venovenous hemodialysis CVVHD Solute loss via convection and diffusion
45. Arterial Access Therapies (Arteriovenous [AV])
Slow continuous ultrafiltration SCUF Fluid removal via ultrafiltration
Continuous arteriovenous
hemofiltration CAVH
Ultrafiltration and convective losses
occur; replacement fluid used
Continuous arteriovenous
hemodialysis
CAVHD Fluid removal via ultrafiltration and
osmosis
46. Ultrafiltration therapies (SCUF and CVVU) :
These are strictly for ultrafiltration or fluid removal.
There is some convective loss of solutes, but no diffusion or osmosis is involved
Hemofiltration therapies (CAVH and CVVH):
It involve the introduction of replacement fluids.
Large volumes of fluid may be removed hourly (200 to 800 ml), and then a portion of this fluid is
replaced.
The type of fluid replacement is dependent on the stability and individualized needs of the patient.
Ultrafiltration and convective losses occur, and solute concentrations in the blood are diluted with
the replacement fluid.
47. The hemodialysis therapies (CAVHD and CVVHD) use dialysate.
Peritoneal dialysate bags are attached to the distal end of the hemofilter, and the fluid is pumped
countercurrent to the blood flow .
As in dialysis, diffusion of solutes and ultrafiltration via hydrostatic pressure and osmosis occur.
This is an ideal treatment for a patient who needs both fluid and solute control but cannot tolerate
the rapid fluid shifts associated with HD.
48. CRRT can be continued as long as 30 to 40 days, but the hemofilter should be changed every 24 to
48 hours because of loss of filtration efficiency or potential for clotting.
The ultrafiltrate should be clear yellow, and specimens may be obtained for evaluation of serum
chemistries.
If the ultrafiltrate becomes bloody or blood tinged, a possible rupture in the filter membrane
should be suspected, and treatment suspended immediately to prevent blood loss and infection
49. The nurse responsible for the care of the patient with ARF who is receiving CRRT may be a critical
care nurse or a nephrology nurse specialist, working in collaboration with other health care
providers.
Specific nursing interventions include obtaining weights and monitoring and documenting
laboratory values daily to ensure adequate fluid and electrolyte balance.
Hourly intake/output measurements, vital signs, and hemodynamic status are essential.
Although reductions in central venous pressure and pulmonary artery pressure are expected, there
should be little change in mean arterial pressure or cardiac output.
Patency of the CRRT system is assessed and maintained, and the patient's vascular access site is
cared for to prevent infection.
Treatment is discontinued and the needle(s) removed once the patient's ARF is resolved or there is
a decision to withdraw treatment due to patient deterioration.
