DIALYSIS

A. ANATOMY & FUNCTION

Types of Dialysis

  • Hemodialysis

  • Peritoneal Dialysis

Kidney

  • Filters for the Blood ; removes excess fluid, minerals and wastes.

  • Maintain Electrolyte balance

  • Ensure Blood pH remains between 7.35-7.45

  • Produces hormones; erythropoietin makes blood healthy

When kidney fails:

  • Harmful wastes builds up in Body

  • BP may rise

  • Body may retain excess fluid and nit make enough RBCs

  • Treatment to replace the work of the Failed kidney may be needed (Dialysis)

B. DIALYSIS

Dialysis

  • Artificially removing fluid and waste products from the body, replacing the usual function of a kidney.

Goals of Dialysis

  • Removes metabolism end products (urea and creatinine) from blood

  • Maintain safe concentration of the serum electrolytes 

  • Corrections of acidosis and restoration of blood buffer system

  • Removal of excess fluid from the blood

Indications

  • Renal Failure, can no longer be managed through dietary modifications and medication administration.

  • Worsening of Uremic Syndrome, associated w/ ESRD (end stage renal disease) (Neurological changes, Pericarditis)

  • Severe Electrolyte and Fluid abnormalities, that cant be controlled by simple measures.

  • Dug and poison removal in acute situations 

3 Principles of Dialysis

  1. Diffusion

  • Movement of particles from an area to a lesser concentration 

  • Occurs in semipermeable membrane

  • Involves in the clearance of solute

  1. Osmosis

  • Involves movement of water across the semipermeable membrane

  • From a lesser concentrated area to greater concentration (osmolality) particles

  1. Ultrafiltration

  • involves movement of fluid across semipermeable membrane, as a result of an artificially created pressure gradient.

  • More efficient than osmosis for removal of fluid

Types of Dialysis 

  1. Peritoneal Dialysis

  • using the body’s peritoneal membrane (in abdomen), as a semipermeable membrane.

  • Solutions that removes toxins are put into abdomen via catheter

  • Solution remains in abdomen the in drained out

  • Performed daily and done in Home

  1. Hemodialysis 

  • works by circulating the blood through a dialyzer outside the body.

  • Blood flows across the dialyzer w/ solutions that helps removes toxins.

  • Typically done 3 times/week

  • Sessions last 3-4 hrs at a time

  • Done at a Dialysis Center

C. PERITONEAL DIALYSIS

  • more closely imitates function of the kidney than hemodialysis 

  • Easy to do

  • Slow process compared to hemodialysis 

  • Useful for pt w/ cardiovascular disease

  • Commonly prescribed to diabetic pts, insulin can be added to dialysate

  • Reduces risk of retinal haemorrhage

  • Treatment choice for childrens, does not interfere w/ growth

Peritoneal Membrane 

  • covers the abdominal cavity

  • Thin, translucent, tissue w/ numerous blood vessels

Peritoneal Cavity

  • space between the parietal membrane and visceral membrane (inner layer that covers organs).

  • can accommodate up to 5 Liters

  • 2-3 L volume during PD

Blood Vessels of the Peritoneum

  • mesenteric artery and peritoneal capillaries

Peritoneum

  • visceral layer covers organs

  • Parietal layer lines the wall of body cavity.

Retroperitoneal

  • area in the back of the abdomen or the peritoneum, posterior abdominal wall.

  • Kidneys and Pancreas, said to be retroperitoneal

Major Advantages:

  • Provides steady state of blood chemistry values

  • Can be easily taught, and can be performed alone in any loc.

  • Have few dietary restrictions

  • Can be used by pt who are hemodynamically unstable

Contraindications:

  • Hypercatabolism - adequate clearance of uremic toxins cannot be achieved with this method of dialysis

  • Adhesions and scarring - extensive surgical scars in the abdomen or any condition that prevents effective PD

  • Limited ability to care for self or lack of caregiving support at home

  • Inflammatory bowel disease or frequent bouts of diverticulitis, respiratory disease, recurrent peritonitis,

  • Abdominal malignancies, severe vascular disease, back problems, and obese

3 steps of PD (Peritoneal Dialysis)

“Fill,Dwell, and Drain” “Exchange”

  1. Infusing the dialysate into cavity

  2. Allow fluid to dwell in the cavity

  3. Drainage of the dialysate from the cavity

  • Before PD begins, Catheter is surgically inserted; about 3-5 cm below umbilicus

  • Dialysate may contain, sterile water, normal plasma, electrolytes and glucose - draws the waste fluid and waste products

  • Volume of dialysate used ranges from 1.5 - 3 qt.

  • Dialysate is left in cavity from 1-10 hrs, depending on time of dialysis

  • Dwell Time - period of time the dialysate is left in the abdominal cavity

PD works based on the principles of

• Osmotic pressure - moving of fluid toward the solution with higher solute concentration

• Diffusion - passing of particles from an area of high concentration to an area of low concentration

PD Preparation

  • Strict sterile technique when doing exchange

  • Dialysate should be warmed to 98.7 F or 37 C

  • Catheter tubing should be flushed

  • Aftercare: when not in use, clamp and tuck catheter under clothing

Diet for PD: Slighty diff from hemodialysis 

  • Limit salts and liquids

  • More protein 

  • Have diff restrictions on potassium

  • Cut back on number of calories

Medications Needed for PD

  • BP medications

  • Erythropoietin 

  • Calcium, Iron and other nutritional supplements 

  • Phosphate binders

  • Stool softener and laxative

Nursing Responsibilities 

  •  Keep dialysate (1-2 L of 1.5%, 2.5%, 4.25% glucose solution)

  • Allow to flow in by gravity

  • 5-10 min inflow time, close clamp immediately

  • 30 min of equilibrium (dwell time)

  • 10-30 min of drainage (clear yellow)

  • Continue for 24-48 exchanges

  • Monitor for complications: peritonitis, bleeding, respiratory difficulty, abdominal pain, bowel or bladder perforation

D. HEMODIALYSIS 

  • Removes toxic waste from the blood in renal failure

  • Requires blood flow of: 400-500 mL/min

  • Dialysis Access - is the special way of accessing the blood in the blood vessels.

  • Access can be temporary or permanent 

Indications

  • Temporary support for pt w/ acute reversible renal failure 

  • Regular long term tx of pt w/ CESR ( Chronic End Stage renal disease)

  • Acute poisoning : barbiturates or analgesic overdose

Dialysis Access

  • Temporary access 

  • Form of Dialysis catheter (large size) placed in veins

  • Used in Emergencies, short period

  • Permanent Access

  • Artery and Vein surgically joined

  • Allows vein to receive blood at high pressure

  • Arterialized Vein; sustains repeat puncture and provides excellent blood flow rates

Types of Access

  1. Fistula (AVF)

  • incision in wrist or lower forearm, small incision in side of artery and another one in vein. 

  • Opening; 3-7 mm long

  • Most effective and durable dialysis access

  • May take out: 6-12 weeks

  • Complications: Infection ate the site, clot formation (thrombosis)

  1. Graft (AVG) arteriovenous

  • Incision in forearm, upper arm or thighs

  • Synthetic or natural graft is tunnelled under skin and distal end is sutured

  • Used in pt w/ very small veins

  • Tube becomes artificial vein

  • Can be used for 1 week

  1. Arteriovenous shunt

  • incision in wrist, lower arm or Ankle

  • 6-10 inches of Transparent silastic cannula is inserted into artery and another in vein

  • Tunnelled out and joined w/ a teflon tubing in “U-shape”

  1. Venous Catheter

  • placed in a vein in neck, chest or groin

  • Not routinely used, can clog and infected easily

  • indications: if hemodialysis need to start right away, used while permanent access develops

Ex: Subclavian Vein Catheterization & Femoral Vein Catheterization

How Dialysis Works:

In dialysis, blood flows from the patient into an external dialyzer (artificial kidney) through an arterial access. Inside the dialyzer, blood and a fluid called dialysate move in opposite directions, separated by a semipermeable membrane.

The dialysate is similar to normal body fluid but with specific concentrations of electrolytes, bicarbonate, and glucose. Since the blood has higher concentrations of waste products and electrolytes, these diffuse across the membrane into the dialysate. Conversely, glucose and acetate in the dialysate diffuse into the blood.

Excess water is removed from the blood through ultrafiltration, using osmotic and hydrostatic pressure. The cleaned blood, free of impurities and excess water, then returns to the body through a venous site.

• Osmotic pressure - is the movement of water across the semipermeable membrane from an area of lesser solute concentration to one of greater solute concentration

• Hydrostatic pressure - forces water from the blood compartment into the dialysate compartment

When is Hemodialysis Started

Hemodialysis is often started when symptoms or complications of kidney failure develop. These include:

  1.  Signs of uremic syndrome - nausea, vomiting, loss of appetite, and fatigue

  2.  High levels of potassium in the blood (hyperkalemia)

  3. Too much fluid being absorbed in the blood (fluid overload)

  4. High levels of acid in the blood (acidosis)