1. Technical Aspects of Hemodialysis
Saramma Mathew, RN,BSN,CNN
Renal Educator
Hackensack University Medical Center, Hackensack, NJ

2. Anatomy Two Kidneys Two Ureters One bladder One Urethra
Kidneys: located in posterior abdominal wall in the retroperitoneal space. Right kidney is slightly lower than the left because the liver is above the right kidney. It is protected anteriorly by abdominal muscles fat, and intestine, posteriorly by large back muscles and ribs. Right kidney is also protected by liver and left kidney by spleen.
It weighs about gm It is a fist size.
Ureters: The main function of ureters are transport the urine from renal pelvis to the bladder. It is cm long2-8 mm diameter.
Bladder: it is pouch composed thick smooth muscle and lined with epithelial cells. Normal adult capacity is ml. Two ureters and one urethra opening in the bladder makes a triangular area called trigone.
Urethra; This is the opening to expel the urine out from the bladder. Male urethra is about 20cm long , female urethra is 3-5 cm long.

3. Nephron Nephron –functional unit of the kidney Filter the waste
Kidney has lot of blood vessels-capillaries
Nephron_ It is the functional unit of kidney. Each kidney has approximately 1 million Nephron. Each Nephron consists of two components, 1) Vascular component which include afferent arteriole, glomerulus efferent arterioles etc.
2) Tubular component- which includes Bowmwan’s capsule, Proximal tubule descending and ascending limbs of loop of Henle, distal tubule, etc.

4. Kidney Physiology Glomerulus- ball of capillaries Bowman’s capsule
Selectively permeable
Glomerular Filtration
Tubule
Glomerulus: Is a tangled ball of capillaries surrounded by a membrane called Bowman’s capsule. The capillaries walls that surround the Nephron are selectively permeable, which means they contain small pores that allow small substance to pass through while restricting the big substance such as blood cells and protein. Blood enters glomerulus from afferent arteriole( toward the organ) Small waste particles are able to pass through tiny pores in the glomeruli along with water forming a liquid called glomerular filtrate. If kidney’s filters are damaged, larger substances such as proteins can also pass through. This is why protein in the urine is signal of kidney damage. Coffe filter------
A normal adult makes about 180 liters of glomerular filtrate per day. Blood returns to the circulatory system by efferent arteriole ( away from the organ).
Tubule: Each glomerulus empties glomerular filtrate in to tubule .The tubule has 3 parts: Proximal convuluted tubule (near) loop of Henle, and distal convuluted tubule (far) The proximal and distal tubules are coiled and loop of henle is U-shaped. Tubules formed collecting ducts which empties urine to renal pelvis.

5. Functions of Kidneys Excretory Functions: Endocrine functions:
Gets rid of waste
Endocrine functions:
Hormones
EPO
Calcitriol
Another function related to bones. Healthy kidney convert Vitamin D in to active form called Calcitriol. This is necessary to absorb calcium from food and maintain a healthy bones. In renal failure, inability to make Calcitriol leads to calcium and phosphorus imbalance. Over time this imbalance can lead to enlargement of Parathyroid glands

6. Principles of dialysis
Solutions:
Solvent
Solute
Semi permeable membrane
Ultra filtration
Solution is the combination of solute and solvent. Solvent is the fluid and solute is any substance that can dissolve in the solvent. In salt water, water is the solvent and salt is the solute.
Dialysate is a solution in which water is the solvent and many dissolved substance such as electrolytes, glucose are the solute.
Semi permeable membrane: it is thin flexible filter . Think about the colander to strain the noodles. Water comes out but not the noodles. In dialysis, the semi permeable membrane’s holes or pores are small that only small molecules such as urea can pass through with water.
Ultra filtration: It is the movement of fluid through a filter as the result of mechanical (hydraulic ) pressure. In dialysis, ultra filtration- water removal from blood due to pressure gradient across membrane is used to remove excess water that has accumulated. The filter used in UF is a semi permeable membrane.

7. First Principle of HD - Diffusion
Solutes move from a region of higher concentration to a region of lower concentration until concentration is equal on either side.

8. Factors affecting diffusion
Concentration gradients:
Molecular weight of the solutes:
Temperature
Concentration gradients: how concentrated is the fluid on each side of the membrane? Solutes move through the semi permeable membrane from an area of greater concentration to an area of lesser concentration. Movement through the membrane can be either direction, but solute always move toward the area of lesser concentration until the solute concentration is equal on both sides.
Molecular weight: how large the dissolve particles? Smaller molecules diffuse more easily and quickly. Small molecule such as urea, salt and creatinine will pass fast. Big molecules such as Albumin, RBCs,WBC and some viruses are too big.
Temperature: how warm is the fluid? Molecules move at a higher temperature. As a result warmer temperature allows faster diffusion. That is why you get tea sooner if you put the tea bag in hot water instead of cold.

9. Factors affecting Diffusion
Membrane permeability:
Surface area of the membrane:
Flow geometry:
Membrane permeability: How big the pores are? Membrane with more pores allows faster diffusion. The membrane thickness and design also affect the diffusion.
Surface area of membrane: Surface area is the amount in direct contact with the blood and dialysate. Larger surface area allow more diffusion.
Flow geometry: How do the fluid flow? In dialysis blood flows one way while dialysate flows the opposite way. This is called counter current flow. This will speed up diffusion because it keeps the blood in constant contact with fresh dialysate.

10. 2nd Principle of HD - Osmosis
Osmosis is the movement of solvent through the semi permeable membrane from an area of lower concentration to an area of higher concentration.
Ultra filtration:
Osmosis: Osmosis is the movement of solvent through the semi permeable membrane from lower to higher. The difference in concentration is called osmotic pressure gradient. In both diffusion and osmosis, the end result is that movement continues until the concentration of molecules becomes equal on both sides of the membrane. Ultra filtration requires a mechanical force to move the fluid through the membrane. The dialysate machine can create a hydraulic pressure difference so that pressure is higher in the blood compartment than the dialysate compartment. This pressure is called TMP.
Filtration is the movement of fluid through a filter as the result of mechanical (hydraulic) pressure. Fluid will always moves from higher pressure to lower pressure. In dialysis- Ultra filtration- water removal from blood due to a pressure gradient across the membrane- is used to remove excess water that has accumulated. Filter is our semi permeable membrane.

11. Adequacy of Dialysis Formula for Urea Reduction Rate
Pre Dial BUN - Post Dial BUN
________________________ x100
Pre Dialysis BUN
= URR Calculation
Urea Reduction Rate: Urea is easily measured waste product of protein breakdown and is used to indicate treatment efficacy. BUN samples collected before treatment at the end of treatment. It is the simplest method for estimating adequacy .As per K/DOQI guidelines A URR of 65% or greater is the minimum level. URR does not provide all information needed to prescribe the treatment. It does not account how much more time or pts size or protein intake.

12. Adequacy - Kt/V K= Dialyzer clearance
T= Length of dialysis time (in minutes)
V= Urea distribution volume in millimeters.
Kt/V must be greater than 1.2

13. Adequacy UKM – Urea Kinetic Modeling Provides More Accuracy
Measures Protein levels
Urea Kinetic Modeling is more complicated than URR, it provides more information about pts dialysis need and it more accurate method.

14. Machine alarms PRIORITY ALARMS Air detector alarm Blood leak detector
Arterial pressure –high/low alarm
Venous pressure high/low alarm
Air detector alarm: detects the presence of air in the blood lines Blood leak detector: detects the presence of blood in used dialysate.
Arterial : A pre pump arterial pressure monitor measures pressure between the patient's vascular access.
Post pump –between the blood pump and dialyzer.
Venous: From the dialyzer to the pts venous puncture site.

15. Technical Complications
POTENTIAL PROBLEMS
Air in Bloodlines:
Blood loss:
Clotting in extracorporeal circuit.
Air in the bloodlines: Causes_ Under filling drip chamber, empty saline bag, Inadequate blood flow,
S&S: Air bubbles forming in the blood lines, alarm
Prevention: Maintain correct chamber levels. Ensure saline bags are not empty, Ensure all connections are secure, Tape needles securely, monitor pre pump arterial pressure.
Intervention: Correct the cause of air, remove the air from the tubing. Air detector alarm always armed.
Blood loss: Cause: Blood line separation or needle dislodge, Crack in the dialyzer, Rupture of aneurysm
S&S: Hypotension, Possible alarm, If venous needle, decrease venous pressure, if arterial needle dislodge, air detecto alarm.
Prevention: All connectors are secure, Tape needles Check extra corporeal circuit
Inter: Stop blood pump clamp blood lines. Apply pressure treat hypotension, administer oxygen, check H&H
Clotting in the extra- circuit: Inadequate anti coagulation therapy, low blood flow rate, increase hematocrit, Air in the system, pts have clotting disorder
S&S: Blood turning dark, clots in the chamber, poor dialyzer rinse back, If clotting in dialyzer, decrease venous pressure, if it is in the venous chamber, increase venous pressure.
Prev: Correct heparin, Maintain blood flow, Proper priming to remove air.
Interv: Fllow the unit protocol to remove the clotted component, return blood if possible.

16. Complications: POTENTIAL PROBLEMS
Dialyzer membrane leak:
Hemolysis:
Power failure:
Dialyzer leak: perforation of dialyzer membrane large enough to allow red blood cells to cross over membrane in to dialysate
S&S: Blood leak detector alarm, may see pink or red-tinged Prev: Do not use dialyzer that dropped,
Interv: Do not return the blood. Change dialyzer as per your unit protocol.
Hemolysis: (rupture of RBC) Cause: hypotonic dialysate, over heated dialysate, temperature monitor failure, too much of chloramine in the water, formaldehyde or bleach in dialysate or in reprocessed dialyzers.
S&S: cherry pop clour blood, chest pain, dyspnea, hypotension, pain and burning at the venous site, Dysrhythmias and cardiac arrest.
Preven: Complete and appropriate dialysate check. Regular preventive maintainnence, Pre-pump arterial pressure should go beyond <250
Intev: Discontinue dialysis, monitor v.s, administer oxygen, treat hypotension, check h&H and potassium level. Blood tranfusion if necessary.
Machine failure, Machine accidently unplug, power outage to area.
S&S: Everything stopped.
Prev: Complete preventive maintainaence.
Interv: Determine the cause and correct, Hand crack the blood.

17. Heparin – Purposes in HD
Function: to prevent clotting
Sensitivity:
Inadequate Heparin
During dialysis, blood comes in contact with artificial materials such as tubing and dialyzer. This will cause clotting heparin is given to prevent that
Sensitivity: If pts hav efever or infection, they required more heparin If they have thrombosis, need more heparin. If pts have hematuria, excessive bleeding or nose bleed, or pre or post op, adjust heparin.
Inadequate heparin: Clotting dialyzer, poor rinse back, reduce adequacy, H&H will be dropped.

18. Heparin Protocols Heparin free Strength of Heparin
Administering heparin:
Systemic
Continuous infusion
Intermittent
Low-dose “tight “ heparinization
Heparin Free: After surgery, bleeding.
Bolus heparin, saline flush, keep blood flow high.
Heparin: 1000 unit/cc can be given in several ways as per unit protocol. A loading dose can be givenafter both needles are in place, before treatment starts. This is called systemically heparinizing the pt. loading dose should be given 5 minutes prior to initiation of dialysis to ensure that the heparin has bound with protein in blood, especially when use high flux dialyzers.
Continuos: Heparin infusion pump connected to arterial blood line. Pump operates contionuosly Unit per hour. Pump will be shut off several minutes to hour prior to end of tx.
Intermittent: Initial dose is given, then heparin is injected during dialysis by single injection in to arterial line. Low dose: This is for pts with slight- to –moderate risk blleding After the loading dose, clotting time monitored q 30 mins and small additional dose can be given