Hemodialysis Devices
How well a dialyzer adsorbs depends on?
-What the membrane is made of -Surface area -How much protein has been adsorbed Less pores = clogging
What is the typical range in dialysate for magnesium?
0.5-1.0 mEq/L
What is the typical range in dialysate for potassium?
1 or 2 mEq/L
What are the 3 main ways to remove solutes that affect a dialyzer's clearance?
1) Diffusion 2) Convection 3) Adsorption
What are the 3 systems that ca monitor how well the dialyzer removes wastes, allowing the clinician to adjust the treatment to reach the patient's prescription?
1) Fresenius Med Care 2) B Braun 3) Gambro
What points is checked for conductivity?
1. Dialysate mixing 2. Before dialysate enters the dialyzer
How can heparin be administered?
1. Intermittently 2. By bolus 3. By continusous infusion Must be stopped before the end of treatment so blood clotting can go backto normal.
What are the important functions of the dialysis machines?
1. Mix and monitors dialysate 2. Pumps and monitors the patient's blood 3. Has alarms to protect the patient's safety
What are the ways that concentrates reach the machine?
1. Prepared liquid concentrate in single "car-boy" jugs is connected to concentrate input lines on the machine. 2. Prepared liquid concentrate comes from central concentrate delivery system with delivery ports near each station. We connect the concentrate input line to a concentrate port at the station. 3. Dry concentrates may be used. In this case, a container of dialysate powder is mounted on the machine. A hydraulic path adds water into the container to make a liquid, then draws off the new concentrate to be made into dialysate.
Solve this problem: The patient is using a dialyzer with a KUF of 10. The dialysis machine's TMP reads 100 mmHg. How much would the patient lose per hour of treatment?
10 mL/hr/mmHg x 100 mmHg = 1000 mL/hr
What is the typical range in dialysate for chloride?
100-105 mEq/L
What is the typical range in dialysate for glucose?
100-200 mEq/L
What is the molecular weight of Creatine?
113
What is the typical range in dialysate for sodium?
139-144 mEq/L
What is the molecular weight of H2O?
18
How many timers are on the dialysis machine? & what are they?
2. UF time and RTD
What is the typical range in dialysate for citrate?
2.4 mEq/L
What is the typical range in dialysate for acetate?
2.4-4 mEq/L
What is the typical range in dialysate for calcium?
2.5-3.5 mEq/L
How long does blood stay in the dialyzer at a 400 bfr?
20 seconds
What is the typical range in dialysate for bicarb?
33-38 mEq/L
What is the molecular weight of Calcium?
40
Gage 15
450
What is the molecular weight of Urea?
60
What is the molecular weight of Nitric Oxide?
62
What is the molecular weight of Zinc?
65.3
What is the molecular weight of albumin?
66,000
What is the molecular weight of Phosphate?
94.9
What is a transducer?
A device in the machine that turns air pressure into an electronic signal.
What is the capillary refill rate?
About 400 mL/hr
What is in dialysate?
Acid concetrate, bicarbonate concentrate, & treated water.
What alarms stop the blood pump?
All of them.
What is heparin?
An anticoagulant that is used to prevent clotting in the extracorporeal blood circuit.
What alarms are set off by blood clots?
Arterial and venous alarms
How is clearance of a solute checked (in terms of dialyzer clearance)?
By drawing samples of a patient's blood going intoandout of the dialyzer.
What are transducer protectors?
Caps with filters that go between blood in the tubing and the transducer. They connect to the machine's venous and/or arterialports via a small tubing segmenton top of the drip chamber.
What is the importance of chloride?
Chloride level in dialysate depends on the contents of chemicals such as sodium chloride, potassium chloride, magnesium chloride, and calcium chloride. Dialysate chloride ranges from 100-105 mEq/L. Normal plasma chloride levels are 95-110 mEq/L.
How do we measure dialyzer effectiveness?
Clearance (K) is the amount of blood (in mL) that is completely cleared of a certain solute in one minute of treatment at a given blood flow rate (Qb) & dialysate flow rate (Qd). BFR & dialysate flow rate, the faster they are, the better the clearace
What is significant of the bypass mode?
High/low conductivity High/low temperature Blood leak alarm can trigger the delivery siystem to switch into bypass mode Only conductivity and temperature
What is surface area?
How large the membrane is.It can range from 0.5 to 2.5 square meters. The more surface area exposed, the moreblood to dialysate, the more solutes are removed.
What does biocompatibility mean?
How much a membrane is like the human body.
What is the Ultrafiltration Coefficients?
How much water will be removed. A dialyzer with Kuf of 10 removes 10 ml of water per hour for each mmHg of TMP. This is stated as ml/mmHg/Hr. Dialyzer Kufis 10. TMP is 10 x 100 = 1000. So the total fluid loss per hour is 1000 ml.
What are modified cellulose membranes?
In the 1970's, the membranes were chemically changed to make it more biocompatible. They use convection,diffusion, and adsorption to remove solutes. They clear solutes up to 15000 Da & are able to clear B2M w/ 18,5000 Da.
What is the disadvantage of sodium modeling?
It can cause thirst, weight gain, and high bp between dialysis. Many clinics no longer use modeling for this reason.
What is the importance of Glucose?
It can prevent loss of blood glucose and reduce catabolism in dialysate. Glucose calories can help patients who have diabetes or are malnourished. Dialysate glucose levels range from 100-200mg/dL. Fasting blood glucose levels are 65-115 mg/dL. It can also give dialysate an osmotic effect aiding in UF.
What is the importance of Na+?
It is a major electrolyte of the blood plasma and interstitial water. It causes water to move across cell membranes in the body. Normal range in the blood is 135-147mEz/L. In dialysate, it is 139-144 mEq/L.
What is the significance of pH?
It is a measure of how acidic or alkaline a solution is. Liquid pH is based on how many acid ions or base ions it has.
What is the importance of Calcium?
It is found in the body both inside and outside of cells. It builds bones and teeth, helps muscles move, aids in bloodclotting, nd helps send nerve signals. Normal range in blood plasma is 8.6-10.3 mg/dL (4.4-5.1 mg/dL when ionized). Dialysate calciumis most often in the rangefrom 2.5-3.5 mEq/L.
What is sorbent dialysis?
It is hemodialysis that takes as little as 6 litersof tap water for treatment. It goes through a sorbent cartridge and is reused. They can be used in a wide range of environments: -acute dialysis in critical care units -homehd -disaster relief -rehab centers and nursing homes -remote locationsand on vacation
What is the importance of Flow Rate?
It is prescribed. The higher the flow,the better the dialyzer efficiency
What is the importance of Magnesium?
It is vital to nerves and muscles as well as triggers enzymes that are key to carbohydrate use. Is found in the plasma at levels from 1.3-2.2 mEq/L. The range in dialysateis 0.5-1.0 mEq/L.
What happens to acetate after an hour and a half of treatment?
It metabolizes in the liver and then turns into bicarb.
What is the importance of a Blood leak detector?
It prevents major blood loss and contaminationby the non-sterile dialysate. It is used to check for blood in the used dialysate by shining a light through the used dialysate and onto a photocell. Since dialysate is clear, the light can pass through. Even a tiny amount of blood will break the light beam.
What is KoA?
Mass Transfer Coefficient. Ko (membrane clearance) x A (surface area) = KoA Mass transfer coefficient measures how well a given solute will pass through a membrane.It is the highest possible clearance of that solute through a membrane at certain and dialysate flow rates. A higher KoA means a more permeable membrane.
What is a disadvantage of adsorption?
More proteins become attached to the membrane and clog the pores.
Is the dialysate sterile?
No.
What does the acid concentrate consist of?
Precise amounts of: -sodium chloride, potassium chloride,magnesium chloride, calcium chloride,glucose, and an acidifier (acetic/citric acid used to lower the pH of the final dialysate)
What is significant about pyrogen filters?
Pyrogens are parts of bacteria that can cause fever in patients. A machine option that can help keep bacteria out of the ddialysate path.
What does hydrophobic mean?
Repel water
What is in the bicarbonate concentrate?
Sodium bicarb or sodium chloride. This concentrate is considered alkaline.
What is the major electrolyte of the blood plasma and interstitial (in between cells) water?
Sodium. It causes water to move across cell membranes in the body. This way, water shifts from inside cells to in between cells to the bloodstream.
What is convection?
Solvent drag.It is the best way to remove large solutes. HD in the US uses only a small amount of convection.
What characteristic of the dialyzer is fixed?
Surface area
What is clearance?
The amount of blood that can be cleared ofa solute in a given time is K (clearance). The more hole/fiber/pores = the better.
What is diffusion?
The best way to remove small-low molecular weight-solutes.
What is the importance of Potassium?
The body uses precise amounts of K+ on both sides of cell membranes to send nerve signals. We add it to dialysate to bring the patient to a normal plasma level: from 3.5-5.0 mEq/L. It is most often fixed at 1 or2 mEq/L.
How is the dialyzer similar to a nephron?
The dialyzer membrane is selective. It allows only certain solutes and water to pass through. Large substances, like protein and blood cells, won't fit through the small pores.
What is Mass Transfer Coefficient?
The highest possible clearance of that solute through a membrane at certain blood and dialysate flow rates. Ko (membrane clearance
Gage 14
The max if 450
What is molecular weight cut off?
The solute size that can pass through the membrane. It is measured in Da. Larger molecules = higher molecular weights & smallermolecules = lower ones
What is significant about synthetic membranes?
They are more biocompatible than cellulose membranes. Their fibers are hydrophobic, allowing them to better to adsorb blood proteins.
What is an air detector?
They checkall of the blood in thevenous tubing segment for air and foam. The systemmay check forair at the venous drip chamber or at the blood tubing below it.
Why is temperature significant in the monitoring system?
Too hot dialysate can burst the patient's blood cells which is called hemolysis. Too cold can make the patient feel cold therefore causing less diffusion. Dialysate is kept in the range of 35-38 degrees C.
What is osmolality?
Total solute level. It must closely match the blood. This way, it keeps too much water from moving across the membrane.
True or false? Solutes are removed by diffusion, adsorption, and a bit of convection. Clearance of solutes depends mainly on UF rates.
True
What is adsorption?
When proteins stick to the membrane. It is useful because the protein keeps the foreign membrane away from the blood. But,protein on the membrane may also prevent some diffusion and convection.
When does the RTD timer stop?
When the acetate and bicarbonate (conductivity) is low, then the bypass alarms.
How well a membrane adsorbs proteins is key to what?
Whether the membrane is biocompatible.
Is dialysate prescribed?
Yes by the doctor.
Are synthetic membranes effective?
Yes. They remove solutes up to 15,000 Da, so they clear someB2M (11,800 Da).
What does the extracorpporeal circuit consist of?
-Arterial and venous blood tubin -Heparin pumps -Dialyzer -Venous line clamp -Blood flow monitors
What are the characteristics of the dialyzer?
-Biocompatibility -Membrane Surface area -Molecular weight cutoff -Ultrafiltration coefficient -Mass transfer coefficient -Clearance
What does diffusion rate depend on?
-Blood and dialysate flow rate -Membrane suface area and thickness -Solution temperature -Membrane resistance -Concentration gradient -Size, weight, and charge of the solutes
What are the different membrane materials?
-Cellulose -Modified Cellulose -Synthetic
What does convective clearance depend on?
-Molecular weight cutoff of the membrane -Membrane surface area -UFR
Convective clearance depends on?
-Molecular weight cutoff of the membrane -Membrane surface area -Ultrafiltration rate (UFR)
What kind of polymers make up synthetic membranes?
-Polycarbonate -Polyacrylonitrile (PAN) -Polysulfone (PSF) -Polyethersulfone (PES) -Polymethylmethacrylate (PMMA)
