dialysis Flashcards
what is dialysis
It is a process for removing waste products such as creatinine, urea, water plus excess water and minerals from the blood
how is it an artificial replacement?
cannot secrete hormones. artificial replacement for patients who have temporary or permanent lost kidney function due to renal failure
dialyser
describe haemodialysis
patient is connected to a dialysis machine to create a haemodialysis circuit
The patient’s blood is pumped through a dialyser within the circuit
The dialyser is composed of thousands of hollow synthetic fibres which act as a semi-permeable membrane
Blood flows through the fibres and the dialysis solution flows outside the fibres in the opposite direction
what diffuses in and out of the blood/dialysis solution?
Water, waste products and excess electrolytes move from the blood into the dialysis solution via diffusion
Essential nutrients from the dialysis solution enter the blood via diffusion e.g. sodium bicarbonate
The movement of solute across the semipermeable membrane is along a concentration gradient – from a high to low concentration
The filtered blood then re-enters the bloodstream
describe haemofiltration
The blood is pumped through a dialyser as in dialysis
However a negative pressure is applied to the dialysate causing solutes to move across a pressure gradient, as opposed to diffusion
More aggressive than HD and allows removal of several litres of water and more solutes from the blood
describe haemodiafiltration
Combination of haemodialysis and haemofiltration i.e. solutes move across the semi-permeable membrane via diffusion and along a pressure gradient
Compared with HD, HDF removes middle-molecular-weight solutes so increases the clearance of larger toxins
HDF: combination of HD and HF – both diffusion AND pressure gradient.
how can we get access to the patients’ blood supply allow connection to the dialysis machine
- Arteriovenous (AV) fistula
- Arteriovenous (AV) graft
- Central venous catheter (CVC)
Arteriovenous (AV) fistula
A surgeon connects an artery to a vein, usually in your arm, to create a fistula
Connecting an artery to a vein makes the vein grow wider and thicker, making it easier to place the needles for dialysis
The AV fistula also has a large diameter that allows blood to flow out and back into the body quickly
pros and cons of AV fistula
Needs time to mature
An AV fistula is the best long-term access
- provides highest blood flow for dialysis
- is less likely to become infected or clot
- lasts longer
Arteriovenous (AV) graft
An AV graft is a strong artificial tube inserted by a surgeon underneath the skin of the forearm, upper arm or thigh
One end of the tube connects to an artery and the other end connects a vein
pros and cons Arteriovenous (AV) graft
Will need 2-4 weeks to mature
Prone to infection and blood clots
An AV graft is usually inserted if the patients’ veins are not suitable for an AV fistula
Central venous catheter (CVC)
A CVC is a pair of hollow tubes called catheters or lines
The catheter is placed into the large central vein in the neck – the internal jugular vein
The ends of the tubes are left on the outside of the body so they can be attached to the dialysis machine
An ultrasound machine will be used to find the central vein in the neck
The brand of catheter used of dialysis access is called “Tesio”
pros and cons Central venous catheter (CVC)
Most Tesio’s are used short-term – whether it is inserted for emergency dialysis or used a ‘bridging’ access whilst an AVF or AVG matures; some are used long-term if AVF or AVG not possible
Tesio lines are great for emergency access but they do have a tendency to become infected or to clot
two main “ways” that patient can receive their dialysis
Conventional (hospital) dialysis
Home dialysis
conventional dialysis
Usually done three times per week, for about 3-4 hours for each treatment
Patients blood is drawn out through a tube at a rate of 200-400ml/min
Blood is then pumped through the dialyser and then filtered
The filtered blood is pumped back into the patients bloodstream through another tube
conventional dialysis advanatages
Very efficient
Improves compliance
Allows healthcare professionals to manage any complications more efficiently
Allows healthcare professionals to monitor bloods and make adjustments if needed more efficiently
?support network for patients that benefit from that network
conventional dialysis dis-advanatages
Strict diet and fluid restrictions
Aggressive fluid removal can cause dramatic drop in blood pressure during the session
Aggressive fluid removal can cause pain muscle cramps
3xweek = very limiting on freedom
Home dialysis
Allows longer or more frequent dialysis, which comes closer to replacing the work healthy kidneys do
Allows for a flexible schedule:
- standard schedule: 3xweek or every other day for 3-5 hours
- daily schedule: 5-7 days per week for 2-4 hours
- nightly schedule: 3-6 times per week while you sleep
Home dialysis ADVANTAGES
Home dialysis dramatically improves quality of life by aiding flexibility
Daily/nocturnal dialysis is less aggressive – less muscle cramps/hypotension
Daily/nocturnal dialysis allows more “normal” diet and fluid intake
Home dialysis DISADVANTAGES
Increased risk of infections if poor aseptic technique
Delayed access to healthcare staff if there are any issues e.g. clotting
Risk of poor compliance for those that are less motivated
?potentially isolating
Home environment – storage space for dialysis fluids and the machine?
Peritoneal dialysis (PD)
Form of dialysis that occurs inside the body
Catheter is placed into abdomen surgically
Sterile dialysate is pumped into the peritoneal (abdominal) cavity through a catheter
Peritoneal membrane acts as a natural filter
how is PD different to the other types of dialysis
this occurs INSIDE the body. (the others were outside via a machine with a dialyser (tube)).
describe the dialysate of PD
The dialysate contains glucose which comes in various concentrations – this creates an osmotic gradient to remove excess waste and water
The dialysate sits in the peritoneum where waste and excess fluids/minerals diffuses into the dialysate
This dialysate is then removed from the peritoneum via the catheter and discarded
two types of PD?
- Continuous Ambulatory Peritoneal Dialysis (CAPD)
- Ambulatory Peritoneal Dialysis (APD)
ONES CONTINUOUS ONES NOT
- Ambulatory Peritoneal Dialysis (APD)
Continuous Ambulatory Peritoneal dialysis (CAPD)
A bag containing the dialysate is attached to the catheter in the abdomen
The dialysate flows into the peritoneal cavity via gravity
The dialysate sits in the peritoneal cavity to allow waste and excess fluid to be drawn out of the blood, across the peritoneum lining
The dialysate is then drained into a waste bag
Usually done 3-5 times a day
Benefits of CAPD
Continuous and machine-free
Patients tend to time their exchanges during mealtimes and at bedtime
Ambulatory Peritoneal dialysis (APD)
Patient attaches a bag of dialysate to the APD machine before going to sleep
The machine performs a number of fluid exchanges
Patient will need to be attached to machine for 8-10 hours
ADVANTAGES OF PD
Patient-centred
Increased flexibility – can be carried out at home or work
Less fluid/diet restrictions
Less side effects in comparison to HD/HF/HDF e.g. hypotension or muscle cramps
Most similar to kidneys
Can be done at night (APD)
Skilled nursing only required for initial training
DISADVANTAGES OF PD
~ four exchanges per day
Permanent external catheter
Change of body image
Risk of infection
Will be tied to the machine at night (APD)
Storage space is needed for supplies
Requires self-motivated and competent patient
Not as efficient as HD
Greater loss of albumin
COMPLICATIONS OF PD
Increased risk of infections within the peritoneum peritonitis. Will require hospital admission and IV antibiotics
Developing of diabetes usually occurs due to high glucose concentration of dialysate
Sclerosing peritonitis thickening of peritoneum that encloses the small intestine. This can lead to partial or complete small bowel obstruction
considering pharmacokinetics, when choosing What is the type of dialysis?
HDF more aggressive, more likely to clear the drug
considering pharmacokinetics, when choosing What is the molecular weight of your drug?
Larger molecular weight less likely to be cleared
considering pharmacokinetics, when choosing Is the drug hydrophilic or lipophilic? What is the Volume of distribution?
High VoD distributes to fatty tissue (lipophilic) not as much in the blood less likely to be cleared
considering pharmacokinetics, when choosing What about the level of protein binding?
Highly protein bound larger molecule less likely to be cleared
considering pharmacokinetics, when choosing Is the drug renally cleared?
If not usually renally cleared i.e 25-30% of total body clearance, then dialysis will not clear much of it either
considering pharmacokinetics, when choosing Any active or toxic metabolites?
Toxic metabolites? give before HD session so that HD removes the toxins
considering pharmacokinetics, when choosing What is the drugs therapeutic index?
Care with narrow therapeutic index – may need to adjust timings in respect to dialysis
considering pharmacokinetics, when choosing OD dosing Vs multi-dose regimens?
E.g. 5 times a day? likely to be cleared by dialysis does it exist in MR?
considering pharmacokinetics, when choosing Regular dosing Vs STAT doses
Stat “one-off” doses are not affected too much by dialysis vs regular long term medication
