mod 2: dialysis and ESKD care

indications for dialysis

• A → acid-base problems

• E → electrolyte problems

• I → intoxications

• O → overload of fluid

• U → uremic symptoms

uremic symptoms

• may occur when a patient has a significant accumulation of nitrogenous waste products in their body

• N/V

• anorexia or declining nutritional status

• fatigue

• metallic taste

• cardiovascular → HTN or HF or bleeding

  • sudden cardiac death

functions of the kidney

1. excretory

   • it’s important to note that dialysis only really targets this process!

2. metabolic

3. endocrine

kidney failure options

• transplant

  • usually the preferred way to go for patients, especially children and young adults

• conservative care

  • medical management, as well as managing diet

  • usually for more elderly patients or those with a terminal illness

• dialysis

  • hemodialysis

  • peritoneal dialysis

diffusion

• solutes moving across a concentration gradient

  • this is used during dialysis to remove waste from the body and clean the blood

• factors:

  • concentration gradient (high→low)

  • molecular size

  • water solubility

  • charge

  • HD filter

    • contains fibers that are hollow (where the blood runs through), and these fibers are the semi-permeable membrane between blood and the dialysate (which kind of “soak” the fibers)!

  • blood flow rate (BFR)/dialysis flow rate (DFR)

ultrafiltration

• the removal of fluid/water

  • fluid moves via hydrostatic pressure and/or osmosis (low→high concentration)

convection

• solutes being dragged with a solvent

hemodialysis (HD)

• involves the concurrent flow of dialysate and blood on opposite sides of a semi-permeable membrane/filter

• two processes occur:

  • solute removal via diffusion and convection

  • fluid removal via ultrafiltration

    • amount of fluid removal depends on what the patient’s weight is compared to what we think their euvolemic (dry) weight is

advantages to hemodialysis

• efficient solute clearance

• low technique failure

• close monitoring of patient

disadvantages to hemodialysis

• loss of patient independence (especially if waiting for a kidney)

• scheduling and transportation to a dialysis center (multiple times per week for several hours)

• large needles

• many complications

• loss of residual kidney function (due to drop in BP)

HD filters

• three types:

  • conventional

    • filter has small pores

  • high efficiency

    • has a larger surface area

    • has large or small pores

  • high flux

    • has larges pores

      has increased “middle molecule” clearance

types of hemodialysis vascular access methods

• catheter

  • temporary

  • can be tunneled to be slightly more permanent

  • least preferred, but best for emergencies

• arteriovenous (AV) graft

  • preferred

  • permanent

• AV fistula

  • most preferred!

  • permanent

AV fistula

• when an artery is (surgically) connected with a vein to create turbulent blood flow and strengthen the vein so that the vein becomes more strengthened but remains pretty pliable

  • this will lead to a mature site that we can use to place the needles into the patient’s arm for dialysis

• it is designed to be stable for the high-volume blood withdrawal and return needed for dialysis treatments

AV graft

• when a synthetic tube is used to connect an artery to a vein

  • the dialysis needles would be inserted into that loop

assessing dialysis adequacy

• urea reduction ratio (URR)

  • URR = [(preBUN - postBUN) ÷ preBUN] • 100

• K•t ÷ v

  • K = constant for filter relating to urea removal

  • t = time on dialysis

  • V = volume of distribution of area

  • goal is 1.4 (minimum of 1.2)

common complications of hemodialysis (HD)

• vascular access complications

  • infection

  • thrombosis

    • these may be more likely with AV grafts

• intradialytic problems

  • hypotension

  • cramps

  • N/V

  • headache

  • chest/back pain

  • pruritus

  • fever/chills

vascular access infections

• one of the most important complications of dialysis

• most common with catheters > grafts > fistulas

• need to distinguish between local infection vs bacteremia!

  • monitor for both

• coverage may include gram-positive and/or gram-negative coverage

• however, infections are often resistant to ABX because of the frequency of ABX that patients do receive

• can be treated at a dialysis facility

  • pts can receive IV abx administered during the dialysis procedure or after the dialysis procedures, however, these medications may not end up on a patient’s medication list!

    • importance of med rec

contributing factors to hypotension during dialysis

• excessive fluid removal

• patients taking BP medications right before dialysis, especially if they’re prone to hypotension

• autonomic dysfunction, making it harder to control BP

• low Ca2+ and Na+ bath of dialysis

• dialysate temperature

• intradialytic eating (eating during the procedure)

  • this can cause more blood to go to the GI tract

acute treatment of hypotension as a result of dialysis

• trendelenburg position

  • when the head is below the heart and the legs/feet are raised

• decreasing or stopping ultrafiltration

• administering NS (100-200 mL)

• administering 23.4% saline (10-20 mL)

• administering mannitol

chronic/prevention of hypotension as a result of dialysis

• non-pharmacologic

  • adjusting the estimated dry weight (EDW)

    • maybe the patient’s weight is higher than we think it is, and so we don’t have to remove as much fluid

  • slowing ultrafiltration rate

  • making dialysate temperature colder

    • can cause vasoconstriction

    • makes the patient feel colder (especially on the inside)

• pharmacologic

  • administering midodrine 30 mins prior to HD

  • think about when the patient’s BP medications are taken

medication-related factors affecting HD drug removal

• molecular weight/size

  • larger drugs are less likely to be removed

• protein binding

  • high degree of protein binding → less likely to be removed

• volume of distribution

  • large Vd → less likely to be removed due to increased tissue binding

• water solubility

  • not water-soluble or lipophilic → less likely to be removed

peritoneal dialysis (PD)

• involves dialysate instilled into the peritoneal cavity via a catheter, where it dwells for a prescribed amount of time, and is then drained (via that catheter)

  • so basically, the dialysis is occurring inside the patient’s body

  • the filter is the peritoneal membrane itself

  • fluid and solutes are removed during this procedure

advantages of peritoneal dialysis (PD)

• improved hemodynamic stability

• preservation of residual renal function (RRF)

• convenient

• patient independence

• little blood loss

disadvantages of peritoneal dialysis (PD)

• high rate of technique failure

• patient responsibility

• peritonitis

• glucose absorption

  • there is glucose in the solution, which may be a problem for patients with DM

  • even for patients without DM, exposing them to a. high amount of glucose can lead to weight gain

PD prescription

• includes:

  • dialysate type

  • dialysate volume

  • number of dwells per day

  • length of dwells

  • manual or automated

PD modalities

1. continuous ambulatory peritoneal dialysis (CAPD)

   • most used

   • patient does multiple manual exchanges throughout the day and then one long dwell overnight

2. continuous cycling peritoneal dialysis (CCPD)

   • also very common

   • patient has a machine (called a cycler) that they would use at night where they have multiple dwells, and then the patient would have one long dwell during the day

   • this means that the patient really must stick to a schedule (be in bed at a particular time and for that length of time

common complications of PD

• peritonitis

peritonitis

• infection of the peritoneal cavity

• intra-peritoneal (IP) abx are generally preferred for treatment

significance of intra-peritoneal drug administration for peritonitis

• when you put the drug directly into the peritoneal cavity, you’re able to have a high concentration of drug in this cavity and then that drug may cross the peritoneal membrane into systemic circulation

  • the point is, the majority of the drug will be at the site of action (the peritoneal cavity)

• if we try to treat the infection via IV administration, we now have to give a much higher dose to achieve an adequate concentration inside the peritoneal cavity

  • can cause more side effects/toxicities

special considerations in ESKD

• adherence

  • treatment

  • diet (potassium, phosphate, calcium)

  • medications

• medication dosing concerns

  • timing around dialysis

  • PK alterations

  • accumulation?

  • dialysis drug removal?

• protocol-based management

  • anemia

  • CKD-MBD

medication-related factors affecting HD drug removal

• molecular weight/size

  • larger = less likely to be removed

• protein binding

  • high degree of protein-binding = less likely to be removed

• volume of distribution

  • large Vd = less likely to be removed

• water solubility

  • lipophilic = less likely to be removed