dialysis Flashcards
CHEMICAL definition of dialysis
the separation of particles in a liquid on the basis of differences in their ability to pass through a membrane
MEDICAL definition of dialysis
the clinical purification of blood, as a substitute for the normal function of the kidney
national kidney foundation definition of dialysis
treatment that does some of the same things done by healthy kidneys. needed when your kidneys can no longer take care of your own body’s needs
2 different types of dialysis
hemodialysis (both traditional and CRRT)
peritoneal dialysis (continuous ambulatory or cyclic peritoneal dialysis)
indications for dialysis
AEIOU
Acidosis
Electrolyte imbalance
Intoxication
Output
Uremia
when to initiate dialysis in CKD patients
preparation: stage 4 CKD (GFR<30)— should plan access for AV fistula
and when GFR < 15 should begin renal replacement therapy
what is the “perfect” timing for starting dialysis
it is a compromise between extending dialysis free period as long as possible but avoiding complications by waiting too long
primary goal of hemodialysis
to restore intracellular and extracellular fluid environment that is characteristic of normal kidney function—-based upon diffusion of solutes across a semipermeable membrane down a concentration gradient
______ is transported INTO dialysate
urea from the blood
______ is transported FROM dialysate into the blood
bicarb
diffusion is movement of substances _______
down a concentration gradient
what is ultrafiltration
movement of water across the dialyzer membrane as a result of hydrostatic or osmotic pressure. primary purpose being removal of excess total body water
what is convection
solutes are dragged across the membrane with water transport– occurs if pores in dialyzer are large enough for solutes to pass
relationship between diffusion and convection
can be controlled separately and the dialysis prescription can be personalized to achieve degree of solute and fluid removal
apparatus required for hemodialysis
dialyzer
dialysis solution (aka dialysate)
tubing for transport of blood & dialysis solution
machine
what is the dialyzer
plastic chamber w/ ability to perfuse blood & dialysate compartment simultaneously at very high flow rates
(hollow fiber capillary dialyzer most common)
what is the dialysate
solution of pure water, electrolytes, and salts. purpose is to pull toxins from the blood via diffusion (high concentration of waste in the blood, low concentration in dialysate).
NOT A STERILE SOLUTION
different lines of the tubing in hemodialysis
arterial line: carries blood from patient to dialyzer
venous line: carries dialyzed blood back to the patient
______ is administered to prevent clotting in the dialyzer
anticoagulant such as heparin
how frequent is in-center hemodialysis, typically
3 weekly sessions, 3-5 hours long
goals/adequacy measures of hemodialysis
achieve dry weight (normotensive, edema free)
Kt/V urea = 1.2
what is Kt/V urea
fraction of the patient’s total body water that is cleared of urea during a dialysis session
K= urea clearance of the dialyzer
T= duration of the sessio
V urea= patient’s volume of urea distribution
what is the preferred type of access for hemodialysis
arteriovenous fistula (AV fistula)
what is AV fistula
access made by joining an artery & vein in the arm; large diameter; preferred for long term HD due to less infection and clotting; takes at least 1-2 months to mature
what are other types of access for HD besides AV fistula
graft (man made tube to connect artery to vein, takes 2-3 weeks, shorter survival than fistula, higher rates of infection and thrombosis)
central venous catheter (temporary access, placed if disease progresses quickly and there isn’t time to place fistula/graft, short life span, prone to infection and thrombosis)
what are the complications of dialysis
hypotension
HTN
cramps
chest and back pain
pruritis
fever & chills
vascular access: dysfunction, thrombosis
infection: leading cause of mortality, sepsis
how is intradialytic hypotension managed?
Pharmacologic: oral midodrine 5 mg 2-3 times daily
Non-pharm: Trendelenburg position, decrease rate, give fluids, etc
how is hypertension managed?
changes in timing of antihypertensives; carvedilol 6.25 mg BID
how is pruritis managed?
acute: diphenhydramine or hydroxyzine
prevention: topical emollients & adequate hemodialysis
how is access thrombosis managed?
flush, alteplase 2 mg/2mL per catheter port, replace catheter
pros/cons of home hemodialysis?
short daily sessions 5-7x/week x 2 hrs
less fluid removed at each session, reduces symptoms
but need to have a responsible care partner to help
what is continuous renal replacement therapy (CRRT)
renal replacement therapy applied for 24h/d in an ICU
more “physiologic”
pros/cons of CRRT
pros: physiologic, minimizes hypotension in hemodynamically unstable patients, used in acute renal failure
cons: lack of fever if infected (blood flowing out and back in constantly cools body down), medication dosing changes
classic indications for CRRT
hyperkalemia, severe metabolic acidosis, diuretic- resistant volume overload, oliguria or anuria, uremic complications, drug intoxications
contraindications for CRRT
patient declines, inability to establish vascular access, lack of trained personnel
what is a common error with medications in a patient on dialysis
dosing medications based on SCr and not realizing they are on dialysis— you can’t calculate CrCL on dialysis because it means nothing– their kidneys don’t work.
what is peritoneal dialysis
dialysis treatment that uses the peritoneum and dialysate; the peritoneal cavity is filled w/ the dialysate and remains there for a “dwell time”— at the end of said dwell time, an exchange occurs
advantages of peritoneal dialysis
hemodynamic stability
can do it at home (independent), convenient
suitable for the very old and very young
better preservation of residual renal function
less blood loss
no systemic heparin necessary
disadvantages of peritoneal dialysis
protein loss thru peritoneum
reduced appetite
sense of abdominal fullness
predisposed to malnutrition
PERITONITIS RISK!!!!!!!
what are different types of peritoneal dialysis
continuous cycler-assisted peritoneal dialysis (CCPD)- usually done at night, a machine does exchanges, takes ~9 hours; in the morning the abdomen is filled with dialysate that remains the entire day.
continuous ambulatory peritoneal dialysis: exchanges are done by hand throughout the day; gravity is used to fill the abdomen and drain it
what is peritonitis
inflammation of the peritoneum usually due to bacterial or fungal infection (1 episode per 24 patient months)
is a major cause of catheter loss in PD
clinical presentation of peritonitis
abdominal pain and cloudy effluent
fever, nausea, vomiting, chills
dialysate WBC>100 (50% pmns)
organisms causing peritonitis
s. epidermidis (most common)
s. aureus
strep sp
eneterococcus sp
E. coli
pseudomonas
fungi
treatment of peritonitis
gram + coverage w/ vanco or 1st gen ceph
gram - coverage w/ 3rd or 4th gen ceph or aminoglycoside
ex: ceftriaxone + vanco
how is adequacy of PD determined
Kt/V weekly= 1.7
what does residual renal function mean
some patients still make urine when on dialysis: improved survival, better solute removal, better BP control
how to preserve residual renal function
avoid nephrotoxins, avoid hypotension, ACEi/ARBs may help, avoid excess fluid control
protein restriction on dialysis?
protein restriction in CKD increases risk of malnutrition but is used to slow progression of CKD….
protein restriction only if GFR<25 NOT on dialysis
