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What do kidneys do? What are they a major component of?
Filter the blood to maintain water, electrolytes, waste, and balance acids and bases
Major component of metabolism and excretion of certain medications
What is renal failure defined as? What are the 2 types of renal failure?
Partial or complete loss of kidney function
Inability to maintain fluid, electrolytes, waste or acid-base
Accumulation of medications renally excreted
Two types of renal failure
Acute Kidney Injury (AKI)
Chronic Kidney Disease (CKD)
How should you treat AKI?
Address underlying causes of AKI
Think of possible meds responsible
Consider external support while trying to achieve recovery of kidneys
How should you consider treating CKD?
There is NO cure for CKD as kidneys become progressively injured and lose function over time
Two options:
External support
Kidney transplantation
What does Renal Replacement Therapy act as?
As an artificial kidney to replicate lost functions
Optimize fluid balance
Prevent or treat electrolyte and acid-base disturbances
Elimination of medications
Avoid hemodynamic or nephrotoxic-related kidney injury
How does dialysis work?
Blood is pumped out of patient into blood line
Heparin is added to prevent clotting
Blood sent to dialyzer where excess fluids, electrolytes and wastes are removed (effluent)
Cleaned blood is removed of air bubbles and returned to patient
How is dialyzed blood accessed by?
Arteriovenous fistula (AVF)
Arteriovenous graft (AVG)
Central venous catheter (CVC)
In terms of dialysis access what is the differences in AVF, ABG, and CVC?
AVF
Time to mature/use: 2-6 months
Maintenance: minimal
Infection risk: low
Thrombosis risk: low
AVG
Time to mature/use: 2-4 weeks
Maintenance: frequent (patency)
Infection risk: medium
Thrombosis risk: medium
CVC
Time to mature/use: immediate
Maintenance: frequent (exchange)
Infection risk: high
Thrombosis risk: high
What does a hemodialysis dialyzer contain? What does it remove?
Dialyzer contains semipermeable membrane that blood passes through
Removes solutes (waste and electrolytes) without removing important components of blood
What does a dialysate fluid contain?
Contains electrolytes and buffer
Waste removal while normalizing plasma composition
Dialysis occurs through which. main ways of filtration?
Diffusion (requires dialysate)
Convection (requires pressurized blood)
What impacts RRT removal? What is the mode of removals?
Molecular weight impacts RRT removal
Mode:
Large molecules: convection or adsorption (nothing above 50k is cleared)
Middle: convection better than diffusion
Small: diffusion better than convection
What are the indications for RRT?
“AEIOU”
Acidosis/azotemia
Electrolyte imbalance
Intoxication/drugs
Overload of fluids
Uremia
What is Azotemia and when is it seen? What does it lead do and what may it progress to?
Elevation of nitrogen waste products in blood (including urea)
Seen when kidney function worsens
Leads to elevation of BUN and SCr
May progress to uremia (urea in blood
What are the toxic medications removed by RRT?
Acetaminophen
Barbiturates (phenobarbital)
Carbamazepine
Ethylene glycol
Gabapentin / Pregabalin
Lithium
Metformin
Methanol
Phenytoin
Salicylates
Theophylline
Valproic acid
What are the different modalities of RRT?
Intermittent → IHD (intermittent hemodialysis), SLEDD (slow low efficiency daily dialysis)
Continuous → CRRT (continuous renal replacement therapy)→ CVVH (continuous venovenous hemofiltration), CVVHD (continuous venovenous hemodialysis), CVVHF (continuous venovenous hemodiafiltration)
What is the duration of intermittent hemodialysis? What does it remove, what risk if made? When can it be performed?
Shortest dialysis procedure
4-6 hours
Performed 3 times per week
Removes the most solute and fluid
Risk of hypotension
Can be performed both inpatient and outpatient
What are the IHD (intermittent) outpatient options?
Dialysis clinics
Fixed time slot
Availability of healthcare professionals
Home hemodialysis
Option for higher frequency
More flexibility
What is the process of peritoneal dialysis?
Waste products cross the semipermeable membrane into the peritoneal space with the dialysate
What is sustained low efficiency dialysis? What does it have less risk of? What is limited and who is it only performed in?
Hybrid between IHD and CRRT
6-12 hours
Less risk of hypotension compared to IHD
Limited drug clearance data
Only performed in critically-ill patients
How long is continuous RRT ran over? What is characteristic of the removal of solutes and fluid? Who is it only performed in?
Run over 24 hours
Slower removal of solutes and fluid
Closer to physiologic kidney function
Lower risk of hypotension
Only performed in critically-ill patients
In continuous RRT, what is the differences in CVVH, CVVHD, and CVVHDF?
CVVH:
Mechanism of solute clearance → convection
Dialysate? → no
Replacement fluid? → yes
Solute size removed → small to large
Effluent → fluid removed + replacement fluid
CVVHD:
Mechanism of solute clearance → diffusion
Dialysate? → yes
Replacement fluid? → no
Solute size removed → mostly small
Effluent → fluid removed + dialysate
CVVHDF:
Mechanism of solute clearance → diffusion and convection
Dialysate? → yes
Replacement fluid? → yes
Solute size removed → small to large
Effluent → fluid removed + replacement fluid + dialysate
Why is replacement fluid used? What are the buffer agents?
Replace fluids lost during CRRT
Containing electrolytes and buffer to return blood closer to physiologic state
Buffer agents:
Lactate
Bicarbonate
Acetate
In Lactate, what does it convert to in physiologic conditions? When is it not used?
Bicarbonate
Not used in liver failure > lactic acidosis
In Bicarbonate, what is known about its usage? What change does it make to arterial pressure? Where is it preferred? What are the precipitation concerns?
Most commonly used
Little change in arterial pressure
Preferred in liver failure
Precipitation concerns with calcium and magnesium
In acetate, what is known about the use? What can it cause?
Historical use, though poor control of acid-base balance
Can cause hyperacetatemia and vasodilation
What are complications of RRT?
Infection
Thrombosis
Electrolyte abnormalities
Metabolic alkalosis
Hemodynamic shifts
Medication clearance
What is the infection risk in RRT? What are some signs of possible access site infection?
Increased risk from frequent bloodstream access
Differing risk based on access
Signs of possible access site infection:
Redness or swelling of site
Drainage or pus along site
Fever
Chills
Malaise
Rank the bloodstream infection risk?
Fistula (lowest risk) → Graft → Central Venous Catheter (highest)
When is management of infection in RRT only in?
Only for ACUTE infection
In management of infx in RRT, what is antibiotic therapy duration?
4-6 weeks of therapy
Lower duration possible
In management of infx in RRT, what is source control?
Removal of catheter
Culture catheter tip
Surgical removal of graft
WHat is a primary issue in CRRT?
Clotting
Clotting in CRRT circuit can lead to what?
Anemia due to blood lost in circuit
How do you minimize clotting in CRRT circuit anticoagulation and what are the options?
Provide anticoagulation to the circuit to minimize clotting
Options:
Heparin
Trisodium Citrate
What are advantages and disadvantages in UFH and Citrate?
UFH: easily reversible, inexpensive → increased bleeding risk HIT
Citrate: lower bleeding risk → hypocalcemia
In Trisodium citrate related hypocalcemia, what does it bind with? What do we need?
Binds with calcium, forming chelated complexes
Calcium prevented from activating clotting pathways
Need calcium replacement
When not in use, what can happen in RRT catheter? What can prevent this?
Clotting
Prevented by either a saline flush or by a citrate “lock”
If occluded in RRT catheter, what can we do?
If occluded, may instill tissue plasminogen activator (tPA; Cathflo) in catheter for 30 minutes
What is the comparison between IHD vs SLED vs CRRT?
IHD
Duration → 4-6 hrs
Blood flow rate → >300 mL/min
Dialysate flow rate → 500-750 mL/min
Fluid removal → fluid removed + replacement fluid
SLED
Duration → 6-12 hrs
Blood flow rate → 200 mL/min
Dialysate flow rate → 100-200 mL/min
Fluid removal → fluid removed + dialysate
CRRT
Duration → 24 hrs
Blood flow rate → <200 mL/min
Dialysate flow rate → <50 mL/min
Fluid removal → fluid removed + replacement fluid + dialysate
Is there always requirement for long term RRT? What are reasons for stoping RRT?
Not all patients will require long-term RRT
Possible reasons for stopping RRT
Recovery of kidney function (AKI)
Removal of lines due to infection
Withdrawal of supportive measures
The clearance of meds is dependent on what?
PK profile and size of pores in hemofilter
What causes increased medication clearances in dialysis?
Hydrophilic
Neutral charge (non-ionic)
Molecular weight <500 Daltons
Low volume of distribution
Low protein binding
Medication clearance changes with what? What is preferred, PK dat or guideline recs?
with worsening renal function and dialysis
PK data>guideline recs
Dosing adjustments via drug databases
Recs per facility protocols
Loading vs maintenance doses
Loading doses not impacted * check recording for rest
What is vancomycin?
A glycopeptide antibiotic used in hospital settings for management of moderate to severe infections
What is dosing based on in vancomycin? What is vancomycin typically seen with in terms of doses?
Dosing based on trough / area under the curve (AUC) targets
Typically seen with standing doses with regular intervals
Ex: q8 hours, q12 hours, q24 hours
In AKI and CKD, vancomycin’s PK profile does what? Which is more stable in clearance?
In AKI and CKD, vancomycin's pharmacokinetic profile changes, especially in its clearance
CKD should have a stable clearance > able to calculate a standing dose
AKI (or AKI on CKD) is more unstable > spot dosing
Dosing strategies is dependent on what? In CRRT patients can use what?
Dosing strategies will be dependent on which modality is used and whether the patient has oliguria or anuria
In CRRT, patient should have steady removal, can use a standing dose
For vancomycin in IHD, when do you check serum vanc levels? What is the goal serum level?
Check serum vancomycin level before and/or after HD
Goal serum level:
20-25 prior to dialysis
15-20 after dialysis
What do you calculate for vanc in IHD?
Calculate dialysis clearance
Around 30-40% cleared in HD
Calculate a dose to give
Based on patient's volume of distribution (Vd)
What is the volume of distribution in Vanco?
Vd(L) ~ 0.7x Actual Body Weight (kg)
For Vanco in IHD, what is the change in serum level needed?
Desired level (mcg/mL) – current level
(mcg/mL
For Vanco in IHD, what is the change in serum Vanco level?
Vanco Dose (mg) / Vd = needed change in serum level