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PDAT3 > 26 - Drug use in Dialysis > Flashcards

26 - Drug use in Dialysis Flashcards

1
Q

When to start dialysis?

A
  • prepare for dialysis once CKD G4*
  • *ESRD when 1+ present:**
  • *S/Sx of kidney failure**
  • inability to control –*volume status or BP
  • continued worsening of* nutritional status or cognitive impairment
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2
Q

Which access type is IDEAL?

Hemodialysis

A

Hemodialysis requires PERMENANT access, done 3x week for 3-5 hours

ARTERIOVENOUS FISTULA = AV
Gold Standard

  • *AV Graft**
  • synthetic grafting, for those who CANT do AV Fistula*
  • *Catheter**
  • least ideal due to INFECTION*
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3
Q

Pros & Cons
Hemodialysis

A

Pros

  • *Intermittent treatment** // Can be done at home
  • *Closer monitoring / better defined** / technique failure is low

Cons
loss of patient independence / vascular access / infection
RAPID DECLINE in Residual renal FXN
Increase in:
HypoTension / Disequilibrium / Muscle Cramps

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4
Q

Dialysate
Function / Contains what?

A

Corrects ELECTROLYTE abnormalities
water & e- pumped
OPPOSITE to flow of blood opposite to semipermeable membrnae

BICARBONATE
Metabolic Acidosis occurs with kidney failure
avg levels 15-17 mEq/L // replenished @ 30-32mEq /L

  • *POTASSIUM**
  • *HYPERkalemia** occurs with kidney failure
  • *Removed by dialysis –> replenished @ 2-3 mEq/L**
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5
Q

Hemodialysis
based on principles of what?

A
  • *DIFFUSION**
  • *Uremic toxins** are REDUCED if they are small-medium sized
  • *CONVECTION**
  • *Excess fluid is REMOVED**
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6
Q

What type of DIALYZER?

Fibers have LARGE pore size

Allow for diffusion of LARGER molecules

Rate of water transfer = much higher

A
  • *HI-FLUX**
  • *most common form**

•Dialyzer is made of several thousand bundles of hollow fibers
The fibers are thin, semipermeable

membranes that allows for blood and dialysate
to be pumped in opposite directions for maximum diffusion

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7
Q
  • *Diffusion**
  • *Dependent on WHAT?**
A

Dependent on:
Concentration Difference
Molecular SIZE of Solute
Membrane Qualities

Coefficient of Diffusion
specific for the TYPE of membrane used & solute used

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8
Q
  • *Convection**
  • *Dependent on WHAT?**
A

Dissolved solutes are transported/dragged across membrane w/ water
driven by:
HIGHER hydrostatic pressures in BLOOD compartment

Sieving Coefficient
ratio of SOLUTE in ultrafiltrate : CONCENTRATION in plasma (return to pt)
Clearance of Drug = S x Ultrafiltration Rate

Dependent on:
membrane PORE SIZE // SIZE / CHARGE of solute

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9
Q

ULTRAFILTRATION
Definition / Function

A

Movement of water across the dialyzer membrane due to
hydrostatic or osmotic pressure

Principle way to:
REMOVE EXCESS FLUID

  • *UltraFiltration procedure = done for FLUID OVERLOADED PTS**
  • even W/O dialysis*

medicare pays for 1 extra dialysis or ultrafiltration / month

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10
Q
  • *Peritoneal Dialysis**
  • *is better for** patients who may have?

& Differences

A

HypoTension

Significant RESIDUAL renal Fxn

LARGER Fluid Gains

Peritoneal membrane = dialyzing surface
intestine & mesentary is tightly covered by visceral membrane
single layer of mesothelial cells overlaying

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11
Q

Pros of Peritoneal Dialysis

A

More hemodynamic Stability

HIGHER clearance of LARGER SLUTES

BETTER conservation of residual renal fxn

MEDICATIONS –> can use intraperitoneal meds

LESS BLOOD + IRON LOSS

Independence

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12
Q

CONS
of peritoneal dialysis

A
  • *MALNUTRITION**
  • *infections**

LARGE body size –> inadequate ultrafiltration

High technique failure

HERNIAS / LEAKS common

NO IV ACCESS

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13
Q

Types of Peritoneal Dialysis

A
  • *CAPD**
  • *manual**, continuous ambulatory PD
  • *APD**
  • *automated, CYCLER**, done overnight / daytime
  • *NIPD**
  • nocturnal** intermittent PD, similar to APD but *dialysate free during DAY

Continuous Flow PD

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14
Q

Contents of
Peritoneal Dialysis DIALYSATE

A

Contain:
Glucose or Icodextrin // Electrolytes // Buffer Solutions

Dextrose solutions = HYPEROSMOLAR –> ULTRAFiltration
not the most IDEAL osmotic agent
cytotoxic to mesothelial cells & peritoneal leukocytes
↑BG & ↑weight gain

ICODEXTRIN = isoosmolar
produces prolonged ultrafiltration –> long dwell times in APD/CAPD

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15
Q

What solutes move in
Peritoneal Dialysis

A
  • *Peritoneal Capillaries –> across Membrane –> Peritoneal CAVITY**
  • *UREA / CREATININE / POTASSIUM**
  • opposite direction*
  • *BUFFERS = Bicarbonate / Lactate**

Diffusion & Convection
same as HD, allow for SOLUTE MOVEMENT

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16
Q

Dwell Time

A

How LONG dialysate stays in Peritoneal Cavity

↑Dwell time –> ↓Osmotic Gradient

17
Q

What is REMOVED by
Peritoneal Dialysis

A
  • Low molecular weight substances*
  • *Creatinine / Urea / Potassium**

NEGATIVELY charged solules move SLOWER
vs pos charged (peritoneal cavity is NEGATIVELY charged)
PHOSPHATE = NOT REMOVED by PD

  • *Large Molecules = Albumin**
  • *can cross peritoneium**
18
Q

Peritoneal Equilibrium Test
PET
&
D/PCr Ratio

A

Done for EACH PATIENT to determine:
RATE OF TRANSPORT

  • *Dialysate-Plasma Creatinine Ratio = D/PCr**
  • *>0.81 = High** // 0.65-0.81 = High-avg
    0. 5 - 0.65 low avg // <0.5 low

High Transporters –> rapid clearance of smoll molecules

Low Transporters –> low clearance for solutes
requires MORE exchanges

19
Q

Peritonitis

A

Major complication where

  • *INFECTION @ PERITONEAL CAVITY**
  • CATHETER SITE is MAIN source*, Gram positive (majority)

ANTIBIOTICS given INTRAPERITONEAL
preferred method

20
Q

Types of
Continuous Renal Replacement

A

CVVH
CONVECTION-based, hemoFILTRATION
high filtrate flows –> enhance solute removal

  • *CVVHD**
  • *DIFFUSION**-based, can he at home
  • *CVVHDF**
  • *HemoDialFiltraion**, BOTH diffusion + Convection
  • *SLED**
  • SLOW EXTENDED daily dialysis, hybrid therapy*
21
Q

Positives for

CRRT

A

GOOD IN HOSPITALS

Therapy is steadier & gentler

Potentially better renal RECOVERY

Allows for use of EXTRA FLUIDS = TPN/IV MEDS
pt has enough room through continuous ultrafiltration

  • *Hemodynamically BETTER TOLERATED**
  • less effect on INTRACRANIAL pressure*
22
Q

URINE REDUCTION RATIO
URR+Kt/V
should be @ what level?

A

Used frequently to:

  • *Measure the REMOVAL of UREA**
  • *> 65%**
  • *Kt/V**
  • *HD > 1.2**

>1.7 PD

23
Q

Vd Considerations for Renal Patients

High / low Vd

A
  • *HIGH VD**
  • *Lipid-SOLUBLE** & Highly TISSUE-BOUND drugs
  • Low Vd*
  • Lipid-INSOLUBLE* drugs
24
Q

BioAvailability
PK in Renal Patients

A

REDUCED GI ABSORPTION
slowed absorption
concurrent meds
ALKALINE environment

25
Q

Protein Binding
​PK in Renal Patients

A

Protein levels are DECREASE
VV
MORE free Drug

26
Q

Metabolism & Clearance
​PK in Renal Patients

A

Metabolism:

  • SLOWER* hydrolysis
  • *Faster Oxidation Rates**

Clearance:

  • Non-Renal Elimination* –> VARIES
  • *Toxic metabolite accumulation may occur**
27
Q

Loading & Maintanence Doses
Dialysis Patients

A

Used for:
Drugs that are ELIMINATED from the body SLOWLY

Adjusted based on Vd –> gets drugs to TARGET levels

Maintanence doses MAY be Decreased
to keep them @ target
or LENGTHEN interval between doses

28
Q

Dialysis Clearance of Drugs

What is MORE LIKELY to be DIALYZED?

A

Small Molecular Weight

WATER SOLUBLE
highly protein bound –> less clearance
only the free drug –> crosses dialysis membrane

SMALL VD <1 L/kg
Lipid solubility, small vd = HIGHLY dialyzable

–> Supplemental Doses Required

29
Q

Peritoneal Dialysis

of DRUGS

A
  • MINIMAL DRUG REMOVAL*
  • if NOT removed by HD* = unlikely to be removed by PD

Dependent on:
MW / Solubility / degree of Ionization / Protein Binding / Vd
&
Peritoneal MEMBRANE (Negative Charged)
negative charged drugs = WONT BE DIALYZED OUT
drugs that are IONIZED @ phys pH –> diffuse SLOWER

30
Q

CRRT & Drug Removal

A

Dependent on:
Weight / Protein Binding / Vd / Dialysate-BloodFlow Rates

CVVH > CVVHDF > CVVHD
Highest rate of drug clearance

31
Q

Which Anti-Hypertensive Drugs are

Dialyzable? - Dose Afterwards?​

A

ACE-I

  • *Beta Blockers**
  • except CARvedelol / LABetalol*

HYDRALAZINE
DOSE AFTERWARDS, clonidine = not LIKELY also DA

Minoxidil

Midodrine
for HypoTensive

NOT
ARB / CCB / Clonidine

32
Q

Which ANTIBIOTICS are DIALYZABLE?

A
  • *= Dose Adjusted for Dialysis*
  • *All Yes = DOSE AFTERWARDS**

Amoxicillin*** & **Cephalexin*

Levofloxacin*** & **Ciprofloxacin*** & **Ofloxacin*

Mofloxacin = not

Sulfamethazole / Trimethoprim*

NOT DIALYZABLE:
Moxifloxacin / Doxycyclin / Tetracycline*
Clarithromycin* // Azi/erythromycin
Metronidazole* / clindamycin

33
Q

OTHER drugs to look out for DIALYSIS

A
  • *LITHIUM**
  • easily DIALYZED** = *low MW & water soluble
  • *PHENYTOIN**
  • *Vd is INCREASED** while ↓protein binding
  • *must monitor FREE LEVELS**

Meperidine
accumulates & may LOWER seizure threshold

Narcotics –> increase sensitivity for renal failure

RENAL VITAMINS –> DOSE AFTER DIALYSIS

PDAT3 (23 decks)

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