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257 Cards in this Set
- Front
- Back
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Conc. dependent antimicrobial killing
Definition |
amount of microbial killing depends on max concentration of drug above MIC
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Conc. dependent antimicrobial killing
PK/PD parameters |
Peak/MIC
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Conc. dependent antimicrobial killing
Examples |
Aminoglycosides
FQs Daptomycin Metronidazole |
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Time dependent antimicrobial killing
Definition |
amount of microbial killing depends on time drug stays above MIC
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Time dependent antimicrobial killing
PK/PD parameters |
T>MIC
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Time dependent antimicrobial killing
Examples |
B-lactams (PCNs, cephalosporins, carbapenems)
Macrolides (Azithro, Clarithro, Erythro) Linezolid Vancomycin Clindamycin |
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Post-antibiotic Effect (PAE)
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continued suppression of bacterial growth after a short exposure to antimicrobial agents
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Aminoglycosides PAE
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Gram negative
Moderate to prolonged (>/- 2 hrs) |
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Azithromycin PAE
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Gram + and Gram -
Moderate to prolonged (>/- 2 hrs) |
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Carbapenems PAE
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Gram +
minimal (0.5-2 hrs) (PAE against some Gram -) |
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Cephalosporins PAE
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Gram + minimal (0.5-2 hr)
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Clindamycin PAE
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Gram + and Gram -
Moderate to prolonged (>/- 2 hrs) |
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Daptomycin PAE
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Gram + Moderate to prolonged (>/- 2 hrs)
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FQs PAE
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Gram + and Gram -
Moderate to prolonged (>/- 2 hrs) |
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Linezolid PAE
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Gram + minimal (0.5-2 hr)
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PCNs PAE
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Gram + minimal (0.5-2 hr)
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Vancomycin PAE
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Gram + minimal (0.5-2 hr)
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Time-dependent and minimal PAE
Goal of therapy |
Maximize duration of exposure
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Time-dependent and minimal PAE
PK/PD Parameter |
T>MIC
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Time-dependent and minimal PAE
Antibiotics and activity spectrum |
Linezolid
PCNs Carbapenems Cephalosporins (All gram + activity) |
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Time-dependent and minimal PAE
Vancomycin (Goal, PK/PD parameters, spectrum) |
Maximize amount of drug
24 hr AUC/MIC gram + |
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Time-dependent and moderate to prolonged PAE
Goal of therapy |
Maximize amount of drug
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Time-dependent and moderate to prolonged PAE
PK/PD parameter |
24-hr AUC/MIC
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Time-dependent and moderate to prolonged PAE
Antibiotics and spectrum |
Clindamycin
Azithromycin (both have gram + and -) |
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Conc.-dependent and prolonged PAE
Goal of therapy |
Maximize concentration
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Conc.-dependent and prolonged PAE
PK/PD parameters |
Peak/MIC
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Conc.-dependent and prolonged PAE
Antibiotics and spectrum |
Aminoglycosides (gram -)
Daptomycin (gram +) FQs (gram + and -) |
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Examples of extended infusions
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Pip/Tazo
cefepime carbapenems |
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fT>MIC
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amount of time the free or non-protein bound drug concentration exceeds the MIC
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PK/PD parameter associated with extended infusions
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fT>MIC
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Near-maximal bactericidal effects when free drug conc. exceeds MIC for:
Cephalosporins |
60-70% of dosing interval
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Near-maximal bactericidal effects when free drug conc. exceeds MIC for:
PCNs |
50% of dosing interval
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Near-maximal bactericidal effects when free drug conc. exceeds MIC for:
Carbapenems |
40% of dosing interval
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Advantages of extended infusions
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superior pharmacodynamic profile (more fT>MIC)
allows for time between doses for admin. of drugs through same IV line cost savings |
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Reasons to use antibiotic combos
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1. broad-spectrum empiric therapy
2. polymicrobial infections 3. decrease resistance 4. decrease dose-related toxicity 5. increase inhibition or killing |
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Synergism
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significantly enhance inhibition or killing than either individually
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Mechanisms for synergistic action
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1. Blockade of sequential steps in a metabolic sequence
2. Inhibition of enzymatic inactivation 3. Enhancement of antibiotic uptake |
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How is bactrim synergistic?
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blocks sequential steps in metabolic sequence
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How is augmentin synergistic?
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Inhibition of enzymatic inactivation
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How is gentamycin/PCN synergistic?
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Enhancement of antibiotic uptake
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Antagonism
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Decreased inhibition or killing than either individually
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Mechanisms of antagonistic action
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1. Inhibition of cidal activity by static agents
2. Induction of enzymatic inactivations |
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How is linezolid given with vancomycin antagonistic?
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Inhibition of cidal activity (vanc) by static agents (linezolid)
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How is imipenem given with cefoxitin antagonistic?
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Induction of enzymatic inactivations
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Synergistic or antagonistic?
trimeth + sulfa |
synergistic
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Synergistic or antagonistic?
Amoxicillin + clavulanate |
synergistic
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Synergistic or antagonistic?
gentamycin + penicillin |
synergistic
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Synergistic or antagonistic?
linezolid + vancomycin |
antagonistic
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Synergistic or antagonistic?
imipenem + cefoxitin |
antagonistic
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Aminoglycoside coverage
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Gram -
Pseudomonas |
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Aminoglycoside toxicities
|
renal toxicity
ototoxicity |
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Aminoglycoside resistance
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gentamycin > vancomycin > amikacin
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Gent/tobra desired peak serum conc.:
uncomplicated lower UTI |
2-4 mcg/mL
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Gent/tobra desired peak serum conc.:
gram + endocarditis (synergistic with PCN) |
4-5 mcg/mL
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Gent/tobra desired peak serum conc.:
gram - infections (sepsis) |
6-8 mcg/mL
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Gent/tobra desired peak serum conc.:
gram - pneumonia |
8-10 mcg/mL
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Gent/tobra desired peak serum conc.:
gram - pneumonia with cystic fibrosis |
10-12 mcg/mL
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Gent/tobra desired trough serum conc.:
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< 1-2 mcg/mL
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High trough levels with aminoglycosides lead to...
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nephrotoxicity
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Low aminoglycoside trough levels
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Ok because drug with continue killing after dose is gone (PAE)
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Amikacin desired peak serum conc:
gram - infections (sepsis) |
20-30 mcg/mL
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Amikacin desired peak serum conc:
gram - pneumonia |
25-35 mcg/mL
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Amikacin desired trough serum conc
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< 5-10 mcg/mL
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When should you sample for aminoglycoside peak concentrations?
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0.5-1 hr after 30 minute infusion
If 1 hr infusion, draw within 15 minutes after end of infusion |
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Why can you not sample for peak serum concentrations immediately?
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must allow for adequate distribution
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When should you sample for aminoglycoside trough concentrations?
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</= 30 minutes before next dose
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When should you sample for aminoglycoside random concentrations when drawing after the first dose?
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Drawing after >/= one half life from peak concentration
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When should you sample for aminoglycoside random concentrations when drawing after dialysis?
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Wait 2 hours for redistribution
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Aminoglycoside ADEs/Toxicities
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1. Nephrotoxicity
2. Neurotoxicity 3. Ototoxicity |
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When does nephrotoxicity occur with aminoglycosides?
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Can occur within 4-5 days
Usually takes 5-10 days Highest risk with use > 10 days |
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When is nephrotoxicity risk with aminoglycoside use highest?
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Use > 10 days
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Urine output effects with aminoglycoside nephrotoxicity
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nonoliguric (normal urine production)
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Is aminoglycoside nephrotoxicity reversible?
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Mostly
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Which aminoglycoside is most likely to cause nephrotoxicity?
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Similar risk with all
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Average incidence of aminoglycoside nephrotoxicity
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~20%
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Risk factors for aminoglycoside nephrotoxicity
|
age
other disease states other nephrotoxic drugs |
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Symptoms of aminoglycoside neurotoxicity
|
muscle twitching
numbness seizures tingling |
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How does ototoxicity occur?
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damage to CN VIII
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Is aminoglycoside ototoxicity uni- or bi- lateral?
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Either
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When does aminoglycoside ototoxicity occur?
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Onset variable
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Incidence of aminoglycoside ototoxicity
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0.5-3%
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Types of ototoxicity
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Cochlear (hearing) or vestibular loss
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Symptoms of cochlear loss ototoxicity
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loss of hearing
tinnitus feeling of ear fullness |
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Is cochlear loss ototoxicity caused by aminoglycosides reversible?
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Usually
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Symptoms of vestibular loss ototoxicity
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vertigo
ataxia (lack muscle coordination) nystagmus (involuntary eye movement) dizziness N/V unsteadiness |
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Is vestibular loss ototoxicity caused by aminoglycosides reversible?
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Usually
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Aminoglycoside Drug-Drug Interactions
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amphotericin B
cisplatin cyclosporine furosemide skeletal muscle relaxants **due to possible additive nephrotoxicity |
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Aminoglycosides and Cyp450 interactions
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All AGs are renally excreted so don't have to worry about Cyp450 interactions
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Ascites/Pancreatitis and aminoglycosides
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Increase Vd >/= 25%
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Burns and aminoglycosides
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Increase clearance
Decrease half-life |
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Cancer and aminoglycosides
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Increase Vd
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Critically ill patients with sepsis and aminoglycosides
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Increase/decrease Vd and clearance
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Cystic fibrosis and aminoglycosides
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Increase Vd or clearance
Decrease half-life |
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Fever and aminoglycosides
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Increase clearance
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Hemodialysis/Peritoneal Dialysis and aminoglycosides
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Increase clearance
Decrease half-life |
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ICU and aminoglycosides
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Increase Vd 25-50%
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Post-op/ventilated patient and aminoglycosides
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Increase Vd
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Postpartum and aminoglycosides
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Increase Vd
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Surgery and aminoglycosides
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Increase Vd
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Speed of aminoglycoside distribution
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rapid
related to ICF |
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Aminoglycoside distribution in relation to protein binding
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low protein binding
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Aminoglycoside CSF penetration
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poor
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Aminoglycoside concentration in kidney, liver, lung
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high
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T/F. Aminoglycosides accumulate over time in the body.
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True
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What factors influence aminoglycoside distribution?
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Age
Weight Disease/conditions |
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% of aminoglycoside excreted by kidney
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95%
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Are aminoglycosides mostly excreted via kidney or liver?
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kidney
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Are aminoglycosides dialyzable?
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Yes
Need extra doses after dialysis because drug removed |
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Is aminoglycoside clearance affected by renal function?
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Yes
Can estimate GFR/CrCl by aminoglycoside clearance |
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What factors influence aminoglycoside clearance?
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Age
Disease/conditions |
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Usual PK population parameters used for dosing
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Clearance: based on age group average renal function
Vd Half-life and time to steady state |
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Factors that overestimate CrCl
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cachexia (physical wasting)
elderly liver disease CrCl < 20 mL/min |
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T/F. Unstable SCr can cause inaccurate CrCl results.
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True
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Factors that influence CrCl
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malnourishment/cachexia (physical wasting)
liver disease paralysis myasthenia gravis muscular dystrophy MS |
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What should be considered if blood concentration is extremely high?
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Question if concentration was drawn from infusion line
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What should be considered if blood concentrations are drawn sooner than 0.5 hr after the end of a 0.5 hr infusion?
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Drug may not be totally distributed
Ke and Cpeak will be overestimated Vd will be overestimated |
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When might Ke and Cpeak be overestimated?
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if blood concentrations are drawn sooner than 0.5 hr after the end of a 0.5 hr infusion
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When might Vd be overestimated?
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if blood concentrations are drawn sooner than 0.5 hr after the end of a 0.5 hr infusion
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What PK parameter may be inaccurate if blood concentrations not drawn at least one half-life apart?
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Ke
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Discrepancies in blood concentrations due to:
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CrCl estimation
patient variability from population Conc. not drawn at specified time Doses not charted/missed Doses not infused at time intended Doses inaccurately prepared |
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Gent/Tobra extended interval dosing based on IBW/ABW
|
7 mg/kg
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Amikacin extended interval dosing based on IBW/ABW
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15 mg/kg
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What body weight should be used for calculations if patient is obese?
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Adjusted BW
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What body weight should be used for calculations if patient is underweight?
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Actual BW
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Aminoglycoside extended interval dosing with CrCl >/= 60
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q24h
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Aminoglycoside extended interval dosing with CrCl 40-59
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q36h
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Aminoglycoside extended interval dosing with CrCl < 40
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Do not use extended interval dosing method
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Steps to determining extended interval AG dosing
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1. Calculate dose based on weight
2. Calculate CrCl 3. Determine dosing interval based on CrCl |
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When should random serum concentrations be drawn with extended interval AG dosing?
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6-14 hours after end of infusion (1 hr infusion)
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How is extended interval AG dosing frequency adjusted?
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Use Hartford nomogram
(graphs given on exam) |
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What should you do for extended AG dosing interval if point appears on line using Hartford nomogram?
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Choose longer interval
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What should you do for extended AG dosing interval if point appears off graph using Hartford nomogram?
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Stop next dose and follow levels to determine appropriate time of next dose
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Patient exclusions for extended interval AG dosing
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Peds
burns ascites dialysis cystic fibrosis ICU patients elderly UTI treatment endocarditis osteomyelitis |
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Rationale for extended interval AG dosing
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1. conc-dependent bactericidal activity
2. relationship b/w peak/MIC ratio and patient outcome 3. PAE 4. traditional dosing often leads to low efficacy and significant toxicity 5. less frequent dosing and monitoring 6. less accumulation |
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T/F.
More AG accumulation occurs with extended interval AG dosing/ |
False
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T/F.
Less monitoring is necessary with extended interval AG dosing. |
True
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Oral vancomycin absorption
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Insignificant with capsules/oral solution (except with colitis)
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When is oral vancomycin appropriate? Why?
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with colitis (PC)
PC-> inflammation/destruction of mucosal integrity -> increase systemic absorption |
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Vancomycin distribution into body
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distributes widely into body tissues
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Where all does vancomycin distribute?
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pericardial, pleural, ascitic, synovial, bile, lung, lymph, feces
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Vancomycin distribution with inflamed meninges
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15% serum conc.
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Vancomycin distribution with un-inflamed meninges
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minimal penetration
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PK model used for vancomycin dosing
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One-compartment model
(although 2-comp. more realistic) |
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Vancomycin half life first distribution vs. second distribution
|
first distribution: 0.1-0.4 hr
second distribution: 0.5-3.6 hr |
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Vancomycin elimination half life
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4-8 hrs in adults with normal renal function
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Vancomycin Vd calculation based on what body weight?
|
TBW (ABW if obese)
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Does vancomycin Vd increase or decrease in obese patients?
|
decrease
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Vancomycin bound to albumin
|
50-60%
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vancomycin metabolism
|
minimal
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How does hepatic disease affect vancomycin metabolism/kinetics?
|
Does not really affect
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How much vancomycin is recovered in urine?
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80-100% IV dose in 24 hrs in normal adults
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Can you use vancomycin excretion to estimate CrCl?
|
No
clearance is proportional (some reabsorption/secretion) |
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What is the basis for vancomycin dosing nomograms?
|
CrCl
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How much vancomycin is removed by HD/CAPD?
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minimal removal
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Vancomycin concentrations after dialysis
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Large rebound effect to original conc. pre-dialysis anticipated in hours after dialysis
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How long might anuric (no urine) patients have elimination half life?
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Up to 7 days
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Who may have increase vancomycin clearance?
|
obese
peds burn pts |
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Vancomycin PK parameters in elderly
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Increase half life
Increase Vd Decrease clearance (not correlated to CrCl) |
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Vancomycin ADEs/toxicities
|
1. Nephrotoxicity
2. Ototoxicity 3. Red Man Syndrome 4. Thrombophlebitis |
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What is vancomycin nephrotoxicity most likely due to?
|
impure formulation
being combined with AGs (additive nephrotoxic effects) |
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What was vancomycin nephrotoxicity originally attributed to?
|
high troughs (>10-20 mcg/mL)
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Vancomycin ototoxicity incidence
|
unclear/rare
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What is vancomycin ototoxicity associated with?
|
high peaks > 50-80 mcg/mL
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What may cause red man syndrome?
|
fast vancomycin infusion
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What type of reaction is red man syndrome?
|
histamine-mediated response
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Symptoms of red man syndrome
|
redness
pruritis of upper torso, arms, neck |
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What can be given/done to help prevent red man syndrome?
|
diphenhydramine 30 min. before infusion
slow infusion rate |
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Vancomycin thrombophlebitis incidence
|
rare
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T/F.
Vancomycin thrombophlebitis is related to serum conc. |
False
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Renal dysfunction effects on vancomycin
|
Decrease clearance
|
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Burns effects on vancomycin
|
Increase GFR
Increase clearance Decrease half life |
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Obesity (>30% over IBW) effects on vancomycin
|
Increase clearance
Decrease half life |
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What serum concentrations are usually drawn with vancomycin?
|
mostly only see troughs drawn
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When should peak and troughs be drawn with vancomycin?
|
At time of steady state
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How long before you should draw vancomycin peaks?
|
>/= 1-2 hrs after end of infusion
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Why wait to check vancomycin peak?
|
Avoid distributive phase which may result in erroneous calculations
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How long before you should draw vancomycin troughs?
|
< 1hr before next dose
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How long before you should draw vancomycin random levels?
|
>/= one half life from previous levels
(ensures accuracy when calculating Ke) |
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Vancomycin dosing by weight for normal adults
|
15 mg/kg q12h
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Vancomycin dosing by weight for renal patients
|
20 mg/kg LD + 15 mg/kg dose based on CrCl
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Vancomycin dosing interval with CrCl >70
|
q12h
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Vancomycin dosing interval with CrCl 40-70
|
q24h
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Vancomycin dosing interval with CrCl 30-40
|
q48h
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Vancomycin dosing interval with CrCl 20-30
|
q72h
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Vancomycin dosing interval with CrCl <10
|
q5-7days
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How long should you wait between vancomycin LD and MD?
|
Wait length of dosing interval
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Vancomycin Intrathecal dosing
|
10-20 mg/24hr
|
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Vancomycin Intrathecal dosing in children
|
10 mg/24hr
|
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Vancomycin intraventricular dosing
|
5 mg/24 hr
Up to 20 mg q24h if fail to eradicate |
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Vancomycin intraventricular dosing in infants
|
5-10 mg/24hr
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Vancomycin dosing in children (<12 yo)
|
15 mg/kg q8h
|
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Vancomycin dosing in neonates
|
Varies based on post-conceptual age
|
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Goal vancomycin peak
|
20-35 mcg/mL
|
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Goal vancomycin trough
|
10-20 mcg/mL
|
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Vancomycin peak recommendations
|
Keep peak conc. ~8x MIC
|
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Vancomycin trough recommendations
|
Keep trough conc. 2-3x MIC for duration of interval
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What is dialysis?
|
Process where substances move by concentration gradient across semi-permeable membrane
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What substance pass into dialysis fluid?
|
Substances small enough to pass through semi-permeable membrane pores can pass out of blood into dialysis fluid
|
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What happens once substances are in dialysis fluid?
|
Waste products/other compounds can be removed from the body
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Why might dialysis be used to remove drugs from circulation?
|
drug overdose
experiencing severe ADEs |
|
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T/F.
Drugs are removed primarily in dialysis. |
False
drugs mostly removed from body coincidental to removal of toxic waste |
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When is supplemental dosing post-dialysis necessary?
|
When there is significant dialysis clearance of the drug
|
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What are the 2 processes involved with dialysis?
|
Diffusion and ultrafiltration
|
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What is diffusion?
|
Concentration gradient
substance goes from high to low conc. |
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What is ultrafiltration?
|
water being pulled off
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What leads to higher filter efficiency is dialysis? What does this correlate with?
|
increased surface area -> higher filter efficiency (flow rate of dialysate)
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What drug characteristics affect dialysis removal?
|
Molecular weight
Water solubility/Lipid solubility Plasma protein binding Vd Inherent clearance (rate and route) |
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What about molecular weight influences dialysis clearance?
|
Molecular size vs. semipermeable membrance pore size
|
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Small drug molecules (<500 daltons) and dialysis
Examples? |
readily eliminated by dialysis
Ex. lidocaine, procainamide, theophylline |
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Moderate drug molecules (500-1000 daltons) and dialysis
Examples? |
Decreased ability to pass
Many of these drugs still require post-dialysis replacement doses Ex. aminoglycosides, digoxin |
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Large molecules (>1000 daltons) and dialysis
Examples? |
not significantly removed
can be removed in high-flux filters Ex. vancomycin |
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In regards to molecular weight, what size is vancomycin?
|
Large molecule (>1000 daltons)
|
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In regards to molecular weight, what size are aminoglycosides?
|
Moderate (500-1000 daltons)
|
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In regards to molecular weight, what size is digoxin?
|
Moderate (500-1000 daltons)
|
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In regards to molecular weight, what size is lidocaine?
|
Small (<500 daltons)
|
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In regards to molecular weight, what size is procainamide?
|
Small (<500 daltons)
|
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In regards to molecular weight, what size is theophylline?
|
Small (<500 daltons)
|
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High water soluble drugs and dialysis
|
Partition into water based dialysis fluid
|
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High lipid soluble drugs and dialysis
|
Remain in blood
|
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Unbound drugs and dialysis
|
Unbound drug able to pass through membrane pores
|
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What types of protein bound drugs are most likely to have a better dialysis clearance?
|
Drugs not highly protein bound have a high free fraction of drug in blood prone to better dialysis clearance
|
|
|
High Vd (>2L/kg) and dialysis
Why? |
Less likely to be removed by dialysis
mostly located at tissue binding sites and not in blood |
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Low Vd (<1 L/kg) and dialysis
|
more likely to be removed by dialysis
|
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Renal elimination of drug and dialysis
|
If kidney is primary rout of elimination, increased likelihood drug will be removed by dialysis
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HD
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Hemodialysis
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CAPD
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continuous ambulatory peritoneal dialysis
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CVVH
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continuous venovenous hemofiltration
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CCPD
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continuous cyclic peritoneal dialysis
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CAVH
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continuous arteriovenous hemofiltration
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CAVHD
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CAVH (continuous arteriovenous hemofiltration) with dialysis
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What dialysis technique(s) are most common?
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HD
CAPD CVVH |
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Differences in dialysis techniques
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indication and clinical condition
delivery system filter flow rate (blood and dialysis) duration |
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How is peritoneal dialysis performed?
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catheter surgically inserted into lower abdomen into peritoneal cavity
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How much dialysis fluid is given with peritoneal dialysis?
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1-3L
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What happens when dialysis fluid is given with peritoneal dialysis?
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Given via catheter, waste products move from blood vessels of peritoneal membrane (semipermeable) into dialysis fluid via concentration gradient
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Is dialysis fluid continuously or periodically removed with peritoneal dialysis?
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periodically
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Which more effectively removes drug from body: peritoneal dialysis or HD?
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HD
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T/F.
Drugs can be added to peritoneal dialysis fluid. |
True
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What happens if drug added to dialysis fluid is absorbed into the body?
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systemic effects may occur
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What infection is common with peritoneal dialysis?
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peritonitis
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How are antibiotics given to treat peritonitis with peritoneal dialysis?
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Antibiotics administered intraperitoneally for local treatment of infection using dialysis fluid as delivery vehicle
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What is used for the delivery vehicle of antibiotics for use during peritoneal dialysis?
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dialysis fluid
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GFR with peritoneal dialysis (CAPD)
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10-20 mL/min
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Is removal of fluids and solutes continuous or periodical with cont. renal replacement dialysis (CAVH, CVVH)?
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continuous
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Which dialysis methods remove larger molecules?
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CAVH, CVVH (cont. renal replacement dialysis)
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T/F.
Both bound and unbound drug portion is removed with CAVH and CVVH. |
False.
Only unbound drug portion is removed |
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GFR with CAVH/CVVH
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~30 mL/min (depending on filter)
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Rate at which blood is pumped out during HD
How is it pumped out? |
blood pumped out of patient at 300-400 mL/min through one side of semi-permeable membrane of articifical kidney by HD machine
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What happens to cleansed blood during HD?
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pumped back into vascular system
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Is HD fluid electrolyte and/or osmotically balanced?
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Both
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How does ultrafiltration occur during HD?
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by adding solutes to increase osmolarity of dialysis fluid relative to blood, it's possible to remove fluid from body by osmotic pressure across semi-permeable membrane of artificial kidney
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HD: high or low flux filters
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low
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How often is HD performed?
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3-4 hrs three times a week
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Pre-distribution
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If drug given too close/during HD, expect larger removal of dose
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If drug given too close/during HD, expect larger or smaller removal of dose?
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larger
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Post-distribution
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rebound in serum concentration can occur after end of HD
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Why does post-distribution occur?
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Due to differences in rate of transfer of drug between tissue and vascular compartments
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