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GI and Renal Exam 1 > 12 - Nephrology in the Podiatric Patient > Flashcards

12 - Nephrology in the Podiatric Patient Flashcards

1
Q

What do you NEED to focus on for this lecture?

A
  • Appropriate dosing and adverse side effects of aminoglycosides.
  • Mechanism, risk factors and prevention of contrast induced renal failure.
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2
Q

What are the typical aminoglycosides used in podiatric medicine?

A
  • Gentamicin (Garamycin)
  • Tobramycin (Nebcin)
  • Amikacin (Amikin)

6 licensed in US, but these 3 have indications for LE infections

Gentamicin is used 90% of the time
- A lot of physicians shy away from this because there are fewer side effects and fewer renal impacts, but are a lot more expensive

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3
Q

What are the adverse reactions we see with aminoglycoside use?

A
  • Nephrotoxicity
  • Ototoxicity
  • Neuromuscular Blockade

Ototoxicity is IRREVERSIBLE ***

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4
Q

Describe the nephrotoxicity seen with aminoglycoside use

A
  • Most feared side effect***
  • Usually begins several days after therapy started - may begin sooner or after medication discontinued
  • First sign - increase in serum creatinine (but damage may already be done***)
  • Usually reversible
  • Increased risk when used with Vancomycin
  • Don’t combine gentamicin and vanco (nephrotoxicity is increased)
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5
Q

Describe the ototoxicity seen with aminoglycoside use

A
  • Most devastating side effect
  • Generally irreversible
  • Can manifest as auditory toxicity (feeling of fullness in ears, tinnitus, loss of acuity-high frequency)
  • Can manifest as vestibular toxicity (dizziness and nausea, poor balance)
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6
Q

Describe the neuromuscular blockade seen with aminoglycoside use

A
  • Excessive levels of antibiotic accumulate at neuromuscular junction which inhibits acetylcholine release and paralysis results.
  • Usually due to rapid administration via IV bolus

Aminoglycosides always infused over 30 minutes

Red man syndrome: massive histamine release

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7
Q

Describe the administration of aminoglycosides

A
  • All parenteral, not absorbed in stomach
  • Correlation between dosing and side effects
  • Patients that need aminoglycosides usually have many medical conditions
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8
Q

Describe the dosing of aminoglycosides

A

Aminoglycosides require a loading dose regardless of renal function

  • Gentamicin and Tobramycin - 2 mg/ kg
  • Amikacin - 7.5 mg/ kg

Maintenance dose is calculated based on renal function. Normal renal function:

  • Gentamicin and Tobramycin 3 - 5 mg/kg/day q 8 - 12 h
  • Amikacin 15 mg/kg/day q 12 h

So, loading dose is the SAME for everyone, but the maintenance dose is dependent on RENAL function ***

Don’t need to know the actual doses, but should know how it changes for renal function

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9
Q

How do you convert pounds to kg?

A

1 kg = 2.2 lbs ***

Need to know this for the exam

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10
Q

What is the cockcroft and gault formula?

A

Creatinine clearance = [(140-age) x weight in kg]/[serum creatinine x 72]

For women, multiply this by 0.85

Normal = 100% or 1.0

It is actually lean body mass, but we don’t test that in the hospital

NEED to know this for renal PBL*** (What impact does age have? What impact does weight have? - Renal function decreases as age increases)

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11
Q

How do you determine the peak and troughs for aminoglycosides?

A
  • Used to determine blood levels
  • Usually drawn after third dose
  • Peak drawn immediately after dose
  • Trough drawn 20-30 minutes before next dose
  • Peak is dose dependent
  • Trough is time dependent
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12
Q

What does peak depend on?

A

DOSE

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13
Q

What does trough depend on?

A

TIME

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14
Q

What should you do if the peak is high and the trough is normal?

A

Decrease the dose

Timing is okay

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15
Q

What should you do if the peak is low and the trough is normal?

A

Increase the dose

Timing is okay

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16
Q

What should you do if the peak is normal but the trough is high?

A

Increase the time (q12 hrs rather than q8 hrs)

Dose is okay

17
Q

What should you do if the peak is normal and the trough is low?

A

Decrease the time (q6 hrs rather than q8 hrs)

Dose is okay

18
Q

Describe the clinical use of aminoglycosides

A
  • Low cost, but safer agents are available
  • Severe gram negative infection or sepsis
  • Combination with a ß-lactam
  • Triple agent combination with a ß-lactam and antianaerobic agent for shotgun therapy for severe diabetic foot infection
19
Q

What is triple antibiotic combination?

A

Broad spectrum approach

  • Put a patient on one broad spectrum antibiotic initially
  • Once you identify the organism, then you narrow your focus

Triple antibiotic approach

  • The theory of triple antibiotic coverage (gram positive, gram negative, anarobe bacteria)
  • Then, based on your culture, you take them off what they don’t need
  • This way you never start a new antibiotic, you just take off what they don’t need
  • This is a cheaper method
  • Will need to pay attention to creatinine clearance with this method
20
Q

Describe a urinary tract infection in podiatric patients

Not on exam

A

NOT tested on this

  • Common cause of post-op fever
  • Usually occurs around 2 day
  • Check urinalysis for presence of leukocytes
  • Check CBC or take urine culture
  • Always check wound
21
Q

Describe a fever in the hospital

A 
Following urgery - Benign post-op fever (from anesthesia)
Day 1 - Wind (pneumonia)
Day 2 - Water (UTI)
Day 3 - Wound (post-op infection)
Day 4 - Walk (DVT)

Others: medications, constipation

22
Q

Describe radiographic contrast agents and ARF

A
  • Increases plasma volume
  • Osmotic diuresis
  • Increase in uric acid and oxalate excretion
  • ARF in 24-48h after diuresis in some patients
  • Creatinine peaks 3-5 days and returns to normal in 10-14 days
23
Q

Describe acute renal failure due to radiographic contrast agents

A
  • Pathology occurs in proximal tubule due to intra-tubular obstruction
  • Can lead to Acute tubular necrosis

Incidence
- 0-12%
-

24
Q

What are the risk factors for contrast induced ARF?

KNOW THESE

A
  • **Definite Risk Factors
  • Pre-existing renal insufficiency
  • Diabetes Mellitus
  • **Probable Risk Factors
  • Dehydration
  • Prior contrast induced ARF

Possible risk factors

  • Large contrast load
  • Advanced age
  • CHF
  • Vascular disease
  • Proteinuria
  • Hyperuricemia
25
Q

What is the incidence of ARF in diabetic patients

A

Normal Renal Function 0%

Moderate Renal Insufficiency 1.5-2.0 mg/dl –> 50-76%

Severe Renal Insufficiency > 4.5 mg/dl –> 92-100%

26
Q

Describe the treatment of contrast-induced ARF

A
  • Once ARF has developed, treatment is usually unsuccessful (with dialysis)
  • Emphasis placed on prevention (with hydration)
27
Q

How do you prevent contrast-induced ARF?

A
  • Identify patient at risk
  • Avoid study if feasible
  • Hydrate - does not really prevent, but may minimize severity***
  • Minimize contrast load
  • Avoid repeated studies
28
Q

Describe the study on the role of osmolality in the incidence of contrast-induced nephropathy

A
  • Level 2 – review of randomized controlled studies
  • 1365 patients
  • 16.8% incidence in nephropathy
  • Iso-osmolality and low-osmolality contrast showed no difference

Different types of contrast didn’t change risk of ARF

Their recommendation is to focus on HYDRATION***

Remember: hydrate, hydrate, hydrate***

GI and Renal Exam 1 (16 decks)

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