| A |
guangyu |
1 |
8% |
| B |
aspire, milestogo, drshvetasm |
3 |
23% |
| C |
fd, lq2006, CocaCola, inkspot, khiladi, ansalshah, Justice, drafzalscotty, vijay1900 |
9 |
69% |
| D |
|
0 |
0% |
| Author | 4 Posts |
Justice
Forum Fanatic
Topics: 101
Posts: 1,970
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Please vote with your answer
Two years after undergoing mitral valve replacement, a 48-year-old man has a cerebrovascular accident. Except for fever, general physical examination is noncontributory. The cardiac examination is unchanged from previous findings. A transesophageal echocardiogram shows an oscillating mass on the mitral valve but no evidence of perivalvular extension or abscess. Six sets of blood cultures grow Enterococcus faecalis, which is resistant to penicillin and ampicillin but sensitive to vancomycin. The laboratory also reports the absence of high-level resistance to gentamicin and streptomycin.
A decision is made to treat medically, and the patient is begun on vancomycin, 1 g intravenously every 12 hours, and gentamicin, 80mg intravenously every 8 hours (the patient weighs 76kg [167 Ib). After 3 days of therapy, the laboratory reports that his vancomycin peak level is 32 μg/mL with a trough level
of 9 μg/mL, and his gentamicin peak level is 3.2 μg/mL with a trough level of 0.8 μg/mL. The technician notes that the vancomycin peak and trough levels and the gentamicin trough level are in the desirable range but that the laboratory’s therapeutic peak range for gentamicin is 4 to 8 μg/mL. Repeat blood cultures show no growth, and complete blood count and serum creatinine values are normal.
Which of the following is most appropriate at this time?
A. Increase the gentamicin dose; keep the vancomycin unchanged
B. Decrease the interval between the gentamicin doses; keep the vancomycin unchanged
C. Keep both the gentamicin and the vancomycin doses unchanged
D. Increase the vancomycin dose; keep the gentamicin unchanged
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| aspire
Forum Senior
Topics: 24
Posts: 158
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What is extended dosing method for aminoglycosides?
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| inkspot
Forum Guru
Topics: 26
Posts: 559
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justice are your poll questions for step 2 ? or step3 or IM boards - they are very difficult and im sure not for step2 . still keep them rolling in -- we are learning new things every day 
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| Justice
Forum Fanatic
Topics: 101
Posts: 1,970
|
The correct answer is C
Many laboratories test enterococci for high-level resistance against gentamicin and streptomycin. Lack of high-level resistance correlates with synergistic killing when the aminoglycoside is added to penicillin, ampicillin, or vancomycin (assuming that the bacteria are also sensitive to these agents). When gentamicin is used as synergistic therapy for gram-positive infections, the starting dose is only 1 mg/kg of body weight every 8 hours (with adjustments for obesity and renal function), and the goal is to obtain peak levels just over 3 ig/mL. This dose maximizes the clinical benefit while minimizing nephrotoxic side effects. Higher peak levels are considered ‘therapeutic” only when aminoglycosides are used to treat gram-negative rod infections. As with all aminoglycoside regimens, trough levels should be low to reduce the risk of toxicity. For this patient, no adjustment in either medication is necessary.
For the reasons discussed above, there is no reason to increase the gentamicin dose, despite being informed that the level is subtherapeutic according to the laboratory’s guidelines. Similarly, there is no reason to decrease the interval between gentamicin doses, which is another way to increase the total daily dose. The vancomycin levels are appropriate, and there is no reason to change that dose. The standard duration of treatment for prosthetic valve enterococcal endocarditis is 6 weeks of combination therapy, although a recent report questioned the need to continue the aminoglycoside beyond 2 weeks.
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