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ACP HospitalistWeekly 7-15-09

Highlights

• New guidelines for treating S. aureus infections with vancomycin
• More patients surviving abdominal aortic aneurysm repairs

Perioperative medicine

• Perioperative diastolic dysfunction predicts vascular surgery outcomes

Annals of Internal Medicine

• Travel associated with threefold increase in VTE risk
• Missed test results: Overlooking CT findings
• Radiofrequency catheter ablation helps control afib symptoms in some patients

FDA update

• Drugs with propoxyphene must carry stronger warnings
• Boxed warning for varenicline, bupropion
• Arthroscopic shavers under safety review
• FDA approves arrhythmia, lung cancer maintenance drugs

Cartoon caption contest

• Put words in our mouth

Physician editor: A. Scott Keller, MD

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Highlights

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New guidelines for treating S. aureus infections with vancomycin

The Infectious Diseases Society of America, the American Society of Health-System Pharmacists, and the Society of Infectious Diseases Pharmacists released guidelines for the use of vancomycin in treating Staphylococcus aureus infections, including new recommendations for targeting and adjusting vancomycin therapy.

The guidelines were published online July 1 by Clinical Infectious Diseases. Recommendations include the following:

• Initial vancomycin dosages should be calculated based on actual body weight, including for obese patients, while subsequent dosage adjustments should be based on actual serum concentrations. Continuous infusion, as opposed to intermittent dosing, is unlikely to greatly improve outcomes.
• Trough serum vancomycin concentrations are the most accurate method of monitoring the drug's effectiveness, and should be obtained just before the fourth dose, at steady-state conditions.
• Trough serum vancomycin concentrations should always be maintained at >10 mg/L to avoid development of resistance. Concentrations of 15-20 mg/L are recommended.
• A patient should be thought to have vancomycin-induced nephrotoxicity if at least 2 or 3 consecutive high serum creatinine concentrations (increase of 0.5 mg/dL or >50% increase from baseline, whichever is greater) are documented after several days of therapy, and absent another explanation.
• Monitoring trough serum vancomycin concentrations to reduce nephrotoxicity is best suited for patients receiving aggressive dose targeting for sustained concentrations of 15-20 mg/L or those who are at risk of toxicity. It is also recommended for patients with unstable renal function and those receiving therapy for more than 3-5 days.
• Once weekly monitoring is recommended for hemodynamically stable patients whose goal trough is 15-20 mg/L.
• Evidence does not support monitoring of peak serum vancomycin levels.

The full text of the guidelines is online.

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More patients surviving abdominal aortic aneurysm repairs

Over the past few decades, survival rates have improved for repair of intact abdominal aortic aneurysms (AAAs), a new Swedish study found.

Researchers used data from the Swedish Vascular Registry to assess the outcomes of 8,663 intact AAA repairs and 4,171 ruptured repairs conducted between 1987 and 2005. Specifically, they looked at patients who received repairs from 1987 to 1999 versus those who got them between 2000 and 2005. Although patients in the later group were older, had more comorbidities and were more likely to have endovascular repair, those who underwent intact AAA repair were also more likely to survive for at least five years. The study was published online by Circulation on July 6.

Overall, survival for intact AAA repair (excluding 90-day mortality) was better for men than women, and for patients older than age 80 years, compared to the group as a whole. The octogenarians made up a small percentage of the whole and were probably required to be healthier to have the surgery, researchers noted. There was no difference in long-term survival depending on whether patients had open or endovascular repair. Patients who had a ruptured aneurysm did not experience any gain in long-term survival over the study period, and survived an average of 5.4 years compared to almost nine for intact repairs.

The improvements seen in intact repair survival could affect clinical decision making and cost-effectiveness calculations, such as on the value of screening for AAA, the study authors said. The researchers also noted that the rate of intact repairs is higher in North America than in Sweden, and that the study's results may not be entirely generalizable to other countries. However, the aneurysm registry could be a useful tool in guiding treatment of AAA, according to an accompanying editorial.

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Perioperative medicine

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Perioperative diastolic dysfunction predicts vascular surgery outcomes

Perioperative diastolic dysfunction independently predicts postoperative congestive heart failure (CHF) and prolonged length of stay after major vascular surgery, a new study found.

Researchers performed perioperative transesophageal echo (TEE) on 313 patients undergoing elective vascular surgery. Left ventricular diastolic function was assessed with transmitral flow propagation velocity (Vp), with Vp < 45 cm/s defined as abnormal. A left ventricular ejection fraction (LVEF) of < 40% constituted abnormal systolic function. Postoperative adverse outcome was defined as one or more adverse events, including myocardial infarction (MI), CHF, significant arrhythmia, prolonged intubation, renal failure and death. The study was published in the July Journal of Vascular Surgery.

While 8% of patients had isolated systolic dysfunction, 43% had isolated diastolic dysfunction, and 24% had both. Thirty percent of patients experienced at least one adverse outcome in the perioperative period, with CHF being the most common at 20%, and arrhythmia the second most common at 8%. Patients with abnormal diastolic function were twice as likely to have at least one adverse outcome (36% vs. 18%, P = 0.002), and a significantly longer length of stay (7 days vs. 5 days, P < 0.001), compared with patients with normal diastolic function. This difference was mostly due to increased CHF incidence. Systolic function didn't significantly predict adverse events or length of stay.

Past research has shown that more than 50% of geriatric patients undergoing surgery have preoperative diastolic dysfunction with normal LVEF, the study's authors noted. Until there is specific therapy for diastolic dysfunction, patients likely should continue with anti-ischemic rate control and diuretics, and avoidance of fluid overload. An accurate diagnosis is the first step toward developing a therapeutic strategy, they added. Additional studies are needed to determine the benefits of diastolic function assessment for preoperative risk stratification, as well as for goals for therapy.

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Annals of Internal Medicine

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Travel associated with threefold increase in VTE risk

Long-distance travel confers an increased risk for venous thromboembolism (VTE), but the extent of this risk has not been previously quantified. Researchers performed a meta-analysis of 14 studies involving 4,055 cases of VTE to investigate the association between travel and VTE for patients using any mode of transportation. Nontraveling persons were used as controls. The authors found that travel was associated with a nearly threefold higher risk of VTE, with a dose-response relationship of 18% higher risk for each two-hour increase in travel duration. Researchers should investigate the use of low-cost, low-risk interventions such as increased hydration and ambulation for all long-distance travelers, the authors concluded. Additional interventions and therapies should be evaluated for higher-risk subgroups, they wrote.

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Missed test results: Overlooking CT findings

Researchers studied the electronic health records of 4,112 patients and found 91 who had newly diagnosed abdominal aortic dilation observed on computed tomography (CT). Using the electronic medical record (EMR) as evidence, the authors found that the clinical care team had not noted the dilation in the EMR in 58% of cases within three months of CT. In 18% of cases, the dilations were never documented during an average follow-up of more than three years. The researchers found no evidence of patient harm associated with the failed documentation but concluded that innovative solutions are needed to ensure that physician awareness of abnormal test results is consistently noted in the medical record.

Click here for a summary of a study about how 7% of patients were not told about abnormal lab results from the June 30 issue of ACP InternistWeekly.

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Radiofrequency catheter ablation helps control afib symptoms in some patients

Although atrial fibrillation is the most common type of sustained arrhythmia, its symptoms are often uncontrolled with medical treatment. The authors performed a systematic review of 108 studies to determine the comparative effectiveness of radiofrequency catheter ablation for atrial fibrillation. They found that the procedure when performed after a failed drug course was more likely to maintain sinus rhythm than continuation of drug therapy alone. Lower strength evidence suggested that radiofrequency ablation improved quality of life, helped avoid anticoagulation and decreased readmission rates compared with medical treatment. Major adverse events were noted in fewer than 5% of patients who underwent the procedure. The authors noted that most of the included studies involved middle-aged adults with preserved left ventricular function and had short follow-up periods, usually a year or less. However, they concluded that radiofrequency catheter ablation is effective for rhythm control up to 12 months as second-line therapy for atrial fibrillation "in relatively young patients with near-intact cardiac function." They called for more extensive studies that used stroke and mortality as end points.

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FDA update

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Drugs with propoxyphene must carry stronger warnings

The FDA is requiring the manufacturers of drugs with propoxyphene (Darvon, Darvocet) to strengthen their labels, including boxed warnings, about potential overdose, and provide patient medication guides about proper use of the drugs, the agency said in a news release.

Physicians need to carefully review patients' histories before prescribing these drugs, and be aware of the risk of overdose at doses higher than recommended, the FDA said. The agency is requiring a new safety study to examine the effects of propoxyphene on the heart at higher-than-recommended doses, triggered in part by reports from Europe that the drug may be deadlier in overdose than other pain medications, the FDA said. An expert panel advised the FDA in January against continued marketing of propoxyphene products.

The FDA will also work with several groups, such as CMS and the Veterans Health Administration, to study how often the elderly are prescribed propoxyphene instead of other pain relievers, and the difference in the safety profiles of propoxyphene compared to other drugs, the agency said.

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Boxed warning for varenicline, bupropion

Smoking cessation drugs varenicline (Chantix) and bupropion (Zyban) must now have boxed warnings on their labels about the risk of serious mental health events, the FDA said in a release.

The events at issue include changes in behavior, depressed mood, hostility and suicidal thoughts. Similar information on mental health events will be required for bupropion marketed as the antidepressant Wellbutrin and for generic versions of bupropion—drugs that already carry a boxed warning for suicidal behavior in treating psychiatric disorders.

Providers who prescribe these drugs should monitor patients for any unusual changes in mood or behavior, the FDA said. In many reported cases, the problems began shortly after starting the medication and ended when the medication was stopped, though some people continued to have symptoms after stopping the medication.

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Arthroscopic shavers under safety review

The FDA is conducting a safety review of arthroscopic shavers in light of reports that pieces of tissue sometimes remain within the shaver, even after cleaning according to the manufacturer's instructions, the agency said in an alert.

Retained tissue in the shavers can compromise the sterilization process, and the FDA is working with manufacturers to gather more data, it said. The agency encourages facilities that use these devices to evaluate their cleaning procedures and, if retained tissue is discovered, to file a voluntary report with MedWatch, the FDA Safety Information and Adverse Reporting program online.

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FDA approves arrhythmia, lung cancer maintenance drugs

The FDA last week approved dronedarone (Multaq) to help maintain normal heart rhythms in patients with a history of atrial fibrillation or atrial flutter, according to a release.

Dronedarone is approved for patients whose hearts have returned to normal rhythm or who will undergo drug or electric-shock treatment to restore a normal heartbeat. Because the drug can cause critical adverse reactions, including death, in patients with recent severe heart failure, its label will contain a boxed warning against use in severe heart failure patients. The most common adverse reactions to dronedarone are diarrhea, nausea, vomiting, fatigue and loss of strength.

Separately, the agency also approved pemetrexed (Alimta), the first available drug for maintenance therapy of advanced or metastatic lung cancer, a release said.

Pemetrexed represents a new approach to treating advanced non-small-cell lung cancer, an FDA expert said. While patients whose tumors respond to chemotherapy do not usually receive further treatment after four to six chemotherapy cycles, research has shown a survival benefit in certain patients who received pemetrexed for maintenance therapy, he said. Reported adverse events included damage to blood cells, fatigue, nausea, loss of appetite, tingling or numbness in the hands and feet, and skin rash.

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Cartoon caption contest

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Put words in our mouth

ACP HospitalistWeekly wants readers to create captions for this cartoon and help choose the winner. Pen the winning caption and win a $50 gift certificate good toward any ACP product, program or service.

E-mail all entries to acphospitalist@acponline.org by July 22. ACP staff will choose three finalists and post them in the July 29 issue of ACP HospitalistWeekly for an online vote by readers. The winner will appear in the Aug. 5 edition of ACP HospitalistWeekly.

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