Journal watch: recent studies of note

Recent studies of note.

Catheter retention raises risk for recurrent staph infection

Retention of the central venous catheter (CVC) in patients with coagulase-negative staphylococcal bacteremia did not affect resolution of the infection but was a significant risk factor for recurrence, a recent study found.

Researchers retrospectively evaluated 188 patients with coagulase-negative staphylococcal bacteremia using CDC criteria of two positive blood cultures and found that resolution of infection within 48 hours of antimicrobial therapy occurred in 93% of patients and was not affected by CVC removal or exchange versus retention.

Using multiple logistic regression analysis, researchers found infections were less likely to resolve in patients with previous ICU stays and those who had other concurrent infection sites. Duration of therapy did not affect recurrence, but patients with catheter retention were 6.6 times more likely to have a recurrence than those who had catheters removed or exchanged. The study also found that infusion ports causing CVC-related infections were associated with recurrences. The findings appeared in the Oct. 15 Clinical Infectious Diseases.

Infectious Diseases Society of America guidelines recommend that systemic antibiotic therapy be prolonged to at least 10 days if a CVC is retained, the authors noted. However, data from this study show that prolonged treatment was not associated with better resolution of infection or significantly lower recurrence rate.

More research is needed to determine the efficacy of salvage interventions in cases where CVC removal is not possible, such as in patients with limited vascular access, the authors said.

ICD soon after heart attack doesn't help survival

Patients who received an implantable cardioverter-defibrillator (ICD) within 40 days after a myocardial infarction had no better survival than those who were treated with medical therapy alone, a new study found.

The randomized, prospective trial included 898 patients with a recent myocardial infarction (MI) who had a reduced left ventricular ejection fraction (≤40%) and either a heart rate of 90 or more beats per minute on the first available electrocardiogram or nonsustained ventricular tachycardia during Holter monitoring or both. Of those patients, 445 were randomly assigned to receive an ICD and 453 were assigned to medical therapy only. After a mean follow-up of 37 months, the groups had no significant difference in overall mortality: 116 patients in the ICD group died compared to 117 in the other group. The ICD patients had a reduced risk of sudden cardiac death (hazard ratio [HR], 0.55; P=0.049), but an increased risk of non-sudden cardiac death (HR, 1.92; P=0.001).

The study's results confirmed the findings of the Defibrillator in Acute Myocardial Infarction Trial (DINAMIT) and offered no evidence that implantation of an ICD improved survival in this high-risk group of patients who were receiving optimal medical therapy, the authors concluded. They speculated that the increase in non-sudden cardiac deaths could be due to untoward effects of the ICD shocks, the substrate of MI studied, other effects of the ICD, or differences in the use of other therapies, but said that further research would be required to determine which factor is responsible.

The study, published in the Oct. 8 New England Journal of Medicine, shows the value of confirmatory trials in comparative effectiveness research, an accompanying editorial noted.

High oxygen levels during abdominal surgery do not lower infection risk

Administering high levels of oxygen during abdominal surgery does not lower the risk of surgical site infection, according to a recent trial.

Researchers randomly assigned 1,400 patients undergoing acute or elective laparotomy to receive either 80% or 30% oxygen during and for two hours following surgery. There were no significant differences in the number of surgical site infections (19.1% in the 80% group vs. 20.1% in the 30% group), pulmonary complications or mortality between the two groups. The results were published in the Oct. 14 Journal of the American Medical Association.

Previous trials have suggested that high oxygen levels may be effective in preventing surgical wound infections, noted an accompanying editorial. However, fluid volumes administered in this trial were smaller than in previous studies and normothermia was not maintained in all patients. Because these factors raise the possibility of vasoconstriction, the editorialist said, the current study would have been stronger if researchers had measured wound partial pressure of oxygen in order to show that supplementary oxygen reached the wounds.

The current findings inform the debate over whether high levels of oxygen can prevent infections, the editorial continued, but more research is needed before the practice becomes standard. For now, physicians should focus on ensuring rigorous perioperative care, including adequate fluid administration, maintenance of normothermia and normoglycemia, and appropriate use of perioperative antimicrobial agents.

Don't base benchmarks on incomplete data

Including only patients who died in studies of resource use results in misleading data, according to a recent study.

The study included 3,999 patients hospitalized for heart failure at six California teaching hospitals between 2001 and 2005. By including all admitted patients, as opposed to only those who died, researchers were able to identify differences in outcomes. The variation in resource use among hospitals was 27% to 44% less than observed in studies that analyzed only patients who died, and hospitals that used the most resources had the lowest mortality rates. The results appear in the November 2009 Circulation: Cardiovascular Quality and Outcomes.

Previous studies that have used the “looking back” method, including only expired patients, have two serious shortcomings, the authors said. The method does not take into account the possibility that resource-intensive care may improve outcomes because all outcomes are 100% mortality. In addition, this method misses the possibility that some hospitals may selectively direct resources based on which patients are most likely to benefit.

The findings have important implications because “looking back” studies have been used to set performance benchmarks, the authors noted. While this study does not mean that there is a causal relationship between higher resource use and better outcomes, it suggests that more study is needed about how resource use during initial hospitalization influences outcomes, the authors said.

Additional evidence supports longer window for tPA after stroke

Additional evidence supports a longer time window for use of tissue plasminogen activator (tPA) after acute ischemic stroke, according to a recent report.

The standard time window for thrombolytic therapy after acute ischemic stroke is three hours. Last year, the European Cooperative Acute Stroke Study III (ECASS III) found that the time window could be safely extended to 4.5 hours. The authors of that study recently performed additional secondary analyses to confirm their findings. They looked at functional end points at day 90 or day 30, treatment response, symptomatic intracranial hemorrhage and death. Their results were published in December's The Lancet Neurology.

In ECASS III, 418 patients received tPA and 403 received placebo. All of the additional end points studied showed at least a trend in favor of tPA. tPA more than three hours after stroke onset was effective in older patients (odds ratios, 1.61 [95% CI, 1.05 to 2.48] for patients <65 years of age and 1.15 [95% CI, 0.80 to 1.64] for those ≥65 years of age; P=0.230) and across all ranges of stroke severity (odds ratios, 1.28 [CI, 0.84 to 1.96] for a National Institutes of Health stroke scale [NIHSS] score of 0 to 9, 1.16 [CI, 0.73 to 1.84] for an NIHSS score of 10 to 19, and 2.32 [CI, 0.61 to 8.90] for an NIHSS score of ≥20; P= 0.631). Incidence of symptomatic intracranial hemorrhage seemed to be unrelated to previous antiplatelet use or time from symptom onset to treatment. The study was funded by Boehringer Ingelheim.

The authors concluded that their results provide further support for an extended time window for tPA in patients with acute ischemic stroke but warned that “time remains critical and fast treatment still provides the greatest chance of recovery.” An accompanying editorial congratulated the ECASS III investigators on their study but pointed out that additional evidence is needed for patients with diabetes and previous stroke, patients older than 80 years, and patients with severe stroke. “Any physician who chooses to treat patients between 3.0 and 4.5 hours after stroke onset should adhere carefully to the ECASS III exclusion and inclusion criteria, and do so without delay,” the editorialist wrote.

PE and DVT after trauma may not be related

Pulmonary embolism in trauma patients may originate in the lungs, contrary to the commonly held belief that it is triggered by deep venous thrombosis of the pelvis and lower extremities, a recent study found.

Researchers retrospectively reviewed records over a three-year period of trauma patients who underwent computed tomographic pulmonary angiography with computed tomographic venography (CTV) of the pelvic and proximal lower extremity veins. Of the 247 patients studied, pulmonary embolism (PE) was diagnosed in 19% and deep venous thrombosis (DVT) in 7%, and seven patients (3%) with PE had DVT. No significant differences were noted between patients with PE who had DVT and those who did not. The study was published in the October 2009 Archives of Surgery.

The results are contrary to the common belief that PE and DVT are related, the authors said. The latest findings have important clinical implications because the development of vena cava filters was based on the theory that PE and DVT coexist, they said. The authors theorize that many PEs form primarily in the lungs and that their findings should prompt reconsideration of the risks and benefits of vena cava filters.

However, an accompanying critique stated that the authors' theory is not supported by the data. The study relies on the results of CTV screening for diagnosis but there is no control comparison. In addition, the critique noted, the authors did not report when patients with PE were screened for DVT and did not explain how new clots would form in the lungs. Future research should focus on differences in clot formation and endothelial response in extremity veins and the lungs in order to explain the temporal relationship between DVT and PE, the critique concluded.