BOSTON – Just 1% of all surgical procedures are associated with complex surgical site infections, but many develop in association with ill-suited prophylactic antibiotic regimens, according to an analysis of more than 2.4 million American who underwent cardiac or orthopedic surgery during 2006-2009.
Nevertheless, "the vast majority [of surgery patients] don’t get SSIs. Do we want to modify treatment for all patients to address the small proportion who get complex SSIs?" asked Dr. Dale W. Bratzler.
The low overall rate of complex SSIs suggests that any changes to standard SSI prophylaxis regimens should proceed cautiously. "What we need most are strategies for identifying patients at high risk for SSI due to drug-resistant organisms for targeting modified antimicrobial prophylaxis regimens," said Dr. Bratzler, a professor in the department of health administration and policy of the University of Oklahoma, Oklahoma City.
The analysis he reported at the annual meeting of the Infectious Diseases Society of America used data from two large U.S. databases collected from January 2006 to December 2009. Information on the pathogen distribution of SSIs came from the National Healthcare Safety Network database of the Centers for Disease Control and Prevention, which included data from 1,389 U.S. hospitals during this period on the number and type of SSIs that occurred in patients who underwent coronary artery bypass grafting (CABG), and those who had primary total hip or total knee replacement surgery. The second database, from the Hospital Inpatient Quality Reporting Program of the Centers for Medicare and Medicaid Services, collected data on the type of antimicrobial prophylaxis received by patients who underwent these surgical procedures at 3,330 U.S. hospitals.
"Do we want to modify treatment for all patients to address the small proportion who get complex SSIs?"
The National Healthcare Safety Network data showed that a total of 3,024 patients developed a complex SSI among the 207,053 who underwent CABG (1.5%), and 3,532 patients had a complex SSI among the 495,529 patients who had primary hip or knee replacement surgery (0.7%), Dr. Bratzler reported. Complex SSIs were defined as either deep incisional infections, or infections of an organ or surgical space. Among the CABG-associated complex SSIs, 34% were caused by gram-negative bacteria, with the balance caused by gram-positive pathogens, and 17% of all SSIs involved methicillin-resistant Staphylococcus aureus (MRSA). In the arthroplasty patients, 18% of the complex SSIs involved a gram-negative pathogen, and 21% of all infections had MRSA involvement.
The data on type of antibiotic prophylaxis used showed that among 428,541 patients who underwent CABG in this dataset, 67% received "standard" prophylaxis with either cefazolin or cefuroxime; 12% received a regimen designed for patients with beta-lactam allergy with either vancomycin or clindamycin, plus an aminoglycoside added at the provider’s discretion; and 15% had prophylaxis with an extended-spectrum regimen consisting of either vancomycin plus cefazolin or cefuroxime, or an aminoglycoside plus cefazolin or cefuroxime. The remaining 6% of patients received another prophylaxis regimen.
The prophylaxis data for 2,007,162 arthroplasty patients showed that the standard regimen was used in 77%, the beta-lactam allergy regimen in 13%, and the extended-spectrum regimen in 7%, with the remaining 3% of patients receiving something else.
Dr. Bratzler then compared the expected efficacy of the three most commonly used regimens against the pattern of SSIs that actually occurred in these patients. Patients who received the standard regimen could expect protection against about 40% of the types of bacteria that actually wound up producing SSIs. Patients who received the beta-lactam allergy regimens could expect protection against 56%-96% of the pathogens that actually caused the SSIs, and patients who received the extended-spectrum regimens could expect protection against 69%-96%, he said.
The researchers could not do a more detailed analysis of the relationship between the type of prophylaxis used and the pattern of SSIs that subsequently developed because both databases were anonymous, which precluded cross-referencing the information.
Dr. Bratzler said that he had no disclosures.