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“A critical weekly review of important new research findings for health-conscious readers”
PREVENTION OF SURGICAL SITE INFECTIONS
(SSIs) AFTER SURGERY
Infections following surgery in the United States occur in approximately 3 to 5 percent of all cases, and in more than 10 percent of certain types of operations. In view of these statistics, surgical site infections (SSIs) are a major public health problem throughout the world. On average, patients in the United States who develop an SSI will remain in the hospital for an additional week, resulting in an average of more than $25,000 in additional healthcare costs per affected patient. Patients who develop SSIs are also 60 percent more likely to be admitted to the ICU, and are twice as likely to die, when compared to patients who do not develop SSIs following surgery. Moreover, at a time when profound changes in the United State’s health care system are being proposed to control skyrocketing health care costs, SSIs are estimated to add an additional $10 billion in national health care costs, annually. In addition to the economic costs associated with SSIs, serious infections following surgery often cause considerable suffering among affected patients; and in severe cases, SSIs can also result in permanent disability or death.
The known causes of SSIs are complex and multiple and, therefore, no single or simple solution is capable of eliminating all cases of SSIs. However, there is ample research data available suggesting that a number of opportunities exist whereby the risk of SSIs can be further reduced. For example, one major (and preventable) cause of potentially life-threatening SSIs is the increasing prevalence of antibiotic-resistant strains of bacteria that have developed following decades of excessive and inappropriate antibiotic use. Among these resistant bacteria, few have raised more concern than methicillin-resistant Staphylococcus aureus (more commonly known by its acronym, MRSA). MRSA is capable of causing limb- and life-threatening infections, particularly in very ill patients, and in the very young and very old. When I began my medical career, more than 20 years ago, MRSA was an exceedingly rare cause of bacterial infections. When MRSA first began to appear, this bacterium primarily caused infections among seriously ill hospitalized patients, and was rarely a source of infection among generally healthy nonhospitalized patients.
In a landmark study by the Centers for Disease Control, and published in the Journal of the American Medical Association in 2007, a remarkable 58 percent of invasive infections caused by MRSA in 2004 and 2005 occurred in nonhospitalized patients, while 27 percent of MRSA infections arose among hospitalized patients. This tectonic shift in the epidemiology of MRSA (and other emerging strains of antibiotic-resistant bacteria and fungi, as well) has grave implications for preventing SSIs, as the majority of SSIs are known to arise from the surgical patient’s own native bacteria.
Two important new studies related to SSI prevention, and just published in The New England Journal of Medicine, offer important new ammunition in the ongoing fight against potentially deadly SSIs.
In the first study, from the Netherlands, patients being admitted to the hospital for elective surgery were tested for the presence of Staphylococcus aureus bacteria in their nasal passages. In this prospective, randomized, placebo-controlled, double-blind, multi-center clinical research trial, 6,771 patients were screened for the presence of nasal Staphylococcus aureus, and 1,251 of these patients were confirmed to be nasal carriers of this bacterium. A total of 917 of these patients were subsequently enrolled into this clinical research trial. These 917 patients were then divided into an “experimental” group and a “control” group, although neither the patients nor the research assistants in this double-blind study were permitted to know which group any patient was assigned to until after the study had been completed. Patients randomized to the “experimental” group were treated, before surgery, with antibacterial ointment (mupirocin) applied to their nasal passages, and with showers using antibacterial soap (chlorhexidine), in an effort to eradicate surface bacteria (including Staphylococcus aureus) from their noses and skin. The “control group” of patients received identical-appearing nasal ointment and skin soap, but without mupirocin or chlorhexidine.
All study patients were tracked following surgery, and the incidence of SSIs was then analyzed. In this highly-powered randomized, controlled clinical research trial, there was a 58 percent overall reduction in the relative risk of SSIs among the “experimental group” of patients when compared to the patients who received only placebo ointment and placebo soap. The benefit of preoperative treatment with mupirocin ointment and chlorhexidine soap was even more pronounced for SSIs involving deep body spaces, in this study: the relative risk of deep body space SSIs was reduced by 79 percent in the “experimental group” of patients. Therefore, the results of this powerful prospective clinical trial suggest that SSIs following elective surgery can be significantly reduced by, first, testing patients for evidence of colonization with Staphylococcus aureus bacteria and, secondly, by “decolonizing” the nasal passages and skin of already-colonized patients with antibacterial ointment and soap, respectively. Many hospitals already selectively apply nasal cavity testing for MRSA (either before or following surgery), and recommend a shower with chlorhexidine soap prior to surgery. The results of this important public health study suggest that the incidence of SSIs can probably be further lowered by more rigorous and more universal preoperative screening programs for nasal Staphylococcus aureus (including both MRSA and non-MRSA Staphylococcus aureus) directed at all patients who are undergoing elective surgery.
The second, and related, study evaluated the impact of two different preoperative skin prep solutions on the incidence of SSIs.
For decades, now, iodine-based skin cleansing solutions have been applied to skin surfaces just prior to the start of surgery, in an effort to kill skin-surface bacteria that can lead to SSIs. While these traditional iodine-based antibacterial skin prep solutions are active against many bacteria and fungi that are known to cause SSIs, their antibacterial and antifungal activity rapidly dissipates after being applied. Newer surgical skin prep agents that contain alcohol and chlorhexidine have been shown by recent research studies to not only have a wider spectrum of activity against skin bacteria and fungi than traditional iodine-based prep solutions, but these newer surgical prep solutions also sustain their antibacterial and antifungal activity over a much longer duration than their iodine-based counterparts. In this new prospective, randomized clinical research study, 849 patients undergoing elective surgery were randomized to one of two groups. One group of patient volunteers underwent preoperative skin preparation with a commercially available chlorhexidine-alcohol solution, while the second group was randomized to undergo skin preparation with the traditional povidone-iodine solution.
Following surgery, 16 percent of the patients who had their skin prepped with povidone-iodine solution developed SSIs within 30 days of surgery, while just under 10 percent of the patients who received the chlorhexidine-alcohol skin prep solution subsequently developed SSIs. (This 41 percent reduction in the relative risk of SSIs was found to be highly statistically significant.) Although use of the chlorhexidine-alcohol skin prep, alone, did not appear to protect against deep organ-space infections (when compared with the use of povidone-iodine skin prep solutions) in this study, both superficial and deep SSIs of the surgical incision were significantly reduced following use of the chlorhexidine-alcohol skin prep solution. In this study, the use of a chlorhexidine-alcohol prep solution cut the risk of superficial incisional infection by one-half, while deep incisional infections were reduced threefold. Thus, the use of chlorhexidine-alcohol skin prep solutions, just prior to making the incision, was associated with a highly significant reduction in the incidence of both superficial and deep infections of surgical incisions when compared to traditional iodine-based prep solutions.
Taken together, these two very important prospective randomized clinical research trials offer clinically valuable lessons for patients, physicians, and hospitals in our crucial quest to drive down the incidence of SSIs to the lowest achievable level. In view of the recent and ongoing emergence of highly virulent strains of bacteria and fungi that have become resistant to many of our most powerful antibiotic and antifungal drugs, respectively, it is imperative that we find new ways to reduce the risk of SSIs, and particularly new methods that do not involve the continued inappropriate or excessive utilization of broad spectrum antibiotic drugs.
If you are scheduled to undergo elective surgery in the near future, I would advocate that you share the findings of these two clinically important research studies with your surgeon (if they are not already aware of them).
Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author
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