Editor’s Note: Welcome to Prescience, a blog focused on the science of surgical site infection (SSI). Since Prescient Surgical was founded to explore the potential benefits of surgical wound irrigation, I thought this would be an excellent first topic to explore. To that end, I invited Prescient Surgical’s Co-founders, Dr. Insoo Suh and Dr. Mark Welton, to provide some grounding context and present an overview of the literature on surgical wound irrigation.
Surgical Wound infection: A “perfect storm”
As is the case with many clinical problems, wound infection is a multifactorial disease with numerous identified risk factors. However, as Cheadle (2006) details in an informative review, these risk factors can be broken down into three broad categories (1):
- The patient. It is well-established that a patient’s underlying medical condition affects the risk of developing surgical complications including wound infection. Pre-existing medical conditions such as advanced age, poor nutritional status, diabetes, coronary artery disease, obesity, and previous abdominal surgery and/or irradiation have clearly been demonstrated to increase the likelihood of wound infection in surgical patients. A patient’s inherent immune status also directly affects the ability of a wound to fight off infection and properly heal. Although important, these risk factors as a whole are generally secondary to the fundamental mechanisms causing wound infection. In addition, these comorbidities are inherent to the makeup of the patient, and are therefore less amenable to significant improvement in a short time frame (other than making sure that they do not significantly worsen in the perioperative period).
- The microbe. By definition, a wound infection requires the presence of a responsible invasive organism, usually bacterial; therefore, the type of microbe that contaminates the wound edges is perhaps the most fundamental factor in the development of wound infection. Generally, wound infections from “clean” operations (those that do not violate the aerodigestive tract) are due to organisms that normally reside on the skin, such as Staphylococcus and Streptococcus species. On the other hand, operations that violate the GI tract (such as colorectal surgery) release millions of fecal organisms (E. coli, Klebsiella, Proteus, etc.), which are then responsible for the majority of wound infections in these procedures. As detailed below, antibiotics represent an active strategy to counteract and destroy bacteria.
- The operation. The setting in which the potential inciting events for wound infection occur is also profoundly important. Factors that either increase the patient’s physiologic stress response (e.g. tissue ischemia, increased blood loss, inadvertent hypothermia, etc.) or increase the exposure of the wound to the possibility of contamination (e.g. longer operative time, increased incision length, improper skin prep/sterilization, operations that expose the wound to contaminating intestinal contents, etc.) are known to increase the likelihood of wound infection. Some of these factors are highly dependent on the technical prowess of the individual surgeon or the inherent difficulty of the operative task, and are therefore difficult to control. However, some factors – namely, contact contamination – are critical factors that can be modified and improved through a standardized approach.