Bariatric Times - June 2008 - (Page 32)

32 Surgical Perspective Bariatric Times • June 2008 TABLE 1. Criteria for defining a surgical site infection (SSI) (Horan TC, et al.4) Superficial Incisional SSI Infection occurs within 30 days after the operations. Infection involves only skin or subcutaneous tissue of the incision and at least one of the following: 1. Purulent drainage, with or without laboratory confirmation, from the superficial incision. 2. Organisms isolated from an aseptically obtained culture of fluid or tissue from the superficial incision. 3. At least one of the following signs or symptoms of infection: pain or tenderness, localized swelling, redness, or heat and superficial incision is deliberately opened by surgeon, unless incision is culture-negative. 4. Diagnosis of superficial incisional SSI by the surgeon or attending physician. Do not report the following conditions as SSI: 1. Stitch abscess (minimal inflammation and discharge confined to the points of suture penetration). 2. Infection of an episiotomy or newborn circumcision site. 3. Infected burn wound. 4. Incisional SSI that extends into the fascial and muscle layers (see deep incisional SSI). Note: • Specific criteria are used for identifying infected episiotomy and circumcision sites and burn wounds. Deep Incisional SSI Infection occurs within 30 days after the operation if no implant is left in place or within one year if implant is in place and the infection appears to be related to the operation. Infection involves deep soft tissues of the incision and at least one of the following: 1. Purulent drainage from the deep incision but not from the organ/space component of the surgical site. 2. A deep incision spontaneously dehisces or is deliberately opened by a surgeon when the patient has at least one of the following signs or symptoms: fever (>38), localized pain, or tenderness, unless site is culture-negative. 3. An abscess or other evidence of infection involving the deep incision is found on direct examination, during reoperation, or by histopathologic or radiologic examination. 4. Diagnosis of a deep incisional SSI by a surgeon or attending physician. Notes: • Report infection that involves both superficial and deep incision sites as deep incisional SSI. • Report an organ/space SSI that drains through the incision as a deep incisional SSI. Organ/Space SSI Infection occurs within 30 days after the operation if no implant is left in place or within one year if implant is in place and the infection appears to be related to the operation. Infection involves any part of the anatomy (e.g., organs or spaces) other than the incision, which was opened or manipulated during an operation, and at least one of the following: 1. Purulent drainage from a drain that is placed through a stab wound into the organ/space. 2. Organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space. 3. An abscess or other evidence of infection involving the organ/space that is found on direct examination, during reporeration, or by histopathologic or radiologic examination. 4. Diagnosis of an organ/space SSI by a surgeon or attending physician. FIGURE 1. Cross section of abdominal wall showing CDC classifications of SSI.4 and non-obese patients undergoing major abdominal operations differs significantly. Specifically, they showed that obese patients had a suboptimal tissue oxygen tension at and near the incision intraoperatively and until postoperative Day 1. Even with oxygen supplementation during and after the procedure, suboptimal tissue oxygen tension persisted and a higher FiO2 was required to achieve the same PaO2 in obese patients than in non-obese patients.17 There is a growing body of evidence that would suggest that suboptimal wound tissue oxygen tension may in part explain the higher risk of SSI in obese patients. An important factor in surgical wound healing is the rate of collagen synthesis. Collagen provides tensile strength to the wound. Oxygenation of tissues is critical for the processes that constitute wound healing— angiogenesis, collagen synthesis, and epithelialization.18 Numerous studies have documented that postoperative pain, sedation, and atelectasis can exacerbate carbon dioxide retention and increase hypoxia in patients who are obese. Another mechanism contributing to SSI may be the tissue concentration of prophylactic antibiotic achieved in obese patients. Many studies have demonstrated the importance of antibiotic concentrations in serum and tissue during an operation.1 One such study noted a high rate of SSI in patients undergoing gastric bypass and recorded low serum concentrations of antibiotic in these patients. Doubling the dose of prophylactic antibiotic resulted in a significant decrease in the rate of SSI—16.5 percent versus 5.6 percent for 1g and 2g of preoperative cefazolin, respectively.1 Another welldesigned study noted that as BMI increased, there was a significant decrease in antibiotic concentration at closure in adipose tissue and at incision and closure in deep tissues (omentum). These studies would suggest that obese patients need substantially higher doses of prophylactic antibiotics to achieve therapeutic concentrations and adequate protection against SSI. Four general strategies have been proposed by Anaya and colleagues to prevent or decrease the risk of SSI in the obese—tight perioperative glucose control, optimizing tissue oxygen tension, larger doses of prophylactic antibiotics, and finally, performing laparoscopic operations whenever feasible. The stress response to surgery, which increases blood glucose levels, can cause hyperglycemia regardless of presence or absence of diabetes. Hyperglycemia impairs immunity, inhibits the inflammatory response, and interferes with collagen synthesis.18 Further, microvascular changes that result from sustained hyperglycemia may further impair tissue oxygenation. Some studies advocate the goal of achieving blood glucose levels below 200mg/dL. Insulin by infusion may be more effective postoperatively than the oral or injected route. Of course, such infusion would require close monitoring to prevent hypoglycemia, and that could present logistical difficulties. Some have suggested that oxygen saturation should be monitored for at least 24 hours after surgery by the use of pulse oximetry, given the close association between obesity and obstructive sleep apnea and the risk of rapid desaturation. However, further studies need to be done to corroborate this. Other groups have suggested that an oxygen

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Bariatric Times - June 2008 Endoluminal Treatment Options for Morbid Obesity: Devices and Techniques for Natural Orifice Approaches The Multidisciplinary Approach to Weight Loss: Defining the Roles of the Necessary Providers Acute Bleeding after Gastric Bypass Editorial Message Contents ASMBS: 25 Years Editorial Board Surgical Site Infection In The Morbidly Obese Patient: A Review Consultant's Corner The Link Between Sleep Loss and Obesity: Understanding the Mechanisms Responsible for Weight Gain with Sleep Deprivation Volume Matters Journal Watch Advertiser Index

Bariatric Times - June 2008

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