Sternotomy infection: poor prediction by acute phase response and delayed hypersensitivity

The impact of surgical site occurrences and the role of closed incision negative pressure therapy

Surgical site occurrences are observed in up to 60% of inpatient surgical procedures in industrialised countries. The most relevant postoperative complication is surgical site infection (SSI) because of its impact on patient outcomes and enormous treatment costs. Literature reviews ('SSI', 'deep sternal wound infections' (DSWI), 'closed incision negative pressure wound therapy' (ciNPT) were performed by electronically searching MEDLINE (PubMed) and subsequently using a 'snowball' method of continued searches of the references in the identified publications. Search criteria included publications in all languages, various study types and publication in a peer-reviewed journal. The SSI literature search identified 1325, the DSWI search 590 and the ciNPT search 103 publications that fulfilled the search criteria. Patient-related SSI risk factors (diabetes mellitus, obesity, smoking, hypertension, female gender) and operation-related SSI risk factors (re-exploration, emergency operations, prolonged ventilation, prolonged operation duration) exist. We found that patient- and operation-related SSI risk factors were often different for each speciality and/or operative procedure. Based on the evidence, we found that high-risk incisions (sternotomy and incisions in extremities after high-energy open trauma) are principally recommended for ciNPT use. In 'lower'-risk incisions, the addition of patient-related or operation-related risk factors justifies the application of ciNPT.

Cultures of sternal wound and mediastinum taken at the end of heart surgery do not predict postsurgical mediastinitis

The aim of the study was to assess of the role of intraoperative cultures taken at the end of major heart surgery (MHS) in the prediction of postoperative mediastinitis (PM) in patients undergoing MHS over a 6-month period in a tertiary university hospital. Just before wound closure, a sample of the sternal border was taken, swabbing back and forth the sternal border and the subcutaneous tissues. A second sample was taken after irrigation of the deep mediastinal structures with 10 mL of Ringer lactate. Swabs were processed semiquantitatively and the mediastinal fluid with a quantitative technique. The observation of one or more colonies per plate was considered a positive culture. Cultures obtained at the end of 229 surgical interventions (227 patients) were positive with the semiquantitative or with the quantitative procedures in 31.0% (95% confidence interval [CI], 25.1-37.4%) and 34.5% (95% CI, 28.4-41.0%) of the times, respectively (P = NS). The number of microorganisms isolated in the wound swab or mediastinal fluid was 91 and 110, respectively. Of the 227 patients, 7 developed an episode of PM (3.1%; 95% CI, 1.2-6.2%) after a median time of 11 days (range, 5-19 days). The microorganisms causing the 7 cases of mediastinitis were not isolated in the intraoperative cultures in any of the cases. The value of intraoperative cultures as a test for prediction of PM depending on the breakpoint chosen were as follows: sensitivity (0%), specificity (66.2-97.3%), and positive (0%) and negative predictive values (96.8-98.0%). We recommend against surveillance cultures taken intraoperatively in patients undergoing MHS.

Plastron-trapdoor technique for direct-vision sternal re-entry

Repeat median sternotomy does not allow good access for retrosternal re-entry. Conversely, by using the plastron-trapdoor technique, which we describe in this report, the retrosternal tissues are dissected from the body of the sternum under direct vision, thus allowing relatively safe and wide exposure for retrosternal re-entry.

A risk index for sternal surgical wound infection after cardiovascular surgery

OBJECTIVES

To identify factors that increase the risk of sternal surgical wound infection after cardiovascular surgery and to develop a bedside clinical risk index using these factors.

DESIGN

A risk index was developed using clinical data collected from a cohort of 11,508 cardiac surgery patients and validated using three independent subsets of the data. With two of these subsets, we derived a logistic regression equation and then modified the scoring algorithm to simplify the calculation of patient risk scores by clinicians. The final subset was used to validate the index. The area under the receiver operating characteristic (aROC) curve was the primary measure of goodness of fit.

SETTING

Toronto General Hospital, a teaching hospital and the largest center for cardiac surgery in Ontario, Canada.

PATIENTS

Cardiac surgery patients receiving cardiopulmonary bypass between April 1, 1990, and December 31, 1995, who survived at least 6 days after surgery.

RESULTS

Variables that were used to construct the risk index included reoperation due to complication (odds ratio, 4.3; range, 1.9 to 8.5), diabetes (odds ratio, 2.4; range, 1.5 to 3.7), more than 3 days in the intensive care unit (odds ratio, 5.4; range, 3.2 to 8.7), and use of the internal mammary artery for revascularization (odds ratio, 3.2; range, 1.7 to 5.8). Validation showed that the index had an aROC curve of 0.64.

CONCLUSIONS

The risk index described in this article allows clinicians to quickly stratify patients into four risk groups associated with an increasing risk of sternal surgical wound infection. It may be used perioperatively or as part of a wound infection surveillance system.

Sternal Wound Infection Prediction Scale: a test of the reliability and validity

The purpose of the present study was to determine the reliability and validity of the Sternal Wound Infection Prediction Scale. The tool was developed to fill the need for a quick and easy way to determine which patients are at risk of developing a sternal wound infection in order that preventive measures can be instituted. Data were collected by a retrospective chart review of 56 patient records, 27 who developed a sternal wound infection and 29 who did not. In this group of patients, obesity and diabetes were found to be statistically significant risk factors. Pharmacological support was found to be a clinically significant factor. Of the infected group, 68.4% of patients who developed a sternal wound infection were predicted to do so by the tool.

Insulin infusion improves neutrophil function in diabetic cardiac surgery patients

Diabetic patients are at increased risk of wound infection after major surgery, but the effect of perioperative glucose control on postoperative wound infection rates after surgery is uncertain. We tested the effect of an insulin infusion on perioperative neutrophil function in diabetic patients scheduled for coronary artery bypass surgery. Participants (n = 26) were randomly allocated to receive either aggressive insulin therapy (AIT) or standard insulin therapy (SIT) during surgery. Blood was drawn for neutrophil testing before surgery, 1 h after the completion of cardiopulmonary bypass, and on the first postoperative day. Neutrophil phagocytic activity decreased to 75% of baseline activity in the AIT group and to 47% of baseline activity in the SIT group (P < 0.05 between groups). No important differences in neutrophil antibody-dependent cell cytotoxicity were found. This study documents a potentially beneficial effect of continuous insulin therapy in diabetic patients who require major surgery.

IMPLICATIONS

A continuous insulin infusion and glucose control during surgery improves white cell function in diabetic patients and may increase resistance to infection after surgery.

Guideline for Prevention of Surgical Site Infection, 1999. Centers for Disease Control and Prevention (CDC) Hospital Infection Control Practices Advisory Committee

EXECUTIVE SUMMARY The "Guideline for Prevention of Surgical Site Infection, 1999" presents the Centers for Disease Control and Prevention (CDC)'s recommendations for the prevention of surgical site infections (SSIs), formerly called surgical wound infections. This two-part guideline updates and replaces previous guidelines.1,2 Part I, "Surgical Site Infection: An Overview," describes the epidemiology, definitions, microbiology, pathogenesis, and surveillance of SSIs. Included is a detailed discussion of the pre-, intra-, and postoperative issues relevant to SSI genesis. Part II, "Recommendations for Prevention of Surgical Site Infection," represents the consensus of the Hospital Infection Control Practices Advisory Committee (HICPAC) regarding strategies for the prevention of SSIs.3 Whenever possible, the recommendations in Part II are based on data from well-designed scientific studies. However, there are a limited number of studies that clearly validate risk factors and prevention measures for SSI. By necessity, available studies have often been conducted in narrowly defined patient populations or for specific kinds of operations, making generalization of their findings to all specialties and types of operations potentially problematic. This is especially true regarding the implementation of SSI prevention measures. Finally, some of the infection control practices routinely used by surgical teams cannot be rigorously studied for ethical or logistical reasons (e.g., wearing vs not wearing gloves). Thus, some of the recommendations in Part II are based on a strong theoretical rationale and suggestive evidence in the absence of confirmatory scientific knowledge.It has been estimated that approximately 75% of all operations in the United States will be performed in "ambulatory," "same-day," or "outpatient" operating rooms by the turn of the century.4 In recommending various SSI prevention methods, this document makes no distinction between surgical care delivered in such settings and that provided in conventional inpatient operating rooms. This document is primarily intended for use by surgeons, operating room nurses, postoperative inpatient and clinic nurses, infection control professionals, anesthesiologists, healthcare epidemiologists, and other personnel directly responsible for the prevention of nosocomial infections. This document does not: Specifically address issues unique to burns, trauma, transplant procedures, or transmission of bloodborne pathogens from healthcare worker to patient, nor does it specifically address details of SSI prevention in pediatric surgical practice. It has been recently shown in a multicenter study of pediatric surgical patients that characteristics related to the operations are more important than those related to the physiologic status of the patients.5 In general, all SSI prevention measures effective in adult surgical care are indicated in pediatric surgical care. Specifically address procedures performed outside of the operating room (e.g., endoscopic procedures), nor does it provide guidance for infection prevention for invasive procedures such as cardiac catheterization or interventional radiology. Nonetheless, it is likely that many SSI prevention strategies also could be applied or adapted to reduce infectious complications associated with these procedures. Specifically recommend SSI prevention methods unique to minimally invasive operations (i.e., laparoscopic surgery). Available SSI surveillance data indicate that laparoscopic operations generally have a lower or comparable SSI risk when contrasted to open operations.6-11 SSI prevention measures applicable in open operations (e.g., open cholecystectomy) are indicated for their laparoscopic counterparts (e.g., laparoscopic cholecystectomy). Recommend specific antiseptic agents for patient preoperative skin preparations or for healthcare worker hand/forearm antisepsis. Hospitals should choose from products recommended for these activitie

Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee

The “Guideline for Prevention of Surgical Site Infection, 1999” presents the Centers for Disease Control and Prevention (CDC)'s recommendations for the prevention of surgical site infections (SSIs), formerly called surgical wound infections. This two-part guideline updates and replaces previous guidelines.

Part I, “Surgical Site Infection: An Overview,” describes the epidemiology, definitions, microbiology, pathogenesis, and surveillance of SSIs. Included is a detailed discussion of the pre-, intra-, and postoperative issues relevant to SSI genesis.

Development of the Sternal Wound Infection Prediction Scale

OBJECTIVE

To develop an instrument to reliably predict the occurrence of sternal wound infection (SWI).

DESIGN

Instrument development with retrospective chart review.

SETTING

Southwestern university-affiliated medical center.

PATIENTS

One hundred eighty-five adults who underwent cardiac surgery. SWI developed in 94 patients, and 91 remained infection free. In phase 1, there were 82 subjects: SWI developed in 41, and 41 remained infection free. In phase 2, there were 103 subjects: SWI developed in 53, and 50 remained infection free.

OUTCOME MEASURE

Development of a postoperative SWI.

INTERVENTION

The Sternal Wound Infection Prediction Scale (SWIPS) was developed in 2 phases. Phase 1 consisted of designing the SWIPS with use of 19 risk factors most often identified with SWI and revising this scale (SWIPS-R) with use of 21 risk factors. Eighty-two patient records were reviewed. After determining the mean cutscores in phase 1, phase 2 provided cross-validation results with use of 103 additional patient records.

RESULTS

The SWIPS produced 62.1% correct predictions of infection and noninfection; whereas the SWIPS-R produced 72.8% correct predictions. Phase 2 cross-validation results for the 21 risk factors demonstrated that 62.1% and 72.8% of the patients were correctly diagnosed using the SWIPS and SWIPS-R, respectively. A multivariate logistic regression was also performed on the risk factors to predict infection/noninfection groups for all 185 patients. A reduced logistic regression model included 9 of the risk factors and correctly classified 76.2% of the subjects.

CONCLUSIONS

The SWIPS-R, with 21 risk factors, and the logistic regression model, with 12 risk factors, provided excellent classification rates of infection/noninfection. However, more data need to be collected to further strengthen reliability.

Predicting infectious morbidity in elective operations

The determination of surgical risk is a major problem in general surgical practice and many studies have attempted to predict postoperative outcome. Clinical judgment is still a fundamental skill with which the experienced surgeon can estimate the risk of postoperative infectious morbidity. Predictive scores based on statistical analysis have also proven to be valid and useful tools. This discussion analyzes the importance of surgical risk prediction. With future research in this area, it is hoped that therapeutic strategies will result that will reduce or eliminate this risk.

The risk factors of median sternotomy infection: a current review

Sternal sepsis following median sternotomy is an infrequent yet devastating complication of cardiac surgery, leading to prolonged hospitalization, increased hospital expense, and a high associated morbidity and mortality. The development of sternotomy infection is multifactorial. Numerous prospective and retrospective studies have pointed to a multitude of clinical and perioperative variables as being causative, with as many other studies presenting evidence of the contrary. This has led to confusion about which clinical variables should be modified so as to minimize the individual patient's risk for developing this severe complication. Other less obvious factors also come into play. Malnutrition, whether overt or subclinical, is not uncommon in cardiac patients. Immune competency is affected by operative trauma, as well as a variety of perioperative factors including underlying nutritional status, transfusion, cardiopulmonary bypass, and anesthesia. This creates a complex milieu for the development of postoperative infection. In this review, the multiple risk factors of median sternotomy infection are studied and treatment options briefly discussed.