Lillian S. Kao

Development and Validation of a Risk-Stratification Score for Surgical Site Occurrence and Surgical Site Infection after Open Ventral Hernia Repair

BACKGROUND Current risk-assessment tools for surgical site occurrence (SSO) and surgical site infection (SSI) are based on expert opinion or are not specific to open ventral hernia repairs. We aimed to develop a risk-assessment tool for SSO and SSI and compare its performance against existing risk-assessment tools in patients with open ventral hernia repair. STUDY DESIGN A retrospective study of patients undergoing open ventral hernia repair (n = 888) was conducted at a single institution from 2000 through 2010. Rates of SSO and SSI were determined by chart review. Stepwise regression models were built to identify predictors of SSO and SSI and internally validated using bootstrapping. Odds ratios were converted to a point system and summed to create the Ventral Hernia Risk Score (VHRS) for SSO and SSI, respectively. Area under the receiver operating characteristic curve was used to compare the accuracy of the VHRS models against the National Nosocomial Infection Surveillance Risk Index, Ventral Hernia Working Group (VHWG) grade, and VHWG score. RESULTS The rates of SSO and SSI were 33% and 22%, respectively. Factors associated with SSO included mesh implant, concomitant hernia repair, dissection of skin flaps, and wound class 4. Predictors of SSI included concomitant repair, dissection of skin flaps, American Society of Anesthesiologists class ≥ 3, wound class 4, and body mass index ≥ 40. The accuracy of the VHRS in predicting SSO and SSI exceeded National Nosocomial Infection Surveillance and VHWG grade, but was not better than VHWG score. CONCLUSIONS The VHRS identified patients at increased risk for SSO/SSI more accurately than the National Nosocomial Infection Surveillance scores and VHWG grade, and can be used to guide clinical decisions and patient counseling.

The epidemiology of sepsis in general surgery patients

BACKGROUND Sepsis is increasing in hospitalized patients. Our purpose is to describe its current epidemiology in a general surgery (GS) intensive care unit (ICU) where patients are routinely screened and aggressively treated for sepsis by an established protocol. METHODS Our prospective, Institutional Review Board-approved sepsis research database was queried for demographics, biomarkers reflecting organ dysfunction, and mortality. Patients were grouped as sepsis, severe sepsis, or septic shock using refined consensus criteria. Data are compared by analysis of variance, Students t test, and χ test (p<0.05 significant). RESULTS During 24 months ending September 2009, 231 patients (aged 59 years ± 3 years; 43% men) were treated for sepsis. The abdomen was the source of infection in 69% of patients. Several baseline biomarkers of organ dysfunction (BOD) correlated with sepsis severity including lactate, creatinine, international normalized ratio, platelet count, and d-dimer. Direct correlation with mortality was noted with particular baseline BODs including beta natriuretic peptide, international normalized ratio, platelet count, aspartate transaminase, alanine aminotransferase, and total bilirubin. Most patients present with severe sepsis (56%) or septic shock (26%) each with increasing multiple BODs. Septic shock has prohibitive mortality rate (36%), and those who survive septic shock have prolonged ICU stays. CONCLUSION In general surgery ICU patients, sepsis is predominantly caused by intra-abdominal infection. Multiple BODs are present in severe sepsis and septic shock but are notably advanced in septic shock. Despite aggressive sepsis screening and treatment, septic shock remains a morbid condition.

Local variations in the epidemiology, microbiology, and outcome of necrotizing soft-tissue infections: a multicenter study.

BACKGROUND Necrotizing soft-tissue infections (NSTIs) are rare and highly lethal. METHODS A retrospective chart review of patients with NSTIs treated at 6 academic hospitals in Texas between January 1, 2004 and December 31, 2007. Patient demographics, presentation, microbiology, treatment, and outcome were recorded. Analysis of variance, chi-square test, and logistic regression analysis were performed. RESULTS Mortality rates varied between hospitals from 9% to 25% (n = 296). There was significant interhospital variation in patient characteristics, microbiology, and etiology of NSTIs. Despite hospital differences in treatment, primarily in critical care interventions, patient age and severity of disease (reflected by shock requiring vasopressors and renal failure postoperatively) were the main predictors of mortality. CONCLUSIONS Significant center differences occur in patient populations, etiology, and microbiology of NSTIs, even within a concentrated region. Management should be based on these characteristics given that adjunctive treatments are unproven and variations in outcome are likely because of patient disease at presentation.

Training future surgical scientists: realities and recommendations.

Objective:To examine factors influencing surgical research and assess the current state of training future surgical scientists. Summary Background Data:The number of surgeons actively engaged in research seems to be decreasing. Training future surgical scientists to increase these numbers depends on a variety of factors that are constantly changing. Current trends at the National Institutes of Health (NIH) and changes in graduate medical education make the training of the next generation of surgical scientists more challenging than ever. Methods:Recent literature in surgical education, surgical research, and funding patterns at the NIH were reviewed. Results:Quantitative and qualitative deficiencies exist in surgical research. Although an increasing number of students are becoming interested in surgery, the burden of debt from medical school may preclude them from pursuing research during or after residency. Research training is complicated by the fact that no formal curriculum exists for training in research and oversight is lacking. Junior faculty face increased demands for clinical revenue, which decreases time for research. In addition, surgeons are less successful at obtaining NIH funding when compared with nonsurgeons and seem to be at a disadvantage. Conclusions:Development of the next generation of surgical scientists begins by attracting the best students into surgery and by providing a structured research curriculum with appropriate oversight. Senior surgical faculty need to become more active at the NIH and provide appropriate financial support and mentorship for residents and junior faculty engaged in research.

Compliance with guidelines to prevent surgical site infections: As simple as 1-2-3?

BACKGROUND the purpose of this study was to assess predictive factors and compliance with surgical site infection (SSI) prevention guidelines at 2 county hospitals. DESIGN chart review and analysis of laparotomy patients undergoing colorectal, hysterectomy, or abdominal vascular procedures over two 6-month periods 1 year apart and evaluation of safety climate using the Safety Attitudes Questionnaire (SAQ). RESULTS overall compliance with all antibiotic prophylaxis guidelines was 62% (n = 442). Gynecologic surgery was an independent predictor of compliance with antibiotic prophylaxis guidelines in elective cases, and nonemergency status was an independent predictor when all cases were considered. Postoperative normothermia was predicted by hospital, procedure length, initial intraoperative temperature, and service. The SAQ had a 91% response rate. Contrary to expected, safety domain scores and agreement with statements on collaboration and teamwork were not predictive of compliance. CONCLUSION interventions to improve poor compliance with infection prevention guidelines must be multifaceted, hospital- and service-specific, and resilient during emergencies. Good safety and teamwork climate are not sufficient.

Predicting Death in Necrotizing Soft Tissue Infections: A Clinical Score

BACKGROUND Necrotizing soft tissue infections (NSTIs) are associated with a high mortality rate; however, there is no uniform way to categorize the severity of this disease early in its course. The goal of this study was to develop a clinical score based on data available at the time of initial assessment to aid in stratifying patients according to their risk of death. METHODS A cohort of all 350 patients admitted with NSTI to two institutions over a nine-year period was examined retrospectively. Using random split sampling, two datasets were created: Prediction (PD) and validation (VD). Multivariable stepwise regression analysis of the PD identified independent predictors of death using data available at the time of admission. Model performance was evaluated for accuracy, discrimination, and calibration. A clinical score to predict death was created, and using the Trauma and Injury Severity Score (TRISS) methodology, the score was validated on the VD (z-statistic). RESULTS Six admission parameters independently predicted death: Age > 50 years, heart rate > 110 beats/min, temperature <36 degrees C, white blood cell count > 40,000/mcL, serum creatinine concentration > 1.5 mg/dL, and hematocrit > 50%. The accuracy of this model was 86.8%; the area under the receiver-operating characteristic curve was 0.81, and the Hosmer-Lemeshow statistic was 11.8. Additionally, the score had excellent performance in evaluation on the VD (z-score/statistic 0.23 to - 0.83). CONCLUSION A clinical score that categorizes patients with NSTI according to the risk of death was created. It uses simple variables, all available at the time of first assessment. It stratifies patients according to disease severity and can guide the use of aggressive or novel therapeutic strategies and selection of patients for clinical trials.

Surgical Education in the Internet Era1

Technological advancements, along with economic and political issues, have resulted in major changes in surgical education. The development of high fidelity simulators and the widespread availability of the Internet have allowed learning to be shifted away from the operating room. Furthermore, the Internet provides an opportunity for surgical educators to standardize general surgery training and assessment and to develop collaborations nationally and globally. This paper highlights presentations about the challenges as well as the rewards of surgical education in the age of the Internet from the 2009 Academic Surgical Congress.

Outcomes of laparoscopic vs open repair of primary ventral hernias

IMPORTANCE More primary ventral hernias (PVHs) are being repaired using the technique of laparoscopic ventral hernia repair (LVHR). Few studies exist comparing the outcomes of LVHR with the outcomes of open ventral hernia repair (OVHR) for PVHs. We hypothesize that LVHR of PVHs is associated with fewer surgical site infections (SSIs) but more hernia recurrences and more clinical cases of bulging (bulging not associated with recurrence or seroma). OBJECTIVE To compare the outcomes of patients who underwent LVHR with the outcomes of patients who underwent OVHR. DESIGN Retrospective study of 532 consecutive patients who underwent an elective PVH repair at a single institution from 2000 to 2010. The outcomes of the 2 procedures were compared using 2 statistical methods. Multivariable logistic regression was used to evaluate the association between outcomes and several independent factors, adjusting for treatment propensity, and the outcomes in the 2 groups of patients were compared using paired univariate analysis. SETTING Michael E. DeBakey VA Medical Center in Houston, Texas. PARTICIPANTS Seventy-nine patients who underwent LVHR and 79 patients who underwent OVHR. MAIN OUTCOMES AND MEASURES The primary outcomes of interest were SSI, hernia recurrence, and bulging. The 2 groups of patients were matched by hernia size, American Society of Anesthesiologists class, age, and body mass index. RESULTS There were 91 patients who underwent an LVHR and 167 patients who underwent an OVHR with mesh, with a median follow-up period of 56 months (range, 1-156 months). Seventy-nine patients with an LVHR were matched to 79 patients with an OVHR. No significant differences in demographic data or confounding factors were detected between the 2 groups. Compared with OVHR, LVHR was significantly associated with fewer SSIs (7.6% vs 34.1%; P < .01) but more clinical cases of bulging (21.5% vs 1.3%; P < .01) and port-site hernia (2.5% vs 0.0%). No differences in recurrence at the site of the hernia repair were observed (11.4% vs 11.4%; P = .99). Propensity score-matched multivariate analysis corroborated that LVHR is associated with more clinical cases of bulging but fewer SSIs. CONCLUSIONS AND RELEVANCE Compared with OVHR of PVHs, LVHR of PVHs is associated with fewer SSIs but more clinical cases of bulging and with the risk of developing a port-site hernia. Further study is needed to clarify the role of LVHR of PVHs and to mitigate the risk of port-site hernia and bulging.

Clinical Research Methodology I: Introduction to Randomized Trials

With increasing initiatives to improve the effectiveness and safety of patient care, there is a growing emphasis on evidence-based medicine and incorporation of high-quality evidence into clinical practice. The cornerstone of evidence-based medicine is the randomized controlled trial (RCT). The World Health Organization defines a clinical trial as “any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes.”1 Randomization refers to the method of assignment of the intervention or comparison(s). Fewer than 10% of clinical studies reported in surgical journals are RCTs,2–4 and treatments in surgery are only half as likely to be based on RCTs as treatments in internal medicine.5 Multiple factors impede surgeons performing definitive RCTs, including the inability to blind health care providers and patients, small sample sizes, variations in procedural competence, and strong surgeon or patient preferences.5–8 Not all questions can be addressed in an RCT; Solomon and colleagues8 estimated that only 40% of treatment questions involving surgical procedures are amenable to evaluation by an RCT, even in an ideal clinical setting. In surgical oncology, trials evaluating survival after operations for a rare malignancy can require an unreasonably large sample size. Pawlik and colleagues9 estimated that only 0.3% of patients with pancreatic adenocarcinoma could benefit from pancreaticoduodenectomy with extended lymphadenectomy; a randomized trial of 202,000 patients per arm would be necessary to detect a difference in survival. These reasons should not dissuade surgeons from performing RCTs. Even for rare diseases, randomized trials remain the best method to obtain unbiased estimates of treatment effect.10,11 Rigorously conducted RCTs minimize bias by controlling for known and unknown factors (confounders) that affect outcomes and distort the apparent treatment effect. Observational studies, including those with the most sophisticated design and analysis,12,13 can control only for known confounders and might not adequately control for those. Many surgical and medical interventions recommended based on observational studies have later been demonstrated to be ineffective or even harmful. These have included blood transfusions to maintain a hemoglobin >10 mg/dL in critically ill patients,14,15 bone marrow transplantation for breast cancer,16–19 and extracranial-intracranial bypass for carotid artery stenosis.20,21 Another major reason for RCTs to be of interest to surgeons is that patients enrolled in trials can have improved short-term outcomes, even if the intervention is ineffective.22–25 Potential sources of this benefit include enrollment of lower-risk patients, use of standardized protocols and improved supportive care, and greater effort to prevent and address treatment hazards. Different outcomes can also be observed in trial participants because of either the Hawthorne or placebo effect, both of which can distort the apparent treatment effect and threaten the validity of the trial. The Hawthorne effect occurs when changes in clinicians’ or patients’ behavior, because of being observed, results in improved outcomes. For example, a prospective observational study evaluating operating room efficiency after an intervention can demonstrate improvement over historic performance, in part because the staff is aware of being observed rather than as a result of the intervention. The placebo effect occurs when the patient derives benefit not from the treatment itself, but from the patient’s expectations for benefit. In a randomized trial of arthroscopic surgery versus sham surgery for osteoarthritis of the knee, the placebo procedure had equivalent results to debridement and lavage, despite lack of any therapeutic intervention.26 Despite the advantages of well-conducted RCTs, poorly conducted trials or inadequately reported results can yield misleading information.27,28 Recently, Chang and colleagues29 demonstrated the continued paucity of high-level evidence in surgical journals and called for articles on clinical research methodology to educate surgeons. The purpose of this article is to serve as an introduction to RCTs, focusing on procedures for assigning treatment groups that serve to minimize bias and error in estimating treatment effects. Common threats to validity and potential solutions to difficulties in randomizing patients in surgical trials will also be discussed.

Should perioperative supplemental oxygen be routinely recommended for surgery patients? A Bayesian meta-analysis.

Objective:The purpose of this study is to use updated data and Bayesian methods to evaluate the effectiveness of hyperoxia to reduce surgical site infections (SSIs) and/or mortality in both colorectal and all surgery patients. Because few trials assessed potential harms of hyperoxia, hazards were not included. Background:Use of hyperoxia to reduce SSIs is controversial. Three recent meta-analyses have had conflicting conclusions. Methods:A systematic literature search and review were performed. Traditional fixed-effect and random-effect meta-analyses and Bayesian meta-analysis were performed to evaluate SSIs and mortality. Results:Traditional meta-analysis yielded a relative risk of an SSI with hyperoxia among all surgery patients of 0.84 [95% confidence interval (CI): 0.73–0.97] and 0.84 (95% CI: 0.61–1.16) for the fixed-effect and random-effect models, respectively. The probabilities of any risk reduction in SSIs among all surgery patients were 77%, 81%, and 83% for skeptical, neutral, and enthusiastic priors. The subset analysis of colorectal surgery patients increased the probabilities to 86%, 89%, and 92%. The probabilities of at least a 10% reduction were 57%, 62%, and 68% for all surgery patients and 71%, 75%, and 80% among the colorectal surgery subset. Conclusions:There is a moderately high probability of a benefit to hyperoxia in reducing SSIs in colorectal surgery patients; however, the magnitude of benefit is relatively small and might not exceed treatment hazards. Further studies should focus on generalizability to other patient populations or on treatment hazards and other outcomes.