Recommendations of the Blue Ribbon Committee II for the Optimization of Surgical Education and Training in the United States: The Surgical Trainee Perspective.

OBJECTIVE: This study aims to appraise recommendations from an expert panel of surgical educators on optimizing surgical education and training in the setting of contemporary challenges. BACKGROUND: The Blue Ribbon Committee (BRC II), a group of surgical educators, was convened to make recommendations to optimize surgical training considering the current changes in the landscape of surgical education. Surgical trainees were recruited to assess their impressions of the recommendations. METHODS: A mixed-methods study design was employed, with a survey, followed by focus group interviews. Participating residents and fellows were recruited through a purposeful sampling approach. Descriptive statistics were applied to analyze the survey data, and a thematic data analysis on interview transcripts was employed. RESULTS: The majority of trainee respondents (n=16) thought that all of the subcommittee recommendations should be included in the final BRC II recommendations and paper. According to the interviews, overall, the feedback from the trainees was positive, with particular excitement around work-life integration, education support and faculty development, and funding pitfalls. Some themes about concerns included a lack of clarity about the recommendations, concern about some recommendations being in conflict with one another, and a disconnect between the initial BRC II survey and the subsequent recommendations. CONCLUSIONS: The residents gathered for this focus group were encouraged by the thought, effort, and intention that gathered the surgical leaders across the country to make the recommendations. While there were areas the trainees wanted clarity on, the overall opinion was in agreement with the recommendations.

Focused assessment with sonography for trauma exam for diagnosis of pericardial effusion in penetrating thoracic trauma - A retrospective review from a level 1 trauma center.

INTRODUCTION: Point of care ultrasound has long been used in the trauma setting for rapid assessment and diagnosis of critically ill patients. Its utility for diagnosis of pericardial effusion in the setting of penetrating thoracic trauma has more recently been a topic of consideration, given the rapid decompensation that these patients can experience. OBJECTIVES: This study aims to identify the diagnostic accuracy of point of care ultrasound in the diagnosis of pericardial effusion among patients with penetrating thoracic trauma. METHODS: Retrospective review of 2099 patients brought to the trauma bay between the years 2016 and 2021 were analyzed for diagnosis of pericardial effusion. Patients who were diagnosed with a pericardial effusion were investigated for point of care ultrasound findings. Descriptive statistics were performed to identify sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: Prevalence was calculated to be 26.7 cases of pericardial effusion per 1000 patients presenting with penetrating thoracic trauma. Incidence was estimated to be 3.8 cases of pericardial effusion per 1000 person-years. Calculation of diagnostic capabilities of ED POCUS revealed a sensitivity of 96.36 â€‹%, a specificity of 100 â€‹%, PPV of 100 â€‹%, and NPV of 99.90 â€‹%. CONCLUSIONS: Point of Care cardiac ultrasonography is a reliable tool for the rapid diagnosis of pericardial effusion in penetrating thoracic trauma patients. Patients with ultrasound suggestive of this condition should receive rapid surgical management to prevent decompensation.

PROSPECTIVE EXAMINATION OF THE K/ICA RATIO AS A PREDICTOR FOR MORTALITY IN SEVERE HEMORRHAGE.

ABSTRACT: Background: Patients receiving massive transfusion protocol (MTP) are at risk for posttransfusion hypocalcemia and hyperkalemia. Previous retrospective analysis has suggested the potassium/ionized calcium (K/iCa) ratio as a prognostic indicator of mortality. This prospective study sought to validate the value of the K/iCa ratio as a predictor for mortality in patients receiving MTP. Methods: This was a prospective analysis of adult trauma patients who underwent MTP activation from May 2019 to March 2021 at an urban level 1 trauma center. Serum potassium and iCa levels within 0 to 1 h of MTP initiation were used to obtain K/iCa. Receiver operator characteristic curve analysis assessed predictive capacity of K/iCa on mortality. Kaplan-Meier survival analysis and Cox regression examined the effect of K/iCa ratio on survival. Results: A total of 110 of 300 MTP activation patients met inclusion criteria. Overall mortality rate was 31.8%. No significant differences between the elevated K/iCa and lower K/iCa groups were found for prehospital or emergency department initial vitals, shock index, or injury severity. However, nonsurvivors had a significantly higher median K/iCa ratio compared with those who survived ( P < 0.01). Multivariable logistic regression revealed the total number of blood products to be significantly associated with elevated K/iCa (odds ratio, 1.02; 95% CI, 1.01-1.04; P = 0.01). The Kaplan Meier survival curve demonstrated a significantly increased rate of survival for those with an elevated K/iCa ratio ( P < 0.01). Multivariable Cox regression adjusted for confounders showed a significant association between K/iCa and mortality (Hazard Ratio, 4.12; 95% CI, 1.89-8.96; P < 0.001). Conclusion: This evidence further highlights the importance of the K/iCa ratio in predicting mortality among trauma patients receiving MTP. Furthermore, it demonstrates that posttransfusion K levels along with iCa levels should be carefully monitored in the MTP setting. Level of Evidence: Level II. Study Type: Prognostic/epidemiological.

Metabolic impact of high lipid low dextrose parenteral nutrition.

BACKGROUND: Parenteral nutrition (PN) containing 100% soybean oil lipids and high amounts of dextrose may lead to liver dysfunction and hyperglycemia. Mixed lipids have less pro-inflammatory components, so higher doses may be given to decrease the amount of dextrose provided. The purpose of this study is to provide a descriptive analysis of patients who received PN with high mixed lipid and low dextrose content versus PN with lower 100% soybean oil lipid and high dextrose content. METHODS: We retrospectively reviewed 62 patients aged ≥18 years receiving PN ≥ 7 days from 2016 to 2021 in an acute care hospital. Participants were divided into two groups: high lipid low dextrose (HLLD) containing a four-oil lipid (>30% kcal or ≥1 g/kg) vs adequate lipid high dextrose (ALHD) containing a 100% soybean oil lipid (<30% kcal or <1 g/kg SO-ILE). RESULTS: Patients in the HLLD group (n = 31) had 64.1% lower incidence of blood glucose levels >180 mg/dL, decreased insulin requirements, 52.7% lower alkaline phosphatase levels, 40.6% higher prealbumin levels, and 42.6% lower c-reactive protein levels while maintaining similar calorie targets compared to the ALHD group (n = 31). CONCLUSION: Changing from 100% soybean oil to a mixed lipid in PN is helpful to reduce soybean oil intake. However, it is also important to increase the mixed lipid dose to decrease the amount of dextrose provided. PNs containing higher amounts of mixed lipids (40-45% kcal) with lower amounts of dextrose (20-30% kcal) may have clinical benefits that warrant further exploration.

Tropical Storms and Hurricanes in New Orleans Lead to Increased Rates of Violent Injury.

OBJECTIVE: The effects of named weather storms on the rates of penetrating trauma is poorly understood with only case reports of single events currently guiding public health policy. This study examines whether tropical storms and hurricanes contribute to trauma services and volume. METHODS: This was a cross-sectional review of tropical storms/hurricanes affecting New Orleans, Louisiana, during hurricane seasons (June 1-November 30) from 2010-2021, and their association with the rate of penetrating trauma. Authors sought to determine how penetrating trauma rates changed during hurricane seasons and associate them with demographic variables. RESULTS: There were 5531 penetrating injuries, with 412 (7.4%) occurring during landfall and 554 (10.0%) in the aftermath. Black/African Americans were the most affected. There was an increase in the rate of penetrating events during landfall (3.4 events/day) and aftermath (3.5 events/day) compared to the baseline (2.8 events/day) (P = < 0.001). Using multivariate analysis, wind speed was positively related to firearm injury, whereas the rainfall total was inversely related to firearm violence rates during landfall and aftermath periods. Self-harm was positively related to distance from the trauma center. CONCLUSIONS: Cities at risk for named weather storms may face increasing gun violence in the landfall and aftermath periods. Black/African Americans are most affected, worsening existing disparities. Self-harm may also increase following these weather events.

Association Between Markers of Structural Racism and Mass Shooting Events in Major US Cities.

Importance: The root cause of mass shooting events (MSEs) and the populations most affected by them are poorly understood. Objective: To examine the association between structural racism and mass shootings in major metropolitan cities in the United States. Design, Setting, and Participants: This cross-sectional study of MSEs in the 51 largest metropolitan statistical areas (MSAs) in the United States analyzes population-based data from 2015 to 2019 and the Gun Violence Archive. The data analysis was performed from February 2021 to January 2022. Exposure: Shooting event where 4 or more people not including the shooter were injured or killed. Main Outcome and Measures: MSE incidence and markers of structural racism from demographic data, Gini income coefficient, Black-White segregation index, and violent crime rate. Results: There were 865 MSEs across all 51 MSAs from 2015 to 2019 with a total of 3968 injuries and 828 fatalities. Higher segregation index (ρ = 0.46, P = .003) was associated with MSE incidence (adjusted per 100 000 population) using Spearman ρ analysis. Percentage of the MSA population comprising Black individuals (ρ = 0.76, P < .001), children in a single-parent household (ρ = 0.44, P < .001), and violent crime rate (ρ = 0.34, P = .03) were other variables associated with MSEs. On linear regression, structural racism, as measured by percentage of the MSA population comprising Black individuals, was associated with MSEs (ß = 0.10; 95% CI, 0.05 to 0.14; P < .001). Segregation index (ß = 0.02, 95% CI, -0.03 to 0.06; P = .53), children in a single-parent household (ß = -0.04, 95% CI, -0.11 to 0.04; P = .28), and Gini income coefficient (ß = -1.02; 95% CI, -11.97 to 9.93; P = .93) were not associated with MSEs on linear regression. Conclusions and Relevance: This study found that major US cities with higher populations of Black individuals are more likely to be affected by MSEs, suggesting that structural racism may have a role in their incidence. Public health initiatives aiming to prevent MSEs should target factors associated with structural racism to address gun violence.

High lipid, low dextrose parenteral nutrition allows patient to achieve nutritional autonomy: A case report.

INTRODUCTION: Prolonged use of parenteral nutrition can eventually lead to liver abnormalities. Causative factors include decreased enteral stimulation, high intakes of intravenous dextrose, proinflammatory 100 % soybean oil-based lipids, and increased burden on liver through 24-h infusions. We present a case report of a patient who received parenteral nutrition modifications to address liver dysfunction. PRESENTATION OF CASE: Our patient was a 37-year-old African American male with a past medical history including refractory Crohn's disease complicated by multiple small bowel obstructions, several bowel surgeries, left lower quadrant colostomy placement, short bowel syndrome, severe protein calorie malnutrition, parenteral nutrition dependence, and elevated liver function tests. He was admitted for nutritional optimization before a planned takedown of multiple chronic enterocutaneous and perianal fistulas. His home parenteral nutrition order contained high amounts of dextrose (69 % kcal), and low amounts of 100 % soybean oil (11 % kcal). DISCUSSION: Due to an elevated alkaline phosphatase level at baseline (1746 U/L), the Registered Dietitian maximized protein, decreased the dextrose by 62.5 %, and changed to SMOFlipid (a fish-oil containing lipid) at >1 g/kg/day to address liver abnormalities. Within 1.5 months of changing parenteral nutrition to high SMOFlipid (>30 % kcal) with low dextrose (<30 % kcal) content, alkaline phosphatase levels declined by 62 %, prealbumin levels increased by 56 %, and c-reactive protein levels decreased by 62 %. CONCLUSION: Parenteral nutrition modifications led to reversal of chronic liver dysfunction. This patient ultimately underwent a successful high-risk fistula takedown procedure, allowing for complete weaning of parenteral nutrition and achievement of sustained nutritional autonomy.

Succinate metabolism and membrane reorganization drives the endotheliopathy and coagulopathy of traumatic hemorrhage.

Acute hemorrhage commonly leads to coagulopathy and organ dysfunction or failure. Recent evidence suggests that damage to the endothelial glycocalyx contributes to these adverse outcomes. The physiological events mediating acute glycocalyx shedding are undefined, however. Here, we show that succinate accumulation within endothelial cells drives glycocalyx degradation through a membrane reorganization-mediated mechanism. We investigated this mechanism in a cultured endothelial cell hypoxia-reoxygenation model, in a rat model of hemorrhage, and in trauma patient plasma samples. We found that succinate metabolism by succinate dehydrogenase mediates glycocalyx damage through lipid oxidation and phospholipase A2-mediated membrane reorganization, promoting the interaction of matrix metalloproteinase 24 (MMP24) and MMP25 with glycocalyx constituents. In a rat hemorrhage model, inhibiting succinate metabolism or membrane reorganization prevented glycocalyx damage and coagulopathy. In patients with trauma, succinate levels were associated with glycocalyx damage and the development of coagulopathy, and the interaction of MMP24 and syndecan-1 was elevated compared to healthy controls.

Intrahepatic cholangiocarcinoma: Evolving role of neoadjuvant and targeted therapy.

Intrahepatic cholangiocarcinoma is an aggressive, often fatal, malignancy that arises from the bile ducts. As it often presents with metastatic disease, surgery has limited utility. However, in some cases, neoadjuvant chemotherapy has provided the necessary reduction in tumor burden to allow for adequate resection. Consequently, new advances in neoadjuvant chemoradiation and targeted therapy are of interest with numerous case reports and small series published routinely; it is challenging to present a large case series or study given the overall rare frequency with which this malignancy is seen. Herein, we aim to summarize the newest advances in both neoadjuvant chemotherapy and targeted immunotherapy.

Tulane STAR (Sending Texts, Advancing Results): impact of text messaging on bariatric post-operative protocol compliance.

BACKGROUND: Text messaging is frequently employed in the outpatient setting to communicate with or send reminders to patients. However, there is a paucity of literature on the impact of text messaging on inpatient care. In this study, the use of text messaging in hospitalized patients is evaluated by assessing patient compliance to a post-operative bariatric protocol. METHODS: This was a randomized controlled trial that studied compliance to a post-operative bariatric protocol in patients who underwent bariatric surgery at a tertiary, academic medical center between February and May 2021. Patients were randomized to either the control group, in which they received standard post-operative education alone or the Tulane Sending Texts, Advancing Results (STAR) intervention arm, in which participants received the same post-operative education along with two text message reminders to drink water, use their incentive spirometers, and ambulate (per post-operative instructions) on post-operative day (POD) # 0 and POD # 1. The primary outcome was compliance with the protocol, defined as the number of 1-oz cups of water consumed, incentive spirometry usage, and ambulation frequency and distance. Secondary outcomes include length of stay and complications. RESULTS: A total of 35 patients were enrolled in the study (17 control, 18 STAR intervention). There was no significant difference in age, BMI, or type of surgery performed between the two groups. Clear liquid consumption was significantly higher in the STAR intervention group with an average of 27.7 ± 3.5 cups as compared to 18.2 ± 8.9 in the control group (p < 0.001). Similarly, statistically significant increases in incentive spirometry usage (p < 0.01) and ambulation distance and frequency (p < 0.02) were observed in the STAR intervention group. CONCLUSIONS: While patients are in the hospital, text messaging can improve compliance to post-operative protocols. Peri-operative text messaging can enhance patient education and communication.

Elevated K/iCa ratio is an ancillary predictor for mortality in patients with severe hemorrhage: A decision tree analysis.

INTRODUCTION: Trauma patients receiving massive transfusion protocol (MTP) are at risk of citrate-induced hypocalcemia and hyperkalemia. Here we evaluate potassium (K), ionized calcium (iCa), and K/iCa ratio as predictors of mortality. METHODS: This retrospective study includes all adult trauma patients who received MTP within 1 h at our level I trauma center between 2014 and 2019. Receiver operating characteristic curve analysis assessed predictive accuracy of K/iCa ratio at admission on 120-day mortality. RESULTS: Of 614 patients, 146 received MTP within 1 h and 38 expired. Patients who expired had higher K/iCa ratio than survivors (median [IQR] = 5.7 [3.8-7.2] vs 3.7 [3.1-4.9], p < 0.001). Area under the curve of K/iCa was 0.72 (95%CI = 0.62-0.82, p < 0.001) with sensitivity = 63.2% and specificity = 77.6%. At the optimum K/iCa cutoff (5.07), patients with high ratios had 4 times higher mortality risk (HR = 3.97, 95%CI = 1.89-8.32, p < 0.001). CONCLUSION: Elevated K/iCa ratio was an independent predictor of mortality in trauma patients managed with MTP.

I text for I COUGH: A clinical pilot study to evaluate the impact of text messaging upon postoperative ambulation in the hospital.

BACKGROUND: The "I COUGH" protocol is associated with improved postoperative pulmonary outcomes, and ambulation is an essential component. I COUGH is an acronym for Incentive spirometry, Coughing, Oral care, Understanding (patient and staff education), Getting-out-of-bed, and Head-of-bed elevation. This trial sought to enhance one component, specifically ambulation after operations. METHODS: Randomized trial of inpatients in a safety-net, academic medical center. The intervention group received standard I COUGH education along with text message reminders to ambulate postoperatively, whereas the control group received standard education alone. Postoperative walking frequency was compared to each participant's ambulation on the day prior to enrollment. RESULTS: The intervention group had an average improvement of 1.8 ± 1.8 walks per day per patient, while the average change for the control group was 0.2 ± 1.0 walks per day per patient. This represents a 9-fold increase in ambulation for the intervention group (p = 0.03). CONCLUSIONS: Implementation of text message reminders increased ambulation and improved adherence to the I COUGH protocol following operations. This system should be further investigated as an adjunct to postoperative care.

Between a Rock and a Hard Place-Colonic Obstruction Between Two Kidneys: A Case Report.

We report a case of a 70-year-old woman with a history of end-stage renal disease secondary to polycystic kidney disease with a previous failed transplant who presented for a cadaveric extraperitoneal renal transplant. The patient developed a progressively worsening bowel obstruction postoperatively and evidence of an obstruction was observed on computed tomography imaging with a transition point at the level of the sigmoid colon. Consequent to this, she underwent an exploratory laparotomy, which revealed kinking of the colon secondary to the compression between the transplanted and the left native polycystic kidneys. There were adhesive bands between the native kidney and the descending colon in the retroperitoneal space maintaining it in a fixed position mechanically. The addition of a retroperitoneal transplant exacerbated this kink and was responsible for the bowel obstruction. Her left colon was completely mobilized to relieve her obstruction, and owing to her bowel distension, her abdomen was left open for 2 days before returning to the operating room to remove her left native polycystic kidney to allow space for safe closure. This report highlights an extremely unusual cause of large bowel obstruction post-kidney transplantation.

Molecular Alterations in Solid Pseudopapillary Neoplasm of the Pancreas: The Achilles Heel in Conquering Pancreatic Tumorigenesis.

ABSTRACT: Solid pseudopapillary neoplasms of the pancreas are overwhelmingly benign tumors predominately observed in women in the third decade of life. However, their malignant potential, based on local recurrences and metastases, has brought into question the available evidence on their biological behavior. Solid pseudopapillary neoplasms have distanced themselves from other pancreatic tumors with varying morphological appearance, immune profile, and histogenesis. In review of the literature, PubMed was queried using search strings, including "solid pseudopapillary neoplasm" and "molecular," and "immunohistochemistry." Alternative searches were also conducted given the variability in tumor name, including "solid pseudopapillary tumor" and "Frantz tumor." This article provides an in-depth review into the molecular pathways that contribute to the pathogenesis of solid pseudopapillary neoplasms. It also discusses the implications of existing molecular pathways toward tumor aggressiveness and recurrence potential.

Multicentric Breast Abscesses in a Patient Who Had COVID-19.

Background: Coronavirus disease 2019 (COVID-19) is recognized as a multisystem disease affecting the whole body, with new complications from the disease being described on an almost-daily basis. Case Report: We report the case of a 50-year-old female with a medical history of diabetes and silicone breast implants who developed right-sided, multicentric breast masses after a prolonged hospitalization for COVID-19 infection complicated by renal failure requiring dialysis. The patient noted an onset of breast pain and masses, and subsequent imaging demonstrated multiple similar oval masses. She underwent biopsy and operative debridement of the lesions and recovered appropriately. Results were consistent with sterile abscesses that were considered secondary to a vasculitis-like process associated with COVID-19 infection. Conclusion: To our knowledge, this case is the first account of breast pathology associated with a diagnosis of COVID-19 in the medical literature and encourages systematic evaluations of patients with coronavirus infections, including breast examinations.

Percutaneous Cholecystostomy in Acute Cholecystitis-Predictors of Recurrence and Interval Cholecystectomy.

BACKGROUND: Percutaneous cholecystostomy (PC) tube is a preferred option in acute cholecystitis for patients who are high risk for cholecystectomy (CCY). There are no evidence-based guidelines for patient care after PC. We identified the predictors of disease recurrence and successful interval CCY. METHODS: A retrospective review of 145 PC patients between 2008 and 2016 at a tertiary hospital was performed. Primary outcomes included mortality, readmissions, hospital and intensive care unit length of stay (LOS), disease recurrence, and interval CCY. RESULTS: There were 96 (67%) calculous and 47 (33%) acalculous cholecystitis cases. Seventy-two (49%) had chronic and 73 (51%) had acute prohibitive risks as an indication for PC. There were 54 (37%) periprocedural complications, which most commonly were dislodgements. Twenty-six (18%) patients had a recurrence at a median time of 65 days. Calculous cholecystitis (odds ratio [OR] 3.44, P = 0.038) and purulence in the gallbladder (OR 3.77, P = 0.009) were predictors for recurrence. Forty-one (28%) patients underwent interval CCY. Patients with acute illness were likely to undergo interval CCY (OR 6.67, P = 0.0002). Patients with acalculous cholecystitis had longer hospital LOS (16 versus 8 days) and intensive care unit LOS (2 versus 0 days), and higher readmission rates (OR 2.42, P = 0.02). Thirty-day mortality after PC placement was 9%. Patients receiving interval CCY were noted to have increased survival compared to PC alone. However, this should not be attributed to interval CCY alone in absence of randomization in this study. CONCLUSIONS: Calculous cholecystitis and purulence in the gallbladder are independent predictors of acute cholecystitis recurrence. Acute illness is a strong predictor of successful interval CCY. The association of interval CCY and prolonged survival in patients with PC as noted in this study should be further assessed in future prospective randomized trials.

Targeted HAS2 Expression Lessens Airway Responsiveness in Chronic Murine Allergic Airway Disease.

Hyaluronan (HA), a major component of the extracellular matrix, is secreted by airway structural cells. Airway fibroblasts in allergic asthma secrete elevated levels of HA in association with increased HA synthase 2 (HAS2) expression. Thus, we hypothesized that HA accumulation in the airway wall may contribute to airway remodeling and hyperresponsiveness in allergic airways disease. To examine this hypothesis, transgenic mice in which the α-smooth muscle actin (α-SMA) promoter drives HAS2 expression were generated. Mixed male and female α-SMA-HAS2 mice (HAS2+ mice, n = 16; HAS2- mice, n = 13) were sensitized via intraperitoneal injection and then chronically challenged with aerosolized ovalbumin (OVA) for 6 weeks. To test airway responsiveness, increasing doses of methacholine were delivered intravenously and airway resistance was measured using the forced oscillation technique. HA, cytokines, and cell types were analyzed in bronchoalveolar lavage fluid, serum, and whole lung homogenates. Lung sections were stained using antibodies specific for HA-binding protein (HABP) and α-SMA, as well as Masson's trichrome stain. Staining of lung tissue demonstrated significantly increased peribronchial HA, α-SMA, and collagen deposition in OVA-challenged α-SMA-HAS2+ mice compared with α-SMA-HAS2- mice. Unexpectedly, OVA-challenged α-SMA-HAS2+ mice displayed significantly reduced airway responsiveness to methacholine compared with similarly treated α-SMA-HAS2- mice. The total numbers of inflammatory cell types in the bronchoalveolar lavage fluid did not differ significantly between OVA-challenged α-SMA-HAS2+ mice and α-SMA-HAS2- mice. We conclude that allergen-challenged mice that overexpress HAS2 in myofibroblasts and smooth muscle cells develop increased airway fibrosis, which lessens airway hyperresponsiveness to bronchoconstrictors.

Insights into the substrate specificity of the MutT pyrophosphohydrolase using structural analogues of 8-oxo-2'-deoxyguanosine nucleotide.

The bacterial repair enzyme MutT hydrolyzes the damaged nucleotide OdGTP (the 5'-triphosphate derivative of 8-oxo-2'-deoxyguanosine; OdG), which is a known mutagen and has been linked to antibacterial action. Previous work has indicated important roles for the C8-oxygen, N7-hydrogen, and C2-exocyclic amine during OdGTP recognition by MutT. In order to gain a more nuanced understanding of the contribution of these three sites to the overall activity of MutT, we determined the reaction parameters for dGTP, OdGTP, and nine of their analogues using steady state kinetics. Our results indicate that overall high reaction efficiencies can be achieved despite altering any one of these sites. However, altering two or more sites leads to a significant decrease in efficiency. The data also suggest that, similar to another bacterial OdG repair enzyme, MutM, a specific carbonyl in the enzyme can not only promote activity by forming an active site hydrogen bond with the N7-hydrogen of OdGTP, but can also hinder activity through electrostatic repulsion with the N7-lone pair of dGTP.