Kathryn L. Butler

Cathelicidin family of antimicrobial peptides: proteolytic processing and protease resistance.

Cathelicidins are a gene family of antimicrobial peptides produced as inactive precursors. Signal peptidase removes the N-terminal signal sequence, while peptidylglycine alpha-amidating monooxygenase often amidates and cleaves the C-terminal region. Removal of the cathelin domain liberates the active antimicrobial peptide. For mammalian sequences, this cleavage usually occurs through the action of elastase, but other tissue-specific processing enzymes may also operate. Once released, these bioactive peptides are susceptible to proteolytic degradation. We propose that some mature cathelicidins are naturally resistant to proteases due to their unusual primary structures. Among mammalian cathelicidins, proline-rich sequences should resist attack by serine proteases because proline prevents cleavage of the scissile bond. In hagfish cathelicidins, the unusual amino acid bromotryptophan may make the active peptides less susceptible to proteolysis for steric reasons. Such protease resistance could extend the pharmacokinetic lifetimes of cathelicidins in vivo, sustaining antimicrobial activity.

Burn Injury Reduces Neutrophil Directional Migration Speed in Microfluidic Devices

Thermal injury triggers a fulminant inflammatory cascade that heralds shock, end-organ failure, and ultimately sepsis and death. Emerging evidence points to a critical role for the innate immune system, and several studies had documented concurrent impairment in neutrophil chemotaxis with these post-burn inflammatory changes. While a few studies suggest that a link between neutrophil motility and patient mortality might exist, so far, cumbersome assays have prohibited exploration of the prognostic and diagnostic significance of chemotaxis after burn injury. To address this need, we developed a microfluidic device that is simple to operate and allows for precise and robust measurements of chemotaxis speed and persistence characteristics at single-cell resolution. Using this assay, we established a reference set of migration speed values for neutrophils from healthy subjects. Comparisons with samples from burn patients revealed impaired directional migration speed starting as early as 24 hours after burn injury, reaching a minimum at 72–120 hours, correlated to the size of the burn injury and potentially serving as an early indicator for concurrent infections. Further characterization of neutrophil chemotaxis using this new assay may have important diagnostic implications not only for burn patients but also for patients afflicted by other diseases that compromise neutrophil functions.

Stem cells and burns: review and therapeutic implications.

Despite significant advances in burn resuscitation and wound care over the past 30 years, morbidity and mortality from thermal injury remain high. Limited donor skin in severely burned patients hinders effective wound excision and closure, leading to infectious complications and prolonged hospitalizations. Even with large-volume fluid resuscitation, the systemic inflammatory response syndrome compromises end-organ perfusion in burn patients, with resultant multiorgan failure. Stem cells, which enhance wound healing and counteract systemic inflammation, now offer potential therapies for these challenges. Through a review of the literature, this article seeks to illustrate applications of stem cell therapy to burn care and to highlight promising areas of research.

Adequate Nutrition May Get You Home Effect of Caloric/Protein Deficits on the Discharge Destination of Critically Ill Surgical Patients

BACKGROUNDnMacronutrient deficit in the surgical intensive care unit (ICU) is associated with worse in-hospital outcomes. We hypothesized that increased caloric and protein deficit is also associated with a lower likelihood of discharge to home vs transfer to a rehabilitation or skilled nursing facility.nnnMATERIALS AND METHODSnAdult surgical ICU patients receiving >72 hours of enteral nutrition (EN) between March 2012 and May 2014 were included. Patients with absolute contraindications to EN, <72-hour ICU stay, moribund state, EN prior to surgical ICU admission, or previous ICU admission within the same hospital stay were excluded. Subjects were dichotomized by cumulative caloric (<6000 vs ≥ 6000 kcal) and protein deficit (<300 vs ≥ 300 g). Baseline characteristics and outcomes were compared using Wilcoxon rank and χ(2) tests. To test the association of macronutrient deficit with discharge destination (home vs other), we performed a logistic regression analysis, controlling for plausible confounders.nnnRESULTSnIn total, 213 individuals were included. Nineteen percent in the low-caloric deficit group were discharged home compared with 6% in the high-caloric deficit group (P = .02). Age, body mass index (BMI), Acute Physiology and Chronic Health Evaluation II (APACHE II), and initiation of EN were not significantly different between groups. On logistic regression, adjusting for BMI and APACHE II score, the high-caloric and protein-deficit groups were less likely to be discharged home (odds ratio [OR], 0.28; 95% confidence interval [CI], 0.08-0.96; P = .04 and OR, 0.29; 95% CI, 0.0-0.89, P = .03, respectively).nnnCONCLUSIONSnIn surgical ICU patients, inadequate macronutrient delivery is associated with lower rates of discharge to home. Improved nutrition delivery may lead to better clinical outcomes after critical illness.

Intraoperative Adverse Events in Abdominal Surgery: What Happens in the Operating Room Does Not Stay in the Operating Room

Objective: We sought to assess the impact of intraoperative adverse events (iAEs) on 30-day postoperative mortality, 30-day postoperative morbidity, and postoperative length of stay (LOS) among patients undergoing abdominal surgery. We hypothesized that iAEs would be associated with significant increases in each outcome. Summary of Background Data: The relationship between iAEs and postoperative clinical outcomes remains largely unknown. Methods: The 2007 to 2012 institutional ACS-NSQIP and administrative databases for abdominal surgeries were matched then screened for iAEs using the Agency for Healthcare Research and Qualitys 15th Patient Safety Indicator, “Accidental Puncture/Laceration”. Each chart flagged during the initial screen was then manually reviewed to confirm whether an iAE occurred. Univariate then multivariable logistic regression models were constructed to assess the independent impact of iAEs on 30-day mortality, 30-day morbidity, and prolonged (≥7 days) postoperative LOS, controlling for preoperative/intraoperative variables (eg, age, comorbidities, ASA, wound classification), procedure type (eg, laparoscopic vs open, intestinal, foregut, hepatopancreaticobiliary vs abdominal wall procedure), and complexity (eg, adhesions; relative value units). Propensity score analyses were conducted with each iAE patient matched with 5 non-iAE patients. Sensitivity analyses were performed. Results: A total of 9288 cases were included; 183 had iAEs. Most iAEs consisted of bowel (44%) or vessel (29%) injuries and were addressed intraoperatively (92%). In multivariable analyses, iAEs were independently associated with increased 30-day mortality [OR = 3.19, 95% confidence interval (CI) 1.52–6.71, P = 0.002], 30-day morbidity (OR = 2.68, 95% CI 1.89–3.81, P < 0.001), and prolonged postoperative LOS (OR = 1.85, 95% CI 1.27–2.70, P = 0.001). Postoperative complications associated with iAEs included deep/organ-space surgical site infection (OR = 1.94, 95% CI 1.20–3.14), P = 0.007), sepsis (OR = 2.14, 95% CI 1.32–3.47, P = 0.002), pneumonia (OR = 2.18, 95% CI 1.11–4.26, P = 0.023), and failure to wean ventilator (OR = 3.88, 95% CI 2.17–6.95, P < 0.001). Propensity score matching confirmed these findings, as did multiple sensitivity analyses. Conclusions: iAEs are independently associated with substantial increases in postoperative mortality, morbidity, and prolonged LOS. Quality improvement efforts should focus on iAE prevention, mitigation of harm after iAEs occur, and risk/severity-adjusted iAE tracking and benchmarking.

A hierarchical task analysis of cricothyroidotomy procedure for a virtual airway skills trainer simulator

BACKGROUNDnDespite the critical importance of cricothyroidotomy (CCT) for patient in extremis, clinical experience with CCT is infrequent, and current training tools are inadequate. The long-term goal is to develop a virtual airway skills trainer that requires a thorough task analysis to determine the critical procedural steps, learning metrics, and parameters for assessment.nnnMETHODSnHierarchical task analysis is performed to describe major tasks and subtasks for CCT. A rubric for performance scoring for each task was derived, and possible operative errors were identified.nnnRESULTSnTime series analyses for 7 CCT videos were performed with 3 different observers. According to Pearsons correlation tests, 3 of the 7 major tasks had a strong correlation between their task times and performance scores.nnnCONCLUSIONSnThe task analysis forms the core of a proposed virtual CCT simulator, and highlights links between performance time and accuracy when teaching individual surgical steps of the procedure.

Gene Expression of Proresolving Lipid Mediator Pathways Is Associated With Clinical Outcomes in Trauma Patients.

Objectives:Specialized proresolving lipid mediators have emerged as powerful modulators of inflammation and activators of resolution. Animal models show significant benefits of specialized proresolving lipid mediators on survival and wound healing after major burn trauma. To date, no studies have investigated specialized proresolving lipid mediators and their relation to other lipid mediator pathways in humans after trauma. Here we determine if patients with poor outcomes after trauma have dysregulated lipid mediator pathways. Design:We studied blood leukocyte expression of 18 genes critical to the synthesis, signaling, and metabolism of specialized proresolving lipid mediators and proinflammatory lipid mediators, and we correlated these expression patterns with clinical outcomes in trauma patients from the Inflammation and the Host Response to Injury study. Setting:Seven U.S. medical trauma centers. Subjects:Ninety-six patients enrolled in the Inflammation and Host Response to Injury study, after blunt trauma and unambiguously classified as having uncomplicated or complicated recoveries. Twenty-eight healthy volunteers were enrolled as controls. Interventions:None. Measurements and Main Results:Within each patient, the 18 genes of interest were used to calculate scores for distinct families of lipid mediators, including resolvins, lipoxins, prostaglandins, and leukotrienes, as well as leukotriene to resolvin score ratios. Scores were built using a simple weighting scheme, taking into consideration both dependent and independent activities of enzymes and receptors responsible for lipid mediator biosynthesis and function. Individually, ALOX12, PTGS2, PTGES, PTGDS, ALOX5AP, LTA4H, FPR2, PTGER2, LTB4R, HPGD, PTGR1, and CYP4F3 were expressed differentially over 28 days posttrauma between patients with uncomplicated and complicated recoveries (p < 0.05). When all genes were combined into scores, patients with uncomplicated recoveries had differential and higher resolvin scores (p < 0.001) and lower leukotriene scores (p < 0.001). A final combined ratio was calculated for each patient, and posttrauma leukotriene score to resolvin score ratios were significantly lower in patients with uncomplicated clinical courses (p < 0.001). Conclusions:proresolving lipid mediator lipidomics and/or protein expression, and identifying associated therapeutic targets, may influence the clinical management of trauma patients.

Diagnosis of sepsis from a drop of blood by measurement of spontaneous neutrophil motility in a microfluidic assay

Current methods for the diagnosis of sepsis have insufficient precision, causing regular misdiagnoses. Microbiological tests can help to diagnose sepsis, but are usually too slow to have an impact on timely clinical decision-making. Neutrophils have a high sensitivity to infections, yet measurements of neutrophil surface markers, genomic changes and phenotype alterations have had only a marginal effect on sepsis diagnosis. Here, we report a microfluidic assay that measures, from one droplet of diluted blood, the spontaneous motility of neutrophils in the presence of plasma. We measured the performance of the assay in two independent cohorts of critically ill patients suspected of sepsis. Using data from a first cohort, we developed a machine-learning-based scoring system (sepsis score) that segregated patients with sepsis from those without sepsis. We then validated the sepsis score in a double-blind, prospective case–control study. For the 42 patients across the two cohorts, the assay identified sepsis patients with 97% sensitivity and 98% specificity. The neutrophil assay could potentially be used to accurately diagnose and monitor sepsis in larger populations of at-risk patients.A microfluidic assay that identifies sepsis from a single droplet of diluted blood by measuring the spontaneous motility of neutrophils showed 97% sensitivity and 98% specificity in two independent patient cohorts.

Derivation and validation of a novel Emergency Surgery Acuity Score (ESAS).

BACKGROUND There currently exists no preoperative risk stratification system for emergency surgery (ES). We sought to develop an Emergency Surgery Acuity Score (ESAS) that helps predict perioperative mortality in ES patients. METHODS Using the 2011 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database (derivation cohort), we identified all surgical procedures that were classified as “emergent.” A three-step methodology was then performed. First, multiple logistic regression models were created to identify independent predictors (e.g., patient demographics, comorbidities, and preoperative laboratory variables) of 30-day mortality in ES. Second, based on the relative impact of each identified predictor (i.e., odds ratio), using weighted averages, a novel score was derived. Third, using the 2012 ACS-NSQIP database (validation cohort), the score was validated by calculating its C statistic and evaluating its ability to predict 30-day mortality. RESULTS From 280,801 NSQIP cases, 18,439 ES cases were analyzed, of which 1,598 (8.7%) resulted in death at 30 days. The multiple logistic regression analyses identified 22 independent predictors of mortality. Based on the relative impact of these predictors, ESAS was derived with a total score range of 0 to 29. ESAS had a C statistic of 0.86; the probability of death at 30 days gradually increased from 0% to 36% then 100% at scores of 0, 11, and 22, respectively. In the validation phase, 19,552 patients were included, the mortality rate was 7.2%, and the ESAS C statistic stayed at 0.86. CONCLUSION We have therefore developed and validated a novel score, ESAS, that accurately predicts mortality in ES patients. Such a score could prove useful for (1) preoperative patient counseling, (2) identification of patients needing close postoperative monitoring, and (3) risk adjustment in any efforts at benchmarking the quality of ES. LEVEL OF EVIDENCE Prognostic/epidemiologic study, level III.

The nature, patterns, clinical outcomes, and financial impact of intraoperative adverse events in emergency surgery

BACKGROUNDnLittle is known about intraoperative adverse events (iAEs) in emergency surgery (ES). We sought to describe iAEs in ES and to investigate their clinical and financial impact.nnnMETHODSnThe 2007 to 2012 administrative and American College of Surgeons-National Surgical Quality Improvement Program databases at our tertiary academic center were: (1) linked, (2) queried for all ES procedures, and then (3) screened for iAEs using the ICD-9-CM-based Patient Safety Indicator accidental puncture/laceration. Flagged cases were systematically reviewed to: (1) confirm or exclude the occurrence of iAEs (defined as inadvertent injuries during the operation) and (2) extract additional variables such as procedure type, approach, complexity (measured by relative value units), need for adhesiolysis, and extent of repair. Univariate and multivariate analyses were performed to assess the independent impact of iAEs on 30-day morbidity, mortality, and hospital charges.nnnRESULTSnOf a total of 9,288 patients, 1,284 (13.8%) patients underwent ES, of which 23 had iAEs (1.8%); 18 of 23 (78.3%) of the iAEs involved the small bowel or spleen, 10 of 23 (43.5%) required suture repair, and 8 of 23 (34.8%) required tissue or organ resection. Compared with those without iAEs, patients with iAEs were older (median age 62 vs 50; P = .04); their procedures were more complex (total relative value unit 46.7, interquartile range [27.5 to 52.6] vs 14.5 [.5 to 30.2]; P < .001), longer in duration (>3xa0hours: 52% vs 8%; P < .001), and more often required adhesiolysis (39.1% vs 13.5% P = .001). Patients with iAEs had increased total charges (