Rachel J. Santora

Organ crosstalk: the role of the kidney.

Purpose of reviewAcute kidney injury (AKI) continues to contribute significantly to morbidity and mortality in the ICU setting, especially when associated with distant organ dysfunction. There is increasing evidence that AKI directly contributes to organ dysfunction in lung, brain, liver, heart and other organs. This review will examine our current understanding of the deleterious organ crosstalk in the critically ill, which can provide a framework for developing novel therapeutics. Recent findingsThe majority of studies correlating AKI with distant organ dysfunction have demonstrated the pathophysiological importance of proinflammatory and proapoptotic pathways as well as oxidative stress and reactive oxygen species (ROS) production. Leukocyte activation and infiltration, changes in levels of soluble factors such as cytokines and chemokines, and regulation of cell death in extra-renal organs are potentially important mechanisms by which AKI modulates multiorgan dysfunction. SummaryThere is increasing knowledge of AKI and deleterious interorgan crosstalk that arises, at least in part, due to the imbalance of immune, inflammatory, and soluble mediator metabolism that attends severe insults to the kidney. Further studies can build on these new mechanistic observations to develop strategies to improve outcomes in the critically ill patient.

Utility of Removable Esophageal Covered Self-Expanding Metal Stents for Leak and Fistula Management

BACKGROUND Esophageal or gastric leakage from anastomotic wound dehiscence, perforation, staple line dehiscence, or trauma can be a devastating event. Traditional therapy has often consisted of either surgical repair for rapidly diagnosed leaks or diversion for more complicated cases, commonly associated with a delayed diagnosis. This study summarizes our experience treating leaks or fistulas with novel, covered self-expanding metal stents (cSEMS). The primary objective of this study was to determine the efficacy and safety of covered self-expanding metal stents when used to treat complicated leaks and fistulas. METHODS Over 15 months, 25 patients with esophageal or gastric leaks were evaluated for stenting as primary treatment. A prospective database was used to collect data. Stents were placed endoscopically, with contrast evaluation used for leak evaluation. Patients who did not improve clinically after stenting or whose leak could not be sealed underwent operative management. RESULTS During a mean follow-up of 15 months, 23 of the 25 patients with esophageal or gastric leaks during a 15-month period were managed with endoscopic stenting as primary treatment. Healing occurred in patients who were stented for anastomotic leakage after gastric bypass or sleeve gastrectomy (n = 10). One patient with three esophageal iatrogenic perforations healed with stenting. Eight patients successfully avoided esophageal diversion and healed with stenting and adjunctive therapy. Two of the 4 patients with tracheoesophageal fistulas sealed with the assistance of a new pexy technique to prevent stent migration; 1 additional patient had this same technique used to successfully heal an upper esophageal perforation. CONCLUSIONS Esophageal leaks and fistulas can be effectively managed with cSEMS as a primary modality. The potential benefits of esophageal stenting are healing without diversion or reconstruction and early return to an oral diet.

Molecular Mechanisms of Pharmaconutrients

Nutritional supplementation has become the standard of care for management of critically ill patients. Traditionally, nutritional support in this patient population was intended to replete substrate deficiencies secondary to stress-induced catabolism. Recognition of the influence of certain nutrients on the immune and inflammatory response of the critically ill has led to the evolution of more sophisticated nutritional strategies and concepts. Administration of immune-enhancing formulas supplemented with a combination of glutamine, arginine, omega-3 fatty acids (omega-3 FA), and nucleotides have been shown in most studies to reduce infectious outcomes. More recently, the separation of nutritional support from the provision of key nutrients has led to a further appreciation of the immunomodulatory and anti-inflammatory benefits of isolated nutrients, such as glutamine and antioxidants. The purpose of this article is to review the molecular mechanisms that are unique to each class of frequently utilized nutrients. A better understanding of the specific molecular targets of immunonutrients will facilitate application of more refined nutritional therapies in critically ill patients.

Outcomes and economic analysis of routine preoperative 4-dimensional ct for surgical intervention in de novo primary hyperparathyroidism: Does clinical benefit justify the cost?

BACKGROUND Preoperative imaging in patients with primary hyperparathyroidism provides important localization information. Although 4-dimensional neck CT (4DCT) can precisely localize hyperfunctioning parathyroid tissue, the contribution of 4DCT to overall cost, operating room time, and hospital stay is unknown. STUDY DESIGN Records of 535 patients with primary hyperparathyroidism who underwent parathyroidectomy at our institution from 1996 to 2010 were reviewed. All patients had preoperative cervical ultrasonography and sestamibi scanning, and most (78.9%) underwent preoperative 4DCT. A decision tree was constructed to compare extent of procedure, operating room time, length of stay, failure rate, and total cost of each strategy (with and without 4DCT). Costs were determined by 2010 Medicare reimbursement. RESULTS For patients with and without preoperative 4DCT, respectively, mean operating room time (64.4 vs 61.4 minutes; p = 0.58) and failure rate (1.9% vs 4.4%; p = 0.12) were not significantly different. Length of stay was higher in the no-CT cohort (0.61 vs 0.23 days; p < 0.001). Patients with a preoperative 4DCT were significantly more likely to undergo a limited parathyroidectomy (90.3% vs 80.5%; p = 0.004). Mean cost of care per patient in the CT and no-CT cohorts was

Lung T Lymphocyte Trafficking and Activation during Ischemic Acute Kidney Injury

6,572 and

TNFR1-dependent pulmonary apoptosis during ischemic acute kidney injury

6,306, respectively. CONCLUSIONS The introduction of routine 4DCT into the preoperative workup for surgical intervention in primary hyperparathyroidism does not appear to shorten operating room time or decrease failure rate significantly. However, preoperative 4DCT is associated with shorter hospital stays and improved rates of minimally invasive parathyroidectomy. This clinical benefit must be weighed against the increased cost associated with routine preoperative 4DCT.

Therapeutic distant organ effects of regional hypothermia during mesenteric ischemia-reperfusion injury.

Despite advances in renal replacement therapy, the mortality rate for acute kidney injury (AKI) remains unacceptably high, likely owing to extrarenal organ dysfunction. Kidney ischemia–reperfusion injury (IRI) activates cellular and soluble mediators that facilitate organ crosstalk and induce caspase-dependent lung apoptosis and injury through a TNFR1-dependent pathway. Given that T lymphocytes mediate local IRI in the kidney and are known to drive TNFR1-mediated apoptosis, we hypothesized that T lymphocytes activated during kidney IRI would traffic to the lung and mediate pulmonary apoptosis during AKI. In an established murine model of kidney IRI, we identified trafficking of CD3+ T lymphocytes to the lung during kidney IRI by flow cytometry and immunohistochemistry. T lymphocytes were primarily of the CD3+CD8+ phenotype; however, both CD3+CD4+ and CD3+CD8+ T lymphocytes expressed CD69 and CD25 activation markers during ischemic AKI. The activated lung T lymphocytes did not demonstrate an increased expression of intracellular TNF-α or surface TNFR1. Kidney IRI induced pulmonary apoptosis measured by caspase-3 activation in wild-type controls, but not in T cell-deficient (Tnu/nu) mice. Adoptive transfer of murine wild-type T lymphocytes into Tnu/nu mice restored the injury phenotype with increased cellular apoptosis and lung microvascular barrier dysfunction, suggesting that ischemic AKI-induced pulmonary apoptosis is T cell dependent. Kidney–lung crosstalk during AKI represents a complex biological process, and although T lymphocytes appear to serve a prominent role in the interorgan effects of AKI, further experiments are necessary to elucidate the specific role of activated T cells in modulating pulmonary apoptosis.

Enteral arginine modulates inhibition of AP-1/c-Jun by SP600125 in the postischemic gut.

Despite advancements in renal replacement therapy, the mortality rate for acute kidney injury (AKI) remains unacceptably high, likely due to remote organ injury. Kidney ischemia-reperfusion injury (IRI) activates cellular and soluble mediators that incite a distinct pulmonary proinflammatory and proapoptotic response. Tumor necrosis factor receptor 1 (TNFR1) has been identified as a prominent death receptor activated in the lungs during ischemic AKI. We hypothesized that circulating TNF-α released from the postischemic kidney induces TNFR1-mediated pulmonary apoptosis, and we aimed to elucidate molecular pathways to programmed cell death. Using an established murine model of kidney IRI, we characterized the time course for increased circulatory and pulmonary TNF-α levels and measured concurrent upregulation of pulmonary TNFR1 expression. We then identified TNFR1-dependent pulmonary apoptosis after ischemic AKI using TNFR1-/- mice. Subsequent TNF-α signaling disruption with Etanercept implicated circulatory TNF-α as a key soluble mediator of pulmonary apoptosis and lung microvascular barrier dysfunction during ischemic AKI. We further elucidated pathways of TNFR1-mediated apoptosis with NF-κB (Complex I) and caspase-8 (Complex II) expression and discovered that TNFR1 proapoptotic signaling induces NF-κB activation. Additionally, inhibition of NF-κB (Complex I) resulted in a proapoptotic phenotype, lung barrier leak, and altered cellular flice inhibitory protein signaling independent of caspase-8 (Complex II) activation. Ischemic AKI activates soluble TNF-α and induces TNFR1-dependent pulmonary apoptosis through augmentation of the prosurvival and proapoptotic TNFR1 signaling pathway. Kidney-lung crosstalk after ischemic AKI represents a complex pathological process, yet focusing on specific biological pathways may yield potential future therapeutic targets.

Computerized clinical decision support for traumatic shock resuscitation.

INTRODUCTION Mesenteric ischemia-reperfusion injury (IRI) leads to systemic inflammation and multiple organ failure in clinical and laboratory settings. We investigated the lung structural, functional, and genomic response to mesenteric IRI with and without regional intraischemic hypothermia (RIH) in rodents and hypothesized that RIH would protect the lung and preferentially modulate the distant organ transcriptome under these conditions. METHODS Sprague-Dawley rats underwent sham laparotomy or superior mesenteric artery occlusion (SMAO) for 60 minutes with or without RIH. Gut temperature was maintained at 15°-20°C during SMAO, and systemic normothermia (37°C) was maintained throughout the study period. At 6 or 24 hours, lung tissue was collected for (1) histology, (2) myeloperoxidase activity, (3) bronchoalveolar lavage (BAL) fluid protein concentrations, (4) lung wet/dry ratios, and (5) total RNA isolation and hybridization to Illuminas Sentrix BeadChips (>22,000 probes) for gene expression profiling. Significantly affected genes (false discovery rate <5% and fold change ≥1.5) were linked to gene ontology (GO) terms using MAPPFinder, and hypothermia-suppressed genes were further analyzed with Pubmatrix. RESULTS Mesenteric IRI-induced lung injury, as evidenced by leukocyte trafficking, alveolar hemorrhage, and increased BAL protein and wet/dry ratios, and activated a proinflammatory lung transcriptome compared with sham. In contrast, rats treated with RIH exhibited lung histology, BAL protein, and wet/dry ratios similar to sham. At 6 hours, GO analysis identified 232 hypothermia-suppressed genes related to inflammation, innate immune response, and cell adhesion, and 33 hypothermia-activated genes related to lipid and amine metabolism and defense response. Quantitative real-time polymerase chain reaction validated select array changes in top hypothermia-suppressed genes lipocalin-2 (lcn-2) and chemokine ligand 1 (CXCL-1), prominent genes associated with neutrophil activation and trafficking. CONCLUSIONS Therapeutic hypothermia during SMAO provides distant organ protection and preferentially modulates the IRI-activated transcriptome in the rat lung. This study identifies potential novel diagnostic and therapeutic targets of mesenteric IRI and provides a platform for further mechanistic study of hypothermic protection at the cellular and subcellular level.

HB-EGF and Mesenteric Ischemia

We previously demonstrated that enteral arginine increased c-Jun/activator protein-1 (AP-1) DNA-binding activity and iNOS expression in a rodent model of mesenteric ischemia/reperfusion (I/R). The objective of this study was to specifically investigate the role of AP-1 in arginine’s deleterious effect on the postischemic gut. We hypothesized that AP-1 inhibition would mitigate the effects of arginine. Using a rodent model of mesenteric I/R we demonstrated that gut neutrophil infiltration, activity of c-Jun/AP-1, as well as iNOS expression were increased by I/R and further increased by arginine while lessened by inhibition of c-Jun using the pharmacologic c-Jun N-terminal kinase inhibitor, SP600125. Similar results were demonstrated using a cell culture model of oxidant stress in IEC-6 cells. Importantly, effects of SP600125 were comparable to those of c-Jun silencing. Lastly, the specific iNOS inhibitor, 1400W, had no effect on either AP-1 or c-Jun. In conclusion, SP600125 attenuated the activity of c-Jun/AP-1, iNOS expression, and neutrophil infiltration induced by arginine following mesenteric I/R. Our data suggest that AP-1 inhibition mitigates the injurious inflammatory effects of arginine in the postischemic gut. Further investigation into the pathologic role of enteral argninine in the postischemic gut is warranted.