Jeffrey M. Dodd-o

Prospective, randomized, controlled clinical trial comparing traditional versus reduced tidal volume ventilation in acute respiratory distress syndrome patients

OBJECTIVE To assess the safety and potential efficacy of a mechanical ventilation strategy designed to reduce stretch-induced lung injury in acute respiratory distress syndrome. DESIGN Prospective, randomized, controlled clinical trial. SETTING Eight intensive care units in four teaching hospitals. PATIENTS Fifty-two patients with acute respiratory distress syndrome. INTERVENTIONS Traditional tidal volume patients: tidal volume 10-12 mL/kg ideal body weight, reduced if inspiratory plateau pressure was > 55 cm H2O (7.3 kPa). Small tidal volume patients: tidal volume 5-8 mL/kg ideal body weight, to keep plateau pressure < 30 cm H2O (4.0 kPa). MEASUREMENTS AND MAIN RESULTS Mean tidal volumes during the first 5 days in traditional and small tidal volume patients were 10.2 and 7.3 mL/kg, respectively (p < .001), with mean plateau pressure = 30.6 and 24.9 cm H2O (3.3 kPa), respectively (p < .001). There were no significant differences in requirements for positive end-expiratory pressure or FIO2, fluid intakes/outputs, requirements for vasopressors, sedatives, or neuromuscular blocking agents, percentage of patients that achieved unassisted breathing, ventilator days, or mortality. CONCLUSIONS The reduced tidal volume strategy used in this study was safe. Failure to observe beneficial effects of small tidal volume ventilation treatment in important clinical outcome variables may have occurred because a) the sample size was too small to discern small treatment effects; b) the differences in tidal volumes and plateau pressures were modest; or c) reduced tidal volume ventilation is not beneficial.

Potential paracrine role of the pericardium in the regulation of cardiac function

OBJECTIVE Both coronary and endocardial endothelium regulate cardiac contractile function via paracrine pathways. We investigated whether pericardial fluid (PF) and pericardial mesothelial cells (PMC) could exert a similar paracrine action. METHODS Both PF and PMC were extracted from sheep pericardial space. Endothelin-1, prostaglandins and atrial natriuretic factor were measured in PF in vivo. In the other hand, PMC were grown on T-75 flasks and microcarrier beads to investigate endothelin-1, nitric oxide and prostaglandin pathways in vitro. In addition, effects of PF and PMC effluent were tested on adult rat cardiac myocyte contraction in vitro. RESULTS In vitro, cultured PMC expressed endothelin-1 mRNA but not the endothelial nitric oxide synthase III, and released endothelin-1 and prostaglandins. Both PF and cultured PMC superfusate induced a potent, rapidly reversible decrease in the shortening of isolated rat cardiac myocytes. This effect was not associated with changes in intracellular calcium. In vivo, prostaglandins, atrial natriuretic factor and endothelin were present in PF. A greater concentration of atrial natriuretic factor was present in PF than in serum, suggesting molecular diffusion from the myocardium to PF. Preliminary results show that the instillation of vasoactive agents into the pericardial space of dogs rapidly alter coronary and systemic vascular tone, consistent with a molecular diffusion of these substances from PF into the myocardium and circulation. CONCLUSIONS In addition to its mechanical role, the pericardium may contribute to the integration and the regulation of cardiovascular function via a paracrine mechanism.

Interactive Effects of Mechanical Ventilation and Kidney Health on Lung Function in an In Vivo Mouse Model

We hypothesized that the influence of acute kidney injury (AKI) on the sensitivity of the lung to an injurious process varies with the severity of the injurious process. Thus, we thought that AKI would exacerbate lung injury from low degrees of lung trauma but attenuate lung injury from higher degrees of lung trauma. C57BL/6 mice underwent AKI (30-min kidney ischemia) or sham surgery, followed at 24 h by 4 h of spontaneous breathing (SB), mechanical ventilation with low tidal volume (7 ml/kg, LTV), or mechanical ventilation with high tidal volume (30 ml/kg, HTV). Compared with LTV, median bronchoalveolar lavage (BAL) protein leak was significantly lower with SB and greater with HTV in both sham and AKI mice. Compared with LTV, median Evans blue dye-labeled albumin extravasation in lungs (L-EBD) was also significantly lower with SB and greater with HTV. L-EBD showed a significant interaction between ventilatory mode and kidney health, such that AKI attenuated the L-EBD rise seen in HTV vs. LTV sham mice. An interaction between ventilatory mode and kidney health could also be seen in BAL neutrophil number (PMN). Thus, AKI attenuated the BAL PMN rise seen in HTV vs. LTV sham mice. These data support the presence of a complex interaction between mechanical ventilation and AKI in which the sensitivity of the lung to trauma varies with the magnitude of the trauma and may involve a modification of pulmonary neutrophil activity by AKI.

The role of natriuretic peptide receptor-A signaling in unilateral lung ischemia-reperfusion injury in the intact mouse

Ischemia-reperfusion (IR) causes human lung injury in association with the release of atrial and brain natriuretic peptides (ANP and BNP), but the role of ANP/BNP in IR lung injury is unknown. ANP and BNP bind to natriuretic peptide receptor-A (NPR-A) generating cGMP and to NPR-C, a clearance receptor that can decrease intracellular cAMP. To determine the role of NPR-A signaling in IR lung injury, we administered the NPR-A blocker anantin in an in vivo SWR mouse preparation of unilateral lung IR. With uninterrupted ventilation, the left pulmonary artery was occluded for 30 min and then reperfused for 60 or 150 min. Anantin administration decreased IR-induced Evans blue dye extravasation and wet weight in the reperfused left lung, suggesting an injurious role for NPR-A signaling in lung IR. In isolated mouse lungs, exogenous ANP (2.5 nM) added to the perfusate significantly increased the filtration coefficient sevenfold only if lungs were subjected to IR. This effect of ANP was also blocked by anantin. Unilateral in vivo IR increased endogenous plasma ANP, lung cGMP concentration, and lung protein kinase G (PKG(I)) activation. Anantin enhanced plasma ANP concentrations and attenuated the increase in cGMP and PKG(I) activation but had no effect on lung cAMP. These data suggest that lung IR triggered ANP release and altered endothelial signaling so that NPR-A activation caused increased pulmonary endothelial permeability.

Upregulation of hypoxia-induced mitogenic factor in bacterial lipopolysaccharide-induced acute lung injury

Hypoxia‐induced mitogenic factor (HIMF), also known as FIZZ1 (found in inflammatory zone), plays important roles in lung inflammation. We found that intraperitoneal injection of lipopolysaccharide (LPS) induced intensive HIMF production exclusively in mouse lung, but not in the heart, liver, spleen or kidney. This HIMF production, at least partly, contributes to LPS‐induced vascular cell adhesion molecule‐1 (VCAM‐1) upregulation and mononuclear cell sequestration to lung parenchyma, while protecting alveolar type II cells from LPS‐resulted decrease in surfactant protein‐C production and cell death. These data indicate that HIMF participates in LPS‐induced acute lung injury and inflammation through modulating VCAM‐1 and SP‐C expression.

Endothelium‐independent relaxation of aortic rings by the nitric oxide synthase inhibitor diphenyleneiodonium

The flavoprotein binder diphenyleneiodonium (DPI) is a potent, irreversible inhibitor of nitric oxide synthase (NOS), but produces only a transient pressor response following systemic administration to animals, despite evidence of persistent NOS inhibition. To characterize further the effects of DPI on vascular tone, isometric tension was recorded from rat isolated aortic rings mounted between steel wires in an organ bath. The NOS inhibitor NG‐nitro‐l‐arginine methyl ester (l‐NAME, 1 mm) initiated an additional contraction of prostaglandin F2α‐preconstricted rings with endothelium which was sustained throughout the period of l‐NAME exposure (+234±39% at 15 min). In contrast, addition of DPI (5 μm) to rings with endothelium produced a transient initial contraction (+111±27% at 2 min) followed by a more sustained relaxation (−27±19% at 15 min, P<0.001 vs l‐NAME). The contraction to DPI was also observed in rings without endothelium, was abolished by l‐NAME pretreatment, and was unaffected by the α‐adrenoreceptor inhibitor prazosin. Relaxation in response to DPI was not inhibited by endothelium removal or by pretreatment with either l‐NAME or with the ATP‐sensitive potassium channel blocker glibenclamide. The endothelium‐independent relaxation to DPI was inhibited at 23°C and its time course was delayed by pretreatment with the guanylate cyclase inhibitor methylene blue. Thus, in addition to a transient initial contraction due to NOS inhibition, DPI produces an endothelium‐independent, temperature‐dependent relaxation which appears in part due to activation of guanylate cyclase. This relaxant effect of DPI may explain the transient nature of its pressor effect in vivo despite sustained NOS inhibition.

CD8+IL-17+ T cells mediate neutrophilic airway obliteration in T-bet-deficient mouse lung allograft recipients

Acute cellular rejection is a known risk factor for the development of obliterative bronchiolitis, which limits the long-term survival of lung transplant recipients. However, the T cell effector mechanisms in both of these processes remain incompletely understood. Using the mouse orthotopic lung transplant model, we investigated whether C57BL/6 T-bet(-/-) recipients of major histocompatibility complex (MHC)-mismatched BALB/c lung grafts develop rejection pathology and allospecific cytokine responses that differ from wild-type mice. T-bet(-/-) recipients demonstrated vigorous allograft rejection at 10 days, characterized by neutrophilic inflammation and predominantly CD8(+) T cells producing allospecific IL-17 and/or IFN-γ, in contrast to IFN-γ-dominant responses in WT mice. CD4(+) T cells produced IL-17 but not IFN-γ responses in T-bet(-/-) recipients, in contrast to WT controls. Costimulation blockade using anti-CD154 Ab significantly reduced allospecific CD8(+)IFN-γ(+) responses in both T-bet(-/-) and WT mice but had no attenuating effect on lung rejection pathology in T-bet(-/-) recipients or on the development of obliterative airway inflammation that occurred only in T-bet(-/-) recipients. However, neutralization of IL-17A significantly attenuated costimulation blockade-resistant rejection pathology and airway inflammation in T-bet(-/-) recipients. In addition, CXCL1 (neutrophil chemokine) was increased in T-bet(-/-) allografts, and IL-17 induced CXCL1 from mouse lung epithelial cells in vitro. Taken together, our data show that T-bet-deficient recipients of complete MHC-mismatched lung allografts develop costimulation blockade-resistant rejection characterized by neutrophilia and obliterative airway inflammation that is predominantly mediated by CD8(+)IL-17(+) T cells. Our data support T-bet-deficient mouse recipients of lung allografts as a viable animal model to study the immunopathogenesis of small airway injury in lung transplantation.

Induction of Major Histocompatibility Complex-mismatched Mouse Lung Allograft Acceptance With Combined Donor Bone Marrow: Lung Transplant Using a 12-Hour Nonmyeloablative Conditioning Regimen.

Background Despite broad and intense conventional immunosuppression, long-term survival after lung transplantation lags behind that for other solid organ transplants, primarily because of allograft rejection. Therefore, new strategies to promote lung allograft acceptance are urgently needed. The purpose of the present study was to induce allograft tolerance with a protocol compatible with deceased donor organ utilization. Methods Using the major histocompatibility complex-mismatched mouse orthotopic lung transplant model, we investigated a conditioning regimen consisting of pretransplant T cell depletion, low-dose total body irradiation and posttransplant (donor) bone marrow, and splenocyte infusion followed by posttransplantation cyclophosphamide. Results Our results show that C57BL/6 recipients of BALB/c lung allografts undergoing this complete short-duration nonmyeloablative conditioning regimen had durable lung allograft acceptance. Mice that lacked 1 or more components of this regimen exhibited significant graft loss. Mechanistically, animals with lung allograft acceptance had established higher levels of donor chimerism, lymphocyte responses which were attenuated to donor antigens but maintained to third-party antigens, and clonal deletion of donor-reactive host V&bgr; T cells. Frequencies of Foxp3+ T regulatory cells were comparable in both surviving and rejected allografts implying that their perturbation was not a dominant cell-regulatory mechanism. Donor chimerism was indispensable for sustained tolerance, as evidenced by acute rejection of allografts in established chimeric recipients of posttransplantation cyclophosphamide after a chimerism-ablating secondary recipient lymphocyte infusion. Conclusions Together, these data provide proof-of-concept for establishing lung allograft tolerance with tandem donor bone marrow transplantation using a short-duration nonmyeloablative conditioning regimen and posttransplant cyclophosphamide.

Multidisciplinary Difficult Airway Course: An Essential Educational Component of a Hospital-Wide Difficult Airway Response Program

OBJECTIVE A hospital-wide difficult airway response team was developed in 2008 at The Johns Hopkins Hospital with three central pillars: operations, safety monitoring, and education. The objective of this study was to assess the outcomes of the educational pillar of the difficult airway response team program, known as the multidisciplinary difficult airway course (MDAC). DESIGN The comprehensive, full-day MDAC involves trainees and staff from all provider groups who participate in airway management. The MDAC occurs within the Johns Hopkins Medicine Simulation Center approximately four times per year and uses a combination of didactic lectures, hands-on sessions, and high-fidelity simulation training. Participation in MDAC is the main intervention being investigated in this study. Data were collected prospectively using course evaluation survey with quantitative and qualitative components, and prepost course knowledge assessment multiple choice questions (MCQ). Outcomes include course evaluation scores and themes derived from qualitative assessments, and prepost course knowledge assessment MCQ scores. SETTING Tertiary care academic hospital center PARTICIPANTS: Students, residents, fellows, and practicing physicians from the departments of Surgery, Otolaryngology Head and Neck Surgery, Anesthesiology/Critical Care Medicine, and Emergency Medicine; advanced practice providers (nurse practitioners and physician assistants), nurse anesthetists, nurses, and respiratory therapists. RESULTS Totally, 23 MDACs have been conducted, including 499 participants. Course evaluations were uniformly positive with mean score of 86.9 of 95 points. Qualitative responses suggest major value from high-fidelity simulation, the hands-on skill stations, and teamwork practice. MCQ scores demonstrated significant improvement: median (interquartile range) pre: 69% (60%-81%) vs post: 81% (72%-89%), p < 0.001. CONCLUSIONS Implementation of a MDAC successfully disseminated principles and protocols to all airway providers. Demonstrable improvement in prepost course knowledge assessment and overwhelmingly positive course evaluations (quantitative and qualitative) suggest a critical and ongoing role for the MDAC course.

Abstract 18: Post Transplantation Cyclophosphamide Promotes Robust Immune Tolerance after Reconstructive Transplantation

22 hypothesize that IUSCT of gene modified hASCs will result in sustained FVIII transgene expression. The success of the first human IUSCT has been shown in a severe combined immunodeficiency patient that utilized paternal bone marrow (BM) derived stem cells. However, BM stem cell isolation is invasive and has a low quantitative yield. Adipose derived stem cell harvesting is minimally invasive and has a high stem cell count per gram. Here we report the safety and survivability of IUSCT of hASCs into a C57BL/6 murine model.