Biomedical subjects

H Shennib

Publications and source records attributed to H Shennib.

At least 37 records · Page 2Linked to original sources

PubMed1998

Arterial graft patency in coronary artery bypass grafting: what do we really know?

BACKGROUND: With increasing use of beating heart techniques for bypass of the left anterior descending coronary artery with the left internal mammary artery (LIMA), appropriate concerns have been raised of whether graft patency by these techniques compares favorably with conventional, arrested heart techniques. METHODS: All published articles that examine outcome efficacy of the LIMA graft to the left anterior descending coronary artery were reviewed. Because angiography has been considered the "gold standard," only those studies that included angiographic follow-up were analyzed. RESULTS: From 1972 through 1998, there have been 37 peer-reviewed publications that examined outcomes of LIMA grafting in conventional coronary bypass grafting, of which 27 contained angiographic follow-up data. The completeness of angiographic follow-up was variable, but early graft patency (< or =1 month) in studied patients ranged between 94% and 99%. Late graft patency (up to 15 years) ranged from 51% to 98%. Five recent series of minimally invasive direct coronary artery bypass grafting that contained LIMA graft patency data show early graft patency rates between 91% and 99%. CONCLUSIONS: Meaningful comparison of LIMA graft patency between arrested heart, conventional coronary artery bypass grafting, and minimally invasive direct coronary artery bypass grafting is difficult; however, early graft patency by both techniques can confidently be stated as being 90% or greater.

Coronary Angiography↗

PubMed1998

A novel charcoal-induced model of obliterative bronchiolitis-like lesions: implications of chronic nonspecific airway inflammation in the development of posttransplantation obliterative bronchiolitis.

OBJECTIVES: In this study, we describe the development of a nonallogeneic animal model of obliterative bronchiolitis-like lesions. Furthermore, we examined whether chronic rejection alone can lead to the development of obliterative bronchiolitis or whether additional nonspecific airway inflammation is required. METHODS: Part I: Rats were intratracheally injected with 0.2 ml of activated charcoal or sorbitol solution (carrier for charcoal control). Animals were put to death beginning at 2 weeks up to 20 weeks. Part II: Animals were divided into three groups: group I, underimmunosuppressed Brown Norway to Lewis lung allografts; group II, charcoal-treated underimmunosuppressed allografts; and group III, charcoal-treated rats. Animals were put to death at 3 months after transplantation. RESULTS: Part I: In charcoal-laden bronchioles, subacute nonspecific airway inflammation was detected at 2 weeks. Slow, subclinical fibroproliferation ensued during the following weeks. Obliterative bronchiolitis-like lesions were observed in 80% of charcoal-treated animals at 12 weeks. Part II: Allografts developed extensive vascular lesions consistent with acute and chronic vascular rejection. Obliterative bronchiolitis-like lesions were scarcely detected. Charcoal-treated allografts demonstrated evidence of diffuse and severe obliterative bronchiolitis-like lesions. CONCLUSIONS: Transtracheal injection of activated charcoal into native lungs results in slowly progressive airway injury and inflammation leading to obliterative airway lesions. Inadequate immunosuppression primarily results in chronic vascular rejection but not obliterative bronchiolitis. Underimmunosuppressed allografts subjected to nonspecific airway inflammation develop obliterative airway lesions that are more prominent than in native lungs. This suggests that a cofactor to chronic rejection is likely necessary for the development of lung transplant obliterative bronchiolitis.

Animals↗

PubMed1998

Immunohistochemical localization of endothelin-1 and endothelin-converting enzyme-1 in rat lung allografts.

Chronic rejection is one of the principal factors that lead to development of obliterative bronchiolitis, which is the cause of death for 50% of lung allograft recipients. To more fully comprehend the pathogenesis of chronic rejection, we investigated the expression of endothelin-1 (ET-1) and endothelin-converting enzyme-1 (ECE-1) in inadequately immuno-suppressed rat lung allografts (n = 15) at monthly intervals after transplantation and compared these findings with those in normal rat lung (n = 5), using immunohistochemistry. Throughout the posttransplantation period, inflammatory cells expressed weak to moderate immunoexpression for both peptides. Constant weak to moderate immunoexpression for both peptides was also seen in the alveolar epithelium and neovascularized endothelium. Early after transplantation the vascular endothelium demonstrated strong immunostaining compared with control sections. This immunostaining, however, was reduced to control levels at later stages of rejection. As rejection progressed, staining in the airway epithelium diminished to weak levels as compared with that in controls. These findings suggest a causal role for ET-1 and ECE-1 in the inflammatory and proliferative damage associated with chronic rejection after lung transplantation.

Animals↗

PubMed1998

Efficacy of administering an endothelin-receptor antagonist (SB209670) in ameliorating ischemia-reperfusion injury in lung allografts.

The purpose of this study was to determine whether treatment with an endothelin-1 (ET-1)-receptor antagonist could prevent ET-1-mediated ischemia-reperfusion injury and early allograft dysfunction. Eleven dogs were subjected to left lung allotransplantation. Donor lungs were preserved with modified Eurocollins solution and stored at 4 degrees C for 18 to 20 h. Animals received an intravenous infusion of either the ET-receptor antagonist SB209670 (n = 6) (15 microg/kg/min) or saline (control, n = 5), in a blinded fashion. The infusion started 30 min before transplantation and continued for up to 6 h after transplantation. Hemodynamic measurements, blood gas tensions, and plasma samples were obtained with animals functioning solely on the transplanted lung. Open-lung biopsies were obtained for wet-to-dry-weight ratios and histologic and immunohistochemical analyses. Survival at 6 h after transplantation was 40% in the control group and 100% in the treatment group. Pulmonary vascular resistance and lung tissue wet-to-dry-weight ratio were significantly lower in treated animals at 3 and 6 h after transplantation. Histology of the transplanted lungs revealed more intense airway and interstitial inflammatory infiltration and edema in the control group. Arterial and venous plasma ET-1 concentrations increased after transplantation; however, they were significantly higher in the treatment group. Immunohistochemical analysis revealed more intense ET-1 immunostaining in the airways and parenchyma of the treatment group. We conclude that treatment of lung allografts with the mixed endothelin A/endothelin B (ETA/ETB) receptor antagonist SB209670 can ameliorate ischemia-reperfusion injury, resulting in improved graft function and survival after lung transplantation.

Animals↗

PubMed1998

Postoperative pneumonia.

Thoracic surgical patients are susceptible to pneumonia because of impaired systemic and lung host defenses. The incidence of pneumonia is higher with more extensive lung resections. Current prophylactic antibiotic therapy is based primarily on general surgical experience with emphasis on wound infection, not pneumonia. With expansion of indications for lung resection to include higher risk patients, there is a need to render antibiotic prophylaxis more specific to bacteria causative of pneumonia.

Antibiotic Prophylaxis↗

PubMed1997

Evolving strategies in minimally invasive coronary artery surgery.

It is estimated that approximately 25% of cardiac surgery will be performed through minimal access by the year 2000. While original efforts focused on performing minimally invasive cardiac surgery totally thoracoscopic, and with cardiopulmonary bypass, more recent realistic approaches rely on small targeted incisions and video assisted techniques on the beating heart. Current instrumentations which provide segmental stabilization of the heart eliminate the need for cardioplegic arrest and cardiopulmonary bypass. While early results are encouraging, intermediate and long term clinical outcome and graft patency remain to be determined.

Animals↗

PubMed1997

Superior vena cava obstruction secondary to mediastinal lymphadenopathy in a patient with cystic fibrosis.

Superior vena cava (SVC) obstruction most often is a complication of malignant tumors such as lung cancer or lymphoma. The common use of long-term indwelling central venous catheters also has added to the prevalence of SVC obstruction. This report describes the first case of SVC obstruction in a patient with cystic fibrosis due to extrinsic compression from benign reactive mediastinal lymphadenopathy. Although in these circumstances intravascular thrombosis should be ruled out, extrinsic compression from mediastinal lymphadenopathy should be considered.

Adult↗

PubMed1997

Immunohistochemical characterization of inflammatory and proliferative events during chronic rejection in rat lung allografts.

BACKGROUND: Chronic rejection is assumed to be the principle cause of airway injury leading to obliterative bronchiolitis (OB) after lung transplantation (Tx). To better understand the contribution of chronic rejection in the development of OB in allografted lungs, we examined the histopathological changes and cytokine expression in inadequately immunosuppressed rat lung allografts. METHODS: Three groups of rats were studied: group I, control nontransplanted Lewis (Lew) rats (n=5); group II, syngeneic Lew-to-Lew isografts (n=25); and group III, Brown Norway-to-Lew allografts (n=25). Groups II and III received two single doses of cyclosporine on postoperative days 2-3. Transplanted animals were killed (n=5) at monthly intervals from 2 months to 6 months after Tx. Resected lungs were stained with hematoxylin and eosin, Masson's trichrome, and Van Gieson's elastin, and immunostained with antisera to interleukin (IL)-1beta, IL-8, and basic fibroblast growth factor (bFGF). The intensity of immunostaining was graded from 0 to 4 (0=no staining, 4=strong staining). RESULTS: In groups I and II, normal airways and vessels were observed. Minimal intensity and distribution of immunostaining for all markers were detected in groups I and II. Group III allografts demonstrated acute grade II-III vascular rejection with mild bronchiolar injury and inflammation at 2 months after Tx. At 6 months after Tx, all allografts demonstrated severe and diffuse chronic vascular rejection. Late airway changes consistent with OB were detected in four of five allografts, however, these lesions were expressed infrequently. Immunohistochemical findings revealed moderate to strong expression for IL-8 and bFGF over the airway epithelium, acute and chronic inflammatory cells, and fibroblasts in allografts at 2 months after Tx. Despite focal development of OB at 6 months, intensity and distribution of immunostaining significantly decreased for all three cytokine markers. CONCLUSIONS: Inadequate immunosuppression of rat lung allografts leads primarily to chronic vascular rejection but fails to induce severe and diffuse development of OB. In this animal model, cytokines IL-1beta, IL-8, and bFGF are likely to play an important role in the early inflammatory phase but not during the late proliferative events of chronic rejection.

Animals↗

PubMed1997

Immunohistochemical localization of nitric oxide synthase and the oxidant peroxynitrite in lung transplant recipients with obliterative bronchiolitis.

BACKGROUND: Obliterative bronchiolitis (OB) is a disease affecting a large percentage of lung and heart-lung transplant recipients. Histologically, the disease is characterized by inflammation, cellular proliferation, and obliteration of terminal airways. METHODS: We investigated the production of inducible and constitutive nitric oxide synthases and peroxynitrite by immunohistochemistry in the lungs of control subjects (n=14) compared with those of transplant recipients with OB (n=8). RESULTS: Strong immunoreactivity for inducible nitric oxide synthase and nitrotyrosine, a marker of protein nitration by peroxynitrite, was seen in inflammatory cells, airway epithelium, and vascular endothelium of patients with OB, compared with little immunoreactivity in control lungs. Immunoreactivity for constitutive nitric oxide synthase was abundant in the airway epithelium and vascular endothelium of control lungs, however, it was decreased in airway epithelial cells and arterial endothelial cells of patients with OB. CONCLUSIONS: We conclude that increased formation of the potent oxidant peroxynitrite and decreased production of endothelial nitric oxide may contribute to the functional and morphological abnormalities of OB.

Bronchiolitis Obliterans↗

PubMed1997

Prolonged ischemia is associated with more pronounced rejection in the lung allograft.

BACKGROUND: Previously it was found that ischemia-reperfusion injury in a left lung autotransplantation model could be a minor inducer of major histocompatibility complex (MHC) class II antigen expression. Thus, we hypothesized that prolonged ischemic times may result in increased expression of MHC class II antigens and predispose the lungs to the development of acute rejection early after transplantation. METHODS: Twenty conditioned dogs underwent single left lung allotransplantation. Donor lungs were subjected to 4 or 24 hours (n = 10 each) of cold ischemia. Open lung biopsies, bronchoalveolar lavage fluid, and blood samples were taken preoperatively and at various intervals up to 1 week after transplantation. Lung biopsy specimens were examined histologically for MHC class II expression and graded for acute rejection. Bronchoalveolar lavage fluid and plasma were analyzed for cytokines interleukin-2 and interferon-gamma. RESULTS: In the 4-hour ischemia group, there was mild diffuse staining of the bronchial epithelium and cellular infiltrate for MHC class II antigens after 1 week with subsequent grade 1-2 rejection. In the 24-hour ischemia group, MHC expression after 1 week revealed strong diffuse staining of bronchial epithelium, vascular endothelium, and cellular infiltrates with a significantly higher grade of rejection. Interleukin-2 and interferon-gamma significantly increased in BAL fluid early after transplantation in both groups. CONCLUSIONS: Ischemic injury may predispose the lung allograft to the development of acute rejection, in part, through the upregulation of MHC class II antigen expression and the local release of cytokines.

Acute Disease↗

PubMed1997

Safe and effective method of stabilization for coronary artery bypass grafting on the beating heart.

BACKGROUND: There is an emerging interest in performing coronary artery bypass grafting on the beating heart. This study examines the efficacy and safety of two types of coronary artery stabilizers developed to perform coronary artery bypass grafting on the beating heart. METHODS: Four dogs underwent left internal mammary artery to left anterior descending artery anastomosis using a retractor-fixed stabilizer. Measurements of hemodynamic indices and range of motion of the targeted arteriotomy were done before and after application of the stabilizers. Patency of the anastomosis was evaluated by angiography. To clinically validate the safety of this stabilizer, we collected data on 150 patients from centers that had access to the retractor-fixed stabilizer. RESULTS: All animals survived the procedure with no ischemic changes or hemodynamic alterations. A significant reduction in range of motion (mm) of the left anterior descending coronary artery was achieved after application of the stabilizers. Angiographic studies showed good anastomotic patency. Histologic examination showed no myocardial injury. Patient data revealed successful completion of the anastomosis, with conversion to sternotomy or cardiopulmonary bypass in 1 patient each. Intraoperative and postoperative myocardial infarctions occurred in 1 patient each, with one in-hospital death. CONCLUSIONS: Significant stabilization of targeted coronary arteries allowing the performance of safe and reliable anastomosis on a beating heart can be achieved using the stabilizer.

Adult↗

PubMed1997

Video-assisted thoracic surgery: has technology found its place?

BACKGROUND: Since the introduction of minimally invasive surgical techniques in thoracic surgery in 1990, video-assisted thoracic surgery (VATS) has become the approach for many thoracic operations. The role of VATS has slowly evolved but has not been clearly defined. To better understand the role of VATS, we undertook a survey of practicing thoracic surgeons. METHODS: A questionnaire was sent to members of the General Thoracic Surgery Club asking the role of VATS in their practice and their opinions regarding appropriate applications, advantages, and limitations of the approach. RESULTS: Two hundred of the 229 members (87.3%) responded to the questionnaire. In this largely academic (66.3%) group of thoracic surgeons, 72% of whom had more than 10 years experience in general thoracic surgery, VATS was the preferred approach (> 50% response) for the management of pleural disease, lung biopsy, recurrent pneumothorax, and sympathectomy. A majority of respondents thought that VATS was an acceptable approach for the diagnosis of the indeterminate pulmonary nodule and of anterior and posterior mediastinal masses, and for the management of early empyema, clotted hemothoraces, secondary pneumothorax, limited lung cancer treatment, and benign esophageal disease. Video-assisted thoracic surgery was thought to be unacceptable or investigational by a majority for thymectomy, lobectomy, and lung volume reduction operations. Video-assisted thoracic surgery still represents only a small portion of the thoracic procedures performed, but there is a gradual increase in its rate of use, although 38.1% expressed concern regarding overuse. The main limitation was thought to be in the management of oncologic disease. CONCLUSIONS: It appears that VATS is a valuable addition to the practice of thoracic surgery, but significant limitations exist. Although there appear to be many specific indications defined, there is still a significant evolutionary component.

Attitude of Health Personnel↗

PubMed1997

Catheter-assisted totally thoracoscopic coronary artery bypass grafting: a feasibility study.

BACKGROUND: The purpose of this study is to examine the feasibility of performing totally thoracoscopic internal mammary-to-coronary artery bypass grafting with the assistance of radiologically guided catheter intervention. METHODS: Fourteen dogs were subjected to mobilization of the internal mammary artery and anastomosis of it to the left anterior descending coronary artery over an angiographic catheter inserted into the internal mammary artery under fluoroscopy. The anastomosis was completed over the catheter using sutures and the application of fibrin glue. Eight animals underwent the anastomosis after their sacrifice. The other 6 animals were put on closed chest cardiopulmonary bypass and had their anastomosis done after intraaortic balloon occlusion and cardioplegic arrest of the heart. All animals had an angiographic and pathologic examination at the completion of the anastomosis. RESULTS: Anastomosis was completed in all dogs. Three anastomoses leaked and two were noted to be stenosed at completion of the anastomosis. One leak was sealed by application of fibrin glue. Both stenotic anastomoses were caused by suturing of the back wall when a short angiographic catheter could not be positioned across the anastomosis. CONCLUSIONS: Minimally invasive totally thoracoscopic mammary-to-coronary artery bypass grafting with catheter assistance is feasible. Technical improvement and appropriate instrumentation are required to minimize anastomotic failure.

Animals↗

PubMed1997

A survey on minimally invasive coronary artery bypass grafting.

BACKGROUND: There is increasing interest in performing minimally invasive coronary artery bypass grafting. To evaluate the current level of acceptance and utility of this procedure a survey of 162 cardiothoracic surgeons was conducted. RESULTS: Currently only 16% of surveyed surgeons performed more than 10 minimally invasive coronary artery bypass grafting procedures. Most were less than 55 years old and in private practice. The majority predicted that it will be indicated in less than 25% of coronary artery bypass grafting cases and considered minimally invasive coronary artery bypass grafting a modification of existing techniques rather than investigational. Most believed exposure and stabilization of the coronary arteries on the beating heart to be the most challenging part and expressed concern with quality of the anastomosis. CONCLUSIONS: We conclude that minimally invasive coronary artery bypass grafting is rapidly gaining acceptance in younger surgeons as techniques are improved. Despite concerns with adequacy of anastomosis the procedure is not considered investigational and follow-up is not rigorous.

Canada↗

PubMed1996

Altered nonspecific lymphocyte cytotoxicity in bronchoalveolar lavage of lung transplant recipients: can it be useful in monitoring rejection or infection?

A reliable method for determining the adequacy of immunosuppression of the lung allograft and the absence of rejection or infection does not exist. The purpose of this study is to evaluate the potential role of bronchoalveolar lavage (BAL) in monitoring the adequacy of immunosuppression of lung allografts and in identifying the possible presence of acute rejection (AR) or infection. Thirty-one consecutive lung transplant recipients were subjected to bronchoscopy, transbronchial biopsy, and BAL either as routine surveillance or for decline in lung function (n=68 episodes: 27 normal, 17 infections, six grade IAR, 10 grade II-III AR, and eight obliterative bronchiolitis). Diagnosis was always confirmed histologically and by microbiological workup. Harvested cells underwent phenotypic analysis, and T lymphocytes were subjected to nonspecific lectin-dependent cell-mediated cytotoxicity (LDCMC) and natural killer cytotoxic assays. BAL from normal grafts predominantly contained macrophages (72.8+/-4.4%), with lower neutrophil (13.9+/-4.1%) and lymphocyte (13.2+/-2.2%) populations. Grade II-III AR and infection were associated with an increase in the percentage of neutrophils (43.3+/-8.3% and 33.2+/-3.6%, respectively, P=0.02). BAL of normal allografts contained T cells with low LDCMC (7.4+/-4.5%) and natural killer cytotoxicity (6.3+/-3.4%), whereas grade II-III AR was associated with a significant elevation in LDCMC (32.5+/-11.6%, P=0.019). Pulmonary infection, regardless of its type, was associated with significant elevation in BAL natural killer cytotoxicity (23.9+/-4.9%, P=0.033). Patients with obliterative bronchiolitis, on the other hand, had a mild elevation in the percentage of neutrophils and lymphocytes in BAL, which did not reach statistical significance. However, BAL T-cell LDCMC was significantly elevated (37.6+/-13.7%, P=0.019) compared with normal and infected allografts. We conclude that phenotypic and nonspecific cytotoxic T-cell analysis of BAL, when complimented with microbiological studies, may be useful in surveillance of lung transplant recipients and in determining whether allografts are likely to be quiescent, or possibly affected by acute/chronic rejection or infection, necessitating further definitive action.

Bronchoalveolar Lavage↗

PubMed1996

Amelioration of pulmonary allograft injury by administering a second rinse solution.

OBJECTIVE: The use of rinse solutions before reperfusing liver allografts has been shown to reduce cell death in rats. Carolina rinse solution (an extracellular solution that contains antioxidants, vasodilators, and other substrates that help prevent ischemia-reperfusion injury) has also been shown to improve liver function clinically in liver transplant recipients. This pilot study evaluates the value of a second pulmonary artery flush before reperfusion of a lung graft. METHODS: Six groups of Sprague-Dawley rats (n = 6 each) were subjected to the following: Group 1 lungs were preserved with modified Euro-Collins solution followed by 24 hours of cold ischemia. Group 2 lungs were treated the same as group 1 but reperfused with blood. Group 3 lungs were preserved in Carolina rinse solution followed by 24 hours of cold ischemia. Group 4 lungs were treated the same as group 3 lungs and then reperfused with blood. Lungs in groups 5 and 6 were preserved with Euro-Collins solution, stored cold for 24 hours, and then rinsed with Euro-Collins or Carolina rinse solution, respectively, before reperfusion with blood. Lungs were subsequently stained with trypan blue solution for 5 minutes. Lung blocks were fixed and embedded in water-soluble methacrylate. Trypan blue--stained nuclei in nonviable endothelial cells and alveolar pneumocytes were counted in 10 different fields. RESULTS: Groups 1 and 3, preserved with Euro-Collins and Carolina rinse solutions for 24 hours but not reperfused with blood, had significantly more viable endothelial cells (groups 1 and 3 vs group 2, p < 0.0001; group 3 vs group 4, p < 0.02) and pneumocytes (group 1 vs groups 2 and 4, group 3 versus group 2, p < 0.0001; group 3 vs group 4; p < 0.035) than groups 2 and 4, which were subsequently reperfused with blood. Groups 5 and 6, which received a second rinse, also had significantly more viable endothelial cells (p < 0.0005) and pneumocytes (p < 0.0001) than control groups, which were not rinsed before reperfusion. CONCLUSIONS: We conclude that damage to pulmonary allografts resulting from prolonged ischemia is accentuated by reperfusion with blood. We also conclude that preservation with a single flush of Euro-Collins or Carolina rinse solution does not offer adequate protection, whereas a second rinse before reperfusion significantly decreases the number of damaged cells within the allograft.

Animals↗

PubMed1996

Expression of nitric oxide synthase in the human nasal mucosa.

The nasal mucosa plays an important role in defense of the lung against harmful agents. It has been suggested that this is partly mediated by the production of nitric oxide (NO). We have investigated the localization of the messenger ribonucleic acids (MRNAs) for human endothelial NO synthase (Type III NOS) and inducible NO synthase (Type II NOS) and the immunoreactivities of these enzymes in human nasal mucosa by immunohistochemistry, in situ hybridization, and reduced nicotinamide adenine diphosphate (NADPH) diaphorase histochemistry. Inferior nasal turbinates were obtained from 27 patients at the time of surgery for local disease. Strong immunostaining for Type III NOS was localized to vascular endothelium, surface epithelium, and submucosal glands in all subjects. Moderate immunostaining for Type II NOS was seen in surface epithelium; glandular, inflammatory, and vascular endothelial cells; and smooth-muscle cells in the specimens from patients with chronic rhinitis only. In situ hybridization showed expression of the mRNA for Type III NOS in similar sites to those shown by immunohistochemistry, whereas the mRNA for Type II NOS was predominantly localized to inflammatory cells. The sites of NOS expression were further confirmed by NADPH histochemical staining. These findings demonstrate the cellular expression of NOS in the human nasal mucosa and suggest a possible role for Types II and III NO synthase in the regulation of blood flow, nasal secretion, and ciliary movement in health and disease.

Adult↗

PubMed1996

Bronchoscopy in the intensive care unit.

With the prevalence of bronchopulmonary disease in the intensive care unit, bronchoscopy has become an essential tool for the management of patients. This article describes the variety of situations in which bronchoscopy can be of assistance in establishing diagnosis, managing the difficult airway, and supporting the patient's suffering of trauma, hemoptysis, atelectasis, and pneumonia.

Bronchoscopes↗