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Biomedical subjects

T G Buchman

Publications and source records attributed to T G Buchman.

At least 37 records · Page 2Linked to original sources
PubMed2000

Comparison of intravenous/oral ciprofloxacin plus metronidazole versus piperacillin/tazobactam in the treatment of complicated intraabdominal infections.

OBJECTIVE: To compare the safety and efficacy of intravenous (IV) ciprofloxacin plus IV metronidazole (CIP+MET) with that of IV piperacillin/tazobactam (PIP/TAZO) in adults with complicated intraabdominal infections, and to compare the efficacy of sequential IV-to-oral CIP+MET therapy with that of the IV CIP-only regimen. SUMMARY BACKGROUND DATA: Treatment of intraabdominal infections remains a challenge, mainly because of their polymicrobial etiology and attendant death and complications. Antimicrobial regimens using sequential IV-to-oral therapy may reduce the length of hospital stay. METHODS: In this multicenter, randomized, double-blind trial involving 459 patients, clinically improved IV-treated patients were switched to oral therapy after 48 hours. Overall clinical response was the primary efficacy measurement. RESULTS: A total of 282 patients (151 CIP+MET, 131 PIP/TAZO) were valid for efficacy. Of these patients, 64% CIP+MET and 57% PIP/TAZO patients were considered candidates for oral therapy. Patients had a mean APACHE II score of 9.6. The most common diagnoses were appendicitis (33%), other intraabdominal infection (29%), and abscess (25%). Overall clinical resolution rates were statistically superior for CIP+MET (74%) compared with PIP/TAZO (63%). Corresponding rates in the subgroup suitable for oral therapy were 85% for CIP+MET and 70% for PIP/TAZO. Postsurgical wound infection rates were significantly lower in CIP+MET (11%) versus PIP/TAZO patients (19%). Mean length of stay was 14 days for CIP+MET and 17 days for PIP/TAZO patients. CONCLUSION: CIP+MET, initially administered IV and followed by CIP+MET oral therapy, was clinically more effective than IV PIP/TAZO for the treatment of patients with complicated intraabdominal infections.

Abdomen↗
PubMed2000

Role of CuZn superoxide dismutase in regulating lymphocyte apoptosis during sepsis.

OBJECTIVE: The lymphocyte is a principal mediator of the inflammatory response, and lymphocyte depletion via apoptosis may be an important mechanism of modulating inflammation. Increased oxygen consumption occurs during sepsis and results in the generation of reactive oxygen species. Although reactive oxygen species initiate apoptosis in many biological systems, their role in controlling lymphocyte apoptosis during sepsis is unclear. The objective of this study was to better characterize the role of oxidative stress in precipitating lymphocyte apoptosis during sepsis and to specifically define the role of the CuZn superoxide dismutase (SOD) enzyme complex, a major antioxidant defense, in modulating this process. DESIGN: Prospective, randomized, controlled study. SETTING: Research laboratory at an academic medical center. SUBJECTS: Mice that were either genetically normal or that were deficient in or overexpressed the enzyme CuZn SOD. INTERVENTIONS: Mice from each genetic group were randomized to no manipulation (control), sham surgery, or cecal ligation and puncture. Mice were killed 18-24 hrs after study entry, and the thymi and spleen were removed for analysis of apoptosis. MEASUREMENTS AND MAIN RESULTS: Lymphocyte apoptosis was assessed by three independent methods: light microscopy, fluorescent terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling, and DNA gel electrophoresis. Comparisons were performed using standard parametric statistical tests. Lymphocyte apoptosis was present in mice after CLP but not in control mice or in mice after sham surgery (p < .05). Mice completely lacking CuZn SOD developed significantly more lymphocyte apoptosis than did either partially CuZn SOD-deficient or genetically normal mice (p < .05). This apoptosis was more pronounced in the thymus than the spleen and, within the thymus, more prominent in the cortex than medulla (p < .05 for all). In contrast, mice that overexpressed CuZn SOD did not differ in the amount of apoptosis after CLP compared with genetically normal mice (p = NS for all). CONCLUSIONS: Oxidative stress occurs in sepsis and appears to be one stimulus for the development of lymphocyte apoptosis, a process that is partly regulated by CuZn SOD. However, we were unable to demonstrate that overexpression of this enzyme suppressed lymphocyte apoptosis, suggesting that either other antioxidant defenses or other pathways independent of oxidative stress may mediate lymphocyte elimination in this syndrome.

Animals↗
PubMed2000

Rapid onset of intestinal epithelial and lymphocyte apoptotic cell death in patients with trauma and shock.

OBJECTIVE: Apoptosis is a cellular suicide program that can be activated by cell injury or stress. Although a number of laboratory studies have shown that ischemia/reperfusion injury can induce apoptosis, few clinical studies have been performed. The purpose of this study was to determine whether apoptosis is a major mechanism of cell death in intestinal epithelial cells and lymphocytes in patients who sustained trauma, shock, and ischemia/ reperfusion injury. DESIGN: Intestinal tissues were obtained intraoperatively from 10 patients with acute traumatic injuries as a result of motor vehicle collisions or gun shot wounds. A control population consisted of six patients who underwent elective bowel resections. Apoptosis was evaluated by conventional light microscopy, laser scanning confocal microscopy using the nuclear staining dye Hoechst 33342, immunohistochemical staining for active caspase-3, and immunohistochemical staining for cytokeratin 18. SETTING: Academic medical center. PATIENTS: Patients with trauma or elective bowel resections. MEASUREMENTS AND MAIN RESULTS: Extensive focal crypt epithelial and lymphocyte apoptosis were demonstrated by multiple methods of examination in the majority of trauma patients. Trauma patients having the highest injury severity score tended to have the most severe apoptosis. Repeat intestinal samples obtained from two of the trauma patients who had a high degree of apoptosis on initial evaluation were negative for apoptosis at the time of the second operation. Tissue lymphocyte apoptosis was associated with a markedly decreased circulating lymphocyte count in 9 of 10 trauma patients. CONCLUSIONS: Focal apoptosis of intestinal epithelial and lymphoid tissues occurs extremely rapidly after injury. Apoptotic loss of intestinal epithelial cells may compromise bowel wall integrity and be a mechanism for bacterial or endotoxin translocation into the systemic circulation. Apoptosis of lymphocytes may impair immunologic defenses and predispose to infection.

Adolescent↗
PubMed2000

Shock at the millennium. I. Walter B. Cannon and Alfred Blalock.

Present management of shock derives, in part, from the classic investigations of Walter B. Cannon and Alfred Blalock. The intersections of their professional lives as recorded in the professional literature and in personal correspondence suggest that Blalock's pivotal studies of experimental shock were fueled, at least in part, by Cannon's inability to resolve the inconsistencies of the then-popular toxic theory of shock. Cannon appears to have substantially shaped Blalock's thought and work, initially as authority and competitor and later as colleague and friend. Blalock's experimental proof that injury precipitated obligatory locoregional fluid losses, the effects of which could be ameliorated by vigorous restoration of plasma volume, became a cornerstone of shock theory and therapy.

Animals↗
PubMed2000

Caspases -2, -3, -6, and -9, but not caspase-1, are activated in sepsis-induced thymocyte apoptosis.

Sepsis induces extensive lymphocyte cell death that may contribute to immune depression and morbidity/mortality in the disorder. bcl-2 is a member of a new class of oncogenes that prevents cell death from an array of noxious stimuli. Transgenic mice that overexpress BCL-2 in T lymphocytes are resistant to sepsis-induced T cell apoptosis, and mortality was decreased in sepsis. The purpose of this study was to identify key initiator and executioner "caspases" involved in sepsis-induced lymphocyte apoptosis and to determine if BCL-2 acts prior to caspase activation. Thymi were removed 5-22 h post-cecal ligation and puncture (CLP) or sham surgery. Apoptosis was evaluated in thymocytes by annexin-V FITC labeling and flow cytometry. Caspase-1 activity was determined by western blot analysis of the procaspase protein and p20 subunit of the activated caspase; activities of caspases -2, -6, and -9 were determined by colorimetric assays using specific substrates conjugated to a color reporter molecule. Caspase-3 activity was determined both by western blot and by a fluorogenic assay in which a fluorescent compound was generated. Thymocytes from CLP mice had markedly increased apoptosis and activation of caspases -2, -3, -6, and -9 in comparison with thymocytes of sham-operated mice. Caspase-1 was not activated. BCL-2 prevented sepsis-induced thymocyte apoptosis and inhibited activation of all caspases. We conclude that sepsis causes activation of multiple caspases and that BCL-2 acts upstream as an inhibitor of caspase activation. The pattern of caspase activation suggests a mitochondrial mediated pathway.

Animals↗
PubMed2000

Injection of iron compounds followed by induction of the stress response causes tissue injury and apoptosis.

To determine whether iron-laden tissue subsequently stimulated to produce the stress ("heat shock") response-sustained injury, hindlimbs of male ND4 mice were injected with iron salts, hemin, or hemoglobin. The stress response was induced with sodium arsenite or with heat. Ulcers appeared at the injection site. Tissues were analyzed by three distinct techniques-electron microscopy, TUNEL stain, and agarose gel electrophoresis of low molecular weight DNA-which collectively suggest that the tissue injury is, at least in part, the consequence of accelerated apoptosis. The data suggest that the toxicity of free iron is amplified by induction of the stress (heat shock) response to signal a programmed response. This model and mechanism may have implications in pathological processes ranging from the cutaneous wounds of venous stasis disease to the tissue failure of multiple organ dysfunction.

Animals↗
PubMed2000

A meta-analysis of prospective trials comparing percutaneous and surgical tracheostomy in critically ill patients.

STUDY OBJECTIVES: Tracheostomy is one of the most commonly performed procedures in the patient receiving long-term mechanical ventilation. While percutaneous dilational tracheostomy (PDT) is becoming increasingly utilized as an alternative to conventional surgical tracheostomy, most literature evaluating these two techniques is neither prospective nor controlled. We performed a meta-analysis of available prospective controlled studies comparing PDT and surgical tracheostomy in critically ill patients to more fully understand the relative benefits and risks of these two procedures in this population. DESIGN: Meta-analysis using Mantel-Haenszel fixed effect model. INTERVENTIONS: We performed searches of MEDLINE, Current Contents, Best Evidence, Cochrane, and HealthSTAR databases from 1985 to present to identify prospective controlled studies comparing PDT and surgical tracheostomy in critically ill patients. After establishing clinical and statistical homogeneity (Q: statistic), studies were analyzed by a Mantel-Haenszel fixed effect model. For each clinical end point examined, PDT and surgical tracheostomy were compared by calculating either absolute differences or odds ratios (ORs) with 95% confidence intervals (CIs) for continuous or discrete variables, respectively. MEASUREMENTS AND RESULTS: We pooled data from five studies (236 patients) satisfying our search criteria to analyze eight clinical end points. Operative time was shorter for PDT than surgical tracheostomy: absolute difference with 95% CI, 9. 84 min (7.83 to 10.85 min). There was no difference comparing PDT and surgical tracheostomy with respect to overall operative complication rates: OR with 95% CI, 0.732 (0.05 to 9.37). However, relative to surgical tracheostomy, PDT was associated with less perioperative bleeding (OR with 95% CI, 0.14 [0.02 to 0.39]), a lower overall postoperative complication rate (OR with 95% CI, 0.14 [0.07 to 0.29]), as well as a lower postoperative incidence of bleeding (OR with 95% CI, 0.39 [0.17 to 0.88]), and stomal infection (OR with 95% CI, 0.02 [0.01 to 0.07]). No difference was identified in days intubated prior to tracheostomy (absolute difference with 95% CI, 0.16 days [- 0.9 to 1.22 days]), overall procedure-related complications (OR with 95% CI, 0.73 [0.06 to 9.37]), or death (OR with 95% CI, 0.63 [0.18 to 2.20]) comparing these two techniques. CONCLUSIONS: Despite its popularity, there are currently only a limited number of small studies prospectively evaluating PDT and surgical tracheostomy. Our meta-analysis of these studies suggests potential advantages of PDT relative to surgical tracheostomy, including ease of performance, and lower incidence of peristomal bleeding and postoperative infection. If confirmed by additional, adequately powered prospective trials, these findings support PDT as the procedure of choice for the establishment of elective tracheostomy in the appropriately selected critically ill patient.

Blood Loss, Surgical↗
PubMed1999

Prevention of lymphocyte cell death in sepsis improves survival in mice.

Sepsis induces extensive lymphocyte apoptosis, a process which may be beneficial to host survival by down-regulating the inflammatory response or, alternatively, harmful by impairing host defenses. To determine the beneficial vs. adverse effects of lymphocyte apoptosis in sepsis, we blocked lymphocyte apoptosis either by N-benzyloxycarbonyl-Val-Ala-Asp(O-methyl) fluoromethyl ketone (z-VAD), a broad-spectrum caspase inhibitor, or by use of Bcl-2 Ig transgenic mice that selectively overexpress the antiapoptotic protein Bcl-2 in a lymphoid pattern. Both z-VAD and Bcl-2 prevented lymphocyte apoptosis and resulted in a marked improvement in survival. z-VAD did not decrease lymphocyte tumor necrosis factor-alpha production. Considered together, these two studies employing different methods of blocking lymphocyte apoptosis provide compelling evidence that immunodepression resulting from the loss of lymphocytes is a central pathogenic event in sepsis, and they challenge the current paradigm that regards sepsis as a disorder resulting from an uncontrolled inflammatory response. Caspase inhibitors may represent a treatment strategy in this highly lethal disorder.

Animals↗
PubMed1999

Overexpression of Bcl-2 in transgenic mice decreases apoptosis and improves survival in sepsis.

In sepsis there is extensive apoptosis of lymphocytes, which may be beneficial by down-regulating the accompanying inflammation. Alternatively, apoptosis may be detrimental by impairing host defense. We studied whether Bcl-2, a potent antiapoptotic protein, could prevent lymphocyte apoptosis in a clinically relevant model of sepsis. Transgenic mice in which Bcl-2 was overexpressed in T cells had complete protection against sepsis-induced T lymphocyte apoptosis in thymus and spleen. Surprisingly, there was also a decrease in splenic B cell apoptosis in septic Bcl-2 overexpressors compared with septic HeJ and HeOuJ mice. There were marked increases in TNF-alpha, IL-1beta, and IL-10 in thymic tissue in sepsis in the three species of mice, and the increase in TNF-alpha and IL-10 in HeOuJ mice was greater than that in Bcl-2 mice. Mitotracker, a mitochondrial membrane potential indicator, demonstrated a sepsis-induced loss of membrane potential in T cells in HeJ and HeOuJ mice but not in Bcl-2 mice. Importantly, Bcl-2 overexpressors also had improved survival in sepsis. To investigate the potential impact of loss of lymphocytes on survival in sepsis, Rag-1-/- mice, which are totally deficient in mature T and B cells, were also studied. Rag-1-/- mice had decreased survival compared with immunologically normal mice with sepsis. We conclude that overexpression of Bcl-2 provides protection against cell death in sepsis. Lymphocyte death may be detrimental in sepsis by compromising host defense.

Animals↗
PubMed1999

Apoptotic cell death in patients with sepsis, shock, and multiple organ dysfunction.

OBJECTIVES: The purpose of this study was to determine whether apoptosis is a major mechanism of cell death in patients with sepsis. The activities of caspase-3 and the antiapoptotic protein, BCL-2, were investigated also. DESIGN: A prospective study of 20 patients who died of sepsis and multiple organ dysfunction was performed. The control group of 16 patients consisted of critically ill, nonseptic patients who were evaluated either prospectively (7) or retrospectively (9). In addition, normal colon sections from seven patients who had bowel resections were included. Apoptosis was evaluated in hematoxylin and eosin-stained specimens by deoxyuridine triphosphate nick end-labeling (TUNEL) and by DNA gel electrophoresis. SETTING: Two academic medical centers. PATIENTS: Critically ill patients. MEASUREMENTS AND MAIN RESULTS: In septic patients, apoptosis was detected in diverse organs by all three methods with a predominance in lymphocytes and intestinal epithelial cells. Hematoxylin and eosin-stained specimens from septic patients demonstrated at least focal apoptosis in 56.3% of spleens, 47.1% of colons, and 27.7% of ileums. Indirect evidence of lymphocyte apoptosis in septic patients included extensive depletion of lymphocytes in white pulp and a marked lymphocytopenia in 15 of 19 patients. Hematoxylin and eosin from nonseptic patients' tissues revealed a low level of apoptosis in one patient only. The TUNEL method increased in positivity with a delay in tissue fixation and was highly positive in many tissues from both septic and nonseptic patients. Immunohistochemical staining for active caspase-3 showed a marked increase in septic vs. nonseptic patients (p < .01), with >25% to 50% of cells being positive focally in the splenic white pulp of six septic but in no nonseptic patients. CONCLUSIONS: We conclude that caspase-3-mediated apoptosis causes extensive lymphocyte apoptosis in sepsis and may contribute to the impaired immune response that characterizes the disorder.

Adult↗
PubMed1999

The abdominal compartment syndrome: CT findings.

OBJECTIVE: The abdominal compartment syndrome is a potentially fatal condition resulting from pathologic elevation of intraabdominal pressure. We evaluated preoperative abdominal CT scans of four patients with proven abdominal compartment syndrome to identify signs of increased intraabdominal pressure. CONCLUSION: CT findings common to all four patients included tense infiltration of the retroperitoneum out of proportion to peritoneal disease, extrinsic compression of the inferior vena cava by retroperitoneal hemorrhage or exudate, and massive abdominal distention with an increased ratio of anteroposterior-to-transverse abdominal diameter (positive round belly sign; ratio > .80; p < .001). Direct renal compression or displacement, bowel wall thickening with enhancement, and bilateral inguinal herniation were each present in two of the four patients. Radiologists should be aware of this life-threatening syndrome. In the appropriate clinical setting, CT findings of increased intraabdominal pressure should be swiftly communicated to other physicians involved in treating the patient because the abdominal compartment syndrome requires emergent surgical decompression.

Abdomen↗
PubMed1999

Inducible nitric oxide synthase (iNOS) gene deficiency increases the mortality of sepsis in mice.

BACKGROUND: Nitric oxide (NO) produced by the inducible isoform of NO synthase (iNOS or NOS2) has been implicated in the hypotension, organ failure, and death that complicate sepsis. To avoid the confounding effects and limitations of iNOS inhibitors, we used iNOS gene "knockout" mice to examine the effect of inducible NO production in a model of polymicrobial abdominal sepsis treated with antibiotics. We hypothesized that iNOS gene deficiency would significantly alter outcome. METHODS: C57BL6 wild-type (control) and congenic iNOS knockout mice were studied concurrently. Under halothane anesthesia, the ceca were ligated with 4-0 silk suture and punctured twice with a 26-gauge needle (cecal ligation and puncture, CLP). Survival was followed for 7 days, after which necropsies were performed in surviving animals. In an accompanying study examining the acute effects of sepsis, organ injury at 18 hours after CLP as determined by histology and the degree of cell death by apoptosis were examined with the use of hematoxylin and eosin (H&E) and TUNEL staining and two-channel fluorescence-activated cell sorter (FACS) analysis. RESULTS: Sham laparotomy produced no lethality in either knockout (n = 3) or wild-type (n = 3) animals. Compared with survival in controls (n = 20), survival after CLP in iNOS knockout mice (n = 21) was significantly decreased (P < .01 at 2 days, P = .080 at 7 days, Mantel-Haenszel log-rank test). CLP-induced apoptotic cell death was significantly less in the thymus of iNOS knockout mice compared with wild-type mice. CONCLUSIONS: We conclude that iNOS gene function provides a survival benefit in septic mice and is associated with increased sepsis-induced thymocyte apoptosis. To our knowledge, this is the first survival study examining the effect of iNOS gene deficiency in a clinically relevant model of sepsis.

Animals↗
PubMed1998

Nitric oxide inhibits stress-induced endothelial cell apoptosis.

OBJECTIVES: To determine a mechanism by which nitric oxide alters induction of stress-induced endothelial cell apoptosis in vitro. Apoptosis is a form of cellular suicide that has been implicated in the pathogenesis of multiple organ dysfunction syndrome. DESIGN: Prospective, controlled trial. SETTING: Research laboratory of a large, academic medical center. SUBJECTS: Cultured primary porcine aortic endothelial cells. INTERVENTIONS: Cells were treated with a range of doses of agents that either spontaneously generate nitric oxide (S-nitroso-N-acetyl-D,L-penicillamine [SNAP] or (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1- ium-1,2-diolate [DETA-NO]) or block nitric oxide production (Nomega-methyl-L-arginine [L-NMA]). The ability of these agents to alter the rate of cell death by apoptosis (induced by the sequence stimuli lipopolysaccharide [LPS] followed by sodium arsenite) was measured. Mechanistic studies included examining the ability of: a) nitric oxide "donors" to alter nuclear factor kappa B (NF-kappaB) DNA binding activity and the level of IkappaBalpha accumulation; and b) a stable cyclic guanosine monophosphate (cGMP) analog (8-bromo-cGMP) to mimic the effect of nitric oxide donors. MEASUREMENTS AND MAIN RESULTS: The sequence LPS/sodium arsenite increased the rate of endothelial cell apoptosis (47.4%, p< .05 vs. control), as measured by fluorescent-activated cell scanning using annexin V/propidium iodide staining. DETA-NO generated nitric oxide (as indicated by an increase in the concentration of the stable end-products of nitric oxide metabolism) and decreased the rate of endothelial cell apoptosis (20.6% at a dose of 2 mM, p=.0001 vs. control). DETA-NO also decreased NF-kappaB DNA binding activity and the apparent accumulation of its endogenous inhibitor, IkappaBalpha. The 8-bromo-cGMP did not mimic the effects of nitric oxide donors (DETA-NO) on apoptosis. CONCLUSIONS: These data suggest that exogenous nitric oxide can block stress-induced endothelial cell apoptosis in vitro. The mechanistic studies are consistent with our hypothesis that inhibitors of NF-kappaB DNA binding activity are associated with protection against apoptosis-inducing stimuli. The results do not support a role for cGMP in mediating the protective effect of DETA-NO in our model.

Animals↗