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R L Danner

Publications and source records attributed to R L Danner.

At least 37 records · Page 2Linked to original sources

Role of endotoxemia in cardiovascular dysfunction and lethality: virulent and nonvirulent Escherichia coli challenges in a canine model of septic shock.

We investigated whether the severity of septic shock is determined by virulence factors associated with or the levels of endotoxemia produced by two Escherichia coli strains. Canines were challenged intraperitoneally with an E. coli strain (O6:H1:K2) that has virulence factors associated with human disease or with an equal dose of a nonvirulent strain (O86:H8) that lacks these factors. Both strains were administered in viable, heat-killed, and purified endotoxin forms. Median survival times with the virulent strain compared with the nonvirulent strain were shorter with viable bacteria (5 x 10(10) CFU/kg) (144 h versus > 672 h; Wilcoxon, P = 0.03), longer with heat-killed bacteria (5 x 10(9) CFU/kg) ( > 676 h versus 26 h; P = 0.03), and similar with purified endotoxin (15 mg/kg) (28 h versus 48 h; P = 0.71). However, whether the challenge contained viable bacteria, heat-killed bacteria, or purified endotoxin, the virulent strain produced less endotoxemia (P = 0.001). Hence, the changing outcomes with differing forms of the two strains cannot be attributed solely to endotoxin levels. The viable virulent strain caused less endotoxemia but more harm, and this does not appear to be explained by a more potent endotoxin or other heat-stable component. This study suggests that circulating endotoxin levels per se are less important in the outcome of septic shock than virulence factors associated with E. coli strains. Furthermore, the data call into question the significance of the endotoxin concentration in the blood in predicting the severity of shock and the lethality of gram-negative infections.

Animals↗

Controlled trials of rG-CSF and CD11b-directed MAb during hyperoxia and E. coli pneumonia in rats.

We studied the effects of inhibiting and augmenting neutrophil function by using an immunocompetent rat model of infectious and hyperoxic lung injury. After intrabronchial Escherichia coli challenge at all fractional inspired O2 (FIO2) values studied (FIO2 = 0.21, 0.60, and 0.95) and after lethal O2 exposure alone (FIO2 = 0.90), lung injury, as measured by histological and physiological changes, was reduced by a CD11b/CD18-directed monoclonal antibody (MAb 1B6, P < 0.05 vs. controls) but was increased by recombinant granulocyte colony-stimulating factor (rG-CSF; P < 0.05 vs. control; MAb 1B6 vs. rG-CSF, P < 0.004). Pulmonary neutrophil counts were reduced by MAb 1B6 (P < 0.04) and increased by rG-CSF (P < 0.0004) compared with control animals. However, despite antibiotics, MAb 1B6 and rG-CSF both significantly increased the relative risk of death, independent of O2 concentration, during E. coli pneumonia (1.74 [symbol: see text] 1.20 and 2.39 [symbol: see text] 1.19, respectively, each P < 0.01). During lethal hyperoxia, MAb 1B6 increased the relative risk of death (1.76 [symbol: see text] 1.28, P < 0.16), whereas rG-CSF had no effect on survival (0.97 [symbol: see text] 1.28, P = 0.89). Thus inhibition of neutrophil function attenuated and enhancement worsened lung injury in response to infectious and hyperoxic challenges, supporting a pathophysiological role of the neutrophil in these processes. However, it is problematic that MAb 1B6 therapy, despite preventing lung damage, ultimately worsened host defenses and survival. Furthermore, rG-CSF also adversely affected survival during infectious lung injury, demonstrating the inherent risks of inhibiting or augmenting neutrophil function in an immunocompetent host during infection.

Animals↗

Serial measures of total body oxygen consumption in an awake canine model of septic shock.

We examined serial changes in total body oxygen consumption (Vo2) in a permanently tracheotomized canine sepsis model. On Day 0, beagles had an Escherichia coli-infected (septic) or sterile (control) clot surgically placed in the peritoneum. During the 21-d study, 10 of the 16 septic animals and none of the six control animals died (p = 0.02). After clot placement septic versus control animals had decreased mean arterial blood pressure (mm Hg; Day 1: 106 versus 128, p = 0.055; Day 2: 95 versus 125, p = 0.004, respectively) and left ventricular ejection fraction (Day 1: 0.44 versus 0.69, p = 0.0006; Day 2: 0.33 versus 0.57, p = 0.0001, respectively). Despite significant lethality and cardiovascular dysfunction, in the septic group on Days 1 and 2, septic versus control animals had no significant differences in mean metabolic cart measured (Vo2DIR, ml/kg/min; Day 1: 11.9 versus 12.4, p = 0.81; Day 2: 14.2 versus 13.5, p = 0.72, respectively) and intravascular catheter calculated (Vo2INDIR, ml/kg/min; Day 1: 11.2 versus 11.2, p = 0.99; Day 2: 12.8 versus 15.4, p = 0.49, respectively). On Day 1 in septic and control animals, volume infusion produced increases (p < 0.001) in oxygen delivery (Do2). In septic and control animals these changes in Do2 were similar and were associated with similar increases in Vo2DIR (p = 0.001), and Vo2INDIR (p = 0.001). In fact, at all time points studied (baseline, Day 1, 2, and 21), both before and after volume infusion, levels of Do2, Vo2DIR, and Vo2INDIR did not differ between septic and control animals, nor did they differ between septic survivors and nonsurvivors. Because levels of Vo2DIR and Vo2INDIR were similar in both groups, we pooled data from septic and control animals. Throughout the study, Vo2 showed a moderate association with Vo2INDIR (r = 0.55, p = 0.003), but mean Vo2DIR was lower at baseline (p = 0.001) and on Day 21 (p = 0.07) and greater on Day 2 (p < 0.01). In summary, our techniques, which detected small changes in both Vo2DIR and Vo2INDIR occurring with volume infusion, did not demonstrate differences in these parameters comparing control and septic animals. These results in euvolemic septic animals suggest that total body Vo2 may not reflect pathogenetic mechanisms during sepsis and septic shock. Furthermore, these results suggest that although the level of total body Vo2 may reflect the effects of therapeutic interventions such as volume loading, it should not itself serve as a therapeutic target.

Animals↗

Hemodynamic effects of dopamine, norepinephrine, and fluids in a dog model of sepsis.

To study how sepsis affects hemodynamic responses to catecholamines and fluids, either Escherichia coli-infected (septic, n = 8) or sterile (controls, n = 6) fibrin clots were implanted intraperitoneally into 2-yr-old beagles. Hemodynamics were measured at each of four doses of dopamine (0, 5, 10, and 20 micrograms.kg-1.min-1) and norepinephrine (0, 10, 20, and 40 micrograms.min-1), before and after infusion of fluid (Ringer 40 ml.kg-1). Septic animals had lower mean arterial pressure (MAP, P = 0.04), stroke volume index (SVI, P = 0.0001), and left ventricular (LV) ejection fraction (LVEF) (P = 0.0001) than controls. During this time, increasing doses of dopamine and norepinephrine produced corresponding increases (P < 0.001) in LVEF, SVI, and MAP. However, during sepsis, the ability of dopamine to increase MAP diminished, while its ability to increase LVEF and SVI was maintained. Conversely, the ability of norepinephrine to increase LVEF and SVI diminished, but its ability to increase MAP was maintained. During sepsis, fluids alone increased (P < 0.05) MAP, LVEF, SVI, and cardiac index (CI). Fluids with catecholamines also significantly increased (P < 0.05) MAP with only minimal increases in LVEF, SVI, and CI. These data demonstrate that during sepsis without catecholamines, fluids improve cardiac performance and systemic pressures, but with catecholamines, fluids have minimal effects on cardiac performance and augment MAP. Furthermore, during sepsis dopamine is more effective than norepinephrine in increasing LV performance, but norepinephrine is more effective than dopamine in increasing systemic pressures.

Animals↗

Therapeutic trial of reconstituted human high-density lipoprotein in a canine model of gram-negative septic shock.

In a controlled, randomized trial, the authors investigated the effects of reconstituted human high-density lipoprotein (R-HDL) on survival, endotoxemia, cytokine production and pathophysiologic and metabolic events in an animal model of gram-negative septic shock. At 0.5, 8 and 16 hr after implantation of a clot infected with Escherichia coli, canines received intravenous R-HDL (n = 13), control lipid (n = 7) or human serum albumin (HSA, n = 7) divided into three doses (0.3, 0.1 and 0.1 g/kg, respectively) at an hourly rate of 0.1 g/kg. All animals were treated with antibiotics and fluids. Animals treated with R-HDL had lower levels of circulating endotoxin and tumor necrosis factor and a smaller decrease in white blood cell counts than did animals treated with lipids and HSA (all P < .05). The survival times of lipid- and HSA-treated animals were similar (P = .3) and were significantly greater than those of R-HDL-treated animals (P = .02). During the first 6 hr after clot implantation, R-HDL-treated animals had significantly greater abnormalities in liver function test findings compared with lipid- and HSA-treated animals (all P < .05). For the first 24 hr, R-HDL-treated animals had significant increases in HDL levels; however, there were no significant relationships between these levels and the constituents of HDL (apolipoprotein AI and phosphatidylcholine) or liver function abnormalities and survival times (all r < .2, P > .3). In normal animals, administration of R-HDL (in similar doses) caused transient elevation of liver enzymes; in animals given sterile clot i.p., R-HDL caused seizures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Continuous arteriovenous hemofiltration does not improve survival in a canine model of septic shock.

BACKGROUND: We examined whether or not continuous arteriovenous hemofiltration (CAVH), in the absence of renal failure, would improve either hemodynamic abnormalities or survival in a canine model of septic shock. STUDY DESIGN: Escherichia coli 0111, as an intraperitoneal clot, was surgically implanted into 21 one- to two-year-old purpose-bred beagles. The dogs were randomized to no CAVH (control group, n = 7), sham CAVH (extracorporeal circulation without hemofiltration, n = 7), or true CAVH (hemofiltration with removal of 600 mL/hour of ultrafiltrate, n = 7). Hemofiltration began one hour after clot implantation and continued for six hours. All dogs received antibiotics and had serial hemodynamic and laboratory evaluations. RESULTS: During the first seven hours of the study, all dogs displayed a progressive, significant decrease in mean arterial pressure, cardiac index, left ventricular ejection fraction, and serum pH (all p < 0.05). Two of seven dogs in the control group, one of seven dogs in the sham CAVH group, and one of seven dogs in the true CAVH group survived seven days after clot implantation. True CAVH, which included fluid replacement with lactated Ringer's solution, significantly increased serum lactate and decreased serum bicarbonate levels after six hours (both p < 0.05). However, pH did not differ between the three treatment groups (p > 0.20). Continuous arteriovenous hemofiltration therapy had no significant effect on cardiovascular abnormalities or survival. CONCLUSIONS: The results of this study suggest that CAVH would be unlikely to provide benefit to patients with gram-negative septic shock, in the absence of renal failure.

Animals↗

Human polymorphonuclear leukocytes lack detectable nitric oxide synthase activity.

Nitric oxide regulates polymorphonuclear leukocyte (PMN) function, but whether or not human PMNs express nitric oxide synthase (NOS) activity is controversial. We studied NOS activity in human PMNs by using human aortic endothelial cells (HAECs) for comparison. The conversion of L-arginine to L-citrulline, a relatively specific measure of NOS activity, was easily measured and inducible in fractionated HAECs, and > 90% of all L-arginine conversion was blocked by the NOS inhibitor, N omega-amino-L-arginine (L-NAA). In fractionated PMNs, L-arginine conversion was low and was unaffected by L-NAA. In addition, NOS activity was not induced in PMNs by LPS, IL-1 beta, or IFN-gamma. In a whole-cell assay, total L-arginine conversion was much lower in human PMNs compared with HAECs (3.38 +/- 0.21 vs 157.5 +/- 10.28 pmol/h/10(6) cells, respectively; p < 0.01). This conversion in whole PMNs was not increased in vitro by LPS, IFN-gamma, IL-1 beta, or TNF-alpha nor decreased by W13, a calmodulin inhibitor. Furthermore, PMNs isolated from four volunteers before and after challenge with i.v. LPS (4 ng/kg) showed no increase in L-arginine to L-citrulline conversion. Nitrite and nitrate release from human PMNs was 35-fold lower than for HAECs and was not inhibited by L-NAA. These data suggest that human PMNs do not express NOS activity.

Amino Acid Oxidoreductases↗

Selected treatment strategies for septic shock based on proposed mechanisms of pathogenesis.

PURPOSE: To review selected new therapies for septic shock designed to inhibit bacterial toxins or endogenous mediators of inflammation. DATA SOURCES: Scientific journals, scientific meeting proceedings, and Food and Drug Administration advisory committee proceedings. STUDY SELECTION AND EXTRACTION: Preclinical and clinical data from trials using core-directed antiendotoxin antibodies and anticytokine therapies for sepsis and studies in animal models of sepsis from our laboratory. RESULTS OF DATA SYNTHESIS: Ten clinical trials using core-directed antiendotoxin antibodies produced inconsistent results and did not conclusively establish the safety or benefit of this approach. Both anti-interleukin-1 and anti-tumor necrosis factor (TNF) therapies have been beneficial in some animal models of sepsis but did not clearly improve survival in initial human trials, and one anti-TNF therapy actually produced harm. Neutrophils, another target for therapeutic intervention, protect the host from infection but may also contribute to the development of tissue injury during sepsis. In a canine model of septic shock, granulocyte colony-stimulating factor increased the number of circulating neutrophils and improved survival, but an anti-integrin (CD11/18) antibody that inhibits neutrophil function worsened outcome. Nitric oxide, a vasodilator produced by the host, causes hypotension during septic shock but may also protect the endothelium and maintain organ blood flow. In dogs challenged with endotoxin, the inhibition of nitric oxide production decreased cardiac index and did not improve survival. CONCLUSIONS: No new therapy for sepsis has shown clinical efficacy. Perhaps more accurate clinical and laboratory predictors are needed to identify patients who may benefit from a given treatment strategy. On the other hand, the therapeutic premises may be flawed. Targeting a single microbial toxin such as endotoxin may not represent a viable strategy for treating a complex inflammatory response to diverse gram-negative bacteria. Similarly, the strategy of inhibiting the host inflammatory response may not be beneficial because immune cells and cytokines play both pathogenic and protective roles. Finally, our scientific knowledge of the complex timing of mediator release and balance during sepsis may be insufficient to develop successful therapeutic interventions for this syndrome.

Animals↗

Nitric oxide regulates endotoxin-induced TNF-alpha production by human neutrophils.

We studied the effect of nitric oxide on LPS-induced TNF-alpha production by human neutrophils. Human neutrophils exposed to LPS and IFN-gamma did not show measurable increases in intracellular cyclic GMP (cGMP). However, cGMP increased upto 30-fold (p < 0.01) in neutrophils incubated with both sodium nitroprusside (SNP), an exogenous source of nitric oxide, and N-acetylcysteine (NAC), which increases the bioavailability of nitric oxide; this increase indicates that neutrophils contain a nitric oxide-sensitive guanylate cyclase. SNP, with or without NAC, did not increase TNF-alpha production in human neutrophils cultured in medium alone. However, LPS-dependent TNF-alpha production was increased by exposure to SNP (p < 0.05); this effect was further increased by the addition of NAC (p < 0.02). IFN-gamma greatly increased LPS-mediated TNF-alpha production by human neutrophils (p < 0.01), and SNP plus NAC was found to further augment this production (p < 0.01). The up-regulation of TNF-alpha production by nitric oxide was not associated with increased amounts of LPS-induced TNF-alpha mRNA, and was not reproduced by exposing neutrophils to cGMP analogues. These data suggest that nitric oxide released by endothelial and vascular smooth muscle cells may exert a paracrine effect on human neutrophils and augment the inflammatory response in sepsis by increasing the production of cytokines. Although the mechanism of this effect remains unknown, it does not seem to be dependent on cGMP or increased levels of TNF-alpha mRNA.

Acetylcysteine↗

Diagnosis of pulmonary microvascular metastases by cytologic evaluation of pulmonary artery catheter-derived blood specimens.

Pulmonary microvascular tumor embolization is a recognized cause of respiratory distress in cancer patients that is rarely diagnosed antemortem. Previous studies with relatively few patients have reported high diagnostic yield using wedged pulmonary artery catheter-derived blood samples to evaluate dyspneic cancer patients for possible microembolization. From 1991 to 1993, 21 cancer patients with respiratory distress of relatively acute onset and varying severity who required pulmonary artery catheterization for hemodynamic monitoring were evaluated using this technique. Pulmonary microvascular cytology (PMC) was interpreted as positive for malignant cells in nine of 21 patients presenting with a range of tumor types, including carcinomas of the breast, colon, and pancreas as well as non-Hodgkin's lymphoma. In 11 patients the PMC was interpreted as negative. One case was considered nondiagnostic. Megakaryocytes, noted in most PMC specimens as well as in several samples of simultaneously drawn peripheral blood, may mimic epithelial tumor cells. Immunocytochemical stains for factor VIII and cytokeratins were used to resolve occasional diagnostic dilemmas. Clinical and/or pathologic follow-up information was available for all patients. Diagnostic accuracy was highest for epithelial malignancies. Two false-negative results occurred in patients with metastatic choriocarcinoma and breast carcinoma. Circulating malignant cells in the peripheral blood of a patient with non-Hodgkin's lymphoma led to one false-positive diagnosis. Benign lymphoid elements in PMC generally have a reactive and variable appearance that should not be misinterpreted as lymphoma. We conclude that PMC is a useful tool in the evaluation of dyspneic cancer patients requiring pulmonary artery catheterization for hemodynamic monitoring and its use potentially avoids additional diagnostic procedures.

Catheterization, Peripheral↗

Distinct functional activities in canine septic shock of monoclonal antibodies specific for the O polysaccharide and core regions of Escherichia coli lipopolysaccharide.

Monoclonal antibodies (MAbs) specific for O polysaccharide or core oligosaccharide/lipid A of Escherichia coli O111:B4 lipopolysaccharide (LPS) were compared in canine septic shock. Animals received O-specific, core-specific, or control murine IgG2a MAbs (or saline) before intraperitoneal implantation of an E. coli O111:B4-infected clot. Animals were further randomized to ceftriaxone or saline. O-specific MAb significantly reduced bacteremia and endotoxemia but not serum tumor necrosis factor. Core-specific MAb significantly increased mean arterial pressure from day 4 to 28 (P = .02). In dogs not receiving ceftriaxone, survival was enhanced by O-specific MAb (4/5) compared with core-specific MAb (0/5) and control (1/8) (P = .03). Survival rates were similar (P = .22) but survival was prolonged in antibiotic-treated animals also receiving O-specific MAb (P = .02 vs. core-specific MAb and controls) or core-specific MAb (P = .08 vs. controls). These data support the complex role of LPS in sepsis and the discrete functional effects of MAbs specific for different elements of LPS.

Animals↗

Neutrophil attractant protein-1 and monocyte chemoattractant protein-1 in human serum. Effects of intravenous lipopolysaccharide on free attractants, specific IgG autoantibodies and immune complexes.

We recently found that normal human sera contain IgG antibodies against two chemoattractants, neutrophil attractant protein-1 (NAP-1/IL-8) and monocyte chemoattractant protein-1 (MCP-1), as well as immune complexes of these proteins. Intravenously administered LPS was reported to cause a sharp rise in serum NAP-1 concentration. Our study was designed to determine if LPS also caused an increase in MCP-1 and to measure associated changes in concentrations of antibody and immune complex. LPS caused a rise to peak within 2 to 3 h in serum concentrations of free NAP-1 and MCP-1, followed by an almost equally rapid fall toward base-line levels by about 5 h postinjection. MCP-1 concentration in sera from the 11 subjects rose to a peak of 330 +/- 52 pM. The peak value for NAP-1 was 80 +/- 11 pM. In 10 of the 11 subjects, free IgG autoantibody to MCP-1 decreased from a mean pre-LPS value of 1820 +/- 660 pM to a mean low of 53% of the respective initial values. Corresponding data for IgG anti-NAP-1 were a pre-LPS concentration of 216 +/- 7 pM, which decreased to a mean low of 44% of the respective initial values. The finding in some subjects of a rapid rise in free antibody after the nadir suggests the possibility of acute regulation of autoantibody secretion rates. Although the results suggested that LPS-induced chemoattractant combined with free antibody, serum concentrations of MCP-1-IgG or NAP-1-IgG did not increase, which points to an as yet unknown mechanism for trapping and elimination of the immune complexes.

Adult↗

A controlled trial of HA-1A in a canine model of gram-negative septic shock.

OBJECTIVE: To investigate the therapeutic efficacy and microbiological and physiological effects of a human IgM monoclonal antibody (HA-1A) directed against the lipid A component of endotoxin in a canine model of sepsis that simulates the cardiovascular abnormalities of human septic shock. DESIGN: Blinded, placebo-controlled 28-day trial. INTERVENTIONS: Purpose-bred beagles were implanted with an intraperitoneal clot infected with Escherichia coli O111:B4. At clot placement, animals received HA-1A (10 mg.kg-1), control human IgM antibody (10 mg.kg-1), or control human serum albumin intravenously. All animals were given antibiotic and fluid therapy. MEASURES: Survival and microbiological and physiological events. RESULTS: Only two (15%) of 13 animals in the HA-1A group, compared with eight (57%) of 14 control animals (combined control human IgM antibody and control human serum albumin groups) (P = .05), survived 28 days. At 24 hours, the HA-1A group had lower mean arterial pressure (P = .04) and cardiac index (P = .004) and higher lactate levels (P = .05) compared with the combined-controls group. In addition, these parameters in the HA-1A group were significantly more predictive of death. The HA-1A and combined-controls groups had similar significant increases in the level of endotoxemia and bacteremia. Studies of toxic effects showed no harmful effects of control human IgM antibody in infected animals or HA-1A in non-infected animals. CONCLUSION: In a canine model of E coli sepsis, HA-1A did not alter levels of bacteremia or endotoxemia and actually decreased survival. If these data are relevant to human septic shock, HA-1A therapy should be limited until the conditions under which this monoclonal antibody has beneficial or deleterious effects are more completely defined.

Animals↗

Plasma exchange does not improve survival in a canine model of human septic shock.

Whether plasma exchange would improve survival in antibiotic-treated canines with septic shock was investigated. Escherichia coli O86H8 (1.4 X 10(10)) was surgically implanted as an intraperitoneal clot in 18 two-year-old (10-12 kg) purpose-bred beagles. Beginning 4 hours after surgery, all animals received cefoxitin and gentamicin for 5 days. Three treatment groups were defined: 1) a no apheresis, or control group, (n = 6); 2) a sham apheresis group, whose whole blood plasma was removed, separated, and then transfused (n = 6); and 3) a plasma exchange group from whom blood and plasma were removed and separated, to whom the blood was returned, and in whom infected plasma was replaced with compatible fresh-frozen canine plasma (n = 6). For the sham apheresis and plasma exchange groups, a commercial blood cell processor was used to separate 1.5 blood volumes of plasma at 5 and 24 hours after surgery. Serial radionuclide left ventricular ejection fractions and femoral and pulmonary arterial catheter hemodynamics were measured simultaneously in awake animals. All six animals in the plasma exchange group died. In both the sham and control groups, only one of six animals survived. Survival times were ordered (median in hours) (control [372 h] > sham apheresis [48 h] > plasma exchange [24 h] [p < 0.038]). Decreases in mean cardiac index and mean arterial pressure (from before apheresis to after) at 5 to 7 hours after surgery were ordered (plasma exchange > sham apheresis > control; p < 0.03). Thus, plasma exchange in this controlled trial of septic shock was associated with decreased survival and worsened hemodynamics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Therapeutic trial of lipid X in a canine model of septic shock.

Three groups of dogs were given lipid X (0, 1, or 10 mg/kg) every 8 h for for seven doses, starting simultaneously with the intraperitoneal placement of Escherichia coli-containing fibrin clots. All animals developed bacteremia, hypotension, and a pattern of decreased left ventricular ejection fraction characteristic of septic shock (P = .01). Survival rates and survival times were not significantly different between treatment groups (P > .2). In a similar experiment, higher doses of lipid X resulted in a significantly decreased survival time compared with concurrent controls (P = .04). Animals receiving lipid X did not differ from controls in serial determinations of temperature, hemodynamic measurements, or laboratory parameters (except serum total protein). Although lipid X has antiendotoxin effects, no benefit could be demonstrated in this antibiotic-treated, gram-negative bacillary-infected model of septic shock. These data do not support a therapeutic role for lipid X in the treatment of gram-negative sepsis.

Animals↗