Search

Background: Previous in vitro studies have demonstrated that the host response to intra-abdominal infection produces increased generalized polymorphonuclear neutrophil (PMN) adherence to vascular endothelial cells (ECs), which may lead to subsequent endothelial damage, leaky capillaries, and organ dysfunction. There are scant data to demonstrate this enhanced systemic PMN adherence in vivo or the influence of PMN rolling on PMN endothelial adherence., Hypothesis: Systemic PMN adherence in the animal with sepsis is increased., Design: In vivo murine model of a 2-front infection using intravital microscopy of the cremasteric muscle to quantify PMN-EC adherence in a septic response., Setting: Basic science laboratory and animal surgical facility., Patients or Other Participants: One hundred CD1 male mice., Interventions: Animals underwent cecal ligation and puncture peritonitis, cremasteric muscle Escherichia coli infection, both infections, or neither (controls). Eighteen hours later, the mice underwent exteriorization of the cremasteric muscle under an intravital microscope for measurement of PMN-EC interactions. Blood was then drawn for calculation of circulating PMN counts., Main Outcome Measures: Adherence of PMNs, PMN rolling flux, PMN rolling velocity, and circulating PMN counts., Results: Circulatory mechanics did not differ between the groups. Unlike static in vitro systems, we could not detect an increase in PMN adherence after peritonitis with this dynamic in vivo model. A local (cremasteric) infection was associated with marked PMN adherence. Peritonitis was associated with reduced PMN adherence at a local infection site as well as reduced rolling adhesion and PMN rolling velocity., Conclusions: The data suggest that intra-abdominal infection does not increase remote PMN adherence, and may actually result in reduction of systemic adherence via modulation of PMN rolling.

Objective: To determine the effect of the inhibition of nitric oxide (NO) on selective organ blood flow in endotoxin-induced sepsis., Design: Nonrandomized, controlled experiment., Setting: Animal research facility in Brooklyn, NY., Participants: Eleven mongrel dogs., Intervention: Eleven dogs were divided into one of two groups: a control group (n = 5) and an endotoxin-treated group (n = 6). The animals were anesthetized, and electromagnetic and ultrasonic flow probes were placed on the distal aorta, right internal carotid artery, superior mesenteric artery, and left renal artery. Sepsis was induced with a 60-mg/kg intravenous injection of Escherichia coli endotoxin. When the arterial blood pressure decreased to less than 60 mm Hg despite adequate fluid resuscitation, NO synthesis was inhibited with a 25-mg/kg intravenous administration of NG-monomethyl-L-arginine. After 15 minutes of inhibition, a 400-mg/kg intravenous administration of L-arginine, the substrate of NO synthase enzyme, was given. Physiologic measurements were continued for 15 minutes thereafter., Main Outcome Measures: Heart rate, blood pressure, central venous pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, hematocrit, arterial and venous blood gas values, and blood flow measurements of right internal carotid artery, superior mesenteric artery, left renal artery, and distal aorta., Results: Control animals did not demonstrate a significant (P > .05) decrease in blood flow in the internal carotid artery, superior mesenteric artery, and distal aorta after the administration of NG-monomethyl-L-arginine. The endotoxin-treated group showed a significant (P < .05) decrease in organ perfusion when treated with the NO synthase inhibitor, NG-monomethyl-L-arginine., Conclusions: Inhibition of NO production in the treatment of sepsis caused a significant decrease in blood flow to all vascular beds in vivo. The role, if any, of the inhibition of NO in the treatment of sepsis is questioned.

We tested the hypothesis that long-term intravascular cannulation exacerbates the harmful effects of an infectious challenge. Four groups of rats were initially studied: rats without intravascular catheters or infection (group 1), rats without catheters with a polymicrobial infection (group 2), rats with catheters but no infection (group 3), and rats with catheters and infection (group 4). Infected animals had an increased mortality and generated a significantly increased tumor necrosis factor response compared with noninfected animals. Animals with catheters and infection generated far less cardiac output than animals from the other three groups. No histologic changes differentiated the four groups. Therefore, the presence of a sterile intravascular catheter significantly increases cardiac dysfunction and mortality rates in rats with chronic bacteremia. These results suggest that intravascular plastic catheters potentiate the destructive cascade of events produced by the host in response to bacteremia.

The effect of intraperitoneal bile on growth, peritoneal absorption, and clearance of Escherichia coli was determined in E coli peritonitis in the rat. In E coli peritonitis, intraperitoneal bacterial counts gradually decreased, whereas they increased (after 2 hours) with subsequent development of bacteremia in E coli plus bile peritonitis. After an intraperitoneal injection of labeled bacteria, blood radioactivity was only initially lower in E coli plus bile peritonitis compared with E coli peritonitis. Clearance from blood was lower in E coli plus bile peritonitis than in E coli peritonitis. Organ localization was similar in E coli peritonitis and E coli plus bile peritonitis with decreased splenic, increased pulmonary, and unchanged hepatic uptakes compared with controls. Impaired peritoneal absorption of bacteria, together with impaired local host defense, is likely to enhance the noxious effect of bile in E coli peritonitis.

Enteral nutritional support has been found to result in better maintenance of mucosal integrity during stress than parenterally administered nutritional support. In our experiments, we employed in vivo microvascular techniques to examine the effect of mucosally applied glucose on intestinal microvascular blood flow during hyperdynamic live Escherichia coli bacteremia in the rat. We observed a significant decrease in intestinal microvascular blood flow during bacteremia when the mucosa was suffused with a nonglucose solution. Blood flow was rapidly restored to above-baseline values after glucose was added. The restoration of blood flow resulted from dilation of arterioles at all branch orders and was associated with dilation of premucosal arterioles to above-baseline diameters. Our results show that glucose-induced absorptive hyperemia restores intestinal blood flow during live E coli bacteremia. Restoration of intestinal microvascular blood flow may be a contributing factor to the improved maintenance of mucosal integrity associated with enteral feeding.

In a common bile duct contamination model, we studied the effect of Streptococcus faecalis compared with Escherichia coli in sheep with chronic lymph fistulas to investigate the role of enterococcus in acute lung injury and acute sepsis. Early pulmonary hypertension in the E coli group was not expressed in the S faecalis group, probably due to a failure of S faecalis to illicit a thromboxane A2 response. In the late period, E coli was associated with significantly greater lung microvascular damage compared with S faecalis. The lack of difference between groups with respect to complement activation suggests the action of chemotactic factors, in addition to complement, mediating granulocyte aggregation, and neutropenia. In this model, S faecalis demonstrated limited pathogenicity as expressed in lung microvascular injury compared with E coli.

To determine the microvascular site of vasodilation during hyperdynamic sepsis, we measured arteriolar and venular responses to live Escherichia coli bacteremia in the rat cremaster muscle by direct in vivo videomicroscopy. Our data indicate that cardiac output (by thermodilution) increased, systemic vascular resistance decreased, and a differential arteriolar response occurred, with constriction of large arterioles and dilation of small terminal arterioles. We conclude that dilation of small terminal arterioles in skeletal muscle could contribute to decreased systemic vascular resistance during hyperdynamic sepsis. This may be an appropriate response to increased oxygen demand or decreased tissue utilization of oxygen. Alternatively, small-arteriole dilation may be an inappropriate response and secondary to release of vasoactive inflammatory mediators. If the latter is true, there is a potential therapeutic role for selective manipulation of the tone of small terminal arterioles in hyperdynamic sepsis.

Measurements of the resting membrane potential in skeletal muscle were used to monitor cell function in live Escherichia coli-induced sepsis and septic shock. Depolarization of the cell membrane, indicative of cell swelling, occurred before the onset of deep hypotension, suggesting cellular injury as a primary cause rather than a result of shock. The normal values for high-energy phosphates found in skeletal muscle in the terminal stages of shock reduce the possibility of an energy deficit as one of the factors in the cellular membrane malfunctions in septic shock.

We studied the effect of 2.5 X 10(9) live Escherichia coli per kilogram v 2.7 X 10(9) dead E coli per kilogram injected into the peritoneal cavity of sheep with chronic pulmonary lymph fistulas. The effects of dead E coli were compared with those of live E coli, with respect to (1) pulmonary hypertension, (2) hemodynamic failure, (3) damage to the pulmonary microvasculature, (4) systemic arterial hypoxemia, (5) neutropenia and lymphopenia, (6) thrombocytopenia and platelet aggregation, (7) plasma fibrinogen concentration, and (8) classic- and alternative-pathway hemolytic complement. The time after injection of the bacteria was divided into an early period (zero to two hours) and a late period (two to seven hours). We made two conclusions: (1) The early period effects, with the exception of the absolute neutrophil count and Pao2, were independent of bacterial viability, whereas the late period effects were strongly dependent on bacterial viability. (2) The early notable difference between the live v dead groups, with respect to the absolute neutrophil count and Pao2, could not be explained on the basis of an increase in bacterial numbers alone.

The response of the adrenal cortex to corticotropin during sepsis is variable. We have previously demonstrated a significant decrease of corticosterone production by rat adrenocortical cells in response to corticotropin stimulation after incubation with septic shock plasma (SP) as compared with control plasma (CP). We have studied the mechanisms of this depression. The following defects were demonstrated. (1) Cells bound less radioiodinated corticotropin analog after SP treatment (2.9 +/- 0.4 femtomoles/50 micrograms DNA) than after CP treatment (6.4 +/- 0.3 fmole/50 micrograms DNA). (2) Cyclic adenosine monophosphate (cAMP) production was less after SP treatment (59.3 +/- 4 pmole per 10(5) cells per two hours) compared with CP treatment (110.3 +/- 11.3 pmole per 10(5) cells per two hours). (3) Exogenously added dibutyryl cAMP was unable to correct the defect in corticosterone production after SP treatment (4.96 +/- 0.7 micrograms/24 hr) as compared with CP treatment (6.99 +/- 0.5 micrograms/24 hr). Our studies suggest this defect is located in the synthesis of pregnenolone from cholesterol. These mechanisms may be responsible for the low cortisol levels previously observed in humans during septic shock.

Previous studies from this laboratory described myocardial depression in an arterially perfused rabbit interventricular septum following perfusion with acute septic plasma. Calcium is critical for maintenance of cardiac contractility on a beat-to-beat basis. We have investigated calcium flux in the septal tissue to determine whether altered calcium flux explains the impaired cardiac function during sepsis. Twenty-two rabbit septa were perfused with control and septic perfusate (cryo-precipitated plasma + RBCs) and calcium flux determined in seven experiments. Perfusate cations (Ca++, Na+, K+, and H+) were measured, tissue function and arterial pressure were monitored. Developed tension decreased 46%, acceleration of tension change fell 42%, and arterial pressure decreased 26%, all highly significant. All septa recovered after return to control perfusate. The septic perfusate Ca++ was significantly lower than control perfusate, while K+ and H+ were significantly elevated. Ion flux studies, however, could not demonstrate altered calcium flux associated with the depressed contractility.

The beneficial effects of delayed closure of contaminated wounds are recognized, but not well defined. Rats with abdominal incisions were infected with Staphylococcus aureus or Escherichia coli and then subgrouped for primary or secondary healing. Noninfected rats served as controls. Between seven and 119 days later, the wounds were subjected to breaking-strength determination, hydroxyproline analysis, and light and scanning electron microscopy. In the controls, secondary closure gave stronger wounds than primary closure. In those infected with S aureus the wounds were stronger than in the primary-closure control group, regardless of the closure method. Of the E coli-infected wounds those primarily closed were weaker than those secondarily closed. Secondary closure gave infected wounds fewer complications. Biochemical and microscopic examination did not explain these findings.

Septic shock was induced by intravenous infusion of live Escherichia coli in pigs to investigate the influences on central hemodynamic, coagulation, and fibrinolytic reactions by a thromboxane A2 (TxA2)-receptor blocker (BM 13.177; n = 6) and a prostacyclin analogue (iloprost or ZK 36,374; n = 7). The early pulmonary vasoconstriction following E coli infusion was attenuated, but not abolished, by BM 13.177. Only minor effects were seen after pretreatment with iloprost. Neither drug had any major effect on the coagulation and fibrinolytic activation. These results confirm that TxA2 is an important, but not the only, mediator of early pulmonary vascular response in porcine septicemia and that neither TxA2 nor prostacyclin is of major importance for the hemostatic reactions in this shock model.

Intracellular metabolite glutathione, existing in either its reduced (GSH) or oxidized states, is crucial for the protection of any cell against an oxidative stress or injury. Significant depletion of intracellular levels of GSH predisposes cells to an oxidative injury. We have investigated the level of hepatic GSH during the early course of sepsis in a physiologically well-characterized septic-sheep model. Following six hours of sepsis, which was characterized by hypotension, hypoxemia, and granulocytopenia, the level of intrahepatic GSH was significantly reduced compared with baseline levels. There was no reduction after two hours of sepsis. Hepatic GSH levels in control animals were unchanged compared with baseline levels. These findings suggest that the liver may be more susceptible to an oxidative stress in septic patients.

Overwhelming sepsis associated with cardiac failure continues to be a major clinical problem. This is commonly associated with a failure to respond to conventional pharmacologic therapy. This study was undertaken to see if manipulations of the electrophysiologic defects previously described by treatment with tetraethylammonium chloride (TEA) would be advantageous. Septic shock was induced in rabbits by a lethal dose of Escherichia coli. Peak tension and velocities of contraction and relaxation were measured in papillary muscle with and without 5mM TEA. Exposure to this compound improved peak tension and velocities of contraction and relaxation to normal values. The action of TEA is not specific to septic tissue as values in normal muscles are similarly improved. Tetraethylammonium chloride or other drugs that decrease outward potassium current and prolong the action potential duration may be helpful in treating cardiac dysfunction that accompanies sepsis.

Low levels of plasma fibronectin (PFN), an adhesive glycoprotein postulated to augment reticuloendothelial function, can predispose animals to a poor clinical outcome following sepsis. In the present study, the PFN levels of adult male rats were measured prior to injection of intraperitoneal Escherichia coli and/or stroma-free hemoglobin (SFH) and subsequently at 4, 24, and 48 hours. Intraperitoneal E coli alone elicited insignificant PFN level depression at four hours, with significantly elevated levels only in the high-dose group at 24 (P less than .05) and 48 hours (P less than .01). Intraperitoneal SFH alone did not alter PFN levels from baseline values; when combined with E coli significant four-hour level depression is noted (P less than .05). Elevation of PFN levels by 24 hours occurs in a dose-dependent fashion, returning to baseline values 48 hours postinoculation. Significant mortality was observed only with high doses of E coli combined with SFH. The PFN levels are elevated 24 to 48 hours following high-dose E coli injection. Stroma-free hemoglobin alone has no effect, but when combined with E coli results in PFN level depression four hours postinoculation, contributing to impairment of systemic host defenses and possibly predisposing to greater mortality.