Study of septic shock in the non-human primate: relationship of pathophysiological response to therapy with anti-TNF antibody.

Therapy with anti-TNF antibody is reported to be effective in preventing morbidity and mortality in baboons given lethal infusions of Escherichia coli. Treated animals survived, and organ histopathology was absent when antibody was administered early after lethal infusions of E. coli. The present study explored the relationship between antibody dosage, pathophysiology, and survivability from shock. When antibody dose was decreased lungs, kidneys, adrenals, spleen, and liver were injured as shown by increased vascular congestion, hemorrhage, edema, and necrosis of tissues. Survival was also affected. All animals treated with 15 mg/kg antibody survived as reported earlier; less than 60% survived with 7.5 mg/kg; 9% survived with 5.0 mg/kg, and all died with 1.5 mg/kg. Serum concentrations of interleukin-6 (IL-6) increased markedly as dose of antibody decreased. The increases in concentrations of IL-6 were associated with increases in morbidity and mortality following E. coli administration.

Efficacy of monoclonal antibody against tumor necrosis factor alpha in an endotoxemic baboon model.

Tumor necrosis factor alpha (TNF) has been described as a primary mediator of the pathophysiology associated with bacterial sepsis/endotoxemia. We tested the efficacy and possible mechanisms of protection of a monoclonal antibody against TNF (TNF Mab) in a low mortality (29%), endotoxemic baboon model. A number of parameters were monitored at days 0, 1, 2 and 5-7 after challenge with 2 mg E. coli endotoxin/kg. TNF Mab pretreatment (15 mg/kg) prevented the increase in detectable serum TNF and the early perturbations in cardiovascular function which occurred in the control group. Early metabolic dysfunction was delayed in the TNF MAb group and was attenuated thereafter. Dysfunction of the kidney, liver, and coagulation systems and the increased IL-6 levels were significantly attenuated in the TNF MAb group; neutrophil activation was not affected by TNF MAb. No deaths occurred in the TNF MAb group. These results support the hypothesis that TNF plays a central role in the pathophysiology of endotoxic shock.

Lethal Staphylococcus aureus-induced shock in primates: prevention of death with anti-TNF antibody.

A successful experimental treatment for gram-positive sepsis to our knowledge has not been achieved. The objectives of this study were to develop a nonhuman primate model of lethal gram-positive sepsis employing the micro-organism Staphylococcus aureus and to determine the efficacy of treatment using monoclonal antibody (MAb) to tumor necrosis factor alpha (TNF). The antibody was administered intravenously, 15 mg/kg, 30 minutes after the beginning of a 2-hour infusion of S. aureus, 4 x 10(10) colony forming units/kilogram. The baboons infused with S. aureus demonstrated the release of the cytokines TNF and interleukin-6 (IL-6), but endotoxin was not observed in the plasma at any time. Treatment with antibody to TNF abolished the rise in serum TNF levels and reduced the increased levels of IL-6. Treatment with MAb to TNF prevented multiple organ failure and achieved permanent (> 7 day) survival of all baboons.

Characterization of an endotoxemic baboon model of metabolic and organ dysfunction.

An anesthetized endotoxemic baboon model has been developed by infusing 2.0 mg E. coli endotoxin/kg i.v. over 1 hr (n = 7). Animals were monitored for 5-7 days with analyses of: cardiovascular, metabolic, and organ dysfunction; acid base, hemostatic, and hematological alterations; as well as tumor necrosis factor (TNF) and interleukin-6 (IL-6) levels. Pathophysiologies detected at 2 hr included transient decreases in vascular resistance and blood pressure, a 157% increase in blood lactate, and a 90% decrease in circulating neutrophils. Organ dysfunction was not observed until 24 hr and, although thrombocytopenia was prevalent (-72% at 48 hr), disseminated intravascular coagulation (DIC) was not a major pathology. Hematocrit fell 21% by 24 hr and was -41% at 5-7 days. Serum TNF peaked at 90 min (7.8 +/- 0.2 ng/mL) and was undetectable after 3 hr. IL-6 also increased early, peaked at 3 hr (3872 +/- 846 U/mL) and was still detectable at 24 hr. A low mortality primate model of gram-negative sepsis has been developed that is characterized by early cardiovascular and metabolic dysfunction (2-6 hr), late organ dysfunction (24-48 hr), sub-clinical DIC, a prolonged anemia, and a 29% mortality between 48 and 72 hr.

Survival of primates in LD100 septic shock following therapy with antibody to tumor necrosis factor (TNF alpha).

The purpose of this study was to determine the efficacy of treatment with anti-TNF monoclonal antibody in preventing the deleterious effects of sepsis in a nonhuman primate. Experiments were carried out on anesthetized baboons intravenously infused with a lethal dose of Escherichia coli (E. coli). Twelve baboons (six control and six experimental) received 2 hr infusions of E. coli. The experimental group was administered a bolus of anti-TNF antibody, 15 mg/kg, 30 min after beginning the E. coli infusion. Control baboons lived an average of 19 hr (12-34 hr). All antibody-treated baboons survived more than 7 days with a significantly improved quality of life compared to the control group. Although some adverse changes occurred during the monitoring period in surviving baboons, they maintained nearly normal arterial pressures, and serum urea nitrogen and creatinine concentrations. The severe histopathologic changes in lungs, liver, adrenals, kidneys, and spleen documented at death in baboons receiving E. coli only were absent after 7 days in baboons given E. coli and early post-treatment with antibody to TNF.

Direct effects of insulin and endotoxin on glucose uptake by skeletal muscle during high cardiac index sepsis in the dog.

Experiments were completed upon unanesthetized and anesthetized dogs in the control and septic groups. Dogs that were made septic by the intraperitoneal administration of live Escherichia coli bacteria showed an elevation in cardiac index and core temperature and a decrease in total peripheral resistance index and mean arterial blood pressure. Following the seventh day of sepsis, the dogs were anesthetized and the constantly perfused gracilis muscle preparation was used for metabolic and hemodynamic determinations. Insulin stimulated muscle glucose uptake in non-septic dogs was markedly increased, whereas increases in muscle glucose uptake in the septic group of dogs was absent when challenged with local insulin infusion. Resting muscle glucose uptake of the septic group was observed to be greater than that of dogs in the nonseptic group. These data demonstrate a hyperdynamic model of sepsis in the dog which was associated with decreased muscle responsiveness or sensitivity to local insulin infusion, or both. The insulin-like activity of the endotoxin molecule in promoting muscle glucose uptake was maintained in both the septic and control group of dogs. This activity of the endotoxin molecule could explain, in part, the increased resting muscle glucose uptake observed in the septic group of dogs.

Skeletal muscle insulin resistance during Escherichia coli bacteremic shock in the dog.

Skeletal muscle glucose uptake during close, intra-arterial insulin infusion was studied before and during live Escherichia coli bacteremic shock in the dog. An in vivo, constant-flow perfused gracilis muscle preparation was used. Insulin infusion before shock resulted in a 395% increase in muscle glucose uptake, which was independent of changes in muscle lactate production or oxygen uptake. At 1, 2, and 3 hours of shock, insulin infusion had no effect on gracilis muscle glucose uptake. This loss of responsiveness to insulin occurred with no change in muscle oxygen uptake, muscle venous PO2, or muscle blood flow (held constant). On the other hand, during nonshock control experiments, muscle glucose uptake in response to insulin infusion was maintained during the 3-hour protocol. These data demonstrate that skeletal muscle insulin resistance develops early during bacteremic shock.

Involvement of adenosine in cerebral hypoxic hyperemia in the dog.

Theophylline, a competitive adenosine antagonist, was used to evaluate the role of adenosine in cerebral hypoxic hyperemia. Cerebral venous outflow was measured by the Rapela-Green technique in mongrel dogs anesthetized with pentobarbital sodium and ventilated artificially. Theophylline was infused locally into the cerebral arterial system during moderate [cerebral venous O2 tension (PO2) 27-29 mmHg] or severe (cerebral venous PO2 = 10-15 mmHg) hypoxia; theophylline had no direct vascular effects at the concentration used. Cerebral hyperemia was completely reversed during moderate hypoxia, but only partially reversed during severe hypoxia when theophylline was infused during maintained hypoxia. Theophylline had no effect on cerebral; perfusion pressure, blood flow, or vascular resistance during normoxia. In another group, theophylline had no effect on the cerebral hyperemia induced by hypercapnia. In separate experiments, local cerebral arterial infusion of adenosine or AMP during normoxia had no effect on cerebral hemodynamics at any infusion rate tested (up to 100 micrograms/min). This study supports the hypothesis that adenosine is involved in the hyperemia associated with cerebral hypoxia. However, the degree of involvement may be dependent on the degree of hypoxia.

Effects of naloxone therapy on hemodynamics and metabolism following a superlethal dosage of Escherichia coli endotoxin in dogs.

Experiments were done upon anesthetized and unanesthetized dogs given endotoxin only, endotoxin plus naloxone or naloxone only. Dogs given endotoxin and treated with naloxone showed marked hemodynamic and metabolic improvements compared with the dogs given endotoxin only. Beneficial effects of naloxone treatment following the administration of endotoxin are attentuated hypotension, hemoconcentration and acidosis and prevention of hypoglycemia. Results of mortality studies in unanesthetized dogs given endotoxin suggest that naloxone treatment increases the survival time.

Methylprednisolone in the prevention of cerebral hemodynamic and metabolic disorders during endotoxin shock in the dog.

These results provide evidence that steroid pretreatment and subsequent post-treatment prevent cerebral hemodynamic and metabolic alterations during four hours of Escherichia coli endotoxin shock in the dog. However, in this study, no data are provided on how the steroid prevents an increase in cerebral vascular resistance, and no clear answer is available in the literature. While active vasodilation or alpha-adrenergic blocking properties, or both, have been attributed to glucocorticoids, recent evidence does not support these findings during normal conditions or circulatory shock. If the increase in cerebral vascular resistance is passive, steroids may help by preventing platelet aggregation, cell disruption and subsequent microvascular plugging. Intravenously administered fluids, dextran-saline solution, while in themselves are probably not important to survival, may augment cerebral blood flow during shock through a blood dilutional effect. Finally, it is possible that steroids act to permit normal, long term cerebral auto-regulation, which is apparently impaired during endotoxin shock in the dog.