Tumor necrosis factor and septic shock

Is TNF-alpha a prognostic factor in patients with sepsis?

OBJECTIVE: To determine tumor necrosis factor-alpha (TNF-alpha) levels in a prospective study in 58 hospitalized patients in a department of internal medicine (63 episodes, 29 in immunocompromised patients) during a 7-month period. METHODS: Patients fulfilling the following criteria were included: clinical evidence of acute infection, temperature >38.2 degrees C, tachycardia >90 beats/min, tachypnea >20 breaths/min. Samples were taken from day 1 up to day 13 after an infection was diagnosed, and TNF-alpha was determined by enzyme immunoassay. RESULTS: In 29 episodes (46.0%) the infection was microbiologically documented. The median of the TNF-alpha levels in the Gram-negative episodes was significantly higher than that in the Gram-positive episodes (p=0.002). Thirteen of 63 episodes (20.6%) had a fatal outcome. With respect to all measured values, the non-survivors had a significantly higher median of TNF-alpha levels than the survivors (p=0.0001). There was, however, great interpatient and intrapatient variability in TNF-alpha levels; thus, no unequivocal correlation between TNF-alpha and outcome could be documented. CONCLUSIONS: Our data indicate that the influence of the infecting organism on TNF-alpha kinetics is less pronounced than that of the underlying disease.

High tumor necrosis factor serum level is associated with increased survival in patients with abdominal septic shock: a prospective study in 59 patients

BACKGROUND

In several studies including patients with septic shock of various origins, high serum cytokine levels have been reported to correlate with poor outcome. The aim of this prospective study was to assess the prognostic value of cytokine serum levels in a group of patients with perioperative septic shock of digestive origin.

METHODS

From January 1992 to December 1994, 59 patients were evaluated (mean age, 68 +/- 15 years). From the first day of septic shock to day 7, blood was drawn every day to measure the conventional biologic parameters (white blood cell count, platelet count, hematocrit, blood urea nitrogen level, serum electrolytes level, pH, blood gases, serum lactate level, coagulation parameters, liver function tests) and tumor necrosis factor (TNF), interleukin-1, and interleukin-6.

RESULTS

No difference was observed between the 26 survivors and the 33 nonsurvivors with regard to age, gender, and cause of sepsis. On admission, mean platelet count was significantly higher in the survivors than in the nonsurvivors (260 +/- 142 versus 177 +/- 122 10(9)/L; p = 0.01). Mean blood urea nitrogen level was significantly lower in the survivors than in the nonsurvivors (9.6 +/- 9 versus 12 +/- 7 mmol/L; p = 0.04). No difference was observed between survivors and nonsurvivors for the other conventional biologic parameters and for serum interleukin-1 and interleukin-6 levels. Mean serum TNF level tended to be higher in survivors than in nonsurvivors (565 +/- 1325 versus 94 +/- 69 pg/ml; not significant). In the group survivor 9 (35%) of 26 patients had a serum TNF level greater than 200 pg/ml versus 2 (6%) of 33 patients in the nonsurvivor group (p < 0.02). Survival was noted in 6 (100%) of 6 patients who had both a serum TNF level greater than 200 pg/ml and a platelet count greater than 100.10(9)/L versus 1 (11%) of 9 in patients with neither of these criteria (p < 0.01).

CONCLUSIONS

In our patients with abdominal septic shock, high serum TNF levels were associated with increased survival. The high serum level of TNF may reflect the efficacy of peritoneal inflammatory response against abdominal sepsis. Although this possibility must be further explored, a score combining the serum TNF level and platelet count could be helpful for the prognostic assessment of patients with abdominal septic shock.

Splanchnic ischaemia and its role in multiple organ failure

Multiple organ failure remains the leading cause of death in the intensive care unit. Increasing numbers of investigators have focused their attention on the role of gastrointestinal tract in the pathogenesis of this syndrome. Their data indicate that inadequate gut perfusion leads to a measurable imbalance between oxygen delivery and the needs of the tissues, i.e., ischaemia. Gut ischaemia of sufficient duration impairs gastrointestinal tract barrier function, facilitating the passage of enteric bacterial endotoxin into the circulation. It has been hypothesized that production of tumor necrosis factor alpha, and other biologic mediators by endotoxin-stimulated macrophages, triggers a generalized and uncontrolled inflammatory response that ultimately leads to multiple organ failure. Preliminary evidence suggests that survival can be improved significantly if gut ischaemia is promptly identified and aggressively treated by administration of fluids and inotropic drugs, using gastric intramucosal pH as the therapeutic endpoint. Future studies are needed to determine whether additional treatment modalities can improve outcome once the inflammatory response has fully developed.

Serum-induced potentiation of tumor necrosis factor alpha production by human monocytes in response to staphylococcal peptidoglycan: involvement of different serum factors

Peptidoglycan from a Staphylococcus epidermidis strain, isolated from a patient with septicemia, was preincubated with human serum. This mixture was then investigated for its potency to induce tumor necrosis factor (TNF) secretion by human blood monocytes. TNF was measured in the supernatants by using a bioassay and/or an enzyme-linked immunosorbent assay specific for TNF alpha (TNF-alpha). Although earlier studies indicated that staphylococcal peptidoglycan alone is a relatively poor stimulator of TNF-alpha production, the present study shows that human serum highly potentiates peptidoglycan-induced TNF-alpha release by human monocytes. In the presence of serum and in the low-dose range, peptidoglycan was almost as potent as endotoxin. At high peptidoglycan concentrations, monocytes showed an extremely high TNF-alpha response, but again only in the presence of serum. At low peptidoglycan doses, the stimulatory effect of serum was abrogated by heat treatment or depleting serum of complement components C1 and C3/C4, which suggests a role for the classical complement pathway. At high doses of peptidoglycan, the serum stimulatory effect depended mainly on immunoglobulin G.

In-vitro stimulation of TNF-alpha from human whole blood by cell-free supernatants of gram-positive bacteria

Gram-positive bacteria are being recognized increasingly as the cause of shock-like syndromes, clinically indistinguishable from those seen in association with Gram-negative endotoxic shock. Much clinical and experimental data link tumour necrosis factor-alpha (TNF-alpha) with the pathogenesis of endotoxic shock, and a number of studies of individual Gram-positive species have also implicated TNF-alpha. We report here the first systematic study of the ability of cell-free supernatants of common Gram-positive bacteria to induce TNF-alpha from human peripheral blood monocytes in vitro. Almost all the 63 strains were able to induce TNF-alpha, although the levels were substantially lower than those obtained from supernatants of Gram-negative bacteria, used as controls. Streptococcus pneumoniae, S. pyogenes, viridans streptococci and coagulase-negative staphylococci were consistently more active than group B and D streptococci. TNF-alpha induction did not correlate with conventional markers of pathogenicity; amongst strains of Staphylococcus aureus, commensal and blood culture isolates did not induce significantly different amounts of TNF. We conclude that cell-free supernatants of most Gram-positive bacteria are capable of inducing TNF-alpha from human peripheral blood monocytes in vitro, but the significance of this finding remains to be determined.

Different role of cytokine mediators in septic shock related to meningococcal disease and surgery/polytrauma

So far, there has been a tendency towards a uniform concept of the role and kinetics of TNF and other cytokines in septic shock. However, our comparison of data from different groups of shock patients clearly demonstrates marked differences. On the one hand, the cytokine pattern in experimental septic shock and meningococcal disease has similarities which include early burst releases of TNF and IL-6. On the other hand, intensive care unit patients which includes patients with polytrauma, surgery, burns and other underlying diseases have a completely different pattern of appearance of TNF and IL-6 in the circulation. We have not been able to detect bioactive TNF in the circulation of these patients, whereas others have measured elevated levels of immunoreactive TNF. Bioactive IL-6 can be detected in serum; however, the levels are often fluctuating and there is no common pattern of appearance. These differences probably reflect differences in the release of endotoxin and the immunological status of the patients. TNF inhibitors and soluble TNF receptors probably play an important role. Experimental models for septic shock most commonly use administration of live bacteria or endotoxin to anesthesized healthy animals. This appears to be a good model for meningococcal disease, but not for intensive care unit patients.

Administration of anti-TNF antibody improves left ventricular function in septic shock patients. Results of a pilot study

In this pilot study, murine monoclonal anti-TNF antibody (2 mg/kg) was administered to ten patients within 24 h of septic shock which persisted after initial resuscitation with intravenous fluids and adrenergic agents. This treatment resulted in a reduction in heart rate (from 122 +/- 10 to 113 +/- 10 beats per minute at 4 h, p less than 0.01) associated with an increase in LVSWI (from 26.5 +/- 5.6 to 31.5 +/- 10.5 g.m2 at 2 h, p less than 0.05), indicating in the absence of change in cardiac filling pressures, an improvement in ventricular function. Arterial oxygenation improved concurrently in six patients. These changes, however, appeared transient. The improvement in cardiac function following anti-TNF antibody administration in patients is in keeping with recent experimental studies indicating the role of TNF in the myocardial depression characterizing septic shock.