Strategies for blocking the systemic effects of cytokines in the sepsis syndrome

Increased interleukin-8 concentrations in the pulmonary edema fluid of patients with acute respiratory distress syndrome from sepsis

OBJECTIVE

To test the hypothesis that significantly higher concentrations of interleukin-8 (IL-8) are found in the pulmonary edema fluid and plasma of patients with a septic vs. a nonseptic etiology of acute respiratory distress syndrome (ARDS).

DESIGN

Prospective measurement of IL-8 concentrations in previously collected edema fluid and plasma.

SETTING

Adult intensive care units at a university medical center.

PATIENTS

There were 27 patients with ARDS (16 patients with a septic etiology and nine patients with a nonseptic etiology) plus eight control patients with hydrostatic pulmonary edema.

MEASUREMENTS AND MAIN RESULTS

IL-8 was present in the pulmonary edema fluid of all patients with ARDS, but the median IL-8 concentration was higher in the edema fluid of patients with ARDS associated with sepsis (84.2 ng/mL, n = 16) compared with the ARDS patients without sepsis (14.8 ng/mL, n = 11) (p < .05). In patients with cardiogenic edema, IL-8 concentration (5.0 ng/mL,n = 8, p < .05) was significantly lower than those values in patients with ARDS. Median plasma concentration of IL-8 was increased in septic individuals (1.3 ng/mL), but these concentrations were not significantly higher than in patients with a nonseptic etiology of ARDS (0.35 ng/mL) (p = .14) or those patients with cardiac failure (0.21 ng/mL).

CONCLUSIONS

The high concentrations of IL-8 in pulmonary edema fluid, coupled with the relatively low concentrations of IL-8 in the plasma, suggest that the lung was the primary source of IL-8 in the patients with ARDS. The markedly increased concentrations of IL-8 in the pulmonary edema fluid of patients with ARDS from sepsis suggests that this group of patients may be particularly suitable for potential trials directed at inhibiting the activity of this important chemokine.

Induction of early-phase endotoxin tolerance in horses

Six, clinically healthy horses, of mixed age and sex, were infused via a jugular venous catheter with 100 ml of pyrogenfree sterile saline (PFSS; 0.9% NaCl). Animals were infused with Escherichia coli O55:B5 endotoxin (total dose = 50 ng/kg bwt), 24 (LPS-1) and 48 h (LPS-2) after PFSS infusion. Blood was collected before, and every 15 min after, each infusion for the first 8 h and then every 2 h for the following 14 h. Clinical responses (rectal temperature, heart rate, respiration rate and blood pressure) were determined before and every 4 h after each infusion for 20 h. Geometric mean anti-endotoxin antibody titres in serum samples, harvested just before each infusion, were unchanged over the course of the experiment. Serum tumour necrosis factor-alpha (TNF alpha) activity was estimated using a cytotoxic bioassay and WEHI 164 clone 13 murine fibrosarcoma cells as targets. Mean clinical parameter values and geometric mean serum TNF alpha activity at given time points were compared across the 3 infusions. Both LPS-1 and LPS-2 resulted in elevated mean rectal temperature at 4 h after infusion. However, duration of mean rectal temperature elevation was greater (P < 0.05) after LPS-1 (through 12 h) than after LPS-2 (through 8 h). More substantial increases in systolic and diastolic blood pressure were observed after LPS-1 than LPS-2 and mean systolic blood pressure after LPS-1 was elevated at 4 h when compared to PFSS (P < 0.05). Decreased systolic and diastolic blood pressures were observed at 16 h after both LPS infusions, when compared to PFSS infusion. Heart rate was increased, compared to PFSS, after both LPS-1 (8-12 h) and LPS-2 (4-12 h) (P < 0.05). No significant elevations in mean respiratory rate were observed after either LPS-1 or LPS-2 when compared to PFSS. However, at 4 h post infusion, mean respiratory rate after LPS-2 was greater (P < 0.05) than that after LPS-1. Serum TNF alpha activity was not detected after infusion of PFSS, but was detected after both LPS-1 and LPS-2. Serum TNF alpha activity was elevated earlier, was present in higher concentrations and persisted longer after LPS-1 than after LPS-2 (P < 0.05). The decreased duration of fever and attenuated serum TNF alpha response subsequent to successive sublethal LPS challenge observed in this study support the conclusion that these horses developed early-phase endotoxin tolerance (EPET) and, therefore, contributes to the understanding of the role of endotoxaemia in a number of clinical conditions in horses.

Hypothesis: compartmentalization of cytokines in intraabdominal infection

BACKGROUND

Although the proximal role of systemic cytokines in the infectious-inflammatory cascades is well recognized, the magnitude and meaning of its intraperitoneal levels in peritonitis have received little attention. We hypothesized that in peritonitis a significant and clinically relevant cytokine-mediated inflammatory response is compartmentalized in the peritoneal cavity.

METHODS

MEDLINE was used to search the literature for all articles dealing with experimental, primary, and secondary bacterial peritonitis and cytokines.

RESULTS

Bacterial peritonitis is associated with an immense intraperitoneally compartmentalized cytokine response, with plasma levels of cytokines representing only the tip of the iceberg. Although certain amount of cytokines may be beneficial to the peritoneal defense mechanisms, higher levels correlate with adverse outcome. Thus it is plausible to look at acute peritonitis as initially a combined infective (microorganism) and inflammatory (cytokines) process. The clinical significance of the distinction between peritoneal inflammation and infection and the relevance of our findings to the stratification and treatment of peritonitis are discussed.

CONCLUSIONS

Current surgical and antibiotic therapy for peritonitis is able to clear the peritoneal cavity of infective concentration of bacteria, but many patients continue to die of an uncontrolled activation of the inflammatory cascade. We suggest that one potential venue for therapeutic progress is the modulation of the compartmentalized peritoneal inflammatory response.

New perspectives on the management of septic shock in the cancer patient

Septic shock is a common life-threatening problem, usually presenting with fever, tachycardia, tachypnea, and often a source of infection. The cardiac index is increased, with a decreased systemic vascular resistance, and a reversibly decreased ejection fraction with an increased end diastolic volume. The myocardial depression is most likely caused by a circulating humoral substance that depresses myocardial contractility. The initial treatment of septic shock is aggressive fluid resuscitation and antibiotic therapy, with vasopressors and inotropes being indicated in those patients who do not respond adequately to fluids. Therapy directed against the mediators of septic shock is theoretically promising, but to date has not been successful.