Aminoethyl-isothiourea inhibits the increase in plasma endothelin-1 caused by serogroup A streptococci and prolongs survival in rat peritoneal sepsis

The effects of dobutamine on microcirculatory alterations in patients with septic shock are independent of its systemic effects*

OBJECTIVE

To evaluate the effects of dobutamine on microcirculatory blood flow alterations in patients with septic shock.

DESIGN

Prospective, open-label study.

SETTING

A 31-bed, medico-surgical intensive care unit of a university hospital.

PATIENTS

Twenty-two patients with septic shock.

INTERVENTIONS

Intravenous administration of dobutamine (5 mug/kg.min) for 2 hrs (n = 22) followed by the addition of 10 M acetylcholine (topically applied, n = 10).

MEASUREMENTS AND MAIN RESULTS

Complete hemodynamic measurements were obtained before and after dobutamine administration. In addition, the sublingual microcirculation was investigated with an orthogonal polarization spectral imaging technique before and after dobutamine administration and after topical application of acetylcholine. Dobutamine significantly improved capillary perfusion (from 48 +/- 15 to 67 +/- 11%, p = .001), but with large individual variation, whereas capillary density remained stable. The addition of topical acetylcholine completely restored capillary perfusion (98 +/- 1%, p = .001) and capillary density. The changes in capillary perfusion during dobutamine administration were not related to changes in cardiac index (p = .45) or arterial pressure (p = .29). Interestingly, the decrease in lactate levels was proportional to the improvement in capillary perfusion (y = 0.07 - 0.02x, r = .46, p = .005) but not to changes in cardiac index (p = .55).

CONCLUSIONS

The administration of 5 mug/kg.min dobutamine can improve but not restore capillary perfusion in patients with septic shock. These changes are independent of changes in systemic hemodynamic variables.

Selective inducible nitric oxide synthase inhibition attenuates organ dysfunction and elevated endothelin levels in LPS-induced DIC model rats

We examined the role of nitric oxide (NO) produced by an inducible isoform of NO synthase (iNOS) using N[6]-(iminoethyl)-lysine (L-NIL), a selective iNOS inhibitor, in the rat model of lipopolysaccharide (LPS)-induced disseminated intravascular coagulation (DIC) and investigated changes in organ function, plasma levels of NOX (metabolites of NO) and endothelin. We induced experimental DIC by the sustained infusion of 30 mg kg(-1) LPS for 4 h via the tail vein. We then investigated the effect of L-NIL (6 mg kg(-1), from - 0.5 to 4 h) on LPS-induced DIC. Blood was withdrawn at 4 and 8 h, and all four groups (LPS with or without L-NIL at 4 and 8 h) consisted of eight rats. Three of the animals in the 8-h LPS group died, and we examined blood samples from five rats in this group. None of the other rats died. The LPS-induced elevation of creatinine, alanine aminotransferase, glomerular fibrin deposition and plasminogen activator inhibitor was significantly suppressed by L-NIL coadministration, although L-NIL did not affect the platelet count, fibrinogen concentration or the level of thrombin-antithrombin complex. Moreover, plasma levels of the D-dimer that reflect the lysis of cross-linked fibrin were significantly increased by L-NIL coadministration in the LPS-induced DIC model. Plasma levels of NOX and endothelin were obviously increased by LPS infusion. However, both levels were significantly suppressed in the LPS + L-NIL group, when compared with the LPS group. Although mean arterial pressure (MAP) was significantly decreased between 2 and 8 h compared with the control in the LPS group, this depression was significantly attenuated in the LPS + L-NIL group. Our results suggest that NO induced by iNOS contributes to hypotension (depressed MAP), the progression of hepatic and renal dysfunction, microthrombus deposition and elevated endothelin levels in the rat model of LPS-induced DIC.

Sepsis: an arginine deficiency state?

OBJECTIVE

Sepsis is a major health problem considering its significant morbidity and mortality rate. The amino acid L-arginine has recently received substantial attention in relation to human sepsis. However, knowledge of arginine metabolism during sepsis is limited. Therefore, we reviewed the current knowledge about arginine metabolism in sepsis.

DATA SOURCE

This review summarizes the literature on arginine metabolism both in general and in relation to sepsis. Moreover, arginine-related therapies are reviewed and discussed, which includes therapies of both nitric oxide (NO) and arginine administration and therapies directed toward inhibition of NO.

DATA

In sepsis, protein breakdown is increased, which is a key process to maintain arginine delivery, because both endogenous de novo production from citrulline and food intake are reduced. Arginine catabolism, on the other hand, is markedly increased by enhanced use of arginine in the arginase and NO pathways. As a result, lowered plasma arginine levels are usually found. Clinical symptoms of sepsis that are related to changes in arginine metabolism are mainly related to hemodynamic alterations and diminished microcirculation. NO administration and arginine supplementation as a monotherapy demonstrated beneficial effects, whereas nonselective NO synthase inhibition seemed not to be beneficial, and selective NO synthase 2 inhibition was not beneficial overall.

CONCLUSIONS

Because sepsis has all the characteristics of an arginine-deficiency state, we hypothesise that arginine supplementation is a logical option in the treatment of sepsis. This is supported by substantial experimental and clinical data on NO donors and NO inhibitors. However, further evidence is required to prove our hypothesis.

Inhibition of nitric oxide synthase exacerbates group B streptococcus sepsis and arthritis in mice

The role of nitric oxide in group B Streptococcus (GBS) infection was evaluated by inhibiting its production with aminoguanidine (AG). AG-treated mice displayed higher mortality rates and more frequent and severe arthritis than controls. Worsening of arthritis correlated with a higher number of GBS cells in the joints and local interleukin-1 beta production.

Application of a rat model of streptococcal shock to evaluate on-line hemoperfusion and removal of circulating superantigens

OBJECTIVE

To evaluate the efficacy of on-line hemoperfusion for the removal of circulating superantigens in a rat model of streptococcal shock.

DESIGN

In vitro and experimental animal studies.

SETTING

University research laboratories.

INTERVENTIONS

Chemically modified polystyrene-based composite fiber reinforced with polypropylene was formulated in discs and used to evaluate the removal of superantigenic toxins from culture supernatants in vitro, and from blood in vivo.

MEASUREMENTS AND MAIN RESULTS

Incubation of streptococcal supernatant with a single disc reduced the concentration of the superantigen streptococcal pyrogenic exotoxin A from 90.9 +/- 12.7 ng/mL with the control fiber to 32.5 +/- 3.6 ng/mL with active fiber (p <.001). The active discs also brought about a dose-dependent reduction in mitogenic activity that was highly significant (counts reduced from 82,133 +/- 2747 using three control discs to 26,307 +/- 3547 with three active discs [p <.001]). Beginning 6 hrs after infection, animals were hemoperfused for 3 hrs over columns containing control or active fiber. At the end of the treatment period, there was a significant decrease in the number of circulating bacteria in the active group (3.5 x 10(4) vs. 3.1 x 10(3) colony-forming units/mL, p<.05). However, bacterial counts subsequently increased and by 15 hrs and at all subsequent time points, the number of circulating bacteria was no different between the two groups. There was a highly significant and sustained difference in circulating streptococcal pyrogenic exotoxin A levels between the groups. Streptococcal pyrogenic exotoxin A levels at 9 hrs were 19.9 ng/mL in the controls vs. 2.1 ng/mL in the active group (p =.05). Animals perfused over active fibers had a highly significant survival advantage compared with control or nonperfused groups (p <.01).

CONCLUSIONS

Hemoperfusion and on-line removal of superantigens merits further study as a possible treatment strategy for streptococcal shock syndromes. The mechanism by which the fibers are operating requires further investigation.