Organ-specific therapy in critical illness: interfacing molecular mechanisms with physiological interventions

Effect of total body irradiation on late lung effects: hidden dangers

PURPOSE

In our ongoing investigation into the consequences of a radiological terrorism or nuclear dispersion event, we assessed whether a dose range that is believed to be sub-threshold for the development of lung endpoints results in late pathological changes and, secondarily, whether those late changes affect the lung's ability to respond to subsequent challenge.

MATERIALS AND METHODS

C57BL/6J mice received total body irradiation (0.5-10 Gy) and were followed for 6-18 months after irradiation. At 12 and 15 months, a subset of mice was exposed to a second challenge (aerosolised lipopolysaccharide [LPS]).

RESULTS

Cytokines shown to be upregulated early (hours) following irradiation (interleukin [IL]6, keratinocyte chemoattractant [KC], IL1B, and IL1R2) demonstrated increases in messenger ribose nucleic acid (mRNA) expression at late time points, beginning at nine months. Although persistent, dose-dependent increases in T cell counts were seen, no other overt changes in pathophysiology were observed. Nonetheless, animals that were exposed to a secondary challenge at late time points demonstrated an increased inflammatory cell recruitment and persistence in response relative to controls.

CONCLUSIONS

We propose that, following doses that elicit little change in pathophysiology, sub-clinical radiation-induced injury increases the lungs' susceptibility to a secondary challenge, possibly through a radiation-induced alteration in the immune defense system.

P2X7 receptor activation amplifies lipopolysaccharide-induced vascular hyporeactivity via interleukin-1 beta release

Lipopolysaccharide (LPS) stimulates cytoplasmic accumulation of pro-interleukin (IL)-1beta. Activation of P2X(7) receptors stimulates conversion of pro-IL-1beta into mature IL-1beta, which is then secreted. Because both LPS (in vivo) and IL-1beta (in vitro) decrease vascular reactivity to contractile agents, we hypothesized the following: 1) P2X(7) receptor activation contributes to LPS-induced vascular hyporeactivity, and 2) IL-1beta mediates this change. Thoracic aortas were obtained from 12-week-old male C57BL/6 mice. The aortic rings were incubated for 24 h in Dulbecco's modified Eagle's medium, LPS, benzoylbenzoyl-ATP (BzATP; P2X(7) receptor agonist), LPS plus BzATP, oxidized ATP (oATP; P2X(7) receptor antagonist), or oATP plus LPS plus BzATP. After the treatment, the rings were either mounted in a myograph for evaluation of contractile activity or homogenized for IL-1beta and inducible nitric-oxide synthase (iNOS) protein measurement. In endothelium-intact aortic rings, phenylephrine (PE)-induced contractions were not altered by incubation with LPS or BzATP, but they significantly decreased in aortic rings incubated with LPS plus BzATP. Treatment with oATP or IL-1ra (IL-1beta receptor antagonist) reversed LPS plus BzATP-induced hyporeactivity to PE. In the presence of N(G)-nitro-l-arginine methyl ester or N-([3-(aminomethyl)phenyl]methyl)ethanimidamide (selective iNOS inhibitor), the vascular hyporeactivity induced by LPS plus BzATP on PE responses was not observed. BzATP augmented LPS-induced IL-1beta release and iNOS protein expression, and these effects were also inhibited by oATP. Moreover, incubation of endothelium-intact aortic rings with IL-1beta induced iNOS protein expression. Thus, activation of P2X(7) receptor amplifies LPS-induced hyporeactivity in mouse endothelium-intact aorta, which is associated with IL-1beta-mediated release of nitric oxide by iNOS.

Psychoneuroimmunology in critically ill patients

Psychoneuroimmunology is the study of the interactions among behavior, neural, and endocrine functions and the immune system. The purpose of this review is to briefly summarize the evidence concerning interactions among behavior, the neuroendocrine system, and the immune system, and to show how this evidence relates to critical care patients. It has been shown that the immune function of many patients in the intensive care unit is suppressed as a result of trauma, sepsis, or profound physiologic and psychological stress. Three of the most common stressors among patients in the intensive care unit are pain, sleep deprivation, and fear or anxiety. Findings have shown each of these stressors to be associated with decreased immune functioning. Nurses have an important responsibility to protect their patients from infection and promote their ability to heal. Several actions are suggested that can help the nurse achieve these goals. It is hoped that nurses would keep these interactions in mind while caring for their patients in the intensive care unit.

Genetic variation in proinflammatory and anti-inflammatory cytokine production in multiple organ dysfunction syndrome

OBJECTIVES

The objectives of this study were to examine the prevalence of genetic variation for cytokine production (tumor necrosis factor [TNF]-alpha, interleukin-10, transforming growth factor-beta1) in patients with multiple organ dysfunction syndrome, to measure circulating cytokine levels and relate these to genotype, and to identify the relationship between genetic variation and outcome.

DESIGN

Prospective analysis.

SETTING

Intensive care unit of a university teaching hospital.

PATIENTS

Eighty-eight critically ill patients with multiple organ dysfunction syndrome.

MEASUREMENTS AND MAIN RESULTS

The frequency of the different interleukin-10 genotypes (corresponding to high, intermediate, and low interleukin-10 production ) were significantly different between controls and multiple organ dysfunction syndrome patients. High interleukin-10 producers were under-represented in the multiple organ dysfunction syndrome group: This genotype occurred in 30% of controls but in only 6% of patients ( <.001). There was no relationship between interleukin-10 genotype and mortality. The frequency of TNF-alpha genotypes was also significantly different between patients and controls. Intermediate TNF-alpha producers were under-represented (5.7% vs. 23%) and high TNF-alpha producers over-represented (35.2% vs. 16%) in the patient group (p <.001). TNF-alpha genotype was not related to mortality. The distribution of TNF-beta genotypes (homozygous B1, homozygous B2, and heterozygotes) was also different between controls and patients (p =.008). The B2/B2 genotype (associated with high TNF-alpha production) tended to occur less frequently in the intensive care unit population (31% vs. 50%) and was associated with a higher mortality rate than either the B1/B1 or B1/B2 genotypes (48% vs. 11% and 33% respectively, p=.115). The combination of proinflammatory (TNF-alpha/TNF-beta) and anti-inflammatory (interleukin-10/transforming growth factor-beta1) cytokine genotypes was associated with prolonged patient survival time. Patients predisposed to produce a balanced cytokine response (e.g., intermediate interleukin-10/TNF-alpha producers) demonstrated the longest survival times, although overall mortality was no different.

CONCLUSION

A genetic predisposition to high interleukin-10 production or intermediate TNF-alpha production may be protective of admission to the intensive care unit, although once admitted, any protection provided by these genotypes seems to be lost. TNF-beta genotype conferred no advantage to patients with multiple organ dysfunction syndrome, the TNFB2 allele being associated with increased mortality. The combination of proinflammatory and anti-inflammatory cytokine genotypes supports the idea that a balanced cytokine response is favorable and was associated with prolonged patient survival time.

Multi-drug strategies are necessary to inhibit the synergistic mechanism causing tissue damage and organ failure in post infectious sequelae

The paper discusses the principal evidence that supports the concept that cell and tissue injury in infectious and post-infectious and inflammatory sequelae might involve a deleterious synergistic interaction among microbial- and host-derived pro-inflammatory agonists. Experimental models had proposed that a rapid cell and tissue injury might be induced by combinations among subtoxic amounts of three major groups of agonists generated both by microorganisms and by the host's own defense systems. These include: (1) oxidants: Superoxide, H(2)O(2), OH', oxidants generated by xanthine-xanthine-oxidase, ROO; HOC1, NO, OONO'-, (2) the membrane-injuring and perforating agents, microbial hemolysins, phospholipases A(2) and C, lysophosphatides, bactericidal cationic proteins, fatty acids, bile salts and the attack complex of complement a, certain xenobics and (3) the highly cationic proteinases, elastase and cathepsin G, as well as collagenase, plasmin, trypsin and a variety of microbial proteinases. Cell killing by combinations among the various agonists also results in the release of membrane-associated arachidonate and metabolites. Cell damage might be further enhanced by certain cytokines either acting directly on targets or through their capacity to prime phagocytes to generate excessive amounts of oxidants. The microbial cell wall components, lipoteichoic acid (LTA), lipopolysaccharides (LPS) and peptidoglycan (PPG), released following bacteriolysis, induced either by cationic proteins from neutrophils and eosinophils or by beta lactam antibiotics, are potent activators of macrophages which can release oxidants, cytolytic cytokines and NO. The microbial cell wall components can also activate the cascades of coagulation, complement and fibrinolysis. All these cascades might further synergize with microbial toxins and metabolites and with phagocyte-derived agonsits to amplify tissue damage and to induce septic shock, multiple organ failure, 'flesh-eating' syndromes, etc. The long persistence of non-biodegradable bacterial cell wall components within activated macrophages in granulomatous inflammation might be the result of the inactivation by oxidants and proteinases of bacterial autolytic wall enzymes (muramidases). The unsuccessful attempts in recent clinical trials to prevent septic shock by the administration of single antagonists is disconcerting. It does suggest however that, since tissue damage in post-infectious syndromes is most probably the end result of synergistic interactions among a multiplicity of agents, only agents which might depress bacteriolysis in vivo and 'cocktails' of appropriate antagonists, but not single antagonists, if administered at the early phases of infection especially to patients at high risk, might help to control the development of post-infectious syndromes. However, the use of adequate predictive markers for sepsis and other post-infectious complications is highly desirable. Although it is conceivable that anti-inflammatory strategies might also be counter-productive as they might act as 'double-edge swords', intensive investigations to devise combination therapies are warranted. The present review also lists the major anti-inflammatory agents and strategies and combinations among them which have been proposed in the last few years for clinical treatments of sepsis and other post-infectious complications.

Apheresis of plasma compounds as a therapeutic principle in severe sepsis and multiorgan dysfunction syndrome

During sepsis there is an increase in the plasma content of several compounds, e.g., bacterial toxins, cytokines, cell debris, free hemoglobin and myoglobin. In blood, these compounds activate various cascade systems, which in large amounts or in more vulnerable patients lead to a disseminated intra-vascular coagulopathy (DIC) with multiorgan dysfunction syndrome (MODS) and death, despite conventional intensive care unit therapy. Therapeutic attempts to reverse these conditions have so far been of limited benefit. These effects have mainly been focused on lowering the blood concentration of single substances such as tumor necrosis factor. By the use of low-and high-flux hemodialysis filters, usually only small amounts of these substances are removed. By the use of plasmapheresis or plasma exchange, the extent of removal is considerably increased. The efficacy varies between the techniques (centrifugation vs. filtration or adsorption) and has also different influences on e.g. the complement system. This report describes these techniques and the therapeutical possibilities given by them. In small trials, blood or plasma exchange has been used as rescue therapy in critically ill patients with a progressive MODS and DIC. A survival of about 80% of the patients has been reported in these studies and the use of combined therapy will be discussed. Controlled trials are required in this field.

Organ failure, infection, and the systemic inflammatory response syndrome are associated with elevated levels of urinary intestinal fatty acid binding protein: study of 100 consecutive patients in a surgical intensive care unit

BACKGROUND

Intestinal mucosal ischemia and subsequent barrier dysfunction have been related to the development of organ dysfunction and death in the critically ill. We hypothesized that urine concentrations of intestinal fatty acid binding protein (IFABP), a sensitive marker of intestinal ischemia, might predict the development of the systemic inflammatory response syndrome (SIRS) and organ dysfunction.

METHODS

One hundred consecutive critically ill patients were prospectively studied for the development of infectious complications, organ dysfunction, and SIRS. Urine was collected daily for measurement of IFABP.

RESULTS

A total of 58 males and 42 females (mean age, 56 years; range,16-85 years) were studied. Of these 100 patients, 40 patients developed complications and 5 patients developed SIRS. IFABP was significantly elevated in all patients with SIRS, and IFABP levels peaked an average of 1.4 days (range, 0-7 days) before the diagnosis of SIRS.

CONCLUSION

Elevated concentrations of urine IFABP correlated with the clinical development of SIRS. Studies to assess the utility of IFABP as a predictor of organ dysfunction and SIRS in the critically ill are warranted.