Increased intestinal permeability is associated with the development of multiple organ dysfunction syndrome in critically ill ICU patients

Glutamine supplementation in serious illness: a systematic review of the evidence

OBJECTIVE

To examine the relationship between glutamine supplementation and hospital length of stay, complication rates, and mortality in patients undergoing surgery and experiencing critical illness.

DATA SOURCES

Computerized search of electronic databases and search of personal files, abstract proceedings, relevant journals, and review of reference lists.

STUDY SELECTION

We reviewed 550 titles, abstracts, and articles. Primary studies were included if they were randomized trials of critically ill or surgical patients that evaluated the effect of glutamine vs. standard care on clinical outcomes. DATA EXTRACTION We abstracted relevant data on the methodology and outcomes of primary studies in duplicate, independently. DATA SYNTHESIS There were 14 randomized trials comparing the use of glutamine supplementation in surgical and critically ill patients. When the results of these trials were aggregated, with respect to mortality, glutamine supplementation was associated with a risk ratio (RR) of 0.78 (95% confidence interval [CI], 0.58-1.04). Glutamine supplementation was also associated with a lower rate of infectious complications (RR, 0.81; 95% CI, 0.64-1.00) and a shorter hospital stay (-2.6 days; 95% CI, -4.5 to -0.7). We examined several -specified subgroups. Although there were no statistically significant subgroup differences detected, there were some important trends. With respect to mortality, the treatment benefit was observed in studies of parenteral glutamine (RR, 0.71; 95% CI, 0.51-0.99) and high-dose glutamine (RR, 0.73; 95% CI, 0.53-1.00) compared with studies of enteral glutamine (RR, 1.08; 95% CI, 0.57-2.01) and low-dose glutamine (RR, 1.02; 95% CI, 0.52-2.00). With respect to hospital length of stay, all of the treatment benefit was observed in surgical patients (-3.5 days; 95% CI, -5.3 to -1.7) compared with critically ill patients (0.9 days; 95% CI, -4.9 to 6.8).

CONCLUSION

In surgical patients, glutamine supplementation may be associated with a reduction in infectious complication rates and shorter hospital stay without any adverse effect on mortality. In critically ill patients, glutamine supplementation may be associated with a reduction in complication and mortality rates. The greatest benefit was observed in patients receiving high-dose, parenteral glutamine.

Intraischemic hypothermia differentially modulates oxidative stress proteins during mesenteric ischemia/reperfusion

BACKGROUND

Thoracoabdominal aortic aneurysm repair requires obligatory mesenteric ischemia/reperfusion (I/R), eliciting an inflammatory response resulting in gut dysfunction and remote organ injury. Therapeutic hypothermia has been advocated for organ protection (ie, brain, spinal cord, and kidneys) during extensive aortic operation, and it has also been shown to differentially modulate proinflammatory gene transcription in the central nervous system. In other I/R models, nuclear factor Kappa-B (NF-(kappa)B) and inducible nitric oxide synthase (iNOS) worsen while heme oxygenase-1 (HO-1) protects against injury. We examined the effects of regional intraischemic hypothermia on mesenteric I/R-induced mucosal injury, NF-kappaB activation, and expression of iNOS and HO-1.

METHODS

Sprague-Dawley rats underwent sham laparotomy or superior mesenteric artery occlusion for 45 minutes with or without topical hypothermia (15 degrees -20 degrees C). Intestinal epithelial permeability to (14)C inulin was assessed at 6 hours of reperfusion. In a separate set of experiments, biopsies of the ileum were obtained at 6 hours of reperfusion for: 1) mucosal histologic injury assessed by a blinded observer; 2) NF-kappaB activation by electrophoretic mobility shift assay; and 3) iNOS and HO-1 protein expression by immunoblot.

RESULTS

Mesenteric I/R significantly increased intestinal permeability to (14)C inulin, histologic injury, activation of NF-kappaB, and iNOS and HO-1 expression when compared with sham control rats. In contrast, rats treated with intraischemic topical hypothermia exhibited intestinal permeability comparable with sham control rats, and reduced histologic injury. In addition, hypothermia prevented the activation of NF-kappaB and iNOS expression, but had no effect on HO-1 expression.

CONCLUSIONS

On the basis of these observations, we conclude that therapeutically applied intraischemic hypothermia protects the gut during mesenteric I/R. In addition, hypothermia prevented NF-kappaB activation while differentially modulating expression of the oxidative stress proteins iNOS and HO-1 in response to mesenteric I/R.

Epidermal growth factor reduces ischemia-reperfusion injury in rat small intestine

OBJECTIVE

To measure the effect of pre-ischemic administration of intraluminal epidermal growth factor on the changes in intestinal permeability induced by 30 mins of superior mesenteric artery occlusion, followed by 2 hrs of reperfusion.

DESIGN

Prospective, randomized, placebo-controlled experimental study.

SETTING

University basic science research laboratory.

SUBJECTS

Healthy, young, adult, male Sprague-Dawley rats.

INTERVENTIONS

A 10-cm segment of small intestine was isolated and studied in situ in rats that were anesthetized with fentanyl and mechanically ventilated. Intestinal ischemia-reperfusion injury was induced by temporary occlusion of the superior mesenteric artery for 30 mins, followed by 2 hrs of reperfusion. Three groups were studied: time controls with a sham operation, saline-treated ischemia-reperfusion, and epidermal growth factor-treated ischemia-reperfusion. Epidermal growth factor, 100 ng/min, was infused intraluminally, beginning 30 mins before and continued until 40 mins after ischemia.

MEASUREMENTS AND MAIN RESULTS

Intestinal permeability was measured for each 10-min time period by using chromium-labeled EDTA. Histopathologic injury was assessed by light microscopy. After superior mesenteric artery occlusion, intestinal permeability increased approximately ten-fold and was sustained for 2 hrs of reperfusion in saline-treated rats. Pretreatment with epidermal growth factor significantly reduced the permeability changes during reperfusion by >60% compared with saline-treated animals (p <.05). Histopathologic sections revealed apparently more extensive loss of epithelial cells and mucosal disruption in saline-treated intestine compared with epidermal growth factor-treated intestine.

CONCLUSION

Pre-ischemic administration of intraluminal epidermal growth factor significantly protects against intestinal ischemia-reperfusion injury.

IL-10 is not protective in intestinal ischemia reperfusion injury

BACKGROUND

Ischemia/reperfusion of the small intestine disrupts gut barrier function, increases bacterial translocation, and activates systemic pro-inflammatory responses. Pharmacological treatment with the anti-inflammatory cytokine interleukin-10 (IL-10) following ischemia to muscle reduces the severity of local and systemic inflammation. While endogenous IL-10 is protective in murine models of acute endotoxemia, its physiological role during direct gut injury is unknown.

PATIENTS AND MATERIALS

Mice genetically deficient in IL-10 (IL-10(-/-)) and their normal littermates (IL-10(+/+)) underwent 20 to 50 min of gut ischemia by occlusion of the superior mesenteric artery.

RESULTS

Both short- and long-term (>16 h) survival after reperfusion of IL-10(-/-) mice was identical to that of the wild-type littermates, with 50% mortality observed at 35 min of occlusion. The small bowel demonstrated discrete gross areas of hemorrhage and ischemia localized to the jejunum. No significant difference in the extent or time for occurrence of macroscopic or microscopic intestinal damage to the small bowel was observed in IL-10(-/-) or IL-10(+/+) mice, despite the marked elevation in serum IL-6.

CONCLUSIONS

The absolute serum concentration of IL-6 in the presence or the absence of IL-10 does not affect local or systemic response to ischemic intestinal injury. These results also demonstrate that the anti-inflammatory cytokine IL-10 does not play a significant local or systemic protective role in this model of ischemia/reperfusion.

Thinking outside the box: mechanisms of environmental selective pressures on the outcome of the materno-fetal relationship

PROBLEM

Study of mechanisms causing spontaneous abortion of the vascularized placenta have focused primarily on the feto-maternal immunological relationship within the pregnant mother. The Th1 cytokines such as tumor necrosis factor (TNF)-alpha + interferon (IFN)-gamma derived in part from natural killer (NK) and NKgammadeltaT cells have been implicated in causing abortion via up-regulation of the novel prothrombinase fgl2 at the feto-maternal interface; Th2/3 cytokines such as interleukin (IL)-10, progesterone-induced blocking factor (PIBF), and TGF-beta2 derived from gammadeltaT cells stimulated by embryo antigens in the context of the OX-2 (CD200) tolerance signal have been viewed as counteracting the Th1 effect. These mechanisms are distinct from those causing and preventing occult pregnancy loss during the periimplantation phase of pregnancy prior to development of a vascularized placenta. Spontaneous abortions in the CBA/J x DBA/2 can be boosted by injecting TNF-alpha + IFN-gamma, but the boosted abortion rates can range from < or = 30 to > 80%, depending on the loss rate in uninjected mice, and this is not explainable by the endogenous level of these cytokines. Furthermore, there is a poor correlation between Th1/Th2.3 cytokine ratios and abortion rates. Could there be a third factor involved, and if so, what might this mean?

METHODS

Known precipitants of recurrent abortion in mice were reviewed with particular attention to stress and endotoxin absorption. The effect of antagonizing the response to bacterial lipopolysaccharide (LPS) (endotoxin) was tested. Data on environmental selective pressures were considered (i.e. thinking outside the 'box', which typifies the conventional approach to thinking about materno-fetal interactions).

RESULTS

Th1 cytokine-triggered abortions appear to depend on availability/presence of LPS.

CONCLUSIONS

Environmental selective pressures are implicated in eliminating 'genetically weaker' embryos in early pregnancy.

Intestinal permeation and gastrointestinal disease

The gastrointestinal tract constitutes one of the largest sites of exposure to the outside environment. The function of the gastrointestinal tract in monitoring and sealing the host interior from intruders is called the gut barrier. A variety of specific and nonspecific mechanisms are in operation to establish the host barrier; these include luminal mechanisms and digestive enzymes, the epithelial cells together with tight junctions in between them, and the gut immune system. Disruptions in the gut barrier follow injury from various causes including nonsteroidal anti-inflammatory drugs and oxidant stress, and involve mechanisms such as adenosine triphosphate depletion and damage to epithelial cell cytoskeletons that regulate tight junctions. Ample evidence links gut barrier dysfunction to multiorgan system failure in sepsis and immune dysregulation. Additionally, contribution of gut barrier dysfunction to gastrointestinal disease is an evolving concept and is the focus of this review. An overview of the evidence for the role of gut barrier dysfunction in disorders such as Crohn's disease, celiac disease, food allergy, acute pancreatitis, non-alcoholic fatty liver disease, and alcoholic liver disease is provided, together with critical insight into the implications of this evidence as a primary disease mechanism.

Role of the gut lymphatic system in multiple organ failure

The central concept of this review is that gut-derived factors contained primarily in the mesenteric lymph rather than the portal blood contribute to distant organ injury. This hypothesis is supported by recent studies indicating that division of the mesenteric lymphatic ducts prevents lung injury after hemorrhagic shock and significantly ameliorates lung injury after thermal injury. The mechanism of hemorrhagic shock-induced lung injury appears to be through mesenteric lymph-induced activation of neutrophils and activation/injury of endothelial cells. This notion is supported by in vitro studies indicating that mesenteric lymph, but not portal vein plasma, collected after a nonlethal episode of hemorrhagic shock activates neutrophils, increases endothelial cell monolayer permeability, and can even cause endothelial cell death. This concept that gut-derived factors contained primarily in the mesenteric lymph rather than the portal system potentiate the development of distant organ (lung) injury, if correct, would help clarify several important issues. First, because the lung is the first organ exposed to mesenteric lymph (i.e., mesenteric lymph enters the subclavian via the thoracic duct), it would help explain the clinical observation of why the lung is generally the first organ to fail in severely injured patients. Second, this gut lymphatic hypothesis would provide new information on the pathophysiology of gut-induced lung injury. Finally, it would help explain the discordant results between experimental and some clinical studies on the role of gut injury and loss of gut barrier function in the development of a systemic inflammatory state and distant organ injury.

Enteral feeding decreases gut apoptosis, permeability, and lung inflammation during murine endotoxemia

We tested the hypothesis that endotoxemia and fasting are associated with increased gut apoptotic activity, gut permeability, and inflammation in a distant organ. Fed or fasted CD-1 mice were studied 6 h after intraperitoneal injection of either saline (sham) or endotoxin (4 mg/kg of 0111:B4 Escherichia coli lipopolysaccharide). We found that endotoxin increased gut caspase-3 and -6 activity by 4.9 +/- 0.6- and 4.5 +/- 0.5-fold, respectively (P < 0.001), and increased terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) staining of mucosal cells (P < 0.05). Feeding decreased caspase-3 activity by 40% (P < 0.05) and decreased endotoxin-induced TUNEL staining (P < 0.05). Endotoxin increased gut poly(ADP-ribose) polymerase activity by 15% (P < 0.05). Endotoxin increased gut permeability by 44% (P < 0.05), an effect reduced 36% by feeding (P < 0.05). Similarly, endotoxin increased pulmonary neutrophil infiltration (6.0 +/- 1.0-fold, P < 0.001) and increased lung interleukin (IL)-6 (5.9 +/- 0.1-fold, P < 0.001) and macrophage inflammatory protein (MIP)-2 expression (290 +/- 40-fold, P < 0.001), whereas feeding decreased this effect by 43% for neutrophils, 40% for IL-6 (P < 0.05), and 35% for MIP-2 (P < 0.05). Thus endotoxin increases gut apoptotic activity, gut permeability, and pulmonary inflammation. Enteral feeding may decrease the distant organ inflammation by reducing gut apoptosis, thereby maintaining gut mucosal function during endotoxemia.

Pediatric sepsis and multiple organ dysfunction syndrome

Systemic inflammatory response syndrome may be viewed as the systemic expression of cytokine signals that normally function on an autocrine or paracrine level. Sepsis is defined as systemic inflammatory response syndrome caused by an infection. Multiple organ dysfunction syndrome may represent the end stage of severe systemic inflammatory response syndrome or sepsis. Many cells are involved, including endothelial cells and leukocytes and multiple proinflammatory and antiinflammatory mediators (cytokines, oxygen free radicals, coagulation factors, and so forth). Various pathophysiologic mechanisms have been postulated. The most popular theory is that the inflammatory process loses its autoregulatory capacity; however, microcirculatory dysregulation and apoptosis may also be important, and a new paradigm posits a complex nonlinear system. Many new treatments have been studied recently. The usefulness of immune modulating diets remains to be evaluated. Molecular immunomodulation is still of unclear value. The therapy of sepsis and multiple organ dysfunction syndrome remains mainly supportive.

Validation of a blind transpyloric feeding tube placement technique in pediatric intensive care: rapid, simple, and highly successful

OBJECTIVE

Nasogastric feeding in intensive care is poorly tolerated as a result of gastroparesis. Transpyloric (TP) feeding has been limited by difficulty in tube placement. This study was to independently validate the success rate of a previously published bedside TP feeding tube (FT) placement technique.

DESIGN

Prospective interventional study.

SETTING

Tertiary pediatric intensive care unit (PICU) in a university hospital.

PATIENTS

Children whose intensivist requested TP feeding, and who were without known fundoplication, pharyngeal trauma, or gastric ulceration.

INTERVENTIONS

After informed consent, an unweighted polyurethane feeding tube with a flexible wire stylet was inserted using a standard technique with metoclopramide, right lateral position, and air insufflation during advancement until <2 mL air could be aspirated after insufflation of 5-10 mL air. The tubes were inserted by one of the authors, whose training was only to observe one insertion, then perform one insertion with supervision.

MEASUREMENTS AND MAIN RESULTS

Patient demographics, procedural data, and success rate based on radiography were prospectively recorded. There were 71 insertions on 38 patients from February 1999 to October 1999. Patients were aged 56 +/- 69.8 months, weighed 17.8 +/- 18 kg, 69% were ventilated, and 56% received procedural sedation. Success rate for TP-FT placement was 63/71 insertions (88.7%) in an average of 7.43 +/- 6.85 mins (median, 5 mins; range, <1-45 mins); of 38 patients, 36 had a successful TP- FT (95%). Insertion was well tolerated. Of the successful TP-FTs, on day 1 (n = 63) the FT was in distal duodenum or jejunum in 51% and by days 3-5 (n = 51), this increased to 75%.

CONCLUSIONS

Bedside placement of a TP-FT with this technique is simple, rapid, well tolerated, and highly successful with little training. Immediate radiograph to confirm TP placement may not always be necessary. In our experience, this technique has obviated the need to search for another method to achieve a transpyloric feeding tube.

Surgical stress and the gastrointestinal tract

Surgery on any part of the body results in a wide spectrum of alterations in normal body homeostasis. The gastrointestinal tract is extremely sensitive to surgical stress, even at remote locations. It is now evident that the G.I. tract also plays an important role in development of postoperative complications, such as the systemic immune response syndrome and multiple organ failure syndrome. The amount of information available on the cellular and subcellular changes occurring in the gastrointestinal tract after surgical stress is scant. These changes are important since they would act as initiators of tissue damage seen at a later stage, which in turn lead to postoperative complications. This review looks at the information available on the effect of surgical stress on the small intestine, the role of oxygen free radicals in this process, and the changes occurring at the cellular level.

Increased gut permeability and bacterial translocation in Pseudomonas pneumonia-induced sepsis

OBJECTIVE

Gut injury and barrier dysfunction may contribute to the pathogenesis of sepsis and multiple organ dysfunction syndrome. The objective of this study was to determine whether gut injury could be demonstrated in hyperdynamic, normotensive sepsis induced by Pseudomonas pneumonia.

DESIGN

Randomized animal study.

SETTING

University laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Sepsis was induced by intratracheal instillation of Pseudomonas aeruginosa.

MEASUREMENTS AND MAIN RESULTS

We measured gut mucosal and microvascular injury. In the first experiment, gut mucosal permeability was measured by 51Cr-EDTA uptake in control (n = 6), pneumonia 20-hr (n = 4), and pneumonia 40-hr (n = 4) groups. In the second experiment, microvascular permeability was measured by albumin extravasation, and morphologic abnormalities were scored in control (n = 6), pneumonia 20-hr (n = 9), and pneumonia 40-hr (n = 11) groups. Bacterial translocation to mesenteric lymph nodes was determined in both experiments. Cardiac index increased significantly in the pneumonia compared with control rats (64+/-2.1, 68+/-1.3, vs. 46+/-2 mL/min/100 g, p < .05; all results are listed in the order of pneumonia 20-hr, pneumonia 40-hr, and control groups as mean +/- SEM). Mean blood pressure was normal and was not different between groups (112+/-3, 111+/-2, vs. 118+/-2 mm Hg). 51Cr-EDTA recovery in urine 6 hrs after gavage increased significantly in both pneumonia groups vs. controls (17.5+/-2.2%, 17.9+/-7%, vs. 4+/-0.7%; p < .05). Albumin leak (tissue/plasma ratio) increased significantly in the middle and distal small intestine in the pneumonia 40-hr group vs. controls (0.68+/-0.05, 0.76+/-0.07, vs. 0.45+/-0.04, p < .05 in the middle small gut; 0.75+/-0.09, 0.85+/-0.07, vs. 0.51+/-0.05, p < .05 in the distal small gut). Bacterial translocation to mesenteric lymph nodes increased significantly in pneumonia 40-hr rats vs. controls (positive culture 67% vs. 8%; p < .05).

CONCLUSIONS

This study demonstrates gut mucosal and microvascular injury and gut barrier dysfunction in normotensive sepsis secondary to bacterial pneumonia. The mechanism and significance of the injury need to be determined.

Resuscitation of critically ill patients based on the results of gastric tonometry: a prospective, randomized, controlled trial

OBJECTIVE

To determine whether additional therapy aimed at correcting low gastric intramucosal pH (pHi) improves outcome in conventionally resuscitated, critically ill patients.

DESIGN

Prospective, randomized, controlled study.

SETTING

General intensive care unit (ICU) of a university teaching hospital.

PATIENTS

A total of 210 adult patients, with a median Acute Physiology and Chronic Health Evaluation II score of 24 (range, 8-51).

INTERVENTIONS

All patients were resuscitated according to standard guidelines. After resuscitation, those patients in the intervention group with a pHi of <7.35 were treated with additional colloid and then dobutamine (5 microg/kg/min then 10 microg/kg min) until 24 hrs after enrollment.

MEASUREMENTS AND MAIN RESULTS

There were no significant differences (p > .05) in ICU mortality (39.6% in the control group vs. 38.5% in the intervention group), hospital mortality (45.3% in the control group vs. 42.3% in the intervention group), and 30-day mortality (43.7% in the control group vs. 40.2 in the intervention group); survival curves; median modified maximal multiorgan dysfunction score (10 points in the control group vs. 13 points in the intervention group); median modified duration of ICU stay (12 days in the control group vs. 11.5 days in the intervention group); or median modified duration of hospital stay (60 days in the control group vs. 42 days in the intervention group). A subgroup analysis of those patients with gastric mucosal pH of > or =7.35 at admission revealed no difference in ICU mortality (10.3% in the control group vs. 14.8% in the intervention group), hospital mortality (13.8% in the control group vs. 29.6% in the intervention group), or 30-day mortality (10.3% in the control group vs. 26.9% in the intervention group).

CONCLUSIONS

The routine use of treatment titrated against pHi in the management of critically ill patients cannot be supported. Failure to improve outcome may be caused by an inability to produce a clinically significant change in pHi or because pHi is simply a marker of disease rather than a factor in the pathogenesis of multiorgan failure.

The gut: the 'motor' of multiple organ dysfunction syndrome?

Abnormal colonization, gut-origin infections, and bacterial translocation are all signs of gut dysfunction that may be implicated in the pathogenesis of multiple organ dysfunction syndrome (MODS). This review summarizes and updates relevant experimental and clinical data that have attempted to correlate these phenomena with the development of MODS and to answer whether or not the gut is the 'motor' of MODS. The presented data suggest that, in some patients, gut dysfunction may precede the development of MODS. However, in most patients, this relationship is less obvious. The gut may still be one of the motors of MODS; however, it does not appear that this motor is fueled by the systemic spread of bacteria. Bacteria may play a role on a local gut-associated level in initiating and perpetuating the production of local inflammatory mediators that may produce distant organ injury.

Duodenal versus gastric feeding in ventilated blunt trauma patients: a randomized controlled trial

OBJECTIVE

To evaluate transpyloric feeds as they have been proposed as a means of providing enteric nutrition more rapidly and minimizing morbidity in ventilated trauma patients.

METHODS

Between July of 1994 and June of 1997, 80 adult ventilated trauma patients were enrolled in a randomized controlled trial of duodenal versus gastric feeds. Feeding was initiated within 72 hours of injury.

RESULTS

Forty-three patients received gastric feeds (G), and 37 patients received duodenal feeds (D). Mean age was 34.7+/-15.7 years (G) and 33.6+/-17.5 years (D); the difference in age was not significant (NS). Mean Injury Severity Score was 30.0+/-11 (G), 33.0+/-9.7 (D), NS. Mean Acute Physiology and Chronic Health Evaluation (APACHE II) score was 18.0+/-6.0 (G) and 18.0+/-7.4 (D), NS. Thirty-four of 43 patients were men (G) and 28 of 37 patients were men (D), NS. Use of narcotics and paralytics between the two groups was not significantly different. Energy requirements were 1.4 times basal energy expenditure at 2,127+/-304 Kcal (G) and 2,089+/-274 Kcal (D), NS. Intensive care unit length of stay was a median of 7 days (range, 3-32 days) (G) and 10 days (range, 3-24 days) (D), NS. Number of days on ventilator was a median of 5 days (range, 3-15 days) (G) and 9 days (range, 2-13 days) (D), NS. Hospital length of stay was a median of 25 days (range, 9-88 days) (G) and 30 days (range, 16-47 days) (D), NS. Recorded morbidity was not significantly different. Pneumonia rates were 42% (G) and 27% (D), NS. Time to tolerate full-strength feeds for 24 consecutive hours was 43.8 hours +/-22.6 (G) and 34.3 hours +/-7.1 (D), difference significant at p = 0.02.

CONCLUSION

Length of stay and ventilator days were not significantly different. A larger trial would be required to determine differences in the rates of pneumonia <20%. Transpyloric-duodenal feeds significantly reduce the time required to achieve targeted enteric nutrition.