Intestinal manipulation during elective aortic aneurysm surgery leads to portal endotoxaemia and mucosal barrier dysfunction

Retroperitoneal Compared to Transperitoneal Approach for Open Abdominal Aortic Aneurysm Repair Is Associated with Reduced Systemic Inflammation and Postoperative Morbidity

BACKGROUND

 In the United Kingdom, the most common surgical approach for repair of open abdominal aortic aneurysms (AAAs) is transperitoneal (TP). However, retroperitoneal (RP) approach is favored in those with more complex vascular anatomy often requiring a cross-clamp on the aorta superior to the renal arteries. This study compared these approaches in patients matched on all major demographic, comorbid, anatomic, and physiological variables.

METHODS

 Fifty-seven patients (TP: n = 24; RP: n = 33) unsuitable for endovascular aneurysm repair underwent preoperative cardiopulmonary exercise testing prior to open AAA repair. The surgical approach undertaken was dictated by individual surgeon preference. Postoperative mortality, complications, and length of hospital stay (LoS) were recorded. Patients were further stratified according to infrarenal (IR) or suprarenal/supraceliac (SR/SC) surgical clamping. Systemic inflammation (C-reactive protein) and renal function (serum creatinine and estimated glomerular filtration rate) were recorded.

RESULTS

 Twenty-three (96%) of TP patients only required an IR clamp compared with 12 (36%) in the RP group. Postoperative systemic inflammation was lower in RP patients (p = 0.002 vs. TP) and fewer reported pulmonary/gastrointestinal complications whereas renal impairment was more marked in those receiving SR/SC clamps (p < 0.001 vs. IR clamp). RP patients were defined by lower LoS (p = 0.001), while mid-/long-term mortality was low/comparable with TP, resulting in considerable cost savings.

CONCLUSION

 Despite the demands of more complicated vascular anatomy, the clinical and economic benefits highlighted by these findings justify the more routine adoption of the RP approach for complex AAA repair.

Elevated Systemic and Intestinal Inflammatory Response Are Associated With Gut Microbiome Disorder After Cardiovascular Surgery

Systemic inflammatory response after cardiovascular surgery is associated with poor prognosis, to which gut barrier impairment is related. To investigate whether perioperative changes of the gut microbiome are associated with systemic and intestinal inflammatory response, we examined changes of the gut microbiome, intestinal homeostasis, and systemic inflammatory response in cardiovascular patients before (Pre) surgery and on the first defecation day [postoperative time 1 (Po1)] or a week [postoperative time 2 (Po2)] postsurgery. Markedly, the enhanced systemic inflammatory response was observed in Po1 and Po2 compared with that in Pre. In line with inflammatory response, impaired gut barrier and elevated gut local inflammation were observed in Po1 and Po2. Microbiome analysis showed a remarkable and steady decline of alpha diversity perioperatively. In addition, microbial composition in the postoperation period was characterized by significant expansion of Enterococcus along with a decrease in anaerobes (Blautia, Faecalibacterium, Bifidobacterium, Roseburia, Gemmiger, [Ruminococcus], and Coprococcus), which were typically health-associated bacteria. Spearman correlation analysis showed microbiome disorder was associated with enhanced systemic inflammatory response and intestinal dysbiosis. These results suggest that microbiome disorder was related to disturbed gut homeostatic and subsequently elevates plasma endotoxin and systemic inflammatory response after cardiovascular surgery. This study not only highlights gut microbiome would be considered in future clinical practice but also proposes a promising perspective of potential diagnostic and therapeutic options for perioperative management of cardiovascular surgery patients.

The retroperitoneal approach for contemporary open abdominal aortic aneurysm surgery: The anatomical reasoning

In current practice, the place of open surgery in managing abdominal aortic aneurysm is a contentious issue. The principal reason being greater applications of endovascular techniques treating increasingly complicated aortic disease. Development of branched and fenestrated devices enabled this, with numbers increasing annually. This meant a good risk patient with a long infrarenal aortic neck and normal diameter non-tortuous iliac arteries may be suitable for both endovascular and open techniques. However, indications for open surgery are becoming increasingly unclear nowadays due to short-term gains in morbidity and mortality. Exact aortic anatomical morphologies optimum for open or endovascular techniques remains unclear. As graft technology evolves, possibilities for endovascular options are expanding. Currently, establishing optimum treatment plans for complicated abdominal aortic aneurysm (little or no infrarenal neck) is difficult without considering general fitness of the patient. Hence, two sets of possible postoperative complications and follow-up protocols must be explained to patients before either approach. Complicating matters is the optimum surgical approach used for any open repair. The standard approach for open abdominal aortic aneurysm surgery has been transperitoneal as this provides excellent access to the infrarenal aorta and iliac arteries. However, although less commonly used, the retroperitoneal approach has advantages particularly when location of proximal aortic disease indicates suprarenal clamp might be optimum. This paper scrutinises benefits of the retroperitoneal approach performed purely for anatomical reasons where stent graft may be considered complicated. Also, long-term outcomes are examined in terms of endo-leak and subsequent development of true and false aneurysm following both endovascular and open repair.

The influence of allopurinol and post-conditioning on lung injuries induced by lower-limb ischemia and reperfusion in Wistar rats

PURPOSE

To analyze the effects of allopurinol and of post-conditioning on lung injuries induced by lower-limb ischemia and reperfusion.

METHODS

Thirty rats were used. They were divided in 5 groups: (1) group A: abdominal aortic dissection only, (2) group B: ischemia and reperfusion, (3) group C: administered allopurinol (100mg/Kg) a few hours before procedure, (4) group D: post-conditioned and (5) group E: administered allopurinol and post-conditioned. With the exception of group A, all groups were submitted to infrarenal aortic ischemia for 2 hours, and reperfusion for 72 hours. After euthanasia, lungs were removed for histological analysis. They were graded under two scores: pulmonary injury (neutrophil infiltration, interstitial edema, vascular congestion, and destruction of lung architecture) and lymphocytic score (neutrophil infiltration, lymphoid aggregate and secondary follicle).

RESULTS

On the pulmonary injury score, the degree of injury was smaller than in groups D and E, when compared to group B, p<0.05. Group C did not obtain the same result (p>0,05). On the lymphocytic score, there was no statistic difference among groups, p>0.05.

CONCLUSION

Both post-conditioning and the combination of allopurinol and post-conditioning were effective in remote lung protection induced by lower-limbs I/R. When used in isolation, allopurinol showed no protective effect.

The Effect of Perioperative Ischemia and Reperfusion on Multiorgan Dysfunction following Abdominal Aortic Aneurysm Repair

Abdominal aortic aneurysms (AAAs) are relatively common and are potentially life-threatening medical problems. The aim of this review is to provide an overview of the effect of I/R injury on multiorgan failure following AAA repair. The PubMed, CINAHL, EMBASE, Medline, Cochrane Review, and Scopus databases were comprehensively searched for articles concerning the pathophysiology of I/R and its systemic effects. Cross-referencing was performed using the bibliographies from the articles obtained. Articles retrieved were restricted to those published in English. One of the most prominent characteristics of AAA open repair is the double physiological phenomenon of ischemia-reperfusion (I/R) that happens either at the time of clamping or following the aortic clamp removal. Ischemia-reperfusion injury causes significant pathophysiological disturbances to distant organs, increasing the possibility for postoperative multiorgan failure. Although tissue injury is mediated by diverse mechanisms, microvascular dysfunction seems to be the final outcome of I/R.

Biomarkers of inflammation in major vascular surgery: a prospective randomised trial

BACKGROUND

Surgery induces inflammation and pro-inflammatory cytokines are associated with post-operative complications. In cardiac surgery, it has been shown that volatile anaesthetics have cardioprotective properties. We explored whether sevoflurane affects the pro-inflammatory response favourably compared with total intravenous anaesthesia (TIVA) after surgery.

METHODS

We measured monocyte chemotactic protein 1 (MCP-1), matrix metalloproteinase 9 (MMP-9), C-reactive protein (CRP), vascular cell adhesion molecule 1 (VCAM-1), interleukin (IL)-6 and IL-8 perioperatively and evaluated if the anaesthetic regimen affected these mediators. Our hypothesis was that sevoflurane-based anaesthesia is associated with a reduced release of biomarkers of inflammation compared with TIVA with propofol/remifentanil.

RESULTS

In the total population, MCP-1, MMP-9, IL-6 and IL-8 increased 30 min after arrival intensive care unit, compared with before surgery (P < 0.001), whereas CRP and VCAM-1 transiently declined (P < 0.001). From 30 min after arrival intensive care unit to 1st post-operative day, MCP-1 and IL-6 levels declined (P < 0.001), CRP and VCAM-1 increased (P < 0.001), whereas MMP-9 and IL-8 were not significantly altered. Pre-operatively there were no significant differences in any variables between the two anaesthetic groups. Lower levels of MCP-1 and IL-8 (P < 0.001) and higher levels of IL-6 and MMP-9 (P = 0.003) were found in the sevoflurane group, compared with the TIVA group 30 min post-operatively. CRP and VCAM-1 levels did not differ. There were no significant differences between the two anaesthetic groups before surgery or at 1st post-operative day.

CONCLUSION

We found an inflammatory response during the observation period, which was modified by the anaesthetic regimen in the early phase. This short-lasting difference is probably too short to support a cardioprotective effect of sevoflurane compared with TIVA in open abdominal aortic surgery.

The impact of endovascular repair of ruptured abdominal aortic aneurysm on the gastrointestinal and renal function

Introduction. Systemic effects of ruptured abdominal aortic aneurysm (rAAA) may be altered by the mode of surgery. This study aimed to determine systemic effects of endovascular aneurysm repair (EVAR) compared to open repair (OR). Patients and Methods. Consecutive patients with rAAA were repaired by OR or EVAR according to computerised tomographic (CT) findings. Renal function was monitored by estimated glomerular filtration rate (eGFR), serum urea and creatinine, and urinary albumin creatinine ratio (ACR). Hepatic function was assessed postoperatively for 5 days. Intestinal function was determined by the paracetamol absorption test. Intestinal permeability was assessed by urinary lactulose/mannitol ratio. Results. 30 rAAA patients were included. Fourteen had eEVAR and sixteen eOR. Serum urea were higher in eOR, while creatinine was similar between groups. Hepatic function showed no intergroup difference. Paracetamol absorption was increased in eEVAR group at day 3 compared to day 1 (P = 0.03), with no similar result in eOR (P = 0.24). Peak lactulose/mannitol ratio was higher in eOR (P = 0.03), with higher urinary L/M ratio in eOR at day 3 (P = 0.02). Clinical intestinal function returned quicker in eEVAR (P = 0.02). Conclusion. EVAR attenuated the organ dysfunction compared to open repair. However, a larger comparative trial would be required to validate this. The clinical trial is registered with reference number EUDRACT: 2013-003373-12.

Low doses of celecoxib attenuate gut barrier failure during experimental peritonitis

The intestinal barrier becomes compromised during systemic inflammation, leading to the entry of luminal bacteria into the host and gut origin sepsis. Pathogenesis and treatment of inflammatory gut barrier failure is an important problem in critical care. In this study, we examined the role of cyclooxygenase-2 (COX-2), a key enzyme in the production of inflammatory prostanoids, in gut barrier failure during experimental peritonitis in mice. I.p. injection of LPS or cecal ligation and puncture (CLP) increased the levels of COX-2 and its product prostaglandin E2 (PGE2) in the ileal mucosa, caused pathologic sloughing of the intestinal epithelium, increased passage of FITC-dextran and bacterial translocation across the barrier, and increased internalization of the tight junction (TJ)-associated proteins junction-associated molecule-A and zonula occludens-1. Luminal instillation of PGE2 in an isolated ileal loop increased transepithelial passage of FITC-dextran. Low doses (0.5-1 mg/kg), but not a higher dose (5 mg/kg) of the specific COX-2 inhibitor Celecoxib partially ameliorated the inflammatory gut barrier failure. These results demonstrate that high levels of COX-2-derived PGE2 seen in the mucosa during peritonitis contribute to gut barrier failure, presumably by compromising TJs. Low doses of specific COX-2 inhibitors may blunt this effect while preserving the homeostatic function of COX-2-derived prostanoids. Low doses of COX-2 inhibitors may find use as an adjunct barrier-protecting therapy in critically ill patients.

Corticotropin-releasing factor: a possible key to gut dysfunction in the critically ill

Critically ill patients frequently display unexplained or incompletely explained features of gastrointestinal (GI) dysfunction, including gastric stasis, ileus, and diarrhea. This makes nutrition delivery challenging, and may contribute to poor outcomes. The typical bowel dysfunction seen in severely ill patients includes retarded gastric emptying, unsynchronized intestinal motility, and intestinal hyperpermeability. These functional changes appear similar to the corticotropin-releasing factor (CRF)-mediated bowel dysfunctions associated with stress of various types and some GI disorders and diseases. CRF has been shown to be present within the GI tract and its action on CRF receptors within the gut have been shown to reduce gastric emptying, alter intestinal motility, and increase intestinal permeability. However, the precise role of CRF in the GI dysfunction in critical illness remains unclear. In this short review, we provide an update on GI dysfunction during stress and review the possible role of CRF in the aetiology of gut dysfunction. We suggest that activation of CRF signaling pathways in critical illness might be key to understanding the mechanisms underlying the gut dysfunction that impairs enteral feeding in the intensive care unit.

Trans-Serosal Leakage of Proinflammatory Mediators during Abdominal Aortic Aneurysm Repair: Role of Phospholipase A2 in Activating Leukocytes

Gut barrier failure and the resultant translocation of luminal bacteria and bacterial products into the systemic circulation have been proposed as pathogenic mechanisms of multiorgan dysfunction syndrome (MODS) in open repair of abdominal aortic aneurysm (AAA). Our study aimed to demonstrate the direct release of gut-derived inflammatory mediators via the trans-serosal route in humans. Fifteen patients who underwent elective infrarenal open repair of AAA were randomized into two groups. In Group I patients (n = 10), the small intestine was exteriorized into a bowel bag. In Group II patients (n = 5), the small intestine was packed within the peritoneal cavity using large gauzes. We collected the bowel bag fluid in Group I and the ascites fluid, squeezed out from the gauzes at the end of surgery, in Group II. Leukocytes were collected from patients' blood samples. Incubation with the bowel bag fluid and ascites fluid caused a significant increase in both granulocyte pseudopod formation and CD11b expression compared to that with control fluid (p < 0.01). The addition of phospholipase A2 (PLA2) inhibitor quinacrine abolished leukocyte activation by the bowel bag fluid. Based on these results, we consider that trasns-serosal leakage of gut-derived mediators occurred during the open repair of AAA; further, sPLA2 may be the most potent mediator in the activation of leukocytes among such gut-derived mediators in AAA surgery.

Retroperitoneal approach to abdominal aortic aneurysm repair preserves splanchnic perfusion as measured by gastric tonometry

BACKGROUND

We investigated if minimizing bowel manipulation and mesenteric traction using the retroperitoneal approach in open abdominal aortic aneurysm (AAA) repair preserves splanchnic perfusion, as measured by gastric tonometry, and reduces the systemic inflammatory response and dysfunction of the various organs.

METHODS

Patients undergoing elective AAA repair were randomized into three groups. Group I had repair via the retroperitoneal approach, while groups II and III were repaired via the transperitoneal approach with the bowel packed within the peritoneal cavity or exteriorized in a bowel bag, respectively. A tonometer was used to measure gastric intramucosal pH (pHi), as an indicator of splanchnic perfusion, just prior to aortic clamping, during clamping, and at 0.5, 1, 2, 4, 6, and 12 hr after clamp release. Multiorgan dysfunction syndrome (MODS) and systemic inflammatory response syndrome (SIRS) scores were calculated and systemic interleukins (IL-6 and IL-10) measured at predetermined intervals.

RESULTS

Thirty-four patients were successfully randomized. The gastric pHi was significantly lower in group II (n=12) and group III (n=11) compared to group I (n=11) during aortic clamping and immediately after clamp release (p<0.05). The aortic clamp time, blood loss, MODS and SIRS scores, and systemic cytokine response were similar in all three groups. When the three groups were combined, there were significant positive correlations between the operation time, aortic clamp time, and amount of blood lost and transfused with plasma IL-6 levels and MODS score on the first postoperative day.

CONCLUSION

The retroperitoneal approach for open AAA repair is associated with gastric tonometric evidence of better splanchnic perfusion compared to the transperitoneal approach.

Translocation of bacterial NOD2 agonist and its link with inflammation

INTRODUCTION

The gut is often considered as the motor of critical illness through bacterial translocation, which amplifies the inflammatory response and alters the immune status. However, systemic bacterial translocation was rarely proven and endotoxin measurement only reflects translocation of Gram-negative-derived products. The process could be more frequently identified if peptidoglycan, derived from both Gram-negative and Gram-positive bacteria, was measured.

METHODS

We developed a new tool to detect circulating peptidoglycan-like structure using a NOD2-transfected cell line. We also measured plasma and cell-associated endotoxin and different plasma markers of inflammation. We studied 21 patients undergoing abdominal aortic surgery (AAS), and 21 patients undergoing carotid artery surgery (CAS) were included as negative controls. Patients were sampled during surgery until two days post-surgery.

RESULTS

In 90.5% of the AAS patients, a NOD2 agonist peak was detected in plasma before aortic clamping, but after gut manipulation by the surgeon, and persisted after blood reperfusion. As expected, no peak was detected in plasma from CAS patients (P = 0.003). Leukocyte-bound endotoxin appeared after blood reperfusion in 71% of the AAS patients, and circulating endotoxin was detected for 57% of them. The levels of interleukin (IL)-6, IL-10 and of inflammatory markers (C-reactive protein, procalcitonin) were maximal at postoperative day 1 or 2 in AAS patients. The levels of circulating NOD2 agonist positively correlated with those of cortisol and IL-10.

CONCLUSIONS

The measurement of circulating NOD2 agonist gives a higher informative tool than that of circulating endotoxin for early and sensitive detection of the translocation of bacterial products. The data suggest that circulating NOD2 agonist contributes to further enhance the stress response following surgery.

Retroperitoneal repair of abdominal aortic aneurysm reduces bowel dysfunction

OBJECTIVE

To assess the effect of intestinal manipulation and mesenteric traction on gastro-intestinal function and postoperative recovery in patients undergoing abdominal aortic aneurysm (AAA) repair.

METHODS

Thirty-five patients undergoing AAA repair were randomised into 3 groups. Group I (n = 11) had repair via retroperitoneal approach while Group II (n = 12) and Group III (n = 12) were repaired via transperitoneal approach with bowel packed within the peritoneal cavity or exteriorised in a bowel bag respectively. Gastric emptying was measured pre-operatively (day 0), day 1 and day 3 using paracetamol absorption test (PAT) and area under curve (P(AUC)) was calculated. Intestinal permeability was measured using the Lactulose-Mannitol test.

RESULTS

Aneurysm size, operation time and PAT (on day 0 and day 3) were similar in the three groups. On day 1, the P(AUC) was significantly higher in Group I, when compared with Group II and Group III (P = .02). Resumption of diet was also significantly earlier in Group I as compared to Group II and Group III. The intestinal permeability was significantly increased in Group II and Group III at day 1 when compared with day 0, with no significant increase in Group I. Retroperitoneal repair was also associated with significantly shorter intensive care unit (P = .04) and hospital stay (P = .047), when compared with the combined transperitoneal repair group (Group II and III).

CONCLUSION

Retroperitoneal AAA repair minimises intestinal dysfunction and may lead to quicker patient recovery when compared to transperitoneal repair.

The intestinal tract as the major source of interleukin 6 production during abdominal aortic clamping and hind limb ischaemia-reperfusion injury

PURPOSE

The aim of this study was to investigate whether the hind limbs or intestinal tract is the most important initiator of the inflammatory response secondary aortic clamping and hind limb ischemia/reperfusion injury.

METHODS

Blood samples of Wistar rats obtained from posterior cava vein, portal vein, and heart cavity during either laparotomy (control group, n=8) or laparotomy + 2 h of aortic clamping and bilateral hind limb ischemia (ischemia group, n=8), or 2 h after ischemia and 2 h of reperfusion (ischemia-reperfusion group, n=8) were assayed for interleukin 6 (IL-6) and C-reactive protein (CRP).

RESULTS

Serum IL-6 at the heart (223.6+/-197.9 [10-832] pg/mL) was higher (p<0.001) than at both portal (133.08+/-108.52 [4-372] pg/mL) and posterior cava veins (127.58+/-109.15 [8-388] pg/mL). CRP was not significant different among groups.

CONCLUSION

The splanchnic region is also a source of inflammatory response secondary to ischemia and reperfusion of the hind limbs.

Bacterial translocation as a source of Dacron-graft contamination in experimental aortic operation: the importance of controlling SIRS

BACKGROUND

Several experimental studies have shown the beneficial effects of nitric oxide (NO) in the modulation of the systemic inflammatory response syndrome (SIRS). Nitric oxide is involved in and affects almost all stages in the development of inflammation. We have attempted to ascertain whether the nitric oxide donor molsidomine prevents aortic graft contamination through control of the SIRS and a decrease in bacterial translocation (BT).

METHODS

Twenty-four mini-pigs were divided into 4 groups. The animals were subjected to suprarenal aortic/iliac cross-clamping (for 30 minutes) and by-pass with a Dacron-collagen prosthetic graft impregnated in rifampicin. Groups: 1) sham (aortic dissection alone); 2) cross-clamping and bypass; 3) hemorrhage of 40% of total blood volume before cross-clamping and by-pass; and 4) the same as in group 3 but also including the administration of the NO donor molsidomine (4 mg/kg) 5 minutes before cross-clamping.

VARIABLES

1) bacteriology of mesenteric lymph nodes (MLN), kidney, blood, and prosthesis; 2) serum TNF-alpha (ELISA); and 3) iNOS expression in kidney and liver (Western blot).

RESULTS

Aortic cross-clamping with or without hemorrhage was associated with BT in 80% and 100% of the animals, respectively. About 86% of the bacteria isolated in the graft were also present in MLN. This contamination coincided with an increase in TNF-alpha and with a greater expression of iNOS. Molsidomine administration decreased TNF-alpha and iNOS, decreased BT (from 100% to 20% of the animals), and decreased graft contamination (from 83% to 20%).

CONCLUSIONS

The present model induces high levels of BT and SIRS, both acted as sources of contamination for the implanted Dacron graft. Molsidomine administration decreased the presence of bacteria in the graft by controlling BT and modulating SIRS.

Ischaemia-Reperfusion Injury and Regional Inflammatory Responses in Abdominal Aortic Aneurysm Repair

OBJECTIVES

The inflammatory response to abdominal aortic aneurysm repair is likely to result in response to an ischaemia-reperfusion injury (IRI) to the lower-limbs and gastrointestinal tract. This paper reviews the pathogenesis of the inflammatory response to abdominal aortic aneurysm repair, with specific reference to the levels of evidence in the current literature regarding the potential origin of the inflammatory response.

DESIGN

Review article.

METHODS

The current literature (1966 to August 2003) was reviewed specifically for all articles employing techniques of regional blood sampling from the venous drainage of the lower limbs or gastrointestinal tract during abdominal aortic aneurysm repair.

RESULTS

Ten relevant studies were identified. These demonstrated that regional blood sampling techniques could be easily performed, and provided useful information regarding the potential sites of origin of the inflammatory response.

CONCLUSIONS

Regional blood sampling techniques provide useful information regarding the potential sites of origin of the inflammatory response. Current evidence suggests that both the lower limbs and gastrointestinal tract are clearly important in their roles, however more work is now required to compare directly the roles and contributions of the lower limbs and gastrointestinal tract to the inflammatory response during abdominal aortic aneurysm repair.

Selective inducible nitric oxide synthase (iNOS) inhibition attenuates remote acute lung injury in a model of ruptured abdominal aortic aneurysm

OBJECTIVE

Abdominal aortic aneurysm rupture is associated with a systemic inflammatory response syndrome and acute lung injury. Using a selective inducible nitric oxide synthase (iNOS) inhibitor, N(6)-(iminoethyl)-lysine (L-NIL), we explored the role of iNOS in the early pro-inflammatory signaling and acute lung injury in experimental abdominal aortic aneurysm rupture.

MATERIALS AND METHODS

Anesthetized rats were randomized to sham control or shock and clamp (s + c) groups, which underwent one hour of hemorrhagic shock, followed by 45 minutes of supramesenteric aortic clamping, and then two hours resuscitated reperfusion. Animals in s + c were randomized to receive intravenous L-NIL at 50 microg/kg/h or saline at the start of reperfusion. Pulmonary permeability to (125)I-labeled albumin, myeloperoxidase (MPO) activity, cytokine levels, and semi-quantitative RT-PCR for mRNA were indicators of microvascular permeability, leuco-sequestration, and pro-inflammatory signaling, respectively.

RESULTS

Lung permeability index were significantly increased in s + c compared to sham (4.43 +/- 0.96 versus 1.30 +/- 0.17, P < 0.01), and attenuated by L-NIL treatment (2.14 +/- 0.70, P < 0.05). Lung tissue MPO activity was significantly increased in s + c compared to sham (2.80 +/- 0.32 versus 1.03 +/- 0.29, P < 0.002), and attenuated by L-NIL treatment (1.50 +/- 0.20, P < 0.007). Lung tissue iNOS activity was significantly increased in s + c compared to sham animals (P < 0.05), and attenuated by L-NIL treatment (P < 0.05). Lung tissue iNOS mRNA was upregulated 8-fold in s + c compared to sham (P < 0.05). Data represents mean +/- standard error mean, comparisons with ANOVA.

CONCLUSIONS

These data suggest that in our model of ruptured abdominal aortic aneurysm iNOS plays a crucial role in reperfusion lung injury. Selective inhibition of iNOS during early reperfusion prevents neutrophil mediated acute lung injury.

Interleukin 6 production during abdominal aortic aneurysm repair arises from the gastrointestinal tract and not the legs

Background

Abdominal aortic aneurysm (AAA) repair is associated with a systemic inflammatory response. This inflammatory response probably arises as a result of an ischaemia–reperfusion injury to the legs and gastrointestinal tract. In this study the relative contributions of these areas to the inflammatory response were assessed during elective AAA repair.

Methods

Blood was sampled from the femoral vein, portal vein and radial artery of 14 patients undergoing elective AAA repair at five time points during the procedure. Plasma was snap-frozen for subsequent batch analysis of interleukin (IL) 6.

Results

The plasma IL-6 concentration rose steadily throughout the procedure at all three locations. The increase in plasma IL-6 was significantly greater in the portal vein than in the radial artery during ischaemia (P = 0·020). The plasma IL-6 concentration was also significantly higher in the portal vein than in the femoral vein (P &lt; 0·001) and radial artery (P &lt; 0·001) during reperfusion. There were no significant differences between radial artery and femoral vein IL-6 levels at any time point.

Conclusion

Ischaemia and reperfusion during AAA repair were associated with a marked increase in IL-6 concentration in the portal vein, suggesting that IL-6 was produced by the gastrointestinal tract.

Catecholamines potentiate LPS-induced expression of MMP-1 and MMP-9 in human monocytes and in the human monocytic cell line U937: possible implications for peri-operative plaque instability

Plaque destabilization leading to myocardial infarction is observed after surgery even if the intervention is of noncardiovascular nature. Mediators of peri- or postoperative stress responsible for such events could include catecholamines and lipopolysaccharide (LPS). Monocytes may be involved in destabilization of atherosclerotic plaques by production of matrix metalloproteinases (MMP). We examined whether catecholamines could affect the expression of MMPs in human monocytes/macrophages and whether catecholamines could modulate LPS-stimulated expression of particular MMPs in these cells. Epinephrine and norepinephrine up-regulated MMP-1 and potentiated LPS-induced expression of MMP-1 in peripheral blood monocytes and monocyte-derived macrophages. We further characterized this effect employing the monocytic cell line U937 and showed that catecholamines potentiate LPS-induced effects on MMP-1 and MMP-9 antigen and activity. mRNA levels of the respective MMPs also increased. These effects did not result from higher mRNA stability but rather from increased transcription possibly induced by enhanced DNA binding of AP-1 and were mediated by either beta1- or beta 2-receptors. If this mechanism is also effective in vivo, our findings might, at least in part, help to explain the observation that cardiac events are important causes of morbidity and mortality after noncardiac surgery and support the findings that peri-operative beta-blockade has been shown to reduce postoperative mortality from cardiac events.

Intestinal barrier: an interface between health and disease

The intestine constitutes the largest interface between a person and his or her environment, and an intact intestinal barrier is thus essential in maintaining health and preventing tissue injury and several diseases. The intestinal barrier has various immunological and non-immunological components. The epithelial barrier is one of the most important non-immunological components. Hyperpermeability of this barrier is believed to contribute to the pathogenesis of several gastrointestinal disorders including inflammatory bowel disease, celiac disease and food allergy. Hence, assessing barrier integrity is of the utmost importance. One of the more quantitative gauges for this assessment is transepithelial permeability of various molecular probes, among which sugars are commonly used. Measures of intestinal permeability might also be useful as markers for assessment of prognosis and follow up in various gastrointestinal disorders. The present article is a review of the normal and abnormal functioning of the intestinal barrier, the diseases that can result from loss of barrier integrity, and some promising agents and strategies for restoring barrier normality and integrity.

The effect of lower limb ischaemia-reperfusion on intestinal permeability and the systemic inflammatory response

OBJECTIVES

a relationship has been demonstrated between increased intestinal permeability, endotoxaemia and the development of the systemic inflammatory response syndrome (SIRS) after aortic surgery. The aim of this study was to evaluate whether isolated lower limb ischaemia-reperfusion (I/R) injury affects intestinal mucosal barrier function and cytokine release.

PATIENTS AND METHODS

four groups of patients were investigated, group I, patients with critical limb ischaemia (CLI) undergoing infra-inguinal bypass surgery (n=18); group II, patients with intermittent claudication (IC) undergoing infra-inguinal bypass surgery (n=14); group III, patients with CLI unsuitable for arterial reconstruction, undergoing major amputation (n=12); and group IV, patients undergoing carotid endarterectomy for symptomatic carotid stenosis (n=13). Intestinal permeability, endotoxaemia and urinary soluble tumour necrosis factor receptors were assessed (p55TNF-R).

RESULTS

an increase in intestinal permeability was observed on the 3rd postoperative day only in CLI group. This was found to correlate with arterial clamp time. Patients who had a femoro-distal bypass had significantly higher intestinal permeability compared to those who had femoro-popliteal bypass. Endotoxaemia was not detected in any of the groups. Postoperative urinary p55TNF-R concentrations were significantly higher in CLI group compared to the other groups. These did not correlate with the increased intestinal permeability.

CONCLUSIONS

our results support the hypothesis that revascularisation of critically ischaemia limbs leads to intestinal mucosal barrier dysfunction and cytokine release. They also suggest that the magnitude of the inflammatory response following I/R injury is related to the degree of initial ischaemia.

Oral antibiotic prophylaxis can influence the inflammatory response in aortic aneurysm repair: results of a randomized clinical study

The purpose of this prospective, randomized study was to evaluate the effect of oral ofloxacin prophylaxis on endotoxin/cytokine release in aortic aneurysm repair, in 25 patients with infrarenal aortic aneurysm at a University hospital. Outcome parameters included complications after operation; endotoxin and endotoxin neutralizing capacity, IL-6, procalciton and neopterin. All patients had the standard perioperative antibiotic prophylaxis (2 g cefotiam). 12 patients randomly received oral ofloxacin prophylaxis (group 1) the day before the operation (200 mg/2x12h); 13 patients were controls (group 2). Data were analyzed by chi-square analysis, Mann-Whitney and Wilcoxon analysis. Ofloxacin had no effect on the occurrence of complications or on the peripheral endotoxin levels. Ofloxacin-treated patients showed increased endotoxin neutralizing capacity (ENC) 30 min after clamping compared to controls (15.8+/-15 vs 262.8+/-709 p=0.005) and increased IL-6 levels preoperatively and 30 min after clamping. Patients with complications had significantly higher IL-6 levels early during the operation and postoperatively (30 min after clamping: 36.4+/-15.1 vs 18.8+/-11.9 pg/ml p=0.01; 2nd postoperative day: 768+/-688 vs 225+/-322 pg/ml p=0.005). Ofloxacin prophylaxis had no effect on procalcitonin, or neopterin plasma levels. Neither procalcitonin nor neopterin could detect patients with complications IL-6 plasma levels predicted the occurrence of complications in aortic aneurysm repair. Oral ofloxacin prophylaxis may influence the ENC and IL-6 plasma levels but had no effect on complications, endotoxin and other inflammatory mediators.

Cytokine activation and intestinal mucosal and renal dysfunction are reduced in endovascular AAA repair compared to surgery

PURPOSE

To compare endovascular (EVR) to open repair (OR) of abdominal aortic aneurysm (AAA) for cytokine activation, changes in the intestinal mucosal barrier, and renal dysfunction.

METHODS

In a prospective nonrandomized study, 15 patients admitted to a university hospital for elective infrarenal AAA repair (8 OR and 7 EVR) were recruited. Intestinal permeability was assessed preoperatively (PO), at day 1 (D1), and at day 3 (D3) after surgery using the lactulose/mannitol differential excretion (LMR) test. Renal damage was assessed from measurements of the urinary albumin:creatinine ratio (ACR); cytokine activation was based on the urinary concentration of tumor necrosis factor receptor p55 (TNF-Rp55) at the same time points. Serum creatinine and urea concentrations were measured preoperatively and daily for 5 days postoperatively.

RESULTS

A significant increase in LMR was found in the OR group at D1 and D3 compared to PO (p<0.05). The LMR increase at D3 was significantly greater in the OR group (p<0.01). A significant difference was observed in the percentage rise in ACR on D1 in the OR group compared to the EVR group (p<0.005). The urinary TNF-Rp55 concentration was significantly elevated in the OR group at D1 (p<0.05) and D3 (p<0.05) compared to baseline; in the EVR group, it was elevated at D1 (p<0.05) compared to PO. The difference was also significant for this marker between the 2 groups at D1 (p<0.01). No significant change was observed in the serum creatinine or urea concentrations in either group perioperatively.

CONCLUSIONS

Endovascular AAA repair is associated with less cytokine production and less intestinal and renal dysfunction compared to the open approach.

Inhibition of endotoxin response by e5564, a novel Toll-like receptor 4-directed endotoxin antagonist

Alpha-D-glucopyranose,3-O-decyl-2-deoxy-6-O-[2-deoxy-3-O-[(3R)-3-methoxydecyl]-6-O-methyl-2-[[(11Z)-1-oxo-11-octadecenyl]amino]-4-O-phosphono-beta-D-glucopyranosyl]-2-[(1,3-dioxotetradecyl)amino]-1-(dihydrogen phosphate), tetrasodium salt (E5564) is a second-generation synthetic lipodisaccharide designed to antagonize the toxic effects of endotoxin, a major immunostimulatory component of the outer cell membrane of Gram negative bacteria. In vitro, E5564 dose dependently (nanomolar concentrations) inhibited lipopolysaccharide (LPS)-mediated activation of primary cultures of human myeloid cells and mouse tissue culture macrophage cell lines as well as human or animal whole blood as measured by production of tumor necrosis factor-alpha and other cytokines. E5564 also blocked the ability of Gram negative bacteria to stimulate human cytokine production in whole blood. In vivo, E5564 blocked induction of LPS-induced cytokines and LPS or bacterial-induced lethality in primed mice. E5564 was devoid of agonistic activity when tested both in vitro and in vivo and has no antagonistic activity against Gram positive-mediated cellular activation at concentrations up to 1 microM. E5564 blocked LPS-mediated activation of nuclear factor-kappaB in toll-like receptor 4/MD-2-transfected cells. In a mouse macrophage cell line, activity of E5564 was independent of serum, suggesting that E5564 exerts its activity through the cell surface receptor(s) for LPS, without the need for serum LPS transfer proteins. Similar to (6-O-[2-deoxy-6-O-methyl-4-O-phosphono-3-O-[(R)-3-Z-dodec-5-endoyloxydecl]-2-[3-oxo-tetradecanoylamino]-beta-O-phosphono-alpha-D-glucopyranose tetrasodium salt (E5531), another lipid A-like antagonist, E5564 associates with plasma lipoproteins, causing low concentrations of E5564 to be quantitatively inactivated in a dose- and time-dependent manner. However, compared with E5531, E5564 is a more potent inhibitor of cytokine generation, and higher doses retain activity for durations likely sufficient to permit clinical application. These results indicate that E5564 is a potent antagonist of LPS and lacks agonistic activity in human and animal model systems, making it a potentially effective therapeutic agent for treatment of disease states caused by endotoxin.

Renal dysfunction after vascular surgery

PURPOSE OF REVIEW

The purpose of this review is to focus on the static incidence of renal dysfunction, the lack of evidence of benefit of traditional renoprotective strategies, and newer techniques that may provide an insight into the mechanisms of acute perioperative renal injury associated with vascular surgery.

RECENT FINDINGS

Recent studies that have investigated the long-term results of aortic surgery still report a significant incidence of postoperative renal dysfunction. This finding remains consistent in several reports. However, less invasive techniques such as endovascular repair seem to be associated with reduced inflammation and postoperative renal dysfunction. The possible association between genetic heterogeneity and renal dysfunction in vascular surgical patients is an exciting new area of research.

SUMMARY

Renal dysfunction after major vascular surgery remains a significant problem. New insights into the mechanisms of acute renal injury and less invasive techniques of vascular repair may help reduce the incidence of renal dysfunction in this patient population. The lack of a truly 'renoprotective' agent has hampered our efforts in preventing this major complication of vascular surgery.

Multi-antioxidant supplementation does not prevent an increase in gut permeability after lower torso ischemia and reperfusion in humans

BACKGROUND

An increase in gut permeability can have serious consequences leading to sepsis and multiple organ failure. After lower torso ischemia an increase in gut permeability is seen in both animals and humans. There is proof that this can be modified by antioxidant supplementation.

METHODS

In this prospective, randomized study we have looked at the influence of a multiantioxidant supplementation regime, using allopurinol, vitamins E and C, mannitol and N-acetylcysteine, perioperatively. Twenty-two patients received standard treatment and 20 patients received supplementation. Gut permeability was determined using a double sugar test with lactulose and rhamnose.

RESULTS

A significant increase in gut permeability was found neither in the non-treatment group (p = 0.012) nor in the treatment group (p = 0.006) after 6 and 24 h. No difference was found between the group receiving antioxidants and the standard treatment group. p = 0.93 6 h post clamp; p = 0.97 24 h post clamp.

CONCLUSION

In this study we have not found an influence of multiantioxidant supplementation on gut permeability after lower torso ischemia. Possible explanations for this negative result are being discussed.

Cytokines and inflammatory pathways in the pathogenesis of multiple organ failure following abdominal aortic aneurysm repair

Multiple organ failure is a common mode of death following abdominal aortic aneurysm repair, particularly after rupture. Cytokines are the principal mediators of the inflammatory response to injury and high levels of circulating cytokines have been associated with poor outcome in major trauma and sepsis. Abdominal aortic aneurysm repair results in an ischaemia-reperfusion injury to the tissues distal to the site of aortic clamping. The inflammatory response in these tissues causes the release of cytokines, principally Interleukins 1-beta, 6, and 8, and Tumour Necrosis Factor alpha. If released in large enough concentrations, these cytokines may enter the circulation and gain access to organs distant to the site of initial injury. Circulating cytokines cause dysfunction of the renal, cardiovascular, respiratory, nervous and musculo-skeletal systems. The combination of these individual changes in organ function is the multiple-organ dysfunction syndrome, which may progress to multiple organ failure.

The Inflammatory Response and its Consequence for the Clinical Outcome Following Aortic Aneurysm Repair

OBJECTIVE

to review published studies on the outcome of the inflammatory response after abdominal aortic aneurysm (AAA) repair.

METHODS

a literature search on PubMed was performed. All studies that determined the inflammatory response (cytokine release) after AAA repair were included. The results of the studies and differences between open and endoluminal repair were compared and evaluated.

RESULTS

seventeen studies were identified. In most studies the investigated cytokines were TNF-alpha and IL-6. Determination of IL-1 beta, IL-8, TNFsr1 and TNFsr2 were less often performed. TNF-alpha may reflect, but not strictly predict, the clinical outcome in patients with ruptured AAA. IL-6 levels correlate well with the surgical trauma per se. Variations in recorded cytokine release during endovascular AAA repair may depend on the times of blood sampling.

CONCLUSION

both open and endovascular AAA repair provoke a cytokine response. This response is greater during open repair than during endovascular aortic aneurysm exclusion.

Extraperitoneal Approach Reduces Neutrophil Activation, Systemic Inflammatory Response and Organ Dysfunctionin Aortic Aneurysm Surgery

OBJECTIVES

to compare the effects of transperitoneal and extraperitoneal approaches on systemic inflammatory response, neutrophil activation and organ dysfunction in elective abdominal aortic aneurysm (AAA) repair.

PATIENTS AND METHODS

twenty patients admitted for elective infrarenal AAA repair were prospectively randomised into transperitoneal (n =10) or extraperitoneal ( n =10) groups. Neutrophil activation was assessed by measuring the plasma levels of neutrophil elastase/alpha(1)-anti-trypsin complexes before surgery, intraoperatively and at 6 h, 12 h, 24 h and then daily after surgery. Venous blood samples for estimation of liver function tests, full blood counts, urea and electrolytes and arterial samples for blood gas analysis were taken daily from preoperatively to day 5 after surgery. Multiple organ dysfunction (MOD) and systemic inflammatory response (SIR) scores were calculated daily.

RESULTS

the concentrations of neutrophil elastase/alpha(1)-anti-trypsin complexes were significantly higher in the transperitoneal group at 6 h after surgery compared to the extraperitoneal group (799(455-921) ng/ml (median(i.q.r.)) vs 307(171-395) ng/ml, p<0.005), and at 12 h (397(364-936) ng/ml vs 319(134-352) ng/ml, p <0.05). The MOD scores were significantly higher in the transperitoneal group in comparison to the extraperitoneal group at day 1 (2.5(2-3.3) vs 1(0-1), p<0.001) and day 2 (2.5(2-3.3) vs 1(0-1), p <0.001). The SIR scores were also significantly higher at day 1 (1(0-2) vs 0, p <0.01), day 2 (1.5(0-2.3) vs 0, p <0.01), and day 3 (1(0-1) vs 0, p <0.05).

CONCLUSIONS

neutrophil activation, systemic inflammatory response and organ dysfunction are increased in elective AAA repair when a transperitoneal approach is used. This may be related to intestinal manipulation and mesenteric traction which are reduced in the extraperitoneal approach.