Treatment of necrotizing pancreatitis: redefining the role of surgery.

BACKGROUND: Early surgical intervention in necrotizing pancreatitis (NP) is associated with high mortality. Guidelines recommend fine needle aspiration (FNA) in patients with NP and signs of sepsis. Because infection of necrosis is considered an indication for surgery, operations are often performed early. We changed treatment toward a conservative approach with FNA in selected cases only, thereby reducing the rate of necrosectomy. METHODS: Retrospectively analyzed patients, all operated on for FNA-proven infection of pancreatic necrosis (n = 20, group 1) were compared to patients subjected to conservative treatment (n = 24, group 2) who were followed prospectively. RESULTS: Prognostic scores did not differ between the two groups, indicating comparable severity: the Acute Physiology and Chronic Health Evaluation (APACHE II) score was 19.8 ± 1.7 versus 16 ± 2.2; the Sequential Organ Failure Assessment (SOFA) score was 8.7 ± 1.4 versus 6.9 ± 1.0, the C-reactive protein (CRP) level on day 3 was 243 ± 21 versus 291 ± 21, and the CTSI (CT severity index) was 7.8 ± 0.5 versus 7.9 ± 0.4 (p = ns). Ten patients in group 2 underwent operation because of severe extrapancreatic complications. Mortality differed significantly (45% in group 1 vs. 8.3% in group 2; p = 0.01). CONCLUSIONS: A highly conservative approach avoiding open necrosectomy in NP results in significantly lower mortality than previous serial FNA and consecutive indication for surgery in case of proven infection. Open surgery in NP should be reserved for concomitant intra-abdominal complications.

Intensified irinotecan-based neoadjuvant chemoradiotherapy in rectal cancer: four consecutive designed studies to minimize acute toxicity and to optimize efficacy measured by pathologic complete response.

BACKGROUND: The objective of the present study was to analyse toxicity and efficacy of irinotecan-based neoadjuvant chemoradiotherapy by the help of four consecutively planed and prospectively performed phase II studies. PATIENTS AND METHODS: Patients with locally advanced rectal cancer received radiotherapy and concurrently chemotherapy consisting 5-Fu/capecitabine in a continuous or intermittent application and irinotecan in two different total doses (240 vs. 200 mg/m(2)). RESULTS: Diarrhea CTC grade III was seen in 35% in continuous application of 5-Fu/capecitabine versus 12.5% in intermittent application (p= 0,008). Complete response according to the irinotecan dose during chemoradiotherapy (240 mg/m(2) vs. 200 mg/m(2)) was 24% and 0%. CONCLUSIONS: Chemoradiotherapy of the last phase II study with intermittent capecitabine (1500 mg/m(2)/day, delivered on days 1-14 and 22-35) and irinotecan (4 x 60 mg/m(2)) concurrently to radiotherapy is a safe treatment with low toxicity and high efficacy.

Effects of octreotide in acute hemorrhagic necrotizing pancreatitis in rats.

BACKGROUND AND AIM: Octreotide is considered to reduce exocrine pancreatic secretion in acute hemorrhagic necrotizing pancreatitis decreasing pancreatic autodigestion. The aim of this study was to determine whether octreotide also has antioxidative effects in acute pancreatitis. Additionally time and dose of application were of interest. METHOD: Ninety male Sprague-Dawley rats were randomized into six groups (n = 15). Group 1 underwent a laparotomy, and animals in groups 2-6 received intraductal glycodeoxycholic acid followed by intravenous cerulein. Groups 3 and 4 were injected with 0.5 mg octreotide, while groups 5 and 6 received continuous intravenous infusion of 0.05 mg octreotide/h for 10 h. Treatment was initiated 6 hours after induction of pancreatitis (IP) in groups 3 and 5, and 14 h after IP in groups 4 and 6. At 24 h after IP all animals were killed and each pancreas was analyzed histopathologically. In addition, levels of pancreatic lipid peroxidation protective enzymes glutathione-peroxidase (GSH-Px) and superoxide dismutase (SOD) as well as lipid peroxidation via thiobarbituric acid reactive substances (TBARS) were determined. RESULTS: Early bolus application of octreotide reduced severity of histopathological changes in acute pancreatitis and decreased lipid peroxidation in pancreatic tissue samples; however, late bolus application and continuous intravenous infusion did not influence pancreatitis or lipid peroxidation. CONCLUSION: Octreotide seems to have a dose- and time-dependent effect on histopathology and lipid peroxidation in a model of pancreatitis in rats.

Effect of neoadjuvant chemoradiation on postoperative fecal continence and anal sphincter function in rectal cancer patients.

BACKGROUND AND AIMS: Neoadjuvant chemoradiation (nCRT) followed by curative surgery has gained acceptance as the therapy of choice in locally advanced rectal cancer. This prospective study evaluates the effect of nCRT on postoperative anorectal function and continence. PATIENTS AND METHODS: Group A consisted of 12 patients (59.8 +/- 11.9 years, male:female = 8:4) who received nCRT (5-FU, CPT-11. 45 + 5.4 Gy boost) before surgery and Group B of 27 patients (61.9 +/- 10.6 years, male:female = 16:11) who were treated by surgery alone. All patients received a questionnaire to evaluate stool continence and anorectal function before as well as after surgery. Anorectal function was further analyzed by perfusion manometry pre- and postoperatively. RESULTS: Preoperatively, none of the patients had signs or symptoms of fecal incontinence, and preoperative measurements showed values within normal limits. Postoperatively, fecal continence was impaired in both groups, but no significant difference was found between patients with or without nCRT. Anorectal manometry revealed an impairment of anorectal function after low anterior resection regardless of the treatment regime. CONCLUSION: nCRT does not impair anorectal function and fecal continence. The deterioration of continence and anal sphincter function after sphincter preserving surgery is solely caused by the surgical procedure.

VEGF antisense therapy inhibits tumor growth and improves survival in experimental pancreatic cancer.

BACKGROUND: Vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, is overexpressed in pancreatic cancer. This study evaluated VEGF production in pancreatic cancer cells and the effect of VEGF antisense on growth and angiogenesis of human pancreatic cancer in a nude mouse model. METHODS: In vitro: VEGF in cell culture supernatant of pancreatic cancer cells (AsPC-1, poorly differentiated; HPAF-2, moderately differentiated) was assessed by enzyme-linked immunosorbent assay. In vivo: A VEGF antisense oligonucleotide (AS-3) was synthesized. One-mm(3) fragments of subcutaneous pancreatic cancer donor tumors were implanted into the pancreas of nude mice also receiving AS-3 (10 mg/kg/day) or vehicle intraperitoneally for 14 weeks. Primary tumor volume, metastasis, and VEGF in plasma and ascites were determined at autopsy. Microvessel density was analyzed in CD31-stained tumors. RESULTS: In vitro: Both pancreatic cancer cell lines secreted VEGF protein (AsPC-1, 4200 +/- 40 pg/10(6) cells; HPAF-2, 8120 +/- 60 pg/10(6) cells). In vivo: AS-3 reduced tumor volume in the HPAF-2 group (860 +/- 140 vs 3830 +/- 590 mm(3)) and metastatic spread in both groups (AsPC-1, 6.5 +/- 0.8 vs 16.7 +/- 0.9 points; HPAF-2, 2.5 +/- 0.2 vs 8.3 +/- 1.5 points). Tumor volume was not different in the AsPC-1 group (1050 +/- 80 vs 1400 +/- 150 mm(3)). Survival was increased in the AsPC-1 group. Plasma levels of VEGF and microvessel density in tumors were significantly reduced in treated animals. Only control animals (50%) developed ascites with high VEGF concentrations. CONCLUSIONS: Human pancreatic cancer cells secrete VEGF at biologically relevant high levels. AS-3 therapy normalizes plasma VEGF and decreases neoangiogenesis, thereby reducing tumor growth and metastasis and improving survival. AS-3-treated animals developed no ascites, suggesting decreased vascular permeability by reducing VEGF expression in pancreatic cancer cells.

Neoadjuvant radiochemotherapy in locally advanced gastric carcinoma.

BACKGROUND AND PURPOSE: Gastric carcinoma is characterized by a high rate of local recurrences and distant metastases and is often not resectable due to locally advanced stage. The aim of this study was to examine feasibility and effectiveness of neoadjuvant radiochemotherapy (RCT) for locally advanced, primarily nonresectable gastric carcinoma and to achieve curative resection. PATIENTS AND METHODS: 21 patients with locally advanced gastric cancer located in cardia (n = 17) and corpus (n = 4; seven cT3; 14 cT4; 18 cN+; all cM0) with a median age of 61 years were scheduled to receive neoadjuvant RCT. Therapy consisted of a conventionally fractionated, conformal radiotherapy using the shrinking-field technique (1.8 Gy to 45 Gy + 5.4 Gy) and chemotherapy using cisplatin (20 mg/m(2), d1-5, 29-33), 5-fluorouracil (5-FU; 800 mg/m(2), d1-5, 29-33) or paclitaxel (135 mg/m(2), d1, 29). 4-6 weeks after completion of RCT, surgery was performed whenever feasible. RESULTS: Hematologic toxicity was moderate with grade 3 leukopenia in 10/21 patients and grade 3 thrombopenia in 5/21 (CTC). Nonhematologic toxicities consisted of 5/21 cases of fever as well as one fungal sepsis. Following RCT, tumors were classified resectable in 16/21 patients (76%); 12/21 patients (58%) were operated on, 11/12 achieved clear margins (R0). Response was as follows: complete remission (CR) 3/21 (14%), partial remission 13/21 (62%), no change 3/21 (14%), systemic progressive disease (PD) 2/21 (10%). The median survival and the 2-year survival rates were 18 months and 42%, respectively, for the patients following R0 resections as compared to 10 months and 0% for the remaining patients (p = 0.035). Local control (4 years) for patients following R0 resection was 89%. CONCLUSION: Neoadjuvant RCT is feasible and locally highly effective but must be further investigated involving a higher number of patients.

Selective inhibition of cyclooxygenase-2 (COX-2) reduces prostaglandin E2 production and attenuates systemic disease sequelae in experimental pancreatitis.

BACKGROUND/AIMS: Prostaglandins and prostaglandin-derived mediators play an important role in mediating the systemic inflammatory response in acute pancreatitis. COX (cyclooxygenase) is the key enzyme of prostaglandin synthesis. Whereas COX-1 produces prostaglandin mediators for physiological reactions, COX-2 is overexpressed in acute pancreatitis. The aim of this study was to investigate whether a selective COX-2 inhibitor alters prostaglandin production and attenuates systemic disease sequelae in severe acute pancreatitis in rats. METHODOLOGY: Severe acute pancreatitis was induced in 36 rats by standardized intraductal infusion of bile salt and intravenous cerulein infusion. Six hours after acute pancreatitis induction, rats were randomized to receive either no COX inhibition (saline), nonselective COX inhibition by indomethacin (3 mg/kg, i.v.) or selective COX-2 inhibition by NS-398 (10 mg/kg, i.v.). Serum concentrations of prostaglandin E2 were measured before and after acute pancreatitis induction and 24 hrs after starting therapy. Routine cardiorespiratory and renal parameters were monitored to assess organ function. RESULTS: Animals treated with the selective COX-2 inhibitor had significantly lower prostaglandin E2 values (211 +/- 17 vs. 366 +/- 37 and 435 +/- 13 pg/mL), produced more urine (18 +/- 4 vs. 13 +/- 3 and 12 +/- 3 mL/6-24 h) and had significantly fewer episodes of respiratory distress (defined as a pO2 < 80 mmHg or pCO2 > 50 mmHg for > 15 min; 12 vs. 57 and 71%) during the observation period than animals without or with nonselective COX inhibition. CONCLUSIONS: Selective inhibition of COX-2 reduces prostaglandin E2 serum levels in this model of acute pancreatitis. This together with improved renal and respiratory function suggests an attenuation of the systemic response to pancreatic injury. COX-2 inhibition may be another step toward optimizing therapy in severe acute pancreatitis.

An orthotopic nude mouse model for evaluating pathophysiology and therapy of pancreatic cancer.

INTRODUCTION: Orthotopic, clinically relevant animal models are necessary for the study of pathophysiology and therapy for pancreatic cancer. AIMS: To develop a minimally traumatic technique of orthotopic tumor induction, to develop a scoring system to quantify local and systemic tumor spread, and to provide a model with a broad range of well-differentiated to undifferentiated pancreatic cancers. METHODOLOGY: Orthotopic tumors were induced in nude mice by atraumatic pancreatic implantation of two fragments from subcutaneous donor tumors or intrapancreatic injection of human tumor cells (MIAPaCa-2, AsPC-1, HPAF-2, Capan-1). Animals were monitored for 14 weeks or until death. Primary tumor volume, local infiltration, and systemic metastasis were assessed and analyzed at autopsy. Macroscopic findings were confirmed by histologic evaluation. RESULTS: Tumor take rate in the implantation group was 100% for all four cell lines. Marked differences with regard to tumor size, metastatic spread, and survival were found depending on the grade of differentiation. Less differentiated cells (MIAPaCa-2, AsPC-1) caused higher dissemination scores and mortality than better-differentiated cells (HPAF-2, Capan-1). Clinical features included cachexia, jaundice, and malignant ascites. Orthotopic tumor cell injection resulted in an incomplete tumor take rate. Moreover, early artificial abdominal tumor spread was found in injected animals due to microscopic cell loss during the injection procedure. CONCLUSIONS: Orthotopic implantation of donor tumor fragments into nude mice is technically feasible and is superior to the cell injection technique. It results in reproducible local and systemic development of pancreatic cancer that mimics the human disease. A dissemination score may help to better quantify therapeutic effects in future studies.

Evaluation of vascular endothelial growth factor blockade and matrix metalloproteinase inhibition as a combination therapy for experimental human pancreatic cancer.

Blockade of vascular endothelial growth factor (VEGF) and inhibition of matrix metalloproteinases (MMP) are promising therapies for cancer. This study assessed the effects of a neutralizing anti-VEGF antibody (A4.6.1) and an MMP inhibitor (BB-94) on pancreatic cancer (PaCa) in vivo. Five million cells of two human PaCa cell lines (AsPC-1 and HPAF-2) were injected subcutaneously into nude mice; 1 mm(3) fragments of the resulting tumors were implanted into the pancreas of other mice. Animals were randomized into a control group and three treatment groups: A4.6.1 (100 microg intraperitoneally twice weekly); BB-94 (50 mg/kg every other day); and combination (A4.6.1 plus BB-94). Treatment was started after 3 days and continued for 14 weeks. Tumor volume, local and distant spread (score), and ascites were determined at autopsy. Microvessel density as a parameter of neoangiogenesis was analyzed in CD31-stained tumor sections. Both monotherapies reduced tumor volume (HPAF-2: -89% by A4.6.1 and -75% by BB-94; AsPC-1: -48% by A4.6.1 and -72% by BB-94), spread (HPAF-2: -76% by A4.6.1 and -58% by BB-94; AsPC-1: -32% by A4.6.1 and -54% by BB-94), and microvessel density (HPAF-2: -75% by A4.6.1 and -30% by BB-94; AsPC-1: -59% by A4.6.1 and -30% by BB-94), resulting in a tendency toward increased survival (HPAF-2: 8 of 8 animals by A4.6.1 or BB-94 vs. 4 of 8; AsPC-1: 3 of 8 by A4.6.1, 4 of 8 by BB-94 vs. 1 of 8). Combination therapy yielded additional effects in the HPAF-2 group with regard to tumor volume (-95%) and development of ascites (0 of 8 vs. 2 of 8 by A4.6.1 or BB-94 vs. 5 of 8 control mice). Both VEGF blockade and MMP inhibition reduce primary tumor size, metastasis, and angiogenesis, thereby increasing survival in experimental pancreatic cancer. Combination treatment results in additive effects in moderately differentiated HPAF-2 tumors.

Omega-3 fatty acid supplementation increases anti-inflammatory cytokines and attenuates systemic disease sequelae in experimental pancreatitis.

BACKGROUND: The cytokines involved in the systemic inflammatory response in acute pancreatitis (AP) comprise lipid mediators (eg, prostanoids, thromboxanes, leukotrienes) generated from arachidonic acid (AA) and eicosapentaenoic acid (EPA). The AA-derived mediators are generated from omega-6-fatty acid (FA) and have strong proinflammatory effects and the EPA-derived mediators generated from omega-3-fatty acid are less active or even exhibit anti-inflammatory effects. Basic parenteral nutrition delivers omega-6-FA and omega-3-FA at a ratio of approximately 7:1. AIM: To investigate whether altering the FA composition by fish oil supplementation (omega-3-FA) affects cytokine production and the parameters reflecting systemic disease severity in experimental AP. METHODS: Severe AP was induced in 30 rats by standardized intraductal infusion of bile salt and IV cerulein. Six hours after AP induction, rats were randomized to TPN using commercial solutions with identical amounts of glucose, amino acids, and fat but different FA compositions: group 1 received a soybean-based fat solution without additional fish oil and group 2 was supplemented with 0.2 g/kg per day fish oil. TPN was continued for 2 days. Serum concentrations of IL-6 and IL-10 were measured before and after AP induction and at 24 and 48 hours after starting TPN. Routine cardiorespiratory and renal parameters were monitored to assess the systemic response at the organ level. RESULTS: Animals treated with fish oil had significantly higher IL-10 values (at 24 hours, 63 +/- 7 versus 46 +/- 3 pg/mL), produced more urine (28 +/- 0.9 versus 21 +/- 1.6 mL), and had significantly fewer episodes of respiratory dysfunction (defined as a pO2 < 80 mm Hg or pCO2 > 50 mm Hg for >15 minutes; 29% versus 67%) during the observation period. CONCLUSIONS: Altering eicosanoid mediator precursor availability by infusion of (omega-3 fatty acid increases anti-inflammatory cytokines in this model of AP. This together with improved renal and respiratory function suggests that the systemic response to pancreatic injury is attenuated.

Chemoembolization of the lung improves tumor control in a rat model.

PURPOSE: The novel method of organ-specific drug application we present here is unilateral chemoembolization of the lung by injecting the pulmonary artery with degradable starch microspheres and cytotoxic drugs to improve tumor control in lung metastases. EXPERIMENTAL DESIGN: In a solitary metastasis rat model (CC531 adenocarcinoma), we studied the clinical and histological tumor response as well as subacute toxicity of the lung. Fourteen days after tumor induction, animals were randomized into five groups. Groups I and II served as controls. Group III received carboplatin i.v. (45 mg/kg). Isolated lung perfusion with buffered starch solution and carboplatin (15 mg/kg) was installed in group IV. Chemoembolization with carboplatin (15 mg/kg) was performed in group V. RESULTS: Seven days later, the difference in the tumor volume before and after treatment was +422 mm(3) (+/-226) in group I, +697 mm(3) (+/-423) in group II, +70 mm(3) (+/-31) in group III, -8 mm(3) (+/-17) in group IV, and -17 mm(3) (+/-16) in group V (P < 0.05 groups IV and V versus groups I, II, and III). No pleural spread was observed in groups IV and V. Histologically, the area of tumor necrosis was largest in group IV. Mild alveolar cell hyperplasia, pulmonary edema, and hemorrhage without subacute fibrotic changes were noted in all groups. CONCLUSION: This is the first study to perform chemoembolization of the lung. Compared with i.v. therapy, chemoembolization was more effective without serious toxicity. Its efficacy was comparable with that of isolated lung perfusion but less stressful for a possible clinical application.

Endothelin A but not endothelin B receptor blockade reduces capillary permeability in severe experimental pancreatitis.

INTRODUCTION: Microcirculatory disorders, in particular increased capillary permeability (CapPerm), contribute to the multiple organ dysfunction syndrome in severe acute pancreatitis (AP). Endothelin receptor antagonists (ET-RA) have been shown to stabilize capillary leakage and improve organ function in AP. AIM: To find out which endothelin receptor subtype (ET-A or ET-B) mediates the changes in CapPerm. METHODOLOGY: Severe AP was induced in rats by intraductal bile salt infusion and i.v. cerulein. Animals were randomized to receive (1) saline; (2) selective ET-A-RA (LU-135252; 30 mg/kg); (3) selective ET-B-RA (A-192621); (4) nonselective ET-RA (LU-135252; 120 mg/kg); or (5) combined ET-A/B-RA (30 mg/kg LU-135252 + A-192621). Capillary blood flow (CBF) and CapPerm in the pancreas and colon and leukocyte rolling in mesenteric venules were determined. RESULTS: Selective ET-A-RA increased CBF and decreased CapPerm in the pancreas and colon by 90-147% and reduced leukocyte rolling in AP but had no effect in healthy controls. Selective ET-B-RA increased pancreatic CBF (2.3 +/- 0.03 versus 2.1 +/- 0.04 nL/min) and enhanced CapPerm in the pancreas and colon by 24-35% in healthy controls but had no effect in AP. Blockade of both receptors produced effects similar to but less pronounced than those of selective ET-A-RA. CONCLUSIONS: Blockade of ET-A and ET-B receptors has different effects on CapPerm in healthy animals and those with AP. This may explain the inconclusive results reported with nonselective ET-RA. In severe AP, blockade of ET-A but not ET-B receptors reduces CapPerm.

Reduction in mortality with delayed surgical therapy of severe pancreatitis.

The indications for surgery in acute pancreatitis have changed significantly in the past two decades. Medical charts of patients with acute pancreatitis treated at our institution were analyzed to assess the effects of changes in surgical treatment on patient outcomes. A total of 136 patients with radiologically defined severe pancreatitis were primarily treated or referred to our institution between 1980 and 1997. Severity of the disease (Ranson score), indications for surgical intervention, timing of surgery, and mortality rates were compared during three study periods: 1980 to 1985 (period I), 1986 to 1990 (period II), and 1991 to 1997 (period III). In period I patients underwent exploratory laparotomy if their clinical status did not improve markedly within 72 hours of admission to the hospital, whereas during period II surgery was reserved for patients who had secondary organ failure together with pancreatic necrosis seen on CT scan. During period III the aim was to operate as late as possible in the presence of pancreatic necrosis or when infected necrosis was suspected. The policy of limiting the indications for surgery resulted in a decrease in surgically treated patients from 68% to 33% (P < 0.001). Likewise, surgical intervention was performed later. In period I, 73% of operations were performed within 72 hours of admission, compared to 32% in period III (P = 0.008). The mortality rate for patients who underwent early surgery (within 72 hours) was higher than for those who underwent late surgical exploration of the abdomen (P = 0.02). Overall, the mortality rate for patients with severe pancreatitis was reduced from 39% to 12% (P = 0.003). Mortality among patients treated nonoperatively did not change significantly. The present study supports the policy of delayed surgery in severe acute pancreatitis. Early surgical intervention often results in unnecessary procedures with an increase in the number of deaths. Whenever possible, prolonged observation allows selection of patients who are likely to benefit from delayed surgery or nonoperative treatment.

Specific targeting of tumor vasculature by diphtheria toxin-vascular endothelial growth factor fusion protein reduces angiogenesis and growth of pancreatic cancer.

Tumor vessels abundantly express receptors for vascular endothelial growth factor (VEGF), a mediator of neoangiogenesis. The aim of this study was to specifically target and damage the vasculature of pancreatic cancer (PaCa) by fusing VEGF to diphtheria toxin (DT), which inhibits protein synthesis of target cells. DT-VEGF fusion protein was produced in vector pGEX-KG and expressed in E. coli SG12036. Human PaCa cell lines (HPAF-2 and AsPC-1) and human endothelial cells (HUVEC) were exposed to DT-VEGF (10 ng/ml - 10,000 ng/ml). Proliferation was assessed after 3 days. One mm(3) fragments of subcutaneous PaCa donor tumors were implanted into the pancreas of nude mice that received either DT-VEGF (200 microg/kg, every other day) or phosphate-buffered saline intraperitoneally for 14 weeks. Tumor volume, metastatic spread, and animal weight were determined at autopsy. Microvessel density was analyzed in CD31-stained tumor sections. Proliferation of PaCa cells was inhibited at high concentrations of DT-VEGF (>1000 ng/ml). DT-VEGF decreased the growth of HUVEC at 10 ng/ml. In vivo, DT-VEGF reduced tumor volume (HPAF-2, 76%; AsPC-1, 53%), microvessel density (HPAF-2, 54%; AsPC-1, 62%), and tumor spread (HPAF-2, 89%; AsPC-1, 50%). Survival was increased (HPAF-2, 7/8 vs. 4/8 animals; AsPC-1, 6/8 vs. 1/8 animals). Weight was not influenced by DT-VEGF. The DT-VEGF effect is due to its toxic action on the tumor vasculature rather than to direct inhibition of PaCa cell growth. DT-VEGF therapy was not associated with systemic side effects.

Therapy of microcirculatory disorders in severe acute pancreatitis: what mediators should we block?

OBJECTIVE: To compare the effect of different vasoactive mediator antagonists in the same model of severe acute pancreatitis (AP) and to evaluate whether combinations of the agents exhibit synergistic effects. DESIGN: Prospective experimental study. SETTING: Microcirculation and pancreas research laboratory at an university hospital. PARTICIPANTS: Hundred eighty anesthetized male Sprague-Dawley rats. INTERVENTIONS: Six hours after inducing AP by intra-ductal bile salt infusion and i.v. cerulein in 168 rats, these were randomized for therapy with (1) saline, (2) endothelin receptor antagonist (ET-RA), (3) platelet activating factor receptor antagonist (PAF-RA), (4) intercellular adhesion molecule-1 antibody (ICAM-1-AB) or different combinations (5-7). After 24 h the animals underwent a second laparotomy for intra-vital microscopic determination of pancreatic and colonic capillary permeability, blood flow and leukocyte-endothelial interaction. RESULTS: AP induction decreased capillary blood flow and increased permeability and leukocyte rolling. ET-RA, PAF-RA and ICAM-1-AB decreased capillary permeability, increased blood flow and reduced leukocyte rolling. ET-RA was most effective in decreasing capillary permeability in both organs as well as in increasing pancreatic capillary blood flow. Combining vasoactive mediator blockers did not further improve target parameters. CONCLUSIONS: This study supports previous observations that ET-RA, PAF-RA and ICAM-1-AB improve microcirculation in AP and that ET-RA is more effective than PAF-RA or ICAM-1-AB, especially in counteracting capillary leakage. Although this may suggest that they act through different mechanisms, antagonist combinations failed to improve microcirculation further. We conclude that ET-RA is the most promising candidate for a clinical trial to reduce capillary leakage in patients with AP.