Intravenous N-acetylcysteine does not prevent post-ERCP pancreatitis

BACKGROUND

Acute pancreatitis remains the most common complication of ERCP. Prophylactic administration of N-acetylcysteine (NAC) probably decreases the incidence and the severity of experimental pancreatitis. The aim of the present study was to assess the efficacy of intravenous NAC for prevention of post-ERCP pancreatitis in humans, who represent an appropriate model to study the potential role of NAC in this setting.

METHODS

A prospective, double-blind, placebo-controlled trial was conducted in 256 patients who underwent ERCP. Patients were randomized to receive intravenous NAC at a loading dose of 70 mg/kg 2 hours before and 35 mg/kg at 4-hour intervals for a total of 24 hours after the procedure, or to receive normal saline solution as placebo. Patients were clinically evaluated, and serum amylase levels were measured before and 6 hours and 24 hours after the procedure. Standardized criteria were used to diagnose and to grade the severity of post-ERCP pancreatitis.

RESULTS

A total of 249 patients were included in the analysis. The two groups were matched for age, gender, underlying disease and indication for treatment, ERCP findings, and type of treatment. The overall incidence of post-ERCP acute pancreatitis was 10.8%, with 12.1% in the NAC group and 9.6% in the placebo group. There were no statistical differences in the incidence or severity grades between the groups. The mean duration of hospitalization for pancreatitis also was similar in the NAC group and the placebo group (3.6 +/- 0.9 and 3 +/- 1.5 days, respectively).

CONCLUSIONS

The results of this trial show the absence of any beneficial effect of NAC on the incidence and the severity of ERCP-induced pancreatitis.

[Antibiotic prophylaxis in acute pancreatitis--is the evidence good enough?]

BACKGROUND

Randomized controlled trials on acute necrotizing pancreatitis suggest that prophylactic antibiotics can reduce mortality and morbidity in these patients by preventing pancreatic infections.

MATERIAL AND METHOD

Relevant articles were assessed using a clinical appraisal skills programme.

RESULTS

Eight trials have been published since 1990. The early trials showed that prophylactic antibiotics did reduce mortality and morbidity; however, errors of methodology weaken these results. In later trials results have varied: in September 2004, Isenmann et al. published a trial with a greatly improved design and found no effect of prophylactic antibiotics compared to antibiotic treatment on demand.

INTERPRETATION

Based on the results obtained so far, the evidence is not yet strong enough to recommend prophylactic antibiotics in acute necrotizing pancreatitis. There is still a need for a new, larger, multicentre study that pays careful attention to all aspects of the condition, for instance diagnosis and treatment of abdominal compartment syndrome, and guidelines for method and time of surgery.

[Continuous regional arterial infusion of protease inhibitor and antibiotic for severe acute pancreatitis]

Continuous regional arterial infusion (CRAI) of protease inhibitor and antibiotic has been established as an initial treatment for severe acute pancreatitis in Japan. CRAI therapy reduced the mortality rate and the frequency of infected pancreatic necrosis. Recently vasospasm has been recognized to be involved in the development of pancreatic ischemia or hypoperfusion in the early phase of the disease, and early application of CRAI of nafamostat may protect the evolution of ischemia into necrosis by inhibition of the increase in the intravascular coagulant activity.

Effects of octreotide on acute necrotizing pancreatitis in rabbits

AIM: To assess the role of oxygen-derived free radicals and cytokines in the pathogenesis of taurocholic acid-induced acute pancreatitis, and to evaluate the preventive effects of octreotide towards the development of acute pancreatitis.

METHODS: Acute pancreatitis was induced in male New Zealand white rabbits by retrograde injection of 0.8 mL/kg·b.m. of 50 g/L sodium taurocholate (NaTC) in the pancreatic duct. Sham-operated animals served as control. Octreotide 1 mg/kg·b.m. was administered subcutaneously before the induction of pancreatitis. Blood was taken from the jugular vein before and at 1, 3, 6, 12 and 24 h after pancreatitis induction. Serum activities of amylase, IL-6 and TNF-α and levels of malonyl dialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), catalase and superoxide dismutase (Mn-, Cu-, and Zn-SOD) in pancreatic tissue were measured.

RESULTS: Serum TNF-α and IL-6 levels increased significantly 3 h after the onset of pancreatitis, and then returned to control level. The tissue concentration of MDA was significantly elevated at 24 h, while the GSH level and GPx, catalase, Mn-SOD, Cu-, Zn-SOD activities were all significantly decreased in animals with pancreatitis as compared to the control. Octreotide pretreatment significantly reversed the changes in cytokines and reactive oxygen metabolites. Octreotide treatment did not alter the serum amylase activity and did not have any beneficial effects on the development of histopathological changes.

CONCLUSION: Oxygen-derived free radicals and proinflammatory cytokines are generated at an early stage of NaTc-induced acute pancreatitis in rabbits. Prophylactic octreotide treatment can prevent release of cytokines and generation of reactive oxygen metabolites, but does not have any beneficial effects on the development of necrotizing pancreatitis.

Prophylactic antibiotic treatment in patients with predicted severe acute pancreatitis: a placebo-controlled, double-blind trial

BACKGROUND & AIMS

Antibiotic prophylaxis in necrotizing pancreatitis remains controversial. Until now, there have been no double-blind studies dealing with this topic.

METHODS

A total sample size of 200 patients was calculated to demonstrate with a power of 90% that antibiotic prophylaxis reduces the proportion of patients with infected pancreatic necrosis from 40% placebo (PLA) to 20% ciprofloxacin/metronidazole (CIP/MET). One hundred fourteen patients with acute pancreatitis in combination with a serum C-reactive protein exceeding 150 mg/L and/or necrosis on contrast-enhanced CT scan were enrolled and received either intravenous CIP (2 x 400 mg/day) + MET (2 x 500 mg/day) or PLA. Study medication was discontinued and switched to open antibiotic treatment when infectious complications, multiple organ failure sepsis, or systemic inflammatory response syndrome (SIRS) occurred. After half of the planned sample size was recruited, an adaptive interim analysis was performed, and recruitment was stopped.

RESULTS

Fifty-eight patients received CIP/MET and 56 patients PLA. Twenty-eight percent in the CIP/MET group required open antibiotic treatment vs. 46% with PLA. Twelve percent of the CIP/MET group developed infected pancreatic necrosis compared with 9% of the PLA group (P = 0.585). Mortality was 5% in the CIP/MET and 7% in the PLA group. In 76 patients with pancreatic necrosis on contrast-enhanced CT scan, no differences in the rate of infected pancreatic necrosis, systemic complications, or mortality were observed.

CONCLUSIONS

This study detected no benefit of antibiotic prophylaxis with respect to the risk of developing infected pancreatic necrosis.

Endothelin(A) receptor blockade reduces ischemia/reperfusion injury in pig pancreas transplantation

OBJECTIVE

The effect of prophylactic administration of a selective endothelin(A) receptor antagonist (ET(A)-RA) on ischemia/reperfusion injury in an experimental model of graft pancreatitis after pancreas transplantation was evaluated.

SUMMARY BACKGROUND DATA

It is well established that endothelin-1 (ET-1), a powerful vasoconstrictor, plays an important role in the development of pancreatitis. Recent studies have shown a beneficial effect of endothelin receptor antagonists in the therapy for experimental pancreatitis.

METHODS

Relevant ischemia/reperfusion injury was induced in pig pancreas transplants after 6 hours hypothermic preservation in University of Wisconsin solution. The recipients were randomized into 2 groups: control pigs received isotonic saline and the treated group received the selective ET(A)-RA BSF 208075 at the beginning of reperfusion. On postoperative days 2 and 5, animals were relaparotomized to obtain tissue specimens. Blood monitoring included lipase, amylase, C-reactive protein, trypsinogen-activation peptide, thiobarbituric acid-reacting substances, and ET-1. Partial oxygen tension (p(ti)O(2)) was measured by a Clarke-type electrode and blood flow by laser doppler. A semiquantitative score index was used for assessment of histologic injury and for immunohistochemical analysis of ET-1 and ET(A) receptor expression. Tissue mRNA levels of prepro ET-1, ET(A) receptor, pro-interleukin (IL)-6, and pro-IL-1beta were quantified using TaqMan real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Prophylactic treatment with ET(A)-RA significantly reduced the severity of graft pancreatitis evidenced by C-reactive protein. The finding of transient capillary perfusion at the beginning of reperfusion supports the application of the ET(A)-RA during this period. The dramatic increase of plasma ET-1 in the therapy group is a clear evidence of effective receptor blockade. Mean trypsinogen-activation peptide levels from the portal venous effluent, but not mean systemic plasma TAP values were significantly lower in the treated group. Analysis of p(ti)O(2) and blood flow revealed a significant improvement of capillary perfusion and blood flow in the treated group and was associated with relevant reduction of tissue injury. Intrapancreatic ET-1 and IL-6 mRNA expression and ET-1 protein levels were significantly lower in the therapy group as compared with the control group. In contrast, ET(A) mRNA showed a marked up-regulation by ET(A) receptor blockade.

CONCLUSION

Application of a ET(A)-RA reduces ischemia/reperfusion induced graft pancreatitis in a pig transplantation model by improving microcirculation and reducing tissue injury.

[Treatment and prophylaxis of infected forms and complications of pancreatic necrosis with the use of regional intraarterial infusion]

The aim of the investigation was to study the variants of the course of sterile and infected pancreatonecrosis, the character of the developing complications depending on the state of organic blood circulation in the pancreas and the influence of its correction upon the outcomes of the disease. The material of examination and treatment of 121 patients with pancreatonecrosis was analyzed. Complex treatment of 51 of the patients included the method of regional intraarterial infusion. Celiacography and CT with the intraarterial contrast reinforcement have revealed that in 35 (68.6%) patients there were symptoms of "perfusion block" of the pancreas of different degrees which was due to spasm, thrombosis of the vessels and impairment of the regional microcirculation. Differentiated approach to the composition of the infusate resulted in arrest of phenomena of "perfusion block" of the pancreas in 24 out of 35 patients. As a whole, using this method allowed to reduce the number of purulent complications, primary open operations and reoperations. Lethality in the group with infusion was 9.8%.

Growth hormone downregulated the excessive apoptosis of ileal intestinal epithelial cells in rats during the early course of acute necrotizing pancreatitis

INTRODUCTION

Growth hormone (GH) has beneficial effects in protecting the intestinal barrier integrity of rats with acute necrotizing pancreatitis (ANP), and the balance between apoptosis and proliferation of intestinal epithelium is one of the key factors in maintenance of the intestinal barrier homeostasis.

AIM

To evaluate further the effect of GH on cell apoptosis of intestinal epithelium in rats with ANP.

METHODOLOGY

Seventy-two rats were randomly divided into 3 groups: sham operation (SO) group (n = 24); ANP group (n = 24); and ANP with GH treatment group (n = 24). ANP in rats was established by injection of 5% sodium taurocholate into the biliopancreatic duct, and laparotomized animals without induction of ANP (sham operation) served as controls. The rats in the GH treatment group received human recombinant GH (0.75 U/kg body weight) subcutaneously once, immediately after operation. The segment of ileum was removed and the detached epithelial cells of ileum were harvested at 3 hours, 6 hours, 12 hours, and 24 hours after operation. Apoptosis of intestinal epithelium was studied by DNA gel electrophoresis, fluorescein isothiocyanate (FITC)-labeled annexin V and propidium iodide (PI) staining under flow cytometry, and the terminal deoxynucleotidyl transferase-mediated d-UTP-biotin nick end labeling (TUNEL) histochemical method.

RESULTS

All specimens harvested at different time points from rats with ANP showed a marked DNA ladder pattern after agarose gel electrophoresis, in comparison with those in the SO group, indicating DNA fragmentation appeared at the early stage in the ANP group. However, a DNA ladder pattern was seen only at 3 hours after operation in the GH-treated rats. The apoptotic percentage assayed by flow cytometry with use of an annexin V kit at 6 hours in the ANP group was significantly higher than in the control group (80% +/- 9% versus 28% +/- 6%; p < 0.01) and was decreased markedly in the GH treatment group (27% +/- 15% versus 80% +/- 9%, p < 0.01). The apoptotic index, studied by the TUNEL method, was obviously higher in the ANP group than in the control group (3 hours: 18 +/- 4 versus 6 +/- 2; 6 hours: 20 +/- 3 versus 8 +/- 2; 12 hours: 15 +/- 2 versus 11 +/- 1; 24 hours: 14 +/- 2 versus 5 +/- 1; p < 0.01), whereas the apoptotic index in the GH treatment group decreased at 3 hours and 6 hours (10 +/- 2 versus 18 +/- 4; 10 +/- 2 versus 20 +/- 3; p < 0.01). The same results were achieved for the apoptotic index of villi tips in the three groups.

CONCLUSION

Apoptosis is a principle model of intestinal epithelial cell death at the early stage of ANP, and GH may downregulate the apoptosis significantly. This action probably is involved in the mechanisms contributing to the protective effects of GH on intestinal barrier integrity in ANP.

Guidelines for treatment of severe acute pancreatitis

Severe acute pancreatitis is a disease of rapid onset and progression with high mortality and morbidity. A new concept suggests that it is multifactorially induced and involves multi-links and that therapy must be directed to several more important links at the same time. The regimen of integrated traditional Chinese and western medicine acts on the same or different sites and links to inhibit or block the inflammatory cascades. Concomitantly, preventive measures were taken at the start of the treatment for preventing the progression of the disease, protecting the function of vital organs, and avoiding the occurrence of complications. No mortality or serious complications occurred in a series of 38 patients with Balthazar's CT grading of D and E. The treatment regimen and the mechanisms of actions of these drugs were delineated in detail in the tables and figure; the regimen is highly recommended for clinical use.

Peptide YY improves local and systemic parameters and prevents death in lethal necrotizing pancreatitis

INTRODUCTION

Peptide YY (PYY) is a gastrointestinal hormone with multiple inhibitory effects on the proximal digestive tract, including suppression of secretion by the exocrine pancreas.

AIM

To determine whether peptide YY would reduce mortality in a lethal model of necrotizing pancreatitis by improving local and systemic parameters of this disease.

METHODOLOGY

Necrotizing pancreatitis was induced in three groups of 30 mice by feeding a choline-deficient ethionine-supplemented diet. Osmotic pumps placed in 10 control mice delivered normal saline. In the two study groups, PYY was delivered at 200 pmol/kg/hr. The prophylactic group received PYY pumps at the onset; the therapeutic group received pumps 24 hours later. Ten mice from each group were followed to assess survival. Remaining mice were killed at 24, 48, 72, and 96 hours. Pancreata were graded on a nine-point histologic scale. Amylasemia was quantified by kinetic determination. Serum interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) values were determined by ELISA.

RESULTS

Both prophylactic and therapeutic PYY significantly reduced mortality compared with that seen in controls ( p = 0.05 and p = 0.007). Five-day survival was 33% in controls, 80% in those receiving prophylactic PYY, and 100% in the therapeutic group. Amylasemia was reduced in the therapeutic group by day 3 ( p < 0.02) and in the prophylactic group by day 4 ( p < 0.01). Histologic changes mirrored those in serum amylase. Prophylactic and therapeutic administration of PYY suppressed early circulating levels of IL-6.

CONCLUSION

PYY reduces mortality and improves local and systemic parameters in this murine model and may be of clinical benefit in the management of human necrotizing pancreatitis, particularly as this study demonstrates a clear survival benefit when PYY is given after the onset of disease.

Prophylactic antibiotics and pancreatic necrosis

Recent controlled clinical studies suggest a positive effect of early antibiotic treatment on late morbidity and mortality in severe acute pancreatitis. In contrast, widespread use of antibiotics may lead to an increased number of fungal infections and multiresistant bacteria. Optimal choice, duration, and route of administration of the antibiotic agent(s) are far from being established. The additional administration of an antifungal agent with prophylactic intention cannot be supported by the currently available data.

Histoprotective effect of antihypoxant olifen during experimental acute pancreatitis

We evaluated the efficiency of perfusion with olifen in preventing oxidative stress at the early stage of acute pancreatitis. Transaortic perfusion with olifen prevented clinical and biochemical symptoms of acute pancreatitis, attenuated oxidative stress, reduced peritoneal exudation, and restricts the area of pancreatic necrosis to 6% tissue.

Prophylactic antibiotic administration reduces sepsis and mortality in acute necrotizing pancreatitis: a meta-analysis

Severe acute pancreatitis is frequently complicated by local and systemic infections resulting in substantial morbidity, mortality, and health care costs. Antibiotic prophylaxis may prevent some infections. We searched for randomized, controlled trials comparing antibiotic prophylaxis with no prophylaxis in patients with acute necrotizing pancreatitis (ANP). Only trials that used antibiotics that reach minimum inhibitory concentration (MIC) in necrotic pancreatic tissue were included. We calculated relative risk reduction (RRR), absolute risk reduction (ARR), and number needed to treat (NNT) for individual trials and pooled data. Antibiotic prophylaxis significantly reduced sepsis by 21.1% (NNT = 5) and mortality by 12.3% (NNT = 8) compared with no prophylaxis. There was also a nonsignificant trend toward a decrease in local pancreatic infections (ARR = 12%; NNT = 8). Antibiotic prophylaxis decreases sepsis and mortality in patients with ANP. All patients with ANP should be given prophylaxis with an antibiotic with proven efficacy in necrotic pancreatic tissue.

[Prophylaxis of acute postoperative pancreatitis in the course of treatment of the giant duodenal ulcer]

The results of surgical treatment of 96 patients with giant duodenal ulcer, to whom selective proximal vagotomy (SPV), duodenoplasty (DP), vagotomy with pylorus destroying operation (PDO), gastric resection were performed, were analyzed. Prophylactic methods for an acute postoperative pancreatitis (APP) occurrence before, during and after the operation performance were elaborated. It was established, that the frequency of APP occurrence after SPV and DP is lower than after gastric resection and vagotomy with PDO.

[The role of antibacterial prophylaxis and therapy in pancreonecrosis]

The research of efficiency of different antibacterial prophylactic and therapy procedures among 89 patients suffering destructive pancreatitis is presented in the article. Determined that optimized tactics of antibacterial prophylactic and therapy with using of such medicines like carbapenems have the important value in cardinal improvement of the results of multi-stage surgical and intensive treatment of the patients suffering pancreonecrosis.

Pancreas-preserving total gastrectomy for gastric cancer

BACKGROUND

Pancreas-preserving total gastrectomy for gastric cancer has been proposed to remove lymph nodes along the upper border of the pancreas without performing a distal pancreatic resection. However, the original technique includes the ligation of the splenic artery at its origin and thus carries the risk of pancreatic necrosis.

HYPOTHESIS

A technique of pancreas-preserving total gastrectomy that includes ligation of the splenic artery approximately 5 cm distally from the root may reduce the risk of postoperative pancreatic necrosis.

DESIGN

Case series.

SETTING

Both primary and referral hospital care.

PATIENTS

Hospital records of 228 consecutive patients who, according to a personal technique, underwent D3 pancreas-preserving total gastrectomy for gastric cancer from 1981 to 1997 were reviewed.

MAIN OUTCOME MEASURES

Surgical complications, postoperative deaths, and survival.

RESULTS

Hospital morbidity and mortality were 33.3% and 3.9%, respectively. No patients experienced pancreatic necrosis. The 5-year survival rate after curative resection was 53.6%: 96.9% for stage IA, 76.3% for stage IB, 63.0% for stage II, 35.6% for stage IIIA, 27.0% for stage IIIB, and 20.3% for stage IV (N3-positive patients) disease.

CONCLUSION

Results of the present study show the efficacy of this method of radical resection for gastric cancer as demonstrated by the low incidence of postoperative complications and high survival rates.

Controlled clinical trial of pefloxacin versus imipenem in severe acute pancreatitis

BACKGROUND & AIMS

Antibiotic prophylaxis in severe pancreatitis has recently yielded promising clinical results, with imipenem significantly reducing the incidence of infected necrosis compared with an untreated control group. On the bases of pefloxacin's spectrum of action and pancreatic penetration, we investigated whether such drugs represent a valid alternative to imipenem.

METHODS

In a multicenter study, 60 patients with severe acute pancreatitis with necrosis affecting at least 50% of the pancreas were randomly allocated to receive intravenous treatment for 2 weeks with pefloxacin, 400 mg twice daily (30 patients), or imipenem, 500 mg three times daily (30 patients), within 120 hours of onset of symptoms. Age, sex, body weight, Ranson and Apache II scores, C-reactive protein, etiology, and time from onset of symptoms to treatment were well matched in the two groups.

RESULTS

The incidences of infected necrosis and extrapancreatic infections were 34% and 44%, respectively, in the pefloxacin group and 10% and 20% in the imipenem group. Imipenem proved significantly more effective in prevention of pancreatic infections (P </= 0.05). Mortality was not significantly different in the two groups.

CONCLUSIONS

Despite its theoretical potential, pefloxacin is inferior to imipenem in the prevention of infections associated with severe pancreatitis.

Multisystemic production of interleukin 10 limits the severity of acute pancreatitis in mice

BACKGROUND

Interleukin 10 (IL-10) decreases the severity of experimental acute pancreatitis. The role of endogenous IL-10 in modulating the course of pancreatitis is currently unknown.

AIMS

To examine the systemic release of IL-10 and its messenger RNA production in the pancrease, liver, and lungs and analyse the effects of IL-10 neutralisation in caerulein induced acute pancreatitis in mice.

METHODS

Acute necrotising pancreatitis was induced by intraperitoneal caerulein. Serum levels of IL-10 and tumour necrosis factor (TNF), and tissue IL-10 and TNF-alpha gene expression were assessed. After injecting control antibody or after blocking the activity of endogenous IL-10 by a specific monoclonal antibody, the severity of acute pancreatitis was assessed in terms of serum enzyme release, histological changes, and systemic and tissue TNF production.

RESULTS

In control conditions, serum IL-10 levels increased and correlated with the course of pancreatitis, with a maximal value eight hours after induction. Both IL-10 and TNF-alpha messengers showed a similar course, and were identified in the pancreas, liver, and lungs. Neutralisation of endogenous IL-10 significantly increased the severity of pancreatitis and associated lung injury as well as serum TNF protein levels (+75%) and pancreatic, pulmonary, and hepatic TNF messenger expression (+33%, +29%, +43%, respectively).

CONCLUSIONS

In this non-lethal model, systemic release of IL-10 correlates with the course of acute pancreatitis. This anti-inflammatory response parallels the release of TNF and both cytokines are produced multisystemically. Endogenous IL-10 controls TNF-alpha production and plays a protective role in the local and systemic consequences of the disease.

The effects of a thromboxane A2 synthesis inhibitor and a prostaglandin I2 analogue on experimental acute necrotizing pancreatitis in rats

To elucidate the role of thromboxane A2 (TxA2) and prostaglandin I2 (PGI2) in acute necrotizing pancreatitis (ANP) in rats and to determine the effect of the TxA2 synthesis inhibitor OKY-046 and the PGI2 analogue OP-2507, the levels of two prostanoids (TxB2, 6-keto PGF1alpha) and two types of phospholipase A2 (PLA2) activity (cytosolic and secretory) were measured in plasma and three tissues (pancreas, lung, and kidney) after injection of a mixed solution of 5% sodium taurocholate and 0.1% trypsin into the pancreatic duct to induce ANP. The survival rate 24 h after inducing ANP was 33.3% in the nontreated group, versus 83.3 and 58.3% in the groups treated with OKY-046 and OP-2507, respectively. Only the group treated with OKY-046 showed significant improvement compared with the nontreated group. The plasma, pancreatic, and pulmonary TxB2 levels decreased significantly in the group treated with OKY-046, and the histopathological changes were not as severe. The levels of pancreatic and pulmonary cytosolic PLA2 activities decreased, and plasma and pancreatic secretory PLA2 activities also decreased. In conclusion, the levels of both types of PLA2 activity and TxA2 production decreased, and the survival rate improved as a result in the group treated with OKY-046, but OP-2507 had no effect on ANP. TxA2 and two types of PLA2 activity play an important role in the process of aggravation of acute pancreatitis.

[Prophylactic antibiotics in acute pancreatitis. Results from a consensus conference]

Pancreatic infection is the leading cause of death from acute pancreatitis. Patients with severe necrotizing pancreatitis are most at risk. Early dynamic computed tomography and percutaneous fine-needle aspiration microbiology of areas of necrosis enable early diagnosis. Several studies has been undertaken in order to investigate the type of bacteria and the concentration reached in pancreatic tissue by different antibiotics. Nevertheless, up to now only three clinical trials of prophylactic antibiotics in acute pancreatitis has been reported. In the IV meeting of the Spanish Association for the Study of the Pancreas, a consensus conference took place with this topic.