Randomised, double blind, placebo controlled trial of intravenous antioxidant (n-acetylcysteine, selenium, vitamin C) therapy in severe acute pancreatitis

Therapeutic implications of oxidative stress in acute and chronic pancreatitis

PURPOSE OF REVIEW

This review presents new evidence on the role of oxidative stress and antioxidant status in acute and chronic pancreatitis published in the last year.

RECENT FINDINGS

In-vitro studies showed that protein phosphatases may play an important role in the interaction between reactive oxygen species and proinflammatory cytokines in acute pancreatitis. In-vivo studies found that several natural compounds ameliorate oxidative stress and, therefore, have therapeutic potential. In the domain of clinical studies, the major development is the first double-blind placebo-controlled randomized trial that showed effectiveness of oral antioxidant supplementation (organic selenium, ascorbic acid, alpha-tocopherol, beta-carotene, and methionine) in relieving pain in patients with chronic pancreatitis. The developments in clinical studies on acute pancreatitis are less spectacular and mainly limited to evaluation of different markers of oxidative stress and antioxidant status in the course of disease.

SUMMARY

A significant advance has been made in the arena of research in chronic, but not acute, pancreatitis. There is now solid evidence to justify the use of oral antioxidants in the treatment of patients with chronic pancreatitis. The progress in clinical research on antioxidants in acute pancreatitis is hampered by several factors, including suboptimal classification of acute pancreatitis and route of administration used in previous studies.

Safety assessment of probiotics for human use

The safety of probiotics is tied to their intended use, which includes consideration of potential vulnerability of the consumer or patient, dose and duration of consumption, and both the manner and frequency of administration. Unique to probiotics is that they are alive when administered, and unlike other food or drug ingredients, possess the potential for infectivity or in situ toxin production. Since numerous types of microbes are used as probiotics, safety is also intricately tied to the nature of the specific microbe being used. The presence of transferable antibiotic resistance genes, which comprises a theoretical risk of transfer to a less innocuous member of the gut microbial community, must also be considered. Genetic stability of the probiotic over time, deleterious metabolic activities, and the potential for pathogenicity or toxicogenicity must be assessed depending on the characteristics of the genus and species of the microbe being used. Immunological effects must be considered, especially in certain vulnerable populations, including infants with undeveloped immune function. A few reports about negative probiotic effects have surfaced, the significance of which would be better understood with more complete understanding of the mechanisms of probiotic interaction with the host and colonizing microbes. Use of readily available and low cost genomic sequencing technologies to assure the absence of genes of concern is advisable for candidate probiotic strains. The field of probiotic safety is characterized by the scarcity of studies specifically designed to assess safety contrasted with the long history of safe use of many of these microbes in foods.

Evaluation of the antioxidant properties of N-acetylcysteine in human platelets: prerequisite for bioconversion to glutathione for antioxidant and antiplatelet activity

N-Acetylcysteine (NAC) is a frequently used "antioxidant" in vitro, but the concentrations applied rarely correlate with those encountered with oral dosing in vivo. Here, we investigated the in vitro antioxidant and antiplatelet properties of NAC at concentrations (10-100 microM) that are achievable in plasma with tolerable oral dosing. The impact of NAC pretreatment (2 hours) on aggregation of platelets from healthy volunteers in response to thrombin and adenosine diphosphate and on platelet-derived nitric oxide (NO) was examined. NAC was found to be a weak reducing agent and a poor antioxidant compared with glutathione (reduced form) (GSH). However, platelets treated with NAC showed enhanced antioxidant activity and depression of reactive oxygen species generation associated with increases in intraplatelet GSH levels. An approximately 2-fold increase in NO synthase-derived nitrite was observed with 10 microM NAC treatment, but the effect was not concentration dependent. Finally, NAC significantly reduced both thrombin-induced and adenosine diphosphate-induced platelet aggregation. NAC should be considered a weak antioxidant that requires prior conversion to GSH to convey antioxidant and antithrombotic benefit at therapeutically relevant concentrations. Our results suggest that NAC might be an effective antiplatelet agent in conditions where increased oxidative stress contributes to heightened risk of thrombosis but only if the intraplatelet machinery to convert it to GSH is functional.

Nutritional strategies in severe acute pancreatitis: a systematic review of the evidence

Nutrition in severe acute pancreatitis is a critical aspect in the management of this condition. This review aims to systematically review the evidence available to inform the use of nutritional support in severe acute pancreatitis. High quality (level 1) evidence supports naso-jejunal enteral nutrition (NJ-EN) over parenteral nutrition (PN) reducing infectious morbidity and showing a trend towards reduced organ failure although there is no detectable difference in mortality. Trial data may underestimate benefit as patients are often recruited with predicted rather than proven severe disease. NJ-EN is safe when started immediately (level 3 evidence). NJ-EN is often impractical and naso-gastric (NG) feeding seems to be equivalent in terms of safety and outcomes whilst being more practical (level 2 evidence). Regarding feed supplementation, probiotic feed supplementation is not beneficial (level 1 evidence) the and may cause harm with excess mortality (level 2 evidence). No evidence exists to confirm benefit of the addition of prokinetics in severe acute pancreatitis (SAP) although their use is proven in other critically ill patients. Level 2 evidence does not currently support the use of combination immuno-nutrition though further work on individual agents may provide differing results. Level 2 evidence does not support intravenous supplementation of anti-oxidants and has demonstrated that these too may cause harm.

Green tea polyphenols ameliorate pancreatic injury in cerulein-induced murine acute pancreatitis

OBJECTIVE

Green tea polyphenols (GTPs) are naturally occurring antioxidants acting through pathways that include reactive oxygen species and nuclear factor kappa B (NF-kappaB). This study investigates the effect of GTPs in a cerulein-induced murine model of acute pancreatitis (AP).

METHODS

Male CD mice (median weight, 37.7 g) were divided into 4 groups: mice administered with cerulein alone, cerulein and GTP, saline alone (sham), and GTP alone. Acute pancreatitis was induced by serial intraperitoneal administration of cerulein (50 microg/kg, x6). Green tea polyphenol was administered intraperitoneally at 25 mg/kg on the first, third, and sixth hours after pancreatitis induction.We analyzed histologic and biochemical features of AP, NF-kappaB pathway activity, leukocyte-mediated damage, cytokine levels, oxidative stress injury, lipid peroxidation, expression of poly-(adenosine diphosphate-ribose) synthetase, and presence of apoptosis.

RESULTS

Treatment with GTP reduced the histologic and biochemical features of AP. Western blot revealed significant NF-kappaB inactivation. Immunostaining for P selectin and intercellular adhesion molecule 1, tumor necrosis factor alpha, transforming growth factor beta, vascular endothelial growth factor, nitrotirosine, poly-(adenosine diphosphate ribose) synthetase, and malondialdheide levels were significantly reduced. There was a significant down-regulation of apoptotic markers.

CONCLUSIONS

Our results demonstrated that GTP significantly ameliorated the effects of cerulein-induced AP in mice. These effects of GTP are mediated by actions at the NF-kappaB/IkB (inhibitor kB) proteins and oxidative stress pathways.

Antioxidant therapy in the management of acute, chronic and post-ERCP pancreatitis: A systematic review

We systematically reviewed the clinical trials which recruited antioxidants in the therapy of pancreatitis and evaluated whether antioxidants improve the outcome of patients with pancreatitis. Electronic bibliographic databases were searched for any studies which investigated the use of antioxidants in the management of acute pancreatitis (AP) or chronic pancreatitis (CP) and in the prevention of post-endoscopic retrograde cholangio-pancreatography (post-ERCP) pancreatitis (PEP) up to February 2009. Twenty-two randomized, placebo-controlled, clinical trials met our criteria and were included in the review. Except for a cocktail of antioxidants which showed improvement in outcomes in three different clinical trials, the results of the administration of other antioxidants in both AP and CP clinical trials were incongruent and heterogeneous. Furthermore, antioxidant therapy including allopurinol and N-acetylcysteine failed to prevent the onset of PEP in almost all trials. In conclusion, the present data do not support a benefit of antioxidant therapy alone or in combination with conventional therapy in the management of AP, CP or PEP. Further double blind, randomized, placebo-controlled clinical trials with large sample size need to be conducted.

ESPEN Guidelines on Parenteral Nutrition: pancreas

Assessment of the severity of acute pancreatitis (AP), together with the patient's nutritional status is crucial in the decision making process that determines the need for artificial nutrition. Both should be done on admission and at frequent intervals thereafter. The indication for nutritional support in AP is actual or anticipated inadequate oral intake for 5-7 days. This period may be shorter in those with pre-existing malnutrition. Substrate metabolism in severe AP is similar to that in severe sepsis or trauma. Parenteral amino acids, glucose and lipid infusion do not affect pancreatic secretion and function. If lipids are administered, serum triglycerides must be monitored regularly. The use of intravenous lipids as part of parenteral nutrition (PN) is safe and feasible when hypertriglyceridemia is avoided. PN is indicated only in those patients who are unable to tolerate targeted requirements by the enteral route. As rates of EN tolerance increase then volumes of PN should be decreased. When PN is administered, particular attention should be given to avoid overfeeding. When PN is indicated, a parenteral glutamine supplementation should be considered. In chronic pancreatitis PN may, on rare occasions, be indicated in patients with gastric outlet obstruction secondary to duodenal stenosis or those with complex fistulation, and in occasional malnourished patients prior to surgery.

Critical Care of the Patient with Acute Pancreatitis

Acute pancreatitis is an inflammatory process of the pancreas with variable involvement of regional tissues and remote organs. This review gives a comprehensive overview of the aetiology, pathophysiology, diagnosis and therapy of acute pancreatitis relevant to the intensivist. Recent international guidelines on the management of acute pancreatitis are summarised.

Eighty percent of acute pancreatitis episodes are related either to gallstones or to alcohol abuse. Independent of its aetiology, the pathophysiologic hallmark of acute pancreatitis is the premature activation of trypsin, which leads to massive pancreas inflammation, systemic overproduction of pro-inflammatory mediators and ultimately remote organ dysfunction. All guidelines agree that the diagnosis of acute pancreatitis should include clinical symptoms, increased serum amylase or lipase levels and/or characteristic findings on computed tomography. Endoscopic retrograde cholangiopancreatography is recommended as a causative therapy in patients with acute cholangitis or a strong suspicion of gallstones. All guidelines underline the importance of vigorous fluid resuscitation and supplemental oxygen therapy and prefer enteral over parenteral nutrition, with the majority favouring the nasojejunal route. In view of lacking scientific evidence, antibiotic prophylaxis to prevent infection of pancreatic necroses is discouraged by most guidelines. Computed tomography-guided fine needle aspiration is the technique of choice to differentiate between sterile and infected pancreas necrosis. While sterile pancreatic necrosis should be managed conservatively, infected pancreatic necrosis requires debridement and drainage supplemented by antibiotic therapy. Surgical necrosectomy is the traditional approach, but less invasive techniques (retroperitoneal or laparoscopic necrosectomy, computed tomography-guided percutaneous catheter drainage) may be equally effective.

Probiotics prevent intestinal barrier dysfunction in acute pancreatitis in rats via induction of ileal mucosal glutathione biosynthesis

Background

During acute pancreatitis (AP), oxidative stress contributes to intestinal barrier failure. We studied actions of multispecies probiotics on barrier dysfunction and oxidative stress in experimental AP.

Methodology/Principal Findings

Fifty-three male Spraque-Dawley rats were randomly allocated into five groups: 1) controls, non-operated, 2) sham-operated, 3) AP, 4) AP and probiotics and 5) AP and placebo. AP was induced by intraductal glycodeoxycholate infusion and intravenous cerulein (6 h). Daily probiotics or placebo were administered intragastrically, starting five days prior to AP. After cerulein infusion, ileal mucosa was collected for measurements of E. coli K12 and ⁵¹Cr-EDTA passage in Ussing chambers. Tight junction proteins were investigated by confocal immunofluorescence imaging. Ileal mucosal apoptosis, lipid peroxidation, and glutathione levels were determined and glutamate-cysteine-ligase activity and expression were quantified. AP-induced barrier dysfunction was characterized by epithelial cell apoptosis and alterations of tight junction proteins (i.e. disruption of occludin and claudin-1 and up-regulation of claudin-2) and correlated with lipid peroxidation (r>0.8). Probiotic pre-treatment diminished the AP-induced increase in E. coli passage (probiotics 57.4±33.5 vs. placebo 223.7±93.7 a.u.; P<0.001), ⁵¹Cr-EDTA flux (16.7±10.1 vs. 32.1±10.0 cm/s10⁻⁶; P<0.005), apoptosis, lipid peroxidation (0.42±0.13 vs. 1.62±0.53 pmol MDA/mg protein; P<0.001), and prevented tight junction protein disruption. AP-induced decline in glutathione was not only prevented (14.33±1.47 vs. 8.82±1.30 nmol/mg protein, P<0.001), but probiotics even increased mucosal glutathione compared with sham rats (14.33±1.47 vs. 10.70±1.74 nmol/mg protein, P<0.001). Glutamate-cysteine-ligase activity, which is rate-limiting in glutathione biosynthesis, was enhanced in probiotic pre-treated animals (probiotics 2.88±1.21 vs. placebo 1.94±0.55 nmol/min/mg protein; P<0.05) coinciding with an increase in mRNA expression of glutamate-cysteine-ligase catalytic (GCLc) and modifier (GCLm) subunits.

Conclusions

Probiotic pre-treatment diminished AP-induced intestinal barrier dysfunction and prevented oxidative stress via mechanisms mainly involving mucosal glutathione biosynthesis.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

A randomized controlled trial of antioxidant supplementation for pain relief in patients with chronic pancreatitis

BACKGROUND & AIMS

Oxidative stress has been implicated in the pathophysiology of chronic pancreatitis (CP). We evaluated the effects of antioxidant supplementation on pain relief, oxidative stress, and antioxidant status in patients with CP.

METHODS

In a placebo-controlled double blind trial, consecutive patients with CP were randomized to groups that were given placebo or antioxidants for 6 months. The primary outcome measure was pain relief, and secondary outcome measures were analgesic requirements, hospitalization, and markers of oxidative stress (thiobarbituric acid-reactive substances [TBARS]) and antioxidant status (ferric-reducing ability of plasma [FRAP]).

RESULTS

Patients (age 30.5+/-10.5 years, 86 male, 35 alcoholic, and 92 with idiopathic CP) were assigned to the placebo (n=56) or antioxidant groups (n=71). After 6 months, the reduction in the number of painful days per month was significantly higher in the antioxidant group compared with the placebo group (7.4+/-6.8 vs 3.2+/-4, respectively; P< .001; 95% CI, 2.07, 6.23). The reduction in the number of analgesic tablets per month was also higher in the antioxidant group (10.5+/-11.8 vs 4.4+/-5.8 respectively; P= .001; 95% CI, 2.65, 9.65). Furthermore, 32% and 13% of patients became pain free in the antioxidant and placebo groups, respectively (P= .009). The reduction in the level of TBARS and increase in FRAP were significantly higher in the antioxidant group compared with the placebo group (TBARS: placebo 1.2+/-2.7 vs antioxidant 3.5+/-3.4 nmol/mL; P= .001; 95% CI 0.96, 3.55; FRAP: placebo -5.6+/-154.9 vs antioxidant 97.8+/-134.9 microMFe(+2) liberated, P= .001, 95% CI 44.98, 161.7).

CONCLUSIONS

Antioxidant supplementation was effective in relieving pain and reducing levels of oxidative stress in patients with CP.

Selenium in Critically Ill Patients

There is increasing evidence that particular nutritional substrates may be important in critically ill patients and in recent years there has been growing interest in selenium. This review aims to outline the incidence of selenium deficiency in critically ill patients, the consequences of such a deficiency and present the evidence for, and effect of, selenium supplementation in these patients. Selenium levels fall during periods of oxidative stress as occurs in critically ill patients with conditions such as severe sepsis, burns, and following trauma. Data from individual studies and meta-analyses suggests that selenium is an important adjuvant therapy in certain critically ill patients and supplementation of selenium may offer a mortality benefit.

Probiotics enhance pancreatic glutathione biosynthesis and reduce oxidative stress in experimental acute pancreatitis

Factors determining severity of acute pancreatitis (AP) are poorly understood. Oxidative stress causes acinar cell injury and contributes to the severity, whereas prophylactic probiotics ameliorate experimental pancreatitis. Our objective was to study how probiotics affect oxidative stress, inflammation, and acinar cell injury during the early phase of AP. Fifty-three male Sprague-Dawley rats were randomly allocated into groups: 1) control, 2) sham procedure, 3) AP with no treatment, 4) AP with probiotics, and 5) AP with placebo. AP was induced under general anesthesia by intraductal glycodeoxycholate infusion (15 mM) and intravenous cerulein (5 microg.kg(-1).h(-1), for 6 h). Daily probiotics or placebo were administered intragastrically, starting 5 days prior to AP. After cerulein infusion, pancreas samples were collected for analysis including lipid peroxidation, glutathione, glutamate-cysteine-ligase activity, histological grading of pancreatic injury, and NF-kappaB activation. The severity of pancreatic injury correlated to oxidative damage (r = 0.9) and was ameliorated by probiotics (1.5 vs. placebo 5.5; P = 0.014). AP-induced NF-kappaB activation was reduced by probiotics (0.20 vs. placebo 0.53 OD(450nm)/mg nuclear protein; P < 0.001). Probiotics attenuated AP-induced lipid peroxidation (0.25 vs. placebo 0.51 pmol malondialdehyde/mg protein; P < 0.001). Not only was AP-induced glutathione depletion prevented (8.81 vs. placebo 4.1 micromol/mg protein, P < 0.001), probiotic pretreatment even increased glutathione compared with sham rats (8.81 vs. sham 6.18 miccromol/mg protein, P < 0.001). Biosynthesis of glutathione (glutamate-cysteine-ligase activity) was enhanced in probiotic-pretreated animals. Probiotics enhanced the biosynthesis of glutathione, which may have reduced activation of inflammation and acinar cell injury and ameliorated experimental AP, via a reduction in oxidative stress.

Impact of high-dose antioxidants on outcomes in acutely injured patients

BACKGROUND

The profound oxidative stress that occurs following injury results in significant depletion of many endogenous antioxidants (vitamin C, E, selenium). Increasing evidence suggests antioxidant supplementation reduces infectious complications and organ dysfunction following injury and hemorrhagic shock. The purpose of this study was to evaluate the impact of high-dose antioxidant administration on the mortality rate of acutely injured patients.

METHODS

In October 2005, we implemented a 7-day high-dose antioxidant protocol for acutely injured patients admitted to our trauma center. A retrospective cohort study, evaluating all patients admitted to the trauma service between October 2005 and September 2006 following protocol implementation (AO+), was performed. The comparison cohort (AO-) was made up of those patients admitted in the year prior to protocol implementation.

RESULTS

A total of 4,294 patients met criteria (AO+, N = 2,272; AO-, N = 2022). Hospital (4 vs 3 days, P < .001) and ICU (3 vs 2 days, P = .001) median length of stays were significantly shorter in the AO+ group. Mortality was significantly lower in the AO+ group (6.1% vs 8.5%, P = .001), translating into a 28% relative risk reduction for mortality in patients exposed to high-dose antioxidants. After adjusting for age, gender, and probability of survival, AO exposure was associated with even lower mortality (OR 0.32, 95% CI 0.22-0.46). Patients with an expected survival <50% benefited most (OR 0.24, 95% CI 0.15-0.37).

CONCLUSIONS

A high-dose antioxidant protocol resulted in a 28% relative risk reduction in mortality and a significant reduction in both hospital and ICU length of stay. This protocol represents an inexpensive intervention to reduce mortality/morbidity in the trauma patient.

Antioxidant supplements for preventing gastrointestinal cancers

BACKGROUND

Oxidative stress may cause gastrointestinal cancers. The evidence on whether antioxidant supplements are effective in preventing gastrointestinal cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

SEARCH STRATEGY

We identified trials through the trials registers of the four Cochrane Review Groups on gastrointestinal diseases, The Cochrane Central Register of Controlled Trials in The Cochrane Library (Issue 2, 2007), MEDLINE, EMBASE, LILACS, SCI-EXPANDED, and The Chinese Biomedical Database from inception to October 2007. We scanned reference lists and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing antioxidant supplements to placebo/no intervention examining occurrence of gastrointestinal cancers.

DATA COLLECTION AND ANALYSIS

Two authors (GB and DN) independently selected trials for inclusion and extracted data. Outcome measures were gastrointestinal cancers, overall mortality, and adverse effects. Outcomes were reported as relative risks (RR) with 95% confidence interval (CI) based on random-effects and fixed-effect model meta-analysis. Meta-regression assessed the effect of covariates across the trials.

MAIN RESULTS

We identified 20 randomised trials (211,818 participants), assessing beta-carotene (12 trials), vitamin A (4 trials), vitamin C (8 trials), vitamin E (10 trials), and selenium (9 trials). Trials quality was generally high. Heterogeneity was low to moderate. Antioxidant supplements were without significant effects on gastrointestinal cancers (RR 0.94, 95% CI 0.83 to 1.06). However, there was significant heterogeneity (I(2) = 54.0%, P = 0.003). The heterogeneity may have been explained by bias risk (low-bias risk trials RR 1.04, 95% CI 0.96 to 1.13 compared to high-bias risk trials RR 0.59, 95% CI 0.43 to 0.80; test of interaction P < 0.0005), and type of antioxidant supplement (beta-carotene potentially increasing and selenium potentially decreasing cancer risk). The antioxidant supplements had no significant effects on mortality in a random-effects model meta-analysis (RR 1.02, 95% CI 0.97 to 1.07, I(2) = 53.5%), but significantly increased mortality in a fixed-effect model meta-analysis (RR 1.04, 95% CI 1.02 to 1.07). Beta-carotene in combination with vitamin A (RR 1.16, 95% CI 1.09 to 1.23) and vitamin E (RR 1.06, 95% CI 1.02 to 1.11) significantly increased mortality. Increased yellowing of the skin and belching were non-serious adverse effects of beta-carotene. In five trials (four with high risk of bias), selenium seemed to show significant beneficial effect on gastrointestinal cancer occurrence (RR 0.59, 95% CI 0.46 to 0.75, I(2) = 0%).

AUTHORS' CONCLUSIONS

We could not find convincing evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, antioxidant supplements seem to increase overall mortality. The potential cancer preventive effect of selenium should be tested in adequately conducted randomised trials.

Pharmacological approach to acute pancreatitis

The aim of the present review is to summarize the current knowledge regarding pharmacological prevention and treatment of acute pancreatitis (AP) based on experimental animal models and clinical trials. Somatostatin (SS) and octreotide inhibit the exocrine production of pancreatic enzymes and may be useful as prophylaxis against Post Endoscopic retrograde cholangiopancreatography Pancreatitis (PEP). The protease inhibitor Gabexate mesilate (GM) is used routinely as treatment to AP in some countries, but randomized clinical trials and a meta-analysis do not support this practice. Nitroglycerin (NGL) is a nitrogen oxide (NO) donor, which relaxes the sphincter of Oddi. Studies show conflicting results when applied prior to ERCP and a large multicenter randomized study is warranted. Steroids administered as prophylaxis against PEP has been validated without effect in several randomized trials. The non-steroidal anti-inflammatory drugs (NSAID) indomethacin and diclofenac have in randomized studies showed potential as prophylaxis against PEP. Interleukin 10 (IL-10) is a cytokine with anti-inflammatory properties but two trials testing IL-10 as prophylaxis to PEP have returned conflicting results. Antibodies against tumor necrosis factor-alpha (TNF-α) have a potential as rescue therapy but no clinical trials are currently being conducted. The antibiotics beta-lactams and quinolones reduce mortality when necrosis is present in pancreas and may also reduce incidence of infected necrosis. Evidence based pharmacological treatment of AP is limited and studies on the effect of potent anti-inflammatory drugs are warranted.

Nutritional support in acute pancreatitis

PURPOSE OF REVIEW

This review explores the role of enteral and parenteral nutrition in severe acute pancreatitis and discusses the potential benefits of glutamine, omega-3 fatty acids, arginine and selenium together with probiotics and prebiotics in these patients. In addition, the method of refeeding during the convalescent period is also examined.

RECENT FINDINGS

A complex picture is emerging in which enteral nutritional support may be important early in the course of the disease with parenteral nutrition being used more as a backup and possibly only after the systemic inflammatory response has peaked. Nasogastric feeding, sometimes supplemented by parenteral nutrition, is as efficacious as nasojejunal feeding. An individualized approach, in which strategies of nutritional support are tailored to patient response, is gaining currency. Data regarding specialized formulae are mixed but the use of prebiotics is showing promise and is worthy of further exploration. In the convalescent period, preliminary data also indicate that the risk of pain developing is no greater if a light diet is instituted rather than clear fluids.

SUMMARY

Nutritional support in acute pancreatitis remains challenging and controversial with a number of different and unexpected approaches, including the use of nasogastric feeding and dual enteral and parenteral nutrition support, being adopted in recent clinical trials.

Antioxidants in acute pancreatitis

Antioxidant supplements may be ineffective for the treatment or prevention of organ failure in predicted severe acute pancreatitis

Antioxidant supplements for preventing gastrointestinal cancers

BACKGROUND

Oxidative stress may cause gastrointestinal cancers. The evidence on whether antioxidant supplements are effective in preventing gastrointestinal cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

SEARCH STRATEGY

We identified trials through the trials registers of the four Cochrane Review Groups on gastrointestinal diseases, The Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 1, 2003), MEDLINE, EMBASE, LILACS, and SCI-EXPANDED from inception to February 2003, and The Chinese Biomedical Database (March 2003). We scanned reference lists and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing antioxidant supplements to placebo/no intervention examining the incidence of gastrointestinal cancers.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted data. The outcome measures were incidence of gastrointestinal cancers, overall mortality, and adverse events. Outcomes were reported as relative risks (RR) with 95% confidence interval (CI) based on fixed and random effects meta-analyses.

MAIN RESULTS

We identified 14 randomised trials (170,525 participants), assessing beta-carotene (9 trials), vitamin A (4 trials), vitamin C (4 trials), vitamin E (5 trials), and selenium (6 trials). Trial quality was generally high. Heterogeneity was low to moderate. Neither the fixed effect (RR 0.96, 95% CI 0.88 to 1.04) nor random effects meta-analyses (RR 0.90, 95% CI 0.77 to 1.05) showed significant effects of supplementation with antioxidants on the incidences of gastrointestinal cancers. Among the seven high-quality trials reporting on mortality (131,727 participants), the fixed effect (RR 1.06, 95% CI 1.02 to 1.10) unlike the random effects meta-analysis (RR 1.06, 95% CI 0.98 to 1.15) showed that antioxidant supplements significantly increased mortality. Two low-quality trials (32,302 participants) found no significant effect of antioxidant supplementation on mortality. The difference between the mortality estimates in high- and low-quality trials was significant by test of interaction (z = 2.10, P = 0.04). Beta-carotene and vitamin A (RR 1.29, 95% CI 1.14 to 1.45) and beta-carotene and vitamin E (RR 1.10, 95% CI 1.01 to 1.20) significantly increased mortality, while beta-carotene alone only tended to do so (RR 1.05, 95% CI 0.99 to 1.11). Increased yellowing of the skin and belching were non-serious adverse effects of beta-carotene. In four trials (three with unclear/inadequate methodology), selenium showed significant beneficial effect on gastrointestinal cancer incidences.

REVIEWERS' CONCLUSIONS

We could not find evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, they seem to increase overall mortality. The potential cancer preventive effect of selenium should be studied in adequately conducted randomised trials.