Pancreatic microcirculation in acute pancreatitis

Computed tomographic evaluation of pancreatic perfusion in 10 dogs with acute pancreatitis

Severe canine acute pancreatitis can be fatal; imaging features that can predict the clinical course of disease are useful for clinicians. On computed tomography (CT), both pancreatic heterogeneous contrast enhancement and portal vein thrombosis have been correlated with poorer outcome. Perfusion CT is used in human medicine to evaluate pancreatic microcirculation to predict the future development of severe sequela to pancreatitis; this technology has yet to be explored in dogs with acute pancreatitis. The objective of this prospective, case-control study is to evaluate pancreatic perfusion using contrast-enhanced CT in dogs with acute pancreatitis and compare it with previously established values obtained in healthy dogs. Ten client-owned dogs preliminarily diagnosed with acute pancreatitis received a full abdominal ultrasound, specific canine pancreatic lipase (Spec cPL), and perfusion CT. Computer software calculated pancreatic perfusion, peak enhancement index, time to peak enhancement, and blood volume for 3-mm and reformatted 6-mm slices. The data was analyzed using Shapiro-Wilk test, linear mixed model, and Spearman's rho. Values for 3-mm slices were similar to 6-mm slices (all P < 0.05). Dogs with acute pancreatitis had a faster time to peak enhancement than healthy dogs (P = 0.04-0.06). Dogs with acute pancreatitis and homogeneous pancreatic enhancement had higher perfusion, faster time to peak enhancement, and greater blood volume compared to healthy dogs and dogs with acute pancreatitis and heterogeneous pancreatic enhancement (all P = / < 0.05). Pancreatic perfusion decreased with increased pancreatitis severity. No correlation was identified between Spec cPL and pancreatic perfusion (all P > 0.05). These findings preliminarily support perfusion CT in dogs with acute pancreatitis.

Glucocorticoid Treatment in Acute Respiratory Distress Syndrome: An Overview on Mechanistic Insights and Clinical Benefit

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS), triggered by various pathogenic factors inside and outside the lungs, leads to diffuse lung injury and can result in respiratory failure and death, which are typical clinical critical emergencies. Severe acute pancreatitis (SAP), which has a poor clinical prognosis, is one of the most common diseases that induces ARDS. When SAP causes the body to produce a storm of inflammatory factors and even causes sepsis, clinicians will face a two-way choice between anti-inflammatory and anti-infection objectives while considering the damaged intestinal barrier and respiratory failure, which undoubtedly increases the difficulty of the diagnosis and treatment of SAP-ALI/ARDS. For a long time, many studies have been devoted to applying glucocorticoids (GCs) to control the inflammatory response and prevent and treat sepsis and ALI/ARDS. However, the specific mechanism is not precise, the clinical efficacy is uneven, and the corresponding side effects are endless. This review discusses the mechanism of action, current clinical application status, effectiveness assessment, and side effects of GCs in the treatment of ALI/ARDS (especially the subtype caused by SAP).

Management of Necrotizing Pancreatitis

Necrotizing pancreatitis affects 10% to 15% of all patients with acute pancreatitis. Despite improved understanding of this complex disease, it is still attended by up to 15% mortality. Necrotizing pancreatitis provides the clinical challenges of working in a multi-disciplinary group, determining proper timing for intervention, and identifying appropriate intervention approaches. The step-up approach consists of supportive care initially. When there is documented infected necrosis, treatment begins with antibiotics, progressing to minimally invasive mechanical necrosis intervention, and reserving surgery as the final treatment modality. However, treatment must be tailored to the individual patient. This article provides an overview of necrotizing pancreatitis.

Treatment of Microcirculatory Disturbances in Acute Pancreatitis: Where Are We Now?

Acute pancreatitis is a serious inflammatory condition. Research has shown an increase in the number of pancreatitis-associated hospitalizations, with a marked decline in the mortality rates down to 0.79% in patients with acute pancreatitis and 0.26% in patients with exacerbation of chronic pancreatitis. Up to one-third of patients develop pancreatic tissue necrosis, with a mortality rate of 30%. One of the mechanisms is the disturbances in pancreatic microcirculation due to the release of endothelin, a long-acting vasoconstrictor. The development of pancreatitis causes the release of other inflammatory mediators, which reduce blood flow in the microcirculation. The activation of intracellular trypsinogen initiates a cascade of mechanisms in pancreatitis. There is no specific treatment for acute pancreatitis. Protease inhibitors are not effective in treating severe acute pancreatitis. There is an important role of low-molecular-weight heparin in attenuating necrosis and restoring perfusion of the pancreas. Other drugs used are endothelin receptor antagonists, antagonist of interleukin-1 and interleukin-6 receptors, α-tocopherol, tumor necrosis factor-α and platelet-activating factor inhibitors, acetylsalicylic acid, and local intra-arterial injection of lidocaine. The prophylactic use of antibiotics is not recommended. The treatment outcome of acute pancreatitis is still unsatisfactory.

Efficacy and Safety of Thoracic Epidural Analgesia in Patients With Acute Pancreatitis: A Narrative Review

Patients admitted to the intensive care unit with moderate to severe acute pancreatitis carry significant morbidity and mortality. A few unfortunate patients in whom the initial line of treatment fails to show clinical improvement develop multiorgan dysfunction involving lungs (adult respiratory distress syndrome), renal failure, intra-abdominal infections, sepsis, and septic shock, which ultimately leads to prolonged hospitalization and a substantial cost of treatment. The acute abdominal pain experienced by these patients is excruciating and requires multimodal analgesia. Continuous epidural analgesia has been found to provide good quality, opioid-sparing analgesia in these patients. A few studies have also demonstrated that segmental sympathectomy resulting from epidural blockade could lead to lowering of serum amylase and lipase levels improve paralytic ileus, and thus hastens the process of recovery. The present paper aims to discuss the advantages of continuous epidural analgesia in patients with acute pancreatitis of varying severity and to review the existing literature using specific keywords.

Development of ex situ normothermic reperfusion as an innovative method to assess pancreases after preservation

Static cold storage (SCS) is the standard method for pancreas preservation prior to transplantation; however, it does not permit organ assessment. Normothermic reperfusion (NR) is utilized clinically for other organs to assess viability. Our aim was to develop NR using normothermic machine perfusion technique to simulate reperfusion at the time of transplantation, enabling evaluation of oxygenated hypothermic machine perfusion (HMPO2) as a newer strategy to optimize pancreas preservation. 13 porcine pancreases procured after circulatory death were divided into 3 groups: 4 pancreases preserved using SCS, and 2 groups preserved by HMPO2 (n = 4 and n = 5, differing by type of preservation solution). Duration of perfusion or cold storage was 6 hours before the 1-hour assessment using NR. Outcome measures were perfusion characteristics, biochemistry and change in tissue water mass as oedema assessment. During NR, the HMPO2 groups demonstrated better perfusion characteristics, normal macroscopic appearances, decreased water mass and one HMPO2 group demonstrated a response to glucose stimulation. Conversely, the SCS group showed an increased water mass and developed early macroscopic appearances of oedema, interstitial haemorrhage and minimal portal outflow. This study suggests that ex situ assessment of pancreases by NR is promising, and that HMPO2 may be better than SCS.

Targeting neutrophil extracellular traps in severe acute pancreatitis treatment

Severe acute pancreatitis (SAP) is a critical abdominal disease associated with high death rates. A systemic inflammatory response promotes disease progression, resulting in multiple organ dysfunction. The functions of neutrophils in the pathology of SAP have been presumed traditionally to be activation of chemokine and cytokine cascades accompanying the inflammatory process. Recently, since their discovery, a new type of antimicrobial mechanism, neutrophil extracellular traps (NETs), and their role in SAP, has attracted widespread attention from the scientific community. Significantly different from phagocytosis and degranulation, NETs kill extracellular microorganisms by releasing DNA fibers decorated with granular proteins. In addition to their strong antimicrobial functions, NETs participate in the pathophysiological process of many noninfectious diseases. In SAP, NETs injure normal tissues under inflammatory stress, which is associated with the activation of inflammatory cells, to cause an inflammatory cascade, and SAP products also trigger NET formation. Thus, due to the interaction between NET generation and SAP, a treatment targeting NETs might become a key point in SAP therapy. In this review, we summarize the mechanism of NETs in protecting the host from pathogen invasion, the stimulus that triggers NET formation, organ injury associated with SAP involving NETs, methods to interrupt the harmful effects of NETs, and different therapeutic strategies to preserve the organ function of patients with SAP by targeting NETs.

Biliary Stricture after Necrotizing Pancreatitis: An Underappreciated Challenge

OBJECTIVE

Biliary stricture in necrotizing pancreatitis (NP) has not been systematically categorized; therefore, we sought to define the incidence and natural history of biliary stricture caused by NP.

SUMMARY/BACKGROUND DATA

Benign biliary stricture occurs secondary to bile duct injury, anastomotic narrowing, or chronic inflammation and fibrosis. The profound loco-regional inflammatory response of NP creates challenging biliary strictures.

METHODS

NP patients treated between 2005-2019 were reviewed. Biliary stricture was identified on cholangiography as narrowing of the extrahepatic biliary tree to < 75% of the diameter of the unaffected duct. Biliary stricture risk factors and outcomes were evaluated.

RESULTS

Among 743 NP patients, 64 died, 13 were lost to follow up; therefore, a total of 666 patients were included in the final cohort. Biliary stricture developed in 108 (16%) patients. Mean follow up was 3.5 ± 3.3 years. Median time from NP onset to biliary stricture diagnosis was 4.2 months (IQR, 1.8-10.9). Presentation was commonly clinical or biochemical jaundice, n = 30 (28%) each. Risk factors for stricture development were splanchnic vein thrombosis and pancreatic head parenchymal necrosis. Median time to stricture resolution was 6.0 months after onset (2.8-9.8). A mean of 3.3 ± 2.3 procedures were performed. Surgical intervention was required in 22 (20%) patients. Endoscopic treatment failed in 17% (17/99) of patients and was not associated with stricture length. Operative treatment of biliary stricture was more likely in patients with infected necrosis or NP disease duration ≥6 months.

CONCLUSION

Biliary stricture occurs frequently after necrotizing pancreatitis and is associated with splanchnic vein thrombosis and pancreatic head necrosis. Surgical correction was performed in 20%.

Low-methoxyl lemon pectin attenuates inflammatory responses and improves intestinal barrier integrity in caerulein-induced experimental acute pancreatitis

SCOPE

Acute pancreatitis (AP) is a common clinical acute abdominal disease. The intestinal injury associated with AP will aggravate the condition retroactively. This study investigates whether the low-methoxyl pectin (LMP) isolated from lemon could attenuate AP and associated intestinal injury.

METHODS AND RESULTS

Experimental AP was induced in BALB/c mice by caerulien (CAE) hyperstimulation. Nutritional prophylactic group was pre-fed with 5% LMP supplemented forage 3 days before AP induction. We found that LMP supplementation attenuated the severity of AP as evidenced by reduced serum amylase and lipase levels, pancreatic edema and myeloperoxidase activity. The protective effect was also confirmed by histological examination of pancreatic damage. LMP suppressed the production of pancreatic proinflammatory cytokines including TNF-α, IL-1β, and IL-6. Moreover, LMP supplementation restored AP-associated disruption of intestinal barrier integrity as evidenced by upregulation of tight junction modulatory proteins occludin, zonula occludens (ZO)-1, antimicrobial peptides β-defensin-1 (DEFB1) and CRAMP as well as increase in SCFAs production. LMP supplemented mice with AP exhibited suppressed intestinal inflammation as shown by decreased ileal and colon cytokine production compared with CAE group.

CONCLUSION

Our results support dietary LMP supplementation as an effective nutritional intervention for AP and associated intestinal injury.

Diffusion tensor magnetic resonance imaging of the pancreas

PURPOSE

To develop a diffusion-tensor-imaging (DTI) protocol that is sensitive to the complex diffusion and perfusion properties of the healthy and malignant pancreas tissues.

MATERIALS AND METHODS

Twenty-eight healthy volunteers and nine patients with pancreatic-ductal-adenocacinoma (PDAC), were scanned at 3T with T2-weighted and DTI sequences. Healthy volunteers were also scanned with multi-b diffusion-weighted-imaging (DWI), whereas a standard clinical protocol complemented the PDAC patients' scans. Image processing at pixel resolution yielded parametric maps of three directional diffusion coefficients λ1, λ2, λ3, apparent diffusion coefficient (ADC), and fractional anisotropy (FA), as well as a λ1-vector map, and a main diffusion-direction map.

RESULTS

DTI measurements of healthy pancreatic tissue at b-values 0,500 s/mm² yielded: λ1 = (2.65±0.35)×10⁻³, λ2 = (1.87±0.22)×10⁻³, λ3 = (1.20±0.18)×10⁻³, ADC = (1.91±0.22)×10⁻³ (all in mm²/s units) and FA = 0.38±0.06. Using b-values of 100,500 s/mm² led to a significant reduction in λ1, λ2, λ3 and ADC (p<.0001) and a significant increase (p<0.0001) in FA. The reduction in the diffusion coefficients suggested a contribution of a fast intra-voxel-incoherent-motion (IVIM) component at b≤100 s/mm², which was confirmed by the multi-b DWI results. In PDACs, λ1, λ2, λ3 and ADC in both 0,500 s/mm² and 100,500 s/mm² b-values sets, as well as the reduction in these diffusion coefficients between the two sets, were significantly lower in comparison to the distal normal pancreatic tissue, suggesting higher cellularity and diminution of the fast-IVIM component in the cancer tissue.

CONCLUSION

DTI using two reference b-values 0 and 100 s/mm² enabled characterization of the water diffusion and anisotropy of the healthy pancreas, taking into account a contribution of IVIM. The reduction in the diffusion coefficients of PDAC, as compared to normal pancreatic tissue, and the smaller change in these coefficients in PDAC when the reference b-value was modified from 0 to 100 s/mm², helped identifying the presence of malignancy.

N-acetylcysteine improves pancreatic microcirculation and alleviates the severity of acute necrotizing pancreatitis

Background/Aims

To investigate the beneficial effect of N-Acetylcysteine (NAC) on pancreatic microvascular perfusion in acute necrotizing pancreatitis (ANP).

Methods

Fifty-four rats were divided into a control group, an ANP group and an NAC-treated group. The ANP model was established by a retrograde injection of 3% sodium taurocholate into the pancreatic duct. The NAC-treated group received an intravenous infusion of NAC just 2 hours before and 30 minutes after the induction of ANP. The pancreatic microvascular perfusion was measured with laser Doppler flowmetry and pancreatic samples were collected for histological examination.

Results

The microvascular perfusion in the NAC-treated group decreased slightly and exhibited a significant increase compared to the ANP group (p<0.01). A pathological examination revealed that edema and inflammatory infiltration decreased, and the hemorrhaging and necrosis of the pancreas were significantly reduced.

Conclusions

NAC could improve pancreatic microvascular perfusion and alleviate the severity of sodium taurocholate-induced ANP, possibly representing a new therapeutic approach to prevent the progression of ANP.

Protective effects of edaravone against acute necrotizing pancreatitis in rats

AIM: To investigate whether edaravone has protective effects against acute necrotizing pancreatitis (ANP) in rats and to explore the possible mechanisms involved.

METHODS: Ninety male Spraque-Dawley rats were randomly and equally divided into sham operation group, ANP group and edaravone treatment group (EDA group). ANP was induced in rats of the ANP and EDA groups by retrograde injection of 1.5% deoxycholate. The EDA group was injected with edaravone (6 mg/kg) via the tail vein immediately after ANP induction. The rats were sacrificed 6, 12, and 24 h after the operation. Pathological changes in the pancreas were observed and graded. Serum levels of amylase, tumor necrosis factor-alpha (TNF-α), endothelin-1 (ET-1) and soluble intercellular adhesion molecule-1 (sICAM-1), as well as malonic dialdehyde (MDA) content and superoxide dismutase (T-SOD) activity in pancreatic tissue were measured.

RESULTS: Compared to the sham operation group, pancreatic pathological scores, serum levels of amylase, TNF-α, ET-1 and sICAM-1, and the contents of MDA in pancreatic tissue were significantly increased, and T-SOD activity in pancreatic tissue was significantly decreased in the ANP group. Compared to the ANP group, pancreatic pathological scores, serum levels of TNF-α (6 h: 109.6 ng/L ± 49.0 ng/L vs 190.2 ng/L ± 46.6 ng/L, 12 h: 405.4 ng/L ± 116.3 ng/L vs 559.7 ng/L ± 203.9 ng/L, 24 h: 415.4 ng/L ± 164.6 ng/L vs 648.7 ng/L ± 222.1 ng/L, all P < 0.05), ET-1 (6 h: 45.6 ng/L ± 13.5 ng/L vs 66.0 ng/L ± 16.0 ng/L, 12 h: 83.5 ng/L ± 15.4 ng/L vs 96.8 ng/L ± 23.0 ng/L, 24 h: 85.1 ng/L ± 25.8 ng/L vs 103.9 ng/L ± 28.9 ng/L, all P < 0.05), and sICAM-1 (6 h: 0.58 ng/L ± 0.13 ng/L vs 0.78 ng/L ± 0.14 ng/L, 12 h: 0.78 ng/L ± 0.10 ng/L vs 0.94 ng/L ± 0.12 ng/L, 24 h: 0.96 ng/L ± 0.16 ng/L vs 1.24 ng/L ± 0.30 ng/L, all P < 0.05), and the contents of MDA in pancreatic tissue (6 h: 4.22 nmol/mgprot ± 0.40 nmol/mgprot vs 8.79 nmol/mgprot ± 0.80 nmol/mgprot, 12 h: 5.90 nmol/mgprot ± 0.51 nmol/mgprot vs 12.30 nmol/mgprot ± 1.02 nmol/mgprot, 24 h: 9.10 nmol/mgprot ± 0.84 nmol/mgprot vs 17.88 nmol/mgprot ± 1.43 nmol/mgprot, all P < 0.05) were reduced, and T-SOD activity was increased (6 h: 88.6 U/mgprot ± 7.1 U/mgprot vs 68.8 U/mgprot ± 10.5 U/mgprot, 12 h: 77.6 U/mgprot ± 6.8 U/mgprot vs 46.0 U/mgprot ± 8.9 U/mgprot, 24 h: 45.5 U/mgprot± 5.3 U/mgprot vs 27.8 U/mgprot ± 4.3 U/mgprot, all P < 0.05) in the EDA group. No significant differences were observed in serum levels of amylase between the ANP and EDA groups.

CONCLUSION: Edaravone can eliminate the excessive generation of oxygen free radicals, down-regulate the expression of inflammatory cytokines, and reduce tissue injury in rats with ANP.

Cardiovascular manifestations of acute pancreatitis

Acute pancreatitis (AP) is an acute inflammatory process of the pancreas that is associated with variable involvement of pancreatic/peripancreatic tissue and one or more organ systems in varying degrees. Among the multiple organ system dysfunctions in severe AP, cardiovascular and/or pulmonary manifestations are frequent. The cardiovascular system may be affected alone or with other organ systems in all stages of AP. Abnormalities of cardiac rhythm, contractility, and vasomotor tone of peripheral vessels are common cardiovascular manifestations. The pathogenetic factors of cardiac manifestations include hypovolemia and metabolic disturbances (eg, hyperkalemia, hypomagnesemia, and hypophosphatemia). Clinically, patients present with hypotension, tachycardia, and signs of systemic inflammatory response syndrome (high cardiac index, significant pulmonary shunting, decreased systemic vascular resistance, and decreased myocardial contractility). Approximately 50% of patients with AP have electrocardiographic changes, most commonly T-wave flattening and ST-segment depression. Many of the cardiac manifestations in AP are reversible with appropriate management. In AP, early onset of either multi-organ dysfunction or a sustained single-organ dysfunction is associated with poor outcome. This review highlights cardiac manifestations of AP relevant to clinical practice.

Differential effects of endothelins on histological and ultrastructural changes and trypsinogen activation in the secretagogue-induced acute pancreatitis in rats

The role of endothelins in acute pancreatitis remains obscure. To assess the effects of endothelins (ETs) in early (4 h) caerulein-induced acute pancreatitis (AP) in rats, ET-1, ET-2 and ET-3 (0.5 or 1.0 nmol/kg) were applied twice with i.p. caerulein (2×40 μg/kg) at 1h interval. Histological and ultrastructural examinations of pancreases and the assay of trypsinogen activation in whole homogenate were performed. All ETs, especially ET-1 at the higher dose, decreased inflammatory cell infiltration despite an increase in the edema score. The vacuolization and necrosis of acinar cells were slightly increased after the lower dose of ET-1 and ET-2. Ultrastructural changes were generally improved after the higher dose of ETs. Trypsinogen activation increased from 4.8±1.3% in control to 18.4±3.8% in AP (p<0.01). It was attenuated to 6.4±1.3% (p<0.01) by the higher dose of ET-1 and to 8.8±1.5% (p<0.05) by the lower dose of ET-3. In summary, ETs, especially ET-1 at the higher dose, were found to have some beneficial effects on morphological changes and trypsinogen activation in the pancreas in early caerulein-induced AP.

Acute edematous and necrotic pancreatitis in a porcine model

OBJECTIVE

It is unclear why pancreatitis progresses either to mild edematous disease or to severe necrotic disease. The aim of the study was to shed some light on this topic by investigating differences during the early stages of necrotic and edematous pancreatitis.

MATERIAL AND METHODS

Piglets were randomized into two groups. Necrotic pancreatitis was induced with retrograde injection of 20% taurocholic acid (1 ml/kg), and edematous pancreatitis was induced with 0.9% NaCl (1 ml/kg). Central hemodynamics was measured, and pancreatic microcirculation was directly examined by intravital microscopy. Vascular permeability to proteins and albumin was measured by microdialysis. Apoptosis and claudins 2, 3, 4, 5, and 7 were analyzed from pancreatic tissue samples. Blood samples were taken for analysis of blood cell counts, blood gases, lipase, and amylase.

RESULTS

Hemodynamic changes were similar in both groups, whereas microcirculatory impairment was more pronounced in necrotic pancreatitis. Necrosis was associated only with necrotic pancreatitis. Apoptosis increased only in edematous pancreatitis. The number of blood neutrophils and monocytes increased and lymphocyte and platelet counts decreased in both groups. Necrotic pancreatitis was associated with increased permeability to albumin and proteins. Expression of claudins 3, 4, 5, and 7 was not changed during pacreatitis, but in acinar cells, membranous expression of claudin-2 increased in both groups.

CONCLUSIONS

The results show that acute edematous pancreatitis is characterized by induction of apoptosis, whereas full-blown pancreatitis is characterized by necrosis. Impaired vascular permeability to albumin and protein is related to the early phase of necrotic pancreatitis. Claudin-2 increases during acute necrotic and edematous pancreatitis and may be related to impaired permeability.

Hyperbaric oxygen improves capillary morphology in severe acute pancreatitis

OBJECTIVES

This article aims to determine the effect of acute pancreatitis on microvascular morphology and the impact of treatment with hyperbaric oxygen (HBO).

METHODS

Sixty-seven male Wistar rats were induced with acute pancreatitis by retrograde bile duct injection. Rats were randomized to 12-hourly HBO or control treatment. Two rats in each group were killed at baseline and 24, 48, and 72 hours postinduction, and a cast of the pancreatic microvasculature was examined using scanning electron microscopy.

RESULTS

Normal pancreatic vasculature is a dense network with a consistent capillary diameter. In acute pancreatitis, mean capillary diameter is increased at 24 hours (P < 0.001) and further increased at 48 hours (P = 0.007). From 24 hours, diameter heterogeneity is increased (P < 0.001) and capillary density is reduced (P < 0.001). Hyperbaric oxygen has a significant effect on vascular morphology changes from 48 hours after induction. Capillary diameter and heterogeneity of diameter are decreased by HBO (both P < 0.001). Capillary density is increased by HBO at 48 and 72 hours (P < 0.001).

CONCLUSIONS

In acute pancreatitis, structural capillary diameter and heterogeneity of diameter increase and capillary density decreases. These parameters are all improved by HBO treatment. Hyperbaric oxygen treatment normalizes the pancreatic microvasculature after acute pancreatitis and may be a potentially effective treatment of this disease.

Mechanism of acute pancreatitis complicated with injury of intestinal mucosa barrier

Acute pancreatitis (AP) is a common acute abdomen in clinic with a rapid onset and dangerous pathogenetic condition. AP can cause an injury of intestinal mucosa barrier, leading to translocation of bacteria or endotoxin through multiple routes, bacterial translocation (BT), gut-origin endotoxaemia, and secondary infection of pancreatic tissue, and then cause systemic inflammatory response syndrome (SIRS) or multiple organ dysfunction syndrome (MODS), which are important factors influencing AP's severity and mortality. Meanwhile, the injury of intestinal mucosa barrier plays a key role in AP's process. Therefore, it is clinically important to study the relationship between the injury of intestinal mucosa barrier and AP. In addition, many factors such as microcirculation disturbance, ischemic reperfusion injury, excessive release of inflammatory mediators and apoptosis may also play important roles in the damage of intestinal mucosa barrier. In this review, we summarize studies on mechanisms of AP.

From acute pancreatitis to end-organ injury: mechanisms of acute lung injury

BACKGROUND

Multi-organ dysfunction, and in particular lung injury, is often responsible for the unfavorable outcome of patients with severe acute pancreatitis. Understanding of the mechanisms by which local inflammation in the pancreas leads to end-organ injury is crucial for the development of new therapeutic strategies.

METHODS

A MEDLINE search was performed with the terms "acute pancreatitis," "lung injury," "inflammatory response," "SIRS," and "multi-organ dysfunction." Pertinent articles were selected for analysis.

RESULTS

Modulation of the inflammatory response using a combination of immunomodulatory agents may decrease the incidence of severe pancreatitis-related acute lung injury and acute respiratory distress syndrome.

CONCLUSION

Clinical trials are of utmost importance to establish the validity of such strategies.

Hyperbaric oxygen therapy reduces severity and improves survival in severe acute pancreatitis

Severe acute pancreatitis is characterized by pancreatic necrosis, resulting in local and systemic inflammation. Hyperbaric oxygen (HBO) therapy modulates inflammation, but has not been extensively studied in pancreatitis. This study investigates the effects of HBO in a rat model of severe acute pancreatitis. Sixty-four rats were induced with severe pancreatitis using 4% sodium taurocholate and randomized to HBO treatment or control. HBO was commenced 6 h after induction (100% oxygen at 2.5 atmospheres for 90 min) and continued every 12 h for a maximum of eight treatment episodes. Surviving animals were killed at 7 days. Severity of pancreatitis was graded macroscopically and microscopically. Lung edema was calculated using wet and dry lung weights. Macroscopic and microscopic severity scores (mean +/- SE) of HBO-treated animals with pancreatitis (8.3 +/- 0.7; 9.6 +/- 0.4) were lower than those of controls (10.5 +/- 0.5; 11.1 +/- 0.4) (p = 0.02 and p = 0.03, respectively). The HBO-treated group had reduced pancreatic necrosis compared to controls (40 +/- 4% vs. 54 +/- 4%; p = 0.003). There was no difference in pulmonary edema between the groups. Median survival in the HBO-treatment group was 51 h, compared to 26 h in controls. Day-7 survival was significantly improved in the HBO-treated animals compared to controls (40% vs. 27%; p = 0.04). HBO therapy reduces overall severity, decreases the extent of necrosis, and improves survival in severe acute pancreatitis.

Acute interstitial edematous pancreatitis: Findings on non-enhanced MR imaging

AIM: To study the appearances of acute interstitial edematous pancreatitis (IEP) on non-enhanced MR imaging.

METHODS: A total of 53 patients with IEP diagnosed by clinical features and laboratory findings were underwent MR imaging. MR imaging sequences included fast spoiled gradient echo (FSPGR) fat saturation axial T1-weighted imaging, gradient echo T1-weighted (in phase), single shot fast spin echo (SSFSE) T2-weighted, respiratory triggered (R-T) T2-weighted with fat saturation, and MR cholangiopancreatography. Using the MR severity score index, pancreatitis was graded as mild (0-2 points), moderate (3-6 points) and severe (7-10 points).

RESULTS: Among the 53 patients, IEP was graded as mild in 37 patients and as moderate in 16 patients. Forty-seven of 53 (89%) patients had at least one abnormality on MR images. Pancreas was hypointense relative to liver on FSPGR T1-weighted images in 18.9% of patients, and hyperintense in 25% and 30% on SSFSE T2-weighted and R-T T2-weighted images, respectively. The prevalences of the findings of IEP on R-T T2-weighted images were, respectively, 85% for pancreatic fascial plane, 77% for left renal fascial plane, 55% for peripancreatic fat stranding, 42% for right renal fascial plane, 45% for perivascular fluid, 40% for thickened pancreatic lobular septum and 25% for peripancreatic fluid, which were markedly higher than those on in-phase or SSFSE T2-weighted images (P < 0.001).

CONCLUSION: IEP primarily manifests on non-enhanced MR images as thickened pancreatic fascial plane, left renal fascial plane, peripancreatic fat stranding, and peripancreatic fluid. R-T T2-weighted imaging is more sensitive than in-phase and SSFSE T2-weighted imaging for depicting IEP.

Potential effects of hyperbaric oxygen therapy in acute pancreatitis

BACKGROUND

To extract from the biomedical published reports, the effects of hyperbaric oxygen (HBO) on inflammatory disease, in particular acute pancreatitis.

METHODS

This review will explain these effects and evaluate potential mechanisms of action of HBO in acute pancreatitis. A Medline/PubMed search (January 1966 to July 2004) with manual cross-referencing was conducted, including all relevant articles investigating the molecular and systemic effects of HBO on inflammatory diseases, particularly focusing on the studies of acute pancreatitis. All publication types, languages and subsets were searched.

RESULTS

Original and review articles and short communications were extracted. The selected original articles covered the molecular and systemic effects of HBO and the effects in inflammatory disease states. The major findings are that HBO can act as an anti-inflammatory agent and as an antimicrobial agent. Many of the effects of HBO would be beneficial in the treatment of acute severe pancreatitis. Work carried out to date in animal models of acute pancreatitis shows promising improvements in severity but studies are limited to date.

CONCLUSION

Acute pancreatitis impairs the pancreatic and systemic microcirculation and causes acute inflammation. These processes are potentially improved by HBO therapy.

Captopril, an Angiotensin-converting enzyme inhibitor, attenuates the severity of acute pancreatitis in rats by reducing expression of matrix metalloproteinase 9

It has been reported that matrix metalloproteinase 9 (MMP-9) disrupts basement membrane and increases vascular permeability. MMP-9 therefore might participate in the pathogenesis of severe acute pancreatitis (SAP). Captopril, an angiotensin-converting enzyme inhibitor, could reduce MMP-9 expression. However, the effect of captopril on the outcome of SAP is not ascertained. The aim of this study was to determine whether captopril attenuates the severity of SAP by reducing MMP-9 expression. Thirty Sprague-Dawley rats were randomly divided into 3 groups (n = 10 for each). Rats were given intraperitoneal injection of saline (SAP group) or captopril (4 mg/kg) (treated group), and then given retrograde infusion of 5% sodium taurocholate (1.5 ml/kg) into the pancreatic duct under laparotomy to induce SAP. One group of rats, injected with saline, underwent only sham operation (Control). Experimental samples were collected at 24 hrs after the induction of SAP or sham operation. Various markers of severity of SAP, such as serum levels of amylase and trypsinogen activation peptide and the vascular permeability, were increased in rats with SAP, but were significantly decreased in captopril-treated rats (p < 0.01). Likewise, the serum MMP-9 levels and expression levels of pancreatic tissue MMP-9 were significantly higher in rats with SAP than those in captopril-treated rats and control rats (p < 0.01 for both parameters), but showed no difference between captopril-treated and control rats. These results suggest that captopril may attenuate vascular permeability by reducing MMP-9 expression in SAP, thereby ameliorating severity of the disease. The use of captopril might become a new therapeutic agent for SAP.

Disturbances of the microcirculation in acute pancreatitis

BACKGROUND

Severe acute pancreatitis is characterized by pancreatic necrosis, resulting in local and systemic inflammation. Pancreatitis affects both the systemic and pancreatic vasculature. This review focuses on the underlying processes involved in the changes of microvascular anatomy following acute pancreatitis.

METHODS

A Medline/PubMed search (January 1966 to December 2005) with manual cross-referencing was conducted. All relevant articles investigating the pancreatic microcirculatory anatomy and the effect of pancreatitis on the microcirculation were included.

RESULTS

The pancreas is susceptible to ischaemic insult, which can exacerbate acute pancreatitis. There is also increasing evidence of pancreatic and systemic microvascular disturbances in the pathogenesis of pancreatitis, including vasoconstriction, shunting, inadequate perfusion, and increased blood viscosity and coagulation. These processes may be caused or exacerbated by ischaemia-reperfusion injury and the development of oxygen-derived free radicals.

CONCLUSION

Acute pancreatitis impairs the pancreatic and systemic microcirculation, which is a key pathological process in the development of severe necrotizing disease.

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Pancreatic proteases in serum induce leukocyte-endothelial adhesion and pancreatic microcirculatory failure

BACKGROUND

Neutrophil-mediated tissue injury in acute pancreatitis includes a severe reduction of the functional microcirculation via interaction of adhesion molecules on leukocytes (MAC-1) and endothelium (ICAM-1). The hypothesis of the study was that trypsin and elastase in serum alone lead to the expression of these complementary adhesion molecules and result in increased leukocyte-endothelial interaction (LEI). In addition we evaluated the preventative benefit of protease inhibition on these mechanisms.

MATERIALS AND METHODS

In vitro: Cultured endothelial cells (HUVEC) and human leukocytes (PMN) were stimulated with increasing doses of trypsin and elastase. In addition, pre-treatment of PMN or HUVEC was performed with protease inhibitors (Nafamostat mesilate, FUT and gabexate mesilate, FOY). The expression of ICAM-1 or MAC-1 was evaluated by flow cytometry. In vivo: Severe pancreatitis was induced in rats. Microcirculatory disturbances were evaluated by real-time confocal microscopy at 9 h in controls and acute pancreatitis with or without anti-protease treatment. Additionally, the effect of continuous trypsin and elastase infusion on pancreatic microcirculation and LEI were evaluated by intravital fluorescence videomicroscopy.

RESULTS

Up-regulation of MAC-1 and ICAM-1 expression requires the presence of serum. The maximal increase of MAC-1 and ICAM-1 expression was found at concentrations of trypsin or elastase characteristic for acute pancreatitis. FUT or FOY significantly reduced protease-induced expression of MAC-1 and ICAM-1. Real-time in-vivo microscopy revealed that functional capillary density in acute pancreatitis was significantly reduced (267.1 +/- 2.95/mm2 vs. 91.29 +/- 12.81/mm2) and treatment with FUT significantly reduced this effect (134.6 +/- 4.6/mm2; p < 0.05 vs. untreated pancreatitis). Infusion of trypsin or elastase alone increased LEI in vivo and reduced pancreatic perfusion.

CONCLUSION

Both trypsin and elastase up-regulate the expression of adhesion molecules on leukocytes and endothelial cells in the presence of serum. Increased LEI and reduced perfusion of the pancreas, characteristic of acute pancreatitis, is induced in vivo by infusion of pancreatic proteases and this effect is partially abrogated by their inhibitors. These results support the role of circulating trypsin and elastase in promoting pancreatic microcirculatory failure in experimental acute pancreatitis.

A new experimental pancreatitis by incomplete closed duodenal loop: the influence of pancreatic microcirculation on the development and progression of induced severe pancreatitis in rats

OBJECTIVES

We developed a new model of reversible pancreatitis, as an incomplete closed duodenal loop (ICDL) model. This permitted us to demonstrate the process of progressing severity of pancreatitis and the influence of tissue microcirculation impairment on the morphologic changes of pancreatitis.

METHODS

An ICDL model was prepared in Wistar rats according to the following procedure. The duodenum was ligated over half its circumference at 2 cm on either side of the duodenal entry of the biliopancreatic duct.

RESULTS

The pancreatic wet weight ratio in the ICDL was higher than that of the control after model preparation. The survival rate in the ICDL group was significantly longer than that in the CDL group. Blood flow in the pancreas and duodenal loop decreased over time after model preparation, and the decline in ICDL occurred and remained at a plateau in chronic pancreatitis phase. Histopathologic alterations of the pancreas in the ICDL group consisted of edema, parenchymal necrosis, thrombosis, and hemorrhage. From 1 week onward, periductal fibrosis spread to the parenchyma, the regenerative activity of the acinar cell presenting the clinical features of chronic pancreatitis.

CONCLUSION

Impairment of microcirculation due to tissue ischemia played a role in the increasing severity of pancreatitis.

Clinical characteristics and management of patients with early acute severe pancreatitis: Experience from a medical center in China

AIM: To study clinical characteristics and management of patients with early severe acute pancreatitis (ESAP).

METHODS: Data of 297 patients with severe acute pancreatitis (SAP) admitted to our hospital within 72 h after onset of symptoms from January 1991 to June 2003 were reviewed for the occurrence and development of early severe acute pancreatitis (ESAP). ESAP was defined as presence of organ dysfunction within 72 h after onset of symptoms. Sixty-nine patients had ESAP, 228 patients without organ dysfunction within 72 h after onset of symptoms had SAP. The clinical characteristics, incidence of organ dysfunction during hospitalization and prognosis between ESAP and SAP were compared.

RESULTS: Impairment degree of pancreas (Balthazar CT class) in ESAP was more serious than that in SAP (5.31 ± 0.68 vs 3.68 ± 0.29, P < 0.01). ESAP had a higher mortality than SAP (43.4% vs 2.6%, P < 0.01), and a higher incidence of hypoxemia (85.5% vs 25%, P < 0.01), pancreas infection (15.9% vs 7.5%, P < 0.05), abdominal compartment syndrome (ACS) (78.3% vs 23.2%, P < 0.01) and multiple organ dysfunction syndrome (MODS)(78.3% vs 10.1%, P < 0.01). In multiple logistic regression analysis, the main predisposing factors to ESAP were higher APACHE II score, Balthazar CT class, MODS and hypoxemia.

CONCLUSION: ESAP is characterised by MODS, severe pathological changes of pancreas, early hypoxemia and abdominal compartment syndrome. Given the poor prognosis of ESAP, these patients should be treated in specialized intensive care units with special measures such as close supervision, fluid resuscitation, improvement of hypoxemia, reduction of pancreatic secretion, elimination of inflammatory mediators, prevention and treatment of pancreatic infections.

Caerulein-induced pancreatitis and islet blood flow in anesthetized rats

BACKGROUND

Microcirculatory mechanisms have been suggested to be involved in the development of acute pancreatitis. Islet blood flow has not previously been studied in this disease. The present study aimed to investigate the effects of caerulein-induced pancreatitis on pancreatic blood perfusion, especially islet blood flow.

MATERIALS AND METHODS

Continuous 4 h caerulein-infusion was used to induce mild, edemateous pancreatitis in anesthetized Sprague-Dawley rats. Some animals were then given an additional 2 h infusion of saline. Thus, at 4 or 6 h after initiating caerulein infusion the blood flow to the pancreas, pancreatic islets, and intestines was measured with a microsphere technique.

RESULTS

All infused animals demonstrated an edemateous pancreatitis, without hemorrhages. Both total pancreatic and islet blood flow was increased after the 4-h infusion. However, the increase was less pronounced in the islets. After an additional 2 h with only saline infused, the blood flow values in rats initially infused with caerulein were lower than at 4 h, but total pancreatic blood was still higher than in control rats. No effects on intestinal blood flow values were seen.

CONCLUSIONS

Pancreatic islet blood flow in rats with mild edematous pancreatitis is increased, but not to the same extent as that in the whole pancreas.

Hemorrhagic shock resuscitation with a low molecular weight starch reduces neutrophil-endothelial interactions and vessel leakage in vivo

BACKGROUND

The polymorphonuclear neutrophil (PMN) has been implicated in the pathogenesis of endothelial cell (EC) damage and organ injury following hemorrhagic shock. Pentastarch (PTS), a low substituted medium molecular weight (MW) colloid, improves hemodynamics in hypovolemic shock and cardiac surgery. No data exist comparing the immunomodulation of PTS and Ringer's lactate (RL) on the activation of PMN in hemorrhagic shock in vivo.

METHODS

Using an in vivo murine hemorrhagic shock model (blood withdrawal to maintain 50 mmHg x 45 min), circulating PMN were observed every 15 minutes using intravital microscopy on cremaster muscle. EC-PMN interactions (videorecorded and subsequently analyzed blindly), vessel leakage (live epifluorescence after injection of 50 mg/kg fluorescent albumin) and PMN expression of L-selectin (immunofluorescent monoclonal antibodies and flow cytometry) were evaluated in three resuscitation groups: PTS (7.14 mL/kg 10% pentastarch/0.9% NaCl + shed blood, n = 13), RL (RL [2 x shed blood volume] + shed blood, n = 13) and SHAM (0 hemorrhage, 0 resuscitation, n = 9). Significance was evaluated by ANOVA with Bonferroni correction.

RESULTS

PMN rolling was significantly diminished in PTS and SHAM as compared to RL animals at all time points. Similar differences were found in PMN adherence to EC at most time points onwards from 15 minutes following resuscitation. In vivo vessel permeability was lowest in SHAM and PTS animals (mean 0.274 +/- 0.07 and 0.356 +/- 0.15, respectively, p > 0.05) and highest in RL animals (0.667 +/- 0.09, p < 0.001 vs PTS or SHAM). PMN L-selectin expression tended to be higher in the RL group than either SHAM and PTS groups. There were no flow-mechanics differences between groups (vessel diameter, mean red cell velocity, shear stress, shear rate).

CONCLUSIONS

10% pentastarch reduces RL-associated EC-PMN interactions and vessel leakage following hemorrhagic shock. These results support the use of low MW starches to resuscitate hemorrhagic shock, potentially reducing PMN-mediated tissue injury.

Pancreatic microcirculatory impairment in experimental acute pancreatitis in rats

AIM: To study the feature of pancreatic microcirculatory impairment, especially the initial changes, in caerulein-induced experimental acute pancreatitis (AP).

METHODS: The pancreatic microcirculation of caerulein-induced AP model was studied by intravital fluorescence microscopy with FITC-labeled erythrocytes (FITC-RBC), scanning electron microscopy of vascular corrosion casts, and light microscopy of Chinese ink-injected/cleared tissues.

RESULTS: Animals in caerulein-treated group showed hyperamylemia (× 2), pancreatic oedema, infiltration of inflammatory cells in pancreas. Constrictions of intralobular arteriolar sphincters, presence of vacuoles in all layers of sphincter, and gross irregularity in capillary network of acini were found in the AP specimens. The decrease of pancreatic capillary blood flow (0.34 ± 0.10 nL·min^-1vs 0.91 ± 0.06 nL·min^-1 of control, P < 0.001), reduction of functional capillary density (277 ± 13 cm^-1vs 349 ± 8 cm^-1 of control, P < 0.001), and irregular intermittent perfusion were observed in caerulein-induced groups.

CONCLUSION: Impairment and constriction of pancreatic intralobular arteriolar sphincter are the initial microcirculatory lesions in the early phase of acute pancreatitis, and play a key role in the pancreatic ischaemia and pancreatic microvascular failure in acute pancreatitis.

Continuous regional application of protease inhibitor in the treatment of acute pancreatitis. An experimental study using closed duodenal obstruction model in dogs

In clinical settings, the effectiveness of protease inhibitors in the treatment of acute pancreatitis has been still controversial. With the concept that sufficient tissue concentration of protease inhibitor in the pancreas has to be included to achieve its potent inhibitory effect, we applied a continuous regional intra-arterial (CRI) application of low-molecular-weight protease inhibitor, nafamostat mesilate (FUT-175), for closed duodenal loop obstruction model in mongrel dogs. The use of CRI application led to a higher concentration of FUT-175 in the pancreatic tissue (4,453 +/- 758 ng/g) when compared with that applied intravenously (905 +/- 48 ng/g). Consequently, pancreatic parenchyma in CRI application animals was remarkably preserved, as assessed by the lower extent of pancreatic necrosis (12.4 +/- 2.6% in CRI vs. 25.6 +/- 1.9% in intravenous). Additionally, the elevation of trypsin-like activity in the pancreas was significantly inhibited in CRI animals. Based on these findings, the dose as well as the route of protease inhibitors should be carefully considered to achieve its beneficial effect.

Pancreatic capillary blood flow in an improved model of necrotizing pancreatitis in the rat

INTRODUCTION

The development of acute pancreatitis is characterized by profound changes in pancreatic microcirculation. Using in vivo microscopy with fluorescent-labeled erythrocytes as tracers we studied changes in pancreatic microcirculation in an improved rat model of necrotizing pancreatitis (NP) in comparison to edematous pancreatitis (EP) and healthy controls.

METHODS

Twenty-one male Wistar rats had their pancreatae exteriorized in a temperature-controlled immersion chamber followed by intravenous administration of fluorescent-labeled autologous erythrocytes. EP was induced by intraductal saline and intravenous caerulein (5 microg/kg/h) for 6 h (n = 7) and NP by controlled intraductal infusion of glycodeoxycholic acid (10 mmol/L) followed by intravenous caerulein (n = 7). Control animals received intraductal and intravenous saline (n = 7). The determination of pancreatic microcirculation was performed before as well as 1, 3, and 6 h after intraductal infusion by correlating the number of passing labeled erythrocytes/capillary/min with their concentration per microliter of arterial blood.

RESULTS

Pancreatic capillary flow in control animals remained constant over the 6-h observation period. Pancreatic capillary flow in the EP group rapidly increased to 188% of baseline after 3 h and remained significantly elevated throughout the experiments (P = 0.0001). In contrast, pancreatic capillary flow decreased significantly in the group suffering NP with values 46.7% of baseline after 6 h (P = 0.0001). Complete capillary stasis developed in 38% of investigated capillaries in the NP group compared to 0-1% in both other groups (P = 0.0001).

CONCLUSION

Pancreatic microcirculation in mild edematous pancreatitis is significantly increased while the evolution of necrotizing pancreatitis in the model studied herein is characterized by a dramatic reduction in pancreatic capillary flow in conjunction with areas of capillary stasis. These results underline the pathophysiologic relevance of the model and of therapeutic measures aimed at an improvement of pancreatic microcirculation in clinical necrotizing pancreatitis.

Influencing factors of pancreatic microcirculatory impairment in acute panceatitis

Pancreatic microcirculatory disturbance plays an important role in the pathogenesis of acute pancreatitis, and it involves a series of changes including vasoconstriction, ischaemia, increased vascular permeability, impairment of nutritive tissue perfusion, ischaemia/reperfusion, leukocyte adherence, hemorrheological changes and impaired lymphatic drainage. Ischaemia possibly acts as an initiating factor of pancreatic microcirculatory injury in acute pancreatitis, or as an aggravating/continuing mechanism. The end-artery feature of the intralobular arterioles suggests that the pancreatic microcirculation is highly susceptible to ischaemia. Various vasoactive mediators, as bradykinin, platelet activating factor, endothelin and nitric oxide participate in the development of microcirculatory failure.

Ultrasonographic splanchnic arterial flow measurement in severe acute pancreatitis

INTRODUCTION

Duplex ultrasonographic technology is now capable of detecting flow signals in the various splanchnic vessels and calculating the concomitant flow velocities using fast-Fourier transformation.

AIM

To use Doppler sonography to investigate how splanchnic hemodynamics vary during the early stage of severe acute pancreatitis.

METHODOLOGY

Six patients with severe acute pancreatitis (age, 59.0 +/- 6.57 years; four men, two women) and seven with mild to moderate acute pancreatitis (age, 60.1 +/- 7.41 years; five men, two women) were examined with Doppler sonography immediately after disease onset. The maximum velocity, minimum velocity, mean velocity, pulsatility index, and resistive index were determined from the Doppler spectra from the proper hepatic artery, celiac artery, and superior mesenteric artery. We also examined 15 healthy subjects (age, 59.3 +/- 4.60 years; 10 men, five women) as controls.

RESULTS

The maximum velocity of the proper hepatic artery in patients with severe acute pancreatitis was significantly higher than that in patients with mild to moderate acute pancreatitis (p = 0.011) and in control subjects (p = 0.0047). Similarly, significant increases in both the minimum velocity and the mean velocity of the proper hepatic artery were observed in patients with severe acute pancreatitis. Neither pulsatility index nor resistive index of the proper hepatic artery showed a significant difference among the three groups. There were no significant differences among the three groups with respect to the flow velocity of the superior mesenteric artery. In contrast, the pulsatility index of the superior mesenteric artery in patients with severe acute pancreatitis was significantly lower than that in patients with mild to moderate acute pancreatitis (p = 0.0058) or in control subjects (p = 0.0024). For patients with acute pancreatitis, a significant inverse correlation was obtained between the maximum velocity of the proper hepatic artery and the pulsatility index of the superior mesenteric artery (r = -0.658, p = 0.0145).

CONCLUSION

The increase in the hepatic arterial flow velocity and the decrease in the superior mesenteric arterial pulsatility index may represent early events of the severe type of acute pancreatitis.