Low molecular weight dextran in experimental pancreatitis: effects on pancreatic microcirculation

Ionic and Non-Ionic Contrast Media Used for Contrast-Enhanced Computed Tomography in Experimental Pancreatitis

Contrast enhancement of the pancreas was studied in pigs using dynamic computed tomography in experimental oedematous and haemorrhagic/necrotizing pancreatitis during the first two minutes after injection of an intravenous bolus of non-ionic contrast medium (iohexol). The prospects of separating the two forms of the disease, known to be possible with ionic contrast media, were tested with a non-ionic contrast medium. In the oedematous form, contrast enhancement after 5 hours of the disease was significantly higher than in the haemorrhagic/necrotizing form. Contrast enhancement after 30 hours of disease tended to vary with the severity of the disease, showing that the course of oedematous pancreatitis is dynamic. Intermediate forms occur and follow-up studies are needed during the disease. A non-ionic contrast medium proved as good for separating the two forms of the disease in the early phase as were ionic contrast media. In severely ill patients, non-ionic contrast media should therefore be used.

Clinical update on fluid therapy and nutritional support in acute pancreatitis

BACKGROUND/OBJECTIVES

The aim of this focused review is to provide a valuable and updated source of information for clinical practice on fluid therapy (FT) and nutritional support in acute pancreatitis (AP).

METHODS

The review encompasses important new clinical information that has become available for understanding and offering these specific treatments since the 2013 publication of two guidelines, both the joint International Association of Pancreatology and American Pancreatic Association and the American College of Gastroenterology. The 2015 Revised Japanese Guideline is discussed selectively. To this end, the review is divided into 7 sections, including timing and cause of mortality; severity classification systems; predicting severity; response to treatment; nutritional support; fluid therapy and steps for further research.

CONCLUSIONS

In mild AP, begin oral feeding when nausea, vomiting and abdominal pain are improving. In (predicted) severe AP, feeding decisions should commence by 72 h, offering oral feeding if GI symptoms improve or enteral feeding if patients are symptomatic and/or intolerant to orals. All patients should be offered goal-directed FT during the first 6-12 h of presentation. Cautious FT is advised in those age >55 years or with preexisting organ failure or predictors of developing fluid sequestration.

Management of acute pancreatitis in dogs: a critical appraisal with focus on feeding and analgesia

Knowledge about acute pancreatitis has increased recently in both the medical and veterinary fields. Despite this expansion of knowledge, there are very few studies on treatment interventions in naturally occurring disease in dogs. As a result, treatment recommendations are largely extrapolated from experimental rodent models or general critical care principles. General treatment principles involve replacing fluid losses, maintaining hydrostatic pressure, controlling nausea and providing pain relief. Specific interventions recently advocated in human medicine include the use of neurokinin-1 antagonists for analgesia and early interventional feeding. The premise for early feeding is to improve the health of the intestinal tract, as unhealthy enterocytes are thought to perpetuate systemic inflammation. The evidence for early interventional feeding is not supported by robust clinical trials to date, but in humans there is evidence that it reduces hospitalisation time and in dogs it is well tolerated. This article summarises the major areas of management of acute pancreatitis in dogs and examines the level of evidence for each recommendation.

Do larger periprocedural fluid volumes reduce the severity of post-endoscopic retrograde cholangiopancreatography pancreatitis?

OBJECTIVE

Fluid therapy is a cornerstone of the early treatment of acute pancreatitis (AP), but data are conflicting on whether it affects disease severity. Administering greater fluid volumes (FVs) during induction of experimental AP preserves pancreatic perfusion and reduces severity but does not prevent onset of AP. We hypothesized that administering larger FV during endoscopic retrograde cholangiopancreatography (ERCP) associates with less severe post-ERCP pancreatitis (PEP).

METHODS

In a retrospective cohort study, we identified 6505 patients who underwent 8264 ERCPs between January 1997 and March 2009; 211 of these patients developed PEP (48 mild, 141 moderate, and 22 severe). Data for FVs were available for 173 patients with PEP.

RESULTS

In univariable analysis, only 1 of 16 variables was significantly associated with moderate to severe PEP--larger periprocedural FV was protective (0.94 T 0.3 L vs 0.81 T 0.4 L; P = 0.0129). Similarly,multivariable analysis of moderate to severe PEP identified 1 independent predictor-- larger periprocedural FV was protective (odds ratio, 0.20; 95% confidence interval, 0.05-0.83). Conversely, moderate to severe disease correlated with larger FV administered after PEP diagnosis(reflecting treatment decisions).

CONCLUSIONS

This hypothesis-generating study suggests that administering larger periprocedural FVs is protective against moderate to severe PEP. Prospective studies on this topic are warranted.

Fluid resuscitation in acute pancreatitis

Acute pancreatitis is a common inflammatory disorder of the pancreas resulting in considerable morbidity and a mortality rate of approximately 5%. Although there are no pharmacologic treatments known to improve important outcomes, aggressive intravenous fluid resuscitation generally is recommended in all patients. However, few human investigations have been performed and several important questions have not been answered. For example, what is the optimal resuscitative fluid? Is there a role for colloid solutions? To what clinical marker should resuscitation be targeted? When is the best time to start such fluids and in which group of patients? This review describes the microcirculation of the pancreas and the pathophysiologic alterations caused by acute pancreatitis. Previous animal experiments are described, as are the limited human studies specifically addressing fluid resuscitation. Finally, current recommendations and goals for further investigation are highlighted. It is our hope that this review will stimulate interest in this often overlooked subject and lead to carefully designed human clinical trials using varying fluid solutions and rates, with an emphasis on patient monitoring and safety, in the near future.

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.

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.

Hyperoncotic dextran and systemic aprotinin in necrotizing rodent pancreatitis

BACKGROUND

Dextrans improve pancreatic microcirculation in acute experimental pancreatitis. They could therefore facilitate the transport of a protease inhibitor to ischemic areas of tissue injury and be of additional benefit.

METHODS

To compare the effects of dextrans with and without aprotinin, necrotizing pancreatitis was induced in 33 male dextran-resistant Wistar rats by intraductal infusion of low-dose glycodeoxycholic acid (10 mmol/l) followed by intravenous cerulein (5 micrograms/kg/h) for 6 h. Three and four hours after the start of the cerulein infusion the animals received infusions of either Ringer's lactate (RL) (12 ml/kg), 70,000 Da dextran (10%) (DEX-70) (4 ml/kg) alone, or DEX-70 (4 ml/kg) with aprotinin (5000 IU/kg) (DEX-70/A).

RESULTS

The death rate was 60% within 9 h in the RL group (6 of 10) but only 10% in the DEX-70 group (1 of 10) (p < 0.03; Fisher's exact test) and 23% in the DEX-70/A group (3 of 13). Histomorphometry demonstrated a significant reduction of acinar necrosis in both treatment groups compared with control animals (p < 0.014; t test). Total amounts of trypsinogen activation peptides (TAP) in ascites were also significantly lower in these groups (p < 0.05; t test).

CONCLUSIONS

DEX-70 given 3 h and 4 h after induction of pancreatitis significantly reduced the levels of TAP, limited acinar necrosis, and improved survival rate in acute necrotizing rodent pancreatitis. There was no additional benefit from the combination with aprotinin.

Impact of microcirculatory flow pattern changes on the development of acute edematous and necrotizing pancreatitis in rabbit pancreas

Impairment of pancreatic microcirculation has often been advocated as one pathogenic mechanism in necrotizing pancreatitis. In contrast, data on pancreatic capillary perfusion in edematous pancreatitis are scarce. It was the aim of this experimental study to compare changes in pancreatic microcirculation in edematous and necrotizing pancreatitis. Twelve rabbits were allocated to two groups. Two different models of acute pancreatitis were used. Edematous pancreatitis was elicited by intravenous administration of cerulein (25 micrograms/kg/hr) (N = 6). Necrotizing pancreatitis of the biliary type was induced by pressure-controlled intraductal infusion of a mixture of taurocholate, trypsin, and blood (N = 6). Pancreatic microcirculation was quantified by means of intravital microscopy assessing functional capillary density, blood cell velocity, and distribution of the plasma marker FITC-dextran 70. Systemic hemodynamics were maintained at baseline values by fluid administration. Regardless of edema or necrosis, pronounced extravasation of FITC-dextran was recorded in the early stage of pancreatitis. In cerulein-induced pancreatitis, hyperemia developed as indicated by an increase in blood cell velocity in the presence of homogeneous capillary perfusion. In contrast, a progressive reduction of the number of perfused capillaries was detected in necrotizing pancreatitis. In conclusion, pancreatic microvascular perfusion may be regarded as an important pathogenetic factor for the determination of acute pancreatitis.

Effect of naloxone on the haemodynamics and the outcome of experimental acute pancreatitis in dogs

Endogenous opioid peptides may play a role in the genesis of pancreatic damage in acute pancreatitis. The effects of naloxone on the haemodynamic changes in acute pancreatitis were investigated by inducing it in dogs with pancreatic ductal injection of fresh trypsin-bile mixture. In the control group (n = 8), acute pancreatitis was characterized haemodynamically by falls in the maximum positive and negative dP/dt (+/- dP/dt), cardiac output (CO) and cardiac index (CI), and increases in the pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) as well as an early reduction of pancreatic blood flow (PBF). In another set of eight dogs (naloxone group), naloxone was given intravenously 10 min after the induction of acute pancreatitis (80 micrograms/kg as a bolus + 80 micrograms/kg/h for 3 h). Compared with untreated dogs, naloxone significantly increased PBF and the +/- dP/dtmax; prevented the significant decreases in CO and CI and increases in PVR and SVR, and reduced significantly the severity of pancreatitis, as assessed by both the histological staging and the mortality rate. These results suggest that naloxone limits the progression of acute pancreatitis from oedematous to haemorrhagic form. It is proposed that endogenous opioid peptides may play a role in the pathophysiology of acute pancreatitis.

Adverse effect of therapeutic vasoconstrictors in experimental acute pancreatitis

Alpha-adrenergic drugs commonly are used to treat hypotension resulting from severe acute pancreatitis. It was shown previously that although systemic arterial pressure is increased by phenylephrine, pancreatic microcirculatory perfusion is decreased. Because inadequate tissue perfusion may be critical in the progression of edematous pancreatitis to parenchymal necrosis, it was hypothesized that vasoconstrictors might be harmful in pancreatitis. Therefore the effect of phenylephrine on cerulein-induced mild pancreatitis were studied. Sprague-Dawley rats (n = 54) were randomly allocated to 6 experimental groups and subjected to the following infusion regimens: (1) cerulein (cae) + phenylephrine (phe), (2) cae + saline (NS), (3) NS + phe, (4) cae + phenoxybenzamine (pbz) + phe, (5) NS + pbz + phe, and (6) NS. Initial and terminal hematocrit, serum amylase activity, and blood ionized calcium concentration were determined. The animals were killed 9 hours after starting the infusion. Macroscopic and histologic changes were scored by a 'blinded' pathologist. Phenylephrine increased the severity of cerulein-induced pancreatitis as manifested by statistically significant adverse changes in serum amylase, hematocrit, ionized calcium, peripancreatitic soap formation, and acinar cell vacuolization. These changes were antagonized by alpha-adrenergic receptor blockade with phenoxybenzamine. It is concluded that phenylephrine is deleterious in acute experimental pancreatitis, the first demonstration of such an effect by a pharmacologic vasoconstrictor, and suggested that microcirculatory changes may be important in the transition of mild to severe pancreatitis. Caution in the use of vasoconstrictor drugs in patients with acute pancreatitis is recommended.

Mechanisms of acute pancreatitis. Vascular etiology

Vascular mechanisms play an important but controversial role in the pathogenesis of acute pancreatitis. In experimental animals, injection of wax, powder, air, mercury, and microspheres into the pancreatic artery causes pancreatitis by end artery occlusion with resulting cellular infarction. Larger microspheres do not cause pancreatitis because collateral blood flow is preserved. Clinical evidence, such as microthrombi and atheromatous emboli in the pancreatic artery of patients with pancreatitis, supports pancreatic infarction as an etiologic agent. Experimental and clinical studies have suggested that pancreatic ischemia may also cause pancreatitis, but these studies have not been conclusive. We have compared five hours of total occlusion of the pancreaticoduodenal artery along with four hours of reperfusion to bile injection into the pancreatic duct as causes of pancreatitis. Bile injection caused a significant increase in serum amylase, activation of trypsin in pancreatic exudate, and histologic evidence of necrotizing pancreatitis. Pancreatic blood flow decreased as pancreatitis developed. Ischemia for five hours did not cause a significant increase in serum amylase or activation of trypsin in pancreatic exudate. Only edema was seen histologically, but there was no necrosis. Pancreatic blood flow increased with reperfusion. We believe ischemia aggravates, but does not initiate pancreatitis. Ischemia does not induce inflammation and necrosis in the pancreas, although infarction does.

Oleic acid induced pancreatitis in pigs

An experimental model of edematous pancreatitis in pigs was established and measurement of pancreatic macro- and microcirculatory parameters and determinations of pancreatic enzymes (lipase, phospholipase A) and vasoactive mediators (prostanoids, kallikrein, kininogen) were performed. During general anesthesia the pancreas was isolated in situ. Pancreatic microcirculatory parameters were measured using videofluorescence microscopy after iv administration of FITC-Dextran. In hourly collected samples lipase and phospholipase A activities were determined enzymatically, concentrations of kallikrein, kininogen, and selected prostanoids were measured by radioimmunoassay. Two experimental groups were studied: (1) control (n = 9); (2) edematous pancreatitis induced by injection of oleic acid into the pancreatic artery (free fatty acid, ffa; n = 10). The animals were followed up for 6 hr. Systemic hemodynamic parameters remained constant in both groups. In the pancreatitis group pancreatic blood flow and O2-consumption decreased significantly (-55 and -49%), while pancreatic vascular resistance increased significantly (+50%). During baseline conditions 41% of all capillaries were perfused. In the pancreatitis group there were both areas with persistent stasis as well as areas with continuous perfusion. However, in the latter areas the portion of perfused capillaries decreased significantly to 27%. In the control group the portion of perfused capillaries remained constant. Liberation of lipase and phospholipase A especially into lymph and ascites fluid was measured during pancreatitis. Furthermore, considerable releases of kallikrein into lymph (+50%) and ascites (+800%) and a marked consumption of kininogen in lymph (+90%) and in ascites fluid (+80%) were measured. Activation of the arachidonic acid cascade and a significant release of prostacyclin and thromboxane A2 into pancreatic venous blood and lymph was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural alterations of pancreatic microvasculature in cerulein-induced pancreatitis in the rat

Pancreatic microvasculature in cerulein-induced pancreatitis was studied at the electron and light microscopic level. Using a modified model of in situ india ink perfusion, focally a marked reduction of the number of india-ink-filled microvessels was found. The numerical density (NA) of filled microvessels was reduced by 66.7% in pancreatitis. The morphological correlate for this extreme numeric reduction might be a collapse of the lumen of pancreatic microvessels. In the presence of cerulein pancreatitis 42% of pancreatic capillaries had a collapsed lumen as shown by electron microscopy. The endothelium of capillaries in acute pancreatitis demonstrated surface blebbing, the formation of cytoplasmatic vacuoles, edema, and swollen mitochondria. Some capillaries had irregularities at the interendothelial junction, and the majority of examined vessels were surrounded by marked perivascular edema. No strict correspondence between histological signs of pancreatitis and light microscopic and/or ultrastructural microvascular alterations could be demonstrated. Our study emphasizes that alterations of microvasculature are present early in experimental edematous pancreatitis. Therefore, alterations of pancreatic microcirculation seem to be of great importance in the pathogenesis of pancreatic inflammation, and should be the subject of further studies.

Pancreatic ischaemia in experimental acute pancreatitis: mechanism, significance and therapy

Much clinical and experimental evidence suggests that pancreatic ischaemia in the early phase of acute pancreatitis is important in the development of pancreatic necrosis. While depletion of intravascular volume has often been assumed to be the main circulatory defect, an additional disturbance of pancreatic microcirculation has been demonstrated experimentally. Possible contributory mechanisms include chemical-induced vasoconstriction, direct injury of vessel wall, intravascular coagulation and increased endothelial permeability resulting in pancreatic oedema, haemoconcentration and impaired venous drainage. Pancreatic ischaemia as a consequence of these local effects seems to be responsible for the transition of mild pancreatitis to parenchymal necrosis. In experimental models the beneficial effect of various drugs and of sympathetic blockade has been ascribed to an improvement in pancreatic perfusion. Although effective volume therapy is generally accepted as the mainstay of conservative treatment in acute pancreatitis, the efficacy of different fluid preparations is still controversial, and simple fluid resuscitation has not been shown to prevent the development of parenchymal necrosis. The specific impairment of pancreatic microcirculation cannot be prevented merely by replenishment of intravascular volume with crystalloids, albumin or plasma despite normalization of macrohaemodynamics. In contrast, partial replacement of blood by dextran preparations has been shown to increase pancreatic perfusion by improving blood fluidity. Isovolaemic haemodilution in conjunction with conventional fluid therapy may provide a new and effective means of protecting the pancreas from secondary injury due to the early ischaemic phase of acute pancreatitis.

Therapeutic effect of isovolemic hemodilution with dextran 60 on the impairment of pancreatic microcirculation in acute biliary pancreatitis

Dextran of different molecular weight (Dx 40, Dx 60/70) has often been evaluated as adjunct treatment of experimental acute pancreatitis. A beneficial effect has been documented by a decrease in its lethality. However, the mechanism of action is poorly understood. A specific effect on the pancreatic microcirculation generally has not been documented and differentiation from unspecific improvement of pancreatic blood flow due to volume expansion has been difficult. This investigation was designed to quantify the effect of dextran on the impairment of pancreatic microcirculation during acute biliary pancreatitis by means of intravital microscopy. Dextran 60 (Dx 60, molecular weight 60,000) was chosen in light of the increase in vascular permeability in the early stage of pancreatitis as demonstrated previously in the same model. Isovolemic hemodilution, i.e., exchange of whole blood for Dx 60 was used as a mode of administration to achieve instantaneous onset of therapy without changes in intravascular volume. In the control group a progressive reduction of pancreatic capillary perfusion commenced 30 minutes after induction of acute pancreatitis, resulting in cessation of nutritive tissue perfusion after 3 hours. In the animals subjected to hemodilution, stabilization of the pancreatic microcirculation was accomplished throughout the observation period of 6 hours. Because volume-related effects could be excluded by the protocol and by monitoring central venous pressure and hematocrit, a specific effect of hemodilution with DX 60 on the pancreatic microcirculation is indicated by our results.

[Pancreatic circulation in experimental biliary pancreatitis]

Measurements of pancreatic micro- and macrocirculation were performed to evaluate the pancreatitis-induced changes. Pigs were anesthetized and ventilated mechanically. Hypotension induced side-effects were avoided by adequate volume replacement. After laparatomy, splenectomy and gastroectomy the animals were enterotomized. Systemic hemodynamic parameters were monitored as well as pancreatic blood flow (Q), which was measured electromagnetically, and arterial and portal-venous blood gases. Pancreatic microcirculatory parameters were observed using fluorescence-videomicroscopy after i.v. administration of FITC dextran 150 and FITC labeled autologous erythrocytes. The pigs were randomly assigned to a control (n = 9) and a pancreatitis group (n = 10), the later being induced by the retrograde infusion of sodium-taurocholate. Systemic and pancreatic macrohemodynamic parameters remained constant in both groups, except for avdO2 and O2-consumption (O2-c) decreasing significantly in the pancreatitis group. At baseline 42% of all capillaries were perfused in both groups. In pancreatitis we detected focal areas with persistent stasis and areas which were continuously perfused. In these areas the portion of capillaries perfused by erythrocytes increased significantly to 67%. This was accompanied by an extravasation of FITC dextran. The finding of an unchanged Q beside reduced O2-c and avdO2 during pancreatitis is explained by the changes in pancreatic microcirculation. Focal stasis was observed beside areas showing typical signs of an acute inflammation: increased macromolecular permeability and capillary recruitment, e.g. oedema and hyperaemia.

Prediction of pancreatic necrosis by dynamic pancreatography

Parenchymal necrosis has recently been recognized as the principal determinant of the incidence of secondary infection in acute pancreatitis. Because secondary infection of pancreatic necrosis accounts for more than 80% of all deaths from acute pancreatitis, a method for determining the presence or absence of parenchymal necrosis would offer considerable prognostic and therapeutic information. Thirty seven patients with unequivocal acute pancreatitis and five normal controls were prospectively studied with intravenous bolus, contrast-enhanced computed tomography (dynamic pancreatography). In the absence of pancreatic necrosis, there were no significant differences in parenchymal enhancement between any of the following patient groups: controls (5), uncomplicated pancreatitis (20), pancreatic abscess (7), or peripancreatic necrosis (4)(p less than 0.05). On the other hand, pancreatic parenchymal enhancement was significantly reduced or absent in all six patients with segmental or diffuse pancreatic necrosis (p less than 0.05). Postcontrast pancreatic parenchymal enhancement was also found to be inversely correlated with the number of Ranson signs (p less than 0.001). Dynamic pancreatography offers prognostic information and is a safe and reliable technique for predicting the presence or absence of pancreatic parenchymal necrosis.

Pancreatic response to crystalloid resuscitation in experimental pancreatitis

Restoration and maintenance of intravascular volume is crucial in acute pancreatitis to prevent hypotension and ensure normal organ perfusion. This study evaluated the hemodynamic and metabolic effects of adequate versus inadequate fluid replacement on the pancreas in a canine model of acute experimental pancreatitis. Bile-trypsin pancreatitis (BTP) was induced in 14 conditioned mongrel dogs. Lactated Ringer's solution was administered intravenously at high (HIR) and low (LIR) infusion rates (6.5 and 1.75 ml/kg/hr, respectively) to 7 dogs each for 4 h. Seven sham-operated controls (CON) received lactated Ringer's at 6.5 ml/kg/hr for 3 hr. Mean arterial pressure remained unchanged in all groups. Central venous pressure decreased in the LIR group (P less than 0.05) and remained unchanged in the other groups. Cardiac index fell uniformly (P less than 0.05) in all groups. Pancreatic blood flow (Qp) decreased in the LIR group (73%) to a significantly greater extent than in the HIR (23%) and CON (8%) groups, and in the HIR group significantly more than in the CON group. The fall in pancreatic oxygen consumption (O2Cp) in both the pancreatitis groups was significant compared to the rise in the CON group. Final changes in Qp and O2Cp from baseline were significant only in the LIR group. We conclude that inadequate crystalloid replacement after BTP results in a progressive fall in Qp and O2Cp. Vigorous fluid replacement incompletely prevents these effects.

Blood flow and distribution in the canine pancreas

Because of a tripartite arterial inflow, accurate determination of canine pancreatic blood flow (QP) in experimental studies remains problematic. Assessment of blood flow using a single electromagnetic flow probe on the anterior pancreaticoduodenal artery (APDA) was compared to the radiolabeled microsphere method. Distribution of QP was based on microsphere density. QP determined simultaneously with the flow probe technique and the microsphere method were 86 +/- 17 and 23 +/- 8 ml/min, respectively, (P less than 0.05). Following occlusion of the splenic artery (SA) and the posterior pancreaticoduodenal artery (PPDA), QP measured by the flow probe increased to 94 +/- 27 ml/min (NS) and decreased to 19 +/- 4 ml/min (NS) using microspheres. Intrapancreatic distribution of QP was not significantly altered by occlusion of the SA and PPDA. Intrapancreatic arterial collateral is adequate to maintain blood flow to the entire pancreas even when arterial inflow is restricted to the APDA. Flow probe determinations of QP are artifactually high because they include flow to the duodenum and may also be subject to methodologic error.

Blood flow measurement in the canine pancreas

Blood flow in the anesthetized animal has been measured indirectly by plethysmography and directly with the stromuhr, venous outflow, and electromagnetic flow techniques. Tissue perfusion in the gland has been assessed qualitatively with thermocouples and quantitatively by isotope fractionation, the distribution of microspheres, hydrogen desaturation, and clearance of either 133Xe or 85Kr. The results of these investigations have been conflicting as there is a large variation in both flow and perfusion measurements, not only overall but also in the values reported by each technique (Table 1). Taking all methods into account flow measurements have been recorded from 9 to 63 (mean 29.8) ml/min, and 10 to 200 (mean 66.1) ml/min/100 g. The mean percentage of the cardiac output distributed to the pancreas is 1.28. Some of these differences are due to various drawbacks associated with each of the techniques; some are almost certainly due to variations in the surgical preparations, and others are undoubtedly caused by the complexity of the pancreatic circulation. Measurements of perfusion in different regions of the pancreas of individual dogs show no difference if all vessels are intact, but accessory vessel ligation affects perfusion in certain areas. In ambulant dogs the studies suggest that pancreatic blood flow is higher than in the anesthetized animal. This is probably true despite inaccuracies associated with each of the techniques. In addition to this drawback there is also the problem of obtaining measurements with the dogs in a relaxed state. It is probably for this reason that the majority of investigators have preferred to examine blood flow and perfusion in the canine pancreas in the anesthetized animal. It is not possible to make a definitive statement regarding the best model and measurement technique available to measure blood flow or tissue perfusion in the canine pancreas. The choice should undoubtedly be governed by the aims of the proposed study. In studies of tissue perfusion in the intact gland, it is obviously preferable that all vessels should be intact, as division of any vessels supplying the gland has been shown to affect perfusion in certain areas. Measurements in such a preparation could be taken using the 85Kr clearance technique, with a flow probe placed around the gastroduodenal artery to ensure stable flow during measurements. It is difficult to assess total arterial blood flow to the whole gland due to the number of vessels supplying the organ.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood flow and perfusion in acute haemorrhagic pancreatitis in the dog

Experimental evidence suggests that in acute haemorrhagic pancreatitis in the dog the percentage of the cardiac output distributed to the pancreas falls. Histological evidence indicates arteriovenous shunt flow, but this has not been confirmed by flow measurements. It has recently been reported that in experimental preparations in which pancreatic blood flow is measured through the superior pancreaticoduodenal artery after ligation of other (accessory) vessels, perfusion is reduced in distal regions of the gland. There are no data regarding regional perfusion measurements in acute pancreatitis or the effect of ligating accessory vessels. This study therefore evaluates blood flow and regional perfusion in haemorrhagic pancreatitis in various preparations of the canine pancreas. Perfusion was assessed by measuring the clearance of Krypton-85 after injection into the arterial blood supply of the pancreas. Arterial blood flow was measured by the electromagnetic flow technique. The results show that perfusion in different regions of the gland is similar both before and during disease. If accessory vessels are ligated, however, only perfusion in the head of the gland is maintained. No arteriovenous shunt flow was shown. The percentage of the cardiac output being distributed to the gland did not change in any of the experiments; this contradiction to previous reports may arise from the effective control of acid base balance in this study.

Hypovolemic shock and contrast-enhanced computed tomography of the pancreas

The effect of profound hemorrhagic hypovolemia on cardiac output and pancreatic blood flow was studied in pigs with the thermodilution method and microsphere technique. Approximately 30-40% of the circulating blood volume was withdrawn slowly during 5 h. Cardiac output and pancreatic blood flow decreased by 35% and 32%, respectively. The animals underwent contrast-enhanced computed tomography (CT) before hypovolemia and at 5 h after its onset. The changes in systemic and local blood flow were related to the contrast enhancement of the pancreas. In spite of profound hypovolemia and a significant decrease in pancreatic blood flow (p less than 0.005), the contrast enhancement remained normal. The results of the present study indicate that pancreatic hypoperfusion caused by hypovolemia does not affect the contrast enhancement of the pancreas in CT.

Flow distribution between the endocrine and exocrine parts of the isolated rat pancreas during perfusion in vitro with different glucose concentrations

Previous studies in our laboratory have indicated that pancreatic islet blood flow is stimulated by glucose. In an attempt to evaluate to what extent intrapancreatic control mechanisms are involved in the glucose modulation of islet blood flow the distribution of flow between the endocrine and exocrine parts of the rat pancreas during perfusion in vitro with different glucose concentrations have now been studied. For this purpose pancreatic glands from 29 rats were perfused at a flow rate of 1.5 ml min-1 for 95 min with low (2.8 mM) or high (16.7 mM) glucose-containing media. Maintenance of vascular reactivity of this preparation in spite of a marked exocrine oedema was confirmed by administration to the perfusion medium of adrenaline, which immediately raised the perfusion pressure. Insulin concentrations in the effluent media were measured to correlate rates of insulin release to changes in islet flow and to assess the functional viability of the preparation. In each experiment non-radioactive microspheres with a diameter of 10 micron were injected into the perfusion medium at one of four time-points: 15, 30, 35 or 80 min after the beginning of the perfusion. Two of these injections (15 and 80 min) took place during perfusion with the low-glucose media and the remaining two during perfusion with high-glucose medium. The microspheres were counted separately in the endocrine and exocrine parts of the pancreas. The results showed that all preparations had a biphasic insulin response to glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Consumptive coagulopathy, fibrinolysis and protease-antiprotease interactions during acute human pancreatitis

Twenty-seven attacks of acute human pancreatitis of different severity were analysed concerning clinical outcome and activation of the coagulation and fibrinolytic systems. Consumptive coagulopathy was suggested by decreased platelet counts, decreased prothrombin values and consumption of fibrinogen during the first days in severe attacks. Factor X was slightly decreased the first 5 days in all attacks. Increased fibrinolysis was suggested by decreased plasminogen values in severe attacks. Fibrinogen degradation products were seen in 40% of the patients in blood and in 100% of the patients in the peritoneal fluid. The four main protease inhibitors of the two systems all showed protease-antiprotease complexation and lower functional than quantitative values. Plasma levels of antithrombin III and alpha 2-macroglobulin were low, while the levels of C1-inhibitor and alpha 2-antiplasmin were high. Functional levels of all the four protease inhibitors were almost zero in the peritoneal fluid in severe attacks. It is concluded that severe acute pancreatitis results in both consumptive coagulopathy and in increased fibrinolysis. A local antiprotease deficiency is seen in the peritoneal cavity and high levels of protease-antiprotease complexes are also seen in plasma. All these changes are closely correlated to the severity of the disease and may probably determine the clinical outcome of the acute attack.

Microangiography of the pancreas in experimental oedemic and haemorrhagic pancreatitis

Microangiography of the pancreas was performed in five normal piglets and in 10 piglets with oedemic and haemorrhagic pancreatitis in order to evaluate the role of microcirculatory changes in experimental pancreatitis. Acute haemorrhagic pancreatitis was induced by intraductal infusion of trypsin-taurocholate and oedematous pancreatitis correspondingly by infusion of autologous diluted bile. Both types of pancreatitis were confirmed by histological examination. Microangiography of the control animals revealed well-filled arteries, arterioles and capillaries, which formed a dense capillary network. In the areas of histologically documented haemorrhagic pancreatitis, unfilled capillary nets were observed as empty areas in the microangiography. Other areas of focal extravasation of the contrast material could be seen. Arteries and arterioles were well filled. In oedematous pancreatitis, the microangiography was unchanged compared with the control.

CONCLUSION

Acute experimental haemorrhagic pancreatitis is associated with severe disturbances in the capillary circulation of the pancreas, whereas in oedematous pancreatitis the microangiography of the pancreas is normal.