Blood flow and perfusion in acute haemorrhagic pancreatitis in the dog

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.

Ischemia/reperfusion injury of the pancreas: a new animal model

BACKGROUND

Ischemia/reperfusion is thought to play an important role in the development of postimplantation pancreatitis after pancreas transplantation and also in the transition of edematous pancreatitis into necrotizing pancreatitis. Previous studies have suggested that impairment of microcirculation and hence tissue oxygenation and energy metabolism may be critical steps in this process.

MATERIALS AND METHODS

In landrace pigs vascular isolation of the pancreatic tail was performed. Morphological alterations, tissue oxygenation, and energy metabolism were assessed in response to 3 h of global warm ischemia and the following reperfusion.

RESULTS

A rapid onset of morphological alterations immediately after reperfusion was noted. Oxygen consumption and ATP levels were markedly decreased, and tissue oxygenation was severely impaired especially during the first hour after reperfusion. ATP tissue levels and oxygen consumption 10 min after reperfusion correlated significantly with the morphological changes at the end of the experiment.

CONCLUSION

These findings can be explained by a failure of nutritive capillary perfusion and concomitant shunt perfusion. Therefore an impaired microcirculation rather than an impaired oxygen utilization shortly after reperfusion is of major relevance in the development of the ischemia/reperfusion injury of the pancreas.

Ischemia and reperfusion in pancreas

Ischemic diseases of heart and brain are the primary causes of mortality in industrialized nations. The ischemic injury with the consecutive reperfusion is responsible for the disturbance of microcirculation with ensuing tissue damage and organ dysfunction. Recent evidence suggests that oxygen-derived free radicals and activated polymorphonuclear leukocytes produced in ischemic tissue are instrumental in the development of ischemic cell injury. In pancreas, ischemia/ reperfusion is proposed as a potentially damaging factor accounting in part for the pathogenesis of acute pancreatitis. Apart from ischemia/reperfusion injury, the kallikrein-kinin system mediates acute inflammation associated with enhanced capillary permeability and accumulation of polymorphonuclear leukocytes, cardinal features of ischemia/reperfusion injury also in acute pancreatitis. Therefore, it seems reasonable to use bradykinin-antagonists to influence postischemic reperfusion injury of the pancreas. In the following, we describe the pathophysiology of ischemia/reperfusion injury with special reference to the pancreatic microcirculation and morphological changes as observed in a model of complete and reversible ischemia. Furthermore, we will discuss the effects of two bradykinin-antagonists (HOE 140 and CP-0597) on functional integrity of the pancreas after ischemia/ reperfusion.

Pancreatic blood flow in cats with chronic pancreatitis

Pancreatic blood flow and its relationship to pancreatic interstitial pressure were investigated in a model of chronic pancreatitis in cats using a hydrogen gas-clearance technique with an intraductal electrode. The intraductal technique correlated well with blood flow measurements made using gamma-labeled microspheres (r = 0.88, P less than 0.001). In control cats, the basal blood flow of 69.1 +/- 9.5 mL.min-1.100 g-1 increased by 25% to 86.2 +/- 11 mL.min-1.100 g-1 with secretory stimulation (P less than 0.05). Interstitial pressure was -0.02 +/- 0.3 mm Hg and did not change significantly with stimulation. In cats with chronic pancreatitis, basal interstitial pressure was 1.8 +/- 0.5 mm Hg and basal blood flow 39.9 +/- 4 mL.min-1.100 g-1 (P less than 0.05). Stimulation of the chronic pancreatitis gland increased the pressure to 3.0 +/- 0.4 mm Hg (P less than 0.01) and reduced flow 15% to 34.2 +/- 4 mL.min-1.100 g-1 (P less than 0.05). Papaverine increased blood flow in control and chronic pancreatitis cats without altering tissue pressure, suggesting that despite the reduced basal blood flow, the ability to increase blood flow was preserved in chronic pancreatitis. The increased interstitial pressure associated with secretion appeared to limit the gland's normal hyperemic response in this model of chronic pancreatitis.

[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.

Hypovolemic shock, pancreatic blood flow, and pancreatitis

Electromagnetic blood flow determinations were carried out on the superior pancreatic duodena (SPDA), the splenic (SA) and the superior mesenteric (SMA) arteries and compared to cardiac output (CO, thermodilution technique) in 12 anesthetized dogs submitted to hypovolemic shock of various duration: 5 dogs underwent a one-hour and 7 a three-hour period of shock. A 50 mm Hg level of mean arterial blood pressure (MABP) was maintained throughout hypovolemia. Dogs were then reinfused. Control preshock values were 4.12 l/min for CO, 38.0 ml/min for SPDA, 405.9 ml/min for SA, and 963.6 ml/min for SMA. SPDA, SA and SMA flows expressed as % of CO amounted to 0.9, 9.8 and 23.4% respectively. No significant changes in SPDA and SMA flows were noted within the first hour of shock. However, from the end of the second hour on, both flows differed significantly (P less than 0.01), SMA increasing from -75.6% of its control value at the end of bleeding to -61.0%, and SPDA decreasing from -75.6 to -86.9%. Similar observations were made when respective flows were considered as % of CO. The SA behaved somewhat in an intermediate fashion. This relative spoliation in pancreatic blood supply as hypovolemia proceeds supports an ischemic etiology of acute pancreatitis (AP), which could account for some of the so-called idiopathic cases of AP.