Continuous peritoneal dialysis as treatment of acute experimental pancreatitis in the rat. II. Analysis of its beneficial effect

Clinical pancreatology I: Pancreatic medical history

The present article and subsequent reviews will not be to report all what has been published, but rather to give an introduction samples that hopefully make the reader eager to read the whole article or articles with "a taste of clinical pancreatology in 2010". The main sources of literatures were PubMed, and the additional Journals such as Pancreas, Pancreatology and Journal of the Pancreas were also scrutinized. Only some full articles in almost all languages were included in the review, other articles, however, that were too superficial or too poor in other ways, were omitted, and the publications of non-human study were excluded.

Treatment of acute pancreatitis: an attempted historical review

This attempt at a historical review of the treatment of acute pancreatitis summarizes the findings of studies carried out in decades long past and shows their impact on the therapy of this disease today. It identifies in retrospect the correct avenues of research and the blind alleys, and describes the ebb and flow of interest in various forms of management. Acquaintance with the work of previous investigators may prevent the unnecessary rediscovery of old principles of treatment. Not all of the studies discussed can be found with search engines: they come from the author's personal library, collected over his 40 years as an active pancreatologist, and from the knowledge of the early literature bequeathed to him by his teachers and mentors.

Hemodynamic effects following intraperitoneal infusion of pancreatic ascites fluid

Severe necrotizing pancreatitis is accompanied by release of hemorrhagic ascites fluid (HAF), which is thought to be related to the occurrence and frequency of cardiocirculatory and pulmonary failure as a consequence of acute pancreatitis. The purpose of this study was to evaluate the role of HAF due to these systemic complications. Experiments were performed in 25 pigs (mean b.wt. 22 +/- 1 kg) under general anesthesia and mechanical ventilation. The animals received 50 ml/kg b.wt. i.p. of either physiologic saline solution (control CO, n = 9) or hemorrhagic ascites fluid (HAF, n = 16). HAF was obtained from 16 pigs with pancreatitis induced by intraductal infusion of bile salt. Eight animals in the HAF group were pretreated with indomethacin (10 mg/kg i.v. INDO/HAF). All animals were followed up for 6 h. Mean arterial pressure, cardiac output, and stroke volume fell significantly in the HAF (-25%, -27%, -27%) and in the INDO/HAF groups (-24%, -20%, -17%) as compared with controls (-6%, -6%, -6%). Also, left ventricular end-diastolic pressure (LVEDP) decreased by 52% and 48% in both HAF recipient groups, whereas LVEDP was unchanged in the control group. Myocardial contractility (Vmax) remained unaltered in all experimental groups. No significant differences in gas exchange and lung dry/wet weight ratio were observed. Lipase and PGI2 of the unpretreated HAF group rised to 203% and 198% in arterial blood at 6 h compared with unaltered levels in the control group. No increase of prostanoid concentrations was detected in the indomethacin-pretreated group, whereas lipase increase by a comparable extent as in the HAF group. We conclude that the early consequences of HAF are mainly characterized by systemic hypotension due to hypovolemia.

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.

Role of the protease-antiprotease balance in peritoneal exudate during acute pancreatitis

The peritoneal exudate formed during experimental pancreatitis is toxic when administered intraperitoneally or intravenously to other animals. Overwhelming of the peritoneal antiprotease defences by proteolytic enzymes released from the pancreas may be a key factor responsible for this toxicity and is examined in the current study. Human pancreatitis exudates possessed tryptic amidase activity indicating trypsinogen activation. The trypsin inhibitory capacities of exudates were reduced indicating a degree of consumption of the peritoneal antiproteases. Of 21 exudates examined, three showed marked reduction of their trypsin inhibitory capacity indicating almost complete consumption of their antiproteases. All three patients were shocked at the time of sampling, two dying of fulminant pancreatitis within 24 h. Overwhelming of the peritoneal antiproteases was not confirmed, but may occur in a few instances where proteolytic enzyme release or zymogen activation continues. Intraperitoneal administration of exogenous antiproteases prolongs survival in rats with pancreatitis and has been suggested as a therapy in man. The current data suggests that few patients are likely to benefit from such an approach.

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.

Effective intraperitoneal antiprotease therapy for taurocholate-induced pancreatitis in rats

In canine pancreatitis, irreversible hypotension and death follow saturation of the antiprotease molecules in peritoneal exudate by activated proteolytic enzymes which are released from the pancreas. This study has examined, in rats with taurocholate-induced pancreatitis, the efficacy of removal of the peritoneal exudate by aspiration and a single lavage, followed by instillation of an exogenous antiprotease solution. Instillation of human fresh frozen plasma, containing alpha 2-macroglobulin and alpha 1-antiprotease, was associated with the longest median survival. Aprotinin, although possessing a much greater trypsin inhibitory capacity, just failed to significantly improve the median survival time compared with the control group. Intraperitoneal antiprotease therapy is simple to perform, has a beneficial effect on survival time in this model and merits investigation in man.

Continuous peritoneal dialysis in acute experimental pancreatitis in dogs. Effect of aprotinin in the dialysate medium

In 27 beagle dogs, acute necrotizing pancreatitis was induced by retrograde injection of autologous bile and trypsin into the main pancreatic duct. Animals were randomly assigned to the following treatments: group 1--(9 dogs) aprotinin 600,000 KIU/d by i.v. route; group 2--(9 dogs) peritoneal dialysis for 6 d plus 500,000 KIU/L of aprotinin in the dialysate fluid; group 3--(9 dogs) peritoneal dialysis without aprotinin in the dialysate fluid. All dogs of the group 1 died within 16 h following the induction of pancreatitis and extensive necrotizing and hemorrhagic changes were seen in the pancreatic and peripancreatic areas. Six dogs of the group 2 survived and no necrotizing changes were observed 30 or 50 d after the induction of pancreatitis. Three dogs of the group 3 survived, but slight necrotizing lesions were found at the autopsy. The survival rate was higher in dogs with peritoneal lavage (p = 0.0129) or with peritoneal lavage plus aprotinin (p less than 0.0001) than in those receiving i.v. aprotinin, indicating that the latter treatment has no beneficiary effect on the course of acute pancreatitis.

High volume lesser sac lavage in acute necrotizing pancreatitis

The effect of lesser sac drainage with or without lavage on some early predictors and on outcome in acute necrotizing pancreatitis was analysed. The evaluation was made prospectively for 24 patients, in a single centre study. According to Ranson's criteria and laparotomy findings, the lavage and drainage groups were comparable and the pancreatitis was severe and necrotizing in both groups. In a longitudinal analysis of the first 4 postoperative days, lavage did not show any advantage over drainage, as measured by seven prognostic signs (serum creatinine, blood glucose, base excess, haematocrit, white blood cells, C-reactive protein and immunoreactive phospholipase A2 concentration). Furthermore, the study did not find that lavage had any positive effect on the incidence of mortality (36 versus 17 per cent in the drainage group) or on septic complications in acute necrotizing pancreatitis. In the total series the extent of pancreatic necrosis was an essential predictor of the outcome.

Increased peritoneal permeability in acute experimental pancreatitis

The peritoneal permeability to differently sized dextran molecules; Mw 4,000, 10,000, 20,000, and 40,000 was investigated in rats with bile-induced acute pancreatitis. Following intraperitoneal deposition, repeated blood samples for measurement of the different dextrans were collected. The results showed increased peritoneal permeability to molecules between 4,000-20,000 daltons in animals with pancreatitis, whereas there was no significant difference for molecules of 40,000 daltons compared to healthy control animals. Also, the passage of phospholipase A2 (Mw 14,000) over the peritoneal membrane was increased during pancreatitis. It is suggested that the transperitoneal route may be of pathophysiological importance in the development of the systemic components of severe acute pancreatitis.

Peritoneal lavage combined with volume therapy in porcine hemorrhagic pancreatitis. Effects on hemodynamics, microcirculation, and peritoneal morphology

Acute hemorrhagic pancreatitis was induced in 15 piglets, after which 8 of the piglets were treated with saline infusion only and 7 were treated with saline infusion and peritoneal lavage. Hemodynamic variables were measured hourly. Organ and peritoneal blood flow was determined at 0, 1, and 5 h with radioactive microspheres. Peritoneal morphology was studied at 0, 1, 3, and 5 h with light microscopy and scanning electron microscopy. According to the results, changes in cardiac output, mean blood pressure, and peritoneal blood flow and the peritoneal inflammatory reaction were similar in the two groups. However, a significant increase in heart rate and a significant decrease in the blood flow to the pancreas, liver, and spleen were observed in the saline group, in contrast to the lavage group. In addition, blood flow to the adrenal glands was significantly higher in the saline group after 1 h. In conclusion, peritoneal lavage prevented the increase in heart rate and the development of a significant decrease in pancreatic blood flow in experimental hemorrhagic pancreatitis. The significance of these findings remains to be further evaluated.

Acute and chronic pancreatitis. An update on management

Therapeutic measures for acute pancreatitis depend on the severity of the disease and its complications. Since complications of acute pancreatitis may develop at any time, patients should be admitted to an intensive care unit for assessment (and frequent reassessment) of the severity of the disease and the development of complications. Basic therapy should include relief of pain, total fasting, nasogastric suction, parenteral replacement of fluids, electrolytes, albumin and blood, and antibiotics. Hyperglycaemia should be corrected and heparin should be given in cases of disseminated intravascular coagulation. In renal insufficiency, peritoneal dialysis is important, and in respiratory complications, humidified oxygen or artificial ventilation including positive and expiratory pressure therapy should be applied. Although the effect of peritoneal dialysis has been proven only in animal experiments and in retrospective studies in man, it is recommended in severe cases for shock therapy and for correction of electrolyte imbalance when ascites is present, even before anuria occurs. Conservative treatment measures in chronic pancreatitis are limited to the management of pain and of exocrine and endocrine pancreatic insufficiency.

Pulmonary complications in fatal acute hemorrhagic pancreatitis

Morphological changes of the lung occur frequently in fatal acute hemorrhagic pancreatitis. The pulmonary alterations are independent of mechanical ventilation and therefore not due to iatrogenic damage caused by high inspired oxygen concentrations. The histological findings are similar to those seen in the so-called shock lung syndrome. The pulmonary lesion develops progressively and three stages can be separated: early, late, and final phase. The pulmonary complications in acute hemorrhagic pancreatitis may be explained by the release of mediators such as pancreatic enzymes or free fatty acids into the blood stream. In acute hemorrhagic pancreatitis a close monitoring for shock parameters is necessary. A fall in arterial PO2 is an early indication for mechanical ventilation, including positive end-expiratory pressure.