Physiologic studies during perfusion of the isolated canine pancreas. The endocrine and exocrine behavior

Composite Tissue Preservation

Composite tissue (CT) preservation is important to outcomes after replant or transplant. Since the first limb replant, the mainstay of preservation has been static cold storage with the amputated part being placed in moistened gauze over ice. Historically, the gold-standard in solid organ preservation has been static cold storage with specialized solution, but this has recently evolved in the last few decades to develop technologies such as machine perfusion and even persufflation. This review explores the impact of cooling and oxygenation on CT, summarizes the work done in the area of CT preservation, discusses lessons learned from our experience in solid organ preservation, and proposes future directions.

A Study of Normothermic Hemoperfusion of the Porcine Pancreas and Kidney

Normothermic machine perfusion has enormous potential to improve organ preservation and expand the organ donor pool. It is well established in other organs but not the pancreas, which has especially strict organ acceptance criteria. We established a model of normothermic hemoperfusion of the porcine pancreas with and without addition of the kidney as a dialysis organ. Four pancreases were harvested and perfused for 120 min with autologous whole blood at body temperature, two with parallel perfusion of the kidney and two without. The organs and perfusion circuit were evaluated for gross appearance, pH, histology and perfusion parameters. The organs maintained steadily increasing flow rate and perfusion pressure. Gross appearance of the organs was stable but appeared grossly ischemic toward the end of the perfusion period. Histology demonstrated necrosis centered in acinar tissue but islet cells were preserved. pH was significantly alkalotic toward the end of the perfusion, likely due to pancreatic tissue damage. Addition of the kidney did not result in significant improvement of the acid-base environment in this small series. In conclusion, normothermic perfusion of the pancreas is still in the experimental stages but holds great potential. Further studies to optimize perfusion parameters will significantly improve results. Parallel perfusion of the kidney may facilitate improvement in the acid-base environment.

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)

In search of an in vitro index of viability during pancreatic preservation

To determine an index of viability during pancreatic preservation, 15 dogs underwent segmental pancreatic autografting after 24 hr of pulsatile perfusion. These animals were divided into Group A (6) and Group B (9) on the basis of post-transplant normoglycemia or hyperglycemia. In each experiment, sequential perfusate amylase and arterial and venous blood gases were analyzed during preservation. In addition, sequential pancreatic tissue slices were obtained to determine in vitro insulin release. A comparison of perfusion parameters demonstrated no significant differences in pancreas weight (41 +/- 2.9 vs 38.3 +/- 1.5 mg), perfusate flow (0.24 +/- 0.2 vs 0.20 +/- 0.06 ml/min/g), diastolic (24.3 +/- 2.3 vs 26.9 +/- 1.6 mm Hg) or mean pressure (27.4 +/- 1.9 vs 30.1 +/- 1.5 mm Hg). Perfusate amylase levels (u/100 ml) and percentage change from baseline are as follows: (Table: see text). Perfusate amylase was significantly greater at 21 hr in Group A (P less than 0.005). In addition, a significantly greater rate of amylase release was evident in Group A at 1 hr (P less than 0.02), 3 hr (P less than 0.02), and 21 hr (P less than 0.01). Group B pancreata demonstrated significantly increased oxygen extraction at 1 hr (A-V O2 difference: Group A = -33, Group B = -68; P less than 0.05). In vitro insulin release of tissue slices obtained pre-harvest, post-flush, post-preservation, and 15 min post-transplantation was not significantly different in the two groups. In conclusion, sequential perfusate amylase and blood gas determinations may be useful in predicting pancreatic transplant function.

Perfusion techniques of the canine pancreas for physiological and secretin response studies

In vivo and in situ perfusion techniques of the canine pancreas for physiologic and secretin response to studies are described. We developed these modified techniques to clarify the mechanism of the pancreatic exocrine secretion. An analysis was made of some physiological parameters of the pancreas and our findings were compared with those obtained in secretin stimulation of the pancreas. The composition of secretin induced venous effluent and pancreatic juice was investigated. A decrease of pH, pO2 and (HCO-3) in the venous blood and a temporary efflux of K+ from the cell to the perfusate were observed after secretin stimulation. A temporary decrease of perfusion pressure was observed after secretin stimulation and the change is thought to be due to vascular dilatation. Ultrastructural findings from the pancreas perfused for about 1 hour showed no prominent changes.

Respiratory exchanges and acid-base balance during perfusion of ex vivo isolated pancreas

We used the technique of ex vivo isolated pancreas, perfused with whole heparinized blood. The organ was stimulated by secretin (G.I.H. Stockolm, 0.1-5.0 clinic units/hr), and/or carbamylcholine (100-200 mug/hr). Oxygen consumption was increased under stimulation. This increase was a function of the dose of secretin and also of the bicarbonate output in the juice. Oxygen uptake increased further when carbamylcholine was super-imposed on secretin. This extra increase was independent of hemodynamic conditions of the organ perfusion. Arteriovenous difference in oxygen saturation did not increase when the gland was stimulated. It tended to decrease when the stimulation resulted in a marked vasodilatation. Thus, oxygen needs seemed to be neither the limiting factor of the response to a given stimulation nor the triggering mechanism of functional vasodilatation. Values of pCO2 were spread over a wide range from one experiment to another. However, it could be observed that CO2 efflux into the vein decreased under stimulation by secretin; in most experiments, CO2 efflux was even replaced by an apparent consumption of CO2 during the perfusion of the stimulated gland. Furthermore, arteriovenous pH difference increased following secretin stimulation. This increase was dose-related to secretin. These facts are discussed under the background of theories recently proposed for bicarbonate secretion.

Pancreaticoduodenal preservation by hypothermic pulsatile perfusion for twenty-four hours

Pancreaticoduodenal grafts remained viable after transplantation only if a modified plasma perfusate with high osmolarity was used during the 24 hours of preservation. When regular plasma perfusate was used during the pancreaticoduodenal preservation, irreversible damage resulted, and all dogs died of ischemie or vascular changes in the first few days after transplantation.