Complete Devascularization Research Articles

Magnetic resonance imaging with superparamagnetic iron oxide particles to evaluate hepatic macrophage—Monocytic phagocytosis after arterial devascularization in Minipigs

We examined the effects of arterial ischemia on the phagocytic activity of the hepatic macrophage-monocytic phagocytic system (MMPS). Six minipigs were studied before and 24 hr after complete arterial devascularization of the liver. Magnetic resonance (MR) imaging was performed at 1.5 T using superparamagnetic iron oxide (SPIO) particles (18 mumol Fe/kg body weight) as an MMPS-specific contrast agent. Hepatobiliary scintigraphy, measurements of serum liver enzymes, and histology also were obtained. On MR imaging, the postcontrast-to-precontrast ratios of the arterially devascularized livers were significantly higher than the corresponding baseline values (p < .01). The greatest difference (52%) between the baseline and the postoperative values was observed on gradient-echo (GE) images. Scintigraphy, laboratory analyses, and histology results indicate that the MR imaging findings were probably predominantly attributable to a reduction in phagocytic activity of the hepatic MMPS. SPIO particles have already proved useful for improving detection of liver neoplasms on MR imaging, but they also may provide a novel way of evaluating the function of the hepatic MMPS in liver diseases.

Ejection of the Proximal Scaphoid in a Trans-scaphoid Perilunate Fracture Dislocation

Trans-scaphoid perilunate fracture dislocations are difficult injuries to treat. Described herein is the unusual case of a trans-scaphoid perilunate fracture dislocation in which the proximal scaphoid fragment was ejected into the volar aspect of the distal forearm. The significant displacement of the proximal fragment represented complete devascularization of this piece. This unique fracture raised difficult management issues in the treatment of this injury. A primary proximal row carpectomy was performed, with a successful clinical result.

Decision analysis in children with blunt splenic trauma: The effects of observation, splenorrhaphy, or splenectomy on quality-adjusted life expectancy

The management of blunt splenic trauma in children has remained controversial, with different physicians advocating observation, splenorrhaphy, and splenectomy. Proponents for each position have debated the relative importance of rebleeding (delayed splenic rupture), posttransfusion hepatitis with its sequelae, and overwhelming postsplenectomy sepsis. In an attempt to guide the clinician, a decision analysis was performed. Variables evaluated included the incidence of transfusion, postsplenectomy sepsis, posttransfusion hepatitis, chronic active hepatitis, cirrhosis, and rebleeding. The quality-adjusted life expectancies (QALEs) when the average incidence of the variables were used in the decision analysis were 62.69 years for observation, 62.32 years for splenorrhaphy, and 61.14 years for splenectomy. Sensitivity analysis showed that there was very little difference between observation and splenorrhaphy when the transfusion rate and hepatitis rate were varied. But these treatment options produced longer QALEs than splenectomy. Therefore, in appropriately selected patients, observation is a safe and effective therapeutic option. If an operation is necessary, every effort should be made to preserve the spleen. Splenectomy may still be required in those cases of complete devascularization, persistent hemorrhage, or other associated significant injuries.

Intravascular Coagulation and Osteonecrosis

Current evidence suggests that intravascular coagulation (IC), an intermediary mechanism, is the most likely final common pathway by which intraosseous fat embolism causes nontraumatic osteonecrosis (ON). Stage 1A lesions (fatty osteocytic necrosis) appear to progress to classic Stage 1B lesions (ischemic degeneration of necrotic osteocytes and adipocytes) when the ischemic threshold is exceeded by absolute subchondral fat overload with insufficient local clearance of procoagulants, especially tissue thromboplastin. The result is vascular stasis, hypercoagulability, endothelial damage (by free fatty acids) and IC, especially if there is coexistent subchondral vasoconstriction and impaired secondary fibrinolysis. Osteonecrosis can be produced in animals by IC, which begins in the vulnerable subchondral microcirculation (Arthus phenomenon). Cartography (embolic scintimetry with superselective angiography) indicates early complete devascularization of the femoral head, suggesting progressive venous and retrograde arterial thrombosis. Increased plasma fibrinopeptide A and direct histologic evidence of intraosseous thromboses and peripheral hemorrhages further indicate that IC is the final pathway. Best evidence are 51 ON lesions complicating disseminated IC in eight children (Shwartzman phenomenon), with collateral histologic evidence of intraosseous thrombosis and ON.

Effect of circumferential bands on cortical vascularity and viability

Wire cerclage devices do not restrict cortical vascularity; however, bands, because they are flat and wide, have been implicated as the cause of fracture nonunion by disruption of cortical vascularity. This experiment evaluated the effect of cerclage bands on the cortical vascularity of bones that had not been fractured. Stainless-steel bands of four sizes (2.5, 5.0, 7.5, and 10.0 mm wide) and nylon bands of five sizes (2.5, 3.6, 4.8, 7.6, and 9.0 mm wide) were applied 1 cm apart to both femoral diaphyses of four mature dogs. In two additional dogs, 18-gauge cerclage wires were applied 5 mm apart on one femur and nylon bands were applied immediately adjacent to one another on the other femur to cover 3 cm of the length of each femoral diaphysis. These six dogs were euthanatized and perfused 7 days postoperatively and specimens were studied by microangiography and correlated histology. Two additional dogs were studied 4 and 15 weeks after application of nylon and metal bands. There was no evidence of complete cortical devascularization under any size or type of cerclage appliance at any time interval. Numerous examples of vessels traversing the cortex directly beneath all the cerclage appliances were observed. Cerclage devices, even when flat and wide, do not restrict cortical vascularity when applied to intact bones.

A rat model of esophageal varices

We have developed a new method for inducing portal hypertension and esophageal varices in rats--partial ligation of the portal vein after devascularization of the circumference of the left renal vein and complete ligation of the portal vein on the fifth day thereafter. Thirty rats were separated into groups of 10, control (sham operation), complete portal ligation only and complete portal ligation plus devascularization. Two weeks after the surgery, the presence of esophageal varices in rats with complete portal ligation plus devascularization was confirmed by portography and by the histological findings. The diameter (mean +/- SD) of the submucosal veins of the lower esophagus in the complete portal ligation plus devascularization group (219.4 +/- 86.6 microns) was significantly larger than that in the complete portal ligation group (99.8 +/- 53.4 microns) or in the control group (30.5 +/- 16.6 microns) (p less than 0.01). Vascular structures of the lower esophagus closely resembled those in humans with esophageal varices. This new technique is simple, rapid and reliable, and application can be made to various experimental studies on portal hypertension.

Effect of Internal Mammary Artery Mobilization on Sternal Blood Flow

Use of the internal mammary artery as a conduit for coronary artery bypass has enhanced this procedure in terms of prolonged graft patency. An earlier warning that use of both arteries would devascularize the sternum was based on postmortem radiologic imaging. This was complemented by a subsequent animal study employing isotopic microspheres. In the present clinical study, laser Doppler flowmetry was adapted to identify changes in blood supply to the left half of the divided manubrium sternum during separation of the left internal mammary artery from its chest wall attachment. Our finding of continued blood flow after this event suggests that complete devascularization of the sternum does not take place. Quality of sternal bone and surrounding tissues and clinical indications should remain as factors influencing use of one or both internal mammary arteries.

Esophageal varices evaluated by endoscopic ultrasonography: observation of collateral circulation during non-shunting operations

To clarify the inflow and outflow vessels of esophagogastric varices, we investigated the collateral circulation using endoscopic ultrasonography (EUS; Olympus GF-UM2, 7.5 MHz, radial type) during non-shunting operations in 16 cases of portal hypertension. The main inflow vessels were the left gastric veins and the short gastric veins. The paraesophageal vessels coalescent with esophageal varices were distributed up to 7 cm from the esophagogastric junction. It was possible to devascularize these inflow vessels from the transabdominal approach, and it was also easy to evaluate the complete devascularization by the intraoperative EUS. The main outflow vein seemed to be the azygos arch from the investigation of cross-sectional areas of the azygos system. EUS is very useful in evaluating portal hypertension and in determining the indications and the efficacy of the treatment.

Application of magnetic resonance imaging technique in determining canine muscle and human free-flap viability.

Magnetic resonance imaging technique is an exciting, new, safe clinical tool that provides a noninvasive way to monitor free-tissue transfers. Magnetic resonance imaging (MRI) produces a cross-sectional tomographic image at higher resolution than conventional CAT scans and provides a dynamic and physiologic assessment of transferred tissue. We first studied ischemic muscle in the beagle hindlimb gracilis muscles and found an incremental and definitive increase in signal strength both over time and in comparing complete devascularization to partial devascularization. In the right hindlimb (partially devascularized), there was an average increase in T2 (measured in milliseconds) of 2.5 percent at 1 hour, 16.72 percent at 3 hours, and 16.45 percent at 12 hours as compared to normal undisturbed muscle. Similarly, the left hindlimb (completely devascularized) measurements increased from 10.97 percent at 1 hour to 24.02 percent at 3 hours to 47.75 percent at 12 hours. Possible explanations for T2 increases include an increase in intercellular and intracellular water, a change in pH, and possible protein metabolism changes. Clinical studies in seven patients with free flaps have shown "normal" T2 values in healthy tissue comparable to undisturbed canine gracilis muscle and the change in contour and composition of tissue over time. The clinical usefulness of these data is apparent.

Successful treatment of hepatic coma by a new artificial liver device in the pig.

In this study, we tested a new artificial liver device using liver pieces in 8-h hemoperfusion of comatous porcine blood and compared two alternative tissue preparations. Acute hepatic coma in the pigs was induced by complete devascularization of the liver. The animals were killed in stage IV coma (15-25 h after the operation), and 1 l blood was perfused over 200 g fresh or DMSO-preserved liver cubes. After the devascularization GOT, GPT, GLDH, AP, LDH, SDH, bilirubin, free fatty acid, and bile acid levels in serum increased progressively. Ammonia concentrations underwent a rapid increase in the first 9 h of coma development from 126.0 +/- 9.9 to 321.9 +/- 62.2 mumol/l. Most of the amino acids in serum were elevated and molar ratio of BCAA/AAA declined from 3.87 +/- 0.79 to 0.92 +/- 0.24. In the course of hemoperfusion ammonia was removed from the perfusate to 71% of the initial values using fresh and to 39% using preserved tissue. Correspondingly, there was an increase in urea concentrations. Amino acid metabolism was ameliorated during the perfusion; Fischer's quotient increased from 0.91 +/- 0.15 to 1.38 +/- 0.14 (fresh liver) and from 0.89 +/- 0.14 to 2.11 +/- 0.44 (preserved liver); neuroexcitatory amino acids Asp and Glu were markedly elevated. Energy charge of the liver cells increased and reached levels exceeding 0.5 in both experimental groups, a balanced energy metabolism was maintained and suggests active metabolization by the liver pieces. In comparison with fresh tissue, preserved liver cubes proved effective. We consider our artificial liver device capable of temporary hepatic support in acute necrosis of the liver and suppose that its efficiency can be potentiated by combining this system with other procedures.

709 Use of Superoxygenated Intraluminal Fluorocarbons in the Treatment of Experimental Intestinal Ischemia

Direct amelioration of intestinal ischemia using an inert intraluminal oxygen carrier is an appealing concept. The perfluorocarbons are biologically inert substances known to reversibly bind oxygen such that passive local delivery of oxygen to tissues is theoretically feasible. 75-100 gram weanling male Sprague-Dawley rats (n=46) were divided into timed study groups from 0.5 to 5 hours. All underwent laparotomy with identical complete de-vascularization of two adjacent 5 cm segments of terminal ileum. Each intestinal segment was treated with a single intraoperative instillation of either; Superoxygenated FC-43 (initial pO2596) or physiologic saline. Timed sacrifice was performed and tissue taken for light and electron microscopy. Blinded (norwai) histologic evaluation was performed in triplicate using a scoring system to quantitate the ischemic injury. (0= normal to 6= full thickness necrosis).The fluorocarbon treatment group has a significantly (p<.01) lower histologic score than the saline treated controls at comparable time points; indicating a cytoprotective effect in the treatment group. (Wilcoxian sign rank test). The utility of this preliminary observation will require further laboratory and clinical experience.

Plasma levels and renal removal of gastrin after acute hepatic ischemia in dogs.

Plasma levels and renal uptake of gastrin were determined in ten dogs submitted to complete liver devascularization in order to induce an acute liver failure. Renal function was evaluated by renal plasma flow (RPF) and glomerular filtration rate (GFR) determinations. Liver devascularization was obtained by end-to-side porto-caval shunt (PCS) followed by temporary clamping of the hepatic artery. PCS alone did not affect renal function and renal ability to remove gastrin; after hepatic ischemia, both RPF, GFR and renal extraction of gastrin showed an abrupt decrease. At the end of the period of hepatic ischemia 5 dogs were submitted to glucose infusion, in consideration that: i) glucagon is able both to affect gastrin release and renal hemodynamics, and ii) hypoglycemia that develops after liver failure releases elevated amounts of glucagon. The renal handling of gastrin was not related to glucagon plasma levels, though the higher gastrin levels occurred at the lower glucagon concentrations. These data suggest that in acute liver failure there is a striking decrease of the renal clearance of gastrin associated with the impairment of kidney function. Furthermore, in this pathological condition plasma gastrin levels are affected by blood glucose concentrations through its effect on plasma glucagon levels.

Complete devascularization of hepatic lobe with nonresectable hepatoma

Complete dearterialization of the entire liver was carried out in three patients with nonresectable liver cell carcinoma in whom the right or left portal vein had already obstructed due to tumor thrombosis or invasion. Although remittent fever ensued for two to three weeks postoperatively in all patients, hepatic infarction never occurred in the devascularized hepatic lobes. The effect of the treatment on tumorous lesions appeared satisfactory. The results indicated that the tumor-bearing liver can tolerate nearly complete deprivation of hepatic arterial and portal blood in at least one lobe of the liver if it is not simultaneous.

Transthoracic cardiectomy with infraesophago-supragastric devascularization for bleeding esophageal varices

Based on the thoughts that transthoracic approaches give less load to liver than transabdominal ones, and that effectiveness for bleeding esophageal varices is secured by cardiectomy with complete devascularization of lower esophagus and upper stomach, a new operative procedure for esophageal varices is described which is more safely applicable to the risky patients. Twenty cases with portal hypertension were operated, including eight cirrhotic patients with severe hepatic dysfunction, six cases of emergency bleeding and six reoperated cases. No operative death was encountered, but three cirrhotic patients died during the late follow up period. The remaining 17 patients had uneventful postoperative courses without recurrence esophageal bleeding during 20 months follow up period. Thus this operation may eliminate the shortcoming of previous operative methods for portal hypertension.

The effect of collateral circulation on survival in liver ischemia

In experiments designed to study the effects of acute hepatic ischemia, all collateral arterial pathways should be interrupted if complete hepatic devascularization is to be achieved and the extraction of indocyanine green is a convenient method to check the completeness of liver isolation. In dogs, the maximum safe period of temporary hepatic inflow stasis was prolonged by maintaining a minimum blood flow to the liver along collateral vessels in the gastrohepatic omentum.

Effect of induced infarction on rat liver implanted with Walker carcinoma 256.

Ligation of a branch of the portal vein or of an extrahepatic bile duct results in atrophy of the corresponding liver lobe. The remaining liver undergoes compensatory hypertrophy. This process is well tolerated by rabbits and dogs.1,4,5Complete devascularization of a portion of the liver results in infarction. When necrotic parts of liver tissue are left within their abdomen, dogs die within 36 hours. There is evidence that death occurs only if the liver tissue becomes decomposed by bacterial action.2Rats, however, are able to control massive bacterial growth in necrotic liver tissue and survive infarction of up to 70% of their liver (100% of 18 rats3). If ligation of various structures of the portal hilus, leading either to atrophy or to necrosis of part of the liver, is followed by regression of a malignant growth within the affected liver tissue, this method could be used as