Thoracoabdominal aneurysm repair.

Aneurysms that extend from the descending thoracic aorta into the abdomen and also those that involve the visceral segments of the upper abdominal aorta are traditionally classified as thoracoabdominal. Besides the surgical exposure difficulties associated with repair of these aneurysms, the temporary interruption of renal, splanchnic, and perhaps even spinal cord flow introduces a number of potential complications that makes surgical repair of these aneurysms a daunting task. The exact incidence of thoracoabdominal aneurysms is unknown, but population studies suggest a prevalence at least a log fold less than the more common infrarenal abdominal aortic aneurysm. The poor prognosis of nonsurgically treated aneurysmal disease of the descending thoracic and abdominal aortas has been reasonably well established. Few patients with thoracoabdominal aneurysms survive beyond five years as a result of not only aneurysm rupture but also death from advanced co-morbid medical disease. Since the first successful report of thoracoabdominal aneurysm repair over 40 years ago, a number of remarkable contributions have been made in the field. These advances have led to a significant decline in operative mortality as well as procedure related morbidity. Spinal cord ischemia remains a perplexing and devastating complication following thoracoabdominal aneurysm repair. A number of surgical adjuncts have been developed over the years to reduce the incidence of cord ischemic complications, yet a great deal of controversy still exists with regards to the optimal protective strategy. A description of the incidence, natural history, and classification of thoracoabdominal aneurysms, along with associated repair techniques centered on reducing spinal cord ischemic complications will form the basis for this review.

Strain differences in neointimal hyperplasia in the rat.

We performed an initial screen of 11 rat strains by use of a standard balloon injury to the left iliac artery to observe whether genetically determined differences existed in the development of neointimal hyperplasia. Neointimal hyperplasia was assayed 8 weeks after the vascular injury on coded microscopic sections. Statistically significant differences in the percentages of the vascular wall cross-sectional areas composed of intima (percentage intima) secondary to neointimal hyperplasia were noted among the different rat strains (P<0.02), with the Brown-Norway (BN), Dark Agouti, and Milan normotensive strain rats having the highest and the spontaneously hypertensive rats (SHR) having the lowest percentages of intima. In a separate experiment, F1 hybrids of SHRxBN strains and parental BN and SHR underwent the vascular injury, and the parental strains again showed a statistically significant difference from one another in the mean percentage of intima (P<0. 0001). The F1 hybrids showed an average percentage of intima intermediate between those of the parental strains. The average lumen size of the injured BN vessels were significantly smaller than that of the noninjured control vessels (P=0.044), but this significance disappeared when the circular areas of these vessels were calculated without taking neointimal growth into consideration (P=0.649). These results provide the groundwork for a genetic linkage analysis to identify the genes that influence the development of neointimal hyperplasia after vascular injury.

Surgical repair of ruptured abdominal aortic aneurysms in the state of Maryland: factors influencing outcome among 527 recent cases.

PURPOSE: Abdominal aortic aneurysm (AAA) rupture has been historically associated with high operative mortality rates. In this community-based, cross-sectional study, we examined factors influencing outcome after operations performed for ruptured AAA (rAAA). METHODS: An analysis of a state database identified 3820 patients who underwent AAA repair between 1990 and 1995, including 527 (13.8%) who had an operation for an rAAA. Demographic variables examined included patient age, gender, race, associated comorbidity rates, operative surgeon experience with rAAA, and annual hospital rAAA and total AAA operative volumes. Outcomes measured included operative mortality rates, hospital length of stay, and charges. RESULTS: Operative mortality rates increased significantly with advancing age (P < 0.0001) but were not related to gender (P = 0.474) or race (p = 0.598) and were significantly lower among patients with hypertension (P = 0.006) or pulmonary disease (P = 0.045). There was no relationship between hospital rAAA or total AAA volume and rAAA repair mortality rate, although high-volume surgeons (i.e., performing more than 10 rAAA repairs) had decreased mortality rates and hospital charges compared with other surgeons. Hospital lengths of stay and charges increased with age among survivors, but not nonsurvivors, of rAAA repair. Despite a stable incidence of rAAA repairs during the study interval and no significant change in the mean age of patients undergoing operation or the percentage of operations performed by high-volume surgeons, the statewide mortality rate declined from 59.3% to 43.2% (P = 0.039). CONCLUSION: The incidence of rAAA does not appear to be declining. Although operative rAAA repair continues to be associated with substantial risk and remains an especially lethal condition among the elderly, the operative mortality rate has declined in recent years in Maryland. Lower operative mortality rates and hospital charges are associated with operations performed by high-volume surgeons.

Abdominal aortic tailoring for renal, visceral, and lower extremity malperfusion resulting from acute aortic dissection.

PURPOSE: The treatment of ischemic complications that result from aortic dissection is a challenging and controversial problem. The purpose of this study was to evaluate aortic tailoring in the management of acute aortic dissection associated with visceral, renal, or lower extremity ischemia. METHODS: We retrospectively reviewed the clinical courses of seven consecutive patients (five men, two women) with a median age of 68 years (range, 48 to 74 years) from January 1994 to January 1997. All patients underwent an abdominal aortic tailoring procedure for relief of ischemic complications associated with acute aortic dissection (type IIIB, n = 6; type I, n = 1) and a normal-sized aorta. RESULTS: All seven patients survived and recovered full mesenteric, renal, and lower extremity function. Two patients required temporary hemodialysis in the immediate postoperative period. There has been no significant dilatation of the tailored aortic segments, with an average follow-up of 19 months (range, 1 to 30 months). CONCLUSIONS: Abdominal aortic tailoring represents a safe and effective method for treating ischemic complications associated with acute aortic dissection and a normal aortic luminal diameter.

Bilirubin monoglucuronide promotes cholesterol gallstone formation.

Recent evidence suggests that cholesterol (Ch) solubility in bile is determined by a complex interaction of mixed micelles and lecithin-cholesterol vesicles. Bilirubin monoglucuronide (BMG), which binds to bile salts and incorporates into mixed micelles, may displace cholesterol from micelles into vesicles, thus favoring cholesterol monohydrate crystal precipitation. Therefore, we designed an experiment to test the hypothesis that BMG may enhance cholesterol gallstone formation without inducing cholesterol supersaturation. For 8 weeks, 28 adult male prairie dogs were fed either a control, nonlithogenic diet (0.03% Ch), a high carbohydrate diet (CHO) which has no cholesterol but increases hepatic bilirubin secretion, or the same CHO diet plus 0.03% Ch. Cholecystectomy was then performed, and bile was examined microscopically for stones or crystals and analyzed for BMG and biliary lipids. Cholesterol saturation index was calculated. Cholesterol gallstones were found in none of the control animals and in 13% of the CHO-fed animals. However, the addition of trace cholesterol to the CHO diet resulted in an 88% incidence of cholesterol gallstones (P less than 0.001 vs control, P less than 0.01 vs CHO, respectively). Gallbladder bile was unsaturated with cholesterol in all groups. (control = 0.65 +/- 0.05, CHO = 0.46 +/- 0.05, CHO + 0.03% Ch = 0.70 +/- 0.03). CHO feeding alone or with trace cholesterol significantly elevated gallbladder bilirubin monoglucuronide, phospholipid, and cholesterol concentrations when compared to controls. These data suggest that in the prairie dog a high carbohydrate diet with only trace amounts of cholesterol increases bilirubin monoglucuronide in gallbladder bile and causes cholesterol gallstone formation without inducing cholesterol supersaturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic lymphoma. Is surgery mandatory for diagnosis or treatment?

From 1982 to 1986, nine patients with non-Hodgkin's lymphoma primarily involving the pancreas were managed at the Johns Hopkins Medical Institutions. This group of nine patients represents 2.2% of patients with non-Hodgkin's lymphoma (nine of 402) and 4.9% of all patients presenting with pancreatic malignancies (nine of 182) at the Johns Hopkins Medical Institutions during this period. Computed tomography (CT) scan findings of a large pancreatic mass (6 cm) with extrapancreatic extension and significant retroperitoneal lymph node enlargement suggested lymphoma. Diagnosis was established by radiographically-guided needle biopsy in four patients, by laparotomy in four, and by peripheral lymph node biopsy in one. In five jaundiced patients, initial chemotherapy with the nonhepatotoxic agents cyclophosphamide and prednisone resulted in marked tumor regression, allowing for early resolution of jaundice and subsequent addition of more aggressive adriamycin containing combination chemotherapy. Overall, complete remission has occurred in six of nine patients, with a median survival of 24 months (range 4-69 months). It is concluded from this experience that the majority of patients with pancreatic lymphoma can be managed without surgery. Excellent control of symptoms, including jaundice, as well as long-term remission, can be obtained with chemotherapy alone. The only role for surgery in this setting may be to aid in establishing the diagnosis when percutaneous biopsy is nondiagnostic.

Neuropeptide Y: a candidate neurotransmitter for biliary motility.

Neuropeptide Y (NPY) is a recently discovered polypeptide found in neurons throughout the gastrointestinal tract and in especially high concentrations in the biliary tree. This study was designed to test the functional significance of these high concentrations in the biliary tree by determining the effect of intravenous NPY on sphincter of Oddi and gallbladder motility. In adult male prairie dogs a side-hole, pressure-monitored perfusion catheter was placed through a choledochotomy into the duodenum and positioned in the sphincter of Oddi. A perfusion catheter was also placed in the gallbladder fundus. Sphincter of Oddi and gallbladder pressures were recorded before and during intravenous infusions of NPY at doses of 10, 100, and 500 ng/kg/min. Each dose was administered to seven separate animals. No effects were seen at the 10 or 100 ng/kg/min doses. NPY at the 500 ng/kg/min dose significantly increased sphincter of Oddi phasic wave frequency, amplitude, and motility index (MI = F X A). In addition, gallbladder pressure was significantly increased after 20 min of intravenous infusion of NPY at the 500 ng/kg/min dose. No significant changes in blood pressure were noted. These data suggest that in the prairie dog, systemic intravenous infusion of NPY significantly increases sphincter of Oddi phasic wave activity and gallbladder pressure. These findings are similar to those observed with intravenous cholecystokinin but opposite of those seen with peptide YY in this species. We hypothesize that neuropeptide Y may be an important neurotransmitter or neuromodulator regulating bile flow.

Gastrosphincter of Oddi reflex.

Gastric distention is known to stimulate gallbladder contraction as well as gastric acid and pancreatic exocrine secretion by way of neural reflexes. Gallbladder distention, in turn, has been shown to affect sphincter of Oddi motility. Since gastric distention may accompany endoscopic or operative biliary manometry, we tested the hypothesis that gastric distention alters sphincter of Oddi motility. In the prairie dog model, gastric distention with acid (0.1 M hydrochloric acid, pH 1.3) and alkaline (10(-5) sodium hydroxide, pH 8.8) isotonic saline solutions both resulted in significant increases in sphincter of Oddi phasic wave frequency, amplitude, and motility index. Similarly, gallbladder pressure increased during both distention periods, thus confirming the previously described pylorocholecystic reflex. These responses were abolished by systemic pretreatment with atropine, suggesting that this reflex is cholinergically mediated. These data suggest the presence of a gastrosphincter of Oddi reflex whereby gastric distention stimulates sphincter of Oddi motility in the prairie dog. We conclude that gastric distention is an important variable to be controlled when performing endoscopic or operative sphincter of Oddi manometry.