James J. Klein

Risk factors for rupture of chronic type B dissections

OBJECTIVE This study was an attempt to determine risk factors for rupture and to improve management of patients with type B aortic dissection who survive the acute phase without operation. METHODS We studied 50 patients by means of serial computer-generated 3-dimensional computed tomographic scans. All patients who did not undergo operative treatment before the completion of at least 2 computed tomographic scans a minimum of 3 months apart after an acute type B dissection were included in the study. The median duration of follow-up was 40 months (range 0.9-112 months). Only 1 patient died of causes unrelated to the aneurysm during follow-up. Nine patients had fatal rupture (18%); 10 patients underwent elective aneurysm resection because of rapid expansion or development of symptoms, and 31 patients remained alive without operation or rupture. Possible risk factors for rupture in patients in the rupture, operative, and event-free groups were compared, as were dimensional data from first follow-up and last computed tomographic scans. RESULTS Older age, chronic obstructive pulmonary disease, and elevated mean blood pressures were unequivocally associated with rupture (rupture versus event-free survival, P <.05), and pain was marginally significantly associated. Analysis of dimensional factors contributing to rupture was complicated by the fact that patients who underwent elective operation had significantly larger aneurysms and faster expansion rates than did either of the other groups, leaving comparisons of aneurysmal diameter between groups with and without rupture showing only marginal statistical significance. The last median descending aortic diameter before rupture in the rupture group was 5.4 cm (range 3.2-6. 7 cm). CONCLUSIONS In an environment in which patients with large and rapidly expanding aneurysms are usually referred for surgical treatment, older patients with chronic type B dissections, especially if they have uncontrolled hypertension and a history of chronic obstructive pulmonary disease, are significantly more likely to have rupture than are younger, normotensive patients without lung disease. Neither the presence of a persistently patent false lumen nor a large abdominal aortic diameter appears to increase the risk of rupture. Overall, our nondimensional data strikingly resemble the natural history of patients with nondissecting aneurysms, suggesting that calculations derived from data on chronic descending thoracic and thoracoabdominal aneurysms would provide an overly conservative individual estimate of rupture risk for patients with chronic type B dissection, who tend toward earlier rupture of smaller aneurysms. A more aggressive surgical approach toward treatment of patients with chronic type B dissection seems warranted.

Natural history of descending thoracic and thoracoabdominal aneurysms

BACKGROUND A review of 165 patients with chronic dissecting and degenerative aneurysms of the descending thoracic and thoracoabdominal aorta initially managed nonoperatively was carried out to ascertain factors associated with a high risk of rupture. METHODS Changes in the aneurysms were followed with three-dimensional reconstructions of computed tomograph scans. Risk factors were compared in patients with dissecting and nondissecting aneurysms who experienced rupture, in whom operation was recommended during the course of follow-up, and in those without rupture or operation. RESULTS Nondimensional variables associated with an enhanced risk of rupture include age, the presence of chronic obstructive pulmonary disease, and even uncharacteristic continued pain. Patients with rupture of dissections had significantly higher blood pressures than survivors, and significantly smaller maximal descending thoracic aortic diameters (median 5.4 cm) than patients with rupture of degenerative aneurysms (median 5.8 cm). The extent of the aneurysm, as reflected by the maximal abdominal aortic diameter, was a significant risk factor for rupture only in nondissecting aneurysms. Mortality from rupture was significantly higher in patients with chronic dissections than in patients with nondissecting aneurysms: 9/10 vs 26/34 (p = 0.004). CONCLUSIONS Almost 20% of patients followed nonoperatively succumbed to rupture, suggesting that a more aggressive surgical approach toward patients with chronic aneurysms of the descending thoracic and thoracoabdominal aorta is warranted. An individualized risk of rupture within 1 year can now be calculated, and patients whose operative risk is lower than their calculated risk should be offered elective surgery.

Application of biological glue in repair of intracardiac structural defects.

BACKGROUND BioGlue (Cryolife Inc, Kennesaw GA) was introduced as an alternative tissue sealant. Its most common application has been in repairs of acute dissections of the aorta. There is no reported experience with its use in the repair of intracardiac structural defects. METHODS In 5 patients BioGlue was used as an adjunct in repairs of complex intracardiac structural defects. It was used during patch repair of posterior mitral annular defects in 2 patients and aortic annular defect in 1 patient in the presence of active endocarditis. It was also used in 1 patient with a chronic atrioventricular groove pseudoaneurysm following mitral valve replacement, and in 1 patient during repair of a postinfarction posterior ventricular septal rupture. RESULTS There were no hospital or late deaths. Immediate intraoperative transesophageal echocardiography and late follow-up echocardiography documented complete and durable repair of all defects without recurrence. At follow-up all patients are in New York Heart Association class I-II, 6 to 29 months postoperatively. No patient has suffered late complications or exhibited signs of glue embolization. CONCLUSIONS BioGlue was found to be an effective adjuvant to the standard techniques used for the repair of intracardiac structural defects of various etiologies. Long-term follow-up is recommended to determine its long-term safety in this application.

Postoperative blood loss and transfusion associated with use of Hextend in cardiac surgery patients at a blood conservation center

BACKGROUND: Hydroxyethyl starch (HES) solutions are readily available colloids, but their widespread use is shadowed by controversies surrounding their effects on bleeding. This retrospective study was conducted to evaluate the relationship between Hextend (HEX; Hospira, Inc.) doses of 1 to 20 mL/kg and allogeneic transfusion and 24‐hour chest tube drainage (CTD) in cardiac surgeries at a blood conservation center.

Does acute normovolemic hemodilution work in cardiac surgery

To the Editor:—In a recent article by Höhn et al., it was concluded that acute normovolemic hemodilution (ANH) in addition to aprotinin was not beneficial in preventing allogeneic blood transfusions compared to aprotinin alone in cardiac surgery. In this randomized, controlled trial, the patients were hemodiluted to a hematocrit of 28% pre–cardiopulmonary bypass (CPB). The transfusion threshold was set at 17% during CPB and at 25% for post-CPB. The total fluid replacement was in excess relative to the amount of ANH (autologous blood) removed (6.4 2.1 l of crystalloid, 2.0 0.7 l of colloid). This led to excessive hemodilution, reducing the hematocrit below the transfusion threshold in the ANH group. Indeed, 50% of the patients in the ANH group required either all (33%) or a portion (22%) of the autologous blood to be transfused during CPB, thus negating its positive effects on erythrocytes and coagulation protection. Consequently, allogeneic erythrocyte transfusion rates and the indirect clinical markers for surgical bleeding (cell saver and 24-h chest tube drainage) were not different between the two groups. One of the goals of ANH is to protect the autologous blood from the negative effects of CPB and to return it after heparin neutralization. Additional hemodilution occurs with the onset of CPB; therefore, hemofiltration or ultrafiltration and/or diuresis should have been employed to remove excess fluid. Alternatively, ANH can be performed just prior to the onset of CPB (by diverting heparinized blood into a storage bag), thus preventing excessive dilutional anemia. The criteria for exclusion from this study were left main disease, severe aortic stenosis, recent myocardial infarction, unstable angina, ejection fraction below 30%, severe carotid stenosis, combined coronary artery bypass grafting and valve cases, respiratory insufficiency, renal insufficiency, and anemia (hemoglobin 12 g/dl). This exclusion process resulted in the selection of a group of patients that we know are at low risk for allogeneic transfusions. Our data (shown below) and those of other investigators demonstrate that patients presenting with adequate hemoglobin levels (average starting hematocrit of 43.3%, body surface area of 1.86) rarely require allogeneic blood. At our institution, the cardiac surgery program utilizes a multidisciplinary approach to blood conservation. In over 300 cardiac surgery cases (coronary artery bypass grafting, valves, and combined procedures), we remove on average 1280 ml of ANH blood per case (based on a formula to reach a target hematocrit on bypass of 20%). The average amount of fluid used for replacement was 1680 ml of crystalloid and 591 ml of colloid (Hextend, Abbott Laboratories, North Chicago, IL). Hemofiltration or ultrafiltration and/or induced diuresis is frequently utilized on CPB to remove excess fluids and to reduce the dilutional effect from the CPB prime. The starting hematocrit averages 39%. We use -aminocaproic acid for low-risk cases and reserve aprotinin (Trasylol, Bayer, West Haven, CT) for high-risk cases. The total amount of cell saver returned is approximately 200 ml, and 24-h chest tube drainage is 428 ml. Allogeneic transfusion rates for packed erythrocytes, fresh frozen plasma, and cryoprecipitate are 11%, 3%, and less than 1%, respectively.