Beneficial circulatory support by left heart bypass with a centrifugal (BioMedicus) pump for aneurysms of the descending thoracic aorta

Cerebrospinal fluid drainage to prevent paraplegia during thoracic and thoracoabdominal aortic aneurysm surgery: a systematic review and meta-analysis

OBJECTIVES

We undertook a quantitative systematic review of randomized controlled trials (RCTs) and observational studies to determine the effectiveness of cerebrospinal fluid (CSF) drainage to prevent paraplegia in thoracic aneurysm (TA) and thoracoabdominal aortic aneurysm (TAAA) surgery.

METHODS

We included RCTs and cohort studies that met the following criteria: elective or emergent aneurysm surgery involving the thoracic or thoracoabdominal aorta, documentation of postoperative neurologic deficits, and patient age older than 18 years. We excluded studies that reported results in 10 or fewer patients and duplicate publications. We identified eligible studies by searching computerized databases, our own files, and the reference lists of relevant articles and review articles. Database searching, eligibility decisions, relevance and method quality assessments, and data extraction were performed in duplicate with prespecified criteria.

RESULTS

Of 372 publications identified in our search, 14 met our eligibility criteria. Three RCTs reported 289 patients with type I or type II TAAA. Lower limb neurologic deficits occurred in 12% of patients who underwent CSF drainage and 33% of control subjects (number needed to treat, 9; 95% confidence interval [CI], 5-50). The pooled odds ratio (OR) for development of paraplegia in patients in the CSF drainage group was 0.35 (P =.05; 95% CI, 0.12-0.99). Similar results were found in five cohort studies with a control group (pooled OR, 0.26; P =.0002; 95% CI, 0.13-0.53). When all studies were considered together the pooled OR of TA and TAAA was 0.3 (95% CI, 0.17-0.54). There was no statistical heterogeneity among studies included in the meta-analysis. In six cohort studies without a control group, the incidence of paraplegia in high-risk TA and TAAA was 7.6%.

CONCLUSIONS

Evidence from randomized and nonrandomized trials and from cohort studies support the use of CSF drainage as an adjunct to prevent paraplegia when this adjunct is used in centers with large experience in the management of TAAA.

A modified technique of atriofemoral bypass for visceral and distal aortic perfusion in thoracoabdominal aortic surgery

Modified atriofemoral bypass (AFB) was used for repair of thoracoabdominal aortic aneurysms (TAAA). The primary circuit consisted of a centrifugal pump and heat exchanger to perfuse and warm the systemic circulation. A parallel secondary circuit with a second heat exchanger perfused the viscera with cold blood. A progressive sequential cross-clamping technique was used. This technique offers theoretical hemodynamic and metabolic advantages and may prove to be useful in preventing ischemic and reperfusion injury to the spinal cord and kidneys.

Developing surgical intervention criteria for thoracic aortic aneurysms

In summary, the development of intervention criteria is a complex and challenging endeavor. Specific examination of this issue is crucial to the appropriate clinical care of patients. With these objectives in mind, we have drawn upon our clinical experience to design, by way of statistical analysis, reasoned size criteria for intervention. These intervention criteria must be carefully weighed against the patient's age, overall physical condition, and anticipated life expectancy. We have approached the development of criteria for intervention using statistical methodology from the standpoint of preventing complications (i.e., dissection and rupture). Symptomatic states, organ compression, concomitant aortic insufficiency, and acute ascending aortic dissection are well-accepted general indications for surgical intervention regardless of aortic size. The appendix incorporates the size criteria developed in the present study as an integral component within a comprehensive strategy for managing patients with TAA. This study confirms that aneurysms of the thoracic aorta are potentially lethal, that attentive follow-up is critical, and that adverse events can be anticipated based on size criteria. As we continue to expand our database, we hope to refine further statistically-based recommendations for surgical intervention. Multi-institutional patient enrollment, with the concomitant statistical power of larger patient numbers, would considerably strengthen this type of analysis.

What is the appropriate size criterion for resection of thoracic aortic aneurysms?

Although many articles have described techniques for resection of thoracic aortic aneurysms, limited information on the natural history of this disorder is available to aid in defining criteria for surgical intervention. Data on 230 patients with thoracic aortic aneurysms treated at Yale University School of Medicine from 1985 to 1996 were analyzed. This computerized database included 714 imaging studies (magnetic resonance imaging, computed tomography, echocardiography). Mean size of the thoracic aorta in these patients at initial presentation was 5.2 cm (range 3.5 to 10 cm). The mean growth rate was 0.12 cm/yr. Overall survivals at 1 and 5 years were 85% and 64%, respectively. Patients having aortic dissection had lower survival (83% 1 year; 46% 5 year) than the cohort without dissection (89% 1 year; 71% 5 year). One hundred thirty-six patients underwent surgery for their thoracic aortic aneurysms. For elective operations, the mortality was 9.0%; for emergency operations, 21.7%. Median size at time of rupture or dissection was 6.0 cm for ascending aneurysms and 7.2 cm for descending aneurysms. The incidence of dissection or rupture increased with aneurysm size. Multivariable regression analysis to isolate risk factors for acute dissection or rupture revealed that size larger than 6.0 cm increased the probability by 32.1 percentage points for ascending aneurysms (p = 0.005). For descending aneurysms, this probability increased by 43.0 percentage points at a size greater than 7.0 cm (p = 0.006). If the median size at the time of dissection or rupture were used as the intervention criterion, half of the patients would suffer a devastating complication before the operation. Accordingly, a criterion lower than the median is appropriate. We recommend 5.5 cm as an acceptable size for elective resection of ascending aortic aneurysms, because resection can be performed with relatively low mortality. For aneurysms of the descending aorta, in which perioperative complications are greater and the median size at the time of complications is larger, we recommend intervention at 6.5 cm.

Surgical treatment for aneurysms of the descending aorta using temporary perfusion by a centrifugal pump: clinical analysis of 33 cases

Since 1987, 33 patients have undergone surgery at Kobe University Hospital for aneurysm of the descending aorta using left heart bypass with a heparin-coated centrifugal pump and heparin-coated tubes. Sixteen patients had true aneurysms of the descending thoracic aorta, 7 had thoracoabdominal aneurysms, and 10 had aortic dissection (DeBakey's Type III). Heat exchangers and oxygenators were not included in the bypass circuit in any of the cases. Perfusion time was from 42 to 205 min (average 90 min). Left heart bypass was established with 1 mg/kg of systemic heparinization in 5 cases, 0.5 mg/kg in 5 cases, and 0 mg/kg in 23 cases. There were no complications such as perioperative embolism, acidosis, or hypothermia. During aortic cross-clamping, the arterial pressure of the lower extremity was maintained above 70 mm Hg, but there was no relationship between the distal perfusion pressure and bypass flow. The urine output during left heart bypass was related to the distal perfusion flow by centrifugal pump. Of 23 patients who underwent bypass with less than 40 ml/kg/min of distal perfusion flow, 7 showed transient renal dysfunction postoperatively, and 1 developed postoperative renal failure. The other patients who were bypassed with over 40 ml/kg/min of pump flow stayed in the normal range of renal function. Postoperative paresis occurred in 2 patients, who were also perfused with less than 40 ml/kg/min of bypass flow. It could be concluded that left heart bypass by centrifugal pump is safe and acceptable as a circulatory support in the surgical treatment of aneurysm of the descending aorta.(ABSTRACT TRUNCATED AT 250 WORDS)