Surgical treatment of aneurysms of the descending thoracic aorta: an analysis of 85 patients

Bypass Techniques for Descending Thoracic Aortic Surgery

The conduct of partial left heart bypass or partial car diopulmonary bypass (CPB) during surgery involving the descending thoracic aorta or thoracoabdominal aorta is one of the most unappreciated and misunder stood extracorporeal circulation procedures in cardio vascular surgery. It is different from conventional CPB, and although some uninitiated practitioners consider it simpler, it is in fact more complicated than conven tional CPB and involves different concepts. It requires expertise and skill in regulating the flow, pressure, and oxygenation of blood going to both the proximal and distal parts of the body and management of the special bypass or shunt procedures used, specialized monitor ing, and knowledge about the protection and preserva tion of organs both proximal and distal to the aortic clamping. It demands exquisite communication and un derstanding of the unique problems faced by the sur geon, anesthesiologist, and perfusionist.

Rapid ischemic preconditioning with a short reperfusion time prevents delayed paraplegia in a rabbit model

BACKGROUND

Surgery for thoracic and thoracoabdominal aortic aneurysms can be complicated by a significant incidence of neurogenic deficits due to spinal cord ischemia. In this study, we investigated whether ischemic preconditioning (IPC) improves neurologic outcome in a rabbit model.

METHODS

Forty rabbits underwent infrarenal aortic occlusion. The IPC group (n = 20) had 10 minutes of aortic occlusion to induce spinal cord ischemia, 40 minutes of reperfusion, and 30 minutes of ischemia, whereas the control group (n = 20) had only 30 minutes of ischemia. Tarlov scoring (0, paraplegia; 4, normal) was used to evaluate neurologic functions 7 days later, and spinal cord segments (L4-L6) were stained with hematoxylin and eosin for histologic evaluation.

RESULTS

Complete paraplegia (grade 0) occurred in 15 (75%) of the 20 control animals, whereas in the IPC group, 13 (65%) of 20 animals were completely normal (grade 4) (P < .05).

CONCLUSION

IPC is beneficial for protecting against neurologic damage after transient aortic occlusion in a rabbit model; however, the protective mechanisms are not clear.

Endovascular treatment of thoracic aortic pathology: feasibility and mid-term results

OBJECTIVE

to report our experience with 21 consecutive patients treated with a thoracic stent-graft.

DESIGN

retrospective analysis.

MATERIALS AND METHODS

Between October 1998 and February 2002, 21 patients (12 male), mean age 55.6 years (range 19-86 years), were treated for aorticortic pathology localized to the descending aorta (18 patients), the aortic arch (2 patients) and the ascending aorta (1 patient) and comprising true aneurysms (8 patients), false aneurysms (6 patients), traumatic rupture (4 patients), mycotic aneurysms (2 patients), and ruptured aneurysm (1 patient). Plain chest X-rays and computed tomography was performed at 3, 6 and 12 months postoperatively and then annually.

RESULTS

the median (range) operation time was 85min (50-305min), hospital stay 6 days (3-63 days) and follow-up 24 months (5-44 months). Complications occurred in 5 patients and comprised intraoperative migration (1), type I endoleak (1), type II endoleak (1), ischemic myelopathy (1), pneumonia (2), suture granuloma (1) and common femoral artery dissection (1).

CONCLUSIONS

stent-grafting can be successfully employed to treat a wide range of thoracic aortic pathologies with a mortality, morbidity and resource utilization that is considerably less than that associated with conventional surgery. However, long term follow-up on safety and efficacy is needed.

DNA damage and repair system in spinal cord ischemia

BACKGROUND AND PURPOSE

Spinal cord ischemia-reperfusion injury may be initiated by a number of mediators, including reactive oxygen species. Recent studies have shown that human MutY homologue (hMYH), human 8-oxo-7,8-dihydrodeoxyguanine (8-oxoG) glycosylase (hOGG1), and human MutS homologue 2 (hMSH2) are important DNA mismatch repair genes. We hypothesized that ischemia-reperfusion injury in spinal cord causes DNA damage manifested by 8-oxoG production and activates the DNA repair system involving hMYH, hOGG1, and hMSH2.

METHODS

Spinal cords of rabbits were removed at 1, 3, 6, 24, and 48 hours after 30 minutes of infrarenal aortic occlusion. DNA damage was determined with 8-oxoG staining. The expression and localization of DNA repair enzymes, such as hMYH, hOGG1, and hMSH2, were studied with Western blot analysis and immunohistochemical staining. The level of apoptosis was determined with TUNEL study. Activation of caspase-3, an enzyme induced by cellular injury that leads to apoptosis by degrading cellular structural proteins, was also studied.

RESULTS

DNA damage monitored with 8-oxoG level was significantly present from 1 hour to 6 hours after reperfusion in gray matter neurons of ischemic spinal cord. The levels of hMYH, hOGG1, and hMSH2 were markedly increased in gray matter neurons at 6 hours after reperfusion. Caspase-3 was also induced at 6 hours to 24 hours after reperfusion in ischemic spinal cord. However, the peak level of TUNEL reactivity was found at 48 hours after reperfusion in spinal cord neurons.

CONCLUSION

This study has shown, for the first time, the rapid expression of DNA damage-repair processes associated with spinal cord ischemia and subsequent reperfusion.

Elective endovascular stent-graft repair of atherosclerotic thoracic aortic aneurysms: clinical results and midterm follow-up

OBJECTIVE

The purpose of this study was to evaluate the clinical and midterm results after endovascular treatment of atherosclerotic thoracic aortic aneurysms.

MATERIALS AND METHODS

Twenty-eight consecutive patients who were 53-82 years old (mean age, 71.6 years) were treated with a commercially available endoprosthesis. Subclavian transposition or bypass surgery was performed before the procedure in eight patients. Size dynamics of the aneurysms were analyzed on the basis of diameter and thrombus volume measurements obtained on three-dimensional CT reconstructions before hospital discharge (n = 22) and at the 1-year (n = 22), 2-year (n = 12), and 3-year (n = 5) follow-ups.

RESULTS

The technical success rate was 100%. There was no 30-day mortality. None of the patients had symptoms due to spinal cord ischemia. The survival rate at 1, 2, and 3 years was 96.1%, 90.9%, and 80.2%, respectively. During the perioperative period, patients presented with leukocytosis (37%), fever (36%), elevated C-reactive protein value (92%), pleural effusion (50%), and periaortic atelectasis (41%). Three early type I endoleaks sealed spontaneously. Three early type II endoleaks persisted over time, and one late type II endoleak was detected. In patients with type II endoleaks, thrombus volume of the aneurysms was constant (n = 2) or increased (n = 2). In patients without endoleaks, mean thrombus volume decreased (-53.2 +/- 56.8 mL, -40%) significantly (p = 0.001) during the first year. There was no significant interval decrease between the 1- and 2-year follow-ups (mean, -2.4 mL, p = 0.92) and between the 2- and 3-year follow-ups (mean, -0.4 mL, p = 0.68).

CONCLUSION

Endovascular treatment of atherosclerotic thoracic aortic aneurysms may result in a substantial reduction of the aneurysm sac in patients without endoleaks.

Establishment of a local cooling model against spinal cord ischemia representing prolonged induction of heat shock protein

OBJECTIVES

Paraplegia is one of the serious complications of thoracoabdominal aortic operations. Regional hypothermia protects against spinal cord ischemia although the protective mechanism remains unknown. We attempted to create a simple model of local cooling under transient spinal cord ischemia and evaluated the effect using functional and histologic findings.

METHODS

Male domesticated rabbits were divided into 3 groups: control, normothermic group (group N), and local hypothermic group (group H). A balloon catheter was used for spinal cord ischemia by abdominal aortic clamping. A cold pack attached to the lumbar region could lower the regional cord temperature initially. Neurologic function was evaluated by the Johnson score. Cell damage was analyzed by observing motor neurons with the use of hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated deoxy-uracil triphosphate biotin in situ nick end labeling (TUNEL), and immunoreactivity of heat shock protein.

RESULTS

Physiologic estimation showed that local hypothermia improved the functional deficits (group N, 1.3 +/- 0.9; group H, 4.9 +/- 0.3; P =.0020). Seven days after reperfusion, there was a significant difference in the motor neuron numbers between groups N and H (group N, 7.2 +/- 1.9; group H, 20.4 +/- 3.2; P =.0090). The number of TUNEL-positive motor neurons was reduced significantly (group N, 7.2 +/- 2.4; group H, 1.0 +/- 0.7; P =.0082). Heat shock protein immunoreactivity was prolonged up to 2 days after reperfusion in the hypothermic group.

CONCLUSIONS

These results suggest that local hypothermia extended the production of heat shock protein in spinal cord motor neurons after reperfusion and inhibited their apoptotic change.

Prevention of paraplegia in transluminally placed endoluminal prosthetic grafts for descending thoracic aortic aneurysms

OBJECTIVE

To evaluate the efficacy of a temporary balloon occlusion test for the prevention of paraplegia following transluminally placed endoluminal prosthetic grafts for descending thoracic aortic aneurysms.

SUBJECTS AND METHODS

Two occlusion balloons were inserted via the brachial and femoral arteries and positioned in the proximal and distal neck of the descending thoracic aortic aneurysms using fluoroscopy. After temporary occlusion of the thoracic aorta by inflation of both the proximal and distal balloons, the evoked spinal potential was measured for 15 mins. A maximum amplitude during temporary balloon occlusion test decreasing by more than 20% of the pre-balloon occlusion level was considered to be significant, enough to not perform transluminally placed endoluminal prosthetic grafts, but instead an open repair. The test was applied in 12 cases (9 males and 3 females, 50-86 years old). All aneurysms were located between the Th6 and Th12 with a maximum diameter of 40-70 mm, and average of 56 mm.

RESULTS

The changes in maximum amplitude of evoked spinal potential remained within 20% of the value before balloon occlusion in 11 cases. Transluminally placed endoluminal prosthetic grafts were performed in these 11 cases and no instance of paraplegia or other complication relating to the test was observed. Deployment of stent-grafts was successful in 10 cases (91%).

CONCLUSION

It is suggested that the preoperative measurement of evoked spinal potential during temporary balloon occlusion is clinically useful for the assessment of the risk to paraplegia occurring in transluminally placed endoluminal prosthetic grafts.

Is distal anastomosis only to the true channel in chronic type B aortic dissection justified?

BACKGROUND

We investigated long-term outcomes of the distal false lumen of the aorta and aortic branches after distal anastomosis of the graft only to the true lumen in chronic type B aortic dissection.

METHODS

From November 1979 until June 1998, we treated 98 patients without Marfan syndrome who had chronic type B aortic dissection and underwent replacement of the descending aorta, 79 of whom had distal anastomosis to the true lumen only. The celiac artery originated from the false lumen in 11 patients, superior mesenteric artery in 5, right renal artery in 19, and left renal artery in 16.

RESULTS

There were 12 (15.1%) early deaths. Spinal cord ischemia was detected in 5 patients. Postoperative follow-up was achieved in 67 patients, and 13 patients died. Postoperative survival at 10 years was 67.6% +/- 7.1%. Eight patients had complete occlusion of the distal false lumen, 54 patients had occlusion of the false lumen down to the celiac artery, and 5 patients had a patent false lumen. Four patients required further replacement of the thoracoabdominal aorta.

CONCLUSIONS

In non-Marfan patients with chronic type B aortic dissection, the false lumen distal to the graft anastomosis was likely to be thrombosed when the graft was anastomosed to the true lumen only. Postoperative visceral circulation was not compromised, but spinal cord ischemia is a problem that remains to be solved.

Surgery for descending thoracic aortic anastomotic aneurysms with a temporary external bypass method

The surgical treatment of descending thoracic aortic anastomotic aneurysms is technically challenging. The purpose of this study was to evaluate the use of a temporary external bypass method as an intraoperative measure in the surgical treatment of anastomotic aneurysms of the descending thoracic aorta. An analysis of five consecutive patients who had undergone surgery for a collective seven descending thoracic aortic anastomotic aneurysms in our university hospital over a period of 14 years was conducted. A temporary bypass technique was used as an intraoperative measure in all the operations, four of which were performed with a right axillary to left external iliac artery bypass, while other sites were used in the remaining three. Systemic heparinization was able to be avoided in six operations and was markedly reduced in the remaining one. Although the major postoperative complication was coagulated hemothorax after six procedures, all patients recovered well and are still alive after a mean follow-up period of 8.2+/-1.5 (SEM) years. The results of this analysis led us to conclude that our temporary bypass method for treating descending thoracic aortic anastomotic aneurysm prevented the risks of anticoagulant administration for circulatory support, which contributed to the success of the operation. This method can be used as adjunct treatment for anastomotic aneurysms in the descending thoracic aorta.

Operation for chronic traumatic aortic aneurysm: when and how?

BACKGROUND

There are few guidelines for surgical intervention late after unoperated traumatic aortic rupture. We reviewed our experience and the literature to determine when and how to operate.

METHODS

Between 1987 and 1997, we treated 9 patients aged 22 to 82 years with chronic traumatic aneurysm. Seven patients underwent aneurysm resection. Two patients have not been operated on. The injury-to-operation interval ranged from 8 weeks to 18 years (mean, 4.1 years). One patient underwent median sternotomy and patch repair during hypothermic circulatory arrest. Six patients underwent left thoracotomy: 2 were operated on with left atrio-femoral bypass, and 4 with hypothermic circulatory arrest and ascending aortic cannulation.

RESULTS

There was no surgical mortality or morbidity. The 2 patients who were not operated on remained asymptomatic without radiologic change in the aneurysm after follow-up of 2 and 9 years.

CONCLUSIONS

From this limited experience and literature review, we make the following subjective observations: (1) all patients with new symptoms should be operated on promptly, and (2) asymptomatic densely calcified aneurysms detected more than 2 years after the accident can be observed by repeated tomography unless new symptoms arise.

Prevention of spinal cord ischemia by selective intercostal arterial infusion of prostaglandin E1

PURPOSE

A new protective method against the spinal cord ischemia that occurs during aortic clamping was investigated in dogs. Oxygenated blood containing prostaglandin E1 (PGE1) was administered at the clamped aortic segment, and the effect was evaluated by measurement of the sensory evoked spinal potential (SESP).

METHODS

In 30 dogs, a thoracotomy was made with dissection of the thoracic aorta. After intravenous heparin (100 units/kg) was administered, the proximal and distal descending thoracic aortas were cross-clamped for 60 minutes. Group A (n=10) received oxygenated blood at the rate of 1.0 ml/kg/min. Groups B (n=10) and C (n=10) received oxygenated blood at the same rate, with PGE1 at the dosage of 25 and 50 ng/kg/min, respectively. The infusion was continuously administered throughout the entire period of ischemia. SESP was measured with epidural electrodes before clamping, 10 and 60 minutes after clamping, and 10 and 60 minutes after declamping. Neurologic outcome was assessed at 24 hours after the operation and graded according to the method of Tarlov.

RESULTS

There was no significant hemodynamic change in any group. At 60 minutes after damping and at 10 and 60 minutes after declamping, the amplitude of SESP was lower than that at preclamping in groups A and B (p < 0.05). At 60 minutes after damping and at 10 and 60 minutes after declamping, the SESP was more markedly decreased in group A compared with groups B and C. Regarding postoperative neurologic outcome, the dogs with SESP amplitude of more than 50% of the preclamping control value at 60 minutes after clamping showed neither paralysis nor paraplegia. Seven of nine dogs with less than 50% SESP amplitude showed neurogenic deficit. In a comparison of groups A, B, and C, the Tarlov score for group A dogs was significantly lower than that for group C dogs (p < 0.05).

CONCLUSION

In this model, PGE1 administration at the rate of 50 ng/kg/min showed sufficient spinal cord protection against ischemia without a decrease in the blood pressure. Further studies are needed to determine the dose that will provide the maximal protective effect and to determine the maximum duration of ischemia against which PGE1 shows protective effects.

Transpericardial inferior vena caval cannulation in thoracic aorta operations

Surgical treatment of thoracic aneurysms is frequently performed with the aid of partial cardiopulmonary bypass. When profound hypothermia and circulatory arrest are employed, inadequate venous drainage may represent a major problem. We herein describe a technique of inferior vena caval cannulation that allows steady performance when high pump flows are imposed.

Descending thoracic aorta aneurysmectomy: left-left centrifugal pump versus simple clamping technique

Forty-six patients who had had an elective repair of a descending thoracic aortic aneurysm were reviewed, in order to investigate the efficacy of support by a centrifugal pump on distal organ perfusion and spinal cord protection during cross-clamping of the thoracic aorta. Two concurrent groups were analysed: 36 patients (78%) were supported by left atriofemoral arterial bypass with a centrifugal pump and 10 (22%) had no distal circulatory support. No patient was fully heparinized. The demographic data and preoperative characteristics of the groups, including location and type of aneurysm, were similar. The mean(s.d.) duration of cross-clamping was 37.8 (16) min in the centrifugal pump group and 42.3(21) min in the simple clamping group. Preoperative haemodynamic and laboratory data were similar in both groups. During cross-clamping, parameters of pH and blood urea varied but were better in the centrifugal pump group; changes from pre-intervention to early aortic cross-clamping time were not significant (pH, P < 0.0006; bases, P < 0.0003). Differences in creatinine values were caused mainly by the change from pre-intervention to the first postoperative day (P < 0.03); this continued throughout the hospital stay. The cerebrospinal fluid pressure measurement indicated a significant difference in time change (P < 0.0001) and mean level over time (P < 0.0002): levels were significantly lower in the centrifugal pump group throughout aortic cross-clamping. Three patients in the simple clamping group and none in the centrifugal pump group (P < 0.02) required cerebrospinal fluid drainage.(ABSTRACT TRUNCATED AT 250 WORDS)

Left atrial-aortic/femoral bypass with a centrifugal pump without systemic heparin during surgery on the descending aorta

Active or passive bypass to support the distal circulation during cross-clamping of the descending thoracic aorta has been reported to decrease the incidence of paraparesis, to reduce left ventricle afterload, and to preserve distal organ perfusion. The aim of this study was to describe and to evaluate a perfusion technique for surgery on the descending aorta in humans. Nine patients underwent surgery on the descending thoracic aorta. The left atrium was cannulated using a Carmeda bioactive surface cannula. Distal cannulation sites were the left common femoral artery or the aorta below the involved segment. The cannulae were connected to a BioMedicus centrifugal pump via Carmeda bioactive surface tubings and pump heads. No systemic heparin was used. Cross-clamp time was 51 +/- 6 min, and the pump flow was 2.3 +/- 0.2 L/min. The mean arterial pressure in the upper body was 81 +/- 4 mm Hg and 68 +/- 5 mm Hg in the lower. Seven patients were discharged from hospital. Two patients with aortic rupture died; one died on the operating table, and the other, neurologically intact, died 4 days postoperatively due to multiorgan failure. No patients suffered spinal cord injury. It is concluded that active bypass without systemic heparin during cross-clamping of the descending aorta is simple and safe.

Distal circulatory support for thoracic aortic operations: effects on intracranial pressure

Spinal cord ischemia can result from aortic clamping during thoracic aortic operations. The perfusion gradient for spinal cord perfusion is positively influenced by distal aortic pressure and negatively influenced by intracranial pressure (ICP). Hemodynamic and ICP changes were examined in a swine model of descending thoracic aortic surgery where distal aortic perfusion was achieved under one of three conditions: (1) clamping without support, (2) a passive aortofemoral shunt, or (3) a left atrium-femoral artery bypass system. With aortic clamping alone, ICP increased from 9.8 +/- 2.2 mm Hg to 15.2 +/- 2.8 mm Hg (p < 0.05). With passive shunting, ICP was decreased to 13.8 +/- 3.0 mm Hg, which was still significantly elevated above baseline. However, with active bypass, ICP remained at control level (9.8 +/- 2.2 mm Hg). Mean distal aortic pressure, which was 82 +/- 10 mm Hg in the control state, decreased to 20 +/- 0.5 mm Hg with clamping alone and to 39 +/- 9 mm Hg with passive shunting, whereas with active support, a distal pressure of 64 +/- 8 mm Hg was achieved. In contrast to passive shunting, active distal bypass results in maintenance of ICP at baseline levels and results in distal aortic pressure significantly greater than that achieved with either aortic clamping alone or passive shunting. Thus, active distal circulatory support produces the greatest salutary effect on the two determinants of the spinal cord perfusion pressure gradient: ICP and distal aortic pressure. This support modality may be the best adjunctive technique to maintain the spinal cord perfusion gradient and hence minimize the risk of ischemic injury.

Evolution of surgical techniques for aneurysms of the descending thoracic aorta: twenty-nine years experience with 659 patients

Between 1953 and 1993, 659 patients underwent descending thoracic aneurysm resection. The most common etiology was atherosclerosis. Pain was the main presenting symptom. Perioperative mortality fell from 24.2% between 1953 and 1964 to 14.3% between 1970 and 1993. Paraplegia occurred in 4.1% (27/659) patients overall and was little affected by time of operation or use of atriofemoral bypass. Paraparesis occurred in 5.9% (39/659) patients and was reduced by use of atriofemoral bypass. The low rate of paraparesis in the earlier experience was offset by the higher perioperative mortality from hemorrhage, attributable to the use of systemic heparin. The use of heparin-free circuits with centrifugal pumps should be considered in patients likely to have a clamp time greater than 30 minutes. The major source of perioperative morbidity and mortality was cardiac causes (48%) followed by perioperative hemorrhage (14.4%), pulmonary complications (14.4%), and rupture of another aneurysmal segment (12.0%). Late mortality occurred most commonly from cardiac causes (30.6% of deaths) and rupture of another aneurysm (16.3% of deaths). Improvement in results was due to general refinements of management in all areas rather than any single factor. These results indicate that complete preoperative assessment of the patient and the entire aorta is essential and that regular life-long follow-up is critical in order to avoid unnecessary morbidity and mortality from cardiac, cerebrovascular, or subsequent aneurysmal complications.

Improved distal circulatory support for repair of descending thoracic aortic aneurysms

Bleeding is a well-known problem when cardiopulmonary bypass with full systemic heparinization is used for distal support during aortic cross-clamping. The recent advent of heparin-coated cardiopulmonary bypass equipment prompted our review of 91 consecutive patients who underwent repair of descending thoracic and thoracoabdominal aortic aneurysms. Two different surgical techniques were used: 42 of 91 patients had simple aortic cross-clamping and rapid reanastomosis, whereas 49 of 91 had distal support using all heparin-coated perfusion equipment with low systemic heparinization (100 IU/kg body weight; activated coagulation time > 180 seconds). Baseline parameters, location (thoracoabdominal: 28/91; 31%), and type of aneurysm (ruptured: 14/91; 15%) were similar in both groups. Cross-clamp time was 37 +/- 22 minutes for support versus 29 +/- 13 minutes for simple clamping (p < 0.05). There were fewer revisions due to bleeding for support (1/49 patients; 2%) versus simple (4/42; 10%; p < 0.05) and fewer patients with impaired renal function requiring temporary hemofiltration for support (4/49 patients; 8%) versus simple (6/42; 14%). Hospital mortality was lower for support (5/49; 10%) versus simple (8/42; 19%). Transfusion requirements during operation were 3,732 +/- 3,458 mL for simple versus 3,392 +/- 2,058 mL for support (not significant). Chest tube drainage totaled 982 +/- 1,102 mL for simple versus 720 +/- 618 mL for support (not significant). The total volume requirements were 8,156 +/- 4,753 mL for simple versus 7,495 +/- 3,342 mL for support (not significant) during operation and 4,416 +/- 2,422 mL for simple versus 3,380 +/- 1,432 mL for support (p < 0.025) during the 24 hours after operation.(ABSTRACT TRUNCATED AT 250 WORDS)

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)

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

A comparative study between left heart bypass with a centrifugal (BioMedicus) pump and with a temporary external shunt was performed to assess the efficacy of distal organ perfusion in the surgical treatment of 31 patients with aneurysm of the descending thoracic aorta. Eighteen patients were supported with a centrifugal pump, and the remaining 13 were supported by temporary shunt with either a Gott shunt or a Dacron graft. Heparinless bypass with a centrifugal pump provided a significant decrease of intraoperative blood loss and blood transfusion by the combined application of Cell-Saver. The pressure difference between upper and lower extremities decreased (p < 0.05) in the centrifugal pump group even with aortic cross-clamping, and the urine output increased during operation. Among 13 patients supported with the temporary shunt, 3 had postoperative renal failure, and 2 died of it. All patients with a centrifugal pump survived without any complications. It could be concluded that the left heart bypass with a centrifugal (BioMedicus) pump was safe and was favorable for support of the distal circulation during aortic cross-clamping and to prevent ischemic complications such as renal failure and spinal cord injury.

Arterial shunt with pump infusion line for the treatment of chronic thoracic aortic aneurysms: the "modified shunt of Gott"

Dissection of the aneurysm is the most dangerous step during graft replacement of the descending thoracic aorta. Sudden hemorrhage may follow wall rupture or disruption of major collaterals before the aorta can be clamped. A simple modification of the classic Gott is illustrated, which makes the shunt work also as a partial bypass if needed, with rapid reinfusion of blood losses. Nineteen of 25 patients requiring resection of descending aortic aneurysms from 1982 to 1990 were treated with this method with no mortality.

Graft replacement of post-traumatic thoracic aortic aneurysm: results without bypass or shunting

From 1986 to 1991 13 cases of post-traumatic thoracic aneurysm were treated at our department. All patients had apparent thoracic injury at the time of trauma, and their mean age was 35 years. The mean time between trauma and operation was 3 years and six patients were asymptomatic. In all patients the diagnosis was made by computed tomography and angiography and all post-traumatic thoracic aneurysms were located at the aortic isthmus. No spinal cord protection by bypass or shunting was used during surgery and the clamp-and-repair method with a mean clamping time of 38 min was used in all 13 patients. No renal or neurological complications were observed postoperatively and there were no hospital deaths. The data of 202 patients who had been operated upon for post-traumatic thoracic aneurysms since 1981 have been reviewed with regard to the relationship between spinal cord protection and the incidence of postoperative paraplegia. Different methods of spinal cord protection were used in 121 patients resulting in paraplegia rate of 1.6%. In 81 patients the clamp-and-repair method was used and no case of paraplegia was observed in this group.

Management and long-term outcome of aortic dissection

All 163 patients admitted to one institution between 1975 and 1988 with aortic dissection were reviewed. Type I and type II patients received grafting of the ascending aorta, with an intraoperative mortality rate of 11%. For type III dissection, management was medical in 53 patients, while 19 required surgery for aortic rupture or expansion, with an intraoperative mortality rate of 11%. The 9- or 10-year survival rates were 29%, 46%, and 29% for types I, II, and III respectively. Of 135 patients with primary aortic dissection, 17 (13%) required subsequent aortic surgery. Cause of late death was other cardiovascular disease in 38%, rupture of another aortic segment in 18%, sudden death in 24%, and other medical conditions in 21%. Although operative therapy for types I and II dissections and reserving operation for selected type III dissections provides acceptable long-term survival, careful follow-up is necessary due to concurrent cardiovascular disease and residual aortic disease.

Visceral and limb perfusion during thoracoabdominal aortic aneurysm repair

Patients undergoing thoracoabdominal aortic aneurysm repair are at high risk of operative morbidity and death. Aortic clamping and unclamping stresses the myocardium, interrupts visceral and limb perfusion, and leads to metabolic acidosis. Use of a simple technique to preserve distal perfusion during the period of aortic clamping may reduce perioperative morbidity. We describe a technique of visceral and limb perfusion that may reduce surgical risk in high-risk patients.

Deep hypothermia and circulatory arrest as an elective technique in the treatment of type B dissecting aneurysm of the aorta

The combination of deep hypothermia and circulatory arrest has been used in a variety of cardiovascular surgical techniques and is presented in this article as an elective method in the treatment of type B dissecting aneurysms that may or may not involve the distal aortic arch. Out of 190 patients operated on with acute aortic dissection, 10 patients with type B underwent surgical procedures, between January 1985 and December 1987, four with acute dissection (less than 14 days evolution), and six with chronic dissection (more than 14 days evolution). The approach was by left posterolateral thoracotomy with cardiopulmonary bypass using femoro-femoral cannulation, deep hypothermia, and circulatory arrest. The duration of circulatory arrest was between 27 and 58 minutes, mean 37 minutes. Extracorporeal circulation (ECC) lasted between 68 and 142 minutes, with a mean perfusion time of 83.7 minutes, and temperature fell to 14 degrees C and 16 degrees C. Intrahospital mortality was 20% (two patients). No long-term mortality has been recorded. Eighty percent of the patients (eight patients) are alive and showed good evolution between 10 and 44 months following surgery, with a long-term mean survival of 24 months and 23 days. The only neurological complication was a single case of right unilateral blindness followed by complete visual recuperation. Myocardial and spinal cord protection are excellent, without any incidence of postoperative infarct or paraplegia. Postsurgical blood loss ranged from 200 to 650 mL with a mean of 385 mL. Acute renal insufficiency was not detected. We believe that the combined techniques of deep hypothermia and circulatory arrest used electively, and not just out of occasional necessity, is a viable choice that allows easier surgical manipulation of type B dissection aneurysms and complete resolution of those involving retrograde dissection to the aortic arch. In addition. this combined technique does not increase postoperative mortality in this critically dangerous disease.

Surgery of the descending thoracic aorta: spinal cord protection with the Gott shunt

From July, 1974, to July, 1987, surgical treatment of descending thoracic aortic aneurysms was performed in 173 patients at l'Hôpital du Sacré-Coeur de Montréal. The cause of the aneurysms was arteriosclerosis or medial degeneration in 83 patients, trauma in 50, dissection in 34, and a congenital malformation in 6. A single method of external shunting provided distal perfusion in all patients in the series. A 9-mm Gott aneurysm shunt was placed preferentially between the ascending aorta (67%) and the descending aorta (60%). Alternative sites of proximal cannulation (aortic arch, 9%; proximal descending aorta, 22%; left ventricle, 2%) and distal cannulation (abdominal aorta, 3%; left femoral artery, 37%) were chosen based on the location and the extent of the aortic aneurysm. No systemic heparinization was used. In the last 40 patients, a flowmeter adapted for use with the shunt allowed the recording of shunt flow (mean, 2,475 ml/min; range, 1,100 to 4,000 ml/min). Hospital mortality, including patients with ruptured aneurysms, was 15% (26/173). The mean aortic cross-clamp time was 37 minutes (range, 8 to 105 minutes). Of the 173 patients, 168 survived long enough to allow accurate clinical evaluation of the function of the spinal cord: no paraplegia or other spinal cord ischemic injury occurred. To date, our clinical experience has demonstrated the effectiveness of the 9-mm Gott shunt in preserving the functional integrity of the spinal cord during cross-clamping of the thoracic aorta.

Painless aortic dissection presenting as spinal cord ischemia

A 67-year-old woman developed a transient paraplegia as the initial manifestation of acute aortic dissection. Chest or abdominal pain was not present. Magnetic resonance imaging of the thorax demonstrated dissection of the aortic root, aortic arch, and descending aorta as well as pericardial effusion. Ultrasonography of the abdomen revealed an intimal flap in the region of the artery of Adamkiewicz. During aortic dissection, temporary obstruction of spinal arteries may result in transient paraplegia. Painless aortic dissection should be considered in patients who present with transient myelopathy.

Evolving concepts in prevention of spinal cord injury during operations on the descending thoracic and thoracoabdominal aorta

Spinal cord injury following operations on the descending thoracic or thoracoabdominal aorta remains a major problem. In certain subsets of patients, the risk of postoperative spinal cord injury is substantial. Although several adjuncts have been employed clinically to eliminate or reduce the frequency of this complication, none have proven to be completely effective. An important reason for this is the failure of these techniques to reliably and noninvasively localize the level of origin of arteries from the aorta that are critical to spinal cord circulation. Since postoperative spinal cord injury most likely results from ischemia or hypoxia of the lower segment of spinal cord, use of adjunctive techniques to preserve spinal cord function during aortic clamping by perfusing the distal aorta adequately with or without systemic hypothermia should be considered. To practically implement this, partial cardiopulmonary bypass for distal perfusion when the critical intercostal or lumbar arteries originate from the aorta distal to the excluded segment, and total cardiopulmonary bypass with systemic hypothermia and implantation of intercostal and lumbar arteries when these arteries originate from the excluded segment, can be used. In addition, whenever possible, intraoperative monitoring of spinal cord function should be performed.

Surgical treatment of aneurysms of the thoracic aorta with the aid of partial cardiopulmonary bypass: an analysis of 95 patients

We retrospectively evaluated the surgical results in 95 patients with aneurysm of the thoracic aorta who were surgically treated using partial cardiopulmonary bypass (CPB) as an adjunctive method during the past 10 years. The cause of the aneurysm was atherosclerosis in 52% and dissection in 41%. Fifty-eight percent of the patients had an aneurysm of the entire descending thoracic aorta and 14 of these patients had a thoracoabdominal aneurysm. Emergency operation was performed in 16 patients (17%). There were 14 early deaths (14.7%) within one month after operation. Postoperative complications included renal dysfunction, partial paraplegia, and hemorrhage. Renal dysfunction occurred in 7 (7.8%) of the operative survivors; 2 of the 7 required hemodialysis. Partial paraplegia was observed in 2 patients undergoing total replacement of the thoracoabdominal aorta. Neither renal dysfunction nor paraplegia was related to the duration of aortic cross-clamping. Postoperative hemorrhage necessitating reopening of the chest occurred in 8 (8.9%) of the operative survivors. Partial CPB is useful in reducing the incidence of postoperative complications among patients undergoing aortic cross-clamping for a long period.

Risk factors for the development of renal failure following the surgical treatment of traumatic aortic rupture

A retrospective study of 44 patients who were treated surgically for traumatic aortic rupture was undertaken to determine risk factors for the development of postoperative renal failure. Renal failure occurred in 11 of 41 patients (27%) eligible for analysis. The Pearson product-moment correlation showed no significant relationship between the occurrence of renal failure and the patient's age, injury severity score, initial blood pressure, or the interval between accident and thoracotomy. Renal failure was significantly correlated with cross-clamping only (r = .2751, p = .043). There was no relationship between renal failure and total cross-clamp times. The mortality rate was significantly higher for patients with renal failure.