Arterial bypass of the descending thoracic aorta with the BioMedicus centrifugal pump

Bypass of the descending thoracic aorta is frequently advocated as an adjunct for repair of traumatic tears and degenerative aneurysms. Many methods of bypass have been proposed to provide distal perfusion and reduce left ventricular afterload during cross-clamp of the thoracic aorta. We describe a simple method of direct arterial (aortoaortic or aortofemoral) bypass using the BioMedicus centrifugal pump with limited systemic heparinization.     

Traumatic tears of the thoracic aorta: improved results using the Bio-Medicus pump

Traumatic disruption of the descending thoracic aorta is a relatively rare but dramatic injury. Controversy remains regarding the use of shunts during operative repair. Discouraged by our results using the "no shunt" technique, we adopted the recently reported technique using the Bio-Medicus pump for left atrium-femoral artery bypass without heparin sodium. At Charlotte Memorial Hospital and Medical Center, 39 patients were treated for tears of the descending thoracic aorta between January 1979 and October 1988. Eight patients died before repair could be completed. Four patients underwent repair using femorofemoral bypass with 1 death and no instances of paraplegia. Fifteen patients had repair using the no-shunt technique with 4 deaths and three instances of paraplegia. Since January 1986, 12 patients have been treated using the Bio-Medicus heparinless pump with no deaths and no instances of paraplegia. We present our experience to confirm the reports of others regarding the efficacy of this technique. We believe it reduces the morbidity and mortality associated with this serious injury and aids in the hemodynamic management of the patient during aortic clamping.     

Beneficial Circulatory Support by Left Heart Bypass with a Centrifugal (BioMedicus) Pump for Aneurysms of the Descending Thoracic Aorta

Abstract: 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.     

Spinal cord ischemia following operation for traumatic aortic transection

The danger of irreversible ischemic damage to the spinal cord following repair of traumatic aortic rupture has prompted many techniques designed to decrease this risk. Surgical repair was performed on 41 consecutive patients, using four different methods. These included: group 1 (15 patients), left-heart pump bypass with systemic administration of heparin; group 2 (7 patients), heparinized shunt from the ascending aorta to the descending aorta or to the femoral artery; group 3 (14 patients), heparinized shunt from the left ventricle to the aorta or femoral artery; group 4 (5 patients), aortic cross-clamp only. Spinal cord ischemia was not seen in groups 1 or 2, but paraparesis or paraplegia developed in 4 patients in group 3. Severe shock accompanied rupture in all patients in group 4, and no time was taken for a shunt or bypass. Four of the 7 deaths occurred in the operating room in patients who had arrived moribund and in severe shock. In our experience, shunts from the left ventricle to the aorta have failed to protect the spinal cord against ischemia. Left-heart bypass or aorta-to-aorta shunts are now our procedure of choice.     

Acute Traumatic Disruption of the Thoracic Aorta: A Ten-Year Experience

During a ten-year period, 44 patients were treated for acute traumatic disruption of the thoracic aorta. Of the 44 patients, 21 had operative repair within 48 hours of injury (Group 1); 14 patients had operative therapy electively delayed for 2 to 79 days (Group 2); 5 had operative therapy electively delayed indefinitely (Group 3); 2 had immediate operative repair when a delayed diagnosis was made at 21 and 56 days, respectively (Group 4); 1 patient died during angiography and 1 refused operation (Group 5). Mortality was as follows: Group 1, 24%; Group 2, 14%; Group 3, 0; Group 4, 100%; and Group 5, 100%. All operative deaths occurred in the subgroup of 23 patients in whom left heart bypass was utilized.Immediate operative intervention with a heparinized shunt is preferable as soon as the diagnosis of thoracic aortic disruption has been established, but elective delay of operation in patients with severe concomitant injuries can be achieved safely with beta blockade and antihypertensive therapy.     

Management of ruptured thoracic aortic aneurysms

Nine cases of emergency resection of the thoracic aorta without temporary shunt or cardiopulmonary bypass are presented. Five were acute traumatic transections of the descending thoracic aorta secondary to blunt trauma. All five patients survived without sequelae. Four of the patients had ruptured arteriosclerotic aneurysms, including one aortobronchial fistula and one aortobronchial esophageal fistula. Two of these four patients survived without sequelae and two died in the postoperative period. One of the two latter patients had paraplegia. A review of the different methods of prevention of ischemic damage to the spinal cord and abdominal viscera is presented. Use of simple aortic cross clamping in the emergency situation for both acute traumatic transections of the aorta and ruptured arteriosclerotic aneurysms of the thoracic aorta is justified.     

Thoracic aneurysmectomy utilizing direct left ventriculofemoral shunt (TDMAC-heparin) bypass.

Use of a temporary heparin-coated ventriculofemoral shunt in 2 patients in the successful management of traumatic aneurysms of the descending thoracic aorta is described. Safe and effective bypass protection can be achieved by direct ventriculofemoral diversion when cannulation of the left subclavian artery or ascending aorta is hazardous. The use of a heparinized shunt bypass without systemic anticoagulation considerably simplifies the operation.     

Clamp/repair: a safe technique for treatment of blunt injury to the descending thoracic aorta

Debate exists with regard to the use of pump bypass, shunt bypass, or clamp/repair techniques in treating injuries to the descending thoracic aorta. The objective in using any of these techniques is to minimize the complications of paraplegia and renal failure, while achieving the lowest possible mortality. During an eighteen-year period, 45 patients were seen with acute blunt injury to the descending thoracic aorta. The shunt bypass method of repair was used in 1; pump bypass in 8; and clamp/repair in 23. There were desperate unsuccessful attempts to resuscitate and control hemorrhage in 13 patients, 1 of whom was placed on portable pump bypass. Thirty-two patients survived resuscitation and operation, and 26 were long-term survivors. Among surviving patients with permanent paraplegia, 2 underwent pump bypass and 1, the clamp/repair technique. Four other patients were seen with paraplegia or paresis and had reversal of the paralysis. The clamp/repair technique was used in these patients with clamp times ranging from 35 to 62 minutes (mean, 47.4 +/- 13.3 minutes). Renal failure did not occur in any patient, despite clamp times of up to 62 minutes (mean, 37.5 minutes). Excluding patients seen in a moribund condition, mortality most often was secondary to neurological or multisystem injury. Debate continues concerning intraoperative management of this highly lethal vascular injury. The data presented here support the historical composite experience that clamp/repair is a safe and efficacious technique that minimizes paraplegia and mortality.     

Repair of lesions of the descending thoracic aorta with the TDMAC-heparin shunt

Utilizing a heparinized tridodecylmethylammonium chloride (TDMAC) shunt makes it possible to treat various surgical diseases of the descending thoracic aorta without cardiopulmonary bypass. Since the initial report by Gott and associates on the use of the heparinized shunt, few subsequent clinical trials have appeared in the literature. Six patients with Type III dissecting thoracic aneurysm, acquired and congenital coarctation of the aorta, saccular arteriosclerotic aneurysm, and transection of the descending thoracic aorta were operated upon by means of this technique. Only one patient had more than 500 ml. of chest tube drainage in the first 8 hours postoperatively. There were no instances of paraplegia, renal failure, or death. This technique is also recommended for repair of innominate artery aneurysms, endarterectomy of the innominate or subclavian artery, arch aneurysm, penetrating injuries of the thoracic aorta, and proximal abdominal aneurysms. Surgical indications, operative management, and postoperative follow-up are discussed.     

A centrifugal pump for graft replacement of the descending thoracic or thoraco-abdominal aorta

Between January 1987, and December 1988, 14 cases of descending thoracic or thoraco-abdominal aortic aneurysm underwent operation using a prosthetic graft replacement. In order to avoid hypoperfusion to distal organs and proximal hypertension during aortic cross-clamping, two different adjuncts were used and the effectiveness of those methods were compared according to the results of surgery. Seven patients were treated with a temporary shunt of heparin-bonded tube from the left axillary artery to left femoral artery, or else Dacron vascular prosthesis from right axillary artery to right femoral artery (Group I). In Group II (seven patients), left heart bypass was performed, using a centrifugal pump from the left atrium to the left femoral artery with minimal heparinization. In Group I, there were two hospital deaths, due to respiratory and hepatic failure respectively, and paraplegia has occurred in one case. In Group II, there was no death during a post-operative observation period of 5-15 months, and there was no case of paraplegia. We think that temporary left heart bypass with a centrifugal pump seems to be the most useful method today for graft replacement of the descending thoracic or thoraco-abdominal aorta.     

Left Atrial-Aortic/Femoral Bypass with a Centrifugal Pump without Systemic Heparin during Surgery on the Descending Aorta

Abstract: 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 postop-eratively 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.     

Traumatic rupture of the thoracic aorta. A clinicopathological study

In a county hospital serving a population of roughly 240,000, the hospital records from the period 1982 to 1987 included 27 patients who presented with traumatic rupture of the thoracic aorta. Eighteen patients died instantaneously, one was dead on admission, five died in hospital and three survived operation. Two patients had direct cross clamping of the aorta and Dacron interposition graft soon after admission; both survived. The third patient had a Gott shunt and Dacron interposition graft the day after the accident and survived with paraplegia. In all patients who died in hospital except one, the condition was not diagnosed before death. We conclude that traumatic rupture of the thoracic aorta occurs more frequently than is generally thought. Although most patients die at the scene of the accident, a liberal use of angiography is indicated in all trauma cases admitted to hospital with a history of a forceful deceleration or acceleration injury.     

Aneurysms of the descending aorta: surgical experience with three methods of adjunct procedures

Thirteen patients were surgically treated for the repair of aneurysms of the descending aorta, using three different types of adjunct procedures--an external temporary bypass with a vascular prosthesis, a tridodecylmethylammonium chloride (TDMAC) or a partial cardiopulmonary bypass. There was no operative death, though one patient died 73 days following surgery. Significant intraoperative morbidity occurred in 3 patients: one had ventricular fibrillation and the other two massive hemorrhages. There was no instance of paraplegia or renal failure. The only significant complication that developed was pulmonary insufficiency in two patients with a pump bypass. The mean operative time and the mean aortic occlusion time in patients with the TDMAC shunt were shorter than the times in patients with the vascular prosthetic shunt or the pump bypass. TDMAC shunt required no special equipment and cannulation was simpler and safer.     

Aneurysms of the descending aorta: Surgical experience with three methods of adjunct procedures

Thirteen patients were surgically treated for the repair of aneurysms of the descending aorta, using three different types of adjunct procedures—an external temporary bypass with a vascular prosthesis, a tridodecylmethylammonium chloride (TDMAC) or a partial cardiopulmonary bypass. There was no operative death, though one patient died 73 days following surgery. Significant intraoperative morbidity occurred in 3 patients: one had ventricular fibrillation and the other two massive hemorrhages. There was no instance of paraplegia or renal failure. The only significant complication that developed was pulmonary insufficiency in two patients with a pump bypass. The mean operative time and the mean aortic occlusion time in patients with the TDMAC shunt were shorter than the times in patients with the vascular prosthetic shunt or the pump bypass. TDMAC shunt required no special equipment and cannulation was simpler and safer.     

Reappraisal of surgical treatment of traumatic transection of the thoracic aorta

Since Crawford's report in 1973, repair of traumatic transection of the thoracic aorta without shunt or bypass has emerged as a popular technique which simplifies the operation and avoids use of heparin. Growing evidence, however, indicates that the incidence of paraplegia is higher with this method and may outweigh its advantages. With this in mind, we have examined our experience with 40 patients who underwent repair of aortic transection from 1975-1988. The operated patients in our series all survived. Fourteen were repaired using some type of bypass or shunt, none of whom developed paraplegia. The remaining 26 patients were repaired without a shunt and 9 (34.6%) developed paraplegia or paraparesis (p less than 0.02). Paraplegia was related to aortic occlusion time (p less than 0.002). It did not occur in 11 patients with times less than 27 minutes, but happened in 2 of 8 patients with times between 28 and 35 minutes and in all 7 patients with clamp times over 35 minutes. These data suggest that shunt or bypass should be used in most cases of aortic transection.     

Blunt injuries of the thoracic aorta.

We managed 51 patients with thoracic aortic injuries caused by blunt trauma between 1977 and 1990. Forty-nine injuries were located in the upper descending aorta and one each in the ascending aorta and aortic arch. Three patients arrived moribund and underwent thoracotomy for resuscitation, and all died. The diagnosis was confirmed by aortography in 48. One patient died of aortic rupture, 1 died of hypoxemia, and 1 refused operation and died. Forty-four patients had aortic repair, 42 with graft insertion. Gott shunts were placed in 23 with 3 cases of paraplegia (13%). Simple cross-clamping was used in 19 with 1 case of paraplegia (5.2%). We found statistically significant differences between the cross-clamp times of patients without paraplegia compared with those in whom paraplegia developed in both the shunt and no-shunt groups. Logistic regression analysis showed that the only factor significantly associated with paraplegia was cross-clamp time. There were two postoperative deaths (4.4%). Seven patients had medical therapy initially and aortic repair was delayed to allow other injuries to stabilize. Before aortic repair, 18 patients had intraarterial pressure monitoring and 34 received beta-blockers or antihypertensive drugs. We conclude that aortic repair with graft insertion is usually successful in nonmoribund patients, simple cross-clamping is associated with a relatively low risk of paraplegia, the incidence of paraplegia is directly associated with the duration of cross-clamp time, and selected patients can be managed medically while awaiting aortic repair.     

Measurement of spinal cord ischemia during operations upon the thoracic aorta: initial clinical experience.

Paraplegia has been an unpredictable, devasting complication following operations upon the thoracoabdominal aorta for over 30 years. The frequency ranges from 0.5% with operations for coarctation to as high as 15% following surgery for thoracoabdominal aneurysms. Both uncertainty and controversy exist about the value of different protective methods during aortic crossclamping (AXC): heparinized shunts, partial bypass, and reimplantation of intercostal arteries. This report describes the authors' initial clinical experience with a highly sensitive indicator of spinal cord ischemia, somatosensory evoked potentials (SEP) in an attempt to prevent paraplegia associated with surgical procedures on the thoracoabdominal aorta. Seven consecutive patients (one coarctation, five thoracic aneurysms, one thoracoabdominal aneurysm) underwent continuous operative monitoring of SEP. Cortical response to simultaneous electrical stimulation (20 mAmps, 0.6 mSec., 2.3 cps) of both the right and left posterior tibial nerves was recorded before, during, and after AXC, and following operation. When ischemic changes were detected by SEP, increasing distal circulation by different maneuvers (heparinized shunt, femoral-femoral bypass, reimplantation of intercostal arteries) reversed these changes. In two patients with thoracic aneurysms, ischemic changes appeared within three minutes after AXC and all potentials disappeared in nine minutes. Rapid insertion of a graft (AXC 28 and 37 minutes) resulted in SEP return 40 minutes following restoration of flow. These changes were prevented by a heparinized shunt in two patients, femoral/femoral bypass in one, and T8-T9 intercostal reimplantation in one. No SEP changes occurred in the patient with coarctation. No postoperative neurologic complications occurred. Continuous operative monitoring of SEP has exciting possibilities for preventing paraplegia. It is simple, highly sensitive, and seems to provide a precise measurement of adequacy of circulation to the spinal cord.     

Surgical treatment of acute traumatic tear of the thoracic aorta.

Acute traumatic tear of the thoracic aorta is a severe injury with a high mortality rate. This condition requires expeditious evaluation and prompt surgical intervention in order to improve patient survival. The experience at the authors' institution from 1971 to 1987 includes 41 patients who sustained acute traumatic tear of the thoracic aorta and reached the hospital alive. The purpose of the study was to evaluate the surgical management of this injury with regards to mortality rate and the incidence of spinal cord injury. Five patients died from exsanguination before definitive repair could be undertaken. Thirty-six patients had repair of traumatic aortic tear in the area of the isthmus. Nine patients were operated upon with the clamp and sew technique, 20 patients had a heparin-bonded shunt placed, and seven patients were treated by repair with cardiopulmonary bypass. There were five operative deaths that were not related to the technique employed. Two patients without preoperative evidence of spinal cord injury developed paraparesis. No patient had postoperative paraplegia. Despite rapid transport, expeditious evaluation, and emergency thoracotomy, some patients die from exsanguination prior to definitive repair. Even with the provision of distal aortic perfusion during clamping, the risk of spinal cord injury is not eliminated.     

Paraplegia following surgery of the descending thoracic aorta

Paraplegia remains an uncontrollable complication of aortic reconstructive surgery. Twenty-one consecutive patients undergoing surgery at the Royal Adelaide Hospital for lesions of the descending thoracic aorta were reviewed. Those patients suffering an acute traumatic transection had a much higher rate of postoperative paraplegia (40%) than those undergoing elective reconstruction of chronic aneurysms (10%). The incidence of paraplegia after surgery for an acute transection when bypass was not employed was greater than 50%. In contrast, the outcome was successful in all patients who underwent reconstruction using left heart extracorporeal bypass. Based on these findings, the routine use of bypass during reconstruction of the thoracic aorta is recommended, particularly for acute traumatic transection.     

Acute traumatic isthmic aortic rupture. Long-term results in 49 patients.

Forty-nine patients who sustained acute traumatic rupture of the aorta at the level of the isthmus were treated in our hospital between 1976 and 1990. Four patients died before surgery and 45 patients were operated upon using a pump oxygenator partial bypass in all but 2 cases (1 clamp and sew and 1 shunt). The tear was circumferential in 33 and partial in 12 cases. Direct suture was used in the 12 partial and in 21 of the circumferential tears. A dacron tube was used in 12 patients. Hospital mortality was 3 resulting from brain damage, prolonged shock before surgery and necrosis of the colon 4 weeks after operation. No paraplegia was observed. There were 2 cases of neurological disturbance (2 spinal cord dysfunction 5 and 8 days, respectively, after surgery). These complications were transient. Among the 42 survivors, 1 was lost to follow-up. The clinical aortic status of the remaining 41 was excellent. Aortic reconstitution as assessed by digital aortic angiography was excellent in the 33 cases examined with 2 exceptions (graft stenosis, false aneurysm). Our experience and review of a large series indicate: the use of a partial bypass with pump oxygenator decreases the probability of medullary ischemia, but the risk of spinal cord ischemia is not eliminated. When intra-abdominal lesions are life-threatening, laparotomy must preceed thoracotomy. Clinical results assessed in long-term survivors are excellent, especially after direct repair.