Spinal cord protection during aortic cross-clamping using retrograde venous perfusion

Background. Paraplegia remains a devastating complication following thoracic aortic operation. We hypothesized that retrograde perfusion of the spinal cord with a hypothermic, adenosine-enhanced solution would provide protection during periods of ischemia due to temporary aortic occlusion.

Methods. In a rabbit model, a 45-minute period of spinal cord ischemia was produced by clamping the abdominal aorta and vena cava just below the left renal vessels and at their bifurcations. Four groups (n = 8/group) were studied: control, warm saline, cold saline, and cold saline with adenosine infusion. In the experimental groups, saline or saline plus adenosine was infused into the isolated cavae throughout the ischemic period. Clamps were removed and the animals to recovered for 24 hours before blinded neurological evaluation.

Results. Tarlov scores (0 = paraplegia, 1 = slight movement, 2 = sits with assistance, 3 = sits alone, 4 = weak hop, 5 = normal hop) were (mean ± standard error of the mean): control, 0.50 ± 0.50; warm saline, 1.63 ± 0.56; cold saline, 3.38 ± 0.26; and cold saline plus adenosine, 4.25 ± 0.16 (analysis of variance for all four groups, p < 0.00001). Post-hoc contrast analysis showed that cold saline plus adenosine was superior to the other three groups (p < 0.0001).

Conclusion. Retrograde venous perfusion of the spinal cord with hypothermic saline and adenosine provides functional protection against surgical ischemia and reperfusion.     

Spinal cord protection during aortic cross clamping: retrograde venous spinal cord perfusion,distal aortic perfusion,and cerebrospinal fluid drainage

OBJECTIVE: We investigated retrograde venous spinal cord perfusion (RVP), with the established adjuncts cerebrospinal fluid drainage (CSFD), and distal aortic perfusion (DAP) in the canine model. We then examined the clinical feasibility of RVP, DAP, and CSFD. DESIGN: Canine study: Twenty dogs were randomized to four treatment groups. All animals underwent 60 min of complete aortic cross-clamp. Group 1 was the control and received only aortic cross-clamp; group 2 DAP and CSFD; group 3 DAP, CSFD, and RVP; and group 4 CSFD plus RVP. Human study: Five patients underwent aortic graft replacement of the descending or thoracoabdominal aorta, while receiving CSFD, DAP, and RVP. RESULTS: Canine study: All animals in groups 1 and 4 awoke paralyzed. One animal each in groups 2 and 3 were paraparetic, with the remaining dogs neurologically intact. Groups 2 and 3 differed from groups 1 and 4 at p < 0.0001. Human study: No mortality or permanent complications were observed in this group. CONCLUSION: While RVP did not reduce neurologic injury, neither did it increase morbidity. In humans the method is technically feasible and free from major problems. Further animal studies and randomized trials are underway at our center.     

Iloprost protects the spinal cord during aortic cross-clamping in a canine model

BACKGROUND: Surgical procedures on the thoracoabdominal part of the aorta make the spinal cord vulnerable to ischemia. Paraplegia is the most severe complication following thoracoabdominal operations. In this study, iloprost was used as an agent to decrease the severity of ischemia and reperfusion injury to the spinal cord during aortic occlusion and declamping. METHODS: Twelve adult mongrel dogs weighing 17+/-2 kg were used in this study. The animals were randomly assigned to either group I, which received saline solution (6 dogs), or group II, which received prostacyclin. Group I was referred to as the control group and group II as the iloprost group. After baseline measurements were completed, the aorta was cross-clamped for sixty minutes distal to the left subclavian artery. No pharmacologic agents were used to control blood pressure in group I. Proximal and distal mean arterial pressures (DMAP) were monitored continuously. DMAP were considered as diastolic pressure in preocclusion and reperfusion periods. Iloprost administration was started at a rate of 5 ng/kg/minute five minutes before the aortic occlusion. This dosage was increased to 25 ng/kg/minute during aortic occlusion. RESULTS: Mean proximal arterial pressure was 147+/-12 mmHg in the control group and 116+/-13 mmHg in the iloprost group at occlusion (p<0.01). Mean distal arterial pressure was 19+/-7 in the control group and 37+/-5 in the iloprost group during clamping (p<0.05). Functional outcome was evaluated according to Tarlov scores 24 hours after the study. Although none of the animals recovered completely from the control group, 4 animals from the iloprost group recovered (p<0.05). Following the neurologic assessment, animals were sacrificed and specimens were taken for the electron microscopic study. Electron microscopic changes documented that severe mitochondrial damage and vacuolisation occurred in the control group. However these changes were more subtle in the iloprost group. CONCLUSIONS: As a result of this study we concluded that iloprost infused before and during clamping of the thoracic aorta mitigates the spinal cord injury due to ischemia and reperfusion following unclamping.     

Effect of sodium nitroprusside on spinal cord perfusion and paraplegia during aortic cross-clamping

To evaluate the effects of sodium nitroprusside (SNP) on hemodynamics, cerebrospinal fluid dynamics, and neurological outcome after 30 minutes of thoracic aortic occlusion, we monitored proximal and distal blood pressure, cerebrospinal fluid pressure, spinal cord blood flow, and somatosensory evoked potentials. In group 1 (n = 6), no attempts were made to control proximal hypertension, whereas in group 2 (n = 6), proximal blood pressure was controlled with intravenous infusion of SNP. There was no significant difference in proximal or distal blood pressure or cerebrospinal fluid pressure between the two groups at baseline. During the crossclamp interval, the mean proximal aortic pressure rose from 108 +/- 21 to 146 +/- 14 mm Hg (p less than 0.001) in the control group, whereas the mean blood pressure in the SNP group was maintained at 99.8 +/- 12 mm Hg (p = not significant compared with baseline blood pressure). Mean distal aortic pressure decreased from systemic values to 23 +/- 7 mm Hg in control animals and to 11 +/- 5 mm Hg in the SNP group (p less than 0.005). In the latter group, cerebrospinal fluid pressure increased significantly from 10.6 +/- 1.9 to 20.1 +/- 5.5 mm Hg (p less than 0.005). In animals receiving SNP, spinal cord blood flow was decreased in the lower spinal cord segments and increased in the upper cord segments. When compared with controls, this difference did not reach significance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebrospinal fluid drainage and deep systemic hypothermia with total absence of circulation for spinal cord protection during surgery on the thoracic aorta

A 53-yearold man with a dissecting aneurysm of Stanford's type-B or Crawford's type I measuring 8.5 cm in diameter underwent replacement of the distal descending aorta and the thoracic aorta using techniques for spinal cord protection involving deep hypothermia at 17 degrees C and lasting 38 minutes with total absence of circulation. A subarachnoid catheter was inserted at the lumbar level to monitor spinal fluid pressure as well as to provide drainage if pressure exceeded 10 mm Hg. During surgery 60 ml was drained, followed by 95 ml after surgery on the same day and 325, 262 and 169 ml on the following three days.No signs of neurological deficit were observed during the postoperative period. Clinical course was good until hypovolemic shock developed 27 days after the operation due to upper digestive tract bleeding caused by two duodenal ulcers that perforated the gastroduodenal artery. Emergency antrectomy and vagotomy were performed. The patient died from multiple organ failure.Spinal cord injury continues to be one of the most feared complications after excision of thoracic and thoracoabdominal aorta aneurysm. Currently, various ways of protecting the spinal cord are practiced, including drainage of cerebrospinal fluid, partial bypass of the femoral artery, intercostal artery reimplantation, drug therapy and local spinal and/or systemic hypothermia. These methods, together with shorter clamping time have achieved a reduction in the incidence of spinal cord injuries.     

Cerebrospinal fluid drainage in the treatment of spontaneous spinal cord ischemia: a case report.

A patient with spontaneous acute spinal cord ischemia successfully treated with cerebrospinal fluid drainage is reported. There are no consensus guidelines on the management of spinal cord ischemia. Various preventive and rehabilitative measures have been suggested, but the best treatment remains unknown.     

Microdialysis of the spinal cord during thoracic aortic cross-clamping in a porcine model

OBJECTIVE: Utilising microdialysis to measure the changes of glucose, lactate, pyruvate and glutamate levels in the spinal cord after cross-clamping of the thoracic aorta in an established porcine model to monitor the degree of ischaemia. DESIGN: Experimental study with a porcine model. SETTING: University Hospital, Trondheim. SUBJECTS: Six pigs. MAIN OUTCOME MEASURE: Lactate, pyruvate and glutamate concentrations in the microdialysis perfusate from the spinal cord. RESULTS: A significant increase of the lactate-pyruvate ratio during the last 30 min of the 1 h clamping period, with a maximum increase of 169% from the basal value the last 10 min before declamping. No evident change in this ratio between the clamping and the reperfusion period. No significant change in glutamate levels during clamping or reperfusion period. CONCLUSION: Microdialysis reflects the ischaemic state of the spinal cord during cross-clamping of the thoracic aorta in pigs, and is well suited to study each phenomena.     

Strategy for spinal cord protection during thoracoabdominal aortic surgery

INTRODUCTION: Our basic strategy for spinal cord protection during thoracoabdominal aortic surgery has been established since August 1994 such as: 1) distal aortic perfusion using partial cardiopulmonary bypass (32-34 degrees C), 2) multi-segmental sequential clamping, 3) deep hypothermic circulatory arrest when sequential clamping is impossible, 4) evoked spinal cord potential-guided reconstruction of the critical intercostal arteries (preoperative evaluation using multi-detector row computed tomography), 5) cerebrospinal fluid drainage, and 6) administration of naloxone hydrochloride and methylprednisolone. In this paper, we analyzed clinical outcome of thoracoabdominal aortic surgery according to this strategy. MATERIALS AND METHODS: We have performed thoracoabdominal aortic surgery for 84 patients (52 male, mean 62 +/- 12 years old) during 1991-2003. Their etiology was 34 dissection, 44 non-dissection degenerative disease, 3 pseudo-aneurysm, and 3 infection. Ten operations were performed urgently and 8 emergently. Crawford's classification (type I/II/III/IV/V) was 17/28/17/13/9 for each type. We used partial cardiopulmonary bypass for 67 cases and deep hypothermic circulatory arrest for 14. RESULTS: For overall/elective cases (n = 84/66), we experienced 13.1/12.1% of incidence of spinal cord injury (paraplegia/paraparesis) and 8.3/4.5% of in-hospital mortality. Within 65 cases (55 elective) operated after August 1994, they decreased up to 7.7/5.5% (0% in type II) and 4.6/1.8%, respectively. Paraplegia was experienced in 2 patients before and 2 patients (emergent operations due to infective aneurysm) after August 1994 (4.8%). Thus, we have experienced no paraplegia in elective cases after establishment of our strategy. CONCLUSIONS: Our strategy for spinal cord protection during thoracoabdominal aortic surgery could provide acceptable clinical outcome and seemed justified.     

Relationship of spinal cord blood flow to vascular anatomy during thoracic aortic cross-clamping and shunting

No satisfactory explanation exists as to why paraplegia occurs despite distal aortic perfusion during thoracic aortic operations. We studied the hemodynamics, paraplegia rate, and spinal cord blood flow with radioactive microspheres in 17 male adult baboons, with particular reference to the arteria radicularis magna. The groups consisted of control animals, subjected to cross-clamping for 60 minutes, and animals with aorto-aortic shunts operational for 60 minutes. There were no significant left ventricular hemodynamic advantages with shunting. Shunting significantly increased lumbar spinal cord blood flow (p = 0.0009), which correlated with the distal aortic mean pressure (r = 0.59, p = 0.008). However, lower thoracic spinal cord blood flow did not increase during shunting (p = 0.2) and did not correlate with the distal aortic pressure (r = 0.11, p = 0.64). This is due to the vascular anatomy of the anterior spinal artery, which was, as in man, smaller above (0.278 mm) than below (0.744 mm) the entry of the arteria radicularis magna. Resistance to flow, as calculated by Poiseuille's equation, was 51.7 times greater up the anterior spinal artery as compared with down this artery. The vascular anatomy explains the absence of paraplegia in one baboon in the cross-clamp group and paraplegia in one baboon in the shunt group. Thus, distal aortic perfusion protects the spinal cord below the arteria radicularis magna but not above it.     

Cerebrospinal fluid drainage complications during first stage and completion fenestrated-branched endovascular aortic repair

ObjectiveTo determine the rates and risk factors of complications related to cerebrospinal fluid drainage (CSFD) during first stage and completion fenestrated-branched endovascular aortic repair (F-BEVAR) of pararenal and thoracoabdominal aortic aneurysms.MethodsWe reviewed the outcomes of 293 consecutive patients enrolled in a prospective, nonrandomized study to investigate outcomes of F-BEVAR between 2013 and 2018. Patients who received CSFD during first-stage thoracic endovascular aortic repair, index F-BEVAR, or completion of temporary aneurysm sac perfusion procedures were included in the analysis. CSFD complications were graded as severe or moderate if they were life threatening, escalated the level of care, or prolonged the hospital stay. Presence of substantial degenerative lumbar disease (DLD) was identified based on review of preoperative computed tomography. End points included technical difficulties during CSFD placement and CSFD-related complications.ResultsA total of 187 patients (mean age, 73 ± 8 years; 70% male) treated for 20 pararenal and 167 thoracoabdominal aortic aneurysms received CSFD in 240 procedures, including 51 first-stage thoracic endovascular aortic repairs, 184 index F-BEVARs, and 5 completion temporary aneurysm sac perfusion procedures. Nineteen patients (10%) had 22 CSFD-related complications after 21 aortic procedures (9%). Complications were graded as severe to moderate in 17 patients (9%). There were 12 patients (6%) with intracranial hypotension, including three (2%) who had intracranial hemorrhage and nine (5%) with post dural puncture headache requiring blood patches in six. Another six patients (3%) developed spinal hematomas resulting in paraplegia in two (1%) and transient paraparesis in two (1%). One patient had CSF leakage from the puncture site (no intervention required). Four patients had bleeding during attempted drain placement, which required postponement of F-BEVAR. Technical difficulties were experienced in 57 drain insertions (24%), more often in patients with DLD than in those without DLD (35/113 [31%] vs 22/121 [18%]; P = .03). Fluoroscopic guidance was used in 44 drain placements (18%) with a lower rate of technical difficulties compared with the blind approach (9% vs 28%; P = .01). There was a statistically nonsignificant trend toward more complications in patients with technical challenges (14% vs 7%; P = .10). Of 13 study patients who developed spinal cord injuries during aortic procedures, 4 (31%) were attributed to CSFD.ConclusionsAlthough CSFD is widely used to prevent ischemic spinal cord injury during complex aortic repair, the risk of major CSFD-related complications is not negligible and should be carefully weighed against its potential benefits. One-third of spinal cord injuries were caused by CSF drain placement. The use of fluoroscopic guidance may decrease the risk of CSFD-related complications.     

The mechanism of spinal cord injury after simple and double aortic cross-clamping

Ischemic spinal cord injury after cross-clamping of the descending aorta can occur independently of aortic disease. In a previous study we had shown a precipitous uniform fall of spinal surface oxygen tension downstream to the clamping site irrespective of level. In the present paper, the hemodynamic changes in the spinal and aortic collateral circulation were investigated. Pressures were measured in the proximal, distal, and excluded aortic segments (descending thoracic and lumbar aorta) as well as in the intercostal and the lumbar arterial beds. Before high aortic occlusion, pressures in the intercostal and lumbar arterial beds were lower than aortic pressure. Along with the postclamping fall in distal arterial pressure, intercostal and lumbar arterial bed pressure decreased further but remained above aortic pressure. Exclusion of the thoracic aorta by double clamping restored intercostal bed pressure almost to control, whereas exclusion of the abdominal aorta hardly affected lumbar bed pressure. We conclude that spinal collateral circulation is more highly developed in the thoracic than in the lumbar region. After aortic cross-clamping, blood tends to drain away from the spinal cord rather than supplying it longitudinally. Under clinical conditions, therefore, retrograde bleeding into the opened aorta as well as into the aorta downstream to the distal clamp should be minimized and larger vessels originating from the aorta should promptly be anastomosed to the graft.     

Current strategies of spinal cord protection during thoracoabdominal aortic surgery

Despite improved survival rates after thoracoabdominal aortic aneurysm repairs, paraplegia remains a devastating complication with high incidence, ranging from 3 to 10%. Ischemic insults to the spinal cord are unavoidable during thoracoabdominal aortic aneurysm repairs. There is no single measure that can prevent paraplegia alone. A multimodality approach is required to minimize the ischemic insults during thoracoabdominal aortic aneurysm repairs and postoperative second hit to the spinal cord. Distal aortic perfusion is important to maintain the collateral network perfusion pressure, while cerebrospinal drainage allows to directly maintain the spinal cord perfusion. Reattachment of segmental arteries T8–T12 is encouraged to lower the incidence of both immediate and delayed paraplegia. Systemic arterial pressure should be maintained above 130 mmHg and cerebrospinal drainage should be continued until the second postoperative day, despite intact neurological status. In this article, we describe our current operative techniques and perioperative management in patients undergoing repairs of thoracoabdominal aortic aneurysm. A review of recent updates on spinal protection strategies is also reported.     

Winner of the ESVS prize 1989. Microcirculation of the spinal cord during proximal aortic cross-clamping

The relationship between the cerebrospinal fluid pressure (CSFP) and the microcirculation of the spinal cord was studied during cross-clamping (XC) of the thoracic aorta in pigs. CSFP was recorded via an intrathecal catheter. The microcirculation was measured by the laser Doppler technique using a needle probe inserted percutaneously into the spinal cord. A left thoracotomy was performed, and the thoracic aorta was cross-clamped for 30 minutes distal to the left subclavian artery. Prior to XC a pulsatile flux recording from the spinal cord (SCF) was observed. Following cross-clamping of the aorta SCF was dramatically reduced (P less than 0.001), then stabilised at 40% of base-line values. During XC, variations in CSFP were observed but these changes were not statistically significant. CSFP gradually increased to pre cross-clamp levels following release of XC (P less than 0.05). SCF increased 51% following removal of 1 ml of cerebrospinal fluid (P less than 0.05). By injection of 0.9% saline at body temperature SCF was totally inhibited at CSFP above 15 mmHg. Occlusion of the azygos vein increased CSFP 1.3 mmHg (P less than 0.05) whereby SCF decreased 58% (P less than 0.01). Following release of XC of a hyperaemic period of the SCF was demonstrated in ten out of 13 animals. In conclusion, SCF was significantly influenced by changes in CSFP during XC of the thoracic aorta. The findings support the theory that removal of spinal fluid during XC of the thoracic aorta may increase the perfusion pressure to the spinal cord, thereby improving its blood supply.