Spinal Cord Blood Supply Research Articles

Development of spinal cord ischemia after clamping of noncritical segmental arteries in the pig

Background. Blood flow to the thoracolumbar spinal cord is thought to be critically dependent on the arteria radicularis magna. We investigated whether spinal cord blood supply becomes dependent on other, noncritical, segmental arteries if spinal cord perfusion pressure (SCPP) is decreased. The SCPP is equal to the mean arterial pressure (MAP) minus the cerebrospinal fluid (CSF) pressure (SCCP = MAP − CSF). Methods. The thoracoabdominal aorta was exposed in 10 pigs. Functional integrity of spinal cord motor pathways was assessed with myogenic motor-evoked potentials after transcranial electrical stimulation (tc-MEPs). Using this technique, a group of segmental arteries not critical for spinal cord blood supply was identified. Before, during, and after clamping of the noncritical segmental arteries, spinal cord ischemia was produced by decreasing SCPP by means of increasing CSF pressure, and the SCPP threshold at which tc-MEPs showed evidence of spinal cord ischemia was determined. Ischemic SCPP thresholds, obtained during and after clamping of the noncritical segmental arteries, were compared with the ischemic threshold obtained before clamping (control value). Results. Before noncritical segmental arteries were clamped, ischemic tc-MEP changes occurred when the SCPP was below 15 ± 5 (SD) mm Hg. With a total of 9 ± 3 (SD) segmental arteries clamped, the ischemic SCPP threshold was 48 ± 14 mm Hg ( p < 0.01). After the release of all clamps, ischemia occurred at a SCPP of 15 ± 5 (SD) mm Hg. Conclusions. In this porcine experiment, clamping of originally noncritical segmental arteries significantly reduced the tolerance of the spinal cord to a decrease in SCPP.

Spinal cord ischemia after abdominal aortic operation: Is it preventable?

Purpose: Spinal cord ischemia after operation on the abdominal aorta is a rare event that is attributed to variations in the spinal cord blood supply. The purpose of this study was to evaluate the possible causes of this devastating event. Methods: A survey of patients among the members of the Southern Association for Vascular Surgery was performed, and 18 patients were identified with spinal cord ischemia manifested by paraplegia or paraparesis after abdominal aortic operation. Results: Preoperative computed tomographic, magnetic resonance, and aortographic results did not visualize the greater radicular artery (Adamkiewicz’s artery) in any patient. Eleven patients underwent resection of infrarenal abdominal aortic aneurysms (AAAs): seven of these patients had tube grafts, three had aortobifemoral grafts, and one had an aortobiiliac graft. Five other patients underwent placement of aortobifemoral grafts, and one patient underwent aortobiiliac graft placement for occlusive disease. One patient underwent suprarenal AAA resection with an interposition graft to a previous aortobiiliac graft. The mean operative time was 3 hours and 39 minutes (range, 2 hours and 45 minutes to 6 hours and 30 minutes), with a mean aortic cross-clamp time of 48 minutes (range, 24 to 97 minutes). Sixteen aortic cross-clamps were placed infrarenally and two suprarenally (one in a case of ruptured AAA, the other a suprarenal AAA). Seventeen proximal anastomoses were end to end. The average minimum systolic blood pressure during the aortic cross-clamping was 96 mm Hg (range, 80 to 130 mm Hg). All the patients had internal iliac artery flow preserved with either prograde perfusion (10 patients) or retrograde perfusion (eight patients), and one patient underwent unilateral internal iliac artery ligation because of aneurysmal disease. One aortobifemoral-graft limb necessitated thrombectomy, but no cases of massive peripheral embolization occurred. When paraplegia was suspected after operation (6 to 20 hours after surgery), five patients underwent lumbar drainage. No clinical improvement was noted. Conclusion: Interference with pelvic blood supply from prolonged aortic cross clamping, intraoperative hypotension, aortic embolization, and interruption of internal iliac artery circulation have all been suggested as possible causes of spinal cord ischemia. In this survey, none of these factors proved to be significant as the sole cause of spinal cord ischemia. In the performance of an aortic operation with an end-to-end proximal anastomosis in the presence of severe external or internal iliac artery disease, there may be an increased incidence of spinal cord ischemia despite appropriate surgical techniques to ensure internal iliac perfusion. Spinal cord ischemia after abdominal aortic operations appears to be a tragically unpredictable, random, and unpreventable event. (J Vasc Surg 1999;30:391-9.)

The Role of Spinal Angiography in Operations on the Thoracic Aorta: Myth or Reality?

Background. The importance of preserving the artery of Adamkiewicz during replacement of the thoracoabdominal aorta is debated. We report our experience with the use of preoperative spinal angiography and modification of the surgical technique. Methods. Between September 1993 and March 1996, 46 patients (mean age, 57 years; range, 25 to 73 years) underwent spinal angiography at our institution, 23 for an aneurysm and 23 for chronic dissection. Localization of the artery of Adamkiewicz between T-9 and L-3 was successful in 30 (65%) patients: T-9, left = 2, right = 1; T-10, left = 4; T-11, left = 10, right = 2; T-12, left = 3, right = 1; L-1, left = 1, right = 2; L-2, left = 2, right = 1; and L-3, left = 1. Thirty-one patients subsequently underwent replacement of the descending thoracic aorta and 13 underwent replacement of the thoracoabdominal aorta. Left atrial-femoral artery bypass was used in 23 patients and full extracorporeal circulation was used in 20 patients. Twelve procedures included the reimplantation of crucial intercostal/lumbar branches. Results. The operative mortality rate was 6.8% (3 of 44 patients) and 1 (2.27%) patient had paraparesis. In addition to the 12 patients who underwent targeted reimplantation of the intercostal branches, evaluation of the spinal cord blood supply influenced the operative technique in 19 other patients. Conclusions. Selective angiography can demonstrate the spinal cord blood supply even in patients with complex aortic pathology. It is a helpful tool for planning extensive replacement of the thoracic and thoracoabdominal aorta.

Intraoperative adjuncts of spinal cord protection.

Immediate neurological deficits as a complication of aortic surgery occur as the direct result of hypoxia, related to the acute deprivation of spinal cord blood supply inflicted by prolonged aortic cross-clamping (AXC). The etiology of spinal cord ischemia constitutes a series of progressive interdependent events which include proximal hypertension, increase in cerebrospinal fluid pressure, perioperative hypotension, inadequate perfusion to critical intercostal or lumbar vessels, extent of aortic pathology and duration of AXC. Several intraoperative interventions and strategies, which address the multifactorial nature of cord injury, are presented by the authors. Of critical importance is the role of adequate distal aortic perfusion, with either left atrium-femoral artery (LA-FA) bypass or arterial-arterial passive shunts, to control both central hypertension, through proximal unloading, and hypotension distal to AXC. Equally crucial is the increase in CSF pressure, secondary to proximal hypertension, which acts antagonistically to distal aortic pressure in regulating spinal cord perfusion pressure (SCPP). Cerebrospinal fluid drainage (CSFD) reduces CSF pressure to offset SCPP to favor cord perfusion. Pharmacological agents, such as papaverine and steroids in combination with CSFD, produce a synergistic benefit of extending the time interval of safe AXC. Encouraging results have also been realized with circulatory arrest and profound hypothermia which reduce oxygen demand of neural tissues and extend the safe duration of AXC interval. The use of distal bypass is most effective with CSFD as an integral component of a multimodality approach, which also incorporates the intraoperative monitoring of somatosensory evoked potentials (SSEP), to detect the onset of spinal cord ischemia and assess the adequacy of distal aortic perfusion and disposition of critical segmental vessels.

Spinal cord monitoring with myogenic motor evoked potentials: early detection of spinal cord ischemia as an integral part of spinal cord protective strategies during thoracoabdominal aneurysm surgery.

Spinal cord ischemia during resection of thoracoabdominal aortic aneurysms (TAA) can result in lower limb neurological deficits. Spinal cord monitoring can only improve outcome if ischemia is detected before irreversible damage has occurred and protective measures are readily available. Monitorin( spinal cord function with motor evoked potentials (MEPs) is a relatively new technique. With MEP. recorded from the muscle (myogenic MEPs), the vulnerable spinal motoneuronal system is exclusively monitored and ischemia is detected within minutes. Using a strategy aimed at maintaining and restoring spinal cord blood supply (distal aortic perfusion, sequential aortic clamping, and selective segmental artery reattachment), early detection of ischemia allows protective measures to be applied and adjusted immediately, ie, reattaching or safely ligating intercostal arteries, increasing proximal o distal aortic pressures as required, or inducing hypothermia. Recent improvements in the technique fo eliciting myogenic MEPs include multi-pulse stimulation paradigms and the use of a circumferentia cathode. This results in robust and reproducible signals, which are less susceptible to anesthetic interference and allow the use of a constant level of neuromuscular blockade. In conclusion, monitoring myogenic MEPs during a TAA repair has become clinically feasible. The fast detection of spinal cord ischemia allows timely guidance of protective measures.

Surgical Education: Scientific Dialogue++Experimental Use of Somatosensory Evoked Potential for Intraoperative Identification of Spinal Cord Blood Supply

The role of sensory evoked potentials (SEPs) to be used intraoperatively to reliably predict spinal cord ischemia, caused by interruption of intercostal and of lumbar and sacral arteries, was evaluated in a canine model. Two groups were assessed: (A) interruption of intercostal arteries (n = 6) and (B) interruption of all posterior branches (n = 6). SEPs were evaluated intraoperatively as control and interruption of posterior vessel groups, and at 18-22 h after surgery. Neurologic assessment was performed preoperatively and 18-22 h postoperatively by modified Tarlov criteria. Morphological assessments were also performed. The assessment of the groups demonstrated prolongation of latency and loss of amplitude of SEP, but individual changes of SEPs were poor predictors of paraplegia. Ultrastructural changes correlated with neurologic findings. SEPs were unreliable for intraoperative identification of vessels critical to spinal cord blood supply, possibly related to anatomically different blood supply of sensory and motor tracts.

Intraoperative identification of spinal cord blood supply during repairs of descending aorta and thoracoabdominal aorta

Objective: The aim was to intraoperatively identify the spinal cord blood supply and shorten the aortic crossclamp time. Methods: A platinum electrode was placed intrathecally by lumbar puncture alongside the spinal cord. After the aorta was crossclamped, hydrogen in a saline solution was injected into the aorta and, if it was shown that the segment supplied the spinal cord and there were multiple arteries, then these were individually injected. The repair was performed by a sequential segmental method as described previously. Results: Postoperatively, highly selective angiography was used to confirm that reattached intercostal arteries supplied the spinal cord. The technique was accurrate in all patients. Five spinal cord perfusion patterns were noted: (1) direct, (2) collateral, (3) no direct supply from segment tested, (4) from atriofemoral bypass, and (5) occluded reattached intercostals. When no response was obtained or no further testing was required ( n = 8), testing time was 4.2 minutes and crossclamp time 41.9 minutes. When multiple segmental arteries required further testing, the mean testing time was 10.4 minutes and crossclamp time 58.5 minutes, including reattachment of intercostal vessels ( p = not significant). Conclusion: Preliminary findings indicate that this method is a safe research technique, can detect radicular arteries, and may reduce the time for aortic crossclamping if no vessels are identified as supplying the spinal cord. (J T horac C ardiovasc S urg 1996;112:1455-61)

Surgery for acquired heart disease looking for the artery of adamkiewicz: A quest to minimize paraplegia after operations for aneurysms of the descending thoracic and thoracoabdominal aorta

All patients undergoing resection of thoracic or thoracoabdominal aneurysms at Mount Sinai Hospital since November 1993 had spinal cord function monitored with somatosensory-evoked potentials as part of a multimodality approach to reducing spinal cord injury. In the segment to be resected, each pair of intersegmental vessels was sequentially clamped, and they were subsequently sacrificed only if no change in somatosensory evoked potentials occurred within 8 to 10 minutes after occlusion. Adjunctive protective measures included mild hypothermia (31° to 33° C), distal perfusion, corticosteroids, maintenance of high normal blood pressures, avoidance of nitroprusside, and cerebrospinal fluid drainage. Ninety-five consecutive patients operated on since 1993 (group II) were compared with 138 earlier patients (group I). Preoperative characteristics such as age, sex, etiology of aneurysm, emergency operation, and reoperation did not differ between groups, nor did operative variables such as incidence of rupture and extent of resection. Group I had slightly more smokers and slightly fewer hypertensive individuals. Group II patients had a significantly better outcome with respect to in-hospital mortality (10.5% vs 18%, p = 0.045) and paraplegia (2% vs 8%, p = 0.008). By multivariate analysis, rupture and diabetes were associated with significantly higher in-hospital mortality, and smoking greatly increased the incidence of paraplegia. The extent of the aneurysm was a major determinant of mortality and paraplegia. The low paraplegia rate in group II was achieved without reattachment of a single intercostal or lumbar artery. No patient with fewer than 10 intersegmental arteries severed had paraplegia, and spinal cord ischemia was reversible in three patients after adjunctive maneuvers were performed to improve perfusion, suggesting that spinal cord blood supply is unlikely to depend on a single “artery of Adamkiewicz.” (J T HORAC C ARDIOVASC S URG 1996;112:1202-15)

Enoximone usage for experimental spinal cord protection during aortic cross-clamping.

Spinal cord preservation during aortic cross-clamping is of vital importance. Maintenance of spinal cord blood supply is one of the key points for spinal cord preservation. In this study enoximone was selected as an agent to reduce the risk of spinal cord injury because of its inotropic and vasodilator actions. Ten dogs underwent sixty minutes aortic occlusion. Five animals received enoximone and the others did not (the control group). Enoximone dosage was 10 microgram/kg/min. Four dogs in the control group suffered paraplegia. There were no paraplegic events in the enoximone group. Cerebrospinal fluid pressure was 17 +/- 3 mmHg in the control group, 15 +/- 4 mmHg in the enoxirmone group. Distal aortic pressure was 15 +/- 4 mmHg in the control group, 47 +/- 6 in the enoximone group (p < 0.001). In this study we conclude that enoximone is an effective agent to reduce the risk of spinal cord injury.

High resolution magnetic resonance imaging of the rat spinal cord.

A two turn saddle shaped surface coil receiver was developed that allowed high resolution magnetic resonance imaging of the rat spinal cord. This is particularly important in laboratory animals where central nervous system regions of interest are relatively small. A continuous copper wire 1.5 mm in diameter was wound into two turns 28 mm in diameter. The saddle shape of the second turn improved the homogeneity of the signal within the region of interest and maintained sufficient field of view and depth of penetration. The quality factor (Q) for the surface coil was Q = 199 unloaded, and Q = 60 loaded. Using this surface coil with a GE CSI II 2.0 Tesla small bore magnet, spin echo T1 (TR = 500 msec, TE = 25 msec) and T2 (TR = 2000 msec, TE = 100 msec) weighted images were obtained in cross section, using 2 mm slice thickness with 2 excitations per phase encoding step. A sagittal gradient echo (rapid scan, TR = 85 msec, TE = 10 msec) was used to document reestablishment of vascular flow following ischemia. Spinal cord ischemia was induced by 14 minute temporary occlusion of spinal cord blood supply. MRI was performed at 18 hours following ischemia. There was a 1.4 fold increase in T2 image intensity in ischemic rat spinal cord (n = 4), consistent with edema formation, compared to normal rat spinal cord (n = 4). Preliminary studies show that similar high resolution images can be performed on the rat brain. This technique uses standard MRI equipment and the surface coil is made from inexpensive readily available materials. There are various animal models of cerebral and spinal cord injury that would benefit from improved high resolution MRI. This coil design may have application in larger animal models and the clinical setting.

Epinephrine Should Not Be Part of an Epidural Test Dose

President Del Oro Anesthesiologists, P.A., P.O. Box 20553 Houston, Texas 77225–0553.To the Editor:--Fitzgibbons et al. correctly pointed out that there is high incidence of paraplegia after thoracic aneurysmectomy. [1]They also noted that tenuous collateral anastomosis of the anterior spinal artery is compromised during and after thoracic aneurysmectomy. Therefore, it is logical to conclude that any technique that increases the epidural and intrathecal pressure is likely to decrease the spinal cord blood supply. In addition, use of epinephrine (intrathecal or intraepidural) is likely to aggravate the situation by causing vasoconstriction. Therefore, I believe the choice of epidural route for pain relief in such a patient is most likely contraindicated.Development of pain service units in the hospitals is a valuable service for the care of patients. Overzealous and aggressive use of these techniques is producing unwelcome results in various parts of the country. I believe it is imperative that all anesthesiologists report serious complications, so that we can have a better understanding of the causes of such disastrous events. A voluntary and confidential data bank should be established so that these cases could be reported and analyzed by a group of anesthesiologists who are actively involved in promoting the regional anesthesia techniques.Biman B. Das, M.B.B.S. (Calcutta), F.R.C.A. (London), President Del Oro Anesthesiologists, P.A., P.O. Box 20553, Houston, Texas 77225–0553.

The risk of ischemic spinal cord injury in patients undergoing graft replacement for thoracoabdominal aortic aneurysms.

We developed a monitoring system to detect spinal cord ischemia during aortic cross-clamping (AXC). This system was used to prospectively determine in which patients ischemia occurs, in which patients reimplantation of intercostal arteries is unnecessary or mandatory, and when reperfusion of intercostal arteries (ICAs) is urgent. Two hundred sixty patients underwent thoracoabdominal aortic aneurysm (TAA) repair with simple AXC. In 167 patients, two electrocatheters were placed before the onset of anaesthesia at level L1/L2 (stimulation) and level T5/T6 (recording) within the epidural space. During surgery, spinal cord function was monitored by recording spinal somatosensory evoked potentials (sSSEP). According to the extent of aortic replacement, most patients were expected to have a high risk of paraplegia. In group A (59 patients), sSSEP remained normal throughout surgery, and in 54 of these patients ICAs were not reattached outside the proximal aortic anastomosis. In the other five patients ICAs were reimplanted separately because of possible anatomic relation to spinal cord blood supply. No patient in group A had postoperative neurologic deficit. In group B (54 patients) sSSEP remained normal until 15 minutes after AXC but were impaired thereafter. Nineteen patients had early reimplantation of ICAs. Of the 19, three had paraparesis and two had paraplegia. Neurologic deficit developed in the patients without early reimplantation of ICAs. In four patients separate reimplantation of ICAs was performed late in the procedure because of incomplete sSSEP recovery. Subsequently, the sSSEP returned to normal and only one of the four patients had mild paraparesis. The total rate of neurologic deficits in this group was 13% (paraplegia, 3.5%; paraparesis, 9.5%). All 54 patients in group C showed rapid loss of sSSEP within 15 minutes of AXC. In 28 patients ICAs were reimplanted only within the proximal anastomosis. Twenty-one of these patients showed prompt signal recovery after blood-flow release into the reimplanted ICAs, and none had neurologic deficit. Seven patients had no or very late and incomplete sSSEP recovery. Of the seven, three had paraplegia and four had paraparesis. In 26 patients ICAs were reimplanted separately to the proximal anastomosis. This was done early during the procedure in 17 patients, of whom 13 had full recovery of sSSEP and normal neurologic status. Four patients had incomplete or no recurrence of sSSEP, followed by paraplegia in one and paraparesis in three. In nine patients ICAs were reimplanted after the aortic replacement had been completed because of sSSEP recovery was not satisfactory. In all patients in this subgroup sSSEP returned to normal. Six patients had a normal neurologic status and three had mild paraparesis. The total neurologic complication rate in group C was 26% (paraplegia, 7.5%; paraparesis, 18.5%). The risk of ischemic spinal cord injury during replacement for TAA can be assessed continuously by monitoring the sSSEP directly from the spinal cord. Patients without sSSEP changes during aortic reconstruction do not require ICA reattachment and will not have neurologic deficit. Patients who lose sSSEP after AXC are at risk for paraplegia. Patients with impairment or loss of sSSEP >15 minutes after AXC have some collateral vessels, and must have ICAs reimplanted only if sSSEP do not return within normal recovery time after blood-flow release into the proximal anastomosis. Loss of sSSEP within 15 minutes of AXC shows poor collateralization and mandates early restoration of spinal cord blood supply. If the surgeon can achieve the return of sSSEP to normal by subsequent separate reimplantation of ICAS, paraplegia will not occur and paraparesis will be rare and mild. Spinal cord monitoring is a valuable guide to detect whether the spinal cord is at risk and to take measures against par

The effect of radicular arteries ligation on the spinal cord blood supply in cats.

In order to study the contribution of the radicular arteries to the blood supply of the spinal cord, we performed experimental occlusion of these arteries in cats. In 43 cats, under thiopental anaesthesia, unilateral, bilateral, single or multiple ligations of dorsal radicular arteries were carried out. The animals were killed at the 1st, 2nd and 7th postoperative day. The spinal cords were removed and preserved in formalin solution for 1 month and then examined, using light microscopy. We conclude that bilateral or multiple ligations are capable of producing ischaemic lesions in the spinal cord, more profound by the seventh postoperative day, while single ligations do not produce such lesions, unless a medullary artery is involved. The ischaemic lesions which were observed were associated with clinical neurological deficits.

Regional adenosine attenuates postischemic spinal cord injury

Purpose: Operations on the thoracic and thoracoabdominal aorta are associated with postoperative paraplegia rates as high as 20% to 30%. Attempts to reduce this complication have focused on decreasing the energy needs of the spinal cord with protective agents such as hypothermia and barbiturates or on increasing blood flow with various shunts. This study explores the hypothesis that perfusion of the spinal cord with hypothermic solutions or with adenosine will prevent or ameliorate paraplegia.Methods: New Zealand white rabbits underwent 40 minutes of infrarenal aortic isolation. The infrarenal aorta is the primary source of spinal cord blood supply in the New Zealand white rabbit. Control rabbits sustained aortic occlusion without any protective measures. The remaining animals were randomized into three groups that underwent aortic cross-clamping with various protective adjuncts. Group I received regional aortic hypothermia perfusion, group II received systemic adenosine, and group III received regional aortic perfusion with high-dose adenosine.Results: Neurologic function was graded according to the Tarlov scale (0 = no movement, 1 = slight movement, 2 = sits with assistance, 3 = sits alone, 4 = weak hop, 5 = normal hop). After 96 hours animals were euthanized, and spinal cords were harvested for histologic examination. The nonparaplegic animals in group I had a mean Tarlov score of 1.5, whereas those in group III had a mean score of 3.4. Histologic studies on spinal cord tissue revealed no significant differences between the study groups.Conclusions: These data demonstrate that administration of regional adenosine attenuates ischemic injury associated with aortic occlusion in this experimental model.

Influence of preservation or perfusion of intraoperatively identified spinal cord blood supply on spinal motor evoked potentials and paraplegia after aortic surgery

Permanent ligation of arteries supplying blood to the spinal cord in operations for aortic aneurysm can lead to spinal cord ischemia, which can result in either paraparesis or paraplegia. This report describes a rapid method of intraoperative identification of those arteries that supply the spinal cord by use of an intrathecal platinum electrode to detect hydrogen in solution that has been injected into the aortic ostia. Preservation or perfusion of those identified arteries supplying the spinal cord may decrease the rate of postoperative neurologic complications. Of 28 porcine experiments with postoperative observation for 24 hours, there were 3 initial pilot experiments in which saline saturated with hydrogen was injected into the temporarily cross-clamped aorta. Twenty animals were then randomized to (1) preservation of only the vessels sequentially identified to supply blood to the spinal cord from T-13 to L-5 (n = 10); (2) division of the vessels supplying the spinal cord (n = 10). A further five animals underwent perfusion experiments wherein the identified cord arteries were perfused by a shunt, the other nonsupply arteries were divided, and the aorta was kept clamped for 45 minutes. Spinal motor evoked potentials were elicited with an intrathecal electrode and were highly sensitive for paralysis. Paralysis occurred in 0/3 pilot (p less than 0.013 vs division); 8/10 division; 1/10 preservation (p less than 0.0017 vs division); and perfusion 1/5 (p less than 0.025 vs division). Results of a pilot study in eight humans shows that the technique can be used to rapidly identify segmental arteries supplying the spinal cord, to determine if distal perfusion is supplying the spinal cord with blood flow, and if reattached segmental arteries are patent.

Angiographic localization of spinal cord blood supply and its relationship to postoperative paraplegia

Forty-seven patients underwent selective catherization of middle and lower thoracic intercostal and upper lumbar arteries to define the origin of the artery of Adamkiewicz. One patient had significant atheroembolism, and a second had transient lower extremity paresthesias. No other complications occurred. The origin was found in 26 (55%), and 21 patients underwent thoracoabdominal aneurysm repair with this knowledge. When the critical lumbar or intercostal artery could be included as part of a long proximal or distal anastomosis, all 12 patients could be included as part of a long proximal or distal anastomosis, all 12 patients survived, and one was paralyzed. However, if the aneurysm repair mandated a midgraft anastomosis to intercostal arteries critical to spinal cord perfusion, seven of nine patients either died or were paralyzed (p < 0.05). In the group of 19 patients operated on in whom spinal cord blood supply was not identified three patients had a technically unsuccessful operation; two died, and one was paralyzed. Twelve of 16 patients who had an adequate, but unsuccessful attempt at localization were treated by intercostal “neglect” and survived. Late paresis developed in two patients, but they are walking now. One of the patients who died had multiple systems failure and awakened paraplegic. She had a patent, enlarged, thoracic radicular artery at T-5 which probably supplied to spinal cord and which was missed angiographically. Paralysis was associated with aneurysm extent (group 2 and III B, dissections vs group 1 & 3, p < 0.05). Selective intercostal angiography requires further refinement, but it is safe and offers the promise of understanding the mechanisms and risks of spinal cord complications after repair of extensive thoracoabdominal aneurysms.

Angiographic localization of spinal cord blood supply and its relationship to postoperative paraplegia

Forty-seven patients underwent selective catheterization of middle and lower thoracic intercostal and upper lumbar arteries to define the origin of the artery of Adamkiewicz. One patient had significant atheroembolism, and a second had transient lower extremity paresthesias. No other complications occurred. The origin was found in 26 (55%), and 21 patients underwent thoracoabdominal aneurysm repair with this knowledge. When the critical lumbar or intercostal artery could be included as part of a long proximal or distal anastomosis, all 12 patients could be included as part of a long proximal or distal anastomosis, all 12 patients survived, and one was paralyzed. However, if the aneurysm repair mandated a midgraft anastomosis to intercostal arteries critical to spinal cord perfusion, seven of nine patients either died or were paralyzed (p less than 0.05). In the group of 19 patients operated on in whom spinal cord blood supply was not identified three patients had a technically unsuccessful operation; two died, and one was paralyzed. Twelve of 16 patients who had an adequate, but unsuccessful attempt at localization were treated by intercostal "neglect" and survived. Late paresis developed in two patients, but they are walking now. One of the patients who died had multiple systems failure and awakened paraplegic. She had a patent, enlarged, thoracic radicular artery at T-5 which probably supplied to spinal cord and which was missed angiographically. Paralysis was associated with aneurysm extent (group 2 and III B, dissections vs group 1 & 3, p less than 0.05). Selective intercostal angiography requires further refinement, but it is safe and offers the promise of understanding the mechanisms and risks of spinal cord complications after repair of extensive thoracoabdominal aneurysms.

Functional Anatomy of the Spinal Cord and Related Structures

This article reviews the anatomy of the vertebral canal and its contents from a surgical perspective. The normal and pathological relationships of intradural structures are addressed. Spinal cord blood supply, metabolism, and ischemia are discussed in detail. A clinically oriented biomechanical analysis of forces acting within the spinal canal under both physiological and pathological conditions is also presented.

Preliminary report of localization of spinal cord blood supply by hydrogen during aortic operations

One source of paraplegia after aortic operations is the failure to reattach the spinal cord blood supply, the origins of which are not evident at operation. This report is concerned with a rapid new method of identifying these vessels intraoperatively. In 9 pigs, a specially designed catheter with platinum and stainless steel electrodes was inserted intrathecally. Saline solution saturated with hydrogen was injected sequentially into arterial ostia at T-15 to L-4 inclusive, and the generated current impulses from the conditioned platinum electrode were recorded. Of 90 potential segmental arteries supplying the spinal cord, 28 gave rise to spinal radicular arteries. Hydrogen-induced current impulses correctly located 25 of the radicular arteries and all those larger than 180 μm in diameter. When injected with indigo carmine, the vessels localized by the hydrogen-induced current impulses filled the entire anterior spinal artery from the low thoracic to the sacral region, whereas injection of the other vessels did not show filling. After refinement and testing for safety, this method has been employed clinically to rapidly localize and reattach routes of critical cord circulation.

Appraisal of cerebrospinal fluid alterations during aortic surgery with intrathecal papaverine administration and cerebrospinal fluid drainage

We have previously described a technique for intrathecal administration of papaverine and cerebrospinal fluid drainage to prevent paraplegia after aortic surgery. Herein we report the cerebrospinal fluid and hemodynamic alterations that occurred in 11 patients who had 30 mg of a specially prepared papaverine hydrochloride 10% dextrose solution injected before aortic cross-clamping and also had cerebrospinal fluid drainage. A mean of 26.6 ml (SD ± 7.1 ml) was drained before and 34.6 ml (SD ± 24.1 ml) was drained during aortic cross-clamping. The cerebrospinal fluid pressure increased significantly with anesthetic induction (p < 0.03), during the period between anesthetic induction and cerebrospinal fluid drainage (p < 0.005), and with aortic cross-clamping (p < 0.05). These cerebrospinal fluid pressure alterations were similar to central venous pressure increases with a significant linear correlation between cerebral spinal fluid pressure and central venous pressure before anesthetic induction (r2 = 0.81, p < 0.005), and both before (r2 = 0.94, p < 0.005) and after (r2 = 0.74, p < 0.005) aortic cross-clamping. As expected, cerebrospinal fluid pressure was significantly reduced by cerebrospinal fluid drainage before aortic cross-clamping (p < 0.001). The administration of intrathecal papaverine had no significant effect on mean arterial pressure, systemic vascular resistance, cerebrospinal fluid pressure, nor the pH of cerebrospinal fluid. Neither were there any complications noted related to the technique. All the patients survived, and no new immediate postoperative paraparesis or paraplegia occurred. The technique described may be used with other methods, such as distal aortic perfusion, in an attempt to protect the spinal cord against ischemic damage, and it may allow the surgeon a longer time to reanastomose critical segmental arteries to maintain spinal cord blood supply.