Thoracoabdominal aneuryThoracoabdominal aneurysm surgery and the risk of sm surgery and the risk of paraplegia: intraoperative paraplegia: intraoperative

neuroprotectionneuroprotectionPresent by Ri Present by Ri 顏廷珊顏廷珊2003/4/142003/4/14

Anatomy review: spinal cord blood Anatomy review: spinal cord blood supplysupply

AortaAorta intercostal a intercostal arteriesrteries One anterior spinal One anterior spinal artery: supply ventraartery: supply ventral 2/3 spinal cordl 2/3 spinal cord Two posterior arterTwo posterior artery: supply dorsal 1/3 sy: supply dorsal 1/3 spinal cordpinal cord

Upper 2/3 of anterior spiUpper 2/3 of anterior spinal artery is continuous nal artery is continuous and has constant caliberand has constant caliber In lower thoracic regent, In lower thoracic regent, it decreased in caliber, ait decreased in caliber, and there is often one larnd there is often one large intercostal branch whge intercostal branch which supple this segmentich supple this segment

artery of Admakiewic artery of Admakiewicz (ARM)z (ARM) 75% in T9-T1275% in T9-T12

Crawford classificationCrawford classification Type I: proximal Type I: proximal

descending to upper descending to upper abdominal aortaabdominal aorta

Type II: proximal Type II: proximal descending to the descending to the below the renal below the renal arteriesarteries

Type III: distal half to Type III: distal half to the abdominal aortathe abdominal aorta

Type IV: most or all Type IV: most or all abdominal aortaabdominal aorta

Strategies for prevention of spinal Strategies for prevention of spinal cord ischemic injurycord ischemic injury

1.1. Identification of critical vessels and intIdentification of critical vessels and intercostal artery anastomosisercostal artery anastomosis2.2. Distal aortic perfusionDistal aortic perfusion3.3. CSF drainageCSF drainage4.4. Spinal cord evoked potential monitoriSpinal cord evoked potential monitoringng5.5. HypothermiaHypothermia6.6. Ischemic preconditionIschemic precondition

Intercostal arteries anastomosisIntercostal arteries anastomosis When more than 9 pairs of intercostal arWhen more than 9 pairs of intercostal arteries are ligatedteries are ligated the incidence of para the incidence of paraplegia increases 29 foldsplegia increases 29 folds T9-L1T9-L1 most risky, exp. T11 and T12 most risky, exp. T11 and T12Safi et al. importance of intercostal artery reattachment during thoracoabdominal aortic aneurysSafi et al. importance of intercostal artery reattachment during thoracoabdominal aortic aneurysm repair, J Vasc Surg 27: 58-68, 1998m repair, J Vasc Surg 27: 58-68, 1998

Identification of critical vesselsIdentification of critical vessels Pre-op evaluation:Pre-op evaluation:1.1. angiographyangiography controversial ?! controversial ?!2.2. MRAMRA being advantageous, may reduc being advantageous, may reduce spinal cord injury and operation timee spinal cord injury and operation timeStrategies for spinal cord protection during descending thoracic and thoracStrategies for spinal cord protection during descending thoracic and thoracoabdominal aortic surgery: up-to-date experimental and clinical resuloabdominal aortic surgery: up-to-date experimental and clinical result, Scand Cardiovasc J 36, 136-160, 2002t, Scand Cardiovasc J 36, 136-160, 2002

Identification of critical vesselsIdentification of critical vessels Intra-op evaluation:Intra-op evaluation:1.1. Monitoring evoked potentialMonitoring evoked potential no convincin no convincing evidence showing benefitg evidence showing benefit

Griepp et al.Griepp et al.1.1. Hydrogen electrode technique Hydrogen electrode technique still in expe still in experimental studies, but the results are encourarimental studies, but the results are encouragingging

Svensson et al.Svensson et al.1.1. Doppler ultrasonography Doppler ultrasonography in dogs in dogs ?? ??

Shibata et al.Shibata et al.

Effects of clamping the descending Effects of clamping the descending thoracic aortathoracic aorta

The risk of ischemic damage to the spinaThe risk of ischemic damage to the spinal cord with normothermic simple aortic l cord with normothermic simple aortic clampingclamping directly related to the clamp directly related to the clamping timeing time the risk of paraplegia begins to increase the risk of paraplegia begins to increase after 30 min, rise dramatically after 40 mafter 30 min, rise dramatically after 40 mininHilgenberg AD et al, Blunt traumatic rupture of the thoracic aorta, Ann ThorHilgenberg AD et al, Blunt traumatic rupture of the thoracic aorta, Ann Thorac Surg 53:233-239, 1992ac Surg 53:233-239, 1992

Effects of clamping the descending Effects of clamping the descending thoracic aortathoracic aorta

proximal to the clamp proximal to the clamp increase in the arterial presincrease in the arterial pressure sure increase in afterload increase in afterload hypertension in brai hypertension in brain and stimulation of aortic receptors n and stimulation of aortic receptors increase CSF increase CSF pressurepressure Distal to the clamp Distal to the clamp hypotension hypotension hypoperfusion hypoperfusion a spinal cord perfusion pressure > 60 mmHg to maina spinal cord perfusion pressure > 60 mmHg to maintain cord functiontain cord function

Hilgenberg AD, spinal cord protection for thoracic aortic surgery, Cardiology Clinic, Vol 17:4: 1999Hilgenberg AD, spinal cord protection for thoracic aortic surgery, Cardiology Clinic, Vol 17:4: 1999

Distal aortic perfusionDistal aortic perfusion1.1. Passive shunt: Passive shunt: proximal to distal aorta, femoral vein to femproximal to distal aorta, femoral vein to femoral artery, left atrial to femoral arteryoral artery, left atrial to femoral artery

provide suboptimal blood flow and perfus provide suboptimal blood flow and perfusion pressure (< 40 mmHg)ion pressure (< 40 mmHg)

Hilgenberg AD, spinal cord protection for thoracic aortic surgery, Cardiology Clinic, VHilgenberg AD, spinal cord protection for thoracic aortic surgery, Cardiology Clinic, Vol 17:4: 1999ol 17:4: 1999

Distal aortic perfusionDistal aortic perfusion Partial bypass:Partial bypass:

left atriumleft atrium centrifugal pump centrifugal pump distal aorta or distal aorta or femoral artery femoral artery maintain proximal maintain proximal artery systolic artery systolic pressure 100-140 pressure 100-140 mmHg, distal artery mmHg, distal artery mean pressure 70 mean pressure 70 mmHgmmHg

CSF drainageCSF drainage Spinal cord perfusion pressure= spinal artery bSpinal cord perfusion pressure= spinal artery blood pressure – CSF pressurelood pressure – CSF pressure Intra-op protectionIntra-op protection inconclusive inconclusive Reverse delayed onset paraplegia post-op!Reverse delayed onset paraplegia post-op! Currently accepted principles:Currently accepted principles:maintaining a CSF pressure at 10-12 mmHg anmaintaining a CSF pressure at 10-12 mmHg and continuing the CSF drainage for 24-72 hours d continuing the CSF drainage for 24-72 hours post-oppost-opZvara: thoracoabdominal aneurysm surgery and the risk of paraplegia: contZvara: thoracoabdominal aneurysm surgery and the risk of paraplegia: contemporary practice and future direction, J American society of Extra-corpemporary practice and future direction, J American society of Extra-corpo technology, 2002:34:11-17o technology, 2002:34:11-17

Spinal cord evoked potential Spinal cord evoked potential monitoringmonitoring

Somatosensory cortical evoked potential Somatosensory cortical evoked potential 1.1. Most common, good clinical results for intra-op guidMost common, good clinical results for intra-op guidanceance2.2. Posterior tibial or peroneal nervesPosterior tibial or peroneal nerves posterior and l posterior and lateral columns of spinal cordateral columns of spinal cord scalp scalp3.3. Detection if there are changes in latency or amplitudDetection if there are changes in latency or amplitudee4.4. Not directly monitor the function of anterior column Not directly monitor the function of anterior column but the posterior and lateral columnbut the posterior and lateral column5.5. Post-op paraplegia may occur despite unchanged inPost-op paraplegia may occur despite unchanged intra-op SEPs tra-op SEPs Strategies for spinal cord protection during descending thoracic and thoracStrategies for spinal cord protection during descending thoracic and thoracoabdominal aortic surgery: up-to-date experimental and clinical resuloabdominal aortic surgery: up-to-date experimental and clinical result, Scand Cardiovasc J 36, 136-160, 2002t, Scand Cardiovasc J 36, 136-160, 2002

Spinal cord evoked potential Spinal cord evoked potential monitoringmonitoring

Motor evoked potentialMotor evoked potential1.1. Motor cortex or spinal cord proximal to the clMotor cortex or spinal cord proximal to the clamping site amping site lower spinal cord, peripheral n lower spinal cord, peripheral nerves or muscleerves or muscle2.2. Affected by many anesthetic drugs: propofol, Affected by many anesthetic drugs: propofol, NO, BZD…NO, BZD…3.3. No good correlationNo good correlation monitoring the white monitoring the white matter of the anterior column rather than gramatter of the anterior column rather than gray mattery matter4.4. Monitoring of MEPs is and extremely sensitivMonitoring of MEPs is and extremely sensitive and fast method to detect the occurrence oe and fast method to detect the occurrence of intra-op SCIf intra-op SCI

Spinal cord evoked potentialsSpinal cord evoked potentials An electrode inserted in the epidural space anAn electrode inserted in the epidural space and recorded by another electrode, or direct stid recorded by another electrode, or direct stimulation of the cordmulation of the cord Yamamoto et al.: lumbar descending ESP was Yamamoto et al.: lumbar descending ESP was the most reliable method for predicting post-othe most reliable method for predicting post-op neurologic outcomep neurologic outcome Fan et al: significantly correlated with regional Fan et al: significantly correlated with regional spinal cord blood flow at the lumbar segment spinal cord blood flow at the lumbar segment

HypothermiaHypothermia Neuroprotection: reduce spinal cord metaboNeuroprotection: reduce spinal cord metabolic rate, decrease CSF neurotransmitter level lic rate, decrease CSF neurotransmitter level Systemic hypothermiaSystemic hypothermia1.1. Deep hypothermic circulatory arrest (18C) Deep hypothermic circulatory arrest (18C) the best condition for repair, for 45-60 minthe best condition for repair, for 45-60 minKouchoukos et al. hypothermic bypass and circulatory arrest for operation of the desKouchoukos et al. hypothermic bypass and circulatory arrest for operation of the desc. Thoracic and thoracoabdominal aorta. Ann Thoracic Surg.1995; 60:67-77c. Thoracic and thoracoabdominal aorta. Ann Thoracic Surg.1995; 60:67-771.1. Moderate hypothermia(29-31C)Moderate hypothermia(29-31C) reduce spi reduce spinal cord ischemic injurynal cord ischemic injurySvensson et al. reduction of neurologic injury after high-risk thoracoabdominal aortic Svensson et al. reduction of neurologic injury after high-risk thoracoabdominal aortic operation. Ann Thoracic Surg. 1998; 66: 132-8operation. Ann Thoracic Surg. 1998; 66: 132-8

HypothermiaHypothermia Regional hypothermiaRegional hypothermia1.1. Epidural injection of iced saline with mEpidural injection of iced saline with monitoring and drainage of CSFonitoring and drainage of CSF spinal spinal cord temperature 25-28C cord temperature 25-28C good clinic good clinical resultsal resultsCambria et al. Epidural cooling for spinal cord protection during thoracoabdominal aCambria et al. Epidural cooling for spinal cord protection during thoracoabdominal anuerysm repair: a 5-year experience, J Vasc Surg. 2000; 31:1093-102nuerysm repair: a 5-year experience, J Vasc Surg. 2000; 31:1093-1021.1. Local cold packingLocal cold packing in animal study in animal study ?? ??

Ueno et al, Ueno et al,

Ischemic preconditionIschemic precondition The natural physiologic process where by shorThe natural physiologic process where by short, sublethal events of ischemia to an organ initit, sublethal events of ischemia to an organ initiate a protective cellular process by which the ate a protective cellular process by which the organ is protected from a subsequent, usually organ is protected from a subsequent, usually lethal ischemic insult.lethal ischemic insult. Mechanism: unclear, Probably mediated by prMechanism: unclear, Probably mediated by production of heat shock protein 70 and 110/105,oduction of heat shock protein 70 and 110/105, adenosine receptors, alpha agonist, and pota adenosine receptors, alpha agonist, and potassium-dependent ATP channelsssium-dependent ATP channelsZvara: thoracoabdominal aneurysm surgery and the risk of paraplegia: contemporarZvara: thoracoabdominal aneurysm surgery and the risk of paraplegia: contemporary practice and future direction, J American society of Extra-corpo technology, 200y practice and future direction, J American society of Extra-corpo technology, 2002:34:11-172:34:11-17

Ischemic preconditionIschemic precondition Zvara et al.: 3min precondition eventZvara et al.: 3min precondition event 30 mi 30 min n 12 min ischemia 12 min ischemia spinal cord protectio spinal cord protection!n! Munyao et al.: 12.5 min precondition event Munyao et al.: 12.5 min precondition event

12 hours 12 hours 30 min ischemia, better results 30 min ischemia, better results than 24 hours delaythan 24 hours delay Clinical debates:Clinical debates:No known optimal timing !! No known optimal timing !!

Strategies for spinal cord protection during descending thoracic and thoracoabdomiStrategies for spinal cord protection during descending thoracic and thoracoabdominal aortic surgery: up-to-date experimental and clinical result, Scand Cardiovanal aortic surgery: up-to-date experimental and clinical result, Scand Cardiovasc J 36, 136-160, 2002sc J 36, 136-160, 2002

Pharmacological protectionPharmacological protection Stabilize cellular membranes : Ca channel blocStabilize cellular membranes : Ca channel blocker, MgSO4ker, MgSO4 Decrease neurologic metabolic activity: ketamDecrease neurologic metabolic activity: ketamineine Scavenge free radicals: allopurinal Scavenge free radicals: allopurinal Reduce intracellular edema: mannitol Reduce intracellular edema: mannitol Decrease inflammation: glucocorticoidsDecrease inflammation: glucocorticoids Currently there is no convincing data regardinCurrently there is no convincing data regarding the efficacy of any of these drugs !g the efficacy of any of these drugs !

T.H Webb and G.M Williams, JHHT.H Webb and G.M Williams, JHHthoracic abdominal aneurysm repair: cardiovascular surg 7thoracic abdominal aneurysm repair: cardiovascular surg 7

(6):573-585, 1999(6):573-585, 1999

JHH repair techniqueJHH repair technique1.1. Pre-op spinal angiography: successfully localPre-op spinal angiography: successfully localized in ~60% of patients, ¾ from left side, 80ized in ~60% of patients, ¾ from left side, 80% form T9-T12% form T9-T122.2. CSF drainCSF drain3.3. Epidural spinal electrode for continuous spinEpidural spinal electrode for continuous spinal cord evoked potential and standard peripal cord evoked potential and standard peripheral somatosensory evoked potential monitheral somatosensory evoked potential monitoringoring

Bypass with a centrifugal blood pump and heat exchaBypass with a centrifugal blood pump and heat exchanger:nger:ProximalProximal inf. Pulmonary vein with tip in left atrium inf. Pulmonary vein with tip in left atriumDistalDistal left femoral artery left femoral artery Moderate hypothermia: systemic cooling to 32CModerate hypothermia: systemic cooling to 32C Segmental clamping and repair: spinal artery ischemiSegmental clamping and repair: spinal artery ischemia for 10-15 min, visceral and renal ischemia for 15-40 a for 10-15 min, visceral and renal ischemia for 15-40 min, no significant hypotension occuredmin, no significant hypotension occured Reimplantation of pre-op localized spinal arteryReimplantation of pre-op localized spinal artery CSF drainage was continued for 72 h post-opCSF drainage was continued for 72 h post-op

Result Result 1993-1997,145 cases, 62% Crawford I or I1993-1997,145 cases, 62% Crawford I or II, 26 % dissection, 9% ruptureI, 26 % dissection, 9% rupture SCI: 5.8 %(Paraplegia/ paraparesis =3.6SCI: 5.8 %(Paraplegia/ paraparesis =3.6%/ 2.2%)%/ 2.2%) Mortality: 11%Mortality: 11%

Discussion Discussion No cord events developed in p’t with sNo cord events developed in p’t with successful pre-op localization of spinal aruccessful pre-op localization of spinal arteries and had critical intercostal vessels teries and had critical intercostal vessels reimplanted.reimplanted. No pre-op localization, no succesful locaNo pre-op localization, no succesful localization lization even reimplantation of lower i even reimplantation of lower intercostal vessels ntercostal vessels high risk of cord ev high risk of cord eventent

Pre-op localization of critical vesselsPre-op localization of critical vessels

Richard P, Cambria MD et al (MGH), Thoracoabdominal anRichard P, Cambria MD et al (MGH), Thoracoabdominal aneurysm repair: results with 337 operation performed over a eurysm repair: results with 337 operation performed over a

15-year interval: Ann of Surg: 236(4): 471-47915-year interval: Ann of Surg: 236(4): 471-479

MGH repair techniqueMGH repair technique1.1. Clamp and sewClamp and sew2.2. Distal perfusion only in highly selected p’ts ( complDistal perfusion only in highly selected p’ts ( complexity in surgery, significant renal insufficiency)exity in surgery, significant renal insufficiency)3.3. Regional hypothermia with epidural cooling (26C)Regional hypothermia with epidural cooling (26C)4.4. Reimplantation of patent T9-L1 intercostal vesselsReimplantation of patent T9-L1 intercostal vessels5.5. Continuous CSF drainage after restoration of lower Continuous CSF drainage after restoration of lower extremity perfusion and discontinuation of EC, for 4extremity perfusion and discontinuation of EC, for 48-72 hr 8-72 hr

Result Result 1987-2001, 337 cases, 44% Crawford I or 1987-2001, 337 cases, 44% Crawford I or II, 24.3%urgent casesII, 24.3%urgent cases SCI: 11.4% (Paraplegia/ paraparesis =6.SCI: 11.4% (Paraplegia/ paraparesis =6.6%/ 4.8%)6%/ 4.8%) Mortality: 8.3%Mortality: 8.3%

Discussion Discussion Multivariate analysis of variables Multivariate analysis of variables

associated with SCIassociated with SCIvariablevariable P valueP valueTAA type I/II vs III/IVTAA type I/II vs III/IV 0.0390.039Aneurysm ruptureAneurysm rupture 0.0340.034Total cross clamp timesTotal cross clamp times 0.00190.0019Patent critical zone intercostal sacriPatent critical zone intercostal sacrifice(T9-L1)fice(T9-L1) 0.0310.031

Intra-op hypotensionIntra-op hypotension 0.0280.028

Distal perfusion only in highly selective Distal perfusion only in highly selective patientspatients mostly rely on neuroprotectiv mostly rely on neuroprotective strategies.e strategies. Hypothermia (Epidural Cooling) is the bHypothermia (Epidural Cooling) is the best method of cord protection.est method of cord protection. An aggressive posture of intercostal revaAn aggressive posture of intercostal revasculization has in our view been conclusisculization has in our view been conclusively proven to be benefit.vely proven to be benefit.