Distal Aortic Perfusion Research Articles

Thoracoabdominal aortic aneurysms open repair: a multimodal approach

Thoracoabdominal aortic aneurysms (TAAA) open repair consists of graft replacement with reattachment of the aortic branches. A multimodal approach with different adjuncts has progressively evolved to maximize organ protection and reduce surgical trauma. Preoperative strategies and intraoperative techniques include precise modern imaging, spinal cord (SC) protection, distal aortic and visceral vessels perfusion with left heart bypass and use of new grafts. The surgical technique and the use of the different adjuncts are discussed.

Abdominal organ protection strategy for aortic arch aneurysm surgery.

Body temperature maintained during open distal anastomosis in patients who undergo aortic surgery has been showing an upward trend; however, a higher temperature may increase visceral organ and spinal cord injury. Distal perfusion may reduce abdominal organ injury, especially acute kidney injury (AKI). From 2009 to 2016, 56 patients who underwent ascending aortic and/or aortic arch surgery were enrolled. Open distal anastomosis was performed using one of three protection strategies: 1) systemic temperature of 25°C followed by selective cerebral perfusion (SCP) with lower body circulatory arrest (Group CA25, n=27); 2) systemic temperature of 28°C followed by SCP with lower body circulatory arrest (Group CA28, n=4); and 3) systemic temperature of 28°C followed by SCP with distal aortic perfusion (Group DP, n=25). During the postoperative course, levels of blood urea nitrogen, creatinine, liver enzymes, lactate dehydrogenase and lactate in Groups CA28 and CA25 were significantly higher than those in Group DP. AKI defined by the AKI Network occurred in 28 cases (50%) and 3 cases required permanent hemodialysis. AKI was significantly higher in Groups CA25 and CA28 than in Group DP (p=0.026). Mid-term follow-up showed that patients who developed postoperative AKI were more likely to suffer from cardiovascular events. Distal perfusion during open distal anastomosis reduced kidney and liver injury after thoracic aortic surgery despite an increased body temperature of up to 28°C. This strategy may be useful to prevent AKI, liver dysfunction, the need for hemodialysis and multiple organ failure and could improve mid-term results.

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 130mmHg 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.

State-of the-art review on the renal and visceral protection during open thoracoabdominal aortic aneurysm repair.

During open thoracoabdominal aortic aneurysm repair (OTAAAR), there is an inevitable organ ischemic period that occurs when the abdominal arteries are being reattached to the aortic graft. Despite various protective techniques, the incidence of renal and visceral complications remains substantial. This state-of-the-art review gives an overview of the current and most evidence-based organ protection methods during OTAAAR, based on the most recent publications and personal experience. An electronic search was performed in four medical databases, using the following MeSH terms: thoracoabdominal aneurysm, TAAAR, visceral protection, renal protection, kidney, perfusion, and intestines. Every publication type was considered. The literature search was ended on August 31st, 2017. The left heart bypass (LHB) is currently the most frequent adjunct to provide distal aortic perfusion (DAP) during aortic clamping. Together with systemic hypothermia, it forms the cornerstone in organ protection during aortic clamping. Further renal protection can be obtained by selective renal perfusion (SRP) with cold blood or cold crystalloid solution, the latter enriched with mannitol. The perfusion should be administered in a volume- and pressure-controlled way and, if possible, by use of a pulsatile pump. Selective visceral perfusion (SVP) is not routinely used, as it does not provide adequate blood flow for visceral protection. The best way to protect the intestines is by minimizing the ischemic time. The preservation of renal and visceral function after OTAAAR can only be obtained with specific strategies before, during, and after the operation. This involves a series of measures, including selective digestive decontamination (SDD), avoidance of nephrotoxic drugs, minimizing the renal and intestinal ischemic time, systemic cooling, avoidance of hemodynamic instability, and regional protective perfusion of the kidneys. Future innovations in catheters, cardiac bypass flow types, mechanical components, hybrid vascular grafts, and pharmaceutical protection measures will hopefully further reduce organ complications.

Maintenance of High Blood Pressure and Early Establishment of Pulsatile Blood Flow to the Spinal Cord during Thoracoabdominal Aortic Repair

Objectives: Despite continuous advancements in the surgical treatments for thoracoabdominal aortic aneurysms (TAAA), paraplegia remains a devastating treatment-related complication. We aimed to summarize our experience with a novel surgical strategy involving maintenance of high blood pressure and early establishment of pulsatile blood flow to the spinal cord. Materials and Methods: Between August 2011 and October 2017, 29 patients (age, 67 ± 12 years) underwent open surgery for TAAA. According to the Crawford classification, two aneurysms were type I, eight were type II, 12 were type III, and seven were type IV. We used partial cardiopulmonary bypass under mild hypothermia in all patients except one. By maintaining distal aortic perfusion pressure at 60 - 80 mmHg and creating the distal aortic anastomosis before visceral branch reconstruction, we established early perfusion of the hypogastric arteries with native pulsatile flow. Intraoperative spinal monitoring and cerebrospinal fluid drainage were performed in 26 (90%) and 23 (79%) patients, respectively. Nineteen patients (66%) underwent reconstruction of the intercostal arteries. During perioperative management, the mean arterial pressure was kept >80 mmHg. Results: No in-hospital deaths or acute neurological complications occurred. One patient (3.4%) experienced delayed temporal paraplegia. During follow-up, aorta-related death occurred in only one patient, who developed prosthetic vascular graft infection but did not undergo repeat graft replacement. The 3-year freedom from aortic-related death was 95%. Conclusion: Our surgical strategy involving maintenance of high blood pressure and early establishment of pulsatile flow to the spinal cord was effective in preventing spinal cord injury following open surgery for TAAA.

Custom-Made E-Vita Graft for Frozen Elephant Trunk With Arch-First Technique

A novel custom-made E-Vita Open prosthesis (JOTEC GmbH, Hechingen, Germany) has been designed with 2 additional side branches. The first one, the reperfusion branch, allows distal aortic perfusion after the collar anastomosis of a frozen elephant trunk repair has been performed. The second one, the debranching branch, permits reimplantation of any configuration of supraaortic debranching to the dacron graft. This modified graft provides two main advantages: first, combined with prior carotid-subclavian bypass and bilateral axillary perfusion, it allows continuous bihemispheric antegrade perfusion and arch-first technique under mild hypothermia (32°C); second, it grants distal aortic reperfusion after distal anastomosis completion performed under moderate hypothermia (28°C).

Japanese perspective in surgery for thoracoabdominal aortic aneurysms.

Operative mortality and morbidity after thoracoabdominal aortic surgery remain high. We report our strategy and outcomes, especially those of spinal cord protection. Outcomes of 178 patients (age: 26-88years) who underwent thoracoabdominal aortic replacement were retrospectively analyzed. 65 had aortic dissection, 14 had infected aneurysms, and 22 presented with rupture. Operations were non-elective in 24 and redo through re-thoracotomy in 21. Extent of replacement was Crawford-I in 39, II in 26, III in 78, and IV in 35. Staged repair was recently preferred, which resulted in decrease in extent II repair and increase in redo since 2009. Operations were performed under distal aortic perfusion and multi-segmental sequential repair to maximize collateral blood flow, and deep hypothermic circulatory arrest was preserved for those requiring open aortic anastomosis (n = 20). A total of 166 separate grafts were used for intercostal reconstruction in 88 patients, which was guided by preoperative feeding artery localization. Their patency was studied by postoperative MD-CT in 74 patients for 145 grafts. There were 3.9% hospital mortality and 5.1% spinal cord injury. Preoperative feeding artery localization resulted in reduced number of reconstruction and improved patency, and grafts connecting to the feeding artery were patent in 92%. Results of redo operations were not different (no mortality and spinal cord injury) from the de novo operations. Our concept of spinal cord protection, which was based on selective intercostal reconstruction while maximizing spinal cord collateral blood flow, seems justified.

Novel Rotational Speed Modulation System Used With Venoarterial Extracorporeal Membrane Oxygenation

Femoral venoarterial extracorporeal membrane oxygenation (VA-ECMO) is widely used to maintain blood flow in patients with cardiogenic shock. However, retrograde blood flow increases left ventricular (LV) afterload during femoral VA-ECMO. Additional support by means of an intraaortic balloon pump (IABP) alleviates LV afterload but is associated with significant adverse events. We previously developed a system for rotational speed modulation in synchrony with the native cardiac cycle, for use with implantable continuous-flow LV assist devices. Here, we aimed to evaluate whether our novel rotation speed modulation system can improve coronary artery flow and reduce LV during femoral VA-ECMO. VA-ECMO was installed by means of right atrial drainage and distal abdominal aortic perfusion in six adult goats. Cardiogenic shock was induced with β-adrenergic antagonist infusion. An IABP was placed in the descending aorta. LV stroke work, LV end-systolic pressure, and coronary arterial flow were evaluated. Data were collected under five conditions (modes): baseline, circuit-clamp (cardiogenic shock), continuous mode (constant rotational speed), counterpulse mode (increasing rotational speed during diastole), and continuous mode with IABP support. LV stroke work and LV end-systolic pressure tended to be lower in the counterpulse mode, indicating decreased LV work load and afterload in this mode. Furthermore, coronary arterial flow tended to be higher in the counterpulse mode. Our system enabled an increase in coronary arterial flow and a decrease in LV work load and afterload during VA-ECMO. The system offers the effects of VA-ECMO and an IABP in a single device.

Whole body perfusion in patients undergoing frozen elephant trunk for type A acute aortic dissections.

The Frozen Elephant Trunk (FET) can be adopted in selected type A acute aortic dissections (TAAAD). During FET, a prolonged distal circulatory arrest exposes the spine and visceral organs to potential ischemic injuries. Antegrade distal aortic perfusion (ADAP) could minimize this risk: we describe the technical aspects of the simultaneous use of antegrade cerebral perfusion (ACP) and ADAP achieving a "Whole Body Perfusion" (WBP) during FET.

15. Aortic IOM for thoraco-abdominal aneurysm surgery

In this presentation, I will give an overview of why and how intraoperative neurophysiologic techniques help reducing post-operative neurologic deficit in Aortic surgery. I will start by briefly presenting the vascular anatomy of the spinal cord as well as of the main types of Aortic aneurysms, surgical repair procedures (i.e., open TAA repair with distal aortic perfusion and endovascular repair/TEVAR) and their associated neurological risks. I will continue with integrating the intraoperative neurophysiologic techniques within the main methods used for intraoperative neuroprotection that allow reaching the balance between metabolic demand of the spinal cord and its oxygen supply. Next, I will present the main neurophysiologic tests used during these procedures, including their role, and methodology. I will then give examples of how specific characteristics of neurophysiologic changes help with differential diagnosis of intraoperative spinal cord ischemia and its management. I will conclude with thoughts about delayed paraplegia and how intraoperative neurophysiology can help in predicting and preventing its occurrence, by informing the postoperative hemodynamic management in the ICU.

Extending resuscitative endovascular balloon occlusion of the aorta: Endovascular variable aortic control in a lethal model of hemorrhagic shock.

The duration of use and efficacy of resuscitative endovascular balloon occlusion of the aorta (REBOA) is limited by distal ischemia. We developed a hybrid endovascular-extracorporeal circuit variable aortic control (VAC) device to extend REBOA duration in a lethal model of hemorrhagic shock to serve as an experimental surrogate to further the development of endovascular VAC (EVAC) technologies. Nine Yorkshire-cross swine were anesthetized, instrumented, splenectomized, and subjected to 30% liver amputation. Following a short period of uncontrolled hemorrhage, REBOA was instituted for 20 minutes. Automated variable occlusion in response to changes in proximal mean arterial pressure was applied for the remaining 70 minutes of the intervention phase using the automated extracorporeal circuit. Damage-control surgery and whole blood resuscitation then occurred, and the animals were monitored for a total of 6 hours. Seven animals survived the initial surgical preparation. After 20 minutes of complete REBOA, regulated flow was initiated through the extracorporeal circuit to simulate VAC and provide perfusion to distal tissue beds during the 90-minute intervention phase. Two animals required circuit occlusion for salvage, while five animals tolerated sustained, escalating restoration of distal blood flow before surgical hemorrhage control. Animals tolerating distal flow had preserved renal function, maintained proximal blood pressure, and rapidly weaned from complete REBOA. We combined a novel automated, extracorporeal circuit with complete REBOA to achieve EVAC in a swine model of uncontrolled hemorrhage. Our approach regulated proximal aortic pressure, alleviated supranormal values above the balloon, and provided controlled distal aortic perfusion that reduced ischemia without inducing intolerable bleeding. This experimental model serves as a temporary surrogate to guide future EVAC catheter designs that may provide transformational approaches to hemorrhagic shock.

Passive Temporary Visceral Shunt from the Axillar Artery as an Adjunct Method during the Open Treatment of Thoracoabdominal Aortic Aneurysm

Distal aortic retrograde perfusion systems like the left heart bypass or femoro-femoral extracorporeal circulation are the methods of reference for organ protection during direct approaches to thoracoabdominal aortic aneurysms. The aim of this work was to evaluate the use of a passive arterial shunt to reduce visceral ischemia during aortic operations when occlusive diseases of the iliac arteries make distal aortic retrograde perfusion inappropriate. Ten patients affected by a Crawford type III thoracoabdominal aneurysm (TAA) were operated on between January 2013 and January 2015 with the use of a temporary shunt inserted onto the left axillar artery that allows visceral perfusion immediately after the aorta is opened. The operation was performed after a single dose of heparin (50 UI/kg). The sera lactate levels were measured 2hr after the last aortic clamp was removed and compared with those obtained from a group of 19 patients operated on for a Crawford type IV TAA during the same period without any arterial shunt. Neither mortality nor paraplegia occurred. The sera lactate levels were lower in the group of patients operated on for a type III TAA (2.57±1) than for a type IV TAA (3.68±1) (P<0.01, Student's t-test). This method was effective for low mesenteric ischemia, easy to perform, and did not require high doses of anticoagulants.

Extended Motor Evoked Potentials Monitoring Helps Prevent Delayed Paraplegia After Aortic Surgery

Motor evoked potentials (MEPs) monitoring can promptly detect spinal cord ischemia (SCI) from aortic clamping during open thoracoabdominal aneurysm repair (OTAAR) with distal aortic perfusion (DAP) and thus help decrease the risk of immediate postoperative SCI (IP-SCI). However, neither stable MEPs during aortic clamp interval (ACI) nor absence of IP-SCI eliminate the possibility of delayed postoperative SCI (DP-SCI). We hypothesized that extension of MEPs monitoring beyond ACI can also help decrease the risk of DP-SCI. We identified 150 consecutive patients at our institution between April 2005 and October 2014 who underwent OTAAR with DAP and MEPs monitoring and had no IP-SCI. Using logistic regression analysis, we studied the independent effect of extended MEPs monitoring on the risk of developing DP-SCI. We used a propensity score analysis to adjust for potential confounders, such as poorly controlled hypertension, previous aneurysm surgery, splenectomy, acute aortic dissection, aneurysm type, older age, and history of diabetes and smoking. From the 150 patients, 129 (86%) remained neurologically intact whereas 21 (14%) developed DP-SCI. Nineteen of these twenty-one patients (90%) had no extended monitoring. Fifty-seven of fifty-nine (97%) patients who benefited from extended monitoring had no DP-SCI (p = 0.003). Extended MEPs monitoring was independently associated with decreased risk of DP-SCI (odds ratio = 0.14; 95% confidence interval: 0.03, 0.65; p = 0.01). MEPs detect the lowest systemic blood pressure that ensures appropriate spinal cord perfusion in the postoperative period. Thus, they inform the hemodynamic management of patients post-OTAAR, particularly in the absence of a reliable neurological exam.

Favorable Outcomes of Open Surgical Repair for Blunt Aortic Injury in the Era of Endovascular Repair.

Background Long-term outcomes of open surgical repair with distal aortic perfusion for blunt aortic injury (BAI) remain undefined in this era of preferential thoracic endovascular aortic repair (TEVAR). Methods We retrospectively reviewed data from 31 consecutive patients (23 males; mean age, 46 ± 16 years) who underwent open surgical repair with distal aortic perfusion for acute BAI between 1998 and 2012 at our center and were followed up for 83 ± 47 months. Results In the 31 patients studied, BAI was most commonly secondary to traffic accidents (87%), with median accident-to-surgery time of 1 day. It was most commonly (90%) located at the isthmus. All patients had other injuries (injury severity score, 25 ± 6), 68% of which required surgery. The aorta was approached by left (84%) or bilateral (3%) thoracotomy, or median sternotomy (13%). During aortic cross-clamping (73 ± 47 minutes), distal aortic perfusion was maintained in all patients by left heart or cardiopulmonary bypass (extracorporeal circulation time, 93 ± 63 minutes). Circulatory arrest was required in 19% of patients. There was no in-hospital mortality or paraplegia. The estimated 5- and 10-year survival rates were 92 ± 6% and 80 ± 12%, respectively. One patient underwent reoperation for aortoesophageal fistula at 75 months postoperatively. Conclusion Open repair with distal aortic perfusion for BAI yielded favorable early and late outcomes, and is thus a viable option even in the era of TEVAR.

Optimizing Outcomes of Open Thoracoabdominal Aortic Aneurysm Repair

Open thoracoabdominal aortic aneurysm (TAAA) repair is a high-risk surgery associated with significant morbidity and mortality. It can be difficult to accumulate experience managing open TAAA repairs due to the low volume of cases and the increasing popularity of endovascular approaches. It is important to review management strategies for these challenging cases as clinical situations remain for which an open repair is preferred. Recent advances now allow for distal aortic perfusion during an off-pump open thoracoabdominal aortic aneurysm repair. This approach is not without risks and a clear, team based, plan is essential for successful management. Key considerations include managing co-morbidities, spinal cord protection, prevention of ischemia (coronary, cerebral, visceral, and peripheral), renal protection, massive transfusion, rapid hemodynamic changes, acidosis, coagulopathy, one lung ventilation, and postoperative pain control. In this case report, we detail an off-pump perioperative approach involving retrograde aortic perfusion, transesophageal echocardiography, and multiple spinal cord protective strategies which resulted in a favorable patient outcome.

Renal Dysfunction following Thoraco-abdominal Aortic Surgery: Occurrence and Long-Tterm Mortality

Introduction: Renal failure is a significant source of morbidity and mortality in patients who require thoraco-abdominal (TAA) aortic repair. We reviewed our 25 year experience with open descending thoracic and thoraco-abdominal repair to identify risk factors for and potential therapeutic targets to prevent renal failure. Methods: We performed 1896 operations in 1795 patients. The majority of cases were performed using cerebrospinal fluid drainage and distal aortic perfusion, and visceral perfusion was used selectively in patients with repairs that involved the origins of the celiac, superior mesenteric and renal arteries. Renal failure was defined as new-onset renal dysfunction in patients without existing chronic renal disease, and included an increase in post-op creatinine >1 mg/dl/day over the first two post-op days, an absolute creatinine >4 mg/dl or need for dialysis. Multivariable statistics were used to assess pre-and intra-operative risk factors for renal dysfunction, and the effect of renal morbidity on long-term survival was evaluated by Kaplan-Meier analysis. Results: Mean population age was 64.2 +/- 13.9, and 669/1795 (37%) patients were female. Renal dysfunction occurred after 488/1896 (25.7%) operations. Multivariable pre-operative predictors of post-operative renal failure were patient age (OR 1.03/yr, p < 0.0001), TAA extent 1 (OR 2.02, p < 0.0001), TAA2 (OR 5.9, p < 0.0001), TAA3 (OR 4.2, p < 0.0001), TAA4 (OR 2.9, p < 0.0001), emergency presentation (OR 1.4, p < 0.04) and coronary artery disease (CAD; OR 1.3, p < 0.04). Addition of intra-operative variables identified patient age (OR 1.03/yr, p < 0.0001), aortic dissection (OR 0.62, p < 0.002), involvement of the aortic segment containing the visceral vessel origins (OR 1.5, p < 0.005), COPD (OR 1.3, p < 0.02), aortic cross clamp time (OR1.02/min, p < 0.0001), and PRBC use (OR 1.04/unit, p < 0.0001). Visceral perfusion was associated with modestly increased risk (OR 1.3, p < 0.04) among patients with aneurysm extents (TAA 1, 2, and 4) involving the visceral vessels. Incidence of renal dysfunction has risen gradually over time. Long-term survival is strongly influenced by post-operative renal failure (Figure, p < 0.0001). Conclusion: New-onset renal dysfunction is common after thoraco-abdominal aortic surgery, and is strongly associated with reduced long-term survival. Renal protection strategies are urgently needed, and treatments that can reduce the effects of ischemic time and transfusion are likely intervention targets.

Extracorporeal circulation increases proliferation in the intestinal mucosa in a large animal model

Extracorporeal circulation induces ischemia/reperfusion injury in the small intestinal wall. One reason for this damage is a perfusion shift from the muscular toward the mucosal layer. This study investigated the effect of this perfusion shift on the small-intestinal apoptosis and proliferation. Twenty-eight pigs were randomly assigned to the following cohorts and underwent a thoracolaparotomy and a 1hour main procedure: cohort I: control; cohort II: thoracic aortic cross-clamping (TAC) without perfusion; cohort III: TAC and distal aortic perfusion (DAP); cohort IV: TAC, DAP, and selective visceral perfusion. The main procedure was followed by 2hours of reperfusion in all cohorts. Tissue samples were taken during the experiment, stained, and analyzed for apoptosis and proliferation (caspase-3, annexin-V, terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling, and proliferating cell nuclear antigen). Six animals died unexpectedly during the experiment and were excluded from the analysis. Extensive tissue damage and necrosis was only found in cohort II after the main procedure. In the mucosa, the proliferation was increased in cohort III at the end of the experiment (P= .0157 cohort I vs II). In contrast, the annexin-V/proliferating cell nuclear antigen ratio was significantly higher in cohorts II and IV than in cohorts I and II at the end of the experiment (P= .0034). Furthermore, the caspase-3/annexin-V ratio was increased in all cohorts at the end of the experiment (P= .0015). Mucosal proliferation is the early repair mechanism of the limited small intestinal ischemia/reperfusion injury after DAP. Furthermore, the extensive surgical trauma shifted the mucosal apoptosis into an advanced state.

Outcomes of Open Repair for Chronic Descending Thoracic Aortic Dissection

This study analyzed early and late outcomes after open repair of descending thoracic aortic aneurysms with chronic aortic dissection. We retrospectively reviewed our cases of open repair of descending thoracic aortic aneurysms with chronic dissection from 1991 to 2011. Patient comorbid conditions and operative details were analyzed to determine risks for adverse outcome. Long-term survival and aortic reinterventions were analyzed. We repaired 519 patients with descending thoracic aortic aneurysms during the study period, and 209 (40%) had chronic dissection. Mean age was 59 years, with 74% (154 of 209) men. Previous ascending repair was performed in 41% (85 of 209), and the second-stage elephant trunk was performed in 10% (21 of 209). Adjunctive distal aortic perfusion with cerebral spinal fluid drainage was used in 90% (188 of 209) of patients, and circulatory arrest with bypass in 1% (3 of 209). The 30-day mortality was 8.6% (18 of 209). Immediate neurologic deficit occurred in 0.95% (2 of 209) and only with extent Cresection. Delayed neurologic deficit occurred in 1.4% (3of 209), 1 patient in each extent. Because 66% (2 of 3) of the patients with delayed neurologic deficit recovered function, permanent deficit occurred in 1.4% (3 of 209). Stroke occurred in 2.4% (5 of 209) and dialysis on discharge in 5% (11 of 211). The only risk factor for 30-day mortality was preoperative glomerular filtration rate of less than 60 mL/min (odds ratio, 4.2; p < 0.006). Survival at 5, 10, and 15 years was 72%, 60%, and 49%, respectively. Freedom from reoperation on the operated-on segment was 98%, 96.5%, 96.5%, and 96.5% at 5, 10, 15, and 20 years. Open repairs of chronic descending thoracic aortic aneurysm dissections can be performed with respectable morbidity and mortality. Neurologic deficit remains low with the use of adjuncts, and early deaths are directly related to preoperative renal status. Reintervention on the involved aortic segment is low. These results allow comparisons with endovascular repair for chronic aortic dissection.

Selective renal blood perfusion induces renal tubules injury in a porcine model

Extracorporeal circulation is routinely used in thoracoabdominal aortic aneurysm repair to preserve blood perfusion. Despite this protective measure, acute and chronic kidney disorders can develop. Therefore, the aim of this study was to establish a new large-animal model to assess the efficacy of selective renal perfusion (SRP) with extracorporeal circulation in a setting of thoracoabdominal aortic aneurysm repair. Eighteen pigs underwent a thoracolaparotomy, during with the aorta and renal arteries were exposed. The animals were divided into three cohorts of six pigs each: cohort I--control; cohort II--thoracic aortic clamping with distal aortic perfusion (DAP) using a roller pump; and cohort III--thoracic aortic clamping with DAP plus SRP. Kidney metabolism, kidney injury, and red blood cell damage were measured by oxygen extraction ratio (O2ER), neutrophil gelatinase-associated lipocalin, a marker for acute kidney damage, and serum free hemoglobin. With normal mean arterial blood pressures, flow rates in the renal arteries during perfusion decreased to 75% (group II) with DAP and to 50% (group III) with SRP compared with the control animals (group I; P = .0279 for I vs II; P = .0002 for I vs III). Microcirculation, measured by microspheres, did not differ significantly among the groups. In contrast, O2ER (P = .0021 for I vs III) and neutrophil gelatinase-associated lipocalin (P = .0083 for I vs III) levels were significantly increased in group III, whereas free hemoglobin was increased in groups II and III (P = .0406 for I vs II; P = .0018 for I vs III). SRP with a roller pump induces kidney tubule injury. Thus, distal aortic and SRP in our model does not provide adequate kidney protection. Furthermore, the perfusion system provokes red blood cell damage with increased free hemoglobin. Hence, the SRP perfusion technique should be revised and tested.

Directly measuring spinal cord blood flow and spinal cord perfusion pressure via the collateral network: Correlations with changes in systemic blood pressure

During thoracoabdominal surgery in which segmental arteries are sacrificed over a large area, blood supply routes from collateral networks have received attention as a means of avoiding spinal cord injury. The aim of this study was to investigate spinal cord blood supply through a collateral network by directly measuring spinal cord blood flow and spinal cord perfusion pressure experimentally. In beagle dogs (n=8), the thoracoabdominal aorta and segmental arteries L1-L7 were exposed, and a temporary bypass was created for distal perfusion. Next, a laser blood flow meter was placed on the spinal dura mater in the L5 region to measure the spinal cord blood flow. The following were measured simultaneously when the direct blood supply from segmental arteries L2-L7 to the spinal cord was stopped: mean systemic blood pressure, spinal cord perfusion pressure (blood pressure within the aortic clamp site), and spinal cord blood flow supplied via the collateral network. These variables were then investigated for evidence of correlations. Positive correlations were observed between mean systemic blood pressure and spinal cord blood flow during interruption of segmental artery flow both with (r=0.844, P<.01) and without (r=0.834, P<.01) distal aortic perfusion. In addition, we observed significant correlations between spinal cord perfusion pressure and spinal cord blood flow with and without distal perfusion (r=0.803, P<.001 and r=0.832, P<.01, respectively), and between mean systemic blood pressure and spinal cord perfusion pressure with and without distal perfusion (r=0.898, P<.001 and r=0.837, P<.001, respectively). The spinal cord was perfused from the collateral network from outside the interrupted segmental arteries, and high systemic blood pressure (∼1.33-fold higher) was needed to obtain the preclamping spinal cord blood flow, whereas 1.68-fold higher systemic blood pressure was needed when distal perfusion was halted. Spinal cord blood flow is positively correlated with mean systemic blood pressure and spinal cord perfusion pressure under spinal cord ischemia caused by clamping a wide range of segmental arteries. In open and endovascular thoracic and thoracoabdominal surgery, elevating mean systemic blood pressure is a simple and effective means of increasing spinal cord blood flow, and measuring spinal cord perfusion pressure seems to be useful for monitoring perioperative spinal cord blood flow.