Elective Aortic Reconstruction Research Articles

Nondestructive Evaluation of Mechanical and Histological Properties of the Human Aorta With Near-Infrared Spectroscopy

IntroductionAscending aortic dilatation is a well-known risk factor for aortic rupture. Indications for aortic replacement in its dilatation concomitant to other open-heart surgery exist; however, cut-off values based solely on aortic diameter may fail to identify patients with weakened aortic tissue. We introduce near-infrared spectroscopy (NIRS) as a diagnostic tool to nondestructively evaluate the structural and compositional properties of the human ascending aorta during open-heart surgeries. During open-heart surgery, NIRS could provide information regarding tissue viability in situ and thus contribute to the decision of optimal surgical repair. Materials and methodsSamples were collected from patients with ascending aortic aneurysm (n = 23) undergoing elective aortic reconstruction surgery and from healthy subjects (n = 4). The samples were subjected to spectroscopic measurements, biomechanical testing, and histological analysis. The relationship between the near-infrared spectra and biomechanical and histological properties was investigated by adapting partial least squares regression. ResultsModerate prediction performance was achieved with biomechanical properties (r = 0.681, normalized root-mean-square error of cross-validation = 17.9%) and histological properties (r = 0.602, normalized root-mean-square error of cross-validation = 22.2%). Especially the performance with parameters describing the aorta's ultimate strength, for example, failure strain (r = 0.658), and elasticity (phase difference, r = 0.875) were promising and could, therefore, provide quantitative information on the rupture sensitivity of the aorta. For the estimation of histological properties, the results with α-smooth muscle actin (r = 0.581), elastin density (r = 0.973), mucoid extracellular matrix accumulation(r = 0.708), and media thickness (r = 0.866) were promising. ConclusionsNIRS could be a potential technique for in situ evaluation of biomechanical and histological properties of human aorta and therefore useful in patient-specific treatment planning.

Transfusion in Elective Proximal Aortic Reconstruction: Where Do We Currently Stand?

Aortic procedures are associated with higher risks of bleeding, yet data regarding perioperative transfusion in this patient population are lacking. We evaluated transfusion patterns in patients undergoing proximal aortic surgery to provide a benchmark against which future standards can be assessed. Between June 2014 and July 2017, 247 patients underwent elective aortic reconstruction for aneurysm. Patients with acute aortic syndrome, endocarditis, and/or prior cardiac surgery were excluded. Transfusion data were analyzed by type of operation: ascending aorta replacement ± aortic valve procedure (group 1, n = 122, 49.4%); aortic root replacement with a composite valve-graft conduit ± ascending aorta replacement (group 2, n = 93, 37.7%); valve-sparing aortic root replacement (VSARR) ± ascending aorta replacement (group 3, n = 32, 13.0%). Thirty-day mortality for the entire cohort was 2.02% (5 deaths). Overall, 75 patients (30.4%) did not require any transfusion of blood or other products. Patients in groups 1 and 3 were significantly more likely to avoid transfusion than those in group 2. Mean transfusion volume for any individual patient was modest; those who underwent VSARR (group 3) required less intraoperative red blood cells (RBC) than others. Intraoperative transfusion of RBC was independently associated with an increased risk of death at 30 days. Elective proximal aortic reconstruction can be performed without the need for excessive utilization of blood products. Composite root replacement is associated with a greater need for transfusion than either VSARR or isolated replacement of the ascending aorta.

Extended intensive care correlates with worsening of surgical outcome after elective abdominal aortic reconstruction

The aim of this study was to evaluate the impact of extended postoperative intensive care on short- and long-term patient outcome after elective abdominal aortic surgery and to assess the risk factors for patient survival after extended intensive care unit (ICU) treatment. The data of 231 patients that underwent open or endovascular abdominal aortic surgery were retrospectively analysed with regard to extended postoperative intensive care, defined as ICU treatment for more than 24 consecutive hours. Pre- and intraoperative factors were evaluated. The endpoints of the study were postoperative complications, mortality, and long-term follow-up. Univariate and multivariate Cox proportional regression analyses were performed to identify risk factors of worse overall survival. Extended postoperative intensive care was needed in 84 patients (63 after open and 21 after endovascular surgery). The period of ICU treatment was similar in both groups. Only the wound complications (31.8% vs. 9.5%, P=0.0498; OR 4.42 [0.94-20.84]) and the rate of acute kidney injury (82.5% vs. 57.1%, P=0.0352; OR 3.55 [1.20-0.46]) were more frequent after open surgery, whereas brief reactive psychosis (38.1% vs. 14.3%, P=0.0281; OR 0.27 [0.09-0.84]) was more frequent after endovascular surgery. ICU stay of ≥8 days correlated with significantly lower survival rates compared to a shorter ICU stay (P=0.0034), independent of open or endovascular techniques. Other multivariate risk factors for worse survival were the absence of preoperative aspirin medication, a Body Mass Index (BMI) of <25, chronic renal insufficiency, and coronary artery disease. Endovascular therapy was a positive predictive factor of short ICU stay of ≤3 days. The outcome after extended intensive care following elective aortic surgery is strongly dependent on the length of ICU stay.

The use of innominate artery cannulation for antegrade cerebral perfusion in aortic dissection

BackgroundDirect cannulation of the innominate artery for selective antegrade cerebral perfusion has been shown to be safe in elective proximal aortic reconstructions. We sought to evaluate the safety of this technique in acute aortic dissection.MethodsA multi-institutional retrospective review was undertaken of patients who underwent proximal aortic reconstruction for Stanford type A dissection between 2006 and 2016. Those patients who had direct innominate artery cannulation for selective antegrade cerebral perfusion were selected for analysis.ResultsSeventy-five patients underwent innominate artery cannulation for ACP for Stanford Type A Dissections. Isolated replacement of the ascending aorta was performed in 36 patients (48.0%), concomitant aortic root replacement was required in 35 patients (46.7%), of whom 7 had a valve-sparing aortic root replacement, ascending aorta and arch replacement was required in 4 patients (5%). Other procedures included frozen elephant trunk (n = 11 (14.7%)), coronary artery bypass grafting (n = 20 (26.7%)), and peripheral arterial bypass (n = 4 (5.3%)). Mean hypothermic circulatory arrest time was 19 ± 13 min. Thirty-day mortality was 14.7% (n = 11). Perioperative stroke occurred in 7 patients (9.3%).ConclusionsThis study is the first comprehensive review of direct innominate artery cannulation through median sternotomy for selective antegrade cerebral perfusion in aortic dissection. Our experience suggests that this strategy is a safe and effective technique compared to other reported methods of cannulation and cerebral protection for delivering selective antegrade cerebral perfusion in these cases.

Hybrid arch frozen elephant trunk repair: evidence from the Canadian Thoracic Aortic Collaborative.

The frozen elephant trunk (FET) technique has become an increasingly popular strategy for aortic reconstruction in the setting of extensive thoracic aortic aneurysms or dissections. The objective of this study is to report on the Canadian experience with the FET technique in both the elective and emergent settings. A total of 167 consecutive patients (mean age 65±13 years, 30% female, 25% re-operation) underwent elective (70%) and non-elective (30%) aortic arch reconstruction with the FET technique between May 2008 and October 2019 in six centers of the Canadian Thoracic Aortic Collaborative (CTAC). In-hospital clinical endpoints and early imaging endpoints were prospectively collected and analyzed. All 167 patients underwent successful FET implantation. In-hospital mortality occurred in 14 patients (8%), stroke occurred in 22 patients (13%) and temporary and permanent spinal cord ischemia (SCI) occurred in 6 (3.6%) and 3 (1.8%) patients, respectively. Prolonged mechanical ventilation was required in 35 patients (21%), renal failure requiring dialysis in 14 patients (8%) and atrial fibrillation in 59 patients (36%). The median hospital and intensive care unit (ICU) lengths of stay were 3 [interquartile range (IQR): 1, 6] and 10 (IQR: 7, 17) days, respectively. The rate of type 1A endoleak was 3.6%, with the lowest rate in patients who underwent a total arch replacement with a hybrid FET graft (0%) and the highest among patients who had a hemiarch with antegrade thoracic endovascular aortic repair (TEVAR) deployment (25%). The rate of other types of endoleak and stent complications was comparatively low. The early CTAC experience with the FET operation demonstrates technical feasibility and good early clinical outcomes in elective and emergent patients. Further analysis is required to explore variations in technique and their potential impact on early and late outcomes.

WHAT HAPPENS TO THE AORTIC ROOT? A LONGITUDINAL STUDY OF AORTIC VALVE SPARING ROOT REPLACEMENTS

To evaluate the natural history of aortic root graft geometry, aortic valve competency and patient prognosis following a valve sparing aortic root reconstruction. Between 2008 and 2016, 65 consecutive patients (mean age 55.8±16.7yrs, 18.0% females) underwent elective and emergent valve sparing aortic root reconstruction. All patients were prospectively evaluated annually with clinical follow-up, echocardiography and CT imaging. Patients were assessed for survival, freedom from reoperation, degree of aortic regurgitation, NYHA status and graft complications over time. All echocardiograms and computed tomograms were read by single echocardiographer and radiologist, respectively. Patients were followed up to 8 years post-operatively (mean 25.4±285 months), with 100% follow-up. The largest increase of the aortic annulus observed during the surveillance period was 6.8±15.5% which occurred over the first 3 months of follow-up. Similarly, the aortic sinuses increased a maximal amount by 10.2±21.1% between the 1st and 2nd post-operative year. Afterwards, both of these components of the reconstruction remained stable through the remaining follow-up period. Both the sinotubular junction and ascending aorta remained stable, with a maximum annual increase of 5.6±5.5% and 5.7±8.2% respectively, for the first four post-operative years seen on CT imaging. The annual echocardiographic findings were similar but showed greater variability in the measurements as compared to CT. The overall survival rate was 93.4%(57 patients). Freedom from reoperation was 98.4%(60 patients). Throughout the entire duration of follow-up, aortic insufficiency was identified as 0 in 44(67.7%), 1+ in 17(26.2%), 2+ in 3(4.6%), 3+ in 0(0%) and 4+ in 1(1.5%). Mean NYHA status was 1.1±0.3 at most recent follow-up for all patients. CT evidence showed 96.5% (59 patients) freedom from graft complication including; endocarditis, thrombosis, embolism, aneurysm, pseudoaneurysm, dehisecence, dissection and kinking. This work demonstrates the stability of the aortic annulus and root following valve sparing aortic root reconstruction with comprehensive annual combined echocardiographic and CT imaging. We have shown that CT imaging on follow-up, more accurately demonstrated changes to the aortic root and its normal oval shaped geometry as compared to echocardiographic imaging for surveillance, whose 2D images assume a more round geometry. With the stability of the annulus and root as well as freedom from symptoms, aortic regurgitation and need for reintervention, annual surveillance of the valve reconstruction may not be necessary for all patients.

Outcomes of Elective Aortic Hemiarch Reconstruction for Aneurysmal Disease in the Elderly

This study evaluated outcomes of elective aortic hemiarch reconstruction for aneurysmal disease in the elderly. Patients undergoing elective aortic hemiarch reconstruction for aneurysmal disease at a single institution between 2009 and 2014 were retrospectively reviewed. Patients were stratified into nonelderly (aged less than 75 years) versus elderly (aged 75 years or more). Outcomes included operative mortality and morbidity. In all, 629 patients (95 elderly; 15%) were included. Elderly patients had a greater comorbidity burden. Concomitant aortic valve replacement and coronary artery bypass were performed more frequently whereas root replacement was performed less frequently in the elderly. The overall stroke rate was 1.8% and was higher among the elderly (4.2% versus 1.3%, p= 0.05), although this difference no longer persisted after risk adjustment (odds ratio 2.54, p= 0.17). Median length of intensive care unit and hospital stay were longer in the elderly (64 versus 41 hours and 9 versus 7 days, respectively; each p < 0.001). Unadjusted and risk-adjusted operative mortality were similar (2.1% elderly versus 0.9% nonelderly, p= 0.32). Elderly patients were less frequently discharged to home (65% versus 95%, p < 0.001). Propensity matched analysis confirmed these findings. Moderate hypothermic circulatory arrest with antegrade cerebral perfusion was a safe strategy for the elderly patients, with stroke and operative mortality rates of 0% each. Although elderly patients have a more prolonged recovery after elective aortic hemiarch reconstruction for aneurysmal disease, outcomes are acceptable with low operative mortality and with the majority being discharged home. Moderate hypothermic circulatory arrest with antegrade cerebral perfusion is a safe strategy for this cohort. Advanced age alone should not be viewed as a contraindication in these cases.

Three Factor Prothrombin Complex Concentrates in Cardiac Surgery: A Novel Algorithmic Approach to Perioperative Bleeding

Background: Three component prothrombin complex concentrates (PCCs) are currently approved to treat bleeding associated with Hemophilia B, and 4 component PCCs for warfarin reversal. They are increasingly used to treat bleeding in cardiac surgery patients. High dose PCC administration in the non-surgical setting has been associated with thrombotic complications, likely due to increased Factor II (Prothrombin) levels. We hypothesized that the use of low dose 3 factor PCCs (Profilnine, Grifols, CA) reduces bleeding following cardiopulmonary bypass without increasing the incidence of postoperative thrombotic complications.Methods: After IRB approval, a retrospective chart review of patients who underwent cardiac surgery and received Profilnine for refractory bleeding from February 2014 to February 2015. Demographic information, preoperative lab values, blood product use before and after PCC, use of rFVIIa, chest tube output and venous and arterial thromboembolic complications were collected. PCC was dosed according to an institutional perioperative bleeding algorithm (Figure 1) after approval by one of the senior authors (KG, JL or IW).Results: 114 patients received Profilnine¨ (Grifols, CA) for postoperative bleeding following cardiac surgery. The most common procedure that required PCC administration was elective aortic reconstruction (61, 57%) followed by acute aortic dissection (13, 12.1%). The mean dose of PCC was 15.8±7.1 IU. The chest tube output for the first hour after arriving in the ICU 150.8±214.0 ml and quickly decreased to 89.5±122.1 ml in the second hour. The mean total blood product transfusion was 12.4±9.9 units prior to PCC dose and 5±6.3 units post dose. The difference is represented in Figure 2 and was found to be statistically significant on a paired t-test. (p <0.0001). Only 4 patients (3.7%) of the patients had to return to the operating room for a re-exploration.Four patients (3.7%) had a cerebrovascular infarction in the postoperative period, of which two patients had undergone ventricular assist device (VAD) insertions, one had an aortic reconstruction and one had central ECMO cannulation performed following a STEMI. The patient with the aortic reconstruction received a higher dose of PCC (3000 Units or 33.5U/kg) and recombinant VIIa. One patient, who had a VAD inserted, had a pulmonary embolism. They received a low dose of PCC (13.8U/kg) did not receive factor VIIa. The post dose factor II activity level for this patient was 64%. Six patients (5.6%) had deep vein thrombosis diagnosed by venous doppler ultrasound. Four of these patients had received factor VIIa after PCC administration.Post dose prothrombin levels were measured in 20 patients, with a mean of 85.9%(±19.3%).The mean PCC dose in this group was 16.3 (±9.0) IU/kg per actual body weight, and 20.2 (±12.1) IU/kg per ideal body weight. Post dose factor II levels were plotted against PCC dose/kg in this group. The median factor II level was 87% (Figure 3). 12 out of these 20 patients received factor VIIa as part of the algorithm, and no postoperative thrombotic complications were reported in this subgroup.Conclusions: Our initial findings from this ongoing study revealed a reduction of total blood products transfused after administration of PCC compared to before administration. Our series is reporting a higher rate of thrombotic events. While some of these are associated with factor VIIa administration following the PCC dose, most are likely to be multifactorial in etiology and were well tolerated. Additional randomized studies are needed to determine the safety and efficacy of PCCs in cardiac surgical patients. [Display omitted] [Display omitted] [Display omitted] DisclosuresGhadimi:Portola Pharmaceuticals: Other: KG is a Co-Investigator in a prospective, open-label study of Andexanet Alfa in patients receiving factor Xa inhibitors with acute major bleeding, sponsored by Portola Pharmaceuticals . Levy:Boehringer Ingelheim: Consultancy; CSL Behring AG: Consultancy; Grifols: Consultancy; Janssen Pharmaceuticals: Consultancy; The Medicines Company: Consultancy. Welsby:NIH: Research Funding; Portola Pharmaceuticals: Research Funding; CSL Behring: Research Funding; Terumo BCT: Research Funding; Zimmer-Biomet: Other: non financial support.

The Impact of Deep Versus Moderate Hypothermia on Postoperative Kidney Function After Elective Aortic Hemiarch Repair

There remains concern that moderate hypothermic circulatory arrest (MHCA) with antegrade cerebral perfusion (ACP) may provide suboptimal distal organ protection compared with deep hypothermic circulatory arrest (DHCA) with retrograde cerebral perfusion (RCP). We compared postoperative acute kidney injury (AKI) in in patients who underwent elective hemiarch repair with either DHCA/RCP or MHCA/ACP. This was a retrospective review of all patients undergoing elective aortic hemiarch reconstruction for aneurysmal disease between 2009 and 2014. Patients were stratified according to the use of DHCA/RCP versus MHCA/ACP. The primary outcome was the occurrence of AKI at 48 hours, as defined by the Risk, Injury, Failure, Loss, End-Stage (RIFLE ) criteria. A multivariable logistic regression identified risk factors for AKI. One hundred eighteen patients who underwent ACP and 471 patients who underwent RCP were included. The mean lowest temperature was 26.4°C in patients who underwent MHCA/ACP and 17.5°C in patients who underwent DHCA/RCP. Baseline demographics were similar except that patients who underwent DHCA/RCP were more likely to have peripheral arterial disease or bicuspid aortic valves. Cardiopulmonary bypass and aortic cross-clamp times were shorter in the MHCA/ACP group. AKI occurred in 19 (16.2%) patients who underwent MHCA/ACP and 67 (14.3%) patients who underwent DHCA/RCP. Four(0.8%) patients who underwent DHCA/RCP required postoperative dialysis. In-hospital mortality tended to increase with increasing RIFLE classification (RIFLE class-0 (No AKI) = 0.41%; Risk = 1.35%, and Injury = 10.0%; p= 0.09). On multivariable analysis, the lowest temperature and cerebral perfusion strategy were not significant predictors of AKI. Lower baseline glomerular filtration rate (GFR), lower preoperative ejection fraction, and longer cardiopulmonary bypass (CPB) time were independently associated with higher AKI. We applied the sensitive RIFLE criteria to examine AKI in patients undergoing elective aortic hemiarch replacement for aneurysmal disease. Baseline renal dysfunction, lower ejection fraction, and longer CPB time are independent predictors of AKI. Compared with DHCA/RCP, our data suggest that an MHCA/ACP cerebral protection strategy does not appear to be associated with worse postoperative renal outcomes.

Use of human fibrinogen concentrate during proximal aortic reconstruction with deep hypothermic circulatory arrest

ObjectiveHuman fibrinogen concentrate (HFC) is approved by the Food and Drug Administration for use at 70 mg/kg to treat congenital afibrinogenemia. We sought to determine whether this dose of HFC increases fibrinogen levels in the setting of high-risk bleeding associated with aortic reconstruction and deep hypothermic circulatory arrest (DHCA). MethodsThis was a prospective, pilot, off-label study in which 22 patients undergoing elective proximal aortic reconstruction with DHCA were administered 70 mg/kg HFC upon separation from cardiopulmonary bypass (CPB). Fibrinogen levels were measured at baseline, just before, and 10 minutes after HFC administration, on skin closure, and the day after surgery. The primary study outcome was the difference in fibrinogen level immediately after separation from CPB, when HFC was administered, and the fibrinogen level 10 minutes following HFC administration. Additionally, postoperative thromboembolic events were assessed as a safety analysis. ResultsThe mean baseline fibrinogen level was 317 ± 49 mg/dL and fell to 235 ± 39 mg/dL just before separation from CPB. After HFC administration, the fibrinogen level rose to 331 ± 41 mg/dL (P < .001) and averaged 372 ± 45 mg/dL the next day. No postoperative thromboembolic complications occurred. ConclusionsAdministration of 70 mg/kg HFC upon separation from CPB raises fibrinogen levels by approximately 100 mg/dL without an apparent increase in thrombotic complications during proximal aortic reconstruction with DHCA. Further prospective study in a larger cohort of patients will be needed to definitively determine the safety and evaluate the efficacy of HFC as a hemostatic adjunct during these procedures.

PC84. Inferior Mesenteric Artery Reimplantation During Aortic Aneurysm Surgery

The role of inferior mesenteric artery (IMA) reimplantation (IMAR) during open aortic reconstruction is debated. We assessed outcomes following IMAR for aortic aneurysmal disease to help shed light on this question. Single-center retrospective review was done of all IMARs performed during open aortic surgery over a 10-year period between 2000 and 2009. Of 840 elective aortic aneurysmal reconstructions performed during this period, 70 underwent IMAR. Indications for IMAR included intraoperative colonic ischemia (n = 24), poor back bleeding (n = 52), large IMA (n = 5), internal iliac disease (n = 5), and prior colon surgery (n = 1). Follow-up imaging studies were available in 35 of 70 patients (computed tomography in 30 [86%] and duplex in 5 [14%]). Primary outcome was patency, while secondary outcomes included colonic ischemia and overall survival. Analysis was performed using Cox models and Kaplan-Meier estimates. Patency was confirmed in 32 of 35 patients (91%) over a median follow-up of 98 months. Both losses in patency were at 4 months and did not require an operation. One patient underwent left colon resection on postoperative day 9 due to ischemia (patency could not be confirmed). No statistically significant predictor of patency was noted. Incidence of colonic ischemia was 1.4% in patients undergoing IMAR. Incidence of colonic ischemia in patients without indications for IMAR was 0.26%. Overall mortality was 51% in patients undergoing IMAR over the median follow-up period. Nature of aneurysm (juxtarenal or higher [JRAAA]) was a predictor of mortality, with a hazard ratio (HR) of 1.8 (P = .08). Ten-year survival was worse if IMAR was performed for intraoperative colonic ischemia (26% vs 34%) or in JRAAA (19.0% vs 38%). Overall 10-year survival was 30% in patients undergoing IMAR for aortic aneurysmal disease. Age per year was the only statistically significant predictor of survival (P < .001). Inferior mesenteric artery reimplantation for aortic aneurysmal disease is indicated in select patients. Reimplantation is associated with excellent long-term patency, low risk of colonic ischemia, and minimal risk of surgical reintervention.

Moderate Versus Deep Hypothermic Circulatory Arrest for Elective Aortic Transverse Hemiarch Reconstruction

Deep hypothermic circulatory arrest (DHCA) with retrograde cerebral perfusion (DHCA group) has traditionally been the cerebral protection strategy during transverse hemiarch aortic reconstruction. Recently, we have adopted moderate hypothermic (≥ 25 °C) circulatory arrest (MHCA) with antegrade cerebral perfusion (MHCA group). We compared the outcomes for these two circulatory arrest management strategies. From 2008 to 2012, in a concurrent series of 376 patients (DHCA, 301; MHCA, 75) undergoing transverse hemiarch for aortic aneurysm disease, incidences of concomitant root replacement (44% vs 47%, p = 0.8), and aortic valve replacement (29% vs 21%, p = 0.3) were similar, although atherosclerotic aneurysm pathology was present in patients in the MHCA group (71% vs 33%, p < 0.01). Antegrade cerebral perfusion was established via axillary artery or direct innominate artery cannulation. A database was prospectively maintained. MHCA group patients were older (66 ± 11 vs 60 ± 14 years; p < 0.01). Other demographics were similar. Aortic cross-clamp (128 ± 46 vs 163 ± 57 minutes, p < 0.01) and cardiopulmonary bypass (167 ± 49 vs 222 ± 61 minutes, p < 0.01) times were lower in the MHCA group. Transfusion requirements were significantly reduced with MHCA (38% vs 61%, p < 0.01), especially use of fresh frozen plasma and cryoprecipitate. Direct innominate artery cannulation did not result in any vascular or neurologic complication. Postoperative outcomes were similar. In-hospital and 30-day mortality was 1% in both groups. Stroke (0% vs 2%) and hemodialysis rates (0% vs 1%) were also similar. MHCA with antegrade cerebral perfusion yields excellent and equivalent outcomes to DHCA for elective aortic hemiarch reconstruction. MHCA significantly improves intraoperative times and, importantly, reduces transfusion requirements compared with DHCA with a retrograde cerebral perfusion strategy.

Antibiotic-Impregnated Grafts for Aortic Reconstruction

An infected aorta, or aortic graft, is a challenge to manage. Extra-anatomical bypass followed by resection of the infected aorta has been considered standard practice. Outcomes are far from ideal and anatomical constraints make this impossible at the visceral and thoracic aorta. In situ aortic repair is an alternative and can be accomplished in most cases. Use of this technique has been tempered by concerns of graft durability and reinfection. In vitro and in vivo laboratory experiments have demonstrated antibiotics can be bound to polytetrafluoroethylene and Dacron aortic grafts. In animal models, antibiotic-soaked grafts were resistant to infection when seeded with an intravenous bacteria challenge. Purulent, infected aortic grafts created in animal models by direct bacteria inoculation could be successfully replaced in situ with infection-resistant antibiotic-soaked Dacron grafts. The antibiotic of choice is rifampin, which readily binds to commercially available, off-the-shelf gelatin- or collagen-impregnated Dacron. In humans, rifampin-soaked Dacron has not only been used to reconstruct the aorta in the face of infection, but also in elective aortic reconstruction as a prophylaxis against future infection. Outcomes from case series are difficult to interpret because of the heterogeneous nature of patients presenting with aortic infections. Thirty-day mortality ranges from 7% to 21% and morbidity from 2% to 60%. Amputations are rarely seen in these cases, but are common in extra-anatomical bypass from graft occlusion. Reinfection of the rifampin grafts are seen in 4% to 22% of patients, and 5-year survival is near 50%. In the future, the utility of rifampin-soaked Dacron will have to be tested against the emergence of antibiotic-resistant bacteria. Improvements in alternative conduits, such as cryopreserved aortic grafts, may diminish the use of antibiotic-soaked grafts, but it will remain a useful tool in the vascular surgeon's armamentarium.

Investigation of Systemic and Mesenteric Inflammatory Signaling and Gut-Derived Endothelial Toxicity in Patients Undergoing High-Risk Abdominal Aortic Surgery

Evidence from animal models of trauma and hemorrhage has suggested that the gut plays an active role in the pathogenesis of systemic inflammatory responses and multiple organ dysfunction syndrome. The aim of the present study was to seek evidence for gut-derived signals in man in a group of eight patients undergoing elective abdominal aortic reconstruction, a procedure that is associated with sterile tissue injury, controlled colonic ischemia as a consequence of aortic cross-clamping, and a significant risk of developing systemic inflammation and multiple organ dysfunction syndrome. Despite the presence of a marked systemic inflammatory response (IL-6, IL-18, monocyte chemoattractant protein 1, and IL-8) and a gut-derived inflammatory signal (IL-6), we could find no evidence that gut-derived pathogen DNA was present in the central or mesenteric circulation, and we could find no evidence that either central or mesenteric plasma samples could induce apoptotic or necrotic cell death in human umbilical vein endothelial cells in vitro. Similarly, we could find no evidence of adhesion molecule upregulation in the endothelial monolayers exposed to central or mesenteric plasma sampled at any time point during surgery. There was, however, evidence of an increase in the expression of RAGE (receptor for advanced glycation end products) by endothelial cells following exposure to mesenteric venous, but not central, plasma sampled during maximum ischemia. In conclusion, during sterile tissue injury and controlled colonic ischemia-reperfusion in man, there is a marked systemic proinflammatory response, which is in part gut derived, in the absence of evidence for the presence of toxic endothelial factors or gut-derived microorganisms in the central or mesenteric circulations.

Improved Accuracy Of Cardiac Output Estimation By The Partial CO2 Rebreathing Method

This study investigated the accuracy of the NICO monitor equipped with the newer software. Additionally, the effects of the increased dead space produced by the NICO monitor on ventilatory settings were investigated. Forty-two patients undergoing elective aortic reconstruction participated in this prospective, observational study at a university hospital. Cardiac output was continuously monitored using both the NICO monitor and continuous cardiac output (CCO) measured by a pulmonary artery catheter. A NICO monitor equipped with ver. 4.2 software was used for the first 21 patients while a NICO monitor equipped with ver. 5.0 software was used for the rest of the patients. Cardiac output measured by bolus thermodilution (BCO) at 30 min intervals was used as a reference. The bias +/- precision of the NICO monitor was 0.18 +/- 0.88 l/min with ver. 4.2 software (n = 182) and 0.18 +/- 0.83 l/min with 5.0 software (n = 194). The accuracy of the NICO monitor is comparable to CCO, whose bias +/- precision against BCO is 0.19 +/- 0.81 l/min (n = 376). At the same level of CO(2) production and minute ventilation, PaCO(2) was lower in the patients monitored by NICO with ver. 5.0 software than patients with ver. 4.2 software. This study demonstrated the improved performance of the NICO monitor with updated software. The performance of the NICO monitor with ver. 4.2 or later software is similar to CCO. However, the cardiac output measurement did not fulfill the criteria of interchangeability to the cardiac output measurement by bolus thermodilution. Updates to ver. 5.0 attenuated the effects of rebreathing introduced by the NICO monitor without compromising the accuracy of the cardiac output measurement.

A Persistent Left Superior Vena Cava: Erroneous Measurement of Cardiac Output

To the Editor: Placement of a pulmonary artery catheter (PAC) through a persistent left superior vena cava (PLSVC) may lead to erroneous cardiac output (CO) measurements. We report a 42-yr-old male who was scheduled for elective aortic valve reconstruction. After induction of anesthesia, a PAC was placed without difficulty and obviously in a correct distal position as confirmed by pressure recording (at 60 cm). However, pulmonary artery thermodilution measurement revealed a double-hump suggesting a shunt phenomenon (Fig. 1A).Figure 1.: (A) Thermodilution curves with a double-hump as obtained with the injection site of the pulmonary artery catheter in the coronary sinus. (B) Thermodilution curves without a double-hump as obtained after repositioning of the pulmonary artery catheter with a correct injection site in the right atrium.The PAC was retracted prior to cardiopulmonary bypass and re-advanced (at 65 cm) after successful weaning. The thermodilution curve then did not show a double-hump shape and CO was more than doubled (8.6 L min−1) (Fig. 1B). A postoperative chest radiograph (Fig. 2A) and computed tomography scan (Fig. 2B) revealed the PAC in a PLSVC.Figure 2.: (A) Chest radiograph showing a persistent left superior vena cava (PLSVC). Arrow head = tip of the pulmonary artery catheter, arrow = central venous catheter. (B) Chest computed tomography scan showing the position of the pulmonary artery catheter through the coronary sinus (indicated by the arrow). Arrow head = persistent left superior vena cava (PLSVC).In general, a PLSVC, being the most common thoracic venous anomaly (0.5%), is of no pathological consequence (1). In up to 92% of cases, the PLSVC drains into the right atrium through the coronary sinus (2) and patients with a PLSVC have an increased risk for atrial fibrillation due to bilateral pacemaker areas in the myocardium (3). Measurement of CO by the thermodilution technique is based on the Stewart–Hamilton principle: CO = m0/AUC Δt dt (m0 = mass of the indicator injected, AUC = area under the temperature curve). Whenever the AUC is increased (here by “re-circulation”) while keeping the amount of indicator injected unchanged, CO will be under-estimated. In our case, cold saline was injected into the coronary sinus yielding a pulmonary artery thermodilution curve with a double-hump which is similar to one observable in left-to-right shunt during which the pulmonary artery thermodilution curve is typically prolonged. Since a part of the indicator that has already passed the tip of the PAC re-circulates, a second, but less pronounced, decrease in temperature appears (4). In our patient, an intracardiac shunt could be excluded by echocardiography. Therefore, “re-circulation” from the coronary sinus into the right atrium was the cause of the described double-hump phenomenon. Consequently, the first AUC was artificially elevated, explaining the underestimation of CO. Re-positioning of the PAC to an increased insertion depth of about 65 cm resulted in a correct right atrial injection site, and a higher CO was measured without the “double-hump” phenomenon. In summary, a PAC advanced through a PLSVC may cause erroneous measurements of CO and particular attention has to be paid to the shape of the thermodilution curve in this setting. Wolfram Schummer, MD Claudia Schummer, MD Samir G.Sakka, MD, PhD Department of Anesthesiology and Intensive Care Medicine Friedrich-Schiller-University of Jena D-07740 Jena, Germany [email protected]

Preoperative clinical evaluation as a predictor of cardiac complications after infrarenal aortic reconstruction

This paper analyses cardiac risk factors in 93 consecutive patients undergoing elective infrarenal aortic reconstruction over a 2 year period. During the perioperative or postoperative period, 26 patients sustained a total of 42 cardiac complications. Eight patients had myocardial infarction, 14 left ventricular failure and 15 arrhythmias. There were five cardiac-related deaths. Angina was the only statistically significant risk factor in predicting postoperative cardiac problems. A multivariate analysis identified a high-risk group of patients in whom cardiac complications after operation were common.

Myocardial infarction after reconstruction of the abdominal aorta.

The records of 555 patients who underwent elective abdominal aortic reconstruction were analysed to identify risk factors predisposing to cardiac complications. Perioperative myocardial infarction occurred in 35 patients (6.3 per cent), of whom 12 (2.2 per cent) died. Using multiple logistic regression, four preoperative factors that were independently predictive for postoperative myocardial infarction were identified with the following relative risk ratios: history of transient ischaemic attacks, 5.08; raised serum creatinine level, 3.66; age > 60 years, 3.00; and angina requiring regular treatment, 2.74. A scoring system using these four factors was devised that identified 150 of the 555 patients as at high risk, and included 69 per cent of those with myocardial infarction after operation and 83 per cent of those who died. A clinical risk score is a practical first step in identifying patients at risk of myocardial infarction; it would also reduce the number of patients for whom sophisticated tests of cardiac function were necessary.

Autotransfusion in aortic surgery: the Haemocell System 350 cell saver.

Autotransfusion was performed during elective abdominal aortic reconstruction in ten patients using the recently developed Haemocell System 350. A mean of 60 per cent of total blood loss was salvaged, and during operation each patient was autotransfused 1 unit. Good preservation of cellular components, including platelets, was seen after processing with the device, which uses a vortex mixing filter for cell separation. There was no evidence of coagulopathy; mean free plasma haemoglobin levels were slightly raised (17 mg/dl) and plasma heparin concentration was negligible (0.10 units/ml) 4 h after surgery. A transient drop in plasma fibrinogen levels and the appearance of fibrin degradation products in low concentrations (mean 1.5 mg/l) were seen. Oxyhaemoglobin dissociation curves showed the salvaged red blood cells to have a normal affinity for oxygen. Renal and hepatic function remained unaltered and there were no complications attributable to autotransfusion. The device was easy to handle and a trained operator was not required.

Reply

We thank the readers for their comments, and we were very interested to see that they have obtained a similar incidence of cTnI elevation in 29% of patients after elective open aortic reconstruction at a unit that did not perform endovascular abdominal aortic aneurysm repair at the time. This, in our opinion, would confirm our results that there is a statistically and almost certainly clinically significant difference in the incidence of subclinical myocardial damage after the two types of infrarenal abdominal aortic aneurysm repair. In our two groups of patients, the preoperative management did not include routine β-blockade and statin therapy. Although this was not prospectively documented, medical optimization was more likely to have taken place in the open group in view of the degree of severity of the planned procedure. It is quite unlikely that medical optimization would have contributed to the reduction in myocardial injury associated with endovascular repair. Our study protocol, as approved by the local ethics committee, dictated analysis of all samples in batches in a way that was not related to the day-to-day management of the individual patient. This was to avoid unnecessary interventions based on the results of a serum analysis that under normal circumstances would not take place according to the best current practice of that time, because troponin measurement is not a routine part of postoperative patient care. Regarding “A prospective study of subclinical myocardial damage in endovascular versus open repair of infrarenal abdominal aortic aneurysms”Journal of Vascular SurgeryVol. 42Issue 3PreviewWe read with interest the article by Abraham et al (J Vasc Surg 2005;41:377-81) reporting increased levels of cardiac troponin (cTn) T in 9% of patients after elective endovascular repair and 25% of patients after elective open repair of infrarenal abdominal aortic aneurysm. These findings are similar to our own, in which increased levels of cTnI were detected in 10 (29%) of 35 patients after elective open aortic reconstruction.1 Because our study was performed in a unit that did not perform endovascular abdominal aortic aneurysm repair at the time, it seems unlikely that the authors’ suggestion that institutional unfamiliarity with open aortic surgery, or more advanced arterial disease in patients unsuitable for endovascular repair, can adequately explain the higher incidence of myocardial injury in the open repair group. Full-Text PDF Open Archive