Lars Englberger

Clinical accuracy of RIFLE and Acute Kidney Injury Network (AKIN) criteria for acute kidney injury in patients undergoing cardiac surgery

IntroductionThe RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification for acute kidney injury (AKI) was recently modified by the Acute Kidney Injury Network (AKIN). The two definition systems differ in several aspects, and it is not clearly determined which has the better clinical accuracy.MethodsIn a retrospective observational study we investigated 4,836 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass from 2005 to 2007 at Mayo Clinic, Rochester, MN, USA. AKI was defined by RIFLE and AKIN criteria.ResultsSignificantly more patients were diagnosed as AKI by AKIN (26.3%) than by RIFLE (18.9%) criteria (P < 0.0001). Both definitions showed excellent association to outcome variables with worse outcome by increased severity of AKI (P < 0.001, all variables). Mortality was increased with an odds ratio (OR) of 4.5 (95% CI 3.6 to 5.6) for one class increase by RIFLE and an OR of 5.3 (95% CI 4.3 to 6.6) for one stage increase by AKIN. The multivariate model showed lower predictive ability of RIFLE for mortality. Patients classified as AKI in one but not in the other definition set were predominantly staged in the lowest AKI severity class (9.6% of patients in AKIN stage 1, 2.3% of patients in RIFLE class R). Potential misclassification of AKI is higher in AKIN, which is related to moving the 48-hour diagnostic window applied in AKIN criteria only. The greatest disagreement between both definition sets could be detected in patients with initial postoperative decrease of serum creatinine.ConclusionsModification of RIFLE by staging of all patients with acute renal replacement therapy (RRT) in the failure class F may improve predictive value. AKIN applied in patients undergoing cardiac surgery without correction of serum creatinine for fluid balance may lead to over-diagnosis of AKI (poor positive predictive value). Balancing limitations of both definition sets of AKI, we suggest application of the RIFLE criteria in patients undergoing cardiac surgery.

Minimizing aortic manipulation during OPCAB using the symmetry aortic connector system for proximal vein graft anastomoses.

BACKGROUND Since minimal invasive techniques have become increasingly common in coronary artery bypass grafting (CABG), there has been renewed interest in facilitated mechanical anastomoses devices that might have the potential of replacing the standard suturing techniques in vascular anastomoses. We report our initial experience with the successful creation of mechanical proximal vein graft anastomoses in off-pump coronary artery bypass operations. METHODS From August to December 2000, we investigated the first 20 consecutive patients who underwent CABG on the beating heart without extracorporeal circulation and who received at least one mechanical proximal vein graft anastomosis with the St. Jude Medical Symmetry aortic connector system without side-clamping of the aorta. We evaluated the different components of the system, the feasibility of such anastomoses, and the intraoperative flow measurements of the grafts using transit time methods. RESULTS A total of 32 proximal vein graft anastomoses were performed with the aortic connector system. Hemostasis was instantaneous in all cases except one, in which the connector was removed and the anastomosis was hand-sewn without complications. All other vein grafts were patent at the end of the procedure; intraoperative flow measurements were 39 +/- 25 mL/min for single vein grafts (n = 20) and 69 +/- 25 mL/min for sequential grafts (n = 11). CONCLUSIONS The St. Jude Medical Symmetry aortic connector system is a user-friendly, effective, quick, and reliable device for sutureless proximal vein graft anastomosis in CABG. This system allows the construction of uniform and geometrically perfect anastomoses and does not require aortic side-biting. This technology is attractive for all CABG procedures because aortic manipulation is reduced. In off-pump surgical procedures the connector system allows aortic manipulation to be minimized, potentially reducing embolization from aortic wall debris.

Ten-year comparison of pericardial tissue valves versus mechanical prostheses for aortic valve replacement in patients younger than 60 years of age.

OBJECTIVE Aortic valve replacement using a tissue valve is controversial for patients younger than 60 years old. The long-term survival in this age group, the expected event rates during long-term follow-up, and valve-related complications are not clearly determined. METHODS From January 2000 to December 2009, overall survival, valve-related events, and echocardiographic outcomes were analyzed in all patients younger than 60 years of age, who underwent biologic aortic valve replacement. Patients who received a Perimount Carpentier-Edwards pericardial tissue valve (n = 103) were selected and compared with a propensity matched group of 103 patients who received aortic valve replacement using a mechanical bileaflet valve. The mean follow-up was 33 ± 24 months (range, 2-120), and the mean age at implantation was 50.6 ± 8.8 years (bioprosthesis, 55 ± 8.9 years; mechanical valve, 50 ± 8.6 years; P = .03). RESULTS Survival was significantly reduced in patients after biologic aortic valve replacement (90.3% vs 98%; P = .038). Freedom from all valve-related complications (bioprosthesis, 54.5%; mechanical valve, 51.6%; P = NS) and freedom from reoperation (bioprostheses, 100%; mechanical valve, 98%; P = NS) were comparable in both groups. The average transvalvular mean (11.2 ± 4.2 mm Hg vs 10.5 ± 6.0 mm Hg, P = .05) and peak (19.9 ± 6.7 mm Hg vs 16.7 ± 8.0 mm Hg, P = .03) gradients were greater after biologic aortic valve replacement. Regression of the left ventricular mass index was more pronounced after mechanical valve replacement (118.5 ± 24.9 g/m(2) vs 126.5 ± 38.5 g/m(2); P = NS). The echocardiographic patient-prosthesis mismatch was greater at follow-up after biological aortic valve replacement (0.876 ± 0.2 cm(2)/m(2) vs 1.11 ± 0.4 cm(2)/m(2); P = .01). Oral anticoagulation was a protective factor for survival among the bioprosthetic valve patients (P = .024). CONCLUSIONS In the present limited cohort of patients younger than 60 years old, biologic aortic valve replacement was associated with reduced mid-term survival compared with survival after mechanical aortic valve replacement. Despite similar valve-related event rates in both groups, the better hemodynamic performance of the mechanical valves and/or protective effect of oral anticoagulation seemed to improve the outcome. The transcatheter valve-in-valve intervention as potential treatment of tissue valve degeneration should not be considered the sole bailout strategy for younger patients because no evidence is available that this would improve the outcome.

Validation of Clinical Scores Predicting Severe Acute Kidney Injury After Cardiac Surgery

BACKGROUND Acute kidney injury (AKI) requiring renal replacement therapy (RRT) in patients undergoing cardiac surgery is associated strongly with adverse patient outcomes. Recently, 3 predictive risk models for RRT have been developed. The aims of our study are to validate the predictive scoring models for patients requiring postoperative RRT and test applicability to the broader spectrum of patients with postoperative severe AKI. STUDY DESIGN Diagnostic test study. SETTING & PARTICIPANTS 12,096 patients undergoing cardiac surgery with cardiopulmonary bypass at Mayo Clinic, Rochester, MN, from 2000 through 2007. INDEX TEST Cleveland Clinic score, Mehta score, and Simplified Renal Index (SRI) score. REFERENCE TEST OR OUTCOME Incidence of postoperative RRT or composite outcome of severe AKI, defined as serum creatinine level >2.0 mg/dL, and a 2-fold increase compared with the preoperative baseline creatinine level or RRT. RESULTS RRT was used in 254 (2.1%) patients, whereas severe AKI was present in 467 (3.9%). Discrimination for the prediction of RRT and severe AKI was good for all scoring models measured using areas under the receiver operating characteristic curve (AUROCs): 0.86 (95% CI, 0.84-0.88) for RRT and 0.81 (95% CI, 0.79-0.83) for severe AKI using the Cleveland score, 0.81 (95% CI, 0.78-0.86) and 0.76 (95% CI, 0.73-0.80) using the Mehta score, and 0.79 (95% CI, 0.77-0.82) and 0.75 (95% CI, 0.72-0.77) using the SRI score. The Cleveland score and Mehta score consistently showed significantly better discrimination compared with the SRI score (P < 0.001). Despite lower AUROCs for the prediction of severe AKI, the Cleveland score AUROC was still >0.80. The Mehta score is applicable in only a subgroup of patients. LIMITATIONS Single-center retrospective cohort study. CONCLUSIONS The Cleveland scoring system offers the best discriminative value to predict postoperative RRT and covers most patients undergoing cardiac surgery. It also can be used for prediction of the composite end point of severe AKI, which enables broader application to patients at risk of postoperative kidney dysfunction.

Arterial access through the right subclavian artery in surgery of the aortic arch improves neurologic outcome and mid-term quality of life

BACKGROUND We have shown that selective antegrade cerebral perfusion improves mid-term quality of life in patients undergoing surgical repair for acute type A aortic dissection and aortic aneurysms. The aim of the study was to assess the impact of continuous cerebral perfusion through the right subclavian artery on immediate outcome and quality of life. METHODS Perioperative data of 567 consecutive patients who underwent surgery of the aortic arch using deep hypothermic circulatory arrest have been analyzed. Patients were divided into three groups, according to the management of cerebral protection. Three hundred eighty-seven patients (68.3%) had deep hypothermic circulatory arrest with pharmacologic protection with pentothal only, 91 (16.0%) had selective antegrade cerebral perfusion and pentothal, and 89 (15.7%) had continuous cerebral perfusion through the right subclavian artery and pentothal. All in-hospital data were assessed, and quality of life was analyzed prospectively 2.4 +/- 1.2 years after surgery with the Short Form-36 Health Survey Questionnaire. RESULTS Major perioperative cerebrovascular injuries were observed in 1.1% of the patients with continuous cerebral perfusion through the right subclavian artery, compared with 9.8% with selective antegrade cerebral perfusion (p < 0.001) and 6.5% in the group with no antegrade cerebral perfusion (p = 0.007). Average quality of life after an arrest time between 30 and 50 minutes with continuous cerebral perfusion through the right subclavian artery was significantly better than selective antegrade cerebral perfusion (90.2 +/- 12.1 versus 74.4 +/- 40.7; p = 0.015). CONCLUSIONS Continuous cerebral perfusion through the right subclavian artery improves considerably perioperative brain protection during deep hypothermic circulatory arrest. Irreversible perioperative neurologic complications can be significantly reduced and duration of deep hypothermic circulatory arrest can be extended up to 50 minutes without impairment in quality of life.

Pitfalls and key lessons with the symmetry proximal anastomotic device in coronary artery bypass surgery.

BACKGROUND Increasing practice of less-invasive coronary artery bypass surgery has generated a revival of automated methods to facilitate the creation of vascular connections during coronary artery bypass grafting procedures. METHODS We have reviewed our clinical experience with 107 patients who received at least one proximal Symmetry aortic connector from St. Jude Medical Anastomotic Technology Group (St. Paul, MN) to connect a saphenous vein graft to the ascending aorta, in whom the minimal follow-up is 6 months. Seventy-five patients were part of an observational study, and 32 patients were enrolled in a prospective randomized study to compare the anastomotic device with the conventional suture technique. Key lessons and pitfalls observed during loading and deployment as well angiographic findings are presented. RESULTS Hospital mortality was 0.9% (1/107); a 76-year-old woman suffered from cerebral complications and died after combined coronary artery bypass grafting and aortic valve replacement. Two connectors had to be removed because of leakage and one because of incomplete deployment. The residual 104 grafts connected to the ascending aorta were patent at the end of the operation (mean flow, 72 +/- 29 mL/min). Fourteen patients from the prospective study have received 6 months of angiographic assessment so far. Forty-two grafts have been evaluated: all IMA grafts (n = 14) are patent. Four radial artery grafts have been studied: three are patent and one is occluded. Twenty-four vein grafts have been assessed: 11 were hand-sewn and 13 were connected to the aorta with the proximal connector system. Patency rate is not different between the two techniques, but there is an incidence of 38% (5/13) stenosis in the proximal vein graft segment in those patients with a proximal connector. No proximal hand-sewn anastomosis shows any significant stenosis. CONCLUSIONS The use of proximal devices allows ultrafast connection of a bypass graft to the aorta. The handling of this device is simple, manipulations on the ascending aorta are minimized, and hemostasis is perfect. However, because stenoses have been observed in the vein graft close to the connector site, mid- and long-term patency rates have to be assessed in large prospective trials.

Deep hypothermic circulatory arrest is not a risk factor for acute kidney injury in thoracic aortic surgery.

OBJECTIVE Previous studies describe a high incidence of acute kidney injury after open thoracic aortic surgery. Findings may be confounded by patient selection, including surgery with deep hypothermic circulatory arrest only or emergency procedures. We studied incidence and risk factors of acute kidney injury in patients undergoing thoracic aortic surgery. METHODS We reviewed 851 patients undergoing elective thoracic aortic surgery with and without deep hypothermic circulatory arrest between 2000 and 2007, focusing on clinical outcome and acute kidney injury defined by consensus RIFLE (Risk, Injury, Failure, Loss of function, End-stage renal disease) criteria. RESULTS Mean age was 59±16 years; 29% were women. Surgical procedures included aortic root or ascending aorta in 817 patients (96%), aortic arch in 172 (20%), and descending thoracic aorta in 54 (6%), with 20% reoperative procedures. Deep hypothermic circulatory arrest was used in 238 (28%). Incidence of postoperative acute kidney injury (all RIFLE classes) was 17.7%; 2.1% required renal replacement therapy. Mortality increased with RIFLE class severity of acute kidney injury (P<.001). Independent risk factors for acute kidney injury were increased age, elevated body mass index, hypertension, impaired left ventricular ejection fraction, preoperative anemia, and cardiopulmonary bypass duration. Deep hypothermic circulatory arrest, aprotinin use, and preoperative creatinine level were not independently associated with acute kidney injury. CONCLUSIONS Thoracic aortic surgery can be performed with low rates of acute kidney injury, comparable to other cardiac surgical procedures. Deep hypothermic circulatory arrest and preoperative serum creatinine are not independent risk factors. RIFLE criteria allow comparison with previous studies and correlate well with patient outcome. Risk estimates for acute kidney injury require multivariable prediction.

Mortality and neurologic injury after surgical repair with hypothermic circulatory arrest in acute and chronic proximal thoracic aortic pathology: effect of age on outcome.

Background— The goal of this study was to determine whether advanced age affects mortality and incidence of neurological injury in patients undergoing surgical repair with hypothermic circulatory arrest in acute and chronic thoracic aortic pathology. Methods and Results— A university center audit was done of 523 consecutive patients (median age, 64 years; interquartile range, 56–71 years) between 2005 and 2010. Mortality in acute type A aortic dissection (207 patients) was 9.7%, and in chronic ascending aortic aneurysms (316 patients) was 2.2% (P<0.001). Neurological injury was observed in 16.9% of patients with acute type A aortic dissection (chronic ascending aortic aneurysms, 7.9%; P=0.002). Multivariable regression analysis revealed hypothermic circulatory arrest >40 minutes (odds ratio [OR], 4.21; 95% confidence interval [CI], 1.60–11.06; P=0.004) and redo surgery (OR, 3.44; 95% CI, 1.11–10.64; P=0.03) but not age (OR, 1.98; 95% CI, 0.73–5.38; P=0.18) as independent predictor of mortality. Emergency surgery (OR, 3.27; 95% CI, 1.31–8.15; P=0.01) and extracardiac arteriopathy (OR, 2.38; 95% CI, 1.26–4.50; P=0.008) but not age (OR, 1.80; 95% CI, 0.93–3.48; P=0.08) were independent predictors of neurological injury. Conclusions— Age is not associated with increased risk for mortality and neurological injury in patients undergoing surgical repair for acute and chronic thoracic aortic pathology with hypothermic circulatory arrest. Extended hypothermic circulatory arrest times, reflecting the extent of disease, and redo surgery predict mortality, whereas emergency surgery and extracardiac arteriopathy predict neurological injury.

Aprotinin reduces blood loss in off-pump coronary artery bypass (OPCAB) surgery

OBJECTIVE Effects of aprotinin in off-pump coronary artery bypass (OPCAB) surgery have not yet been described. This study analyses hemostasiologic changes and potential benefit in OPCAB patients treated with aprotinin. METHODS In a prospective, double-blind, randomized study 47 patients undergoing OPCAB surgery were investigated. Patients received either aprotinin (2 x 10(6) KIU loading dose and 0.5 x 10(6) KIU/h during surgery, n=22) or saline solution (control, n=25). Activated clotting time was adjusted to a target of 250 s intraoperatively. Blood samples were taken up to 18h postoperatively: complete hematologic and hemostasiologic parameters including fibrinopeptide A (FPA) and D-dimer in a subgroup of 31 patients were analyzed. Blood loss, blood transfusion and other clinical data were collected. RESULTS Both groups showed comparable demographic and intraoperative variables. Forty-one (87%) patients of the whole study group received aspirin within 7 days prior to surgery. Number of grafts per patient were comparable (2.9+/-1.0 [mean+/-SD] in the aprotinin group and 2.8+/-1.2 in control, P=0.83). Blood loss during the first 18 h in intensive care unit was significantly reduced in patients treated with aprotinin (median [25th-75th percentiles]: 500 [395-755] ml vs. 930 [800-1170] ml, P<0.001). Postoperatively only two patients (10%) in the aprotinin group received packed red blood cells, whereas eight (35%) in the control group (P=0.07). Perioperatively FPA levels reflecting thrombin generation were elevated in both groups. The increase in D-dimer levels after surgery was significantly inhibited in the aprotinin group (P<0.001). Early clinical outcome was similar in both groups. CONCLUSIONS Aprotinin significantly reduces blood loss in patients undergoing OPCAB surgery. Inhibition of enhanced fibrinolysis can be observed. FPA generation during and after OPCAB surgery seems not to be influenced by aprotinin.

Clinical experience with the second-generation 3f Enable sutureless aortic valve prosthesis

OBJECTIVE The 3f Enable aortic bioprosthesis (ATS Medical, Inc, Minneapolis, Minn) represents a new generation of equine pericardial self-expanding valve designed for sutureless implantation. This study evaluated technical aspects of implantation and safety and effectiveness of the valve in the short term. METHODS In an outcome analysis of a consecutive series of 28 patients who underwent aortic valve replacement for aortic stenosis with the 3f Enable during an 18-month period, mean age was 75.7 +/- 6.6 years, 18 patients were female (64.2%), and mean EuroSCORE was 7.1% +/- 1.7%. RESULTS Most implanted valves were 23 mm in diameter (19-27 mm). Mean aortic crossclamp time was 39 +/- 15 minutes (29-103 minutes), mean cardiopulmonary bypass time was 58 +/- 20 minutes (41-127 minutes), mean hospital stay was 11 days (7-22 days), and 30-day mortality was 3.5%. Mean and peak intraoperative transvalvular pressure gradients were 6.1 +/- 2.6 and 18 +/- 5 mm Hg, respectively. Trivial and mild paravalvular leaks were observed in 1 patient each. One patient underwent reoperative aortic valve replacement 4 months after initial surgery for severe valve-unrelated paravalvular leakage. Five patients (18.5%) required permanent pacemakers. No patients were unavailable for follow-up. One-year survival was 86.2%. CONCLUSIONS The 3-f Enable aortic bioprosthesis can be implanted safely with favorable early hemodynamics. The self-expanding stent allows sutureless implantation with a large valve area. The procedure was fast, although not as fast as expected. This experience has led to continued design and procedural enhancements to facilitate and accelerate future implantation.