Brain injury in canine models of cardiac surgery.

Neuropathology and neurologic impairment were characterized in a clinically relevant canine model of hypothermic (18°C) circulatory arrest (HCA) and cardiopulmonary bypass (CPB). Adult dogs underwent 2 hours of HCA (n = 39), 1 hour of HCA (n = 20), or standard CPB (n = 22) and survived 2, 8, 24, or 72 hours. Neurologic impairment and neuropathology were much more severe after 2-hour HCA than after 1-hour HCA or CPB; histopathology and neurologic deficit scores were significantly correlated. Apoptosis developed as early as 2 hours after injury and was most severe in the granule cells of the hippocampal dentate gyrus. Necrosis evolved more slowly and was most severe in amygdala and pyramidal neurons in the cornu ammonis hippocampus. Neuronal injury was minimal up to 24 hours after 1-hour HCA, but 1 dog that survived to 72 hours showed substantial necrosis in the hippocampus, suggesting that, with longer survival time, the injury was worse. Although neuronal injury was minimal after CPB, we observed rare apoptotic and necrotic neurons in hippocampi and caudate nuclei. These results have important implications for CPB in humans and may help explain the subtle cognitive changes experienced by patients after CPB.

Increased exposure improves recruitment: early results of a program designed to attract medical students into surgical careers.

BACKGROUND: In recent years, general surgery and surgical subspecialty residency interests have remained somewhat static among medical students, casting some doubt on recruitment of the best students. A summer research program was designed to introduce interested medical students to surgical careers. METHODS: In 2003, the division of cardiac surgery instituted an 8-week structured summer research experience for second-year medical students. Three students were competitively chosen from a pool of 20 to 30 interested applicants every year. They were taught basic operative suturing and knot-tying techniques. Students participated in large animal research projects, witnessed clinical operations, and developed individual clinical projects with an attending cardiac surgeon. The summer experience culminated with oral presentations to the cardiac surgery division, with many students producing manuscripts for publication or presentation at national meetings. RESULTS: From 2003 to 2012, 30 students participated in the program. Of 23 participants who had applied for residency, 12 (52.2%) matched into general surgery or a surgical subspecialty, including 3 into plastic surgery, 2 into cardiothoracic surgery, 1 into orthopedic surgery, and 1 into neurosurgery. These students produced 64 publications and presented at 51 national and regional meetings. CONCLUSIONS: These results suggest that an 8-week, structured program introducing students to cardiothoracic surgery can successfully attract students into surgical careers. The percentage (52%) of these students entering a surgical career compares favorably with national residency match results (16%) and graduating Johns Hopkins medical students (22%). Increased effort for early exposure to surgery may be a key factor in generating and securing surgical interest among medical students.

Disclosure of physician-specific behavior improves blood utilization protocol adherence in cardiac surgery.

BACKGROUND: Evidence indicates that a transfusion (Tx) trigger hemoglobin (Hgb) value of 8 gm/dL may be safer than a more liberal Tx trigger in cardiac surgery (CS) patients. We hypothesized that weekly physician feedback would improve adherence to such a protocol, but that the public identification of individual physician behavior would have an additive effect. METHODS: We concurrently reviewed all adult CS patients at our institution from December 1, 2010 to May 27, 2011. We matched any cardiac surgery intensive care unit Tx event (red blood cells) with the Hgb value immediately before Tx. Patients requiring massive transfusions (>10 units/24 hours) were excluded. After all providers agreed upon a Hgb of 8 as the Tx trigger, we studied 3 consecutive time periods: no feedback, weekly feedback of group Tx behavior, and weekly feedback with identification of individual surgeon Tx behavior. RESULTS: Of the 512 patients who underwent cardiac operations, 144 patients underwent 510 Tx events. Compared with period 1, the unadjusted odds of receiving a Tx above 8 gm/dL decreased by 48% in study period 2(odds ratio: 0.52, p < 0.01), and 63% in study period 3(odds ratio: 0.37, p <0.001). Single unit transfusion rates increased from 77% to greater than 90% (p < 0.001). In-hospital mortality also fell from period 1 to period 3 (7.0% to 1.5%, p = 0.02) with the observed to expected mortality ratio decreasing from 2.19 to 0.51. CONCLUSIONS: Blood transfusion protocol adherence improves when weekly feedback is provided. Identifying individual surgeon behavior improves adherence to a greater degree. Routine presentation of quality metrics with identification of individual physician-specific behavior may be the most effective way to accomplish performance improvement.

Hemoglobin drift after cardiac surgery.

BACKGROUND: Recent literature suggests that a restrictive approach to red blood cell transfusions is associated with improved outcomes in cardiac surgery patients. Even in the absence of bleeding, intravascular fluid shifts cause hemoglobin levels to drift postoperatively, possibly confounding the decision to transfuse. The purpose of this study was to define the natural progression of hemoglobin levels in postoperative cardiac surgery patients. METHODS: All cardiac surgery patients from October 2010 through March 2011 who did not receive a postoperative transfusion were included. Primary stratification was by intraoperative transfusion status. Change in hemoglobin was evaluated relative to the initial postoperative hemoglobin. Maximal drift was defined as the maximum minus the minimum hemoglobin for a given hospitalization. Final drift was defined as the difference between initial and discharge hemoglobin. RESULTS: The final cohort included 199 patients: 71 (36%) received an intraoperative transfusion, whereas 128 (64%) did not. The average initial and final hemoglobin levels for all patients were 11.0±1.4 g/dL and 9.9±1.3 g/dL, respectively, giving a final drift of 1.1±1.4 g/dL. The maximal drift was 1.8±1.1 g/dL and was similar regardless of intraoperative transfusion status (p=0.9). Although all patients' hemoglobin initially dropped, 79% of patients reached a nadir and experienced a mean recovery of 0.7±0.7 g/dL by discharge. On multivariable analysis, increasing cardiopulmonary bypass time was significantly associated with total hemoglobin drift (coefficient/hour, 0.3 [0.1-0.5] g/dL; p=0.02). CONCLUSIONS: In this report of hemoglobin drift after cardiac surgery, although all postoperative patients experienced downward hemoglobin drift, 79% of patients exhibited hemoglobin recovery before discharge. Physicians should consider the eventual upward hemoglobin drift before administering red blood cell transfusions.

Successful repair of an atrioesophageal fistula after catheter ablation for atrial fibrillation.

Catheter ablation of arrhythmias can result in the rare but devastating complication of an atrioesophageal fistula. This complication can be associated with significant neurologic morbidity and high mortality and requires a high index of suspicion to facilitate life-saving surgical intervention. Herein, we report the successful repair of an atrioesophageal fistula after catheter ablation for atrial fibrillation.

Serum levels of neuron-specific ubiquitin carboxyl-terminal esterase-L1 predict brain injury in a canine model of hypothermic circulatory arrest.

OBJECTIVES: Ubiquitin carboxyl-terminal esterase-L1 (UCHL1) is a protein highly selectively expressed in neurons and has been linked to neurodegenerative disease in humans. We hypothesize that UCHL1 would be an effective serum biomarker for brain injury as tested in canine models of hypothermic circulatory arrest (HCA) and cardiopulmonary bypass (CPB). METHODS: Dogs were exposed to CPB (n = 14), 1 hour of HCA (1h-HCA; n = 11), or 2 hours of HCA (2h-HCA; n = 20). Cerebrospinal fluid and serum were collected at baseline, 8 hours, and 24 hours after treatment. UCHL1 levels were measured using a sandwich enzyme-linked immunosorbent assay. Neurologic function and histopathology were scored at 24 hours, and UCHL1 immunoreactivity was examined at 8 hours. RESULTS: Baseline UCHL1 protein levels in cerebrospinal fluid and serum were similar for all groups. In serum, UCHL1 levels were elevated at 8 hours after treatment for 2h-HCA subjects compared with baseline values (P < .01) and also compared with CPB dogs at 8 hours (P < .01). A serum UCHL1 level above 3.9 ng/(mg total protein) at 8 hours had the best discriminatory power for predicting functional disability. In cerebrospinal fluid, UCHL1 was elevated in all groups at 8 hours after treatment compared with baseline (P < .01). However, UCHL1 levels in cerebrospinal fluid remained elevated at 24 hours only in 2h-HCA subjects (P < .01). Functional and histopathologic scores were closely correlated (Pearson coefficient, 0.66; P < .01) and were significantly worse in 2h-HCA animals. CONCLUSIONS: This is the first report associating elevated serum UCHL1 with brain injury. The novel neuronal biomarker UCHL1 is increased in serum 8 hours after severe neurologic insult in 2h-HCA animals compared with CPB animals. These results support the potential for use in cardiac surgery patients and form the basis for clinical correlation in humans.