Denise Barbut

Improvement of outcomes after coronary artery bypass: A randomized trial comparing intraoperative high versus low mean arterial pressure

BACKGROUND The objective of this randomized clinical trial of elective coronary artery bypass grafting was to investigate whether intraoperative mean arterial pressure below autoregulatory limits of the coronary and cerebral circulations was a principal determinant of postoperative complications. The trial compared the impact of two strategies of hemodynamic management during cardiopulmonary bypass on outcome. Patients were randomized to a low mean arterial pressure of 50 to 60 mm Hg or a high mean arterial pressure of 80 to 100 mm Hg during cardiopulmonary bypass. METHODS A total of 248 patients undergoing primary, nonemergency coronary bypass were randomized to either low (n = 124) or high (n = 124) mean arterial pressure during cardiopulmonary bypass. The impact of the mean arterial pressure strategies on the following outcomes was assessed: mortality, cardiac morbidity, neurologic morbidity, cognitive deterioration, and changes in quality of life. All patients were observed prospectively to 6 months after the operation. RESULTS The overall incidence of combined cardiac and neurologic complications was significantly lower in the high pressure group at 4.8% than in the low pressure group at 12.9% (p = 0.026). For each of the individual outcomes, the trend favored the high pressure group. At 6 months after coronary bypass for the high and low pressure groups, respectively, total mortality rate was 1.6% versus 4.0%, stroke rate 2.4% versus 7.2%, and cardiac complication rate 2.4% versus 4.8%. Cognitive and functional status outcomes did not differ between the groups. CONCLUSION Higher mean arterial pressures during cardiopulmonary bypass can be achieved in a technically safe manner and effectively improve outcomes after coronary bypass.

Severity of aortic atheromatous disease diagnosed by transesophageal echocardiography predicts stroke and other outcomes associated with coronary artery surgery: a prospective study.

Advanced atheromatous disease of the thoracic aorta identified by transesophageal echocardiography (TEE) is a major risk factor for perioperative stroke.This study investigated whether varying degrees of atherosclerosis of the descending aorta, as assessed by TEE, are an independent predictor of cardiac and neurologic outcome in patients undergoing coronary artery bypass grafting (CABG). Intraoperative TEE of the descending aorta was performed on 189 of 248 patients participating in a randomized controlled trial of low (50-60 mm Hg) or high (80-100 mm Hg) mean arterial pressure during cardiopulmonary bypass for elective CABG. Aortic atheromatous disease was graded from I to V in order of increasing severity by observers blinded to outcome. Measured outcomes were death, stroke, and major cardiac events assessed at 1 wk and 6 mo. Nine of the 189 patients with TEE examinations had perioperative strokes by 1 wk. At 1 wk, no strokes had occurred in the 123 patients with atheroma Grades I or II, while the 1-wk stroke rate was 5.5% (2/36), 10.5% (2/19), and 45.5% (5/11) for Grades III, IV, and V, respectively (Fishers exact test, P = 0.00001). For 6-mo outcome, advancing aortic atheroma grade was a univariate predictor of stroke (P = 0.00001) and death (P = 0.03). By 6 mo there were one additional stroke, three additional deaths, and one additional major cardiac event. Atheromatous disease of the descending aorta was a strong predictor of stroke and death after CABG. TEE determination of atheroma grade is a critical element in the management of patients undergoing CABG surgery. (Anesth Analg 1996;83:701-8)

Comparison of Transcranial Doppler Ultrasonography and Transesophageal Echocardiography to Monitor Emboli During Coronary Artery Bypass Surgery

BACKGROUND AND PURPOSE Transcranial Doppler ultrasonography (TCD) is the standard technique for monitoring emboli in the cerebral circulation. Embolic signals have been detected with the use of this technique in most patients undergoing coronary artery bypass surgery. We previously reported that the majority of emboli are detected after release of aortic cross-clamps and partial occlusion clamps. In this study we compare the intraoperative use of TCD with transesophageal echocardiography (TEE) to monitor cerebral emboli. METHODS We simultaneously monitored 20 patients undergoing coronary bypass surgery with TCD and TEE. All patients also underwent routine TEE examination of the aorta. RESULTS Embolic signals were detected in all patients by both techniques. Mean total number of emboli was 535 +/- 109 by TEE compared with 133 +/- 28 by TCD. We found correlation between numbers of emboli detected by the two techniques at clamp placement and release (r = .65, P = .002). Clamp placement and release accounted for 84% of all emboli by TEE and 83% by TCD. By TEE, large, highly echogenic particles were detected after clamp release compared with small, barely echodense particles at the onset of bypass. No such distinction was apparent by TCD. We found correlation between severity of aortic atheroma and both TEE- (P = .003) and TCD-detected (P = .009) emboli. CONCLUSIONS TEE and TCD can both be used to continuously monitor emboli during coronary artery bypass surgery. However, TEE is invasive and justified only if it is being performed for intraoperative assessment of aortic atheromatosis or cardiac function.

Impact of Embolization During Coronary Artery Bypass Grafting on Outcome and Length of Stay

BACKGROUND Transcranial Doppler ultrasonography detects emboli in most patients during coronary artery bypass grafting. However, the significance of these emboli has not yet been established. METHODS We monitored 82 patients during coronary artery bypass grafting with this technique and related the numbers of emboli to the outcomes and length of hospital stay. RESULTS We detected cerebral emboli in all patients. Patients with stroke (n = 4; 4.9%) had a mean of 449 emboli, as compared with 169 emboli in patients without stroke (n = 78) (p = 0.005). Patients with major cardiac complications (n = 7) had a mean of 392 emboli, as compared with 163 in patients without such complications (n = 75) (p = 0.003). The mean hospital stay of survivors was 8.6 days in patients with fewer than 100 emboli (n = 40), 13.5 days in patients with 101 to 300 emboli (n = 23), 16.3 days in those with 301 to 500 emboli (n = 16), and 55.8 days in patients with more than 500 emboli (n = 6) (p = 0.0007). This relation was unchanged when patients with complications were excluded. The correlation between embolization and outcome was independent of the extent of aortic atheroma or age. CONCLUSIONS Emboli detected during coronary artery bypass grafting are significantly related to major cardiac and neurologic complications and affect length of stay in all patients, even in the absence of such specific complications.

Determination of size of aortic emboli and embolic load during coronary artery bypass grafting

BACKGROUND Embolic signals have been detected within both the aortic lumen and the intracranial vasculature during coronary artery bypass grafting. Total numbers of these emboli have been reported. The present study examined the size of individual emboli and the total volume of embolization. METHODS Using transesophageal echocardiography, we continuously monitored the aortic lumen of 10 patients undergoing isolated coronary artery bypass grafting. We manually analyzed 720,000 individual echo frames over a 4-minute period after the release of aortic clamps to track and to calculate the volume of 657 individual particles. The embolic load for the entire procedure was calculated from mean volume based on analysis of 1,508 particles. We simultaneously monitored the middle cerebral artery using transcranial Doppler ultrasonography and compared numbers of emboli detected by the two techniques. RESULTS Particle diameter ranged from 0.3 to 2.9 mm (mean, 0.8 mm), and particle volume from 0.01 to 12.5 mm3 (mean, 0.8 mm3). Twenty-eight percent of particles measured 1 mm or more, 44% measured 0.6 to 1.0 mm, and only 27% measured 0.6 mm or less in diameter. Aortic embolic load for the procedure ranged from 0.6 cm3 to 11.2 cm3 (mean, 3.7 cm3). Estimated cerebral embolic load for the procedure ranged from 60 to 510 mm3 (mean, 276 mm3). The fraction of aortic emboli entering the cerebral circulation was very variable (3.9% to 18.1%). Seventy-six percent of the embolic volume after the release of clamps occurred over a 20-second period. Only 1 patient was encephalopathic perioperatively. This patient had the largest estimated cerebral embolic load (510 mm3) and the second largest aortic embolic load (8.4 cm3). CONCLUSIONS We determined the size of individual intraaortic embolic particles and the total volume of embolization during coronary artery bypass grafting, and found the proportion entering the cerebral circulation to be very variable. The constitution of these particles and the neurologic impairment resulting from such embolization remains to be determined.

Aortic Atheroma Is Related to Outcome but Not Numbers of Emboli During Coronary Bypass

BACKGROUND The relation between aortic atheroma severity and stroke after coronary artery bypass grafting is established. The relation between atheroma severity and other outcome measures or numbers of emboli has not been determined. METHODS Using transesophageal echocardiography, we determined the severity of atheroma in the ascending, arch, and descending aortic segments in 84 patients undergoing operations. Seventy patients were monitored using transcranial Doppler ultrasonography. RESULTS The incidence of stroke was 33.3% among 9 patients with mobile plaque of the arch and 2.7% among 74 patients with nonmobile plaque (p = 0.011). Cardiac complications were not significantly related to atheroma severity in any aortic segment. Length of stay was significantly related to atheroma severity in the aortic arch (p = 0.025) and descending segment (p = 0.024). The presence of severe atheroma in both the arch and descending segments was associated with significantly longer hospital stays as compared with patients with severe atheroma in neither segment (p = 0.05). Numbers of emboli were greater in patients with severe atheroma at clamp placement, although the differences did not achieve statistical significance. CONCLUSIONS Aortic atheroma severity is related to stroke and to the duration of hospitalization after coronary artery bypass grafting. The lack of correlation between numbers of emboli and atheroma severity suggests that m any emboli may be nonatheromatous in nature.

Intraoperative cerebral arterial embolization during total hip arthroplasty.

Background Fat embolism to the pulmonary circulation is known to occur during total hip arthroplasty, especially during insertion of a cemented femoral component. Fat and air bubbles may enter the systemic circulation via a patent foramen ovale or through pulmonary circulation. Methods To determine whether microemboli to the brain were occurring during total hip arthroplasty, 23 patients underwent transcranial Doppler assessment of emboli to the middle cerebral artery during total hip arthroplasty. Surgery was performed with the patient in the lateral decubitus position so that the probe recorded from the nondependent side. Results Successful recordings were made in 20 patients, in 8 of 20 patients there were embolic signals, which ranging from 1 to 200. In all eight patients, signals were recorded during impaction of a cemented component or after relocation of the hip. Only one patient showed evidence of emboli with impaction of the acetabulum component. In two patients there were 150 and 200 embolic signals: in both mild respiratory symptoms developed. One patient became overtly agitated during a flurry of emboli. Conclusion Cerebral microemboli can occur during total hip arthroplasty. Whether this contributes to changes in postoperative cognitive function is unknown.

Aortic atheromatosis and risks of cerebral embolization

With the advent of transesophageal echocardiography, aortic atheromatosis has emerged as an important source of cerebral embolization. Mobile atheromatous plaque in the ascending aorta and aortic arch has been shown to constitute a strong and independent risk factor in patients with stroke. In patients undergoing coronary bypass surgery, it is the single most important contributing factor to perioperative neurologic morbidity. Emboli originating in the heart, aorta, and proximal cerebral vasculature have been observed intraoperatively in patients undergoing coronary bypass surgery, especially when aortic clamps are released. The constitution of these emboli is unclear, although an indeterminate fraction undoubtedly represents dislodged atheromatous material. The impact of such embolization in terms of neurologic outcome is currently under investigation. Prevention of embolization from mobile aortic atheroma in patients undergoing cardiac surgery may require modification of surgical technique. Secondary prevention in patients with a history of embolization can only be determined once the natural history of such lesions is established.

Particulate emboli capture by an intra-aortic filter device during cardiac surgery

OBJECTIVE Particulate embolization is associated with neurologic morbidity after cardiac surgery. Crossclamp manipulation has been identified as the single most significant cause of particulate emboli release during cardiac surgery. A new intra-aortic filtration method has been assessed with regard to its safety and its ability to capture particulate emboli before they enter the central circulation. METHODS Patients undergoing cardiac surgery with cardiopulmonary bypass through standard median sternotomy were selected for emboli management by means of intra-aortic filtration. A novel intra-aortic filter device was inserted through a modified 24F arterial cannula immediately before releasing the crossclamp in 77 patients. Filters remained in the aorta until cardiopulmonary bypass was discontinued and the heart was fully ejecting. The procedure was assessed for facility, safety, and effect on routine cardiopulmonary bypass operation and function. RESULTS The insertion and removal of the intra-aortic filter were safe, easy, and uneventful in most patients. Patient hemodynamics and bypass flow rates remained normal throughout the filter dwell period. No strokes or gross neurologic defects were noted. Electron microscopic analysis of 12 filters revealed an insignificant degree of platelet adhesion on filter surfaces. Histology samples (n = 44) were examined, and 66% (n = 29) showed evidence of atheromatous material, 36% (n = 16) with platelet-fibrin, 25% (n = 11) with true thrombus and/or blood clot, 7% (n = 3) with normal vessel wall, and 2% (n = 1) with aggregates of cholesterol or grumous portion of atheromatous plaque. CONCLUSION The intra-aortic filter can be safely deployed and captures particulate emboli, the predominant origin of which is atheromatous. The beneficial effects of this device on neurologic outcomes have yet to be determined.

Posterior distribution of infarcts in strokes related to cardiac operations.

BACKGROUND Stroke complicates cardiac surgical procedures in a substantial number of patients. The mechanism of stroke is predominantly embolic, although hypoperfusion may play a role. The aim of this study was to determine whether radiologic appearances in this population were consistent with an embolic cause. METHODS We reviewed computed tomographic scans and medical records in 24 patients who suffered stroke after cardiac operation. Stroke was evident at 24 hours in 19 patients (79%). Infarcts were multiple in 16 and single in 3 patients (group 1). The remaining 5 patients suffered stroke beyond 24 hours and had single infarcts on computed tomographic scan (group 2). RESULTS In group 1, 15 patients (79%) had bilateral cerebellar infarcts, 4 (74%) had posterior cerebral artery infarcts, 10 (53%) had posterior watershed infarcts, and 11 patients (58%) had middle cerebral artery branch infarcts. The mean number of vascular territories involved was 5.1 (range, 1 to 10). Mobile atheromatous plaque was present in the ascending aorta or arch in 5 of 9 patients (56%) in group 1. In group 2, stroke occurred in close association with atrial or ventricular fibrillation in 3 of 5 patients (60%). CONCLUSIONS In patients with radiologic evidence of infarction, perioperative strokes after cardiac operation are typically multiple, and involve the posterior parts of the brain, consistent with atheroembolization. Delayed strokes may be attributable to cardiogenic embolism.