Microemboli during coronary artery bypass grafting: Genesis and effect on outcome

Abstract

Cerebral dysfunction after coronary artery bypass operations represents some of the most serious and costly complications of cardiac surgery. We used transcranial Doppler ultrasonography to detect and quantify the number of microemboli in the right middle cerebral artery of patients undergoing elective first coronary bypass operations (n = 117) and second coronary bypass operations (n = 10). We hypothesized that total microemboli were related to clinical outcome. A 2 MHz transducer was positioned in front of the ear above the zygomatic arch and depth gated to 50 mm. Microemboli were recorded as perturbations of the blood flow velocity in the middle cerebral artery and aurally monitored. Each episode of microembolism was specified both by clock time and as a perfusion or surgical event. Forty-one patients (32%) completed neuropsychologic evaluation with a battery of tests for cognitive function. Anxiety states and traits were also assessed. The distribution of microembolism showed that there were three groups of patients: < 30 microemboli (n = 83); 30 to 59 (n = 24); and > 60 (n = 20). Seven of 10 patients with cerebral complications (stroke, coma, delirium, aberrant behavior) were in the > 60 microemboli group. Those with cerebral complications had 20.7 +/- 4.5 microemboli from perfusion and 57.4 +/- 15.6 from surgical events. The 13 patients in the > 60 microemboli group without central nervous system symptoms had 95.5 +/- 19.5 microemboli from perfusion and 36.0 +/- 6.9 from surgical events. Neuropsychologic scores were most often depressed for memory (73%), comprehension (49%), attention (46%), and constructional ability (44%). The greatest change was in total score in the > 60 microemboli group (-3.3 +/- 0.6) compared with -1.1 +/- 0.2 and -1.9 +/- 0.2 for the 30 to 59 and < 30 groups, respectively. The incidences of cardiac and pulmonary complications and mortality were different between those patients with < 60 microemboli versus those with > 60 microemboli. Cardiac and pulmonary complications and mortality percentages were 4.7%, 3.7%, and 0.9%, respectively, for the < 60 microemboli group and 20%, 20%, and 15%, respectively, for the > 60 microemboli group. We concluded that transcranial Doppler ultrasonography is a useful technique to quantify and detect the source of microemboli during coronary artery bypass operations and may be useful in assessing new operative strategies, the quality of the perfusion, and potentially as an indicator for pharmacologic therapy in the operating room in patients with high microemboli counts.

Pathophysiology of Delirium in the Intensive Care Unit

“…To date, studies examining associations between surgery and delirium have investigated microemboli migration [149][150][151], hypoperfusion [64,137,[152][153][154], inflammatory responses [155][156][157], changes in hormone levels [158][159][160][161], and local and general anesthesia [64,133,162,163]. Gottesman and colleagues [152] hypothesized that a drop in the mean arterial pressure may put patients at risk for early cognitive dysfunction.…”

Recognition of the Importance of Embolization in Atherosclerotic Vascular Disease

“…These neurological sequelae are all believed to result from emboli. [61][62][63][64] In the past few years, there has been an emphasis on the presence of atherosclerosis in the aorta as a key risk factor for stroke during open heart surgery. 65,66 With TCD, cerebrovascular embolization has been found to occur in essentially all patients, and there is positive correlation between brain injury and embolic burden.…”

“…65,66 With TCD, cerebrovascular embolization has been found to occur in essentially all patients, and there is positive correlation between brain injury and embolic burden. 61,62 In a meticulous study with TEE and TCD, Barbut and colleagues 64 ), and the cerebral embolic load was 60 to 510 mm 3 (mean, 276 mm 3 ), with 3.9% to 18.1% of aortic emboli entering the cerebral circulation. The field of CABG is behind other areas of emboli protection, but this direction needs to be pursued.…”

Pharmacology and Biological Efficacy of a Recombinant, Humanized, Single-Chain Antibody C5 Complement Inhibitor in Patients Undergoing Coronary Artery Bypass Graft Surgery With Cardiopulmonary Bypass

“…1,4,8 Myocardial injury may manifest as perioperative Q-wave or non-Q-wave myocardial infarction (MI) or as severe ventricular dysfunction requiring circulatory assist. 1 Systemic inflammation, together with diffuse cerebral microembolization, 9 may result in clinically significant stroke or, more commonly, in cognitive deficits that persist in a significant proportion of patients. 9,10 Additional clinical sequelae of CPB-induced inflammation and ischemia include impaired hemostasis, pulmonary edema, renal insufficiency, and gastrointestinal dysfunction.…”

“…1 Systemic inflammation, together with diffuse cerebral microembolization, 9 may result in clinically significant stroke or, more commonly, in cognitive deficits that persist in a significant proportion of patients. 9,10 Additional clinical sequelae of CPB-induced inflammation and ischemia include impaired hemostasis, pulmonary edema, renal insufficiency, and gastrointestinal dysfunction. 4,11 Among the inflammatory cascades, activated components of the complement system contribute to all phases of the inflammatory response.…”