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Microemboli during coronary artery bypass grafting. Genesis and effect on outcome
R E Clark1, J Brillman, D A Davis
1Cardiovascular and Pulmonary Research Center, Allegheny-Singer Research Institute, Pittsburgh, PA 15212.
Insights
High microemboli counts during coronary artery bypass operations are linked to increased cerebral complications and poorer outcomes. Transcranial Doppler ultrasonography can detect and quantify these microemboli, aiding in risk assessment and potential interventions.
Area of Science:
- Neurosurgery
- Cardiovascular Surgery
- Medical Imaging
Background:
- Cerebral dysfunction is a serious complication of cardiac surgery.
- Quantifying microemboli during coronary artery bypass (CAB) operations is crucial for understanding patient outcomes.
Purpose of the Study:
- To use transcranial Doppler ultrasonography (TCD) to detect and quantify microemboli during CAB operations.
- To investigate the relationship between microemboli load and clinical outcomes, including cognitive function and surgical complications.
Main Methods:
- 117 patients undergoing first CAB and 10 undergoing second CAB were monitored using TCD.
- Microemboli were detected in the middle cerebral artery and categorized by event type (perfusion or surgical).
- Neuropsychological evaluation and assessment of anxiety were performed on 41 patients.
Main Results:
- Patients were grouped by microemboli count: <30 (n=83), 30-59 (n=24), and >60 (n=20).
- Seven of ten patients with cerebral complications had >60 microemboli.
- The >60 microemboli group showed significantly higher rates of cardiac/pulmonary complications (20%) and mortality (15%) compared to the <60 group (4.7%, 3.7%, 0.9%).
- Cognitive function, particularly memory and comprehension, was most impaired in the >60 microemboli group.
Conclusions:
- TCD is effective for quantifying microemboli during CAB operations and identifying their sources.
- High microemboli counts correlate with increased risk of cerebral dysfunction, cognitive decline, and other surgical complications.
- TCD may assist in evaluating surgical strategies, perfusion quality, and guiding perioperative pharmacologic therapy.
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.