https://cdr.lib.unc.edu/downloads/9p290c48k

ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery A Report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1991 Guidelines for Coronary Artery Bypass Graft Surgery)

ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: Summary article. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (committee to update the 1999 guidelines for coronary artery bypass graft surgery)

Objective To explore the relationship between hypoperfusion, embolism, and brain infarction. Design We studied 4 situations in which brain infarction is related to hypoperfusion: extracranial and intracranial occlusive vascular disease, reduced functional vascular reserve in patients with carotid artery occlusive disease, reduced collateral blood flow in patients given thrombolytic treatment, and cardiac surgery. We reviewed results of emboli monitoring using transcranial Doppler ultrasonography. Results Hypoperfusion is strongly linked to brain ischemia and infarction. The evidence includes close correlation of (1) the severity of arterial stenosis with brain infarction; (2) impaired functional blood flow reserve in patients with carotid artery disease and subsequent brain infarction; (3) reduced collateral blood flow with poor prognosis after thrombolysis; and (4) stroke-related neurologic deficits after cardiac surgery to hypoperfusion during surgery. Microembolization is common in patients with severe symptomatic carotid artery stenosis and during and after cardiac surgery. Conclusions Hypoperfusion and embolism often coexist and their pathophysiological features are interactive. Arterial lumenal narrowing and endothelial abnormalities stimulate clot formation and subsequent embolization. Reduced perfusion limits the ability of the bloodstream to clear or wash out emboli and microemboli and reduces available blood flow to regions rendered ischemic by emboli that block supply arteries. The brain border zones are a favored destination for microemboli that are not cleared. We posit that impaired washout is an important but neglected concept that intertwines hypoperfusion, embolization, and brain infarction.

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=NEUR&articleId=774385&pdfFileName=nhy7582.pdf

Impaired Clearance of Emboli (Washout) Is an Important Link Between Hypoperfusion, Embolism, and Ischemic Stroke

Microemboli have been implicated in the etiology of neuropsychological deficits after cardiopulmonary bypass. This study examined the incidence of high-intensity transcranial signals (microemboli) and their relation to changes in neuropsychological performance after surgery.Transcranial Doppler ultrasonography was used to measure middle cerebral artery blood flow velocity and detect microemboli. The number of high-intensity transcranial signals was determined and related to a neurological examination and absolute changes in neuropsychological performance as well as the number of patients considered to exhibit a neuropsychological deficit. Data were available on 100 consenting patients undergoing routine cardiopulmonary bypass. Fifty of the patients were randomly assigned to a procedure that included a 40-microns arterial line filter, and 50 had the procedure without any arterial line filter.Significantly more patients were found to have neuropsychological deficits in the group without the arterial line fi...

The impact of microemboli during cardiopulmonary bypass on neuropsychological functioning

Utility of transcranial Doppler ultrasound for the integrative assessment of cerebrovascular function.

The Detection of Microemboli in the Middle Cerebral Artery during Cardiopulmonary Bypass: A Transcranial Doppler Ultrasound Investigation Using Membrane and Bubble Oxygenators

The effect of arterial filtration on reduction of gaseous microemboli in the middle cerebral artery during cardiopulmonary bypass

The occurrence of neurological sequelae following cardiopulmonary bypass (CBP) surgery has stimulated interest in refining the techniques of extracorporeal circulation. Air micro-emboli originating from the oxygenator have been postulated as one source of cerebral damage. Since controversy still exists regarding the merits of bubble versus membrane oxygenators, this has prompted investigators to devise methods to determine the amount of micro-emboli produced during CPB. In this study, 27 patients undergoing CPB surgery for coronary artery disease (21) or valve replacement (6) were examined. The surgical and anaesthetic techniques were standardised in all patients except for the type of oxygenator used. A bubble oxygenator was used in 17 patients (Bentley Bio-10, William Harvey or Dideco) and a membrane oxygenator with a 25 microns filter in the remaining 10 patients (Bentley BOS CM50). Transcranial pulsed Doppler ultrasound was used to obtain blood velocity signals from the middle cerebral artery throughout CPB. A flow disturbance index (FDI) was defined which provided a representative index of the number of micro-emboli passing the ultrasound transducer. The FDI indicated the presence of gaseous micro-emboli during insertion of the aortic cannula in 22 of the 27 patients. In the 17 patients with a bubble oxygenator, the FDI ranged from 4-39. In the 10 patients with a membrane oxygenator, the FDI was always 0. Variation of gas flow rates in 3 patients with bubble oxygenators showed a change in the FDI from 4 +/- 4 at a flow rate of 2 l/min to 17 +/- 9 at 5 l/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrasound detection of micro-emboli in the middle cerebral artery during cardiopulmonary bypass surgery

The measurement of blood flow in small arteries is a potential extension of magnetic resonance (MR) angiography. We have compared flow measurements based on MR phase mapping with those obtained by Doppler ultrasound and electromagnetic flowmetry in both phantom and animal models. Correlation between modalities was high forin vitro studies (R
 2=0.93–0.98).In vivo, electrocardiogram-gated MR and Doppler ultrasound flow measurements compared to electromagnetic flowmetry showed fair correlation coefficients (R
 2=0.73 and 0.66, respectively). However, limits of agreement indicated that in small vessels flow measured by the three modalities could differ by up to ±90 mL/min. For both models, arteries in the range of 3–6.5 mm in diameter produced complementary errors in area and velocity measurements in MR studies. Ungated MR studies showed a reduced agreement (R
 2=0.88in vitro, 0.54in vivo), which may in part be due to poor sampling of the velocity pattern. The results show that the high correlation obtainedin vitro cannot be extrapolated to thein vivo situation, where additional physiological and anatomical variables are encountered.

S. Parsons

Papers

The Detection of Microemboli in the Middle Cerebral Artery during Cardiopulmonary Bypass: A Transcranial Doppler Ultrasound Investigation Using Membrane and Bubble Oxygenators

The effect of arterial filtration on reduction of gaseous microemboli in the middle cerebral artery during cardiopulmonary bypass

Ultrasound detection of micro-emboli in the middle cerebral artery during cardiopulmonary bypass surgery

Measurement of flow in small vessels by magnetic resonance phase mapping techniques: an in vitro and in vivo study.