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

Abstract

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)

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

“…Both gaseous and solid microemboli can be detected using TCD through recognition of irregularities within the Doppler signal (Padayachee et al, 1987;Deverall et al, 1988;Ringelstein et al, 1998). Although these microemboli are often clinically silent, their detection may be of prognostic value in assessing risk of stroke, and of use during cardiac or vascular surgeries where gaseous emboli may originate from the oxygenator.…”

SELCAB (Self-Lung Cardiac Bypass) Procedures for Pediatric Patients

“…It is well known that CPB induces a massive amount of microembolic products, 18 including aggregated cells, polymerized fibrin, oxygenator-induced microbubbles, and microdebris. The pediatric circulatory system and microcirculation poorly tolerate microembolic phenomena.…”

New Directions in the Dynamic Assessment of Brain Blood Flow Regulation

“…Both gaseous and solid microemboli can be detected using TCD through recognition of irregularities within the Doppler signal (Padayachee et al, 1987;Deverall et al, 1988;Ringelstein et al, 1998). Although these microemboli are often clinically silent, their detection may be of prognostic value in assessing risk of stroke, and of use during cardiac or vascular surgeries where gaseous emboli may originate from the oxygenator.…”