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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)

Doppler-shifted ultrasound and spectral analysis were used to assess the carotid arteries of 77 elderly stroke patients, which represented 154 carotid bifurcations. Severe carotid disease was demonstrated at 19 of the 154 carotid bifurcations and in eight of these complete occlusion of the internal carotid artery was present. In 12 of the 19 instances the severe disease was in the internal carotid artery associated with the stroke. Localized carotid bruits were present in five patients and only three of these were associated with severe disease of the internal carotid artery. Minor disease was detected in 80 of the 154 carotid bifurcations and no disease was detected at the remaining 55 carotid bifurcations. An abnormally low ankle/arm systolic pressure ratio, which indicated occlusive arterial disease of the legs, was obtained in 19 of the 43 patients examined. No relationship was found between the severity of carotid artery disease and the presence of haemodynamically significant disease of the lower limbs. Ultrasound measurement of aortic compliance gave significantly lower values in elderly stroke patients compared to elderly asymptomatic volunteers. Comparison of flow-velocity transit times from the stroke-affected and non-affected limbs showed no consistent effect of the stroke on vascular tone in the patients assessed.