Significance of gaseous microemboli in the cerebral circulation during cardiopulmonary bypass in dogs

W. E. Johnston, D. A. Stump, D. S. DeWitt, J. Vinten-Johansen, W. K. O'Steen, R. L. James, D. S. Prough

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Background. Gaseous microemboli during cardiac surgery may damage the brain by reducing cerebral blood flow (CBF). We examined whether the incidence of gaseous microemboli during 150-minute hypothermic (28°C) cardiopulmonary bypass (CPB) adversely affects CBF (radioactive microspheres). Methods and Results. Thirty anesthetized dogs were placed on CPB using bubble oxygenators with 50% O2 (n=10) or 100% O2 (n=10) to produce a wide range in the number of gaseous microemboli or membrane oxygenators with 50% O2 (n=10) to avoid microemboli. The number of carotid artery microemboli occurring in a 1-minute interval was counted using a 5- MHz Doppler probe every 15 minutes for the duration of CPB, which lasted 258±5 minutes. With bubbled 100% O2, the number of microemboli averaged 4.1±1.7 emboli per minute on normothermic bypass and increased with cooling to 18.3±4.9 emboli per minute (P<.001). With bubbled 50% O2, the microemboli number was greater on normothermic bypass (19.8±9.8 emboli per minute, P=.0653 compared with bubbled 100% O2) and increased with cooling (100.3±18.7 emboli per minute, P<.001) to a greater extent than with bubbled 100% O2 (P<.001). In contrast, with membrane 50% O2, the emboli number was small (0.6±0.1 emboli per minute) and did not change with CPB temperature. CBF values were not reduced after termination of CPB, even when compared with prebypass values, being 48.3±7.5 mL/min per 100 g (bubbled 50% O2), 49.6±4.1 mL/min per 100 g (bubble 100% O2), and 44.5±2.8 mL/min per 100 g (membrane 50% O2, P=.7581). Similarly, regional perfusion to the cerebellum, hippocampus, and caudal brainstem was not adversely affected by microemboli. After CPB, cortical biopsies demonstrated no difference among groups with respect to lactate (P=.1753), energy charge (P=.5179), and brain water content (P=.939). Retinal histopathology indicated no differences among groups. Conclusions. These results indicate that (1) the incidence of gaseous microemboli during hypothermia increases when a bubble oxygenator is used, and (2) global CBF and regional brain perfusion are not adversely affected by numerous gaseous microemboli.

Original languageEnglish (US)
Pages (from-to)319-329
Number of pages11
Issue number5 II
StatePublished - Jan 1 1993


  • brain
  • cerebrovascular circulation
  • embolism
  • extracorporeal circulation

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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    Johnston, W. E., Stump, D. A., DeWitt, D. S., Vinten-Johansen, J., O'Steen, W. K., James, R. L., & Prough, D. S. (1993). Significance of gaseous microemboli in the cerebral circulation during cardiopulmonary bypass in dogs. Circulation, 88(5 II), 319-329.