A Critical Assessment of Neurological Risk During Warm Heart Surgery

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A prospective randomized trial comparing retrograde warm blood cardioplegia with cold oxygenated crystalloid cardioplegia in coronary bypass patients at Emory University revealed an increased risk of adverse neurological events in the warm group (4.5% vs 1.4%, p < 0.005). Multivariant analysis found four variables to be independent predictors of adverse neurological outcome: congestive heart failure (p = 0.002); age (p = 0.002); aortic cross-clamp time (p = 0.02); and randomization to the warm group (p = 0.026). In Toronto, a prospective randomized trial compared antegrade warm blood cardioplegia with antegrade cold blood cardioplegia. Compared to the Emory trial, the Toronto series contained fewer female patients (16% vs 25%), fewer patients older than age 70 (16% vs 30%), and fewer redo operations (4% vs 14%). The other prominent differences between the Emory series and the Toronto series were: extensive use of retrograde cardioplegia in the Emory series; mild hypothermia in the warm group in the Toronto series; and elevated serum glucose in the warm group in the Emory series. The Toronto series showed no difference in adverse neurological events comparing cold versus warm cardioplegia groups. A comparison of these two series suggests that mild hypothermia in the Toronto series, elevated glucose in the Emory series, or the use of retrograde cardioplegia may be operative in the elevated incidence of adverse neurological events seen in the Emory series in addition to a relatively larger number of high-risk patients (female, elderly, and redo) in the Emory series.