HYPOTHERMIC CIRCULATORY ARREST IN OPERATIONS ON THE THORACIC AORTA - DETERMINANTS OF OPERATIVE MORTALITY AND NEUROLOGIC OUTCOME

This study was undertaken to determine the factors that influence the final outcome after hypothermic circulatory arrest Between 1985 and 19 92 a uniform method of hypothermic circulatory arrest was used in 200 patients as the primary method of cerebral protection during operation s on aneurysms of the thoracic aorta. There were 30 hospital deaths (1 5 %). Age greater than 60 years (relative risk 3.7, p < 0.02), emergen cy operation and hemodynamic compromise (relative risk 22.2, p < 0.000 ), concomitant procedures (relative risk 2.7, p < 0.04), presentation with new neurologic symptoms (relative risk 5.2, p < 0.04), and postop erative permanent neurologic deficits (relative risk 9.4, p < 0.000) w ere found to be significant predictors of operative mortality. A total of 183 patients were available for evaluation of neurologic function and outcome. Multivariate analysis of this cohort of patients by multi ple logistic regression showed that temporary neurologic dysfunction o ccurred in 36 cases (19 %). Temporary neurologic dysfunction correlate d with the duration of hypothermic circulatory arrest (47 +/- 16 minut es; odds ratio 1.06/minute; p < 0.001) and age (66 +/- 14 years; odds ratio 1.07/year; p < 0.001). Embolic strokes occurred in 22 patients ( 11 %) and were associated with permanent deficits in 13 (7 %). Strokes correlated significantly with age (older than 60, 21 % versus younger than 60, 1 %; p < 0.001) and operations on the arch and descending ao rtic aneurysms containing clot or atheroma (p < 0.001). This experienc e shows that the operative mortality is not affected by any parameters related to the use of hypothermic circulatory arrest. The incidence o f temporary neurologic dysfunction rises linearly in relation to the a ge of the patient and the duration of hypothermic circulatory arrest. However, permanent neurologic injury is a result of thromboembolic eve nts and is not related to the method of cerebral protection used. Addi tional methods to prevent perioperative embolic strokes are needed. Hy pothermic circulatory arrest affords adequate cerebral protection if t he arrest period is kept less than 60 minutes. We will continue to use this modality until the safety and utility of the alternate methods o f cerebral protection are shown to be superior.