NEW YORK – Deep hypothermia may affect long-term survival in individuals who have aortic arch surgery with antegrade cerebral perfusion (ACP), but not short-term outcomes in terms of death and major morbidities, according to a Baylor College of Medicine study.
The study evaluated outcomes of 544 consecutive patients who had proximal and total aortic arch surgery and received ACP for more than 30 minutes over a 10-year period, said lead investigator Ourania Preventza, MD, of the division of cardiothoracic surgery at the college in Houston. The researchers compared results of three different hypothermia levels: deep hypothermia at 14.1°-20° C; low-moderate at 20.1°-23.9° C; and high-moderate at 24°-28° C. The study also classified ACP time in two levels: 31-45 minutes for 238 patients (43.8%); and 45 minutes or more in 306 patients (56.3%).
Dr. Ourania Preventza
“The different temperature levels did not significantly affect the short-term mortality and major morbidity rates,” Dr. Preventza said. “Reoperation for bleeding was associated with lower temperature (14.1°-20° C). The long-term survival rate in patients who underwent proximal arch surgery involving ACP for more than 30 minutes and use of moderate hypothermia (20.1°-28° C) were actually improved.”
While the outcomes showed small variations between the three groups, with deep hypothermia being associated with a higher percentage of adverse outcomes, Dr. Preventza said the differences were not statistically significant. The overall operative mortality rate was 12.5% (68 patients): 15.5% (18 patients) in the deep-hypothermia group; 11.8% (31 patients) in the low-moderate group; and 11.5% (19 patients) in the high-moderate group (P = 0.54).
The patients who underwent deep hypothermia were more likely to receive unilateral ACP, and those who underwent moderate hypothermia were more likely to have bilateral ACP, Dr. Preventza said at the meeting sponsored by the American Association for Thoracic Surgery. The deep-hypothermia group had higher transfusion rates, but, again, the researchers did not consider this variation to be statistically significant.
In the deep-hypothermia group, 20.9% of patients had a reoperation for bleeding, compared with 11.3% in the overall group and 7.7% and 10.2% in the low- and high-moderate groups, respectively, Dr. Preventza reported. Multivariate analysis revealed that higher temperature was associated with less bleeding, with an odds ratio of 0.61 (P = 0.015).
Deep hypothermia was related to statistically significant differences in the rates of permanent stroke and permanent neurologic events in the univariate analysis only, Dr. Preventza said: 6.3% and 7.2%, respectively, in the overall analysis vs. 12.2% for both events in the deep-hypothermia group. In the propensity score analysis, the rates of permanent stroke and permanent neurologic events in the moderate-hypothermia group were 7.6% and 8.5%, respectively, vs. 11.3% for both events in the deep-hypothermia group, a nonsignificant difference.
“With regard to permanent stoke and permanent neurological events, the multivariate analysis showed that preoperatively a neurologic deficit as well as acute type I aortic dissection were associated with adverse neurological events,” she said.
“However,” Dr. Preventza added, “the surprising thing is that when we looked at long-term survival for the entire cohort, we saw that the patients with moderate hypothermia did better.”
Kaplan-Meier analysis for the propensity pairs showed that the probability of survival at 8 years was 55.3% for the deep-hypothermia group vs. 68.5% for the moderate-hypothermia group.
The approach the Baylor researchers used involved cannulating the axillary or innominate artery in most patients before administering ACP, although a few patients had femoral or direct aortic cannulation, Dr. Preventza said. For bilateral ACP, the researchers delivered cerebral perfusion via a 9-French Pruitt balloon-tip catheter (LeMaitre Vascular) in the left common carotid artery. To protect the brain, they administered perfusion at 8-12 cc/kg per min and maintained a perfusion pressure of 50-70 mm Hg, as measured via the radial arterial line and guided by near-infrared spectroscopy.
Dr. Preventza had no relevant disclosures.