Monitoring of regional cerebral oxygenation by near-infrared spectroscopy during continuous retrograde cerebral perfusion for aortic arch surgery1

Objective: To assess the value of monitoring of regional cerebral oxygen saturation (rSO 2 ) during aortic arch surgery using continuous retrograde cerebral perfusion (CRCP) in conjunction with profound hypothermic circulatory arrest (HCA). Methods: The rSO 2 of 12 consecutive patients was monitored non-invasively using near-infrared spectroscopy (NIRS) and the data were analyzed statistically. Results: The mean duration of HCA with CRCP was 62 ± 14. min. The mean CRCP flow rate was 226 ± 163 ml/min. Surgical outcomes were favorable with only a single hospital death (8.3% ). However, the rSO 2 decreased gradually in all patients during HCA, even combined with CRCP, and fell to 46 ± 8.7% on average. It did not change so greatly before HCA and returned finally to its initial level at the end of re-warming. Only one patient developed a permanent neurologic deficit; this patient showed the greatest decrease of rSO 2 from 56% to 29% after the longest HCA of 88 min. Two parameters, End-rSO 2 (the ratio of post- to pre-HCA rSO 2 ) and Δ-rSO 2 (the rate of decrease from preto post-HCA rSO 2 ) were obtained since the initial values of rSO 2 before surgery differed. There were linear correlations between the CRCP flow rate and each of these two parameters. A multiple regression analysis also revealed a linear equation relating the parameters, which allowed prediction of the safe duration of HCA in different conditions of CRCP and a more favorable adjustment of the CRCP condition in each patient. Conclusions: The study suggests that the combination of HCA and CRCP has a limit of safe duration in spite of its potential usefulness for brain protection, and that rSO 2 monitored by NIRS is useful in testing for adequate brain protection. It is hoped that monitoring of rSO 2 can facilitate prediction of the safe duration of HCA with CRCP and a more favorable adjustment of CRCP.