Regional cerebral oxygen saturation in cardiac arrest survivors undergoing targeted temperature management 36 °C versus 33 °C: A randomized clinical trial

Aim of study: To investigate whether regional cerebral oxygen saturation (rSO₂) differs in out-of-hospital cardiac arrest (OHCA) survivors undergoing targeted temperature management (TTM) 36 °C versus 33 °C.

Methods: A randomized clinical trial was conducted at intensive care units in two referral hospitals. Fifty-seven comatose OHCA survivors were randomized into either a 36 °C or 33 °C group. Patients were cooled and maintained at an oesophageal temperature of either 36 °C or 33 °C for 24 hours, rewarmed at a rate of 0.25 °C/hour, and maintained at <37.5 °C until 72 hours. During 72 hours of TTM, rSO₂ was continuously monitored on the left forehead using near-infrared spectroscopy (INVOS^TM 5100C). The rSO₂ level at 72 hours was compared between the two groups. Next, serial rSO₂ levels for 72 hours were compared using mixed effects regression. The association between rSO₂ levels and 6-month neurological outcomes was also evaluated.

Results: There were no significant differences in the rSO₂ level at 72 hours between the 36 °C and 33 °C groups (p = 0.372). Furthermore, serial rSO₂ levels for 72 hours of TTM were not different between the two groups (p = 0.733). However, low rSO₂ levels, particularly at 24 hours of TTM, were significantly associated with poor 6-month neurological outcomes (odds ratio = 0.899, 95% confidence interval: 0.831-0.974). The area under the receiver operating characteristic curve of the rSO₂ level at 24 hours for poor neurological outcomes was 0.800.

Conclusions: Regardless of target temperatures, low rSO₂ levels during TTM were significantly associated with poor 6-month neurological outcomes in OHCA survivors.