Pre-hospital portable monitoring of cerebral regional oxygen saturation (rSO2) in seven patients with out-of-hospital cardiac arrest.

Background: In recent years, measurement of cerebral regional oxygen saturation (rSO₂) has attracted attention during resuscitation. However, serial changes of cerebral rSO₂ in pre-hospital settings are unclear. The objective of this study was to clarify serial changes in cerebral rSO₂ of patients with out-of-hospital cardiac arrest (OHCA) in the prehospital setting. Methods: We recently developed a portable rSO₂ monitor that is small (170 × 100 × 50 mm in size and 600 g in weight) enough to carry in pre-hospital settings. The sensor is attached to the patient's forehead by the ELT (Emergency Life-saving Technician), and it monitors rSO₂ continuously. Results: From June 2013 through August 2014, serial changes in cerebral rSO₂ in seven patients were evaluated. According to the results of the serial changes in rSO₂, four patterns of rSO₂ change were found, as follows. Type 1: High rSO₂ (around about 60 %) type (n = 1). Initial electrocardiogram was ventricular fibrillation and ROSC (return of spontaneous circulation) could be diagnosed in pre-hospital setting. Her outcome at discharge was Good Recovery (GR). Type 2: Low rSO₂ (around about 45-50 %) type (n = 3). They did not get ROSC even once. Type 3: Gradually decreasing rSO₂ type (n = 2): ROSC could be diagnosed in hospital, but not in pre-hospital setting. Their outcomes at discharge were not GR. Type 4: other type (n = 1). In this patient with ROSC when ELT started cerebral rSO₂ measurement, cerebral rSO₂ was 67.3 % at measurement start, it dropped gradually to 54.5 %, and then rose to 74.3 %. The cerebral oxygenation was impaired due to possible cardiac arrest again, and after that, ROSC led to the recovery of cerebral blood flow. Conclusion: We could measure serial changes in cerebral rSO₂ in seven patients with OHCA in the pre-hospital setting. Our data suggest that pre-hospital monitoring of cerebral rSO₂ might lead to a new resuscitation strategy. [ABSTRACT FROM AUTHOR]