Cerebral oximetry and autoregulation monitoring in shock patients

Background: Data on regional cerebral oxygen saturation (rSO2) and cerebral autoregulation monitoring in shock patients are limited. This study aimed to find the optimal range of rSO2 and cerebral oximetry index (COx), an autoregulation index correlated with adequate tissue perfusion determined by standard clinical and laboratory assessment. Method: We plan to monitor cerebral oximetry using near-infrared spectroscopy in shock patients admitted to the medical intensive care unit (MICU) at Siriraj Hospital. The rSO2 are continuously recorded for 72 hours [48] after admission or 24 hours after cessation of vasopressor infusion. The COx is calculated from the correlation coefficient between rSO2 and MAP. Data on patient demographics, treatments, physiologic parameters, and outcomes are recorded. The primary objective is to identify the optimal rSO2 and COx correlated with adequate tissue perfusion assessed by the current standard method. Adequate tissue perfusion as is defined as MAP ≥65 mmHg and two of the following criteria: urine ≥0.5 ml/kg/hour, capillary refill time ≤3 seconds, improvement in consciousness, lactate reduction ≥10% in 1 hour, serum lactate <2 mmol/L, or central venous oxygen saturation (ScVO2) ≥70%. Since the optimal values of rSO2 and COx in shock patients are unknown, we are unable to perform the sample size calculation. Thus, for this study, we plan to collect data on rSO2 and COx in 30 patients. Hypothesis: We hypothesize that the values of rSO2 and COx are different between patients with adequate and inadequate tissue perfusion. Ethics statement: The study was reviewed and approved by the Human Research Protection Unit of Siriraj Hospital, Mahidol University (certificate of approval no. si 410/2022).