Clinical values of cerebral oxygen saturation monitoring in patients with septic shock.

Objectives: Sepsis associated encephalopathy (SAE) is a common neurological complication of sepsis. Delirium is a common symtom of SAE. The pathophysiology of SAE is still unclear, but several likely mechanisms have been proposed, such as mitochondrial and endothelial dysfunction, neurotransmission disturbances, derangements of calcium homeostasis, cerebral microcirculation dysfunction, and brain hypoperfusion. Near-infrared spectroscopy (NIRS) is a non-invasive measure for regional cerebral oxygen saturation (rSO), which has attracted more attention these years. Previous studies have reported that abnormal NIRS values were associated with delirium in critically ill patients. Blood pressure management according to NIRS monitoring improved the organ perfusion and prognosis of patients. This study aimed to observe the dynamic changes of rSO using NIRS in septic shock patients, and analyze the relationship between them.

Methods: A total of 48 septic patients who admitted to the intensive care unit (ICU) of Xiangya Hospital, Central South University from August 2017 to May 2018, were retrospectively study. Septic shock was diagnosed according to the criteria of sepsis 3.0 defined by the American Association of Critical Care Medicine and the European Society of Critical Care Medicine. NIRS monitoring was performed during the first 6 hours admitted to ICU with sensors placed on the bilateral forehead of patients. The maximum (rSOmax), minimum (rSOmin), mean value, and the variation rate during the first 6 hours of monitor were recorded. The following data were collected upon the first 24 h after admission to the ICU: The baseline data of patients, laboratory examination results (routine blood test, liver and renal function, blood gas analysis, indicators of infection, and coagulation function), scoring system results [Glasgow Coma Scale (GCS), Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA)]. Delirium was screened with the Confusion Assessment Method for ICU (CAM-ICU). The length of time on mechanical ventilation (MV), length of ICU-stay, length of hospital-stay, and 28-day mortality were also recorded. The primary outcome was 28-day mortality, and the secondary outcomes were the incidence of delirium, length of ICU-stay, and length of hospital-stay. The differences between survivors and non-survivors, and patients with or without delirium were analyzed, and the risk factors for delirium were assessed. The performance of rSO-related indexes (rSOmax, rSOmin, the mean value, and the variation rate of rSO) in predicting 28-day mortality and delirium was analyzed and the cutoff values were determined.

Results: The overall 28-day mortality of septic shock patients was 47.92% (23/48), and the incidence of delirium was 18.75% (9/48). The rSOmin was significantly lower in the non-survivors than the survivors (=0.042). The variation rate of rSO was higher in patients with delirium than those without delirium (=0.006). The independent risk factors for delirium were rSOmax, the level of direct bilirubin (DBIL), and whether achieved the 6-hour bundle. To predict the 28-day mortality of septic shock patients, the area under the receiver operating characteristic curve (AUROC) for rSOmax, rSOmin, the mean value and the variation rate of rSO were 0.616, 0.606, 0.623, and 0.504, respectively. To predict the incidence of delirium, AUROC for rSOmax, rSOmin, the mean value and the variation rate of rSO were 0.682, 0.617, 0.580, and 0.501, respectively. The best cutoff value for rSOmax in predicting delirium was 77.5% (sensitivity was 0.444, specificity was 0.897). The best cutoff value for rSOmin in predicting delirium was 65.5% (sensitivity was 0.556, specificity was 0.744).

Conclusions: Cerebral anoxia and hyperoxia, as well as the large fluctuation of cerebral oxygen saturation are important factors that affect the outcomes and the incidence of delirium in septic shock patients, which should be paid attention to in clinical practice. Dynamic monitoring of cerebral oxygen saturation and maintain its stability may be of great significance in patients with septic shock.