A Comprehensive Review of Cerebral Oximetry in Cardiac Surgery

Background: Patients who undergo cardiac surgery are at increased risk of stroke, postoperative cognitive decline, and delirium. These neurocognitive complications have led to increased costs, intensive care unit stays, morbidity, and mortality. As a result, there is a significant push to mitigate any neurological complications in cardiac surgery patients. Near-infrared spectroscopy to measure regional cerebral oxygen saturations has gained consideration due to its non-invasive, user-friendly, and relatively inexpensive nature. Aim of Study: To provide a comprehensive summary of cerebral oximetry in cardiac surgery. The review interrogates multiple systematic reviews assessing different outcomes in cardiac surgery to assess if cerebral oximetry is effective. Further, the review analyzes all available interventions for an acute desaturation to determine the efficacy of individual interventions. Methods: A narrative review of randomized controlled trials, observational studies, and systematic reviews with metanalyses were performed through August 2021. Results: There is significant heterogeneity amongst studies regarding the definition of a clinically significant cerebral desaturation. In addition, the assessment of neurocognitive outcomes has large variability, making metanalysis challenging. To date, cerebral oximetry use during cardiac surgery has not been associated with improvements in neurocognitive outcomes, morbidity, or mortality. The evidence to support particular interventions for an acute desaturation is equivocal. Conclusions: Future research is needed to quantify a clinically significant cerebral desaturation and to determine which interventions for an acute desaturation effectively improve clinical outcomes.

Relationship Between Intraoperative Cerebral Desaturation and Postoperative Complications In Pediatric Patients Undergoing Congenital Heart Surgery: Prospective Cohort Study

Objective: In this study, we aimed to investigate the incidence of cerebral desaturation and the possible relationship between intraoperative cerebral desaturation and postoperative complications. Methods: A prospective, observational study was performed 115 patients under 18 years of age who required open heart surgery in a university hospital. Cerebral desaturation was defined as a 25% decrease in cerebral saturation (low alarm limit) when compared with the basal value. Duration (second) was referred to the amount of time the patient stays below low alarm limit. Depth (%) was referred to gap between the patient’s cerebral regional oxygen saturation (rSO2) level and the rSO2 low alarm limit. The cerebral desaturation score was calculated using the %*seconds. The patients were divided into two groups: group 1 (desaturation score >3000 %sec) and group 2 (desaturation score ≤ 3000 %sec). The groups were compared in terms of demographic data, intraoperative and postoperative variables, postoperative complications, and duration of intensive care and hospital stays. Results: In the study, 59 patients (51.3%) were male and 28 patients (24.3%) had cyanotic heart disease. A total of 55 patients (47.8%) experienced over 3000 %sec desaturation. Postoperative complications were found to be increased in group 1 (71% vs 3.3%; χ²=57.119, p<0.001). In the multiple logistic regression analysis, desaturation score>3000 %sec (p<0.001), low body surface area (p=0.001) and prolonged cardiopulmonary bypass (p=0.006) were found to be associated with postoperative complications. Conclusion: In patients undergoing congenital heart surgery, cerebral desaturation score >3000 %sec is associated with a negative effect on patient prognosis.

Assessment of Systemic and Cerebral Oxygen Saturation during Diagnostic Bronchoscopy: A Prospective, Randomized Study

Background. Arterial hypoxemia occurs in about 2.5–69% of cases during fiberoptic bronchoscopy and may necessitate administration of supplemental oxygen. Whether routine supplementary administration is indicated for all patients is a debated issue. In this prospective randomized study, we assessed the incidence of systemic desaturation (SpO2 <90% or a >4% decrease lasting for more than 60 s) and wanted to find out whether cerebral desaturation occurs in parallel with systemic changes. Patients and Methods. 92 consecutive patients scheduled for diagnostic bronchoscopy were randomly assigned to the no oxygen (O2- group), 2 l/min supplemental O2, or 4 l/min supplemental O2 groups. Primary end points were systemic and cerebral desaturation rate during the procedure. Secondary end points were to delineate the main risk factors of systemic and cerebral desaturation. Results. In the entire cohort, systemic desaturation occurred in 18.5% of patients (n = 17), corresponding to 5 patients (16%) in the O2 (−)group, 6 patients (19%) in the 2 l/min group, and 6 patients (20%) in 4 l/min group, respectively. In the O2 (−) group, the probability of desaturation was 41.7 times higher than that in the 2 l/min group ( p = 0.014 s), while there was no difference in the probabilities of desaturation between the 2 l/min and 4 l/min groups ( p = 0.22 ). Cerebral desaturation (more than 20% rSO2 decrease compared to baseline) did not occur in any patients in the three groups. Systemic desaturation developed earlier, and recovery after desaturation was longer in the O2 (−) group. Male gender, smoking, and systemic oxygen saturation at baseline and FEV1% were the most significant factors contributing to systemic desaturation during bronchoscopy. Conclusions. Administration of supplemental oxygen does not prevent systemic desaturation during flexible bronchoscopy, but may contribute to the shortening of desaturation episodes and faster normalization of oxygen saturation. According to our results, 2 l/min supplemental oxygen should routinely be administered to patients throughout the procedure. This trial is registered with NCT04002609

Effects of hypothermia, hypoxia and hypercapnia on brain oxygenation and haemodynamic parameters during simulated avalanche burial - a porcine study

Avalanche patients who are completely buried but still able to breathe are exposed to hypothermia, hypoxia and hypercapnia (triple H syndrome). Little is known about how these pathologic changes affect brain physiology. Study aim was to investigate the effect of hypothermia, hypoxia and hypercapnia on brain oxygenation and systemic and cerebral haemodynamics. Anaesthetised pigs were surface-cooled to 28°C. Inspiratory oxygen (FiO2) was reduced to 17% and hypercapnia induced. Haemodynamic parameters and blood gas values were monitored. Cerebral measurements included cerebral perfusion pressure (CPP), brain tissue oxygen tension (PbtO2), cerebral venous oxygen saturation (ScvO2) and regional cerebral oxygenation saturation (rSO2). Tests were interrupted when haemodynamic instability occurred or 60 min after hypercapnia induction. ANOVA for repeated measures was used to compare values across phases. There was no clinically relevant reduction in cerebral oxygenation (PbtO2, ScvO2, rSO2) during hypothermia and initial FiO2 reduction. Hypercapnia was associated with an increase in pulmonary resistance followed by a decrease in cardiac output and CPP, resulting in haemodynamic instability and cerebral desaturation (decrease in PbtO2, ScvO2, rSO2). Hypercapnia may be the main cause of cardiovascular instability, which seems to be the major trigger for a decrease in cerebral oxygenation in triple H syndrome despite severe hypothermia.