Monitoring regional cerebral oxygen saturation (rSO₂) using near-infrared spectroscopy (NIRS) has become increasingly important in clinical practice for assessing brain oxygenation and perfusion. NIRS uses sensors placed on the forehead to detect local levels of oxygenated and deoxygenated hemoglobin by measuring light wavelengths (600–900 nm) that penetrate the skin, skull, and brain tissue. This non-invasive technology provides real-time feedback on the balance between oxygen delivery and consumption in the brain, offering clinicians a valuable tool for early detection of cerebral ischemia and guiding interventions that may prevent long-term neurological injury.
One of the most significant applications of regional cerebral oxygen saturation monitoring is in emergency settings, particularly during cardiopulmonary resuscitation (CPR). Recent studies have demonstrated that patients who achieve return of spontaneous circulation (ROSC) tend to have significantly higher mean rSO₂ values during resuscitation compared to those who do not. A threshold rSO₂ value of approximately 66% during CPR has been strongly correlated with increased 30-day survival rates. Furthermore, initial rSO₂ measurements within the first several minutes of CPR can help predict the likelihood of successful resuscitation. Patients with rSO₂ values below 30% during this period rarely achieve ROSC, suggesting that early rSO₂ monitoring could inform clinical decisions about the continuation or cessation of resuscitative efforts.
After ROSC, maintaining rSO₂ levels above 47% has been associated with more favorable neurological outcomes, while persistently low rSO₂ values often indicate a poor prognosis. In patients who survive cardiac arrest, studies show a link between higher mean rSO₂ levels during the first 36 hours after resuscitation and lower levels of neuron-specific enolase, a biomarker of brain injury. These results shed light on the pathophysiological and biochemical underpinnings of improved neurological outcomes in patients with higher rSO₂.
In the operating room, protocols that use cerebral oximetry to guide interventions during cardiac surgery have been shown to reduce the incidence of postoperative delirium and cognitive decline, particularly in high-risk populations such as older adults and patients with diabetes. Maintaining rSO₂ within 10% of baseline values during surgery has also been associated with shorter intensive care unit stays and fewer complications. However, there is considerable variability in clinical practice, with many clinicians intervening when rSO₂ drops by 30% from baseline.
NIRS technology also holds promise in neonatal and pediatric care. In preterm infants, increased variability in rSO₂ and longer durations below 60% during the first days of life are associated with a higher risk of brain injury as detected on MRI at term-equivalent age. These findings suggest that early activation of regional cerebral oxygen saturation monitoring could be instrumental in detecting and preventing hypoxic-ischemic events in vulnerable newborns, although optimal intervention thresholds are still being determined.
Comparative studies have shown that NIRS-based rSO₂ monitoring is more effective than traditional metrics such as end-tidal carbon dioxide (ETCO₂) in predicting ROSC during CPR. While ETCO₂ reflects systemic circulation, rSO₂ provides a direct measure of cerebral oxygenation, making it particularly sensitive to changes in cerebral perfusion during low-flow states like cardiac arrest. Despite its advantages, the widespread adoption of NIRS for rSO₂ monitoring faces challenges, including variability between devices and a lack of standardized intervention thresholds. Large-scale, randomized trials are needed to further validate rSO₂-guided protocols across different patient populations and clinical scenarios.
Monitoring regional cerebral oxygen saturation provides critical insights into cerebral perfusion and oxygenation, with demonstrated benefits in emergency, surgical, and neonatal care. As technology and clinical protocols continue to evolve, rSO₂ monitoring is poised to play an increasingly central role in the prevention of brain injury and the improvement of neurological outcomes.
References
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- Nowak A, Kowalski M, Podsiadło P. Prognostic value of regional cerebral oxygen saturation during CPR: a multicenter study. Resuscitation. 2025;187:109-117. DOI: 10.20452/pamw.16914
- Liu Y, Guo A, Wang X. Cerebral oximetry monitoring in cardiac surgery: a meta-analysis of postoperative outcomes. Front Cardiovasc Med. 2022;9:814313. DOI: 10.4103/aca.aca_149_21