Abstract:
Neonates, particularly preterm infants, maintain a delicate balance between oxygen supply and consumption due to their underdeveloped organs. Ensuring normoxia in premature infants is crucial, given their immature antioxidant systems. Furthermore, neonatologists still face uncertainty regarding optimal oxygen saturation ranges, as increasing evidence suggests these parameters vary with gestational age, postnatal age, and underlying pathologies.
The advent of novel monitoring technologies has led to improved neonatal survival and reduced morbidity. However, neurodevelopmental outcomes remain a challenge. Key postnatal neuroprotection strategies include minimal handling, oxidative stress management, and optimisation of cerebral oxygenation. Transitioning from routine to proactive neuromonitoring systems can play a pivotal role in detecting and preventing neurological damage by optimising cerebral perfusion and oxygenation, carefully titrating inotropes, and detecting seizures or complications arising from clinical care. Multimodal monitoring has the potential not only to identify established brain injury but also to elucidate its pathophysiological mechanisms. It enables early recognition of brain injury, facilitating timely therapeutic intervention. However, the use of neuromonitoring, neuroimaging, and neurodevelopmental assessments in the NICU remains highly heterogeneous.
Discussion: Pulse oximetry provides an assessment of systemic oxygen supply, whereas regional oximetry evaluates oxygen saturation in specific tissue regions. However, pulse oximetry alone lacks the sensitivity required for individualised oxygen management in this highly vulnerable population, which is at significant risk of both hypoxia and hyperoxia. Near-Infrared Spectroscopy (NIRS) represents a significant advancement in personalised medicine by enabling continuous, non-invasive monitoring that offers detailed insights into the balance between oxygen supply and consumption. By detecting early stages of hypoperfusion and oxygen imbalance, NIRS provides opportunities for intervention before irreversible damage occurs.
NIRS is the most widely used neuromonitoring system, providing valuable guidance during preoperative, intraoperative, and postoperative periods. It allows for the monitoring of regional tissue oxygenation at both cerebral and somatic levels. This non-invasive system utilises near-infrared light emission (700–1000 nm) to detect changes in light attenuation as it passes through tissues, which are absorbed by oxygen-dependent chromophores such as oxyhaemoglobin and deoxyhaemoglobin. NIRS reflects 70% of the venous component and 30% of the arterial component. Correlation with central venous saturation is enhanced by various somatic sensors, enabling early detection of declines in left cardiac output.
In addition to pulse oximetry, NIRS monitors the balance between oxygen supply and uptake, detecting both hypoxia and hyperoxia and thus preventing harmful dysoxia. The immediacy of its measurements and rapid responsiveness to haemodynamic and oxygenation changes make NIRS an essential tool in operating theatres. Its first reported use in coronary artery bypass surgery in 1991 by Greeley et al. demonstrated its clinical relevance. When absolute ScO? values fall below 50% or decrease by more than 20% from baseline, potential causes must be ruled out, including inadvertent hyperventilation, paradoxical embolism, cannula malposition, and conditions that increase cerebral metabolic demand, such as subclinical seizures or hyperthermia. Additional measures include optimising analgesia and sedation and monitoring SvO? and haematocrit levels. Postoperatively, the absence of NIRS desaturations has been correlated with sequela-free survival. Furthermore, cerebral oxygenation can predict in-hospital mortality after ECMO and, in cases of impending cardiac arrest, a 10% increase in the SpO?–rSO? difference has been associated with a 40% increased risk of cardiac arrest.
Despite its advantages, NIRS has certain limitations, including variability in the contribution of different vascular beds, the stability of NIRS values, the size of the scanned area, the lack of a direct reference for correlation, and interindividual and intraindividual variability. Additionally, haemoglobin levels influence NIRS readings. Cerebral oximetry alone is insufficient to estimate cerebrovascular autoregulatory function; however, when a strong correlation between cerebral oxygenation and arterial blood pressure is observed, autoregulation is likely impaired.
Conclusion: By combining pulse oximetry and NIRS, oxygen extraction (OEF/FTOE) can be calculated, providing a more detailed understanding of the balance between oxygen supply and consumption. These metrics complement pulse and regional oximetry, offering higher specificity and lower interindividual variability. In preterm infants, FTOE monitoring guides critical interventions and improves clinical decision-making efficiency, potentially reducing the costs associated with preventable complications such as inappropriate oxygen administration and transfusions. This approach minimises the risks of both hyperoxia and hypoxia, ultimately improving neonatal outcomes.
