Near-infrared spectroscopy (NIRS) has gained recognition in monitoring various organs, including the central nervous system. Research on NIRS has demonstrated the possibility of using it for quantifying cerebral blood flow and cerebral blood volume, making NIRS technology more appealing for real-time monitoring, in particular in the acute care setting. The most common applications of NIRS for cerebral monitoring include subarachnoid haemorrhage, TBI, carotid endarterectomy, cardiac surgery, as well as liver transplantation. ICM+ allows the continuous monitoring of NIRS parameters in the context of multimodal brain monitoring.

Cerebral autoregulation

 

NIRS has been extensively studied for the monitoring of cerebral autoregulation both in clinical, as well as experimental studies. Recent research has demonstrated that autoregulation indices based on NIRS parameters were highly correlated with those calculated with TCD or ICP. 

Blood pressure-flow velocity and blood pressure-tissue oxygenation index

Monitoring data from a patient with SAH on day 5 post-ictus. High coherence between ABP and FV as well as between ABP and TOI (black arrow). ABP – arterial blood pressure; FV – flow velocity; SAH – subarachnoid haemorrhage; TOI – tissue oxygenation index obtained with NIRS. View image

The correlation coefficient method for calculating cerebral autoregulation
A. A negative correlation is representative of an active system and functioning autoregulation. B. A positive correlation is representative of a passive system and impaired autoregulation. In both (A and B) and similar behaviour of FV and TOI can be seen. ABP-arterial blood pressure; FV-flow velocity; Mxa-transcranial Doppler based autoregulation index; TOI-tissue oxygenation index; TOxa-nearinfrared spectroscopy based autoregulation index.
Multimodal assessment of autoregulation
Example of monitoring performed on day 5 post-ictus. The middle panel shows impaired autoregulation using Sxa (black line), TOxa (grey line) and THRT (insert). There is a relatively good correlation between Sxa and TOxa (r=0.68). The patient developed delayed cerebral ischemia on day 9. ABP-arterial blood pressure; Sxa-systolic flow index; THRT-transient hyperaemic response test; TOxa-TOI based index.

Selected references

 

Cerebral Autoregulation