Optical monitoring of cerebral microcirculation in neurointensive care

Peter Rejmstad,Neda Haj-Hosseini,Karin Wårdell,Oscar Åneman

doi:10.1007/s11517-017-1725-8

Peter Rejmstad, Neda Haj-Hosseini + Show 2 more

Open Access

https://doi.org/10.1007/s11517-017-1725-8

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Abstract

Continuous optical monitoring of local cerebral microcirculation could benefit neurointensive care patients treated for subarachnoid hemorrhage (SAH). The aim of the study was to evaluate laser Doppler flowmetry (LDF) and diffuse reflectance spectroscopy (DRS) for long-term monitoring of brain microcirculation and oxygen saturation (SO2) in the neurointensive care unit (NICU). A fiber optic probe was designed for intraparenchymal use and connected to LDF and DRS for assessment of the local blood flow (perfusion and tissue reflectance (TLI)) and SO2 in the brain. The optically monitored parameters were compared with conventional NICU monitors and Xe-CT. The LDF signals were low with median and 25 to 75% interquartiles of perfusion = 70 (59 to 83) a.u. and TLI = 2.0 (1.0 to 2.4) a.u. and showed correlation with the NICU monitors in terms of heart rate. Median and interquartiles of SO2 were 17.4 (15.7 to 19.8) %. The lack of correlation between local perfusion and cerebral perfusion pressure indicated intact cerebral autoregulation. The systems were capable of monitoring both local perfusion and SO2 with stable signals in the NICU over 4 days. Further clinical studies are required to evaluate the optical systems’ potential for assessing the onset of secondary brain injury.

Highlights

Monitoring of local brain microcirculation and oxygenation saturation (SO2) is a clinical demand not yet fully addressed in neurointensive care
Cerebral blood flow (CBF) monitoring is especially important for patient groups treated for traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH) due to the increased risk of secondary insults coupled with high mortality [17, 38]
The laser Doppler flowmetry (LDF) and diffuse reflectance spectroscopy (DRS) systems were evaluated on one neurointensive care patient for a period of 4 days with stable signals

Summary

Introduction

Monitoring of local brain microcirculation and oxygenation saturation (SO2) is a clinical demand not yet fully addressed in neurointensive care. The vulnerability to local ischemia in patients is often detected at a late stage, sometimes in contradiction with ICP readings within the normal healthy range [27]. Oxygen microelectrodes such as the Licox® system are sometimes used for local oxygen assessment in the brain but have a relatively slow response time to changes [26]. The electrodes measure cerebral oxygen pressure (pO2) related to SO2 through the oxygen dissociation curve (ODC) Techniques such as jugular venous SO2 and blood flow monitoring give a general view of the systemic parameters of the brain but do not reflect regional impairments such as focal ischemia [33].

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