Correlation of rheoencephalography and laser Doppler flow: a rat study

Abstract

Measuring brain electrical impedance (rheoencephalography) is a potential technique for noninvasive, continuous neuro-monitoring of cerebral blood flow autoregulation in humans. In the present rat study, we compared changes in cerebral blood flow autoregulation during CO2 inhalation measured by rheoencephalography to changes measured by laser Doppler flowmetry, an invasive continuous monitoring modality. Our hypothesis was that both modalities would reflect cerebral blood flow autoregulation. Male Sprague-Dawley rats (n=28; 28 control and 82 CO2 challenges) were measured under anesthesia. The surgical preparation involved implantation of intracerebral REG electrodes and an LDF probe into the brain. Analog waveforms were stored in a computer. CO2 inhalation caused transient, simultaneous increases in the signals of both laser Doppler flow (171.99 ± 46.68 %) and rheoencephalography (329.88 ± 175.50%). These results showed a correlation between the two measured modalities; the area under the receiver operating characteristic curve was 0.8394. The similar results obtained by measurements made with laser Doppler flowmetry and rheoencephalography indicate that rheo-encephalography, like laser Doppler flowmetry, reflects cerebral blood flow autoregulation. Rheoencephalography therefore shows potential for use as a continuous neuro-monitoring technique.

A noninvasive, continuous brain monitoring method: rheoencephalography (REG)

“…CBF manipulations on rats ( Figure 6): Several groups were used for measuring REG pulse amplitude change during electrical stimulation, carotid clamping, hemorrhage, CO2 inhalation, vinpocetine injection. REG was compared to carotid flow, laser Doppler flow, ICP, SAP, and spreading depolarization (Bodo et al, 2003(Bodo et al, , 2004(Bodo et al, , 2010(Bodo et al, , 2016.…”

Thoracic, peripheral, and cerebral volume, circulatory and pressure responses to PEEP during simulated hemorrhage in a pig model: a case study

“…It was demonstrated that BOLD MRI can reflect an early impairment of cerebrovascular reserve after aneurysmal subarachnoid hemorrhage [ 77 ]. Since REG reflects CBF AR it is expected that will be able to reflect the same way the impairment of cerebrovascular reserve, tested by CO 2 inhalation; REG correlated well (AUC= 0.84 with p<0.0001) to laser Doppler flow during CO 2 inhalation [ 78 ].…”

“…Earlier studies [ 31 , 32 ] made an initial effort to establish pathophysiological correlates to REG [ 30 , 34 ] but did not mention CBF AR. Previous studies documented that REG reflects cerebrovascular reactivity [ 40 ], has a correlation to ICP [ 35 , 38 ], laser Doppler flow [ 39 ], carotid flow [ 40 ] and can be used for patient monitoring instead of ICP [ 42 ]. It was documented that REG indicated cerebral vasospasm before systemic reaction caused by complement activation/cytokine storm in pigs [ 42 ].…”