Abstract
Significance: Intracranial pressure (ICP), variability in perfusion, and resulting ischemia are leading causes of secondary brain injury in patients treated in the neurointensive care unit. Continuous, accurate monitoring of cerebral blood flow (CBF) and ICP guide intervention and ultimately reduce morbidity and mortality. Currently, only invasive tools are used to monitor patients at high risk for intracranial hypertension.Aim: Diffuse correlation spectroscopy (DCS), a noninvasive near-infrared optical technique, is emerging as a possible method for continuous monitoring of CBF and critical closing pressure (CrCP or zero-flow pressure), a parameter directly related to ICP.Approach: We optimized DCS hardware and algorithms for the quantification of CrCP. Toward its clinical translation, we validated the DCS estimates of cerebral blood flow index () and CrCP in ischemic stroke patients with respect to simultaneously acquired transcranial Doppler ultrasound (TCD) cerebral blood flow velocity (CBFV) and CrCP.Results: We found CrCP derived from DCS and TCD were highly linearly correlated (ipsilateral , ; contralateral , ). We found weaker correlations between and CBFV (ipsilateral , ; contralateral , ) probably due to the different vasculature measured.Conclusion: Our results suggest DCS is a valid alternative to TCD for continuous monitoring of CrCP.
Highlights
In the healthy brain, and under normal intracranial pressure (ICP), cerebral autoregulation ensures that adequate constant cerebral blood flow (CBF) is maintained over a wide range of arterial blood pressures (ABP).[1,2] in patients suffering from conditions as shock, stroke, cerebral edema, or traumatic brain injury, their cerebral autoregulation can be impaired such that changes in ABP may lead to cerebral hyperperfusion, hypoperfusion, and ischemia.[3]
Variables were tested for normality and were found normal (Kolmogorov–Smirnov: pulsatile cerebral blood flow index (pCBFi) D 1⁄4 0.11, p 1⁄4 0.94; ipsilateral pCBFV D 1⁄4 0.20 p 1⁄4 0.41, contralateral pCBFV D 1⁄4 0.19, p 1⁄4 0.45; pABP D 1⁄4 0.16, p 1⁄4 0.64)
While cerebrovascular resistance (CVR) across modality did not correlate, we found a strong correlation between CVRDCS and CPPDCS, defined as mean arterial blood pressure (MAP)-CrCPDCS
Summary
Under normal intracranial pressure (ICP), cerebral autoregulation ensures that adequate constant cerebral blood flow (CBF) is maintained over a wide range of arterial blood pressures (ABP).[1,2] in patients suffering from conditions as shock, stroke, cerebral edema, or traumatic brain injury, their cerebral autoregulation can be impaired such that changes in ABP may lead to cerebral hyperperfusion, hypoperfusion, and ischemia.[3]. Continuous monitoring of CBF and ICP is needed to optimize the management of critically ill neurointensive care unit (Neuro-ICU) patients and reduce morbidity and mortality.[7,8] Current gold standard techniques for CBF and ICP continuous monitoring are invasive, requiring surgical insertion of an intracranial catheter through a hole drilled into the skull.[9] Because of the invasiveness of the methods and the associated risks of hemorrhage and infection, ICP and CBF monitoring are not done for diagnosis, but only for clinical management in a limited patient population, in cases at high risk for intracranial hypertension.[10,11] Development of noninvasive monitoring of CBF and ICP will avoid the complications of invasive monitoring in high-risk patients and will allow inclusion of patients whose risk may be substantial but not enough to justify the invasive procedure. Noninvasive measurements would aid in identifying patients who may need invasive monitoring and allow for monitoring patients in critical periods before an invasive sensor can be applied. The problem is that current experimental noninvasive ICP monitoring devices[12] are suboptimal, operator dependent, or not accurate enough
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