Real-Time Monitoring of Neurocritical Patients with Diffuse Optical Spectroscopies

Summary

Presented here is a protocol for non-invasively monitoring cerebral hemodynamics of neurocritical patients in real-time and at the bedside using diffuse optics. Specifically, the proposed protocol uses a hybrid diffuse optical systems to detect and display real-time information on cerebral oxygenation, cerebral blood flow and cerebral metabolism.

Abstract

Neurophysiological monitoring is an important goal in the treatment of neurocritical patients, as it may prevent secondary damage and directly impact morbidity and mortality rates. However, there is currently a lack of suitable non-invasive, real-time technologies for continuous monitoring of cerebral physiology at the bedside. Diffuse optical techniques have been proposed as a potential tool for bedside measurements of cerebral blood flow and cerebral oxygenation in case of neurocritical patients. Diffuse optical spectroscopies have been previously explored to monitor patients in several clinical scenarios ranging from neonatal monitoring to cerebrovascular interventions in adults. However, the feasibility of the technique to aid clinicians by providing real-time information at the bedside remains largely unaddressed. Here, we report the translation of a diffuse optical system for continuous real-time monitoring of cerebral blood flow, cerebral oxygenation, and cerebral oxygen metabolism during intensive care. The real-time feature of the instrument could enable treatment strategies based on patient-specific cerebral physiology rather than relying on surrogate metrics, such as arterial blood pressure. By providing real-time information on the cerebral circulation at different time scales with relatively cheap and portable instrumentation, this approach may be especially useful in low-budget hospitals, in remote areas and for monitoring in open fields (e.g., defense and sports).

Introduction

Most of the complications that lead to poor outcomes for critically ill neurologic patients are related to secondary injuries caused by cerebral hemodynamic impairments. Therefore, monitoring cerebral physiology of these patients may directly impact morbidity and mortality rates^{1,2,3,4,5,6,7}. Currently, however, there is no established clinical tool for the continuous real-time noninvasive monitoring of cerebral physiology in neurocr....

Protocol

The protocol was approved by the local committee of the University of Campinas (protocol number 56602516.2.0000.5404). Written informed consent was obtained from the patient or a legal representative prior to the measurements. We monitored patients that were admitted to the Clinics Hospital at the University of Campinas with a diagnosis of either ischemic stroke or a subarachnoid hemorrhage affecting the anterior circulation. Patients with ischemic strokes affecting the posterior circulation, patients with decompressive craniectomies due to elevated intracranial pressure and patients with other neurodegenerative diseases (dementia, Parkinson's or any other disease....

Results

Ideally, the normalized autocorrelation curves obtained with the DCS module should be approximately 1.5 at the zero delay-time extrapolation (when using single-mode fibers¹⁴), and the curves should decay to 1 at longer delay times. The curve should be smooth, and it should have a faster decay for the longer source-detector separations. An example of a good autocorrelation is shown in Figure 2A. Figure 2B shows an example of a bad auto-cor.......

Discussion

This paper presented a hybrid optical system that can provide real-time information about cerebral blood flow, cerebral oxygenation, and cerebral oxygen metabolism of neurocritical patients at the beside. The use of diffuse optical techniques had been previously addressed as a potential marker for non-invasive, bedside monitoring in clinical scenarios. A previous study focused on the clinical aspects and the feasibility of optical monitoring during hospitalization in the neuro-ICU through a case report^9.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3D Printer	Sethi3D	S2	3D-printer used to print the customizable probes
Arduino UNO	Arduino	UNO REV3	Microcontroller responsible to interleave the DCS and FD-DOS measurements
DCS Correlator	Correlator.com	Flex11-16ch	Component of the DCS module
DCS Dectectors IO Boards	Excelitas Technology	SPCM-AQ4C-IO	Component of the DCS module
DCS Detectors	Excelitas Technology	SPCM-AQ4C	Component of the DCS module
DCS Laser	CrystaLaser	DL785-120-SO	Component of the DCS module
DCS Power supply	Artesyn	UMP10T-S2A-S2A-S2A-S2A-IES-00-A	Component of the DCS module (power supply for the DCS detecto; 2, 5 and 30V)
FD-DOS fibers	ISS	Imagent supplies	The fibers used for FD-DOS detection and illumination are provived by ISS
Flexible 3D printer material	Sethi3D	NinjaFlex	Material used to print the flexible customizable probes
Imagent	ISS	Imagent	FD-DOS module
Laser safety googles	Thorlabs	LG9
Multi-mode fiber	Thorlabs	FT400EMT	Multi-mode fiber used for DCS illumination
Neutral density filter 1.0 OD	Edmund Optics	53-705	Neutral density filter for the short source detector separations
Single-mode optical fiber	Thorlabs	780HP	Single-mode optical fiber used for the DCS detectors
System battery	SMS	NET4	System battery used for transportation