Optimal cerebral perfusion pressure via transcranial Doppler in TBI:application of robotic technology
作者：Frederick A. Zeiler & Marek Czosnyka & Peter Smielewski
2018年9月29日，剑桥大学Marek Czosnyka教授等人在最新一期的《Acta Neurochirurgica》发表最新研究：通过采用自动探头，可以获得危重TBI患者的长程脑血流记录，从而获得基于TCD脑血管反应指数的接近最优的脑灌注压。随着自动探头技术的不断进步，更长的记录成为可能，人员工时投入减少，TBI患者使用连续无间断的TCD监测将成为神经多模态监测的标准配置。
Individualized cerebral perfusion pressure (CPP) targets may be derived via assessing the minimum of the parabolic relationship between an index of cerebrovascular reactivity and CPP. This minimum is termed the optimal CPP (CPPopt), and literature suggests that the further away CPP is from CPPopt, the worse is clinical outcome in adult traumatic brain injury (TBI). Typically,CPPopt estimation is based on intracranial pressure (ICP)-derived cerebrovascular reactivity indices, given ICP is commonly measured and provides continuous long duration data streams. The goal of this study is to describe for the first time the application of robotic transcranial Doppler (TCD) and the feasibility of determining CPPopt based on TCD autoregulation indices.
Continuous monitoring of cerebrovascular reactivity in traumatic brain injury (TBI) is becoming increasingly common in
the multi-modal monitoring (MMM) of critically ill patients [10, 11, 16]. To date, support for such monitoring has arisen
within international consensus statements [10, 16]. Such support is centered on what is considered the Bgold standard^
continuous index, pressure reactivity index (PRx—correlation between intracranial pressure (ICP) and mean arterial pressure (MAP)) , given its association with global outcome in TBI and validation in experimental animal models against the lower limit of autoregulation [4, 23, 32]. Furthermore, literature supports the association of PRx-derived Bpersonalized^cerebral perfusion pressure (CPP) targets (referred to as CPP optimum or CPPopt) and global outcome .Numerous other continuous indices of cerebrovascular reactivity exist in the TBI literature [31, 32], derived from other invasive and non-invasive monitoring devices, including transcranial Doppler (TCD)-based measures. Indices based on TCD mean flow velocity (FVm) and systolic flow velocity (FVs) have been linked to global outcome in adult TBI [6, 22] and are known to be reasonably strongly associated with ICPderived indices, such as PRx [30, 33].
Various signals were obtained through a combination of invasive and non-invasive methods. Arterial blood pressure (ABP) was
obtained through either radial or femoral arterial lines connected to pressure transducers (Baxter Healthcare Corp.CardioVascular Group, Irvine, CA). ICP was acquired via an intra-parenchymal strain gauge probe (Codman ICP MicroSensor; Codman & Shurtleff Inc., Raynham, MA). Zeroing of the arterial line occurred at the level of the tragus during the course of this study.
Finally, TCD assessment of MCA CBFV was conducted via a robotic TCD system, the Delica EMS 9D (Delica, Shenzhen, China, http://www.delicasz.com/html/en). This system allows for continuous extended duration recording of MCA CBFV, using 1.6 MHz robotically controlled TCD probes, with automated correction algorithms for probe shift.We aimed to record 3 to 4 h of continuous data from all devices simultaneously, given the previous work from our group on inter-index relationships focused on recording durations of only 0.5- to 1-h duration due to limitations of conventional TCD [22, 30]. Based on manufacturer specifications of the Delica robotic TCD system, the thermal index for the 1.6 MHz Doppler probes is less than 1.0, with the index less than 0.5 in most cases. As such, in keeping with the guidelines for adult TCD provided by the British Medical Ultrasound Society, the thermal index for the device is in the range acceptable for potentially Bunlimited^ TCD duration, while adhering to the principles of Bas low as reasonably achievable^(ALARA) [5, 12, 13]. Thus, there were no concerns with tissue heating as a result of the extended duration recordings using this system. Brain temperature, local or global, was not recorded in this patient cohort. Figure 1 displays the robotic TCD device and set up for recording in critical ill TBI patients.……