**Author details**

*Advancement and New Understanding in Brain Injury*

extracranial circulation [72].

in turn compromise CPP.

primary or systemic diseases that affect the CNS.

are essential to ensure that the best results will be achieved.

**8. Conclusion**

**9. Last words**

reaches values greater than 95% and specificity of 100% [50].

due to the advantages of being noninvasive, of being performed at the bedside and of allowing repetition, if necessary38. TCD sensitivity for brain death diagnosis

TCD should show no bilateral blood flow in the arteries of the intracranial carotid system and the vertebro-basilar system under normal body temperature conditions for at least 30 minutes. The criteria are: 1) presence of oscillatory flow (systolic velocity equal to reverse diastolic velocity – final flow zero) or 2) systolic spikes or 3) disappearance of intracranial flow with typical signs observed in the

Cerebral circulatory changes are often found in ICU daily practice and can lead to secondary tissue damage. Hypoxia, ischemia, intracranial hypertension, traumatic brain injury, stroke, kidney or liver failure, and sepsis can impair CAR. Since CAR mechanisms have been impaired, CBF passively follows MAP changes, which

A number of factors can influence the CBF and its regulation, so the monitoring and control of these factors by TCD can help adjust CBF to brain metabolic demands. TCD has the advantage of allowing bedside access to brain hemodynamic modifications, whether intermittent or serial and continuous monitoring. The disadvantage of the method is given by operator dependence and intensive training requirement, so that it can be applied in practice by physicians with clinical expertise in various

Noninvasive methods represent an advance in patient management, and will be increasingly present in hospitals. Understanding and proper use of these methods

**112**

Gustavo Frigieri1 \*, Nicollas Nunes Rabelo2 , Ricardo de Carvalho Nogueira3 and Sérgio Brasil<sup>2</sup>

1 Brain4care - Scientific Department, São Paulo, Brazil

2 Department of Neurology, University of São Paulo, São Paulo, Brazil

3 Laboratory of Neurosonology and Cerebral Hemodynamics - Division of Neurosurgery, Department of Neurology, School of Medicine, University of São Paulo, Brazil

\*Address all correspondence to: gustavo.frigieri@brain4.care

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
