Ebook Neurocritical care monitoring: Part 2
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Ebook Neurocritical care monitoring: Part 2
Cerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2alion.The extent of this impairment may fluctuate with time. A repeatable non invasive method of monitoring of aulorcgulalory reserve is needed.If aulorcgulalion is altered, it decreases the range of cerebral perfusion pressure (CPP) that ensures adequate cerebral blood flow (CBF) as it becomes pres Ebook Neurocritical care monitoring: Part 2sure passive, lite risk of cerebral hypoperfusion ischemia (1.2), or hyperemia, edema, and cerebral bleeding increases (3). Patients with severe brainEbook Neurocritical care monitoring: Part 2
injury and impaired cerebral aulorcgulation have poor outcome (4).Several modalities are frequently used for monitoring cerebral autoregulation. TheyCerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2 ultrasonography has the ability to continuously assess the autoregulatory reserve.The versatility of TCD has encouraged imaginative applications in head-injured patients, allowing both dynamic and static tests to be evaluated in the clinical setting (5-7).Static Test of AutoregulationMethods for th Ebook Neurocritical care monitoring: Part 2e static assessment of autoregulation rely on observing middle cerebral artery (MCA) blood flow velocity (FV) during changes in mean arterial blood prEbook Neurocritical care monitoring: Part 2
essure (ABP) induced by an infusion of vasopressor (Figure 7.1). The static rale of autoregulation (SRoR) can be calculated as the percentage increaseCerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2y depleted autoregulation. The test is potentially prone to8586 Neurocritical Care MonitoringSRoR = [(CCPi/FVi-cpP2jFV2)/(CCPi.'FVi)n(CCPi-cpP2).'CCPi]-ioo%[(eo'tsa - 82/40y(6Q''38)j/Ị(6O-82).'60Ì,10ơíi» = 81%FIGURE 7.1 Example of measurement of SRoR in a TBI patient. ABP has been raised with norepi Ebook Neurocritical care monitoring: Part 2nephrine. Baseline values (index 1) were compared with values recorded after elevation of ABP by 19 mmHg (index 2). SRoR has been calculated as relatiEbook Neurocritical care monitoring: Part 2
ve increase in CVR (CPP/FV, where FV was mean blood FV in the MCA and CPP) divided by relative increase in CPP (see formula under the graph). In this Cerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2cg-ulation, when only changes in arterial pressure (not CPP) are used for the calculation (9).Transcranial Doppler Reactivity to Changes in Carbon Dioxide Concentration (10)Testing for CO2 cerebrovascular reactivity has been shown to have an important application in the assessment of severely head-i Ebook Neurocritical care monitoring: Part 2njured patients as well as other cerebrovascular diseases. Although many authors have demonstrated that cerebral vessels are reactive to changes in coEbook Neurocritical care monitoring: Part 2
, when cerebral autoregulation had been already impaired (II). co, reactivity correlates significantly with outcome following head injury (11-13). TheCerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2acranial pressure (1CP) (14.15). Therefore, this method cannot be used without consideration of patient safety, particularly if baseline 1CP is already elevated. Brief induction of mild hypocapnia (above 4.5 kPa or .34 mmHg) is safer than induction of hypercapnia (Figure 7.2; 16). Also, changes in m Ebook Neurocritical care monitoring: Part 2ean arterial pressure (MAP), induced by change in PaCO,. should be accounted for while calculating reactivity (17). Normal reactivity should stay abovEbook Neurocritical care monitoring: Part 2
e 15% per kPa (7.5 mmHg) change in PaCO,.Thigh Cuff TestAaslid described a method in which a step-wise decrease in ABP was achieved by the deflation oCerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2escribes how quickly cerebral vessels react to the sudden fall in blood pressure. The RoR was proposed7: Cerebral Autoregulation ■ tí/PaCO2 = 5.6 kPaPaCO; = 4.9 kPaFVL1 = 41 cm/sFVL2 ss 33 cnVsFVR1 = 57 cm/sGV IfclO GV licit, (M)1tc20 &v IM!V GV 15:30Ebook Neurocritical care monitoring: Part 2
vel of mild hypocapnia by increasing FiO,. Decrease in mean FV and a slight decrease in ICP were noted. Calculated CO, reactivity was very good at botCerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2oregulation (index of autoregulation = 6):When following decrease in ABP the flow velocity first decreased but compensatory (autoregulation-mediated) rise was seen very soon. Deteriorated autoregulation is presented in the right panel: With thanks to Prof. L. Steiner. An initial decrease in flow vel Ebook Neurocritical care monitoring: Part 2ocity was sustained (ARI = 3).to express the autoregulatory reserve, and was subsequently shown to correlate with blood co, concentration in volunteerEbook Neurocritical care monitoring: Part 2
s and with static rate of autoregulation. Index of autoregulation (ARI) (graded from O-impaired autoregulation, to 9-intact autoregulation) was introdCerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgula Ebook Neurocritical care monitoring: Part 2aries with rapid changes in arterial pressure according to the state of the cerebral autoregulation (20-22).88 Neurocritical Care MonitoringTransient Hyperaemic Response Test Ebook Neurocritical care monitoring: Part 2Cerebral AutoregulationMarek Czosnyka, PhD Enrique Carrero Cardenal, PhDINTRODUCTIONPatients with brain injuries may have impaired cerebral aulorcgulaGọi ngay
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