Publications by authors named "Magdalena Kasprowicz"

62 Publications

Serum biomarkers and cerebral autoregulation as early warnings of delayed cerebral ischemia risk in patients after aneurysmal subarachnoid haemorrhage.

J Clin Neurosci 2021 May 9;87:35-43. Epub 2021 Mar 9.

Department of Anaesthesiology and Intensive Care, Wroclaw Medical University, Wroclaw, Poland.

Background: Identifying patients at risk of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid haemorrhage (aSAH) remains challenging. This study aimed to evaluate the concentration of serum biomarkers along with cerebral autoregulation impairment on DCI.

Methods: 55 patients suffering from aSAH were enrolled in the study. Serum S100protein B (S100B) was tested both on the day of admission and over three consecutive days following the occurrence of aSAH. Cerebral autoregulation was assessed using a tissue oxygenation index (TOxa) based on near-infrared spectroscopy.

Results: Changes in serum S100B levels interacted with DCI status (presence vs. absence): F = 3.84, p = 0.016. Patients with DCI had higher S100B concentration level on day 3 than those without DCI (3.54 ± 0.50 ng/ml vs. 0.58 ± 0.43 ng/ml, p = 0.001). S100B concentration on day 3 following aSAH predicted DCI (AUC = 0.77, p = 0.006). Raised level of serum S100B on day 3 was related with higher TOxa, thus with impaired cerebral autoregulation (r = 0.52,p = 0.031). Multivariate logistic regression analysis showed thatimpaired cerebral autoregulation andelevatedS100B concentration on day 3 increasethe likelihood of DCI.

Conclusions: Tracking changes in the serum biomarkers concentration along with monitoring of cerebral autoregulation, may play a role in early detection of patients at risk of DCI after aSAH. These results need to be validated in larger prospective cohorts.
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http://dx.doi.org/10.1016/j.jocn.2021.02.009DOI Listing
May 2021

Compliance of the cerebrospinal space: comparison of three methods.

Acta Neurochir (Wien) 2021 Apr 14. Epub 2021 Apr 14.

Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.

Background: Cerebrospinal compliance describes the ability of the cerebrospinal space to buffer changes in volume. Diminished compliance is associated with increased risk of potentially threatening increases in intracranial pressure (ICP) when changes in cerebrospinal volume occur. However, despite various methods of estimation proposed so far, compliance is seldom used in clinical practice. This study aimed to compare three measures of cerebrospinal compliance.

Methods: ICP recordings from 36 normal-pressure hydrocephalus patients who underwent infusion tests with parallel recording of transcranial Doppler blood flow velocity were retrospectively analysed. Three methods were used to calculate compliance estimates during changes in the mean ICP induced by infusion of fluid into the cerebrospinal fluid space: (a) based on Marmarou's model of cerebrospinal fluid dynamics (C), (b) based on the evaluation of changes in cerebral arterial blood volume (C), and (c) based on the amplitudes of peaks P1 and P2 of ICP pulse waveform (C).

Results: Increase in ICP caused a significant decrease in all compliance estimates (p < 0.0001). Time courses of compliance estimators were strongly positively correlated with each other (group-averaged Spearman correlation coefficients: 0.94 [0.88-0.97] for C vs. C, 0.77 [0.63-0.91] for C vs. C, and 0.68 [0.48-0.91] for C vs. C).

Conclusions: Indirect methods, C and C, allow for the assessment of relative changes in cerebrospinal compliance and produce results exhibiting good correlation with the direct method of volumetric manipulation. This opens the possibility of monitoring relative changes in compliance continuously.
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http://dx.doi.org/10.1007/s00701-021-04834-yDOI Listing
April 2021

Cerebrovascular Impedance During Hemodynamic Change in Rabbits: A Pilot Study.

Acta Neurochir Suppl 2021 ;131:283-288

Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.

Introduction: Cerebrovascular impedance describes the relationship between pulsatile changes in arterial blood pressure (ABP) and cerebral blood flow (CBF). It is commonly defined by modulus and phase shift derived from Fourier spectra of ABP and CBF velocity (CBFV) signals under mostly steady-state conditions. The aim of this work was to assess heartbeat-to-heartbeat cerebrovascular impedance at heart rate frequency during controlled changes in mean ABP and intracranial pressure (ICP).

Material And Methods: Recordings of ABP in the femoral artery, transcranial Doppler CBFV in the basilar artery, and subarachnoid ICP were obtained from anesthetized rabbits with induced arterial hypotension (n = 8 rabbits), arterial hypertension (n = 5), or intracranial hypertension (n = 7). Modulus of cerebrovascular impedance (|Z|) was estimated from amplitudes of ABP and CBFV. Phase shift of cerebrovascular impedance (PS) was estimated from time-frequency (TF) representations of phase shift between ABP and CBFV overlaid with a time-variant mask based on the fundamental frequency of ABP.

Results: Both |Z| and PS increased with increasing mean ABP. |Z| decreased with increasing mean ICP, but no change was observed in PS.

Conclusions: The combined beat-to-beat and TF approach allows for the estimation of cerebrovascular impedance during transient hemodynamic changes. |Z| and PS follow the pattern of changes in CPP.
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http://dx.doi.org/10.1007/978-3-030-59436-7_53DOI Listing
January 2021

Analysis of Intracranial Pressure Pulse-Pressure Relationship: Experimental Validation.

Acta Neurochir Suppl 2021 ;131:279-282

Faculty of Electronics and Information Technology, Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland.

The slope of linear relationship between the amplitude of pulsations in intracranial pressure (ICP) versus mean ICP has recently been suggested as a useful guide for selecting patients for shunt surgery in normal pressure hydrocephalus (NPH). To better understand how the pathophysiology of cerebral circulation influences this parameter, we aimed to study the relationship between mean pressure and pulsation amplitude in a wide range of conditions affecting cerebrovascular tone and ICP in experimental conditions.We retrospectively analysed experimental material collected previously. Three physiological manoeuvres were studied in 29 New Zealand white rabbits: lumbar infusion with an infusion rate ≤0.2 mL/min to induce mild intracranial hypertension (n = 43), sympathetic blockade to induce arterial hypotension (n = 19), and modulation of the ventilator tidal volume, simultaneously influencing arterial carbon dioxide partial pressure (PaCO) to induce hypocapnia or hypercapnia (n = 17). We investigated whether the slope of the pulse amplitude (AMP)-ICP line depended on PaCO and arterial blood pressure (ABP) changes.We found a linear correlation between AMP-ICP and ICP with positive slope. Regression of slope against mean ABP showed a negative dependence (p = 0.03). In contrast, the relationship between slope and PaCO was positive, although not reaching statistical significance (p = 0.18).The slope of amplitude-pressure line is strongly modulated by systemic vascular variables and therefore should be taken as a descriptor of cerebrospinal fluid dynamics with great care.
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http://dx.doi.org/10.1007/978-3-030-59436-7_52DOI Listing
January 2021

Brain-Specific Biomarkers as Mortality Predictors after Aneurysmal Subarachnoid Haemorrhage.

J Clin Med 2020 Dec 20;9(12). Epub 2020 Dec 20.

Department of Anesthesiology and Intensive Therapy, Wroclaw Medical University, Borowska 213, 50-556 Wroclaw, Poland.

Aneurysmal subarachnoid haemorrhage (aSAH) is a serious condition with a high mortality and high permanent disability rate for those who survive the initial haemorrhage. The purpose of this study was to investigate markers specific to the central nervous system as potential in-hospital mortality predictors after aSAH. In patients with an external ventricular drain, enolase, S100B, and GFAP levels were measured in the blood and cerebrospinal fluid (CSF) on days 1, 2, and 3 after aSAH. Compared to survivors, non-survivors showed a significantly higher peak of S100B and enolase levels in the blood (S100B: 5.7 vs. 1.5 ng/mL, = 0.031; enolase: 6.1 vs. 1.4 ng/mL, = 0.011) and the CSF (S100B: 18.3 vs. 0.9 ng/mL, = 0.042; enolase: 109.2 vs. 6.1 ng/mL, = 0.015). Enolase showed the highest level of predictability at 1.8 ng/mL in the blood (AUC of 0.873) and 80.0 ng/mL in the CSF (AUC of 0.889). The predictive ability of S100B was also very good with a threshold of 5.7 ng/mL in the blood (AUC 0.825) and 4.5 ng/mL in the CSF (AUC 0.810). In conclusion, enolase and S100B, but not GFAP, might be suitable as biomarkers for the early prediction of in-hospital mortality after aSAH.
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http://dx.doi.org/10.3390/jcm9124117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7766120PMC
December 2020

A comparison of the time constant of the cerebral arterial bed using invasive and non-invasive arterial blood pressure measurements.

Physiol Meas 2020 08 11;41(7):075001. Epub 2020 Aug 11.

Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland.

Objective: The time constant of the cerebral arterial bed (τ), which is an index of brain haemodynamics, can be estimated in patients using continuous monitoring of arterial blood pressure (ABP), transcranial Doppler cerebral blood flow velocity (CBFV) and intracranial pressure (ICP) if these measures are available. But, in some clinical scenarios invasive measurement of ABP is not feasible. Therefore, in this study we aimed to investigate whether invasive ABP can be replaced with non-invasive ABP, monitored using the Finapres photoplethysmograph (fABP).

Approach: Forty-six recordings of ICP, ABP, fABP, and CBFV in the right and left middle cerebral arteries were performed daily for approximately 30 min in 10 head injury patients. Two modelling approaches (constant flow forward [CFF, pulsatile blood inflow and steady blood outflow] and pulsatile flow forward [PFF, where both blood inflow and outflow are pulsatile]) were applied to estimate τ using either invasive ABP (τ, τ) or non-invasive ABP (fτ, fτ).

Main Results: Bland-Altman analysis showed quite poor agreement between the fτ and τ methods of estimation. The fτ method produced significantly higher values than the τ method when calculated using both the CFF and PFF models (p < .001 for both). The correlation between fτ and τ was moderately high (r = 0.63; p < .001), whereas that between fτ and τ was weaker (r = 0.40; p = .009).

Significance: Our results suggest that using non-invasive ABP for estimation of τ is inaccurate in head injury patients.
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http://dx.doi.org/10.1088/1361-6579/ab9bb6DOI Listing
August 2020

Critical closing pressure during experimental intracranial hypertension: comparison of three calculation methods.

Neurol Res 2020 May 13;42(5):387-397. Epub 2020 Mar 13.

Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland.

: The critical closing pressure (CrCP) defines arterial blood pressure below which cerebral arteries collapse. It represents a clinically relevant parameter for the estimation of cerebrovascular tone. Although there are few methods to assess CrCP, there is no consensus which of them estimates this parameter most accurately. The aim of present retrospective, experimental study was to compare three methods of CrCP estimation: conventional Aaslid's formula and methods based on the cerebrovascular impedance: the established continuous flow forward (CFF) and a new pulsatile flow forward (PFF) model.: The effects of the following physiological manoeuvres on the CrCP were studied in New Zealand white rabbits: lumbar infusion of Hartmann's solution to induce mild intracranial hypertension, sympathetic blockade to induce arterial hypotension, and modulation of respiratory tidal volume to induce hypocapnia or hypercapnia.: During intracranial hypertension, all CrCP estimates were significantly higher than at baseline, decreased with decreasing ABP and increased with gradual hypocapnia. During hypercapnia, all CrCP estimates were significantly decreased but only in the case of CrCP the negative, non-physiological values were observed (16% of the cases). The Bland-Altman analysis revealed that a good agreement between each impedance method and Aaslid's method deteriorated significantly in the low range of the average numerical value of the estimates.: Our results confirm the limited usage of Aaslid's formula for the calculation of CrCP. Although both impedance methods seem to be equivalent, the fact that PFF model better describes cerebrovascular hemodynamic allows the recommendation of this model for the calculation of CrCP.
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http://dx.doi.org/10.1080/01616412.2020.1733323DOI Listing
May 2020

Feasibility of Hidden Markov Models for the Description of Time-Varying Physiologic State After Severe Traumatic Brain Injury.

Crit Care Med 2019 11;47(11):e880-e885

Division of Anesthesia, Department of Anesthesia, University of Cambridge, Cambridge, United Kingdom.

Objectives: Continuous assessment of physiology after traumatic brain injury is essential to prevent secondary brain insults. The present work aims at the development of a method for detecting physiologic states associated with the outcome from time-series physiologic measurements using a hidden Markov model.

Design: Unsupervised clustering of hourly values of intracranial pressure/cerebral perfusion pressure, the compensatory reserve index, and autoregulation status was attempted using a hidden Markov model. A ternary state variable was learned to classify the patient's physiologic state at any point in time into three categories ("good," "intermediate," or "poor") and determined the physiologic parameters associated with each state.

Setting: The proposed hidden Markov model was trained and applied on a large dataset (28,939 hr of data) using a stratified 20-fold cross-validation.

Patients: The data were collected from 379 traumatic brain injury patients admitted to Addenbrooke's Hospital, Cambridge between 2002 and 2016.

Interventions: Retrospective observational analysis.

Measurements And Main Results: Unsupervised training of the hidden Markov model yielded states characterized by intracranial pressure, cerebral perfusion pressure, compensatory reserve index, and autoregulation status that were physiologically plausible. The resulting classifier retained a dose-dependent prognostic ability. Dynamic analysis suggested that the hidden Markov model was stable over short periods of time consistent with typical timescales for traumatic brain injury pathogenesis.

Conclusions: To our knowledge, this is the first application of unsupervised learning to multidimensional time-series traumatic brain injury physiology. We demonstrated that clustering using a hidden Markov model can reduce a complex set of physiologic variables to a simple sequence of clinically plausible time-sensitive physiologic states while retaining prognostic information in a dose-dependent manner. Such states may provide a more natural and parsimonious basis for triggering intervention decisions.
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http://dx.doi.org/10.1097/CCM.0000000000003966DOI Listing
November 2019

The relationship between the time of cerebral desaturation episodes and outcome in aneurysmal subarachnoid haemorrhage: a preliminary study.

J Clin Monit Comput 2020 Aug 20;34(4):705-714. Epub 2019 Aug 20.

Department of Anesthesiology and Intensive Care, Wroclaw Medical University, Wroclaw, Poland.

In this preliminary study we investigated the relationship between the time of cerebral desaturation episodes (CDEs), the severity of the haemorrhage, and the short-term outcome in patients with aneurysmal subarachnoid haemorrhage (aSAH). Thirty eight patents diagnosed with aneurysmal subarachnoid haemorrhage were analysed in this study. Regional cerebral oxygenation (rSO) was assessed using near infrared spectroscopy (NIRS). A CDE was defined as rSO < 60% with a duration of at least 30 min. The severity of the aSAH was assessed using the Hunt and Hess scale and the short-term outcome was evaluated utilizing the Glasgow Outcome Scale. CDEs were found in 44% of the group. The total time of the CDEs and the time of the longest CDE on the contralateral side were longer in patients with severe versus moderate aSAH [h:min]: 8:15 (6:26-8:55) versus 1:24 (1:18-4:18), p = 0.038 and 2:05 (2:00-5:19) versus 0:48 (0:44-2:12), p = 0.038. The time of the longest CDE on the ipsilateral side was longer in patients with poor versus good short-term outcome [h:min]: 5:43 (3:05-9:36) versus 1:47 (0:42-2:10), p = 0.018. The logistic regression model for poor short-term outcome included median ABP, the extent of the haemorrhage in the Fisher scale and the time of the longest CDE. We have demonstrated that the time of a CDE is associated with the severity of haemorrhage and short-term outcome in aSAH patients. A NIRS measurement may provide valuable predictive information and could be considered as additional method of neuromonitoring of patients with aSAH.
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http://dx.doi.org/10.1007/s10877-019-00377-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7367903PMC
August 2020

Pattern Recognition in Medical Decision Support.

Biomed Res Int 2019;2019:6048748. Epub 2019 Jun 13.

Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland.

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http://dx.doi.org/10.1155/2019/6048748DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6595383PMC
December 2019

Can interhemispheric desynchronization of cerebral blood flow anticipate upcoming vasospasm in aneurysmal subarachnoid haemorrhage patients?

J Neurosci Methods 2019 09 12;325:108358. Epub 2019 Jul 12.

Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wybrzeże S. Wyspiańskiego 27, 50-370 Wrocław, Poland.

Background: Asymmetry of cerebral autoregulation (CA) was demonstrated in patients after aneurysmal subarachnoid haemorrhage (aSAH). A classical method for CA assessment requires simultaneous measurement of both arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). In this study, we have proposed a cerebral blood flow asymmetry index based only on CBFV and analysed its association with the occurrence of vasospasm after aSAH.

New Method: The phase shifts (PS) between slow oscillations in left and right CBFV (side-to-side PS) and between ABP and CBFV (CBFV-ABP PS) were estimated using multichannel matching pursuit (MMP) and cross-spectral analysis.

Results: We retrospectively analysed data collected from 45 aSAH patients (26 with vasospasm). Data were analysed up to 7th day after aSAH unless the vasospasm was detected earlier. A progressive asymmetry, manifested by a gradual increase in side-to-side PS on consecutive days after aSAH, was observed in patients who developed vasospasm (R = 0.14, p = 0.009). In these patients, early side-to-side PS was more positive than in patients without vasospasm (2.8° ± 5.6° vs -1.7° ± 5.7°, p = 0.011). No such a difference was found in CBFV-ABP PS. Patients with positive side-to-side PS were more likely to develop vasospasm than patients with negative side-to-side PS (21/7 vs 5/12, p = 0.0047).

Comparison With Existing Method: MMP, in contrast to the spectral approach, accounts for non-stationarity of analysed signals. MMP applied to the PS estimation reflects the cerebral blood flow asymmetry in aSAH better than the spectral analysis.

Conclusions: Changes in side-to-side PS might be helpful to identify patients who are at risk of vasospasm.
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http://dx.doi.org/10.1016/j.jneumeth.2019.108358DOI Listing
September 2019

Hypocapnia after traumatic brain injury: how does it affect the time constant of the cerebral circulation?

J Clin Monit Comput 2020 Jun 7;34(3):461-468. Epub 2019 Jun 7.

Division of Academic Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Rd, Cambridge, CB2 0QQ, UK.

The time constant of the cerebral arterial bed ("tau") estimates how fast the blood entering the brain fills the arterial vascular sector. Analogous to an electrical resistor-capacitor circuit, it is expressed as the product of arterial compliance (Ca) and cerebrovascular resistance (CVR). Hypocapnia increases the time constant in healthy volunteers and decreases arterial compliance in head trauma. How the combination of hyocapnia and trauma affects this parameter has yet to be studied. We hypothesized that in TBI patients the intense vasoconstrictive action of hypocapnia would dominate over the decrease in compliance seen after hyperventilation. The predominant vasoconstrictive response would maintain an incoming blood volume in the arterial circulation, thereby lengthening tau. We retrospectively analyzed recordings of intracranial pressure (ICP), arterial blood pressure (ABP), and blood flow velocity (FV) obtained from a cohort of 27 severe TBI patients [(39/30 years (median/IQR), 5 women; admission GCS 6/5 (median/IQR)] studied during a standard clinical CO reactivity test. The reactivity test was performed by means of a 50-min increase in ventilation (20% increase in respiratory minute volume). CVR and Ca were estimated from these recordings, and their product calculated to find the time constant. CVR significantly increased [median CVR pre-hypocapnia/during hypocapnia: 1.05/1.35 mmHg/(cm/s)]. Ca decreased (median Ca pre-hypocapnia/during hypocapnia: 0.130/0.124 arbitrary units) to statistical significance (p = 0.005). The product of these two parameters resulted in a significant prolongation of the time constant (median tau pre-hypocapnia/during hypocapnia: 0.136 s/0.152 s, p ˂ .001). Overall, the increase in CVR dominated over the decrease in compliance, hence tau was longer. We demonstrate a significant increase in the time constant of the cerebral circulation during hypocapnia after severe TBI, and attribute this to an increase in cerebrovascular resistance which outweighs the decrease in cerebral arterial bed compliance.
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http://dx.doi.org/10.1007/s10877-019-00331-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7223592PMC
June 2020

Assessment of Baroreflex Sensitivity Using Time-Frequency Analysis during Postural Change and Hypercapnia.

Comput Math Methods Med 2019 3;2019:4875231. Epub 2019 Feb 3.

Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw 50-370, Poland.

Baroreflex is a mechanism of short-term neural control responsible for maintaining stable levels of arterial blood pressure (ABP) in an ABP-heart rate negative feedback loop. Its function is assessed by baroreflex sensitivity (BRS)-a parameter which quantifies the relationship between changes in ABP and corresponding changes in heart rate (HR). The effect of postural change as well as the effect of changes in blood O and CO have been the focus of multiple previous studies on BRS. However, little is known about the influence of the combination of these two factors on dynamic baroreflex response. Furthermore, classical methods used for BRS assessment are based on the assumption of stationarity that may lead to unreliable results in the case of mostly nonstationary cardiovascular signals. Therefore, we aimed to investigate BRS during repeated transitions between squatting and standing in normal end-tidal CO (EtCO) conditions (normocapnia) and conditions of progressively increasing EtCO with a decreasing level of O (hypercapnia with hypoxia) using joint time and frequency domain (TF) approach to BRS estimation that overcomes the limitation of classical methods. Noninvasive continuous measurements of ABP and EtCO were conducted in a group of 40 healthy young volunteers. The time course of BRS was estimated from TF representations of pulse interval variability and systolic pressure variability, their coherence, and phase spectra. The relationship between time-variant BRS and indices of ABP and HR was analyzed during postural change in normocapnia and hypercapnia with hypoxia. In normocapnia, observed trends in all measures were in accordance with previous studies, supporting the validity of presented TF method. Similar but slightly attenuated response to postural change was observed in hypercapnia with hypoxia. Our results show the merits of the nonstationary methods as a tool to study the cardiovascular system during short-term hemodynamic changes.
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http://dx.doi.org/10.1155/2019/4875231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377966PMC
August 2019

Cerebral arterial time constant calculated from the middle and posterior cerebral arteries in healthy subjects.

J Clin Monit Comput 2019 Aug 5;33(4):605-613. Epub 2018 Oct 5.

Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.

The cerebral arterial blood volume changes (∆CBV) during a single cardiac cycle can be estimated using transcranial Doppler ultrasonography (TCD) by assuming pulsatile blood inflow, constant, and pulsatile flow forward from large cerebral arteries to resistive arterioles [continuous flow forward (CFF) and pulsatile flow forward (PFF)]. In this way, two alternative methods of cerebral arterial compliance (C) estimation are possible. Recently, we proposed a TCD-derived index, named the time constant of the cerebral arterial bed (τ), which is a product of C and cerebrovascular resistance and is independent of the diameter of the insonated vessel. In this study, we aim to examine whether the τ estimated by either the CFF or the PFF model differs when calculated from the middle cerebral artery (MCA) and the posterior cerebral artery (PCA). The arterial blood pressure and TCD cerebral blood flow velocity (CBFV) in the MCA and in the PCA were non-invasively measured in 32 young, healthy volunteers (median age: 24, minimum age: 18, maximum age: 31). The τ was calculated using both the PFF and CFF models from the MCA and the PCA and compared using a non-parametric Wilcoxon signed-rank test. Results are presented as medians (25th-75th percentiles). The cerebrovascular time constant estimated in both arteries using the PFF model was shorter than when using the CFF model (ms): [64.83 (41.22-104.93) vs. 178.60 (160.40-216.70), p < 0.001 in the MCA, and 44.04 (17.15-81.17) vs. 183.50 (153.65-204.10), p < 0.001 in the PCA, respectively]. The τ obtained using the PFF model was significantly longer from the MCA than from the PCA, p = 0.004. No difference was found in the τ when calculated using the CFF model. Longer τ from the MCA might be related to the higher C of the MCA than that of the PCA. Our results demonstrate MCA-PCA differences in the τ, but only when the PFF model was applied.
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http://dx.doi.org/10.1007/s10877-018-0207-3DOI Listing
August 2019

Baroreflex sensitivity and heart rate variability are predictors of mortality in patients with aneurysmal subarachnoid haemorrhage.

J Neurol Sci 2018 11 13;394:112-119. Epub 2018 Sep 13.

Department of Anesthesiology and Intensive Care, Wroclaw Medical University, Wroclaw, Poland.

Object: We aimed to investigate the link between the autonomic nervous system (ANS) impairment, assessed using baroreflex sensitivity (BRS) and heart rate variability (HRV) indices, and mortality after aneurysmal subarachnoid haemorrhage (aSAH).

Methods: A total of 57 patients (56 ± 18 years) diagnosed with aSAH were retrospectively enrolled in the study, where 25% of patients died in the hospital. BRS was calculated using a modified cross-correlation method. Time- and frequency-domain HRV indices were calculated from a time-series of systolic peak intervals of arterial blood pressure signals. Additionally, cerebral autoregulation (CA) was assessed using the mean velocity index (Mxa), where Mxa > 0 indicates impaired CA.

Results: Both BRS and HRV indices were lower in non-survivors than in survivors. The patients with disturbed BRS and HRV had more extensive haemorrhage in the H-H scale (p = .040) and were more likely to die (p = .013) when compared to patients with the intact ANS. The logistic regression model for mortality included: the APACHE II score (p = .002; OR 0.794) and the normalised high frequency power of the HRV (p < <.001; OR 0.636). A positive relationship was found between the Mxa and BRS (R = 0.48, p = .003), which suggests that increasing BRS is moderately strongly associated with worsening CA.

Conclusion: Our results indicated that lower values of HRV indices and BRS correlate with mortality and that there is a link between cerebral dysautoregulation and the analysed estimates of the ANS in aSAH patients.
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http://dx.doi.org/10.1016/j.jns.2018.09.014DOI Listing
November 2018

Assessment of cerebral hemodynamic parameters using pulsatile versus non-pulsatile cerebral blood outflow models.

J Clin Monit Comput 2019 Feb 4;33(1):85-94. Epub 2018 Apr 4.

Brain Physics Laboratory, Department of Clinical Neurosciences, Division of Neurosurgery, University of Cambridge, Cambridge, UK.

Background: Prior methods evaluating the changes in cerebral arterial blood volume (∆CBV) assumed that brain blood transport distal to big cerebral arteries can be approximated with a non-pulsatile flow (CFF) model. In this study, a modified ∆CBV calculation that accounts for pulsatile blood flow forward (PFF) from large cerebral arteries to resistive arterioles was investigated. The aim was to assess cerebral hemodynamic indices estimated by both CFF and PFF models while changing arterial blood carbon dioxide concentration (EtCO) in healthy volunteers.

Materials And Methods: Continuous recordings of non-invasive arterial blood pressure (ABP), transcranial Doppler blood flow velocity (CBFV), and EtCO were performed in 53 young volunteers at baseline and during both hypo- and hypercapnia. The time constant of the cerebral arterial bed (τ) and critical closing pressure (CrCP) were estimated using mathematical transformations of the pulse waveforms of ABP and CBFV, and with both pulsatile and non-pulsatile models of ∆CBV estimation. Results are presented as median values ± interquartile range.

Results: Both CrCP and τ gave significantly lower values with the PFF model when compared with the CFF model (p ≪ 0.001 for both). In comparison to normocapnia, both CrCP and τ determined with the PFF model increased during hypocapnia [CrCP (mm Hg): 5.52 ± 8.78 vs. 14.36 ± 14.47, p = 0.00006; τ (ms): 47.4 ± 53.9 vs. 72.8 ± 45.7, p = 0.002] and decreased during hypercapnia [CrCP (mm Hg): 5.52 ± 8.78 vs. 2.36 ± 7.05, p = 0.0001; τ (ms): 47.4 ± 53.9 vs. 29.0 ± 31.3, p = 0.0003]. When the CFF model was applied, no changes were found for CrCP during hypercapnia or in τ during hypocapnia.

Conclusion: Our results suggest that the pulsatile flow forward model better reflects changes in CrCP and in τ induced by controlled alterations in EtCO.
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http://dx.doi.org/10.1007/s10877-018-0136-1DOI Listing
February 2019

Critical Closing Pressure During a Controlled Increase in Intracranial Pressure.

Acta Neurochir Suppl 2018 ;126:133-137

Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.

Objectives: The objectives were to compare three methods of estimating critical closing pressure (CrCP) in a scenario of a controlled increase in intracranial pressure (ICP) induced during an infusion test in patients with suspected normal pressure hydrocephalus (NPH).

Methods: We retrospectively analyzed data from 37 NPH patients who underwent infusion tests. Computer recordings of directly measured intracranial pressure (ICP), arterial blood pressure (ABP) and transcranial Doppler cerebral blood flow velocity (CBFV) were used. The CrCP was calculated using three methods: first harmonics ratio of the pulse waveforms of ABP and CBFV (CrCP) and two methods based on a model of cerebrovascular impedance, as a function of cerebral perfusion pressure (CrCP), and as a function of ABP (CrCP).

Results: There is good agreement among the three methods of CrCP calculation, with correlation coefficients being greater than 0.8 (p < 0.0001). For the CrCP method, negative values were found for about 20% of all results. Negative values of CrCP were not observed in estimators based on cerebrovascular impedance. During the controlled rise of ICP, all three estimators of CrCP increased significantly (p < 0.05). The strongest correlation between ICP and CrCP was found for CrCP (median R = 0.41).

Conclusion: Invasive CrCP is most sensitive to variations in ICP and can be used as an indicator of the status of the cerebrovascular system during infusion tests.
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http://dx.doi.org/10.1007/978-3-319-65798-1_28DOI Listing
July 2018

Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia.

PLoS One 2017 27;12(7):e0181851. Epub 2017 Jul 27.

Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.

Objective: Classic methods for assessing cerebral autoregulation involve a transfer function analysis performed using the Fourier transform to quantify relationship between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). This approach usually assumes the signals and the system to be stationary. Such an presumption is restrictive and may lead to unreliable results. The aim of this study is to present an alternative method that accounts for intrinsic non-stationarity of cerebral autoregulation and the signals used for its assessment.

Methods: Continuous recording of CBFV, ABP, ECG, and end-tidal CO2 were performed in 50 young volunteers during normocapnia and hypercapnia. Hypercapnia served as a surrogate of the cerebral autoregulation impairment. Fluctuations in ABP, CBFV, and phase shift between them were tested for stationarity using sphericity based test. The Zhao-Atlas-Marks distribution was utilized to estimate the time-frequency coherence (TFCoh) and phase shift (TFPS) between ABP and CBFV in three frequency ranges: 0.02-0.07 Hz (VLF), 0.07-0.20 Hz (LF), and 0.20-0.35 Hz (HF). TFPS was estimated in regions locally validated by statistically justified value of TFCoh. The comparison of TFPS with spectral phase shift determined using transfer function approach was performed.

Results: The hypothesis of stationarity for ABP and CBFV fluctuations and the phase shift was rejected. Reduced TFPS was associated with hypercapnia in the VLF and the LF but not in the HF. Spectral phase shift was also decreased during hypercapnia in the VLF and the LF but increased in the HF. Time-frequency method led to lower dispersion of phase estimates than the spectral method, mainly during normocapnia in the VLF and the LF.

Conclusion: The time-frequency method performed no worse than the classic one and yet may offer benefits from lower dispersion of phase shift as well as a more in-depth insight into the dynamic nature of cerebral autoregulation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0181851PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5531479PMC
October 2017

Changes in the level of cardiac troponine and disorders in pulmonary gas exchange as predictors of short- and long-term outcomes of patients with aneurysm subarachnoid haemorrhage.

Br J Neurosurg 2017 Dec 21;31(6):653-660. Epub 2017 Jun 21.

a Department of Anaesthesiology and Intensive Care , Wroclaw Medical University , Wroclaw , Poland.

Subject: Cardiopulmonary abnormalities are common after aneurysmal subarachnoid haemorrhage (aSAH). However, the relationship between short- and long-term outcome is poorly understood. In this paper, we present how cardiac troponine elevations (cTnI) and pulmonary disorders are associated with short- and long-term outcomes assessed by the Glasgow Outcome Scale (GOS) and Extended Glasgow Outcome Scale (GOSE).

Methods: A total of 104 patients diagnosed with aSAH were analysed in the study. The non-parametric U Mann-Whitney test was used to evaluate the difference between good (GOS IV-V, GOSE V-VIII) and poor (GOS I-III, GOSE I-IV) outcomes in relation to cTnI elevation and pulmonary disorders. Outcome was assessed at discharge from the hospital, and then followed up 6 and 12 months later. Pulmonary disorders were determined by the PaO/FiO ratio and radiography. The areas under the ROC curves (AUCs) were used to determine the predictive power of these factors.

Results: In the group with good short-term outcomes cTnI elevation on the second day after aSAH was significantly lower (p = .00007) than in patients with poor short-term outcomes. The same trend was observed after 6 months, although there were different results 12 months from the onset (p = .024 and n.s., respectively). A higher peak of cTnI was observed in the group with a pathological X-ray (p = .008) and pathological PaO/FiO ratio (p ≪ .001). cTnI was an accurate predictor of short-term outcomes (AUC = 0.741, p ≪ .001) and the outcome after 6 months (AUC = 0.688, p = .015).

Conclusion: The results showed that cardiopulmonary abnormalities perform well as predictive factors for short- and long-term outcomes after aSAH.
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http://dx.doi.org/10.1080/02688697.2017.1339301DOI Listing
December 2017

Critical Closing Pressure During Controlled Increase in Intracranial Pressure-Comparison of Three Methods.

IEEE Trans Biomed Eng 2018 03 24;65(3):619-624. Epub 2017 May 24.

Goal: Critical closing pressure (CrCP) is the arterial blood pressure (ABP) threshold, below which small arterial vessels collapse and cerebral blood flow ceases. Here, we aim to compare three methods for CrCP estimation in scenario of a controlled increase in intracranial pressure (ICP), induced by infusion tests performed in patients with suspected normal pressure hydrocephalus (NPH).

Methods: Computer recordings of directly-measured ICP, ABP, and transcranial Doppler cerebral blood flow velocity (CBFV), from 37 NPH patients undergoing infusion tests, were retrospectively analyzed. The CrCP was calculated with three methods: one with the first harmonics ratio of the pulse waveforms of ABP and CBFV (CrCPA) and two methods based on a model of cerebrovascular impedance, as functions of both cerebral perfusion pressure (CrCPinv), and of ABP (CrCPninv).

Conclusion: All methods give similar results in response to ICP changes. In the case of individual CrCP measurements for each patient, CrCPA may provide negative, nonphysiological values. Invasive critical closing pressure is most sensitive to variations in ICP and CPP and can be used as an indicator of the cerebrospinal and the cerebrovascular system status during infusion tests.
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http://dx.doi.org/10.1109/TBME.2017.2707547DOI Listing
March 2018

Phase shift between respiratory oscillations in cerebral blood flow velocity and arterial blood pressure.

Physiol Meas 2017 02 18;38(2):310-324. Epub 2017 Jan 18.

Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.

We aim to investigate whether phase shift between respiratory oscillations in cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) is associated with changes in cerebral autoregulation (CA) or reflects the mechano-elastic properties of the cerebrovascular bed. The relationships between respiratory phase shift and slow wave phase shift versus cerebrovascular time constant (the product of cerebrovascular resistance and compliance) and the index of CA (Mx) were analyzed during breathing at 6, 10, and 15 breaths min in 39 volunteers. With increasing respiratory rate the time constant, Mx, and respiratory phase shift decreased, whereas slow wave phase shift increased. The time constant correlated moderately strongly with the respiratory phase shift (R  =  0.49, p [Formula: see text] 0.001) and did not correlate with the slow wave phase shift. The slow wave phase shift was significantly associated with Mx (R  =  -0.46, p [Formula: see text] 0.001). The respiratory phase shift more accurately reflects the mechano-elastic properties of the cerebrovascular bed, whereas CA is better described by the slow wave phase shift.
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http://dx.doi.org/10.1088/1361-6579/38/2/310DOI Listing
February 2017

Complexity of brain signals is associated with outcome in preterm infants.

J Cereb Blood Flow Metab 2017 Oct 11;37(10):3368-3379. Epub 2017 Jan 11.

3 Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.

A characteristic feature of complex healthy biological systems is the ability to react and adapt to minute changes in the environment. This 'complexity' manifests itself in highly irregular patterns of various physiological measurements. Here, we apply Multiscale Entropy (MSE) analysis to assess the complexity of systemic and cerebral near-infrared spectroscopy (NIRS) signals in a cohort of 61 critically ill preterm infants born at median (range) gestational age of 26 (23-31) weeks, before 24 h of life. We further correlate the complexity of these parameters with brain injury and mortality. Lower complexity index (CoI) of oxygenated haemoglobin (HbO), deoxygenated haemoglobin (Hb) and tissue oxygenation index (TOI) were observed in those infants who developed intraventricular haemorrhage (IVH) compared to those who did not (P = 0.002, P = 0.010 and P = 0.038, respectively). Mean CoI of HbO, Hb and total haemoglobin index (THI) were lower in those infants who died compared to those who survived (P = 0.012, P = 0.004 and P = 0.003, respectively). CoI-HbO was an independent predictor of IVH (P = 0.010). Decreased complexity of brain signals was associated with mortality and brain injury. Measurement of brain signal complexity in preterm infants is feasible and could represent a significant advance in the brain-oriented care.
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http://dx.doi.org/10.1177/0271678X16687314DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624386PMC
October 2017

Outcome, Pressure Reactivity and Optimal Cerebral Perfusion Pressure Calculation in Traumatic Brain Injury: A Comparison of Two Variants.

Acta Neurochir Suppl 2016 ;122:221-3

Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.

This study investigates the outcome prediction and calculation of optimal cerebral perfusion pressure (CPPopt) in 307 patients after severe traumatic brain injury (TBI) based on cerebrovascular reactivity calculation of a moving correlation correlation coefficient, named PRx, between mean arterial pressure (ABP) and intracranial pressure (ICP). The correlation coefficient was calculated from simultaneously recorded data using different frequencies. PRx was calculated from oscillations between 0.008 and 0.05Hz and the longPRx (L-PRx) was calculated from oscillations between 0.0008 and 0.016 Hz. PRx was a significant mortality predictor, whereas L-PRx was not. CPPopt for pooled data was higher for L-PRx than for PRx, with no statistical difference. Mortality was associated with mean CPP below CPPopt. Severe disability was associated with CPP above CPPopt (PRx). These relationships were not statistically significant for CPPopt (L-PRx). We conclude that PRx and L-PRx cannot be used interchangeably.
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http://dx.doi.org/10.1007/978-3-319-22533-3_44DOI Listing
July 2017

Cerebral Arterial Time Constant Recorded from the MCA and PICA in Normal Subjects.

Acta Neurochir Suppl 2016 ;122:211-4

Department of Neurology, University of Freiburg, Freiburg, Germany.

Cerebral arterial time constant (τ) estimates how quickly the cerebral arterial bed distal to the point of insonation is filled with arterial blood following a cardiac contraction. It is not known how τ behaves in different vascular territories in the brain. We therefore investigated the differences in τ of two cerebral arteries: the posterior inferior cerebellar artery (PICA) and the middle cerebral artery (MCA).Transcranial Doppler cerebral blood flow velocity (CBFV) in the PICA and left MCA along with Finapres arterial blood pressure (ABP) were simultaneously recorded in 35 young healthy volunteers. τ was estimated using mathematical transformations of pulse waveforms of ABP and the CBFV of the MCA and the PICA. Since τ is independent from the vessel radius, its comparison in different cerebral arteries was feasible. Mean ABP was 76.1 ± 9.6 mmHg. The CBFV of the MCA was higher than that of the PICA (59.7 ± 7.7 vs. 41.0 ± 4.5 cm/s; p < 0.000001). τ of the PICA was shorter than that of the MCA (0.15 ± 0.03 vs. 0.18 ± 0.03 s; p < 0.000001). The MCA-supplied vascular bed has a longer distal average length, measured from the place of insonation up to the small arterioles, than the PICA-supplied vascular bed. Therefore, a longer time is needed to fill it with arterial blood volume. This study thus confirms the physiological validity of the τ concept.
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http://dx.doi.org/10.1007/978-3-319-22533-3_42DOI Listing
July 2017

Monitoring Cerebral Autoregulation After Subarachnoid Hemorrhage.

Acta Neurochir Suppl 2016 ;122:199-203

Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Box 167, Block A, Hills Road, CB2 0QQ, Cambridge, UK.

Introduction: Delayed cerebral ischemia (DCI) is a major contributor to morbidity and mortality after subarachnoid hemorrhage (SAH). Data challenge vasospasm being the sole cause of ischemia and suggest other factors. We tested the hypothesis that early autoregulatory failure might predict DCI.

Methods: This is a prospective observational study of cerebral autoregulation following SAH in which the primary end point was DCI at 21 days. Cox proportional hazards and multivariate models were used and the benefit of using multiple indices was analyzed.

Results: Ninety-eight patients were included in the study. There was an increased risk of DCI with early dysautoregulation (odds ratio [OR]: 7.46, 95% confidence interval [CI]: 3.03-18.40 and OR: 4.52, 95 % CI: 1.84-11.07 for the transcranial Doppler index of autoregulation [Sxa] and near-infrared spectroscopy index of autoregulation [TOxa], respectively), but not vasospasm (OR: 1.36, 95 % CI: 0.56-3.33). Sxa and TOxa remained independent predictors of DCI in the multivariate model (OR: 12.66, 95 % CI: 2.97-54.07 and OR: 5.34, 95 % CI: 1.25-22.84 for Sxa and TOxa, respectively). There was good agreement between different indices. All 13 patients with impaired autoregulation in all three methods developed DCI.

Conclusions: Disturbed autoregulation in the first 5 days after SAH is predictive of DCI. Although colinearities exist between the methods assessed, multimodal monitoring of cerebral autoregulation can aid the prediction of DCI.
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http://dx.doi.org/10.1007/978-3-319-22533-3_40DOI Listing
July 2017

Plateau Waves of Intracranial Pressure and Partial Pressure of Cerebral Oxygen.

Acta Neurochir Suppl 2016 ;122:177-9

Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.

This study investigates 55 intracranial pressure (ICP) plateau waves recorded in 20 patients after severe traumatic brain injury (TBI) with a focus on a moving correlation coefficient between mean arterial pressure (ABP) and ICP, called PRx, which serves as a marker of cerebrovascular reactivity, and a moving correlation coefficient between ABP and cerebral partial pressure of oxygen (pbtO2), called ORx, which serves as a marker for cerebral oxygen reactivity. ICP and ICPamplitude increased significantly during the plateau waves, whereas CPP and pbtO2 decreased significantly. ABP, ABP amplitude, and heart rate remained unchanged. In 73 % of plateau waves PRx increased during the wave. ORx showed an increase during and a decrease after the plateau waves, which was not statistically significant. Our data show profound cerebral vasoparalysis on top of the wave and, to a lesser extent, impairment of cerebral oxygen reactivity. The different behavior of the indices may be due to the different latencies of the cerebral blood flow and oxygen level control mechanisms. While cerebrovascular reactivity is a rapidly reacting mechanism, cerebral oxygen reactivity is slower.
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http://dx.doi.org/10.1007/978-3-319-22533-3_36DOI Listing
July 2017

Increasing Intracranial Pressure After Head Injury: Impact on Respiratory Oscillations in Cerebral Blood Flow Velocity.

Acta Neurochir Suppl 2016 ;122:171-5

Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.

Experiments have shown that closed-box conditions alter the transmission of respiratory oscillations (R waves) to organ blood flow already at a marginal pressure increase. How does the increasing intracranial pressure (ICP) interact with R waves in cerebral blood flow after head injury (HI)?Twenty-two head-injured patients requiring sedation and mechanical ventilation were monitored for ICP, Doppler flow velocity (FV) in the middle cerebral arteries, and arterial blood pressure (ABP). The analysis included transfer function gains of R waves (9-20 cpm) from ABP to FV, and indices of pressure-volume reserve (RAP) and autoregulation (Mx). Increasing ICP has dampened R-wave gains from day 1 to day 4 after HI in all patients. A large impact (ΔGain /ΔICP right: 0.14 ± 0.06; left: 0.18 ± 0.08) was associated with exhausted reserves (RAP ≥0.85). When RAP was <0.85, rising ICP had a lower impact on R-wave gains (ΔGain /ΔICP right: 0.05 ± 0.02; left: 0.06 ± 0.04; p < 0.05), but increased the pulsatility indices (right: 1.35 ± 0.55; left: 1.25 ± 0.52) and Mx indices (right: 0.30 ± 0.12; left: 0.28 ± 0.08, p < 0.05). Monitoring of R waves in blood pressure and cerebral blood flow velocity has suggested that rising ICP after HI might have an impact on cerebral blood flow directly, even before autoregulation is impaired.
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http://dx.doi.org/10.1007/978-3-319-22533-3_35DOI Listing
July 2017

The Interaction Between Heart Systole and Cerebral Circulation During Lower Body Negative Pressure Test.

Acta Neurochir Suppl 2016 ;122:137-41

Department of Neurology, University Hospital Aachen, Aachen, Germany.

The time constant (τ[s]) estimates how fast the arterial part of the cerebrovascular bed fills with blood volume during the cardiac cycle, whereas a product of τ and heart rate (HR) (τ*HR[%]) assesses how this period of arterial filling is related to an entire heart cycle. In this study we aimed to investigate cerebral hemodynamics using τ and τ*HR during a progressive lower body negative pressure (LBNP) test.Transcranial Doppler cerebral blood flow velocity (CBFV), Finapres arterial blood pressure (ABP), and HR, along with end-tidal CO2, were simultaneously recorded in 38 healthy volunteers during an LBNP test. The τ was estimated using mathematical transformation of ABP and CBFV pulse waveforms. After a gradual shortening of τ from baseline (0.20 ± 0.06 s) to maximal LBNP before the onset of presyncope (0.15 ± 0.05 s), we observed a significant increase in τ at presyncope (0.24 ± 0.15 s; p = 0.0001). In the course of LBNP, the τ*HR did not significantly change from baseline (25.6 ± 5.7 % vs 26.6 ± 8.9 %, p = n.s.) except for presyncope, when it increased to 40.4 ± 21.1 % (p < 0.000001). Because the time needed to fill the arterial part of the cerebrovascular bed with blood is prolonged during presyncope, an increased part of the heart cycle seems to be spent on the cerebral blood supply.
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http://dx.doi.org/10.1007/978-3-319-22533-3_28DOI Listing
July 2017

A comparison of the Full Outline of UnResponsiveness (FOUR) score and Glasgow Coma Score (GCS) in predictive modelling in traumatic brain injury.

Br J Neurosurg 2016 22;30(2):211-20. Epub 2016 Mar 22.

b Department of Anaesthesiology and Intensive Care Unit , Wroclaw Medical University , Wroclaw , Poland.

Objectives: To compare the performance of multivariate predictive models incorporating either the Full Outline of UnResponsiveness (FOUR) score or Glasgow Coma Score (GCS) in order to test whether substituting GCS with the FOUR score in predictive models for outcome in patients after TBI is beneficial.

Material And Methods: A total of 162 TBI patients were prospectively enrolled in the study. Stepwise logistic regression analysis was conducted to compare the prediction of (1) in-ICU mortality and (2) unfavourable outcome at 3 months post-injury using as predictors either the FOUR score or GCS along with other factors that may affect patient outcome. The areas under the ROC curves (AUCs) were used to compare the discriminant ability and predictive power of the models. The internal validation was performed with bootstrap technique and expressed as accuracy rate (AcR).

Results: The FOUR score, age, the CT Rotterdam score, systolic ABP and being placed on ventilator within day one (model 1: AUC: 0.906 ± 0.024; AcR: 80.3 ± 4.8%) performed equally well in predicting in-ICU mortality as the combination of GCS with the same set of predictors plus pupil reactivity (model 2: AUC: 0.913 ± 0.022; AcR: 81.1 ± 4.8%). The CT Rotterdam score, age and either the FOUR score (model 3) or GCS (model 4) equally well predicted unfavourable outcome at 3 months post-injury (AUC: 0.852 ± 0.037 vs. 0.866 ± 0.034; AcR: 72.3 ± 6.6% vs. 71.9%±6.6%, respectively). Adding the FOUR score or GCS at discharge from ICU to predictive models for unfavourable outcome increased significantly their performances (AUC: 0.895 ± 0.029, p = 0.05; AcR: 76.1 ± 6.5%; p < 0.004 when compared with model 3; and AUC: 0.918 ± 0.025, p < 0.05; AcR: 79.6 ± 7.2%, p < 0.009 when compared with model 4), but there was no benefit from substituting GCS with the FOUR score.

Conclusion: Results showed that FOUR score and GCS perform equally well in multivariate predictive modelling in TBI.
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http://dx.doi.org/10.3109/02688697.2016.1161173DOI Listing
January 2017

Complexity of cerebral blood flow velocity and arterial blood pressure in subarachnoid hemorrhage using time-frequency analysis.

Annu Int Conf IEEE Eng Med Biol Soc 2015 ;2015:7700-3

We investigated changes of time-frequency (TF) complexity, in terms of Rényi entropy and a measure of concentration, of middle cerebral blood flow velocity (CBFV) and arterial blood pressure in relation to the development of cerebral vasospasm in 15 patients after aneurysmal subarachnoid hemorrhage. Interhemispheric differences in the period of no vasospasm and vasospasm were also compared. Results show reduced complexity of TF representations of CBFV on the side of aneurysm before vasospasm was identified. This potentially can serve as an early-warning indicator of future derangement of cerebral circulation.
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http://dx.doi.org/10.1109/EMBC.2015.7320176DOI Listing
September 2016