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Dynamic cerebral autoregulation during step-wise increases in blood pressure during anaesthesia: A nonrandomised interventional trial. Eur J Anaesthesiol 2023; 40:407-417. [PMID: 36655712 PMCID: PMC10155696 DOI: 10.1097/eja.0000000000001798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND Classically, cerebral autoregulation (CA) entails cerebral blood flow (CBF) remaining constant by cerebrovascular tone adapting to fluctuations in mean arterial pressure (MAP) between ∼60 and ∼150 mmHg. However, this is not an on-off mechanism; previous work has suggested that vasomotor tone is proportionally related to CA function. During propofol-based anaesthesia, there is cerebrovascular vasoconstriction, and static CA remains intact. Sevoflurane-based anaesthesia induces cerebral vasodilation and attenuates CA dose-dependently. It is unclear how this translates to dynamic CA across a range of blood pressures in the autoregulatory range. OBJECTIVE The aim of this study was to quantify the effect of step-wise increases in MAP between 60 and 100 mmHg, using phenylephrine, on dynamic CA during propofol- and sevoflurane-based anaesthesia. DESIGN A nonrandomised interventional trial. SETTING Single centre enrolment started on 11 January 2019 and ended on 23 September 2019. PATIENTS We studied American Society of Anesthesiologists (ASA) I/II patients undergoing noncardiothoracic, nonneurosurgical and nonlaparoscopic surgery under general anaesthesia. INTERVENTION In this study, cerebrovascular tone was manipulated in the autoregulatory range by increasing MAP step-wise using phenylephrine in patients receiving either propofol- or sevoflurane-based anaesthesia. MAP and mean middle cerebral artery blood velocity (MCA Vmean ) were measured in ASA I and II patients, anaesthetised with either propofol ( n = 26) or sevoflurane ( n = 28), during 10 mmHg step-wise increments of MAP between 60 and 100 mmHg. Static CA was determined by plotting 2-min averaged MCA Vmean versus MAP. Dynamic CA was determined using transfer function analysis and expressed as the phase lead (°) between MAP and MCA Vmean oscillations, created with positive pressure ventilation with a frequency of 6 min -1 . MAIN OUTCOMES The primary outcome of this study was the response of dynamic CA during step-wise increases in MAP during propofol- and sevoflurane-based anaesthesia. RESULTS MAP levels achieved per step-wise increments were comparable between anaesthesia regiment (63 ± 3, 72 ± 2, 80 ± 2, 90 ± 2, 100 ± 3 mmHg, and 61 ± 4, 71 ± 2, 80 ± 2, 89 ± 2, 98 ± 4 mmHg for propofol and sevoflurane, respectively). MCA Vmean increased more during step-wise MAP increments for sevoflurane compared to propofol ( P ≤0.001). Dynamic CA improved during propofol (0.73° mmHg -1 , 95% CI 0.51 to 0.95; P ≤ 0.001)) and less pronounced during sevoflurane-based anaesthesia (0.21° mmHg -1 (95% CI 0.01 to 0.42, P = 0.04). CONCLUSIONS During general anaesthesia, dynamic CA is dependent on MAP, also within the autoregulatory range. This phenomenon was more pronounced during propofol anaesthesia than during sevoflurane. TRIAL REGISTRATION NCT03816072 ( https://clinicaltrials.gov/ct2/show/NCT03816072 ).
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The Influence of Carbon Dioxide on Cerebral Autoregulation During Sevoflurane-based Anesthesia in Patients With Type 2 Diabetes. J Neurosurg Anesthesiol 2023; 35:65-73. [PMID: 34387283 DOI: 10.1097/ana.0000000000000794] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/06/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Cerebral autoregulation (CA) continuously adjusts cerebrovascular resistance to maintain cerebral blood flow (CBF) constant despite changes in blood pressure. Also, CBF is proportional to changes in arterial carbon dioxide (CO 2 ) (cerebrovascular CO 2 reactivity). Hypercapnia elicits cerebral vasodilation that attenuates CA efficacy, while hypocapnia produces cerebral vasoconstriction that enhances CA efficacy. In this study, we quantified the influence of sevoflurane anesthesia on CO 2 reactivity and the CA-CO 2 relationship. METHODS We studied patients with type 2 diabetes mellitus (DM), prone to cerebrovascular disease, and compared them to control subjects. In 33 patients (19 DM, 14 control), end-tidal CO 2 , blood pressure, and CBF velocity were monitored awake and during sevoflurane-based anesthesia. CA, calculated with transfer function analysis assessing phase lead (degrees) between low-frequency oscillations in CBF velocity and mean arterial blood pressure, was quantified during hypocapnia, normocapnia, and hypercapnia. RESULTS In both control and DM patients, awake CO 2 reactivity was smaller (2.8%/mm Hg CO 2 ) than during sevoflurane anesthesia (3.9%/mm Hg; P <0.005). Hyperventilation increased CA efficacy more (3 deg./mm Hg CO 2 ) in controls than in DM patients (1.8 deg./mm Hg CO 2 ; P <0.001) in both awake and sevoflurane-anesthetized states. CONCLUSIONS The CA-CO 2 relationship is impaired in awake patients with type 2 DM. Sevoflurane-based anesthesia does not further impair this relationship. In patients with DM, hypocapnia induces cerebral vasoconstriction, but CA efficacy does not improve as observed in healthy subjects.
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Kho E, Sperna Weiland NH, Vlaar APJ, Veelo DP, van der Ster BJP, Corsmit OT, Koolbergen DR, Dilai J, Immink RV. Cerebral hemodynamics during sustained intra-operative hypotension. J Appl Physiol (1985) 2022; 132:1560-1568. [PMID: 35511723 DOI: 10.1152/japplphysiol.00050.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Background Static cerebral autoregulation (CA) maintains cerebral blood flow (CBF) relatively constant above a mean arterial blood pressure (BPmean) of 60-65 mmHg. Below this lower limit of CA (LLCA), CBF declines along with BPmean. Data are lacking describing how CA reacts to sustained hypotension, since hypotension is usually avoided. In this study, we took advantage of a procedure requiring sustained hypotension. We assessed static CA for LLCA determination, and a more continuous CA, which counter short-term blood pressure variations. With these data, we analyzed CA during longstanding hypotension. Methods Continuous arterial blood pressure and middle cerebral artery blood flow velocity (MCAVmean) were monitored in 23 patients that required deep intra-operative hypotension. The LLCA was determined for every patient, and BPmean below this LLCA was classified as the patient specific hypotension. With the mean flow index (Mxa) continuous CA (Mxa-CA) was quantified. Mxa was calculated and averaged after induction of general anesthesia (baseline), every 15 minutes during, and 15 minutes after one-hour of hypotension. Functioning CA was defined as Mxa <0.4. Data are expressed as median (25th-75th percentile). Results The LLCA was located at 56 (47-74) mmHg. At baseline, Mxa was 0.21 (0.14-0.32) and 0.61 (0.48-0.78) during hypotension (p<0.01), with no appreciable change over time, n=12. After blood pressure restoration, Mxa improved, 0.25 (0.06-0.35, n=9). Conclusions Mxa-CA became and remained disturbed during the one-hour of hypotension, and improved after blood pressure restoration. This completely reversible situation suggests no ischemic hyperemia occurs and renders an adaptation mechanism during sustained hypotension unlikely.
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Affiliation(s)
- Eline Kho
- Department of Intensive Care, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.,Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Alexander P J Vlaar
- Department of Intensive Care, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Denise P Veelo
- Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Björn J P van der Ster
- Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Oskar T Corsmit
- Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Dave R Koolbergen
- Department of Cardio-thoracic Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - José Dilai
- Department of Clinical Neurophysiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Rogier V Immink
- Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
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Longhitano Y, Iannuzzi F, Bonatti G, Zanza C, Messina A, Godoy D, Dabrowski W, Xiuyun L, Czosnyka M, Pelosi P, Badenes R, Robba C. Cerebral Autoregulation in Non-Brain Injured Patients: A Systematic Review. Front Neurol 2021; 12:732176. [PMID: 34899560 PMCID: PMC8660115 DOI: 10.3389/fneur.2021.732176] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 10/11/2021] [Indexed: 01/12/2023] Open
Abstract
Introduction: Cerebral autoregulation (CA) plays a fundamental role in the maintenance of adequate cerebral blood flow (CBF). CA monitoring, through direct and indirect techniques, may guide an appropriate therapeutic approach aimed at improving CBF and reducing neurological complications; so far, the role of CA has been investigated mainly in brain-injured patients. The aim of this study is to investigate the role of CA in non-brain injured patients. Methods: A systematic consultation of literature was carried out. Search terms included: “CA and sepsis,” “CA and surgery,” and “CA and non-brain injury.” Results: Our research individualized 294 studies and after screening, 22 studies were analyzed in this study. Studies were divided in three groups: CA in sepsis and septic shock, CA during surgery, and CA in the pediatric population. Studies in sepsis and intraoperative setting highlighted a relationship between the incidence of sepsis-associated delirium and impaired CA. The most investigated setting in the pediatric population is cardiac surgery, but the role and measurement of CA need to be further elucidated. Conclusion: In non-brain injured patients, impaired CA may result in cognitive dysfunction, neurological damage, worst outcome, and increased mortality. Monitoring CA might be a useful tool for the bedside optimization and individualization of the clinical management in this group of patients.
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Affiliation(s)
- Yaroslava Longhitano
- Department of Anesthesiology and Critical Care, AO St. Antonio, Biagio and Cesare Arrigo, Alessandria, Italy
| | - Francesca Iannuzzi
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa, Genoa, Italy
| | - Giulia Bonatti
- Anesthesia and Intensive Care, Gaslini Hospital, Genova, Italy
| | - Christian Zanza
- Foundation of "Nuovo Ospedale Alba-Bra" and Department of Emergency Medicine, Anesthesia and Critical Care Division, Michele and Pietro Ferrero Hospital, Verduno, Italy
| | - Antonio Messina
- Humanitas Clinical and Research Center - IRCCS, Milan, Italy.,Department of Biomedical Sciences, Humanitas University, Milan, Italy
| | - Daniel Godoy
- Neurointensive Care Unit, Sanatorio Pasteur, 2 Intensive Care Unit, Hospital Carlos Malbran, Catamarca, Argentina
| | | | - Li Xiuyun
- Department of Anesthesiology & Critical Care Medicine, John Hopkins University, Baltimore, MD, United States
| | - Marek Czosnyka
- Brain Physics Laboratory, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Paolo Pelosi
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa, Genoa, Italy.,Anesthesia and Critical Care, San Martino Policlinico Hospital, IRCCS for Oncology and Neuroscience, Genoa, Italy
| | - Rafael Badenes
- Department of Anesthesiology and Surgical-Trauma Intensive Care, Hospital Clinic Universitari de Valencia, Department of Surgery, University of Valencia, Valencia, Spain
| | - Chiara Robba
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa, Genoa, Italy.,Anesthesia and Critical Care, San Martino Policlinico Hospital, IRCCS for Oncology and Neuroscience, Genoa, Italy
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Effects of dobutamine and phenylephrine on cerebral perfusion in patients undergoing cerebral bypass surgery: a randomised crossover trial. Br J Anaesth 2020; 125:539-547. [PMID: 32718724 PMCID: PMC7565906 DOI: 10.1016/j.bja.2020.05.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/20/2020] [Accepted: 05/13/2020] [Indexed: 01/22/2023] Open
Abstract
Background Patients undergoing cerebral bypass surgery are prone to cerebral hypoperfusion. Currently, arterial blood pressure is often increased with vasopressors to prevent cerebral ischaemia. However, this might cause vasoconstriction of the graft and cerebral vasculature and decrease perfusion. We hypothesised that cardiac output, rather than arterial blood pressure, is essential for adequate perfusion and aimed to determine whether dobutamine administration resulted in greater graft perfusion than phenylephrine administration. Methods This randomised crossover study included 10 adult patients undergoing cerebral bypass surgery. Intraoperatively, patients randomly and sequentially received dobutamine to increase cardiac index or phenylephrine to increase mean arterial pressure (MAP). An increase of >10% in cardiac index or >10% in MAP was targeted, respectively. Before both interventions, a reference phase was implemented. The primary outcome was the absolute difference in graft flow between the reference and intervention phase. We compared the absolute flow difference between each intervention and constructed a random-effect linear regression model to explore treatment and carry-over effects. Results Graft flow increased with a median of 4.1 (inter-quartile range [IQR], 1.7–12.0] ml min−1) after dobutamine administration and 3.6 [IQR, 1.3–7.8] ml min−1 after phenylephrine administration (difference –0.6 ml min−1; 95% confidence interval [CI], –14.5 to 5.3; P=0.441). There was no treatment effect (0.9 ml min−1; 95% CI, 0.0–20.1; P=0.944) and no carry-over effect. Conclusions Both dobutamine and phenylephrine increased graft flow during cerebral bypass surgery, without a preference for one method over the other. Clinical trial registration Netherlands Trial Register, NL7077 (https://www.trialregister.nl/trial/7077).
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Uryga A, Kasprowicz M, Burzyńska M, Calviello L, Kaczmarska K, Czosnyka M. Cerebral arterial time constant calculated from the middle and posterior cerebral arteries in healthy subjects. J Clin Monit Comput 2018; 33:605-613. [PMID: 30291539 DOI: 10.1007/s10877-018-0207-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 10/01/2018] [Indexed: 10/28/2022]
Abstract
The cerebral arterial blood volume changes (∆CaBV) 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 (Ca) 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 Ca 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 (CBFVa) 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 Ca 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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Affiliation(s)
- Agnieszka Uryga
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wrocław, Poland.
| | - Magdalena Kasprowicz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wrocław, Poland
| | - Małgorzata Burzyńska
- Department of Anesthesiology and Intensive Care, Wroclaw Medical University, Wrocław, Poland
| | - Leanne Calviello
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Katarzyna Kaczmarska
- Department of Neurosurgery, Mossakowski Medical Research Centre Polish Academy of Sciences, Warsaw, Poland.,Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.,Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
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Sperna Weiland NH, Hermanides J, van der Ster BJP, Hollmann MW, Preckel B, Stok WJ, van Lieshout JJ, Immink RV. Sevoflurane based anaesthesia does not affect already impaired cerebral autoregulation in patients with type 2 diabetes mellitus. Br J Anaesth 2018; 121:1298-1307. [PMID: 30442257 DOI: 10.1016/j.bja.2018.07.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 06/11/2018] [Accepted: 07/09/2018] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND The baroreflex regulates arterial blood pressure (BP). During periods when blood pressure changes, cerebral blood flow (CBF) is kept constant by cerebral autoregulation (CA). In patients with diabetes mellitus (DM), low baroreflex sensitivity (BRS) is associated with impaired CA. As sevoflurane-based anaesthesia obliterates BRS, we hypothesised that this could aggravate the already impaired CA in patients with DM resulting in a 'double-hit' on cerebral perfusion leading to increased fluctuations in blood pressure and cerebral perfusion. METHODS On the day before surgery, we measured CBF velocity (CBFV), heart rate, and BP to determine BRS and CA efficacy (CBFVmean-to-BPmean-phase lead) in 25 patients with DM and in 14 controls. During the operation, BRS and CA efficacy were determined during sevoflurane-based anaesthesia. Patients with DM were divided into a group with high BRS (DMBRS↑) and a group with low BRS (DMBRS↓). Values presented are median (inter-quartile range). RESULTS Preoperative vs intraoperative BRS was 6.2 (4.5-8.5) vs 1.9 (1.1-2.5, P<0.001) ms mm Hg-1 for controls, 5.8 (4.9-7.6) vs 2.7 (1.5-3.9, P<0.001) ms mm Hg-1 for patients with DMBRS↑, and 1.9 (1.5-2.8) vs 1.1 (0.6-2.5, P=0.31) ms mm Hg-1 for patients with DMBRS↓. Preoperative vs intraoperative CA efficacy was 43° (38-46) vs 43° (38-51, P=0.30), 44° (36-49) vs 41° (32-49, P=0.52), and 34° (28-40) vs 30° (27-38, P=0.64) for controls, DMBRS↑, and DMBRS↓ patients, respectively. CONCLUSIONS In diabetic patients with low preoperative BRS, preoperative CA efficacy was also impaired. In controls and diabetic patients, CA was unaffected by sevoflurane-based anaesthesia. We therefore conclude that sevoflurane-based anaesthesia does not contribute to a 'double-hit' phenomenon on cerebral perfusion. CLINICAL TRIAL REGISTRATION NCT 03071432.
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Affiliation(s)
- N H Sperna Weiland
- Amsterdam UMC, University of Amsterdam, Anaesthesiology, Amsterdam, The Netherlands; Amsterdam UMC, University of Amsterdam, Laboratory for Clinical Cardiovascular Physiology, Department of Medical Biology, Amsterdam, The Netherlands
| | - J Hermanides
- Amsterdam UMC, University of Amsterdam, Anaesthesiology, Amsterdam, The Netherlands.
| | - B J P van der Ster
- Amsterdam UMC, University of Amsterdam, Laboratory for Clinical Cardiovascular Physiology, Department of Medical Biology, Amsterdam, The Netherlands; Amsterdam UMC, University of Amsterdam, Internal Medicine, Amsterdam, The Netherlands
| | - M W Hollmann
- Amsterdam UMC, University of Amsterdam, Anaesthesiology, Amsterdam, The Netherlands
| | - B Preckel
- Amsterdam UMC, University of Amsterdam, Anaesthesiology, Amsterdam, The Netherlands
| | - W J Stok
- Amsterdam UMC, University of Amsterdam, Laboratory for Clinical Cardiovascular Physiology, Department of Medical Biology, Amsterdam, The Netherlands
| | - J J van Lieshout
- Amsterdam UMC, University of Amsterdam, Laboratory for Clinical Cardiovascular Physiology, Department of Medical Biology, Amsterdam, The Netherlands; Amsterdam UMC, University of Amsterdam, Internal Medicine, Amsterdam, The Netherlands; MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK
| | - R V Immink
- Amsterdam UMC, University of Amsterdam, Anaesthesiology, Amsterdam, The Netherlands; Amsterdam UMC, University of Amsterdam, Laboratory for Clinical Cardiovascular Physiology, Department of Medical Biology, Amsterdam, The Netherlands
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Zamir M, Moir ME, Klassen SA, Balestrini CS, Shoemaker JK. Cerebrovascular Compliance Within the Rigid Confines of the Skull. Front Physiol 2018; 9:940. [PMID: 30065667 PMCID: PMC6056744 DOI: 10.3389/fphys.2018.00940] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 06/26/2018] [Indexed: 12/01/2022] Open
Abstract
Pulsatile blood flow is generally mediated by the compliance of blood vessels whereby they distend locally and momentarily to accommodate the passage of the pressure wave. This freedom of the blood vessels to exercise their compliance may be suppressed within the confines of the rigid skull. The effect of this on the mechanics of pulsatile blood flow within the cerebral circulation is not known, and the situation is compounded by experimental access difficulties. We present an approach which we have developed to overcome these difficulties in a study of the mechanics of pulsatile cerebral blood flow. The main finding is that while the innate compliance of cerebral vessels is indeed suppressed within the confines of the skull, this is compensated somewhat by compliance provided by other “extravascular” elements within the skull. The net result is what we have termed “intracranial compliance,” which we argue is more pertinent to the mechanics of pulsatile cerebral blood flow than is intracranial pressure.
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Affiliation(s)
- Mair Zamir
- Department of Applied Mathematics, The University of Western Ontario, London, ON, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada
| | - M Erin Moir
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Stephen A Klassen
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | | | - J Kevin Shoemaker
- School of Kinesiology, The University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada
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Grüne F, Klimek M. Cerebral blood flow and its autoregulation - when will there be some light in the black box? Br J Anaesth 2017; 119:1077-1079. [DOI: 10.1093/bja/aex355] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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