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Webb AJ, Klerman EB, Mandeville ET. Circadian and Diurnal Regulation of Cerebral Blood Flow. Circ Res 2024; 134:695-710. [PMID: 38484025 PMCID: PMC10942227 DOI: 10.1161/circresaha.123.323049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 01/30/2024] [Accepted: 02/07/2024] [Indexed: 03/17/2024]
Abstract
Circadian and diurnal variation in cerebral blood flow directly contributes to the diurnal variation in the risk of stroke, either through factors that trigger stroke or due to impaired compensatory mechanisms. Cerebral blood flow results from the integration of systemic hemodynamics, including heart rate, cardiac output, and blood pressure, with cerebrovascular regulatory mechanisms, including cerebrovascular reactivity, autoregulation, and neurovascular coupling. We review the evidence for the circadian and diurnal variation in each of these mechanisms and their integration, from the detailed evidence for mechanisms underlying the nocturnal nadir and morning surge in blood pressure to identifying limited available evidence for circadian and diurnal variation in cerebrovascular compensatory mechanisms. We, thus, identify key systemic hemodynamic factors related to the diurnal variation in the risk of stroke but particularly identify the need for further research focused on cerebrovascular regulatory mechanisms.
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Affiliation(s)
- Alastair J.S. Webb
- Department of Clinical Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford, United Kingdom (A.J.S.W.)
| | - Elizabeth B. Klerman
- Department of Clinical Neurosciences, Wolfson Centre for Prevention of Stroke and Dementia, University of Oxford, United Kingdom (A.J.S.W.)
- Department of Neurology, Massachusetts General Hospital, Boston (E.B.K.)
- Division of Sleep and Circadian Disorders, Department of Medicine, Brigham and Women’s Hospital, Boston, MA (E.B.K.)
- Division of Sleep Medicine, Harvard Medical School, Boston, MA (E.B.K.)
| | - Emiri T. Mandeville
- Departments of Radiology and Neurology, Neuroprotection Research Laboratories, Massachusetts General Hospital, Harvard Medical School, Boston (E.T.M.)
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2
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Carr JMJR, Hoiland RL, Fernandes IA, Schrage WG, Ainslie PN. Recent insights into mechanisms of hypoxia-induced vasodilatation in the human brain. J Physiol 2023. [PMID: 37655827 DOI: 10.1113/jp284608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 08/07/2023] [Indexed: 09/02/2023] Open
Abstract
The cerebral vasculature manages oxygen delivery by adjusting arterial blood in-flow in the face of reductions in oxygen availability. Hypoxic cerebral vasodilatation, and the associated hypoxic cerebral blood flow reactivity, involve many vascular, erythrocytic and cerebral tissue mechanisms that mediate elevations in cerebral blood flow via micro- and macrovascular dilatation. This contemporary review focuses on in vivo human work - with reference to seminal preclinical work where necessary - on hypoxic cerebrovascular reactivity, particularly where recent advancements have been made. We provide updates with the following information: in humans, hypoxic cerebral vasodilatation is partially mediated via a - likely non-obligatory - combination of: (1) nitric oxide synthases, (2) deoxygenation-coupled S-nitrosothiols, (3) potassium channel-related vascular smooth muscle hyperpolarization, and (4) prostaglandin mechanisms with some contribution from an interrelationship with reactive oxygen species. And finally, we discuss the fact that, due to the engagement of deoxyhaemoglobin-related mechanisms, reductions in O2 content via haemoglobin per se seem to account for ∼50% of that seen with hypoxic cerebral vasodilatation during hypoxaemia. We further highlight the issue that methodological impediments challenge the complete elucidation of hypoxic cerebral reactivity mechanisms in vivo in healthy humans. Future research is needed to confirm recent advancements and to reconcile human and animal findings. Further investigations are also required to extend these findings to address questions of sex-, heredity-, age-, and disease-related differences. The final step is to then ultimately translate understanding of these mechanisms into actionable, targetable pathways for the prevention and treatment of cerebral vascular dysfunction and cerebral hypoxic brain injury.
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Affiliation(s)
- Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Collaborative Entity for Researching Brain Ischemia (CEREBRI), University of British Columbia, Vancouver, British Columbia, Canada
| | - Igor A Fernandes
- Department of Health and Kinesiology, Purdue University, Indiana, USA
| | - William G Schrage
- Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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3
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Terrett LA, McIntyre L, Turgeon AF, English SW. Anemia and Red Blood Cell Transfusion in Aneurysmal Subarachnoid Hemorrhage. Neurocrit Care 2023; 39:91-103. [PMID: 37634181 DOI: 10.1007/s12028-023-01815-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/13/2023] [Indexed: 08/29/2023]
Abstract
Anemia is very common in aneurysmal subarachnoid hemorrhage (aSAH), with approximately half of the aSAH patient population developing moderate anemia during their hospital stay. The available evidence (both physiologic and clinical) generally supports an association of anemia with unfavorable outcomes. Although aSAH shares a number of common mechanisms of secondary insult with other forms of acute brain injury, aSAH also has specific features that make it unique: an early phase (in which early brain injury predominates) and a delayed phase (in which delayed cerebral ischemia and vasospasm predominate). The effects of both anemia and transfusion are potentially variable between these phases, which may have unique considerations and possibly different risk-benefit profiles. Data on transfusion in this population are almost exclusively limited to observational studies, which suffer from significant heterogeneity and risk of bias. Overall, the results are conflicting, with the balance of the studies suggesting that transfusion is associated with unfavorable outcomes. The transfusion targets that are well established in other critically ill populations should not be automatically applied to patients with aSAH because of the unique disease characteristics of this population and the limited representation of aSAH in the clinical trials that established these targets. There are two upcoming clinical trials evaluating transfusion in aSAH that should help clarify specific transfusion targets. Until then, it is reasonable to base transfusion decisions on the current guidelines and use an individualized approach incorporating physiologic and clinical data when available.
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Affiliation(s)
- Luke A Terrett
- School of Epidemiology and Public Health, University of Ottawa, Ottawa, ON, Canada
- College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
- Department of Adult Critical Care, Saskatchewan Health Authority, Saskatoon, SK, Canada
| | - Lauralyn McIntyre
- Department of Medicine (Critical Care), University of Ottawa, Ottawa, ON, Canada
- Clinical Epidemiology Program (CEP), Ottawa Hospital Research Institute (OHRI), Civic Campus Room F202, 1053 Carling Avenue, Ottawa, ON, K1Y 4E9, Canada
- The Ottawa Hospital, Ottawa, ON, Canada
| | - Alexis F Turgeon
- Department of Anesthesiology and Critical Care Medicine, Université Laval, Quebec City, QC, Canada
- Population Health and Optimal Health Practices Unit, Centre hospitalier universitaire de Québec-Université Laval Research Center, Quebec City, QC, Canada
| | - Shane W English
- Department of Medicine (Critical Care), University of Ottawa, Ottawa, ON, Canada.
- Clinical Epidemiology Program (CEP), Ottawa Hospital Research Institute (OHRI), Civic Campus Room F202, 1053 Carling Avenue, Ottawa, ON, K1Y 4E9, Canada.
- The Ottawa Hospital, Ottawa, ON, Canada.
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Taty TM, Mabiala JB, Lovett ME, Pongo J, Musungufu DA, Uchama M, O'Brien NF. Cerebral Blood Flow Velocity is Not Associated with Serum Hemoglobin in Children with Malaria-Associated Anemia. J Neuroimaging 2020; 30:463-467. [PMID: 32449973 DOI: 10.1111/jon.12715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 03/26/2020] [Accepted: 03/28/2020] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Hemoglobin (Hbg) is often thought to impact cerebral blood flow velocity (CBFV). This study was performed to investigate the relationship between Hbg value and CBFV in African children with malaria. METHODS In this prospective, observational study, children aged 3 months to 18 years with malaria and a normal Blantyre coma score underwent a single transcranial Doppler ultrasound (TCD) examination with a concurrent Hbg check. RESULTS One hundred fifty-six children with a mean age of 43 months were enrolled. Thirty-three children (21%) had severe anemia (Hbg <5g/dL), 46 (29%) had moderate anemia (Hbg 5-6.9 g/dL), 63 children (41%) had mild anemia (7-9.9 g/dL), and 14 children (9%) had no anemia (Hbg >10 g/dL) at the time of TCD examination. Mean averaged CBFV in the middle cerebral artery (MCA) for the cohort was 99% of predicted based on normative values standardized for age. There was no significant correlation between Hbg levels and measured CBFV in the MCA (r = -.09; 95% CI, -.24-.07; P = .29). CONCLUSION In a large sample of African children with malaria, Hbg did not correlate with CBFVs as measured by TCD. Future work that includes baseline TCD measurements and Hbg values as well as other physiological parameters known to influence CBFVs is necessary to confirm these findings.
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Affiliation(s)
- Tshimanga M Taty
- Departement de Pediatrie, Hopital Pediatrique de Kalembe Lembe, Cliniques Universitaires de Kinshasa, Kinshasa, Congo DR
| | - Joseph B Mabiala
- Departement de Pediatrie, Cliniques Universitaires de Kinshasa, Kinshasa, Congo DR
| | - Marlina E Lovett
- Department of Pediatrics, Division of Critical Care Medicine, Nationwide Children's Hospital, The Ohio State University, Columbus, OH
| | - Jean Pongo
- L'Hopital General de Reference de Lodja, Universite des Sciences et des Technologie de Lodja (USTL), Lodja, Sankuru, Congo DR
| | - Davin A Musungufu
- L'Hopital Generale de Reference de Nyankunde, Bukavu, South Kivu, Congo DR
| | - Mananu Uchama
- L'Hopital Generale de Reference de Nyankunde, Bukavu, South Kivu, Congo DR
| | - Nicole F O'Brien
- Department of Pediatrics, Division of Critical Care Medicine, Nationwide Children's Hospital, The Ohio State University, Columbus, OH
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Solheim SA, Bejder J, Breenfeldt Andersen A, Mørkeberg J, Nordsborg NB. Autologous Blood Transfusion Enhances Exercise Performance-Strength of the Evidence and Physiological Mechanisms. SPORTS MEDICINE-OPEN 2019; 5:30. [PMID: 31286284 PMCID: PMC6614299 DOI: 10.1186/s40798-019-0204-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 06/25/2019] [Indexed: 01/21/2023]
Abstract
This review critically evaluates the magnitude of performance enhancement that can be expected from various autologous blood transfusion (ABT) procedures and the underlying physiological mechanisms. The review is based on a systematic search, and it was reported that 4 of 28 studies can be considered of very high quality, i.e. placebo-controlled, double-blind crossover studies. However, both high-quality studies and other studies have generally reported performance-enhancing effects of ABT on exercise intensities ranging from ~70 to 100% of absolute peak oxygen uptake (VO2peak) with durations of 5–45 min, and the effect was also seen in well-trained athletes. A linear relationship exists between ABT volume and change in VO2peak. The likely correlation between ABT volume and endurance performance was not evident in the few available studies, but reinfusion of as little as 135 mL packed red blood cells has been shown to increase time trial performance. Red blood cell reinfusion increases endurance performance by elevating arterial oxygen content (CaO2). The increased CaO2 is accompanied by reduced lactate concentrations at submaximal intensities as well as increased VO2peak. Both effects improve endurance performance. Apparently, the magnitude of change in haemoglobin concentration ([Hb]) explains the increase in VO2peak associated with ABT because blood volume and maximal cardiac output have remained constant in the majority of ABT studies. Thus, the arterial-venous O2 difference during exercise must be increased after reinfusion, which is supported by experimental evidence. Additionally, it remains a possibility that ABT can enhance repeated sprint performance, but studies on this topic are lacking. The only available study did not reveal a performance-enhancing effect of reinfusion on 4 × 30 s sprinting. The reviewed studies are of importance for both the physiological understanding of how ABT interacts with exercise capacity and in relation to anti-doping efforts. From an anti-doping perspective, the literature review demonstrates the need for methods to detect even small ABT volumes.
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Affiliation(s)
- Sara Amalie Solheim
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark.,Anti Doping Denmark, Brøndby, Denmark
| | - Jacob Bejder
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark
| | - Andreas Breenfeldt Andersen
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark
| | | | - Nikolai Baastrup Nordsborg
- Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, 2100, Copenhagen, Denmark.
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Hoiland RL, Bain AR, Rieger MG, Bailey DM, Ainslie PN. Hypoxemia, oxygen content, and the regulation of cerebral blood flow. Am J Physiol Regul Integr Comp Physiol 2015; 310:R398-413. [PMID: 26676248 DOI: 10.1152/ajpregu.00270.2015] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 11/30/2015] [Indexed: 01/13/2023]
Abstract
This review highlights the influence of oxygen (O2) availability on cerebral blood flow (CBF). Evidence for reductions in O2 content (CaO2 ) rather than arterial O2 tension (PaO2 ) as the chief regulator of cerebral vasodilation, with deoxyhemoglobin as the primary O2 sensor and upstream response effector, is discussed. We review in vitro and in vivo data to summarize the molecular mechanisms underpinning CBF responses during changes in CaO2 . We surmise that 1) during hypoxemic hypoxia in healthy humans (e.g., conditions of acute and chronic exposure to normobaric and hypobaric hypoxia), elevations in CBF compensate for reductions in CaO2 and thus maintain cerebral O2 delivery; 2) evidence from studies implementing iso- and hypervolumic hemodilution, anemia, and polycythemia indicate that CaO2 has an independent influence on CBF; however, the increase in CBF does not fully compensate for the lower CaO2 during hemodilution, and delivery is reduced; and 3) the mechanisms underpinning CBF regulation during changes in O2 content are multifactorial, involving deoxyhemoglobin-mediated release of nitric oxide metabolites and ATP, deoxyhemoglobin nitrite reductase activity, and the downstream interplay of several vasoactive factors including adenosine and epoxyeicosatrienoic acids. The emerging picture supports the role of deoxyhemoglobin (associated with changes in CaO2 ) as the primary biological regulator of CBF. The mechanisms for vasodilation therefore appear more robust during hypoxemic hypoxia than during changes in CaO2 via hemodilution. Clinical implications (e.g., disorders associated with anemia and polycythemia) and future study directions are considered.
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Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan Campus, Kelowna, British Columbia, Canada; and
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan Campus, Kelowna, British Columbia, Canada; and
| | - Mathew G Rieger
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan Campus, Kelowna, British Columbia, Canada; and
| | - Damian M Bailey
- Neurovascular Research Laboratory, Research Institute of Science and Health, University of South Wales, Glamorgan, United Kingdom
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan Campus, Kelowna, British Columbia, Canada; and Neurovascular Research Laboratory, Research Institute of Science and Health, University of South Wales, Glamorgan, United Kingdom
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7
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Gottesman RF, Sojkova J, Beason-Held LL, An Y, Longo DL, Ferrucci L, Resnick SM. Patterns of regional cerebral blood flow associated with low hemoglobin in the Baltimore Longitudinal Study of Aging. J Gerontol A Biol Sci Med Sci 2012; 67:963-9. [PMID: 22552368 DOI: 10.1093/gerona/gls121] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Anemia has been associated with elevated cerebral blood flow (CBF) in animal models and certain clinical conditions (eg, renal disease), but whether hemoglobin level variations across a relatively normal range are associated with local or diffuse CBF changes is unclear. We investigated whether lower hemoglobin is associated with regional increases in relative CBF in older individuals, and if these increases occur in watershed regions. METHODS Seventy-four older nondemented adults underwent serial (15)O water positron emission tomography scans. Voxel-based analysis was used to investigate regional relative CBF patterns in association with hemoglobin level and in individuals with and without anemia. Analyses of cross-sectional relations between regional CBF and anemia were performed separately at two time points, 2 years apart, to identify replicable patterns of associations. RESULTS Restricting results to associations replicated across two cross-sectional analyses, lower hemoglobin was associated with higher relative CBF within the middle/inferior frontal, occipital, precuneus, and cerebellar regions. In addition, individuals with anemia (n = 15) showed higher relative CBF in superior frontal, middle temporal, hippocampal, and gyrus rectus regions than those without anemia. In some regions (right superior temporal gyrus, left inferior frontal gyrus, midline cuneus, and right precuneus); however, lower hemoglobin was associated with lower relative CBF. CONCLUSIONS In nondemented individuals, lower hemoglobin is associated with elevated relative CBF in specific cortical areas but reduced CBF in other areas. Whether this association between anemia and CBF in the absence of chronic diseases and in a normal physiologic range is related to clinical endpoints warrants further study.
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Affiliation(s)
- Rebecca F Gottesman
- Department of Neurology, Johns Hopkins University School of Medicine, Meyer 6-113, 600 North Wolfe Street, Baltimore, MD 21287, USA.
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8
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Mertes PM, Baumann A, Audibert G. [Transfusion in neurosurgery]. Transfus Clin Biol 2008; 15:205-11. [PMID: 18930420 DOI: 10.1016/j.tracli.2008.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Accepted: 09/04/2008] [Indexed: 10/21/2022]
Abstract
In neurosurgery, the question of the optimal transfusion "trigger" remains a controversial matter. Regarding the brain, the current data are still incomplete, justifying the continuation of experimental and clinical studies. The existing expert advices are based on these rather poor data and would probably evolve after the completion of clinical studies in progress. In spine surgery, the situation is simpler and the transfusional stakes are quite similar to those of orthopedics and traumatology. With regard to hemostasis, standardized recommendations exist depending on the laboratory test results or the anticoagulant treatments of the patient.
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Affiliation(s)
- P-M Mertes
- Département d'anesthésie-réanimation, hôpital Central, CHU de Nancy, Nancy, France.
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Hare GMT, Tsui AKY, McLaren AT, Ragoonanan TE, Yu J, Mazer CD. Anemia and cerebral outcomes: many questions, fewer answers. Anesth Analg 2008; 107:1356-70. [PMID: 18806052 DOI: 10.1213/ane.0b013e318184cfe9] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A number of clinical studies have associated acute anemia with cerebral injury in perioperative patients. Evidence of such injury has been observed near the currently accepted transfusion threshold (hemoglobin [Hb] concentration, 7-8 g/dL), and well above the threshold for cerebral tissue hypoxia (Hb 3-4 g/dL). However, hypoxic and nonhypoxic mechanisms of anemia-induced cerebral injury have not been clearly elucidated. In addition, protective mechanisms which may minimize cerebral injury during acute anemia have not been well defined. Vasodilatory mechanisms, including nitric oxide (NO), may help to maintain cerebral oxygen delivery during anemia as all three NO synthase (NOS) isoforms (neuronal, endothelial, and inducible NOS) have been shown to be up-regulated in different experimental models of acute hemodilutional anemia. Recent experimental evidence has also demonstrated an increase in an important transcription factor, hypoxia inducible factor (HIF)-1alpha, in the cerebral cortex of anemic rodents at clinically relevant Hb concentrations (Hb 6-7 g/dL). This suggests that cerebral oxygen homeostasis may be in jeopardy during acute anemia. Under hypoxic conditions, cytoplasmic HIF-1alpha degradation is inhibited, thereby allowing it to accumulate, dimerize, and translocate into the nucleus to promote transcription of a number of hypoxic molecules. Many of these molecules, including erythropoietin, vascular endothelial growth factor, and inducible NOS have also been shown to be up-regulated in the anemic brain. In addition, HIF-1alpha transcription can be increased by nonhypoxic mediators including cytokines and vascular hormones. Furthermore, NOS-derived NO may also stabilize HIF-1alpha in the absence of tissue hypoxia. Thus, during anemia, HIF-1alpha has the potential to regulate cerebral cellular responses under both hypoxic and normoxic conditions. Experimental studies have demonstrated that HIF-1alpha may have either neuroprotective or neurotoxic capacity depending on the cell type in which it is up-regulated. In the current review, we characterize these cellular processes to promote a clearer understanding of anemia-induced cerebral injury and protection. Potential mechanisms of anemia-induced injury include cerebral emboli, tissue hypoxia, inflammation, reactive oxygen species generation, and excitotoxicity. Potential mechanisms of cerebral protection include NOS/NO-dependent optimization of cerebral oxygen delivery and cytoprotective mechanisms including HIF-1alpha, erythropoietin, and vascular endothelial growth factor. The overall balance of these activated cellular mechanisms may dictate whether or not their up-regulation leads to cytoprotection or cellular injury during anemia. A clearer understanding of these mechanisms may help us target therapies that will minimize anemia-induced cerebral injury in perioperative patients.
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Affiliation(s)
- Gregory M T Hare
- Department of Anesthesia, University of Toronto, St. Michael's Hospital, 30 Bond Street, Toronto, ON M5B 1W8, Canada.
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Konstas AA, Neimark MA, Laine AF, Pile-Spellman J. A theoretical model of selective cooling using intracarotid cold saline infusion in the human brain. J Appl Physiol (1985) 2007; 102:1329-40. [PMID: 17170208 DOI: 10.1152/japplphysiol.00805.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A three-dimensional mathematical model was developed to examine the transient and steady-state temperature distribution in the human brain during selective brain cooling (SBC) by unilateral intracarotid freezing-cold saline infusion. To determine the combined effect of hemodilution and hypothermia from the cold saline infusion, data from studies investigating the effect of these two parameters on cerebral blood flow (CBF) were pooled, and an analytic expression describing the combined effect of the two factors was derived. The Pennes bioheat equation used the thermal properties of the different cranial layers and the effect of cold saline infusion on CBF to propagate the evolution of brain temperature. A healthy brain and a brain with stroke (ischemic core and penumbra) were modeled. CBF and metabolic rate data were reduced to simulate the core and penumbra. Simulations using different saline flow rates were performed. The results suggested that a flow rate of 30 ml/min is sufficient to induce moderate hypothermia within 10 min in the ipsilateral hemisphere. The brain with stroke cooled to lower temperatures than the healthy brain, mainly because the stroke limited the total intracarotid blood flow. Gray matter cooled twice as fast as white matter. The continuously falling hematocrit was the main time-limiting factor, restricting the SBC to a maximum of 3 h. The study demonstrated that SBC by intracarotid saline infusion is feasible in humans and may be the fastest method of hypothermia induction.
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11
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Menke J, Stöcker H, Sibrowski W. Cerebral oxygenation and hemodynamics during blood donation studied by near-infrared spectroscopy. Transfusion 2004; 44:414-21. [PMID: 14996201 DOI: 10.1111/j.1537-2995.2003.00663.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Blood donation is a safe human model for acute blood loss. This study investigated associated changes in regional cerebral oxygenation and cerebral blood volume (CBV) by near-infrared spectroscopy (NIRS). STUDY DESIGN AND METHODS Fifty healthy blood donors donated 450 mL of whole blood within 4 to 9 minutes. Changes in regional cerebral oxygen saturation (rSO2) and cerebral tissue Hb concentration (HbT) were semiquantitatively measured by NIRS. Venous Hb concentration was measured before and after blood donation. The predonation and postdonation CBV was estimated from HbT and venous Hb concentration. Differences between pre- and postdonation study parameters were analyzed by paired t tests (p < 0.05). RESULTS Within the study group, rSO2 decreased by 0.44 sat percent (p < 0.01) on average during blood donation, which is still within the range of individual physiologic baseline variation. The average venous Hb concentration decreased significantly by 4.6 percent, whereas HbT increased significantly by 2.5 percent and CBV increased even by 7.5 percent on average. CONCLUSION The increase in CBV indicates cerebral vasodilation, which seems to be the major compensation mechanism during acute blood loss. The decrease in rSO2 was relatively small, indicating that cerebral oxygenation was maintained within the physiologic range.
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Affiliation(s)
- J Menke
- Department of Transfusion Medicine, University Hospital, 48149 Münster, Germany.
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12
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Hsu LL, Miller ST, Wright E, Kutlar A, McKie V, Wang W, Pegelow CH, Driscoll C, Hurlet A, Woods G, Elsas L, Embury S, Adams RJ. Alpha Thalassemia is associated with decreased risk of abnormal transcranial Doppler ultrasonography in children with sickle cell anemia. J Pediatr Hematol Oncol 2003; 25:622-8. [PMID: 12902915 DOI: 10.1097/00043426-200308000-00007] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE Cerebrovascular complications of sickle cell disease (SCD) are common, but the risk factors remain unclear. The multicenter Stroke Prevention Trial in Sickle Cell Anemia (STOP) provided an opportunity to examine alpha thalassemia-2 as a modifying risk factor, using abnormal transcranial Doppler ultrasonography (TCD) as a surrogate marker for cerebrovascular disease. The authors hypothesized that children with abnormal TCD are less likely to have alpha thalassemia-2, and an increased hemoglobin level accounts for this protective effect. METHODS A retrospective study was conducted of children with SCD who had both alpha gene and TCD data from STOP: 128 with TCD of at least 200 cm/s (abnormal TCD) and 172 with TCD less than 170 cm/s (normal TCD). RESULTS Alpha thalassemia-2 was more frequent in the normal TCD group compared with the abnormal TCD group. The odds ratio for normal TCD and alpha thalassemia-2 was 4.1. Adjusting for either hemoglobin level or red cell size (mean corpuscular volume) reduced the odds ratio only slightly. Age, normal TCD, and alpha thalassemia-2 had significant statistical interaction, so that alpha thalassemia-2 was not related to TCD for age 10 years or older. CONCLUSIONS The frequency of alpha thalassemia-2 was significantly higher in children with normal TCD. Speculation on mechanisms of effect includes improved erythrocyte deformability, reduced red cell adhesion, and reduced nitric oxide scavenging in alpha thalassemia-2. The association of alpha thalassemia-2 and normal TCD adds to the evidence on the protective effects of alpha thalassemia-2 in SCD and highlights the contribution of epistatic factors.
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Affiliation(s)
- Lewis L Hsu
- Emory University School of Medicine and Georgia Comprehensive Sickle Cell Center, Atlanta, Georgia 30303, USA
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13
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Vavilala MS, Lee LA, Morris GP, Lam AM. Cerebral autoregulation before and after blood transfusion in a child. J Neurosurg Anesthesiol 2001; 13:233-6. [PMID: 11426098 DOI: 10.1097/00008506-200107000-00009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The authors present the case of an anemic 22-month-old child undergoing lower extremity surgery in whom the lower limit of cerebral autoregulation was shifted to the right.
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Affiliation(s)
- M S Vavilala
- Department of Anesthesiology, Harborview Medical Center, University of Washington School of Medicine, Seattle, Washington 98104, USA
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