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Quantifying the speed of fluctuations in systolic blood pressure. Hypertens Res 2013; 36:1039-44. [PMID: 23784510 DOI: 10.1038/hr.2013.62] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 03/21/2013] [Accepted: 04/14/2013] [Indexed: 11/08/2022]
Abstract
Increased blood pressure variability (BPV), even in the absence of hypertension, has been identified as an important independent cardiovascular risk factor (CVRF). However, the role of the speed of changes in systolic blood pressure (SBP; vSBP) on cardiovascular risk needs to be investigated. The objective of this study was to investigate whether subjects with a high cardiovascular risk profile have an increased degree and speed of changes in SBP compared with subjects with low or no risk. Resting beat-to-beat blood pressure (BP) was recorded for 5 min. Standard BPV measures in both time and frequency domains were conducted. The s.d. of SBP (s.d.-SBP) values was used to quantify the degree of BPV. vSBP was assessed by calculating the slopes of oscillatory fluctuations in SBP for different interbeat intervals (IBI). Subjects were allocated to one of four groups according to the number of CVRFs (0, 1, 2, ≥ 3 CVRF). Of 122 subjects, 19.7% had 0 CVRF, 27.0% had 1, 32.0% had 2 and 21.3% had ≥ 3 CVRFs. There was an increase in vSBP across the four risk groups. The vSBP in patients without CVRF was 3.12 (1.09), 1 CVRF 3.23 (1.07), 2 CVRF 4.16 (2.26) and ≥ 3 CVRF 4.22 (1.66; P = 0.015). The s.d.-SBP was not significantly different between the cardiovascular risk groups. The speed of fluctuations in SBP rather than the degree of BPV is pronounced in patients with elevated cardiovascular risk. Increased speed of BP fluctuations may thus be a contributing mechanism to cardiovascular morbidity.
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Genny SRK, Elangovan P, Kapadia N, Rajagopalan BK. Posterior reversible encephalopathy syndrome following cardiopulmonary bypass–a case report. Indian J Thorac Cardiovasc Surg 2013. [DOI: 10.1007/s12055-013-0183-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Li Y, Gor D, Walicki D, Jenny D, Jones D, Barbour P, Castaldo J. Spectrum and Potential Pathogenesis of Reversible Posterior Leukoencephalopathy Syndrome. J Stroke Cerebrovasc Dis 2012; 21:873-82. [PMID: 21703874 DOI: 10.1016/j.jstrokecerebrovasdis.2011.05.010] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 05/09/2011] [Indexed: 10/18/2022] Open
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Abstract
OBJECTIVES We have sought to develop an automated methodology for the continuous updating of optimal cerebral perfusion pressure (CPPopt) for patients after severe traumatic head injury, using continuous monitoring of cerebrovascular pressure reactivity. We then validated the CPPopt algorithm by determining the association between outcome and the deviation of actual CPP from CPPopt. DESIGN Retrospective analysis of prospectively collected data. SETTING Neurosciences critical care unit of a university hospital. PATIENTS A total of 327 traumatic head-injury patients admitted between 2003 and 2009 with continuous monitoring of arterial blood pressure and intracranial pressure. MEASUREMENTS AND MAIN RESULTS Arterial blood pressure, intracranial pressure, and CPP were continuously recorded, and pressure reactivity index was calculated online. Outcome was assessed at 6 months. An automated curve fitting method was applied to determine CPP at the minimum value for pressure reactivity index (CPPopt). A time trend of CPPopt was created using a moving 4-hr window, updated every minute. Identification of CPPopt was, on average, feasible during 55% of the whole recording period. Patient outcome correlated with the continuously updated difference between median CPP and CPPopt (chi-square=45, p<.001; outcome dichotomized into fatal and nonfatal). Mortality was associated with relative "hypoperfusion" (CPP<CPPopt), severe disability with "hyperperfusion" (CPP>CPPopt), and favorable outcome was associated with smaller deviations of CPP from the individualized CPPopt. While deviations from global target CPP values of 60 mm Hg and 70 mm Hg were also related to outcome, these relationships were less robust. CONCLUSIONS Real-time CPPopt could be identified during the recording time of majority of the patients. Patients with a median CPP close to CPPopt were more likely to have a favorable outcome than those in whom median CPP was widely different from CPPopt. Deviations from individualized CPPopt were more predictive of outcome than deviations from a common target CPP. CPP management to optimize cerebrovascular pressure reactivity should be the subject of future clinical trial in severe traumatic head-injury patients.
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Koller A, Toth P. Contribution of flow-dependent vasomotor mechanisms to the autoregulation of cerebral blood flow. J Vasc Res 2012; 49:375-89. [PMID: 22739136 PMCID: PMC3586555 DOI: 10.1159/000338747] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 04/04/2012] [Indexed: 11/19/2022] Open
Abstract
Regulation of cerebral blood flow (CBF) is the result of multilevel mechanisms to maintain the appropriate blood supply to the brain while having to comply with the limited space available in the cranium. The latter requirement is ensured by the autoregulation of CBF, in which the pressure-sensitive myogenic response is known to play a pivotal role. However, in vivo increases in pressure are accompanied by increases in flow; yet the effects of flow on the vasomotor tone of cerebral vessels are less known. Earlier studies showed flow-sensitive dilation and/or constriction or both, but no clear picture emerged. Recently, the important role of flow-sensitive mechanism(s) eliciting the constriction of cerebral vessels has been demonstrated. This review focuses on the effect of hemodynamic forces (especially intraluminal flow) on the vasomotor tone of cerebral vessels and the underlying cellular and molecular mechanisms. A novel concept of autoregulation of CBF is proposed, suggesting that (in certain areas of the cerebrovascular tree) pressure- and flow-induced constrictions together maintain an effective autoregulation, and that alterations in these mechanisms may contribute to the development of cerebrovascular disorders. Future studies are warranted to explore the signals, the details of signaling processes and the in vivo importance of these mechanisms.
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Affiliation(s)
- Akos Koller
- Department of Pathophysiology and Gerontology, Medical School, University of Pécs, Pécs, Hungary.
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McKinney AM, Sarikaya B, Gustafson C, Truwit CL. Detection of microhemorrhage in posterior reversible encephalopathy syndrome using susceptibility-weighted imaging. AJNR Am J Neuroradiol 2012; 33:896-903. [PMID: 22241378 DOI: 10.3174/ajnr.a2886] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE PRES-related vasogenic edema is potentially reversible while hemorrhage occurs in only 15.2%-17.3% of patients. However, the true incidence of hemorrhage could be higher when SWI is considered. Thus, we set out to determine the incidence of MH, SAH, and IPH in PRES by using SWI and to particularly evaluate whether such MHs are reversible. MATERIALS AND METHODS Thirty-one patients with PRES and SWI were included, 17 having follow-up SWI. Two neuroradiologists reviewed SWI, FLAIR, DWI, and CE-T1WI. The presence and number of MHs (<5 mm) on SWI, SAH, and IPH (>5 mm) were recorded at presentation and follow-up. We evaluated associations between the presence of MH on SWI and DWI lesions, SAH, IPH, contrast enhancement, and MR imaging severity. RESULTS Hemorrhage was present in 20/31 patients (64.5%), with MHs on SWI in 18/31 (58.1%) at presentation and in 11/17 (64.7%) at follow-up. SAH was present in 3/31 on SWI and 4/31 on FLAIR, while 2/31 had IPH. At follow-up, no patients had acquired new MHs; 2/5 MHs in 1 patient resolved. Four patients with available SWI before PRES developed MHs after PRES onset. No association was found between the presence of MHs on SWI and DWI, SAH, IPH, enhancement, and MR imaging severity (all P > .05). CONCLUSIONS SWI showed a higher rate of MH than previously described, underscoring the potential of SWI in evaluating PRES. Such MHs typically persist and may develop after PRES onset. However, the clinical relevance of MHs in PRES is yet to be determined. We propose that MHs in PRES relate to endothelial cell dysfunction.
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Affiliation(s)
- A M McKinney
- Department of Radiology, University of Minnesota, MMC 292, 420 Delaware St SE, Minneapolis, MN 55455, USA.
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Schmidt JM, Claassen J. Clinical utility of brain tissue oxygen tension in treatment of brain injury more complicated than it appears. Clin Neurophysiol 2011; 123:1060-2. [PMID: 22119796 DOI: 10.1016/j.clinph.2011.10.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Revised: 10/14/2011] [Accepted: 10/19/2011] [Indexed: 10/15/2022]
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Asymmetric Posterior Reversible Encephalopathy Syndrome Complicating Hemodynamic Augmentation for Subarachnoid Hemorrhage-Associated Cerebral Vasospasm. Neurocrit Care 2011; 15:542-6. [DOI: 10.1007/s12028-011-9635-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Sheta MA, Paladugu M, Mendelson J, Holland NR. When should nitroglycerine be avoided in hypertensive encephalopathy? Hypertension 2011; 58:e187-8. [PMID: 21931071 DOI: 10.1161/hypertensionaha.111.175703] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Ogoh S, Sato K, Fisher JP, Seifert T, Overgaard M, Secher NH. The effect of phenylephrine on arterial and venous cerebral blood flow in healthy subjects. Clin Physiol Funct Imaging 2011; 31:445-51. [DOI: 10.1111/j.1475-097x.2011.01040.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Brassard P, Seifert T, Wissenberg M, Jensen PM, Hansen CK, Secher NH. Phenylephrine decreases frontal lobe oxygenation at rest but not during moderately intense exercise. J Appl Physiol (1985) 2010; 108:1472-8. [DOI: 10.1152/japplphysiol.01206.2009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whether sympathetic activity influences cerebral blood flow (CBF) and oxygenation remains controversial. The influence of sympathetic activity on CBF and oxygenation was evaluated by the effect of phenylephrine on middle cerebral artery (MCA) mean flow velocity ( Vmean) and the near-infrared spectroscopy-derived frontal lobe oxygenation (ScO2) at rest and during exercise. At rest, nine healthy male subjects received bolus injections of phenylephrine (0.1, 0.25, and 0.4 mg), and changes in mean arterial pressure (MAP), MCA Vmean, internal jugular venous O2 saturation (SjvO2), ScO2, and arterial Pco2 (PaCO2) were measured and the cerebral metabolic rate for O2 (CMRO2) was calculated. In randomized order, a bolus of saline or 0.3 mg of phenylephrine was then injected during semisupine cycling, eliciting a low (∼110 beats/min) or a high (∼150 beats/min) heart rate. At rest, MAP and MCA Vmean increased ∼20% ( P < 0.001) and ∼10% ( P < 0.001 for 0.25 mg of phenylephrine and P < 0.05 for 0.4 mg of phenylephrine), respectively. ScO2 then decreased ∼7% ( P < 0.001). Phenylephrine had no effect on SjvO2, PaCO2, or CMRO2. MAP increased after the administration of phenylephrine during low-intensity exercise (∼15%), but this was attenuated (∼10%) during high-intensity exercise ( P < 0.001). The reduction in ScO2 after administration of phenylephrine was attenuated during low-intensity exercise (−5%, P < 0.001) and abolished during high-intensity exercise (−3%, P = not significant), where PaCO2 decreased 7% ( P < 0.05) and CMRO2 increased 17% ( P < 0.05). These results suggest that the administration of phenylephrine reduced ScO2 but that the increased cerebral metabolism needed for moderately intense exercise eliminated that effect.
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Affiliation(s)
- Patrice Brassard
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Seifert
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Mads Wissenberg
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Peter M. Jensen
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Christian K. Hansen
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Niels H. Secher
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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63
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Ainslie PN, Tzeng YC. On the regulation of the blood supply to the brain: old age concepts and new age ideas. J Appl Physiol (1985) 2010; 108:1447-9. [PMID: 20299620 DOI: 10.1152/japplphysiol.00257.2010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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64
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Rothwell PM. Limitations of the usual blood-pressure hypothesis and importance of variability, instability, and episodic hypertension. Lancet 2010; 375:938-48. [PMID: 20226991 DOI: 10.1016/s0140-6736(10)60309-1] [Citation(s) in RCA: 518] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Although hypertension is the most prevalent treatable vascular risk factor, how it causes end-organ damage and vascular events is poorly understood. Yet, a widespread belief exists that underlying usual blood pressure can alone account for all blood-pressure-related risk of vascular events and for the benefits of antihypertensive drugs, and this notion has come to underpin all major clinical guidelines on diagnosis and treatment of hypertension. Other potentially informative measures, such as variability in clinic blood pressure or maximum blood pressure reached, have been neglected, and effects of antihypertensive drugs on such measures are largely unknown. Clinical guidelines recommend that episodic hypertension is not treated, and the potential risks of residual variability in blood pressure in treated hypertensive patients have been ignored. This Review discusses shortcomings of the usual blood-pressure hypothesis, provides background to accompanying reports on the importance of blood-pressure variability in prediction of risk of vascular events and in accounting for benefits of antihypertensive drugs, and draws attention to clinical implications and directions for future research.
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Affiliation(s)
- Peter M Rothwell
- Stroke Prevention Research Unit, University Department of Clinical Neurology, John Radcliffe Hospital, Headington, Oxford, UK.
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65
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Choi HS, Cho YM, Kang JH, Shin CS, Park KS, Lee HK. Cerebral white matter hyperintensity is mainly associated with hypertension among the components of metabolic syndrome in Koreans. Clin Endocrinol (Oxf) 2009; 71:184-8. [PMID: 19178513 DOI: 10.1111/j.1365-2265.2008.03444.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Cerebral white matter hyperintensity (WMH) is a common abnormality in brain magnetic resonance imaging (MRI) and is known to be associated with ischaemic stroke. Previous studies revealed that the risk factors for cerebral WMH were age, female gender, hypertension and diabetes. In this study we examined the association between cerebral WMH and metabolic syndrome, a cluster of hypertension, glucose intolerance, abdominal obesity and dyslipidaemia. METHODS AND RESULTS We reviewed the results of brain MRI of 5498 subjects who underwent routine check-ups including laboratory tests at the Seoul National University Health Care System. Among the subjects who met the inclusion criteria (n = 5104), 1693 (33.2%) had cerebral WMH. They were characterized by old age, female predominance, higher body mass index (BMI), larger waist circumference, higher blood pressure, higher fasting plasma glucose level, and higher haemoglobin A1c (HbA1c). In multivariate analyses, age, female gender and hypertension were the independent risk factors for cerebral WMH. Metabolic syndrome was associated with cerebral WMH after adjusting for age and gender [odds ratio (OR) 1.20, 95% confidence interval (CI) 1.04-1.39, P = 0.014]. Among the components of metabolic syndrome, hypertension was independently associated with cerebral WMH (OR 1.20, 95% CI 1.05-1.38, P = 0.007). CONCLUSION Age, female gender and hypertension were risk factors for cerebral WMH in the Korean population. Cerebral WMH was also associated with metabolic syndrome; however, metabolic syndrome offered no advantage over hypertension alone in predicting cerebral WMH.
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Affiliation(s)
- Hoon Sung Choi
- Department of Internal Medicine, Seoul National University College of Medicine, Chongno-gu, Seoul, South Korea
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67
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Johansson BB. The blood-brain barrier and cerebral blood flow in acute hypertension. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 678:107-12. [PMID: 6584009 DOI: 10.1111/j.0954-6820.1984.tb08668.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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68
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Strandgaard S, Jones JV, MacKenzie ET, Graham DI, Farrar JK. The sausage-string pattern in the pial vessels in acute, angiotensin-induced hypertension--vasospasm or vasodilatation? ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 602:9-12. [PMID: 1071958 DOI: 10.1111/j.0954-6820.1977.tb07632.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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A model of brain circulation and metabolism: NIRS signal changes during physiological challenges. PLoS Comput Biol 2008; 4:e1000212. [PMID: 18989392 PMCID: PMC2573000 DOI: 10.1371/journal.pcbi.1000212] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Accepted: 09/23/2008] [Indexed: 11/19/2022] Open
Abstract
We construct a model of brain circulation and energy metabolism. The model is designed to explain experimental data and predict the response of the circulation and metabolism to a variety of stimuli, in particular, changes in arterial blood pressure, CO(2) levels, O(2) levels, and functional activation. Significant model outputs are predictions about blood flow, metabolic rate, and quantities measurable noninvasively using near-infrared spectroscopy (NIRS), including cerebral blood volume and oxygenation and the redox state of the Cu(A) centre in cytochrome c oxidase. These quantities are now frequently measured in clinical settings; however the relationship between the measurements and the underlying physiological events is in general complex. We anticipate that the model will play an important role in helping to understand the NIRS signals, in particular, the cytochrome signal, which has been hard to interpret. A range of model simulations are presented, and model outputs are compared to published data obtained from both in vivo and in vitro settings. The comparisons are encouraging, showing that the model is able to reproduce observed behaviour in response to various stimuli.
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70
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Carlson BE, Arciero JC, Secomb TW. Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses. Am J Physiol Heart Circ Physiol 2008; 295:H1572-9. [PMID: 18723769 DOI: 10.1152/ajpheart.00262.2008] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The autoregulation of blood flow, the maintenance of almost constant blood flow in the face of variations in arterial pressure, is characteristic of many tissue types. Here, contributions to the autoregulation of pressure-dependent, shear stress-dependent, and metabolic vasoactive responses are analyzed using a theoretical model. Seven segments, connected in series, represent classes of vessels: arteries, large arterioles, small arterioles, capillaries, small venules, large venules, and veins. The large and small arterioles respond actively to local changes in pressure and wall shear stress and to the downstream metabolic state communicated via conducted responses. All other segments are considered fixed resistances. The myogenic, shear-dependent, and metabolic responses of the arteriolar segments are represented by a theoretical model based on experimental data from isolated vessels. To assess autoregulation, the predicted flow at an arterial pressure of 130 mmHg is compared with that at 80 mmHg. If the degree of vascular smooth muscle activation is held constant at 0.5, there is a fivefold increase in blood flow. When myogenic variation of tone is included, flow increases by a factor of 1.66 over the same pressure range, indicating weak autoregulation. The inclusion of both myogenic and shear-dependent responses results in an increase in flow by a factor of 2.43. A further addition of the metabolic response produces strong autoregulation with flow increasing by a factor of 1.18 and gives results consistent with experimental observation. The model results indicate that the combined effects of myogenic and metabolic regulation overcome the vasodilatory effect of the shear response and lead to the autoregulation of blood flow.
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Affiliation(s)
- Brian E Carlson
- Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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71
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Shah AK, Rajamani K, Whitty JE. Eclampsia: a neurological perspective. J Neurol Sci 2008; 271:158-67. [PMID: 18495165 DOI: 10.1016/j.jns.2008.04.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 03/28/2008] [Accepted: 04/08/2008] [Indexed: 01/17/2023]
Abstract
Eclampsia is a poorly understood disorder characterized by seizures or unexplained coma in setting of gestational hypertension. Its neurological manifestations are varied and are an important cause of the morbidity and mortality associated. We present a comprehensive prospective study of forty women recruited over four years describing neurological symptoms and signs, neuroimaging and laboratory studies as well as prognosis including 3-6 months follow-up. The seizures occurred in the postpartum period in majority of women (55%), while 45% had seizures before labor, and the rest (5%) during labor. Interestingly, one third of the women suffered their first seizures more than 48 h postpartum (late postpartum eclampsia). A sizable minority suffered more than one seizure and some had documented partial seizures. Headache preceded seizures by more than a day and was described as throbbing or pounding pain by most. The visual symptoms in decreasing frequency were blurring, blindness, scotoma and visual processing deficits. The most common finding during the neurological exam was memory deficits, followed by increased deep tendon reflexes (asymmetric in some), visual perception deficits, visual information processing deficits, altered mental status and cranial nerve deficits. Intracranial or intraspinal pressure when examined was elevated. Among neuroimaging studies, MRI was more sensitive compared to CT scan. The MRI abnormalities included both white as well as gray matter and the most common location of abnormalities was high frontal/parietal lobe. The laboratory studies revealed proteinuria in majority, but not in all. The liver function tests were abnormal in many, while few patients had HELLP syndrome. The neurological deficits resolved by the time of discharge in all. At follow-up, some patients developed new neurological problems such as recurrent headaches or seizures.
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Affiliation(s)
- A K Shah
- Department of Neurology, Wayne State University/Detroit Medical Center, Detroit, MI 48201, United States.
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Bartynski WS. Posterior reversible encephalopathy syndrome, part 2: controversies surrounding pathophysiology of vasogenic edema. AJNR Am J Neuroradiol 2008; 29:1043-9. [PMID: 18403560 DOI: 10.3174/ajnr.a0929] [Citation(s) in RCA: 694] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic state accompanied by a unique brain imaging pattern typically associated with a number of complex clinical conditions including: preeclampsia/eclampsia, allogeneic bone marrow transplantation, solid organ transplantation, autoimmune diseases and high dose cancer chemotherapy. The mechanism behind the developing vasogenic edema and CT or MR imaging appearance of PRES is not known. Two theories have historically been proposed: 1) Severe hypertension leads to failed auto-regulation, subsequent hyperperfusion, with endothelial injury/vasogenic edema and; 2) vasoconstriction and hypoperfusion leads to brain ischemia and subsequent vasogenic edema. The strengths/weaknesses of these hypotheses are reviewed in a translational fashion including supporting evidence and current available imaging/clinical data related to the conditions that develop PRES. While the hypertension/hyperperfusion theory has been most popular, the conditions associated with PRES have a similar immune challenge present and develop a similar state of T-cell/endothelial cell activation that may be the basis of leukocyte trafficking and systemic/cerebral vasoconstriction. These systemic features along with current vascular and perfusion imaging features in PRES appear to render strong support for the older theory of vasoconstriction coupled with hypoperfusion as the mechanism.
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Affiliation(s)
- W S Bartynski
- Department of Radiology, Division of Neuroradiology, University of Pittsburgh, Presbyterian University Hospital, Pittsburgh, PA 15213, USA.
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73
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Bartynski WS, Boardman JF. Catheter angiography, MR angiography, and MR perfusion in posterior reversible encephalopathy syndrome. AJNR Am J Neuroradiol 2007; 29:447-55. [PMID: 18079186 DOI: 10.3174/ajnr.a0839] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND AND PURPOSE The cause of posterior reversible encephalopathy syndrome (PRES) is unknown. Two primary hypotheses exist: 1) hypertension exceeding auto-regulatory limits leading to forced hyper-perfusion and 2) vasoconstriction and hypo-perfusion leading to ischemia with resultant edema. The purpose of this study was to evaluate the catheter angiography (CA), MR angiography (MRA), and MR perfusion (MRP) features in PRES in order to render further insight into its mechanism of origin. MATERIALS AND METHODS In 47 patients with PRES, 9 CAs and 43 MRAs were evaluated for evidence of vasculopathy (vasoconstriction and vasodilation), and 15 MRP studies were evaluated for altered relative cerebral blood volume (rCBV) in PRES lesions and regions. Visualization of vessels on MRA and toxicity blood pressures were compared with the extent of hemispheric vasogenic edema. RESULTS Vasculopathy was present in 8 of 9 patients on CA (direct correlation to MRA in 3/6 patients). At MRA, moderate to severe vessel irregularity consistent with vasoconstriction and vasodilation was present in 30 of 43 patients and vessel pruning or irregularity in 7 patients, with follow-up MRA demonstrating reversal of vasoconstriction or vasodilation in 9 of 11 patients. Vasogenic edema was less in patients with hypertension compared with patients who were normotensive. Preserved normal length of the posterior cerebral artery (PCA) was commonly seen in patients with severe hypertension despite diffuse or focal vasoconstriction or vasodilation. In these patients, lengthier visualization of the distal PCA correlated with a lower grade of hemispheric edema (P = .002). Cortical rCBV was significantly reduced in 51 of 59 PRES lesions and regions compared with a healthy reference cortex (average 61% of reference cortex) with mild decrease in the remainder. CONCLUSION Vasculopathy was a common finding on CA and MRA in our patients with PRES, and MRP demonstrated reduced cortical rCBV in PRES lesions. Vasogenic edema was reduced in patients with hypertension, and superior distal PCA visualization correlated with reduced hemispheric edema in patients with PRES and severe hypertension.
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Affiliation(s)
- W S Bartynski
- Department of Radiology, Division of Neuroradiology, University of Pittsburgh, Presbyterian University Hospital, Pittsburgh, PA 15213, USA.
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McKinney AM, Short J, Truwit CL, McKinney ZJ, Kozak OS, SantaCruz KS, Teksam M. Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings. AJR Am J Roentgenol 2007; 189:904-12. [PMID: 17885064 DOI: 10.2214/ajr.07.2024] [Citation(s) in RCA: 464] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE Posterior reversible encephalopathy syndrome (PRES) is classically characterized as symmetric parietooccipital edema but may occur in other distributions with varying imaging appearances. This study determines the incidence of atypical and typical regions of involvement and unusual imaging manifestations. MATERIALS AND METHODS Seventy-six patients were eventually included as having confirmed PRES from 111 initially suspected cases, per imaging and clinical follow-up. Two neuroradiologists retrospectively reviewed each MR image. Standard sequences were unenhanced FLAIR and T1- and T2-weighted images in all patients, with diffusion-weighted imaging (n = 75) and contrast-enhanced T1-weighted imaging (n = 69) in most. The regions involved were recorded on the basis of FLAIR findings, and the presence of atypical imaging findings (contrast enhancement, restricted diffusion, hemorrhage) was correlated with the severity (extent) of hyperintensity or mass effect on FLAIR. RESULTS The incidence of regions of involvement was parietooccipital, 98.7%; posterior frontal, 78.9%; temporal, 68.4%; thalamus, 30.3%; cerebellum, 34.2%; brainstem, 18.4%; and basal ganglia, 11.8%. The incidence of less common manifestations was enhancement, 37.7%; restricted diffusion, 17.3%; hemorrhage, 17.1%; and a newly described unilateral variant, 2.6%. Poor correlation was found between edema severity and enhancement (r = 0.072), restricted diffusion (r = 0.271), hemorrhage (r = 0.267), blood pressure (systolic, r = 0.13; diastolic, r = 0.02). Potentially new PRES causes included contrast-related anaphylaxis and alcohol withdrawal. CONCLUSION This large series of PRES cases shows that atypical distributions and imaging manifestations of PRES have a higher incidence than commonly perceived, and atypical manifestations do not correlate well with the edema severity.
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Affiliation(s)
- Alexander M McKinney
- Department of Radiology and Neuroradiology, University of Minnesota Medical Center, Minneapolis, MN, USA.
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75
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Euser AG, Bullinger L, Cipolla MJ. Magnesium sulphate treatment decreases blood-brain barrier permeability during acute hypertension in pregnant rats. Exp Physiol 2007; 93:254-61. [PMID: 17933863 DOI: 10.1113/expphysiol.2007.039966] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Eclampsia is associated with increased blood-brain barrier (BBB) permeability and formation of cerebral oedema. Magnesium sulphate is used to treat eclampsia despite an unclear mechanism of action. This study was to determine the effect of magnesium sulphate on in vivo BBB permeability and formation of cerebral oedema during acute hypertension and on brain aquaporin-4 (AQP4) protein expression. An in vivo model of hypertensive encephalopathy was used in late-pregnant (LP) rats following magnesium sulphate treatment, 270 mg kg(-1) i.p. injection every 4 h for 24 h. Permeability of the BBB was determined by in situ brain perfusion of Evan's Blue (EB) and sodium fluorescein (NaFl), and dye clearance determined by fluorescence spectrophotometry. Cerebral oedema was determined following acute hypertension by measuring brain water content. The effect of magnesium treatment on AQP4 expression was determined by Western blot analysis. Acute hypertension with autoregulatory breakthrough increased BBB permeability to EB in both brain regions studied (P < 0.05). Magnesium attenuated BBB permeability to EB during acute hypertension by 41% in the posterior cerebrum (P < 0.05) but had no effect in the anterior cerebrum (P > 0.05). Treatment with magnesium did not change NaFl permeability, cerebral oedema formation or AQP4 expression. In summary, BBB permeability to Evan's Blue was increased by acute hypertension in LP rats, and this was attenuated by treatment with magnesium sulphate. The greatest effect on BBB permeability to EB was in the posterior cerebrum, an area particularly susceptible to oedema formation during eclampsia.
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Affiliation(s)
- Anna G Euser
- University of Vermont, Department of Neurology, 89 Beaumont Avenue, Given C454, Burlington, VT 05405, USA
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77
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Abstract
Stroke is the third most common cause of death in developed countries. In England and Wales, 1000 people under the age of 30 have a stroke each year. Cocaine is the most commonly used class A drug, and the first report of cocaine-induced stroke was in 1977. Since the development of alkaloidal "crack" cocaine in the 1980s, there has been a significant rise in the number of case reports describing both ischaemic and haemorrhagic stroke associated with cocaine use. Cocaine is a potent central nervous system stimulant, and acts by binding to specific receptors at pre-synaptic sites preventing the reuptake of neurotransmitters. The exact mechanism of cocaine-induced stroke remains unclear and there are likely to be a number of factors involved including vasospasm, cerebral vasculitis, enhanced platelet aggregation, cardioembolism, and hypertensive surges associated with altered cerebral autoregulation. The evidence surrounding each of these factors will be considered here.
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Affiliation(s)
- Sean D Treadwell
- Department of Integrated Medicine, University Hospitals of Leicester NHS Trust, Leicester Royal Infirmary, Leicester, UK.
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78
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Talman WT, Nitschke Dragon D. Neuronal nitric oxide mediates cerebral vasodilatation during acute hypertension. Brain Res 2007; 1139:126-32. [PMID: 17291465 PMCID: PMC1885240 DOI: 10.1016/j.brainres.2007.01.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 10/09/2006] [Accepted: 10/16/2006] [Indexed: 12/21/2022]
Abstract
Parasympathetic nerves from the pterygopalatine ganglia provide nitroxidergic innervation to forebrain cerebral blood vessels. Disruption of that innervation attenuates cerebral vasodilatation seen during acute hypertension as does systemic administration of a non-selective nitric oxide synthase (NOS) inhibitor. Although such studies suggest that nitric oxide (NO) released from parasympathetic nerves participates in vasodilatation of cerebral vessels during hypertension, that hypothesis has not been tested with selective local inhibition of neuronal NOS (nNOS). We tested that hypothesis through these studies performed in anesthetized rats instrumented for continuous measurement of blood pressure, heart rate and pial arterial diameter through a cranial window. We sought to determine if the nNOS inhibitor propyl-L-arginine delivered directly to the outer surface of a pial artery would (1) attenuate changes in pial arterial diameter during acute hypertension and (2) block nNOS-mediated dilator effects of N-methyl-D-aspartate (NMDA) delivered into the window but (3) not block vasodilatation elicited by acetylcholine (ACh) and mediated by endothelial NOS dilator. Without the nNOS inhibitor arterial diameter abruptly increased 70+/-15% when mean arterial pressure (MAP) reached 183+/-3 mm Hg while with nNOS inhibition diameter increased only 13+/-10% (p<0.05) even when MAP reached 191+/-4 mm Hg (p>0.05). The nNOS inhibitor significantly attenuated vasodilatation induced by NMDA but not ACh delivered into the window. Thus, local nNOS inhibition attenuates breakthrough from autoregulation during hypertension as does complete interruption of the parasympathetic innervation of cerebral vessels. These findings further support the hypothesis that NO released from parasympathetic fibers contributes to cerebral vasodilatation during acute hypertension.
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Affiliation(s)
- William T Talman
- Laboratory of Neurobiology, Department of Neurology, VAHCS, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
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79
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Gardner CJ, Lee K. Hyperperfusion syndromes: insight into the pathophysiology and treatment of hypertensive encephalopathy. CNS Spectr 2007; 12:35-42. [PMID: 17192762 DOI: 10.1017/s1092852900020502] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Hypertensive encephalopathy is one of the manifestations of a hypertensive crisis. It is not the absolute value of the blood pressure that causes the encephalopathy, rather the presence of an abrupt rise in pressure. In terms of clinical and radiographic findings, there are many similarities among a group of entities, including hypertensive encephalopathy, eclampsia, and immunosuppressant neurotoxicity. Hyperperfusion syndromes may represent these clinical disease states that may share the same pathophysiology. Magnetic resonance imaging fluid attenuated inversion recovery sequences have recognized the prominent cortical involvement of the disease that had been previously missed on computed tomography. Studies have found cortical involvement in 94% of their patients, particularly in mild cases. Animal models demonstrate endothelial damage and enhanced pinocytosis in the cortex as reasons why edema may begin in that region of the brain. Patients diagnosed with hypertensive encephalopathy should be diagnosed and treated promptly in order to avoid further neurological complications. The mean arterial pressure should be lowered by 20% to 25% within the first hour of patient presentation, followed by further gradual reduction in blood pressure over the following 24 hours. Hypertensive emergency in acute ischemic stroke should be managed with more caution. According to the 2003 American Stroke Association treatment guidelines, for patients with ischemic stroke not eligible for thrombolytic therapy, target blood pressures are a diastolic blood pressure <120 mmHg and systolic blood pressure <220 mmHg. The systolic pressure must be <185 mmHg and diastolic pressure <110 mmHg at all times if eligible for thrombolytic therapy.
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80
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Geddes JF, Talbert DG. Paroxysmal coughing, subdural and retinal bleeding: a computer modelling approach. Neuropathol Appl Neurobiol 2006; 32:625-34. [PMID: 17083477 DOI: 10.1111/j.1365-2990.2006.00771.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Unexplained subdural and retinal haemorrhages in an infant are commonly attributed to 'shaking', the mechanism of which is believed to be traumatic venous rupture. However, the haemorrhagic retinopathy reported as a result of Valsalva manoeuvres and the subdural bleeding that is a rare complication of pertussis together demonstrate that if a sustained rise in intrathoracic pressure is transmitted to cerebral and retinal vessels, it may result in bleeding, similar to that reported in inflicted injury. Such haemorrhages would be expected to occur whenever severe paroxysmal coughing were induced, whatever the cause. This study used a computer modelling approach to investigate feeding accidents as the trigger for bleeding. A dynamic circulatory model of a 3-month-old infant was induced to 'cough', and the response to changes in physiological variables monitored. It showed that coughing causes intracranial pressures to build up exponentially to approach a maximum, proportional to the amount of pressure the musculature of the thorax can produce, as venous return is impeded. They do not have time to become dangerous during individual coughs, as blood quickly returns after the cough is over, reestablishing normal pressures. Paroxysmal coughing, however, does not allow blood to return between coughs, with the result that very high luminal pressures may be generated, sufficient to damage veins. A history of coughing, vomiting or choking is not uncommon in otherwise normal infants with retinal and subdural bleeding. Our findings suggest that paroxysmal coughing could account for such bleeding in some cases.
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81
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Ferrington L, Kirilly E, McBean DE, Olverman HJ, Bagdy G, Kelly PAT. Persistent cerebrovascular effects of MDMA and acute responses to the drug. Eur J Neurosci 2006; 24:509-19. [PMID: 16836637 DOI: 10.1111/j.1460-9568.2006.04923.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Acutely, 3,4,-methylenedioxymethamphetamine (MDMA) induces cerebrovascular dysfunction [Quate et al., (2004)Psychopharmacol., 173, 287-295]. In the longer term the same single dose results in depletion of 5-hydroxytrptamine (5-HT) nerve terminals. In this study we examined the cerebrovascular consequences of this persistent neurodegeneration, and the acute effects of subsequent MDMA exposure, upon the relationship that normally exists between local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCMRglu). Dark agouti (DA) rats were pre-treated with 15 mg/kg i.p. MDMA or saline. Three weeks later, rats from each pre-treatment group were treated with an acute dose of MDMA (15 mg/kg i.p.) or saline. Quantitative autoradiographic imaging was used to measure LCBF or LCMRglu with [(14)C]-iodoantipyrine and [(14)C]-2-deoxyglucose, respectively. Serotonergic terminal depletion was assessed using radioligand binding with [(3)H]-paroxetine and immunohistochemistry. Three weeks after MDMA pre-treatment there were significant reductions in densities of 5-HT transporter (SERT)-positive fibres (-46%) and [(3)H]-paroxetine binding (-47%). In animals pre-treated with MDMA there were widespread significant decreases in LCMRglu, but no change in LCBF indicating a persistent loss of cerebrovascular constrictor tone. In both pre-treatment groups, acute MDMA produced significant increases in LCMRglu, while LCBF was significantly decreased. In 50% of MDMA-pre-treated rats, random areas of focal hyperaemia indicated a loss of autoregulatory capacity in response to MDMA-induced hypertension. These results suggest that cerebrovascular regulatory dysfunction resulting from acute exposure to MDMA is not diminished by previous exposure, despite a significant depletion in 5-HT terminals. However, there may be a sub-population, or individual circumstances, in which this dysfunction develops into a condition that might predispose to stroke.
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Affiliation(s)
- Linda Ferrington
- Division of Neuroscience, University of Edinburgh, 1 George Square, Edinburgh EH8 9JZ, UK.
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82
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Wang R, Foniok T, Wamsteeker JI, Qiao M, Tomanek B, Vivanco RA, Tuor UI. Transient blood pressure changes affect the functional magnetic resonance imaging detection of cerebral activation. Neuroimage 2006; 31:1-11. [PMID: 16460967 DOI: 10.1016/j.neuroimage.2005.12.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 11/08/2005] [Accepted: 12/07/2005] [Indexed: 11/26/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) provides an indirect measure of cerebral activation that could be altered by factors directly affecting cerebral blood flow independent of changes in neuronal activation. Presently, we investigate how changes in blood pressure (BP) affect the activation detected with fMRI. fMRI scans were acquired in 33 rats under control conditions and following transient BP increases (norepinephrine, IV) or decreases (arfonad, IV) with and without electrical stimulation of the forepaw. Voxels correlating to either the stimulation or the change in BP time courses were identified. During transient hypertension, irrespective of forepaw stimulation, BP increases (i.e., >10 mm Hg) produced a transient increase in the blood oxygen level-dependent (BOLD) intensity resulting in a significant numbers of voxels correlating to the BP time courses (P < 0.05), and the number of these voxels increased as BP increased, becoming substantial at BP > 30 mm Hg. The activation patterns with BP increases and stimulation overlapped spatially resulting in an enhanced cerebral activation to simultaneous forepaw stimulation (P < 0.05). BP decreases (>10 mm Hg) produced corresponding decreases in BOLD intensity, causing significant numbers of voxels correlating to the BP decreases (P < 0.005), and these numbers increased as BP decreased (P < 0.001). The BP decreases and stimulation time courses and responses were distinct, and hypotension did not affect the detection of the activation response to forepaw stimulation. The results indicate that substantial hypertension accompanying a stimulation paradigm produces a BOLD response that enhances the cerebral activation detected, whereas hypotension does not affect the detection of neuronal activation but does produce responses that could be interpreted as a 'deactivation'.
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Affiliation(s)
- Rong Wang
- Institute for Biodiagnostics (West), National Research Council of Canada, B153, 3330 Hospital DR N.W., Calgary, Alberta, Canada T2N4N1
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83
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Lagopoulos J, Malhi GS, Ivanovski B, Cahill CM, Lang EW, Mudaliar Y, Dorsch N, Yam A, Griffith J, Mulvey J. Cerebrovascular autoregulation as a neuroimaging tool. Acta Neuropsychiatr 2006; 18:100-4. [PMID: 26989798 DOI: 10.1111/j.1601-5215.2006.00133.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Functional transcranial Doppler (fTCD) sonography provides a high temporal resolution measure of blood flow and has over the years proved to be a valuable tool in the clinical evaluation of patients with cerebrovascular disorders. More recently, due to advances in physics and computing, it has become possible to derive indices of cerebrovascular autoregulation (CA) as well as cerebrovascular pressure reactivity (CR), using non-invasive techniques. These indices provide a dynamic representation of the brain's regulatory blood flow mechanisms not only in pathological states but also in health. However, whilst the temporal resolution of these regulatory indices is very good, spatially, the localization of brain regions remains very poor, thus limiting its brain mapping capacity. Functional MRI, on the contrary, is a brain-imaging technique that operates on similar blood flow principles; however, unlike fTCD, it provides high spatial resolution. Because both fTCD and fMRI determine blood flow-dependant imaging parameters, the coupling of fTCD with fMRI may provide greater insight into brain function by virtue of the combined enhanced temporal and spatial resolution that each technique affords. This review summarizes the fTCD technique with particular emphasis on the CA and CR indices and their relationship in traumatic brain injury as well as in health.
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Affiliation(s)
- Jim Lagopoulos
- 1School of Psychiatry, The University of New South Wales, Australia
| | - Gin S Malhi
- 1School of Psychiatry, The University of New South Wales, Australia
| | | | | | - Erhard W Lang
- 5Department of Neurosurgery, Westmead Hospital, Westmead, Australia
| | - Yugan Mudaliar
- 6Intensive Care Unit, Westmead Hospital, Westmead, Australia
| | - Nick Dorsch
- 5Department of Neurosurgery, Westmead Hospital, Westmead, Australia
| | - Alan Yam
- 5Department of Neurosurgery, Westmead Hospital, Westmead, Australia
| | - Jane Griffith
- 5Department of Neurosurgery, Westmead Hospital, Westmead, Australia
| | - Jamin Mulvey
- 6Intensive Care Unit, Westmead Hospital, Westmead, Australia
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84
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Goto H, Mizuno R, Ono N, Sakaguchi M, Ohhashi T. Comparison of biomechanical and histological properties in dog carotid arteries injured by neointima or intimal thickening. ACTA ACUST UNITED AC 2005; 55:355-64. [PMID: 16368015 DOI: 10.2170/jjphysiol.r2136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Accepted: 12/20/2005] [Indexed: 11/05/2022]
Abstract
A general formula (Oka and Azuma's equation) has been rigorously derived for the circumferential wall tension in a hollow cylindrical tube in equilibrium. To evaluate the validity and usefulness of Oka and Azuma's equation, T = P(1) x r(1) - P(2) x r(2) (T, circumferential wall tension; P(1) and P(2), internal and external pressures of the tube; r(1) and r(2), the corresponding internal and external radii), we experimentally investigated changes in circumferential wall tension of noninjured (control) and injured dog common carotid arteries by using a newly developed apparatus with a photo- and X-ray-sensitive image sensor. We also studied histological features of the control and injured arteries with special reference to the relation of biomechanical properties. Two types of animal models with injured arteries--balloon-induced neointima or external collar-induced intimal thickening--were adopted in the present study. In the control arteries, the circumferential wall tension was experimentally confirmed to change from negative to positive by an increase in intraluminal pressure ranging from 50 to 180 mmHg. The critical intraluminal pressure that produced 0 dyne/cm of the circumferential wall tension was around 135 mmHg. The activation of arterial smooth muscles caused a significant increase in the critical pressure in the control arteries. In the arteries injured by neointima, the critical intraluminal pressure was significantly lower than that in the control. The activation of smooth muscles also significantly increased the critical pressure in the injured arteries. Histological examination demonstrated the existence of a circumferential neointimal formation along with a shortening of the internal diameter. In other arteries injured by intimal thickening, the circumferential wall tension was always negative at intraluminal pressure ranging from 50 to 180 mmHg. Newly developed structures consisted of elastic and collagen fibers, smooth muscles, and extracellular matrix in the intima and media of the injured arteries. These experimental findings suggest that the circumferential wall tension of dog common carotid arteries has been confirmed experimentally to become negative. We have also concluded that circumferential wall tension calculated with Oka-Azuma's equation may be one of the best parameters for evaluating changes in the biomechanical and histological properties of pathologically injured arteries.
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Affiliation(s)
- Hirohisa Goto
- Department of Physiology, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan
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85
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Ono Y, Manabe Y, Hamakawa Y, Murakami T, Omori N, Hayashi Y, Abe K. Localized lesions on MRI in a case of hypertensive brainstem encephalopathy. Intern Med 2005; 44:1002-5. [PMID: 16258222 DOI: 10.2169/internalmedicine.44.1002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report a case of hypertensive brainstem encephalopathy (HBE) with unusual magnetic resonance imaging (MRI) findings. A 67-year-old woman presented with high blood pressure and stupor as the only symptoms. MRI revealed lesions localized in the area from the upper medulla oblongata to the lower pons with high fluid-attenuated inversion recovery (FLAIR) and T2-weighted signal intensity, but these were not seen in the whole brainstem and there were no accompanying occipital lobe changes. To our knowledge, no similar case has been reported. The lesions and symptoms dramatically improved after normalization of blood pressure. Severe hypertension that exceeded the range of autoregulation may have resulted in segmental vasodilatation and the increased vascular permeability may have lead to vasogenic edema in the localized areas of the brainstem.
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Affiliation(s)
- Yoichi Ono
- Department of Neurology, National Hospital Organization Okayama Medical Center, Japan
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86
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Feske SK. HYPERPERFUSION SYNDROMES. Continuum (Minneap Minn) 2005. [DOI: 10.1212/01.con.0000293722.63368.90] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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87
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Amberg GC, Rossow CF, Navedo MF, Santana LF. NFATc3 Regulates Kv2.1 Expression in Arterial Smooth Muscle. J Biol Chem 2004; 279:47326-34. [PMID: 15322114 DOI: 10.1074/jbc.m408789200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated K+ (Kv) channels control the excitability of arterial smooth muscle. However, the molecular mechanisms regulating Kv channel function in smooth muscle remain unclear. We examined the hypothesis that the vasoactive peptide angiotensin II (Ang II) regulates arterial smooth muscle Kv channel function via calcineurin-dependent activation of the transcription factor NFAT. We found that sustained administration of Ang II decreased Kv currents (IKv) by reducing the expression of Kv2.1 K+ channel subunits. This effect of Ang II was independent of pressure but required Ca2+ influx through L-type Ca2+ channels. Consistent with our hypothesis, we found that calcineurin and NFATc3 are obligatory components of the signaling cascade mediating reduced IKv by Ang II. We conclude that sustained Ang II exposure increases smooth muscle Ca2+, which leads to activation of calcineurin and NFATc3, culminating in decreased Kv2.1 expression and reduced IKv function. These results support the novel concept that NFATc3 controls the excitability of arterial smooth muscle by regulating Kv2.1 expression.
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MESH Headings
- Adenoviridae/genetics
- Angiotensin II/chemistry
- Animals
- Arteries/metabolism
- Blood Pressure
- Blotting, Western
- Calcium/chemistry
- Calcium/metabolism
- Calcium Channels/chemistry
- DNA-Binding Proteins/chemistry
- DNA-Binding Proteins/physiology
- Electrophysiology
- Green Fluorescent Proteins/metabolism
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Knockout
- Microscopy, Confocal
- Models, Biological
- Muscle Cells/metabolism
- Muscle, Smooth/cytology
- Muscle, Smooth/metabolism
- Myocytes, Smooth Muscle/metabolism
- NFATC Transcription Factors
- Peptides/chemistry
- Potassium/chemistry
- Potassium Channels, Voltage-Gated/biosynthesis
- Potassium Channels, Voltage-Gated/chemistry
- Pressure
- Rats
- Rats, Sprague-Dawley
- Shab Potassium Channels
- Signal Transduction
- Transcription Factors/chemistry
- Transcription Factors/physiology
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Affiliation(s)
- Gregory C Amberg
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA
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88
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Finocchi V, Bozzao A, Bonamini M, Ferrante M, Romano A, Colonnese C, Fantozzi LM. Magnetic resonance imaging in Posterior Reversible Encephalopathy Syndrome: report of three cases and review of literature. Arch Gynecol Obstet 2004; 271:79-85. [PMID: 15480723 DOI: 10.1007/s00404-004-0622-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Accepted: 02/05/2004] [Indexed: 10/26/2022]
Abstract
INTRODUCTION Eclampsia is one of the main causes of Posterior Reversible Encephalopathy Syndrome (PRES) a recent clinico-neuroradiological entity represented by characteristic MR findings of a symmetric bilateral subcortical/cortical hyperintensity in T2-weighted images, more often in parieto-occipital lobes, accompanied by clinical neurological alterations. Neuroradiological and clinical alterations are commonly completely reversible although ischemic evolution has been described. The pathophysiology is still a matter of debate. Specific magnetic resonance (MR) techniques, such as FLAIR (fluid attenuated inversion recovery) and DWI (diffusion weighted images) sequences, have improved the ability to detect subcortical/cortical lesions and helped to clarify the underlying pathophysiological mechanism of cerebrovascular involvement, which results important for an appropriate therapeutic decision. CASE REPORT AND DISCUSSION We report the MR imaging findings of three patients with eclampsia and PRES as well as a careful review of literature.
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Affiliation(s)
- Vanina Finocchi
- Department of Neuroradiology, University of Rome La Sapienza, Sant'Andrea Hospital, Via di Grottarossa 1035, 00189 Rome, Italy.
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89
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Aksoy DY, Arici M, Kiykim AA, Durusu M, Sahin G, Baydar DE, Altun B, Erdem Y, Yasavul U, Turgan C, Caglar S. Posterior Leukoencephalopathy and Nephrotic Syndrome: Just a Coincidence? Am J Med Sci 2004; 327:156-9. [PMID: 15090755 DOI: 10.1097/00000441-200403000-00008] [Citation(s) in RCA: 9] [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
Posterior leukoencephalopathy syndrome (PLES) is an acute neurological disorder. The most plausible hypothesis for the pathophysiology of PLES is the loss of autoregulation and consequent vasogenic edema. PLES is mostly attributed to severe or sudden elevations of arterial blood pressure. A number of reports, however, describe patients with PLES without severe hypertension. This report presents two patients with nephrotic syndrome who developed PLES without customarily severe hypertension. Proteinuria, low levels of serum albumin, or generalized increase in capillary permeability in nephrotic syndrome can initiate PLES with moderately high arterial blood pressure levels. PLES is increasingly recognized by neurologists, but it should also be remembered by internists when confronted with patients with nephrotic syndrome who present with neurological symptoms, whether or not they have severe hypertension.
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Affiliation(s)
- Duygu Yazgan Aksoy
- Departments of Internal Medicine, Hacettepe University Faculty of Medicine, Ankara, Turkey.
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90
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Lu K, Clark JW, Ghorbel FH, Robertson CS, Ware DL, Zwischenberger JB, Bidani A. Cerebral autoregulation and gas exchange studied using a human cardiopulmonary model. Am J Physiol Heart Circ Physiol 2004; 286:H584-601. [PMID: 12946929 DOI: 10.1152/ajpheart.00594.2003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The goal of this work is to study the cerebral autoregulation, brain gas exchange, and their interaction by means of a mathematical model. We have previously developed a model of the human cardiopulmonary (CP) system, which included the whole body circulatory system, lung and peripheral tissue gas exchange, and the central nervous system control of arterial pressure and ventilation. In this study, we added a more detailed description of cerebral circulation, cerebrospinal fluid (CSF) dynamics, brain gas exchange, and cerebral blood flow (CBF) autoregulation. Two CBF regulatory mechanisms are included: autoregulation and CO(2) reactivity. Central chemoreceptor control of ventilation is also included. We first established nominal operating conditions for the cerebral model in an open-loop configuration using data generated by the CP model as inputs. The cerebral model was then integrated into the larger CP model to form a new integrated CP model, which was subsequently used to study cerebral hemodynamic and gas exchange responses to test protocols commonly used in the assessment of CBF autoregulation (e.g., carotid artery compression and the thigh-cuff deflation test). The model can closely mimic the experimental findings and provide biophysically based insights into the dynamics of cerebral autoregulation and brain tissue gas exchange as well as the mechanisms of their interaction during test protocols, which are aimed at assessing the degree of autoregulation. With further refinement, our CP model may be used on measured data associated with the clinical evaluation of the cerebral autoregulation and brain oxygenation in patients.
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Affiliation(s)
- K Lu
- Dynamical Systems Group, Rice University, Houston, TX 77005, USA
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91
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Kazama K, Wang G, Frys K, Anrather J, Iadecola C. Angiotensin II attenuates functional hyperemia in the mouse somatosensory cortex. Am J Physiol Heart Circ Physiol 2003; 285:H1890-9. [PMID: 12907423 DOI: 10.1152/ajpheart.00464.2003] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether angiotensin II (ANG II), a peptide that plays a central role in the genesis of hypertension, alters the coupling between synaptic activity and cerebral blood flow (CBF), a critical homeostatic mechanism that assures adequate cerebral perfusion to active brain regions. The somatosensory cortex was activated by stroking the facial whiskers in anesthetized C57BL/6J mice while local CBF was recorded by laser-Doppler flowmetry. Intravenous ANG II infusion (0.25 mug.kg-1.min-1) increased mean arterial pressure (MAP) from 82 +/- 2 to 102 +/- 3 mmHg (P < 0.05) without affecting resting CBF (P > 0.05). ANG II attenuated the CBF increase produced by whisker stimulation by 65% (P < 0.05) but did not affect the response to hypercapnia or to neocortical application of the nitric oxide donor S-nitroso-N-acetyl penicillamine (P > 0.05). The effect of ANG II on functional hyperemia persisted if the elevation in MAP was offset by controlled hemorrhage or prevented by topical application of the peptide to the activated cortex. ANG II did not reduce the amplitude of the P1 wave of the field potentials evoked by whisker stimulation (P > 0.05). Infusion of phenylephrine increased MAP (P > 0.05 from ANG II) but did not alter the functional hyperemic response (P > 0.05). The data suggest that ANG II alters the coupling between CBF and neural activity. The mechanisms of the effect are not related to the elevation in MAP and/or to inhibition of the synaptic activity evoked by whisker stimulation. The imbalance between CBF and neural activity induced by ANG II may alter the homeostasis of the neuronal microenvironment and contribute to brain dysfunction during ANG II-induced hypertension.
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Affiliation(s)
- Ken Kazama
- Division of Neurobiology, Department of Neurology and Neuroscience, Weill Medical College of Cornell University, 411 E. 69th Street, Rm. KB410, New York, NY 10021, USA
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92
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Belfort MA, Tooke-Miller C, Allen JC, Dizon-Townson D, Varner MA. Labetalol decreases cerebral perfusion pressure without negatively affecting cerebral blood flow in hypertensive gravidas. Hypertens Pregnancy 2003; 21:185-97. [PMID: 12517326 DOI: 10.1081/prg-120015845] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVE To research the cerebral hemodynamic effects of labetalol in pregnant women with hypertension. DESIGN Prospective observational study. SETTING Tertiary Care Medical Center. POPULATION Pregnant patients with hypertension. METHODS Transcranial Doppler (TCD) ultrasound was used to measure the blood velocity in the middle cerebral arteries (MCA) of eight pregnant patients with hypertension, before and after the administration of a 200 mg oral dose of labetalol. Five patients had severe preeclampsia, and three had chronic hypertension with superimposed preeclampsia. MCA blood velocity and systemic blood pressure were measured simultaneously at the baseline, and at 60 and 180 min after labetalol. Selected cerebral hemodynamic parameters were compared with normative curves. Values outside of the 5th and 95th percentiles were regarded as abnormal. MAIN OUTCOME MEASURES Cerebral perfusion pressure (CPP), resistance area product (RAP), and cerebral flow index (CFI). RESULTS Patient age, gestational age, and parity were similar to those of the normal women from whom the normative data were obtained. Women with hypertension had higher baseline CPP, MAP, and RAP than normal pregnant women, but their CFI was within the normal range. Labetalol reduced the CPP, as well as the systolic, diastolic, and mean BP significantly at 60 and 180 min without significantly affecting the heart rate, MCA velocities, RAP, or CFI. CONCLUSIONS Labetalol effectively reduces CPP, without affecting cerebral perfusion, primarily by a decrease in systemic blood pressure. This makes it an ideal agent for blood pressure control in severely hypertensive pregnant women.
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Affiliation(s)
- Michael A Belfort
- Division of Maternal-Fetal Medicine, Department of Obstetrics, University of Utah School of Medicine, Salt Lake City, UT, USA.
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93
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Payen JF, Fauvage B, Falcon D, Lavagne P. [Brain oedema following blood-brain barrier disruption: mechanisms and diagnosis]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 2003; 22:220-5. [PMID: 12747990 DOI: 10.1016/s0750-7658(03)00010-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Brain oedema following blood-brain barrier (BBB) disruption, or vasogenic oedema, is present in most cases of brain oedema. According to the Starling's law, water, ions and plasma proteins cross the BBB toward the interstitium if the driving forces for transmural bulk flow are excessive (mechanical origin) and/or if the BBB permeability is enhanced (chemical origin). Both mechanisms coexist in most cases. Excessive elevation of the gradient of hydrostatic pressure with lost of cerebral autoregulation has been proved in ischaemia/reperfusion and trauma, and suggested in acute mountain sickness and eclampsia. The BBB permeability can be enhanced by immediate (chemical mediators) or delayed (cellular infiltration) inflammatory response, or by alteration of the membrane integrity. This later can be transient (hyperosmolar BBB disruption), or permanent by activation of matrix metalloproteinase or by neovascularization with BBB breakdown. The reference method for the diagnosis of vasogenic oedema is the MRI diffusion-weighted imaging.
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Affiliation(s)
- J F Payen
- Département d'anesthésie-réanimation, hôpital Michallon, BP 217, 38043 Grenoble, France.
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94
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Myburgh JA, Upton RN, Grant C, Martinez A. The cerebrovascular effects of adrenaline, noradrenaline and dopamine infusions under propofol and isoflurane anaesthesia in sheep. Anaesth Intensive Care 2002; 30:725-33. [PMID: 12500509 DOI: 10.1177/0310057x0203000602] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Infusions of catecholamines are frequently administered to patients receiving propofol or isoflurane anaesthesia. Interactions between these drugs may affect regional circulations, such as the brain. The aim of this animal (sheep) study was to determine the effects of ramped infusions of adrenaline, noradrenaline (10, 20, 40 micrograms/min) and dopamine (10, 20, 40 micrograms/kg/min) on cerebral blood flow (CBF), intracranial pressure (ICP), cerebrovascular resistance (CVR) and cerebral metabolic rate for oxygen (CMRO2). These measurements were made under awake physiological conditions, and during continuous propofol (15 mg/min) or 2% isoflurane anaesthesia. All three catecholamines significantly and equivalently increased mean arterial pressure from baseline in a dose-dependent manner in the three cohorts (P < 0.001). In the awake cohort (n = 8), dopamine (P < 0.01) significantly increased CBF from baseline whilst adrenaline and noradrenaline did not (P > 0.05). Under propofol (n = 6) and isoflurane (n = 6), all three catecholamines significantly increased CBF (P < 0.001). Dopamine caused the greatest increase in CBF, and was associated with significant increases in ICP (awake: P < 0.001; propofol P < 0.05; isoflurane P < 0.001) and CVR (isoflurane P < 0.05). No significant changes in CMRO2 were demonstrated. Under propofol and isoflurane anaesthesia, the cerebrovascular effects of catecholamines were significantly different from the awake, physiological state, with dopamine demonstrating the most pronounced effects, particularly under propofol. Dopamine-induced hyperaemia was associated with other cerebrovascular changes. In the presence of an equivalent effect on mean arterial pressure, the exaggerated cerebrovascular effects under anaesthesia appear to be centrally mediated, possibly induced by propofol- or isoflurane-dependent changes in blood-brain barrier permeability, thereby causing a direct influence on the cerebral vasculature.
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Affiliation(s)
- J A Myburgh
- Department of Anaesthesia and Intensive Care, University of Adelaide, Adelaide, South Australia
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95
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Fernandes FJF, Machado Júnior MADC, Pedreira AV, Silva CIS, Tavares HC, Barbosa VA. Sindrome de encefalopatia posterior reversível: relato de caso. ARQUIVOS DE NEURO-PSIQUIATRIA 2002. [DOI: 10.1590/s0004-282x2002000400027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A encefalopatia posterior reversível é uma síndrome aguda / subaguda geralmente causada pela encefalopatia hipertensiva, eclâmpsia, neurotoxicidade a ciclosporina-A, encefalopatia urêmica e púrpura trombocitopênica trombótica.. A maioria dos pacientes apresenta elevação acentuada dos níveis tensionais outros, níveis moderados ou normais. Os sintomas são progressivos e compreendem cefaléia, diminuição do nível de consciência, crises epilépticas e distúrbios visuais. A sintomatologia regride completamente se corrigidas em tempo as causas determinantes, caso contrário, podem instalar-se danos irreversíveis como a cegueira cortical e morte. A tomografia computadorizada (TC) e, sobretudo, a ressonância magnética (RM) contribuem para o diagnóstico. Tais métodos evidenciam edema da substância branca e cinzenta, principalmente das regiões parieto-occipitais. Os achados podem apresentar dificuldade no diagnóstico, hoje superado em parte, com a técnica de difusão pela RM, capaz de diferenciar edema citotóxico de vasogênico. Apresentamos um caso de encefalopatia posterior reversível decorrente de encefalopatia hipertensiva estudada com TC e RM.
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96
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Meyer B, Stoffel M, Stuer C, Schaller C, Muhlbauer B, Schramm J. Norepinephrine in the Rat Cortex before and after Occlusion of Chronic Arteriovenous Fistulae: A Microdialysis Study in an Animal Model of Cerebral Arteriovenous Malformations. Neurosurgery 2002. [DOI: 10.1227/00006123-200209000-00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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97
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Norepinephrine in the Rat Cortex before and after Occlusion of Chronic Arteriovenous Fistulae: A Microdialysis Study in an Animal Model of Cerebral Arteriovenous Malformations. Neurosurgery 2002. [DOI: 10.1097/00006123-200209000-00028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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98
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Abstract
Lacunar infarcts and "hypertensive" primary intracerebral hemorrhages, collectively often referred to as hypertensive small vessel strokes, constitute about one third of all strokes. However, despite their public health importance, their etiopathogenesis remains ill-understood. Like all strokes, they are a heterogeneous entity, but the autopsy pathology evidence suggests that the majority are caused by a limited number of cerebral small vessel lesions. Small vessel atherosclerosis is causally implicated in a proportion of lacunar infarcts, although modern concepts of atherosclerotic plaque biology and natural history have yet to be applied to small cerebral vessels. A lesion characterized in its acute form by fibrinoid necrosis appears to be important in causing both lacunar infarcts and primary intracerebral bleeds. Advances in molecular genetics may prove instrumental in understanding the cause of this lesion and therefore in designing its targeted prevention.
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Affiliation(s)
- G Alistair Lammie
- Department of Pathology, University of Wales College of Medicine, Cardiff, United Kingdom.
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99
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Steiner LA, Czosnyka M, Piechnik SK, Smielewski P, Chatfield D, Menon DK, Pickard JD. Continuous monitoring of cerebrovascular pressure reactivity allows determination of optimal cerebral perfusion pressure in patients with traumatic brain injury. Crit Care Med 2002; 30:733-8. [PMID: 11940737 DOI: 10.1097/00003246-200204000-00002] [Citation(s) in RCA: 519] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
OBJECTIVES To define optimal cerebral perfusion pressure (CPPOPT) in individual head-injured patients using continuous monitoring of cerebrovascular pressure reactivity. To test the hypothesis that patients with poor outcome were managed at a cerebral perfusion pressure (CPP) differing more from their CPPOPT than were patients with good outcome. DESIGN Retrospective analysis of prospectively collected data. SETTING Neurosciences critical care unit of a university hospital. PATIENTS A total of 114 head-injured patients admitted between January 1997 and August 2000 with continuous monitoring of mean arterial blood pressure (MAP) and intracranial pressure (ICP). MEASUREMENTS AND MAIN RESULTS MAP, ICP, and CPP were continuously recorded and a pressure reactivity index (PRx) was calculated online. PRx is the moving correlation coefficient recorded over 4-min periods between averaged values (6-sec periods) of MAP and ICP representing cerebrovascular pressure reactivity. When cerebrovascular reactivity is intact, PRx has negative or zero values, otherwise PRx is positive. Outcome was assessed at 6 months using the Glasgow Outcome Scale. A total of 13,633 hrs of data were recorded. CPPOPT was defined as the CPP where PRx reaches its minimum value when plotted against CPP. Identification of CPPOPT was possible in 68 patients (60%). In 22 patients (27%), CPPOPT was not found because it presumably lay outside the studied range of CPP. Patients' outcome correlated with the difference between CPP and CPPOPT for patients who were managed on average below CPPOPT (r =.53, p <.001) and for patients whose mean CPP was above CPPOPT (r = -.40, p <.05). CONCLUSIONS CPPOPT could be identified in a majority of patients. Patients with a mean CPP close to CPPOPT were more likely to have a favorable outcome than those whose mean CPP was more different from CPPOPT. We propose use of the criterion of minimal achievable PRx to guide future trials of CPP oriented treatment in head injured patients.
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Affiliation(s)
- Luzius A Steiner
- Academic Neurosurgery, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
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100
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Mesiwala AH, Farrell L, Wenzel HJ, Silbergeld DL, Crum LA, Winn HR, Mourad PD. High-intensity focused ultrasound selectively disrupts the blood-brain barrier in vivo. ULTRASOUND IN MEDICINE & BIOLOGY 2002; 28:389-400. [PMID: 11978420 DOI: 10.1016/s0301-5629(01)00521-x] [Citation(s) in RCA: 186] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
High-intensity focused ultrasound (HIFU) has been shown to generate lesions that destroy brain tissue while disrupting the blood-brain barrier (BBB) in the periphery of the lesion. BBB opening, however, has not been shown without damage, and the mechanisms by which HIFU induces BBB disruption remain unknown. We show that HIFU is capable of reversible, nondestructive, BBB disruption in a targeted region-of-interest (ROI) (29 of 55 applications; 26 of 55 applications showed no effect); this opening reverses after 72 h. Light microscopy demonstrates that HIFU either entirely preserves brain architecture while opening the BBB (18 of 29 applications), or generates tissue damage in a small volume within the region of BBB opening (11 of 29 applications). Electron microscopy supports these observations and suggests that HIFU disrupts the BBB by opening capillary endothelial cell tight junctions, an isolated ultrastructural effect that is different from the mechanisms through which other (untargeted) modalities, such as hyperosmotic solutions, hyperthermia and percussive injury disrupt the BBB.
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Affiliation(s)
- Ali H Mesiwala
- Department of Neurological Surgery, University of Washington, Seattle, WA 98105, USA
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