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Differential influence of vitamin C on the peripheral and cerebral circulation after diving and exposure to hyperoxia.
Barak, OF, Caljkusic, K, Hoiland, RL, Ainslie, PN, Thom, SR, Yang, M, Jovanov, P, Dujic, Z
American journal of physiology. Regulatory, integrative and comparative physiology. 2018;(4):R759-R767
Abstract
We examined if the diving-induced vascular changes in the peripheral and cerebral circulation could be prevented by oral antioxidant supplementation. Fourteen divers performed a single scuba dive to eighteen meter sea water for 47 min. Twelve of the divers participated in a follow-up study involving breathing 60% of oxygen at ambient pressure for 47 min. Before both studies, participants ingested vitamin C (2 g/day) or a placebo capsule for 6 days. After a 2-wk washout, the study was repeated with the different condition. Endothelium-dependent vasodilator function of the brachial artery was assessed pre- and postintervention using the flow-mediated dilation (FMD) technique. Transcranial Doppler ultrasound was used to measure intracranial blood velocities pre- and 90 min postintervention. FMD was reduced by ∼32.8% and ∼21.2% postdive in the placebo and vitamin C trial and posthyperoxic condition in the placebo trial by ∼28.2% ( P < 0.05). This reduction in FMD was attenuated by ∼10% following vitamin C supplementation in the hyperoxic study ( P > 0.05). Elevations in intracranial blood velocities 30 min after surfacing from diving were reduced in the vitamin C study compared with the placebo trial ( P < 0.05). O2 breathing had no postintervention effects on intracranial velocities ( P > 0.05). Prophylactic ingestion of vitamin C effectively abrogated peripheral vascular dysfunction following exposure to 60% O2 but did not abolish the postdive decrease in FMD. Transient elevations of intracranial velocities postdive were reduced by vitamin C. These findings highlight the differential influence of vitamin C on peripheral and cerebral circulations following scuba diving, which are only partly mediated via hyperoxia.
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Cerebrovascular and ventilatory responses to acute isocapnic hypoxia in healthy aging and lung disease: effect of vitamin C.
Hartmann, SE, Waltz, X, Kissel, CK, Szabo, L, Walker, BL, Leigh, R, Anderson, TJ, Poulin, MJ
Journal of applied physiology (Bethesda, Md. : 1985). 2015;(4):363-73
Abstract
Acute hypoxia increases cerebral blood flow (CBF) and ventilation (V̇e). It is unknown if these responses are impacted with normal aging, or in patients with enhanced oxidative stress, such as (COPD). The purpose of the study was to 1) investigate the effects of aging and COPD on the cerebrovascular and ventilatory responses to acute hypoxia, and 2) to assess the effect of vitamin C on these responses during hypoxia. In 12 Younger, 14 Older, and 12 COPD, we measured peak cerebral blood flow velocity (V̄p; index of CBF), and V̇e during two 5-min periods of acute isocapnic hypoxia, under conditions of 1) saline-sham; and 2) intravenous vitamin C. Antioxidants [vitamin C, superoxide dismutase (SOD), glutathione peroxidase, and catalase], oxidative stress [malondialdehyde (MDA) and advanced protein oxidation product], and nitric oxide metabolism end products (NOx) were measured in plasma. Following the administration of vitamin C, vitamin C, SOD, catalase, and MDA increased, while NOx decreased. V̄p and V̇e sensitivity to hypoxia was reduced in Older by ∼60% (P < 0.02). COPD patients exhibited similar V̄p and V̇e responses to Older (P > 0.05). Vitamin C did not have an effect on the hypoxic V̇e response but selectively decreased the V̄p sensitivity in Younger only. These findings suggest a reduced integrative reflex (i.e., cerebrovascular and ventilatory) during acute hypoxemia in healthy older adults. Vitamin C does not appear to have a large influence on the cerebrovascular or ventilatory responses during acute hypoxia.
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Cerebral oximetry assessed by near-infrared spectrometry during preeclampsia: an observational study: impact of magnesium sulfate administration.
Guerci, P, Vial, F, Feugeas, J, Pop, M, Baka, NE, Bouaziz, H, Losser, MR
Critical care medicine. 2014;(11):2379-86
Abstract
OBJECTIVES To determine the regional cerebral oxygen saturation of hemoglobin (rcSO2) in severe preeclamptic parturients exhibiting neurologic symptoms compared with healthy pregnant women (control) and to describe the effects of MgSO4 infusion on rcSO2 and cerebral and systemic hemodynamic variables. DESIGN Prospective, observational study. SETTING Obstetric critical care unit in a university-affiliated hospital. PATIENTS Twenty severe preeclamptic parturients presenting with neurologic signs before any administration of MgSO4, and 20 control parturients. INTERVENTION Infusion of MgSO4 in severe preeclamptic patients. MEASUREMENTS AND MAIN RESULTS We measured rcSO2 using near-infrared spectroscopy, blood flow velocities of the middle cerebral artery, and cardiac output at baseline, 5 minutes, 1 hour, and 6 hours after the MgSO4 bolus (4 g), followed by continuous MgSO4 infusion (1 g/h). These measurements were also obtained in 20 control parturients at baseline and 6 hours. Baseline rcSO2 was significantly lower in the severe preeclamptic group: 61% (56-69) vs 66% (63-71) (p = 0.037). At inclusion, blood pressures were significantly higher in the severe preeclamptic group compared with the control group, whereas cardiac output and transcranial Doppler readings were similar. Five minutes after the MgSO4 bolus infusion, a median increase of 8.6% (3.2-18.1) in rcSO2 was observed (p = 0.007), reaching values of the control group that were maintained up to 6 hours. Blood pressures and systolic velocities of the middle cerebral artery significantly decreased (p < 0.01) after the MgSO4 bolus, whereas cardiac output did not change. The percentage increase in rcSO2 was negatively correlated to the mean blood pressure (r = 0.60, p < 0.0001). CONCLUSION Cerebral oxygenation impairment can be detected by near-infrared spectroscopy monitoring in severe preeclamptic parturients. These results suggested the presence of disorders in cerebral microcirculation and/or changes in cerebral oxygenation. MgSO4 infusion in patients with severe preeclampsia restored rcSO2 to control levels with no systemic side effects. Further studies are needed to confirm the usefulness of near-infrared spectroscopy monitoring in patients with preeclampsia and to assess the action of other antihypertensive therapies on rcSO2.
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Cerebral blood flow and glucose metabolism in appetite-related brain regions in type 1 diabetic patients after treatment with insulin detemir and NPH insulin: a randomized controlled crossover trial.
van Golen, LW, IJzerman, RG, Huisman, MC, Hensbergen, JF, Hoogma, RP, Drent, ML, Lammertsma, AA, Diamant, M
Diabetes care. 2013;(12):4050-6
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Abstract
OBJECTIVE To test the hypothesis that insulin detemir, which is associated with less weight gain than other basal insulin formulations, exerts its weight-modulating effects by acting on brain regions involved in appetite regulation, as represented by altered cerebral blood flow (CBF) or cerebral glucose metabolism (CMRglu). RESEARCH DESIGN AND METHODS Twenty-eight male type 1 diabetic patients (age 36.9 ± 9.7 years, BMI 24.9 ± 2.7 kg/m(2), A1C 7.5 ± 0.6%) successfully completed a randomized crossover study, consisting of two periods of 12-week treatment with either insulin detemir or NPH insulin, both in combination with prandial insulin aspart. After each treatment period, patients underwent positron emission tomography scans to measure regional CBF and CMRglu. RESULTS After 12 weeks, A1C, daily insulin doses, fasting insulin, and blood glucose levels were similar between treatments. Insulin detemir resulted in body weight loss, whereas NPH insulin induced weight gain (between-treatment difference 1.3 kg; P = 0.02). After treatment with insulin detemir relative to NPH insulin, CBF was higher in brain regions involved in appetite regulation, whereas no significant difference in CMRglu was observed. CONCLUSIONS Treatment with insulin detemir versus NPH insulin resulted in weight loss, paralleled by increased CBF in appetite-related brain regions in the resting state, in men with well-controlled type 1 diabetes. These findings lend support to the hypothesis that a differential effect on the brain may contribute to the consistently observed weight-sparing effect of insulin detemir.
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[Determination of the optimal ROI setting position of the input function for the ⁹⁹mTc-ethyl cysteinate dimmer brain uptake ratio method].
Inoue, S, Kabuto, T, Masunaga, S, Souma, T, Takaki, A, Hosoya, T, Yoshioka, K, Ito, S
Nihon Hoshasen Gijutsu Gakkai zasshi. 2012;(3):269-76
Abstract
Determination of the input function for the (99m)Tc-ethyl cysteinate dimmer brain uptake ratio ((99m)Tc-ECD BUR) method as a non-invasive quantitative measurement of cerebral blood flow measurement is of critical importance in order to improve the accuracy of this method. The input functions were experimentally obtained by setting the regions of interest (ROIs) in the ascending aorta, aortic arch, and descending aorta on the 49 chest RI-angio images. rCBFs by the BUR method with 3 input functions of the 6 cases were compared with those by the (123)I-iodoamphetamine (IMP) continuous arterial blood sampling method in order to determine the best location for the ROI of the input function. The input function of the ascending aorta was higher than those of the aortic arch and the descending aorta. The input functions of the aortic arch and the descending aorta decreased due to the origin of the three branches of the right brachiocephalic artery, left subclavian artery, and left common carotid artery. A good correlation was found in the regional cerebral blood flow (rCBF) values between the (123)I-IMP continuous arterial blood sampling method and the (99m)Tc-ECD BUR method with the input function of the ascending aorta. Therefore, the ascending aorta is the best location for the ROI of the input function for the (99m)Tc-ECD BUR method.
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Benefits of the angiotensin II receptor antagonist olmesartan in controlling hypertension and cerebral hemodynamics after stroke.
Matsumoto, S, Shimodozono, M, Miyata, R, Kawahira, K
Hypertension research : official journal of the Japanese Society of Hypertension. 2009;(11):1015-21
Abstract
The purpose of this study was to assess the relative benefits of angiotensin II receptor blockers (ARBs) and calcium channel blockers (CCBs) on cerebral hemodynamics and rehabilitation outcome in hypertensive stroke patients. We randomly assigned 35 patients to either the olmesartan (n=18) or amlodipine (n=17) treatment groups for 8 weeks. Changes in cerebral blood flow (CBF) and cerebrovascular reserve capacity (CRC) were quantified using xenon-CT and rehabilitation parameters were also measured. Over 24 h, olmesartan and amlodipine both reduced blood pressure (BP) to similar levels (systolic BP, -16.1+/-2.7 mm Hg vs. -15.7+/-3.1; diastolic BP, -9.2+/-2.9 vs. -8.6+/-3.3 mm Hg, respectively). In olmesartan-treated patients, CBF significantly increased in the affected and unaffected hemispheres, and CRC increased significantly in the affected hemisphere. No increases in CBF and CRC were observed in amlodipine-treated patients. Patients treated with olmesartan showed effective rates of improvement in hand (30.0%), upper extremities (40.0%) and lower extremities (100.0%), measured by Brunnstrom stage; these improvements were significantly different from those in amlodipine-treated patients for the total (P<0.02) and lower extremity (P<0.05) scores. There were no significant differences in Barthel indices and Mini-Mental State Examination (MMSE) scores. Olmesartan, but not amlodipine, had beneficial effects on CBF, CRC and rehabilitation outcomes in hypertensive stroke patients, by a mechanism independent of BP reduction and possibly by normalizing CBF autoregulation. Our results suggest that olmesartan may improve cerebral circulation and rehabilitation in hypertensive stroke patients in whom CBF autoregulation is impaired.
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The influence of the timing of cord clamping on postnatal cerebral oxygenation in preterm neonates: a randomized, controlled trial.
Baenziger, O, Stolkin, F, Keel, M, von Siebenthal, K, Fauchere, JC, Das Kundu, S, Dietz, V, Bucher, HU, Wolf, M
Pediatrics. 2007;(3):455-9
Abstract
OBJECTIVE Our goal was to investigate the effect of placentofetal transfusion on cerebral oxygenation in preterm infants by near-infrared spectroscopy. SUBJECTS A total of 39 preterm infants with a median gestational age of 30.4 weeks were randomly assigned to an experiment group (n = 15) and a control group (n = 24). INTERVENTIONS The delivery of the infants in the experiment group was immediately followed by maternal administration of syntocinon, the infant was placed 15 cm below the placenta, and cord clamping was delayed by 60 to 90 seconds. The infants in the control group were delivered conventionally. At the ages of 4 and 24 hours, cerebral hemoglobin concentrations, cerebral blood volume, and regional tissue oxygenation were measured by near-infrared spectroscopy. RESULTS Cerebral blood volume was not different between the 2 groups at the age of 4 hours (6.1 vs 5.8 mL/100 g of tissue) nor at the age of 24 hours (6.2 vs 6.2 mL/100 g of tissue). Mean regional tissue oxygenation of the experiment group was higher at the ages of 4 hours (69.9% vs 65.5%) and of 24 hours (71.3% vs 68.1%). CONCLUSION Delayed clamping of the umbilical cord improves cerebral oxygenation in preterm infants in the first 24 hours.
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Arterio-jugular differences in serum S-100beta proteins in patients receiving selective cerebral perfusion.
Kunihara, T, Shiiya, N, Bin, L, Yasuda, K
Surgery today. 2006;(1):6-11
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Abstract
PURPOSE The early increase in serum S100beta after cardiopulmonary bypass (CPB) seems to be derived from an extracerebral source. To exclude contamination, we investigated the arterio-jugular differences in S100beta levels in patients receiving selective cerebral perfusion (SCP). We also evaluated the brain-protective effect of SCP by comparing the arterial S100beta levels with those in patients undergoing coronary artery bypass grafting (CABG). METHODS We measured arterial and jugular venous levels of S100beta in ten patients undergoing aortic arch repair with SCP for up to 12 h postoperatively (SCP group). We also measured arterial levels of S100beta in nine patients undergoing CABG (CPB group). RESULTS There was no incidence of hospital death or stroke. The arterial levels of S100beta in both groups were comparable and peaked just after the conclusion of CPB. The arterial and jugular venous levels of S100beta were almost equivalent. The arterio-jugular differences in S100beta levels were negligible, even in our SCP-group patient with postoperative delirium, who had a peak value three times higher than the other patients. CONCLUSIONS The arterio-jugular differences in S100beta did not clarify the origin of their increase. Thus, measuring the jugular venous levels of S100beta in patients without postoperative clinical neurological deterioration would be of little benefit. However, SCP seems to protect the brain against S100beta release as effectively as conventional CPB.
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Hypertonic saline (7.2%) in 6% hydroxyethyl starch reduces intracranial pressure and improves hemodynamics in a placebo-controlled study involving stable patients with subarachnoid hemorrhage.
Bentsen, G, Breivik, H, Lundar, T, Stubhaug, A
Critical care medicine. 2006;(12):2912-7
Abstract
OBJECTIVE To compare the effects of a bolus infusion of hypertonic saline hydroxyethyl starch with the effects of normal saline (placebo) on intracranial pressure (ICP) and cerebral perfusion pressure in patients with spontaneous subarachnoid hemorrhage. DESIGN AND SETTING Prospective, randomized, single-blinded, placebo-controlled study in a university hospital. PATIENTS A total of 22 mechanically ventilated patients with spontaneous subarachnoid hemorrhage with stable ICP between 10 and 20 mm Hg. INTERVENTIONS During the course of 30 mins, 2 mL/kg of either 7.2% saline in 6% hydroxyethyl starch 200/0.5 (HSS) or of normal saline was infused. The effects were observed for another 180 mins. MEASUREMENTS AND MAIN RESULTS Mean change in ICP after intervention (DeltaICP) calculated from the average of all observations was -3.3 (sd 2.6) mm Hg in the HSS group vs. -0.3 (sd 1.3) mm Hg in the normal saline group. Mean difference between the groups (HSS - normal saline) was -3.0 mm Hg (95% confidence interval, -4.9 to -1.1; p = .004). Mean peak change after HSS was -5.6 (range, -0.8 to -12.2) mm Hg after 64 (range, 40 to 115) mins. Mean difference in cerebral perfusion pressure change between the groups (HSS - normal saline) was 5.4 mm Hg (95% confidence interval, 2.2 to 8.6; p = .002), and mean difference in cardiac index change, measured as the area under the curve for the whole study period, corresponded to 0.2 L.min.m (95% confidence interval, 0.03 to 0.4; p = .025). CONCLUSIONS In this placebo-controlled study involving spontaneous subarachnoid hemorrhage patients with normal to moderately increased ICP, 2 mL/kg HSS reduced ICP and increased cerebral perfusion pressure significantly. Maximum effect was reached at twice the infusion time of 30 mins. There were also beneficial hemodynamic effects with increased cardiac index in the HSS group.
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A temporal comparison of BOLD, ASL, and NIRS hemodynamic responses to motor stimuli in adult humans.
Huppert, TJ, Hoge, RD, Diamond, SG, Franceschini, MA, Boas, DA
NeuroImage. 2006;(2):368-82
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Abstract
In this study, we have preformed simultaneous near-infrared spectroscopy (NIRS) along with BOLD (blood oxygen level dependent) and ASL (arterial spin labeling)-based fMRI during an event-related motor activity in human subjects in order to compare the temporal dynamics of the hemodynamic responses recorded in each method. These measurements have allowed us to examine the validity of the biophysical models underlying each modality and, as a result, gain greater insight into the hemodynamic responses to neuronal activation. Although prior studies have examined the relationships between these two methodologies through similar experiments, they have produced conflicting results in the literature for a variety of reasons. Here, by employing a short-duration, event-related motor task, we have been able to emphasize the subtle temporal differences between the hemodynamic parameters with a high contrast-to-noise ratio. As a result of this improved experimental design, we are able to report that the fMRI measured BOLD response is more correlated with the NIRS measure of deoxy-hemoglobin (R = 0.98; P < 10(-20)) than with oxy-hemoglobin (R = 0.71), or total hemoglobin (R = 0.53). This result was predicted from the theoretical grounds of the BOLD response and is in agreement with several previous works [Toronov, V.A.W., Choi, J.H., Wolf, M., Michalos, A., Gratton, E., Hueber, D., 2001. "Investigation of human brain hemodynamics by simultaneous near-infrared spectroscopy and functional magnetic resonance imaging." Med. Phys. 28 (4) 521-527.; MacIntosh, B.J., Klassen, L.M., Menon, R.S., 2003. "Transient hemodynamics during a breath hold challenge in a two part functional imaging study with simultaneous near-infrared spectroscopy in adult humans". NeuroImage 20 1246-1252.; Toronov, V.A.W., Walker, S., Gupta, R., Choi, J.H., Gratton, E., Hueber, D., Webb, A., 2003. "The roles of changes in deoxyhemoglobin concentration and regional cerebral blood volume in the fMRI BOLD signal" Neuroimage 19 (4) 1521-1531]. These data have also allowed us to examine more detailed measurement models of the fMRI signal and comment on the roles of the oxygen saturation and blood volume contributions to the BOLD response. In addition, we found high correlation between the NIRS measured total hemoglobin and ASL measured cerebral blood flow (R = 0.91; P < 10(-10)) and oxy-hemoglobin with flow (R = 0.83; P < 10(-05)) as predicted by the biophysical models. Finally, we note a significant amount of cross-modality, correlated, inter-subject variability in amplitude change and time-to-peak of the hemodynamic response. The observed co-variance in these parameters between subjects is in agreement with hemodynamic models and provides further support that fMRI and NIRS have similar vascular sensitivity.