WISE 2005: responses of women to sublingual nitroglycerin before and after 56 days of 6° head-down bed rest

2012 ◽  
Vol 113 (3) ◽  
pp. 434-441 ◽  
Author(s):  
K. A. Zuj ◽  
H. Edgell ◽  
J. K. Shoemaker ◽  
M. A. Custaud ◽  
P. Arbeille ◽  
...  
Keyword(s):  
Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Femoral Artery ◽  
Peripheral Resistance ◽  
Resistance Index ◽  
Cardiovascular Effects ◽  
Cardiovascular Responses ◽  
Bed Rest ◽  
Sublingual Nitroglycerin

This study tested the hypothesis that cardiovascular effects of sublingual nitroglycerin (NG) would be exaggerated after 56 days of 6° head-down bed rest (HDBR) in women, and that an aerobic and resistive exercise countermeasure (EX, n = 8) would reduce the effect compared with HDBR without exercise (CON, n = 7). Middle cerebral artery maximal blood flow velocity (CBFV), cardiac stroke volume (SV), and superficial femoral artery blood flow (Doppler ultrasound) were recorded at baseline rest and for 5 min following 0.3 mg sublingual NG. Post-HDBR, NG caused greater increases in heart rate (HR) in CON compared with EX (+24.9 ± 7.7 and +18.8 ± 6.6 beats/min, respectively, P < 0.0001). The increase in HR combined with reductions in SV to maintain cardiac output. Systolic, mean, and pulse pressures were reduced 5–10 mmHg by NG, but total peripheral resistance was only slightly reduced at 3 min after NG. Reductions in CBFV of −12.5 ± 3.8 cm/s were seen after NG, but a reduction in the Doppler resistance index suggested dilation of the middle cerebral artery with no differences after HDBR. The femoral artery dilated with NG and blood flow was reduced ∼50% with the appearance of large negative waves suggesting a marked increase in downstream resistance, but there were no effects of HDBR. In general, responses of women to NG were not altered by HDBR; the greater increase in HR in CON but not EX was probably a consequence of cardiovascular deconditioning. These results contrast with the hypothesis and a previous investigation of men after HDBR by revealing no change in cardiovascular responses to exogenous nitric oxide.

scholarly journals Is there any influence of breastfeeding on the cerebral blood flow? A review of 256 healthy newborns

2012 ◽  
Vol 45 (5) ◽  
pp. 263-266 ◽  
Author(s):  
Alexandra Maria Vieira Monteiro ◽  
Claudio Marcio Amaral de Oliveira Lima ◽  
Paula Medina
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Pulsatility Index ◽  
Cerebral Blood Flow Velocity ◽  
Resistance Index ◽  
Left Middle Cerebral Artery ◽  
Mean Velocity ◽  
The Right

OBJECTIVE: To investigate whether breastfeeding influence the cerebral blood-flow velocity. MATERIALS AND METHODS: The present study included 256 healthy term neonates, all of them with appropriate weight for gestational age, 50.8% being female. Pulsatility index, resistance index and mean velocity were measured during breastfeeding or resting in the anterior cerebral artery, in the left middle cerebral artery, and in the right middle cerebral artery of the neonates between their first 10 and 48 hours of life. The data were analyzed by means of a paired t-test, Brieger's f-test for analysis of variance and linear regression, with p < 0.01 being accepted as statistically significant. RESULTS: Mean resistance index decreased as the mean velocity increased significantly during breastfeeding. Pulsatility index values decreased as much as the resistance index, but in the right middle cerebral artery it was not statistically significant. CONCLUSION: Breastfeeding influences the cerebral blood flow velocities.

WISE-2005: adrenergic responses of women following 56-days, 6° head-down bed rest with or without exercise countermeasures

2007 ◽  
Vol 293 (6) ◽  
pp. R2343-R2352 ◽  
Author(s):  
Heather Edgell ◽  
Kathryn A. Zuj ◽  
Danielle K. Greaves ◽  
J. Kevin Shoemaker ◽  
Marc-Antoine Custaud ◽  
...  
Keyword(s):  
Vascular Resistance ◽  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Peripheral Resistance ◽  
Resistance Index ◽  
Cardiovascular Responses ◽  
Bed Rest ◽  
Nutritional Supplement ◽  
Exercise Group ◽  
Adrenergic Stimulation

We tested the hypotheses that women completing 56 days, 6° head-down bed-rest (HDBR) would have changes in sensitivity of cardiovascular responses to adrenergic receptor stimulation and that frequent aerobic and resistive exercise would prevent these changes. Twenty-four women, eight controls, eight exercisers (lower body negative pressure treadmill and flywheel resistance exercise), and eight receiving nutritional supplement but no exercise were studied in baseline and during administration of the β-agonist isoproterenol (ISO) and the α- and β-agonist norepinephrine (NOR). In the control and nutrition groups, HDBR increased heart rate (HR) and reduced stroke volume (SV), and there was a significantly greater increase in HR with ISO after HDBR. In contrast, the HR and SV of the exercise group were unchanged from pre-HDBR. After HDBR, leg vascular resistance (LVR) was greater than pre-HDBR in the exercise group but reduced in control and nutrition. LVR was reduced with ISO and increased with NOR. Changes in total peripheral resistance were similar to those of LVR but of smaller magnitude, perhaps because changes in cerebrovascular resistance index were directionally opposite to those of LVR. There were no changes in sensitivity of the vascular resistance responses to adrenergic stimulation. The HR response might reflect a change in sensitivity or a necessary response to the reduction in SV after HDBR in control and nutrition groups. The reduced peripheral vascular resistance after HDBR might help to explain orthostatic intolerance in women. Exercise was an effective countermeasure to the HDBR effects.

scholarly journals Safety, hemodynamic effects, and detection of acute xenon inhalation: rationale for banning xenon from sport

2019 ◽  
Vol 127 (6) ◽  
pp. 1511-1518 ◽  
Author(s):  
Justin S. Lawley ◽  
Hannes Gatterer ◽  
Katrin A. Dias ◽  
Erin J. Howden ◽  
Satyam Sarma ◽  
...  
Keyword(s):  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Total Peripheral Resistance ◽  
Substantial Reduction ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Gas Chromatography Mass Spectrometry ◽  
Detection Rates ◽  
Task Failure ◽  
Breathing Apparatus

This study aimed to quantify the sedative effects, detection rates, and cardiovascular responses to xenon. On 3 occasions, participants breathed xenon (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) in a nonblinded design. Sedation was monitored by a board-certified anesthesiologist. During 70% xenon, participants were also verbally instructed to operate a manual value with time-to-task failure being recorded. Beat-by-beat hemodynamics were measured continuously by ECG, photoplethysmography, and transcranial Doppler. Over 48 h postadministration, xenon was measured in blood and urine by gas chromatography-mass spectrometry. Xenon caused variable levels of sedation and restlessness. Task failure of the self-operating value occurred at 60–90 s in most individuals. Over the first minute, 50% and 70% xenon caused a substantial reduction in total peripheral resistance ( P < 0.05). All dosages caused an increase in cardiac output ( P < 0.05). By the end of xenon inhalation, slight hypertension was observed after all three doses ( P < 0.05), with an increase in middle cerebral artery velocity ( P < 0.05). Xenon was consistently detected, albeit in trace amounts, up to 3 h after all three doses of xenon inhalation in blood and urine with variable results thereafter. Xenon inhalation caused sedation incompatible with self-operation of a breathing apparatus, thus causing a potential life-threatening condition in the absence of an anesthesiologist. Yet, xenon can only be reliably detected in blood and urine up to 3 h postacute dosing. NEW & NOTEWORTHY Breathing xenon in dosages conceivable for doping purposes (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) causes an initial rapid fall in total peripheral resistance with tachycardia and thereafter a mild hypertension with elevated middle cerebral artery velocity. These dose duration intervals cause sedation that is incompatible with operating a breathing apparatus and can only be detected in blood and urine samples with a high probability for up to ~3 h.

scholarly journals Effects of maternal abdominal decompression on umbilical artery and fetal middle cerebral artery blood flow

2015 ◽  
Vol 49 (3) ◽  
Author(s):  
Sara Mugerli ◽  
Gordana Njenjić ◽  
Vesna Fabjan Vodušek ◽  
Miha Lučovnik
Keyword(s):  
Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Umbilical Artery ◽  
Fetal Brain ◽  
Resistance Index ◽  
Doppler Velocity ◽  
Before And After ◽  
Student’S T ◽  
Abdominal Decompression

Introduction: Maternal abdominal decompression during pregnancy could be used in an attempt to improve utero-placental blood flow. We utilized Doppler ultrasonography to investigate the effects of this procedure on blood flow in the umbilical artery and fetal middle cerebral artery. Methods: Women (n = 23) with singleton pregnancies attending antenatal abdominal decompression were enrolled in the study. Doppler velocity waveforms were obtained from umbilical artery and fetal middle cerebral artery before and after a 30-minute decompression session. Resistance indices were compared using the Student's t - test (p < 0.05 significant). Results: 23 healthy pregnant women were included at an average gestational age of 36+1 weeks. The mean resistance index before decompression in the umbilical artery was 0.58 (s = 0.10) and after decompression 0.54 (s = 0.07, p = 0.06). In the middle cerebral artery the values were 0.72 (s = 0.11) and 0.77 (s = 0.08), respectively (p = 0.01). Discussion and conclusion: Significantly increased resistance index in the middle cerebral artery implies a higher fetal brain oxygenation after decompression. This is further corroborated by the trend towards a decrease in umbilical artery resistance index. The effects of decompression could be beneficial in pregnancies complicated by IUGR or hypertensive disorders of pregnancy.

scholarly journals Fetal Aortic-cerebral Doppler Resistance Index Ratio: An Indicator of Physiologic Blood Flow Distribution

2009 ◽  
Vol 3 (3) ◽  
pp. 91-96
Author(s):  
Zoltán Tóth ◽  
János Aranyosi ◽  
Tamás Deli ◽  
Péter Bettembuk ◽  
Bence Kozma ◽  
...  
Keyword(s):  
Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Resistance Index ◽  
Flow Distribution ◽  
Arterial Blood Flow ◽  
Blood Flow Distribution ◽  
Descending Aorta ◽  
Arterial Blood ◽  
Index Ratio

Abstract Identical hemodynamic impedance and constant ratio of the fetal descending aorta and middle cerebral artery of uncomplicated pregnancies at term. Fetal aortic-cerebral Doppler resistance index ratio: An indicator of physiologic blood flow distribution. Objective To interpret the physiologic fetal arterial blood flow distribution by relating the vascular impedance of the fetal descending aorta (DA) and middle cerebral artery (MCA) and to establish the reference ranges for the aortic-cerebral Doppler resistance index ratio (ACRI). Study design Ninety-six patients with uncomplicated pregnancies were recruited for the cross-sectional assessment of the Doppler resistance index (RI) in the fetal DA and MCA between the 38rd and 40th weeks of gestation. The normal ranges of the ACRI were calculated. A cut-off value was designed to facilitate the clinical application of the ACRI. Results Between the 38th and 40th weeks of gestation in normal pregnancies the ACRI of healthy fetuses is constant, the overall mean is: 1.062 (+/– 0.087). A single cut-off value of 1.2 is recommended to assist separating normal and pathologic arterial blood flow patterns. Conclusion The normal ACRI reflects the identical vascular resistance of the descending aorta and the cerebral vessels, which maintains the physiologic fetal central arterial blood flow. Additional clinical studies are necessary to assess the diagnostic efficacy of the abnormal ACRI (>1.2) as a potentially useful marker of the centralized arterial circulation indicating the early stage of fetal hypoxemic jeopardy.

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