Orthostatic intolerance after spaceflight

1996 ◽  
Vol 81 (1) ◽  
pp. 7-18 ◽  
Author(s):  
J. C. Buckey ◽  
L. D. Lane ◽  
B. D. Levine ◽  
D. E. Watenpaugh ◽  
S. J. Wright ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Space Shuttle ◽  
Orthostatic Intolerance ◽  
Peripheral Resistance ◽  
Systemic Hemodynamic ◽  
Vasoconstrictor Response ◽  
Before And After ◽  
Underlying Mechanisms

Orthostatic intolerance occurs commonly after spaceflight, and important aspects of the underlying mechanisms remain unclear. We studied 14 individuals supine and standing before and after three space shuttle missions of 9-14 days. After spaceflight, 9 of the 14 (64%) crew members could not complete a 10-min stand test that all completed preflight. Pre- and postflight supine hemodynamics were similar in both groups except for slightly higher systolic and mean arterial pressures preflight in the finishers [15 +/- 3.7 and 8 +/- 1.2 (SE) mmHg, respectively; P < 0.05]. Postflight, finishers and nonfinishers had equally large postural reductions in stroke volume (-47 +/- 3.7 and -48 +/- 3.3 ml, respectively) and increases in heart rate (35 +/- 6.6 and 51 +/- 5.2 beats/min, respectively). Cardiac output during standing was also similar (3.6 +/- 0.4 and 4.1 +/- 0.3 l/min, respectively). However, the finishers had a greater postflight vasoconstrictor response with higher total peripheral resistance during standing (22.3 +/- 1.2 units preflight and 29.4 +/- 2.3 units postflight) than did the nonfinishers (20.1 +/- 1.1 units preflight and 19.9 +/- 1.4 units postflight). We conclude that 1) the primary systemic hemodynamic event, i.e., the postural decrease in stroke volume, was similar in finishers and nonfinishers and 2) the heart rate response and cardiac output during standing were not significantly different, but 3) the postural vasoconstrictor response was significantly greater among the finishers (P < 0.01).

Leg crossing with muscle tensing, a physical counter-manoeuvre to prevent syncope, enhances leg blood flow

2007 ◽  
Vol 112 (3) ◽  
pp. 193-201 ◽  
Author(s):  
Jan T. Groothuis ◽  
Nynke van Dijk ◽  
Walter ter Woerds ◽  
Wouter Wieling ◽  
Maria T. E. Hopman
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Orthostatic Intolerance ◽  
Peripheral Resistance ◽  
Haemodynamic Effects ◽  
Vascular Conductance ◽  
Leg Blood Flow ◽  
Head Up Tilt

In patients with orthostatic intolerance, the mechanisms to maintain BP (blood pressure) fail. A physical counter-manoeuvre to postpone or even prevent orthostatic intolerance in these patients is leg crossing combined with muscle tensing. Although the central haemodynamic effects of physical counter-manoeuvres are well documented, not much is known about the peripheral haemodynamic events. Therefore the purpose of the present study was to examine the peripheral haemodynamic effects of leg crossing combined with muscle tensing during 70° head-up tilt. Healthy subjects (n=13) were monitored for 10 min in the supine position followed by 10 min in 70° head-up tilt and, finally, for 2 min of leg crossing with muscle tensing in 70° head-up tilt. MAP (mean arterial BP), heart rate, stroke volume, cardiac output and total peripheral resistance were measured continuously by Portapres. Leg blood flow was measured using Doppler ultrasound. Leg vascular conductance was calculated as leg blood flow/MAP. A significant increase in MAP (13 mmHg), stroke volume (27%) and cardiac output (18%), a significant decrease in heart rate (−5 beats/min) and no change in total peripheral resistance during the physical counter-manoeuvre were observed when compared with baseline 70° head-up tilt. A significant increase in leg blood flow (325 ml/min) and leg vascular conductance (2.9 arbitrary units) were seen during the physical counter-manoeuvre when compared with baseline 70° head-up tilt. In conclusion, the present study indicates that the physical counter-manoeuvre of leg crossing combined with muscle tensing clearly enhances leg blood flow and, at the same time, elevates MAP.

Pet CO2 inversely affects MSNA response to orthostatic stress

2001 ◽  
Vol 281 (3) ◽  
pp. H1040-H1046 ◽  
Author(s):  
J. Kevin Shoemaker ◽  
Debbie D. O'Leary ◽  
Richard L. Hughson
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Orthostatic Intolerance ◽  
Muscle Sympathetic Nerve Activity ◽  
Peripheral Resistance ◽  
Burst Frequency ◽  
Head Up Tilt ◽  
End Tidal ◽  
Combined Data

Arterial hypocapnia has been associated with orthostatic intolerance. Therefore, we tested the hypothesis that hypocapnia may be detrimental to increases in muscle sympathetic nerve activity (MSNA) and total peripheral resistance (TPR) during head-up tilt (HUT). Ventilation was increased ∼1.5 times above baseline for each of three conditions, whereas end-tidal Pco 2 (Pet CO2 ) was clamped at normocapnic (Normo), hypercapnic (Hyper; +5 mmHg relative to Normo), and hypocapnic (Hypo; −5 mmHg relative to Normo) conditions. MSNA (microneurography), heart rate, blood pressure (BP, Finapres), and cardiac output (Q, Doppler) were measured continuously during supine rest and 45° HUT. The increase in heart rate when changing from supine to HUT ( P < 0.001) was not different across Pet CO2 conditions. MSNA burst frequency increased similarly with HUT in all conditions ( P < 0.05). However, total MSNA and the increase in total amplitude relative to baseline (%ΔMSNA) increased more when changing to HUT during Hypo compared with Hyper ( P < 0.05). Both BP and Q were higher during Hyper than both Normo and Hypo (main effect; P < 0.05). Therefore, the MSNA response to HUT varied inversely with levels of Pet CO2 . The combined data suggest that augmented cardiac output with hypercapnia sustained blood pressure during HUT leading to a diminished sympathetic response.

Effect of sympathetic blockade on diurnal variation of hemodynamic patterns

1989 ◽  
Vol 256 (3) ◽  
pp. R778-R785 ◽  
Author(s):  
M. I. Talan ◽  
B. T. Engel
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Total Peripheral Resistance ◽  
Peripheral Resistance ◽  
Base Line ◽  
Sympathetic Blockade ◽  
Selective Blockade ◽  
Arterial Blood

Heart rate, stroke volume, and intra-arterial blood pressure were monitored continuously in each of four monkeys, 18 consecutive h/day for several weeks. The mean heart rate, stroke volume, cardiac output, systolic and diastolic blood pressure, and total peripheral resistance were calculated for each minute and reduced to hourly means. After base-line data were collected for approximately 20 days, observation was continued for equal periods of time under conditions of alpha-sympathetic blockade, beta-sympathetic blockade, and double sympathetic blockade. This was achieved by intra-arterial infusion of prazosin, atenolol, or a combination of both in concentration sufficient for at least 75% reduction of response to injection of agonists. The results confirmed previous findings of a diurnal pattern characterized by a fall in cardiac output and a rise in total peripheral resistance throughout the night. This pattern was not eliminated by selective blockade, of alpha- or beta-sympathetic receptors or by double sympathetic blockade; in fact, it was exacerbated by sympathetic blockade, indicating that the sympathetic nervous system attenuates these events. Because these findings indicate that blood volume redistribution is probably not the mechanism mediating the observed effects, we have hypothesized that a diurnal loss in plasma volume may mediate the fall in cardiac output and that the rise in total peripheral resistance reflects a homeostatic regulation of arterial pressure.

Minute-to-minute covariations in cardiovascular activity of conscious dogs

1979 ◽  
Vol 236 (3) ◽  
pp. H434-H439 ◽  
Author(s):  
D. E. Anderson ◽  
J. E. Yingling ◽  
K. Sagawa
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Peripheral Resistance ◽  
Aversive Stimulation ◽  
Conscious Dogs ◽  
Cardiovascular Activity ◽  
Independent Events ◽  
Constant Coefficient Of Variation ◽  
Cardiovascular Variables

Cardiovascular activity of chronically instrumented conscious dogs was monitored continuously during daily sessions of rest or of intermittent aversive stimulation. Data analysis of minute-to-minute averages revealed that cardiovascular variables changed in patterns, rather than as isolated independent events. Variations in cardiac output were highly positively correlated with concurrent variations in heart rate in all subjects under both conditions (mean r = +0.93). Variations in heart rate were two to five times as great as stroke volume, which was remarkably constant (coefficient of variation averaged only 4.6%). Variations in mean arterial pressure were consistently correlated with the variations in cardiac output (mean r = + 0.66) and heart rate (mean r = +0.68), but were poorly correlated with the small changes in stroke volume (mean r = -0.17) and total peripheral resistance (mean r = -0.16).

Cardiovascular changes during acceleration stress in dogs

1960 ◽  
Vol 15 (6) ◽  
pp. 1065-1068 ◽  
Author(s):  
Edward J. Hershgold ◽  
Sheldon H. Steiner
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Technical Assistance ◽  
Peripheral Resistance ◽  
Cardiovascular Changes ◽  
Positive Acceleration ◽  
Acceleration Stress ◽  
Circulatory Disturbances

Dogs were accelerated on the Wright-Patterson AFB human centrifuge in positive and transverse vectors. Cardiac output, blood pressure and heart rate were measured, and stroke volume and peripheral resistance calculated. In positive (headward) acceleration, the cardiac output and stroke volume were reduced; the peripheral resistance was increased. In the transverse vectors, the cardiac output was stable or increased; stroke volume was stable, and peripheral resistance was reduced. The results suggest that the circulatory disturbances associated with positive acceleration may limit tolerance to acceleration and that these may be avoided in transverse acceleration. Note: (With the Technical Assistance of Peter Grenell) Submitted on December 3, 1959

Changes in sympathoadrenal response to standing in humans after spaceflight

1995 ◽  
Vol 79 (2) ◽  
pp. 428-433 ◽  
Author(s):  
P. A. Whitson ◽  
J. B. Charles ◽  
W. J. Williams ◽  
N. M. Cintron
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Stroke Volume ◽  
Space Shuttle ◽  
Cardiovascular Responses ◽  
Plasma Norepinephrine ◽  
Plasma Catecholamine ◽  
Blood Samples ◽  
Before And After ◽  
Catecholamine Levels

Plasma catecholamine levels and cardiovascular responses to standing were determined in astronauts before and after several Space Shuttle missions. Blood pressure, heart rate, and cardiac output were measured and blood samples for catecholamine analyses were drawn at the end of the supine and standing periods. Supine plasma norepinephrine and epinephrine concentrations increased 34 and 65%, respectively, on landing day compared with before flight. Standing on landing day resulted in a 65 and 91% increase in plasma norepinephrine and epinephrine, respectively. Supine and standing norepinephrine levels remained elevated 3 days after landing while epinephrine levels returned to preflight levels. On landing day, supine heart rate and systolic blood pressure increased 18 and 8.9%, respectively, and standing heart rate and diastolic blood pressure were elevated by 38 and 19%, respectively. On standing, stroke volume was decreased by 26% on landing day compared with before flight. Collectively, these data indicate that the decreased orthostatic function after spaceflight results largely from the decreased stroke volume. Possible mechanisms contributing to this condition are discussed.

scholarly journals Abnormal cardiovascular response to nitroglycerin in migraine

Cephalalgia ◽  
2019 ◽  
Vol 40 (3) ◽  
pp. 266-277
Author(s):  
Willebrordus PJ van Oosterhout ◽  
Guus G Schoonman ◽  
Dirk P Saal ◽  
Roland D Thijs ◽  
Michel D Ferrari ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Stroke Volume ◽  
Total Peripheral Resistance ◽  
Cardiovascular Response ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Initial Increase

Introduction Migraine and vasovagal syncope are comorbid conditions that may share part of their pathophysiology through autonomic control of the systemic circulation. Nitroglycerin can trigger both syncope and migraine attacks, suggesting enhanced systemic sensitivity in migraine. We aimed to determine the cardiovascular responses to nitroglycerin in migraine. Methods In 16 women with migraine without aura and 10 age- and gender-matched controls without headache, intravenous nitroglycerin (0.5 µg·kg−1·min−1) was administered. Finger photoplethysmography continuously assessed cardiovascular parameters (mean arterial pressure, heart rate, cardiac output, stroke volume and total peripheral resistance) before, during and after nitroglycerin infusion. Results Nitroglycerin provoked a migraine-like attack in 13/16 (81.2%) migraineurs but not in controls ( p = .0001). No syncope was provoked. Migraineurs who later developed a migraine-like attack showed different responses in all parameters vs. controls (all p < .001): The decreases in cardiac output and stroke volume were more rapid and longer lasting, heart rate increased, mean arterial pressure and total peripheral resistance were higher and decreased steeply after an initial increase. Discussion Migraineurs who developed a migraine-like attack in response to nitroglycerin showed stronger systemic cardiovascular responses compared to non-headache controls. The stronger systemic cardiovascular responses in migraine suggest increased systemic sensitivity to vasodilators, possibly due to insufficient autonomic compensatory mechanisms.

Autonomic Cardiovascular Dysregulation at Rest and During Stress in Chronically Low Blood Pressure

2019 ◽  
Vol 33 (1) ◽  
pp. 39-53 ◽  
Author(s):  
Stefan Duschek ◽  
Alexandra Hoffmann ◽  
Casandra I. Montoro ◽  
Gustavo A. Reyes del Paso
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Total Peripheral Resistance ◽  
Baroreflex Sensitivity ◽  
Peripheral Resistance ◽  
Control Group ◽  
Low Blood Pressure

Abstract. Chronic low blood pressure (hypotension) is accompanied by symptoms such as fatigue, reduced drive, faintness, dizziness, cold limbs, and concentration difficulties. The study explored the involvement of aberrances in autonomic cardiovascular control in the origin of this condition. In 40 hypotensive and 40 normotensive subjects, impedance cardiography, electrocardiography, and continuous blood pressure recordings were performed at rest and during stress induced by mental calculation. Parameters of cardiac sympathetic control (i.e., stroke volume, cardiac output, pre-ejection period, total peripheral resistance), parasympathetic control (i.e., heart rate variability), and baroreflex function (i.e., baroreflex sensitivity) were obtained. The hypotensive group exhibited markedly lower stroke volume, heart rate, and cardiac output, as well as higher pre-ejection period and baroreflex sensitivity than the control group. Hypotension was furthermore associated with a smaller blood pressure response during stress. No group differences arose in total peripheral resistance and heart rate variability. While reduced beta-adrenergic myocardial drive seems to constitute the principal feature of the autonomic impairment that characterizes chronic hypotension, baroreflex-related mechanisms may also contribute to this state. Insufficient organ perfusion due to reduced cardiac output and deficient cardiovascular adjustment to situational requirements may be involved in the manifestation of bodily and mental symptoms.

Cardiovascular Effects of Moxibustion at Jen Chung (Go-26) during Halothane Anesthesia in Dogs

1975 ◽  
Vol 03 (03) ◽  
pp. 245-261 ◽  
Author(s):  
Do Chil Lee ◽  
Myung O. Lee ◽  
Donald H. Clifford
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Stroke Volume ◽  
Total Peripheral Resistance ◽  
Venous Pressure ◽  
Peripheral Resistance ◽  
Cardiovascular Effects ◽  
Halothane Anesthesia

The cardiovascular effects of moxibustion at Jen Chung (Go-26) in 10 dogs under halothane anesthesia were compared to 5 dogs under halothane anesthesia without moxibustion and 5 dogs under halothane anesthesia in which moxibustion was effected at a neutral or non-acupuncture site. Cardiac output, stroke volume, heart rate, mean arterial pressure, central venous pressure, total peripheral resistance, pH, PaCO2, PaO2 and base deficit were measured over a two-hour period. A significant increase in cardiac output and stroke volume and a significant decrease in the total peripheral resistance were observed in the group which was stimulated by moxibustion at Jen Chun (Go-26). Heart rate, mean arterial pressure and pulse pressure were significantly increase during the early part of the two-hour period in the same group. The cardiovascular effects of moxibustion at Jen Chung (Go-26) which were observed at the end of the two hours were also present in two dogs in which measurements were continued for two additional hours.

Effects of reserpine on circulation of the rat after microwave irradiation

1962 ◽  
Vol 202 (6) ◽  
pp. 1171-1174 ◽  
Author(s):  
Theodore Cooper ◽  
Teresa Pinakatt ◽  
Max Jellinek ◽  
Alfred W. Richardson
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Continuous Wave ◽  
Peripheral Resistance ◽  
Thermal Response ◽  
Cardiac Response ◽  
Tissue Temperature ◽  
White Rats

Hyperthermia of 40.5 C was induced in anesthetized white rats by microwave exposure (2,450-Mc continuous wave, .08 w/cm2). Thermal response was accompanied by increased cardiac output, stroke volume, cardiac work, and heart rate. Blood pressure and total peripheral resistance decreased. Administration of reserpine as a single dose of 2.5 mg/kg body wt. 1 day before the experiment depleted the myocardial norepinephrine, but did not eliminate the accelerated heart rate and increase of cardiac output during hyperthermia. Hyperthermia after reserpine did not alter significantly the stroke volume and blood pressure, and the peripheral resistance decreased. These data suggest that the circulatory adaptation to microwave hyperthermia is mediated not only through the sympathetic nervous system, but by other mechanisms such as direct cardiac response to the increased tissue temperature.

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