Early effects of oral salt on plasma volume, orthostatic tolerance, and baroreceptor sensitivity in patients with syncope

1998 ◽  
Vol 8 (4) ◽  
pp. 231-235 ◽  
Author(s):  
Benjamin L. Mtinangi ◽  
Roger Hainsworth
Keyword(s):  
Plasma Volume ◽  
Orthostatic Tolerance ◽  
Baroreceptor Sensitivity ◽  
Early Effects

Relationship between Plasma Volume, Carotid Baroreceptor Sensitivity and Orthostatic Tolerance

1995 ◽  
Vol 88 (4) ◽  
pp. 463-470 ◽  
Author(s):  
H. El-Sayed ◽  
R. Hainsworth
Keyword(s):  
Plasma Volume ◽  
Pulse Interval ◽  
Blue Dye ◽  
Orthostatic Tolerance ◽  
Lower Body ◽  
Baroreceptor Sensitivity ◽  
Carotid Baroreceptor ◽  
Asymptomatic Volunteers ◽  
Head Up Tilt ◽  
Blood Volumes

1. Studies were carried out on 43 otherwise healthy patients referred for investigation for attacks of syncope of unknown cause and on six healthy volunteers. 2. Plasma volume was determined by Evans Blue dye dilution and blood volume was estimated using haematocrit. Carotid baroreceptor sensitivity was determined from the changes in pulse interval in response to subatmospheric pressures applied to the neck overlying the carotid sinuses, and orthostatic tolerance was assessed as the time to presyncope in a test of head-up tilt, followed by the addition of graded lower body suction. 3. Eight patients and one volunteer fainted during head-up tilt alone, 23 patients and two volunteers fainted during tilt with lower body suction at −20 mmHg and 12 patients and three volunteers either fainted during suction at −40 mmHg or tolerated the entire procedure. 4. Although plasma and blood volumes were higher in males than females, the values normalized for either body weight or for calculated lean body mass were not different between male and female patients and asymptomatic volunteers. The subjects showing the greatest resistance to syncope were found to have significantly larger plasma and blood volumes (P < 0.0001) and significantly smaller baroreceptor sensitivities (P < 0.0002) than those who fainted earlier. 5. There was a highly significant positive correlation in all subjects between orthostatic tolerance (time to onset of syncope) and plasma and blood volumes (r = 0.60, P < 0.0001; r = 0.53, P < 0.0002), and highly significant negative correlations between time to syncope and baroreceptor sensitivity (r = −0.61, P < 0.0001) and between baroreceptor sensitivity and plasma and blood volumes (r = −0.54, P < 0.0001; r = −0.31, P < 0.03). 6. These results show that tolerance to orthostatic stress is favoured by large plasma and blood volumes and a low sensitivity of the carotid baroreceptor—heart rate reflex.

scholarly journals Moderate Exercise Based on Artificial Gravity Preserves Orthostatic Tolerance and Exercise Capacity During Short-Term Head-Down Bed Rest

2017 ◽  
pp. 567-580 ◽  
Author(s):  
X.-T. LI ◽  
C.-B. YANG ◽  
Y.-S. ZHU ◽  
J. SUN ◽  
F. SHI ◽  
...  
Keyword(s):  
Aerobic Exercise ◽  
Plasma Volume ◽  
Systolic Function ◽  
Bed Rest ◽  
Control Group ◽  
Orthostatic Tolerance ◽  
Short Term ◽  
Exercise Endurance ◽  
Physical Deconditioning ◽  
Cardiac Systolic Function

Numerous countermeasures have been proposed to minimize microgravity-induced physical deconditioning, but their benefits are limited. The present study aimed to investigate whether personalized aerobic exercise based on artificial gravity (AG) mitigates multisystem physical deconditioning. Fourteen men were assigned to the control group (n=6) and the countermeasure group (CM, n=8). Subjects in the CM group were exposed to AG (2 Gz at foot level) for 30 min twice daily, during which time cycling exercise of 80-95 % anaerobic threshold (AT) intensity was undertaken. Orthostatic tolerance (OT), exercise tests, and blood assays were determined before and after 4 days head-down bed rest (HDBR). Cardiac systolic function was measured every day. After HDBR, OT decreased to 50.9 % and 77.5 % of pre-HDBR values in control and CM groups, respectively. Exercise endurance, maximal oxygen consumption, and AT decreased to 96.5 %, 91.5 % and 91.8 % of pre-HDBR values, respectively, in the control group. Nevertheless, there were slight changes in the CM group. HDBR increased heart rate, sympathetic activity, and the pre-ejection period, but decreased plasma volume, parasympathetic activity and left-ventricular ejection time in the control group, whereas these effects were eliminated in the CM group. Aldosterone had no change in the control group but increased significantly in the CM group. Our study shows that 80-95 % AT aerobic exercise based on 2 Gz of AG preserves OT and exercise endurance, and affects body fluid regulation during short-term HDBR. The underlying mechanisms might involve maintained cardiac systolic function, preserved plasma volume, and improved sympathetic responses to orthostatic stress.

The Early Effects of Intravenous Frusemide on Central Haemodynamics, Venous Tone and Plasma Renin Activity

1975 ◽  
Vol 49 (6) ◽  
pp. 551-555 ◽  
Author(s):  
B. Hesse ◽  
I. Nielsen ◽  
H. Lund-Jacobsen
Keyword(s):  
Plasma Renin Activity ◽  
Plasma Volume ◽  
Plasma Renin ◽  
Right Heart Catheterization ◽  
Renin Activity ◽  
Heart Catheterization ◽  
Volume Loss ◽  
Volume Depletion ◽  
Venous Tone ◽  
Early Effects

1. Nine patients with clinically unimportant heart disease or benign essential hypertension were given frusemide intravenously during right-heart catheterization. 2. Pressures in both atria decreased rapidly and in parallel. The magnitude of the pressure decrease was clearly related to decrease in plasma volume loss. 3. Plasma renin activity increased significantly after 5 min (P < 0·01), but did not correlate with plasma volume loss. 4. Venous tone in the forearm was unchanged. 5. It is concluded that the pressure reduction was secondary to plasma volume depletion through diuresis and that increased plasma renin activity was mainly caused by intrarenal changes.

Abstract P192: Orthostatic Tolerance Before And After 60 Days Of Strict Head Down Tilt Bedrest With And Without Daily Artificial Gravity Training

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Jan Hoenemann ◽  
Fabian Hoffmann ◽  
Stefan Moestl ◽  
Karten Heusser ◽  
Edwin Mulder ◽  
...  
Keyword(s):  
Stroke Volume ◽  
Plasma Volume ◽  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Responses ◽  
Pooled Analysis ◽  
Artificial Gravity ◽  
Control Group ◽  
Orthostatic Tolerance ◽  
Before And After

Background: Orthostatic intolerance occurs after space flight, immobilization and in patients with autonomic diseases, so there is a need for more effective countermeasures. We hypothesized that daily artificial gravity elicited through short-arm centrifugation attenuates plasma volume loss and orthostatic intolerance following 60 days of HDTBR, which models cardiovascular responses to weightlessness. Methods: We studied 24 healthy persons (8 women, 33.4±9.3 yr, 24.3±2.1 kg/m2) exposed to 60d HDTBR. Subjects were assigned to 30 min/d continuous short arm centrifugation (cAG), 6x5 min short arm centrifugation (iAG), or a control group (ctr, no countermeasures). Head-up tilt testing (15 min of 80°) followed by incremental lower body negative pressure (-10 mmHg every 3 min) until presyncope was performed before and at the end of HDTBR. Plasma volume was measured (CO rebreathing) 12-2 days before and after 56d of HDTBR. Stroke volume was measured by cMRI. Norepinephrine, epinephrine, aldosterone, and renine plasma levels were measured before and after HDTBR. Results: Time to presyncope decreased in all groups following bedrest (ctr: 22:56 min pre and 9:35 min post, cAG 15:34 min pre and 10:11 min post; iAG 14:56 min pre and 10:00 min post, p<0.001). The significant interaction (p=0.025) between bedrest and intervention was explained by greater baseline orthostatic tolerance time in the ctr. AG Data was pooled analysis. The reduction in stroke volume (ctr, pre: 93±19 ml, HDTBR: 69±13 ml, AG, pre: 88±20 ml, HDTBR: 67±17 ml) and plasma volume was similar (ctr, pre: 4155±1085 ml, HDTBR: 3855±1087 ml, AG, pre: 4114±1250 ml, HDTBR: 3674± 1313 ml). Catechols and aldosterone did not change significantly during bedrest. The increase in renine was similar between groups (ctr pre: 18±12 mE/L, HDTBR: 21±8 mE/L, AG pre: 21±10 mE/L, HDTBR: 31±12 mE/L). Conclusions: 30 min daily AG didn’t prevent a reduction in orthostatic tolerance following 60d HDTBR. Whether numerically smaller reductions in orthostatic tolerance in the AG groups indicate efficacy or result from baseline differences can’t be ascertained. A stronger AG stimulus or combination with other countermeasures might be required to maintain orthostatic tolerance and to attenuate the volume reduction.

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