Beta-blockade does not improve orthostatic intolerance induced by 20 days bed rest.
To assess if propranolol influences orthostatic intolerance induced by prolonged bed rest (BR), a lower body negative pressure test (LBNP) and left ventricular (LV) echocardiography before and during -40mmHg of LBNP were performed with and without intravenous propranolol administration (0.04mg/kg) in 9 healthy volunteers (mean age: 21 years) before and after 20 days BR. LBNP tolerance time (LBNP-T), endpoint heart rate(HR), and percentage changes from 0 to -40mmHg LBNP in HR, LV diastolic dimension(LVDd), stroke volume (SV), cardiac output (CO), and systemic vascular resistance(SVR) were measured. After BR, percentage changes in CO during LBNP was not altered by propranolol (-12+/-21% vs. -24+/-24%; with and without propranolol; p>0.05) because the effect on percentage changes in HR (18+/-11% vs. 26+/-12%; p<0.05) cancelled out the effects of percentage changes in LVDd (-9+/-6% vs. -15+/-10%; p<0.05) and percentage changes in SV (-26+/-16% vs. -39+/-22%; p<0.05). In addition, propranolol decreased end-point HR (85+/-15bpm vs. 119+/-l4bpm; p<0.05) and percentage changes in SVR (25+/-32% vs. 53+/-57%; p<0.05). As a result, LBNP-T after BR was unchanged by propranolol (8.8+/-3.3min vs. 10.8+/-5.0min; p>0.05). In conclusion, propranolol failed to change orthostatic intolerance induced by BR.
Takenaka
K
K
Department of Laboratory Medicine, University of Tokyo, Japan.
Suzuki
Y
Y
Kawakubo
K
K
Haruna
Y
Y
Kuriyama
K
K
Iwamoto
S
S
Igarashi
T
T
Watanabe
F
F
Omata
M
M
Bonde-Petersen
F
F
Sekiguchi
C
C
Murai
T
T
Miyamoto
A
A
Sudoh
M
M
Akimura
A
A
Gunji
A
A
Miyamotoi
A
A
Watanbe
F
F
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D000328:Adult; D001510:Bed Rest / Q000009:adverse effects*; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007024:Hypotension, Orthostatic / Q000188:drug therapy* / Q000209:etiology; D008150:Lower Body Negative Pressure; D008297:Male; D011433:Propranolol / Q000494:pharmacology / Q000627:therapeutic use*
D000319:Adrenergic beta-Antagonists; D011433:Propranolol