Reductions in central venous pressure improve carotid baroreflex responses in conscious men

Pawelczyk, James A.; Raven, Peter B.

doi:10.1152/ajpheart.1989.257.5.h1389

Cited by 102 publications

(146 citation statements)

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“…5 It has been suggested that this degree of plasma volume change could lead to increased baroreflex sensitivity. 9 In addition, estrogen and progesterone could indirectly alter baroreflex sensitivities by altering arterial distensibility, 10 thus changing the impact of pressure fluctuations on baroreceptor firing. Changes in baroreflex sensitivities may have occurred to maintain blood pressure in response to changes in other physiological systems during the course of the menstrual cycle or OC use.…”

Section: Discussionmentioning

confidence: 99%

Sympathetic Activity and Baroreflex Sensitivity in Young Women Taking Oral Contraceptives

Minson¹,

Halliwill²,

Young³

et al. 2000

Circulation

117

129

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Background-We tested sympathetic and cardiovagal baroreflex sensitivity during the placebo or "low-hormone" phase (LH) and 2 to 3 weeks later during the "high-hormone" phase (HH) of oral contraceptive (OC) use in 9 women. Methods and Results-Sympathetic baroreflex sensitivity was assessed by intravenous doses of sodium nitroprusside and phenylephrine and defined as the slope relating muscle sympathetic nerve activity (by microneurography) and diastolic blood pressure. Cardiovagal baroreflex sensitivity was defined as the slope relating R-R interval and systolic blood pressure. No difference was observed for resting muscle sympathetic nerve activity or plasma norepinephrine levels. However, sympathetic baroreflex sensitivity was greater and mean arterial pressure was higher during the LH than in the HH phase. Similarly, cardiovagal baroreflex sensitivity was greater in the LH than in the HH phase. Conclusions-Sympathetic and cardiovagal baroreflex sensitivities change during the 28-day course of OC use.Furthermore, changes in baroreflex sensitivity with OC differ from changes in baroreflex sensitivity during the normal menstrual cycle. (Circulation. 2000;102:1473-1476.)Key Words: estrogens Ⅲ progesterone Ⅲ blood pressure Ⅲ nervous system, autonomic W e recently reported that blood pressure regulation by the sympathetic nervous system changes during the menstrual cycle. 1 Resting muscle sympathetic nerve activity (MSNA) and sympathetic baroreflex sensitivity, but not cardiovagal baroreflex sensitivity, were greater during the midluteal (high hormone) phase compared with the early follicular (low hormone) phase of the menstrual cycle.Our goal in the present study was to extend these observations to women taking oral contraceptives (OC). We compared resting MSNA, sympathetic baroreflex sensitivity, and cardiovagal baroreflex sensitivity in young women during the placebo or "low hormone" (LH) phase of OC use and during the active OC phase ("high hormone"; HH). We hypothesized that our results would parallel our previous findings, ie, resting MSNA and sympathetic baroreflex sensitivity would be greater when women were taking exogenous estrogen and progestin than when taking the placebo. Methods SubjectsThe Institutional Review Board approved all procedures. Nine women were recruited and gave written informed consent. Subjects were young (30Ϯ2 years), healthy (body mass index, 24.2Ϯ1.0 kg/m 2 ) nonsmokers who had not taken medications except monophasic OC, which provided 30 to 35 g of ethinyl estrogen and low-dose progestin for 21 days and placebo for 7 days. Experimental ProtocolSubjects were studied twice, once during the LH phase (4 to 5 days after starting placebo pill, 3 to 6 days after onset of menstruation) and once during the HH phase of OC use (17 to 20 days after starting the ethinyl estrogen-progestin pills). The order of testing was counterbalanced.Subjects were placed in the supine position, and a catheter was placed in an antecubital vein for drug injections. Heart rate was determined from an ECG, and bea...

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Section: Discussionmentioning

confidence: 99%

Sympathetic Activity and Baroreflex Sensitivity in Young Women Taking Oral Contraceptives

Minson¹,

Halliwill²,

Young³

et al. 2000

Circulation

117

129

View full text Add to dashboard Cite

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“…Also, some reports have suggested that the sensitivity of the arterial HR baroreceptor reflex may be increased with decreases in central venous pressure. 12 However, other studies have failed to demonstrate similar changes. 51314 Frequency domain analyses have been applied extensively over the last 10 years to the study of HR control.…”

Section: -3mentioning

confidence: 99%

Mild hypovolemic stress alters autonomic modulation of heart rate.

1993

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In response to changes in central venous volume, changes in vagal efferent cardiac outflow have been demonstrated in animals but not in humans. In this study, frequency domain analysis was used to quantify modulation of heart rate by respiration and blood pressure in normal human adults undergoing mild central hypovolemic stress induced by blood donation and postural change. In supine subjects, blood donation caused no change in mean heart rate, pulse pressure, or in the variance of heart rate or blood pressure. There were small decreases in mean and systolic blood pressures. A significant decrease in vagal modulation of heart rate was seen in the 0.12-0.5-Hz frequency band, as measured by the change in the relation of lung volume to heart rate in this frequency band (-4.49 beats per minute [bpm] per liter [I], p<0.001). Comparison of supine and tilt positions revealed marked changes in heart rate and blood pressure means and variances consistent with more pronounced decreases in intracardiac filling pressures and unloading of the arterial baroreceptors. A further progressive decrease in the vagal modulation of heart rate by lung volume was observed in the 0.12-0.5-Hz band, with a near-linear response of magnitude of respiratory sinus arrhythmia over a range of estimated central venous volume. Transfer function analysis can detect changes in autonomic response to mild degrees of central hypovolemia, which are insufficient to cause changes in mean heart rate or heart rate variance. This represents evidence for modulation of heart rate control by cardiopulmonary baroreceptors. A near-linear relation between magnitude of respiratory sinus arrhythmia and central venous volume suggests that this may have clinical relevance in patient monitoring. (Hypertension 1993;21:236-247) KEY WORDS • autonomic nervous system • pressoreceptors • hemorrhage • heart rate

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“…The prolonged BP elevation is otherwise explained by a compensatory mechanism other than the arterial baroreflex, such as the cardiopulmonary baroreflex [6,7] or vestibulosympathetic reflex [8]. It is generally accepted that, in a prolonged stage ([2 min) of orthostasis, BP maintenance is supported by humoral factors [4,5].…”

Section: Other Compensatory Mechanismsmentioning

confidence: 99%

“…This blood shift then reduces the venous return, so that the cardiac output and blood pressure (BP) tend to decline. This BP reduction, however, is compensated partly by various reflex mechanisms including arterial baroreflex [4,5], cardiopulmonary reflex [6,7], vestibulosympathetic reflex [8], or venoarteriolar axon reflex [9], and thus BP is maintained during an upright posture. Improvement in orthostatic tolerance is achieved by improving orthostatic cardiovascular responses [10].…”

Section: Introductionmentioning

confidence: 99%

Arterial blood pressure response to head-up tilt test and orthostatic tolerance in nurses

Onizuka

Niimi²,

Sato

et al. 2015

Environ Health Prev Med

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Objectives High tolerance to postural changes was examined in nurses. Methods Twelve female nurses and 12 healthy controls underwent a 70°head-up tilt (HUT) test for 10 min. Blood pressure (BP), heart rate (HR), pulse pressure, and hormone levels were measured. Baroreceptor sensitivity (BRS) was calculated using a sequence technique. Results HR increased during HUT in both subject groups, with no difference between groups. Systolic BP was rapidly increased by HUT in both subject groups, and was higher in the nurse group than in the control group during the first 2 min of HUT. Pulse pressure decreased during 1-2.5 min of HUT in the control group, but there was no decrease in the nurse group. BRS was decreased by HUT in the nurse group, while it tended to be decreased in the control group. Both during baseline and HUT, BRS was lower in the nurse group than in the control group. Plasma noradrenaline increased with HUT, and the increase was greater in the nurse group than in the control group. Conclusions Although nurse subjects had a lower BRS during HUT than control subjects, they were able to effectively maintain BP during HUT, suggesting that nurse subjects had higher orthostatic tolerance. The better maintenance of BP in nurse subjects appeared to be associated with a compensatory mechanism other than the arterial baroreflex and/or a hemodynamic mechanism.

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Reductions in central venous pressure improve carotid baroreflex responses in conscious men

Cited by 102 publications

References 0 publications

Sympathetic Activity and Baroreflex Sensitivity in Young Women Taking Oral Contraceptives

Sympathetic Activity and Baroreflex Sensitivity in Young Women Taking Oral Contraceptives

Mild hypovolemic stress alters autonomic modulation of heart rate.

Arterial blood pressure response to head-up tilt test and orthostatic tolerance in nurses

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