Arterial pressure maintenance after haemorrhage in the pregnant rabbit.

Humphreys, P. W.; Joels, N.

doi:10.1113/jphysiol.1985.sp015782

Cited by 14 publications

(5 citation statements)

References 12 publications

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“…Nevertheless, they noted that after hemorrhage, the pregnant animals exhibited greater hypotension due to a greater fall in TPR and hindquarter resistance; the cardiac output responses were similar (14,15). Further work (13) revealed that the response of the femoral vascular bed to stimulation of the sympathetic nerves was similar between pregnant and nonpregnant rabbits, indirectly implying that the smaller degree of vasconstriction in the femoral bed observed in the present study was due to a smaller increase in sympathetic activity rather than decreased vascular responsiveness.…”

Section: Discussionmentioning

confidence: 99%

“…Humphreys and Joels (14) investigated the effect of pregnancy on the hemodynamic response to hemorrhage, but two aspects of their experimental approach markedly reduced the duration, and therefore the study, of the first phase: first, the rabbits were anesthetized, which markedly attenuates reflex increases in sympathetic activity during the initial phase of hemorrhage (19), and second, blood loss proceeded very rapidly. Nevertheless, they noted that after hemorrhage, the pregnant animals exhibited greater hypotension due to a greater fall in TPR and hindquarter resistance; the cardiac output responses were similar (14,15).…”

Section: Discussionmentioning

confidence: 99%

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Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Clow¹,

Giraud

Ogden

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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Pregnant animals are less able to maintain mean arterial pressure (MAP) during hemorrhage compared with nonpregnant animals, but the hemodynamic basis of this difference is unknown. The hypothesis that pregnancy attenuates responses of cardiac output, as well as total peripheral resistance (TPR) and femoral conductance, to hemorrhage was tested in conscious rabbits in both the pregnant and nonpregnant state ( n = 10). During continuous slow blood loss (2% of the initial blood volume per minute), MAP was maintained initially in both groups. However, MAP then abruptly decreased to <45 mmHg in all animals after a smaller percentage of the initial blood volume was removed in pregnant compared with nonpregnant rabbits (43.6 ± 1.7%, nonpregnant; 29.6 ± 2.2%, pregnant; P < 0.005). The more rapid transition to hypotension exhibited by pregnant rabbits was associated with greater initial falls in cardiac output (−56 ± 10 ml/min, nonpregnant; −216 ± 33 ml/min, pregnant; P < 0.005) and stroke volume (0.8 ± 0.1 ml/beat, nonpregnant; −1.3 ± 0.1 ml/beat, pregnant; P < 0.05). In addition, the increase in TPR as a function of the decrease in cardiac output was markedly attenuated ( P < 0.0001) during pregnancy. Whereas femoral conductance decreased in nonpregnant rabbits, it did not change significantly in pregnant animals. In conclusion, the lesser ability of conscious pregnant rabbits to maintain MAP during hemorrhage is due largely to a greater decrease in cardiac output but also to inadequate reflex increases in TPR, possibly in part in the femoral vascular bed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Clow¹,

Giraud

Ogden

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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show abstract

“…As a consequence, pregnant individuals exhibit an increased incidence of orthostatic hypotension 4 and a reduced ability to maintain arterial pressure during hemorrhage 5–7. Despite the fact that peripartum hemorrhage is a major cause of maternal death 8;9, the mechanisms by which pregnancy causes baroreflex dysfunction remain unclear.…”

Section: Introductionmentioning

confidence: 99%

Impaired Baroreflex Gain During Pregnancy in Conscious Rats

Azar

Brooks

2011

Hypertension

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Abstract-Pregnancy impairs baroreflex gain, but the mechanism is incompletely understood. To test the hypothesis that reductions in brain insulin contribute, we determined whether pregnant rats exhibit lower cerebrospinal fluid (CSF) insulin concentrations and whether intracerebroventricular infusion of insulin normalizes gain of baroreflex control of heart rate in conscious pregnant rats. CSF insulin was lower in pregnant (68Ϯ21 pg/mL) compared to virgin (169Ϯ25 pg/mL) rats (PϽ0.05

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“…Pregnant women are prone to orthostatic hypotension, due to blunted reflex activation of the sympathetic nervous system and inadequate peripheral vasoconstriction (56,122,132). Moreover, in many species, pregnancy interferes with the normal ability to maintain arterial pressure during hemorrhage (26,36,99,152,186). Hemodynamic studies have revealed that in pregnant animals, arterial pressure falls with less blood loss due to both a failure to maintain cardiac output and also inadequate peripheral vasoconstriction (22,36).…”

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confidence: 99%

Pregnancy and the endocrine regulation of the baroreceptor reflex

Brooks

Dampney

Heesch

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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-The purpose of this review is to delineate the general features of endocrine regulation of the baroreceptor reflex, as well as specific contributions during pregnancy. In contrast to the programmed changes in baroreflex function that occur in situations initiated by central command (e.g., exercise or stress), the complex endocrine milieu often associated with physiological and pathophysiological states can influence the central baroreflex neuronal circuitry via multiple sites and mechanisms, thereby producing varied changes in baroreflex function. During pregnancy, baroreflex gain is markedly attenuated, and at least two hormonal mechanisms contribute, each at different brain sites: increased levels of the neurosteroid 3␣-hydroxydihydroprogesterone (3␣-OH-DHP), acting in the rostral ventrolateral medulla (RVLM), and reduced actions of insulin in the forebrain. 3␣-OH-DHP appears to potentiate baroreflex-independent GABAergic inhibition of premotor neurons in the RVLM, which decreases the range of sympathetic nerve activity that can be elicited by changes in arterial pressure. In contrast, reductions in the levels or actions of insulin in the brain blunt baroreflex efferent responses to increments or decrements in arterial pressure. Although plasma levels of angiotensin II are increased in pregnancy, this is not responsible for the reduction in baroreflex gain, although it may contribute to the increased level of sympathetic nerve activity in this condition. How these different hormonal effects are integrated within the brain, as well as possible interactions with additional potential neuromodulators that influence baroreflex function during pregnancy and other physiological and pathophysiological states, remains to be clearly delineated.3␣-hydroxy-dihydroprogesterone; angiotensin II; insulin; paraventricular nucleus of the hypothalamus NORMAL PREGNANCY is characterized by profound changes in fluid and electrolyte balance and blood pressure regulation. Blood volume and cardiac output increase by 30 -50%, but arterial pressure falls due to even greater decreases in systemic vascular resistance (120,138,189). These hemodynamic alterations are evident early in pregnancy, precede the increases in uterine blood flow, and are sustained until parturition (127,138,189). Considerable data implicate increases in relaxin and nitric oxide (NO) in the systemic vasodilation induced by pregnancy (20,127,128,177,196). In addition, peripheral vascular sensitivity to circulating vasoconstrictors including vasopressin, angiotensin II (ANG II), and norepinephrine (NE) is decreased (50,71,154).Unlike the hemodynamic changes, which likely subserve adequate fetal development, an adverse consequence of normal pregnancy is a marked impairment of the arterial baroreceptor reflex. This change was first noted by Humphreys and Joels (97,98) in an extensive series of studies in anesthetized pregnant rabbits, in which reductions in carotid sinus pressure failed to elicit normal increases in arterial pressure and peripheral vascular resistanc...

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Arterial pressure maintenance after haemorrhage in the pregnant rabbit.

Cited by 14 publications

References 12 publications

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Impaired Baroreflex Gain During Pregnancy in Conscious Rats

Pregnancy and the endocrine regulation of the baroreceptor reflex

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