The effect of pregnancy on the changes in hind‐limb vascular resistance following haemorrhage in the rabbit.

Humphreys, P. W.; Joels, N.

doi:10.1113/jphysiol.1986.sp015997

Cited by 3 publications

(1 citation statement)

References 14 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%

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%

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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Hemodynamic and hormonal responses to hemorrhage in conscious rabbits at mid- and late gestation

Brooks

Quesnell

Kane

et al. 1998

American Journal of Physiology-Regulatory, Integrative and Comp

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This study tests the hypothesis that conscious rabbits late in pregnancy (P), but not at midgestation (MP), are less able to maintain arterial pressure during hemorrhage. Blood volume (BV) was elevated ( P < 0.05) by an average of 13 ± 4 (MP) and 35 ± 3% (P). Rabbits were bled in both the nonpregnant (NP) and P state at 2% of the initial BV per minute. The hemorrhage was stopped after arterial pressure decreased. In NP rabbits, arterial pressure was well maintained near control pressures of 70 ± 2 mmHg until 38 ± 2% of the initial BV was removed and then rapidly fell to reach a nadir at 35 ± 2 mmHg. In contrast, in P rabbits, basal arterial pressure was lower (61 ± 2 mmHg; P < 0.05) and gradually decreased to below control after <25% of the initial BV was removed. Moreover, the rapid hypotensive phase was triggered with a lower percent BV removal (33 ± 2%; P < 0.05). Basal heart rate was higher during P (149 ± 5 vs. 189 ± 9 beats/min; P < 0.05), and reflex increases were delayed. The slope of the relationship between arterial pressure and vasopressin was not modified during P, although the line was shifted to a lower pressure ( P < 0.05). Larger increases in plasma renin activity and ANG II concentration were produced during hemorrhage in P rabbits. In contrast, no differences in the changes in arterial pressure, heart rate, and vasopressin were found between NP and MP rabbits during hemorrhage, although increases in renin and ANG II were greater at MP ( P < 0.05). In summary, although P conscious rabbits are less able to maintain blood pressure during hemorrhage, this change is not evident at MP. These data suggest that the factors that mediate the P-induced alterations in arterial pressure regulation are not operative until late in gestation.

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Regional conductance changes during hemorrhage in pregnant and nonpregnant conscious rabbits

Brooks

Kane

Welch

1999

American Journal of Physiology-Regulatory, Integrative and Comp

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Late pregnant (P) conscious rabbits are less able to maintain arterial pressure during hemorrhage than nonpregnant (NP) animals. This study tested the hypothesis that the difference is due in part to less reflex vasoconstriction when the rabbits are P. Rabbits ( n = 14) were instrumented with arterial and venous catheters as well as ultrasonic flow probes around the superior mesenteric, renal, and/or terminal aortic arteries. Pregnancy increased ( P < 0.05) blood volume [235 ± 5 (P) vs. 171 ± 3 (NP) ml], terminal aortic conductance [1.88 ± 0.11 (P) vs. 0.98 ± 0.06 (NP) ml ⋅ min−1 ⋅ mmHg−1], mesenteric conductance [1.20 ± 0.19 (P) vs. 0.80 ± 0.05 (NP) ml ⋅ min−1 ⋅ mmHg−1], and heart rate [191 ± 4 (P) vs. 162 ± 3 (NP) beats/min] and decreased arterial pressure [59 ± 1 (P) vs. 67 ± 2 (NP) mmHg; P < 0.05]. Renal conductance was unaltered. The rabbits were bled in both the NP and P states at 2% of the initial blood volume per minute until arterial pressure fell below 45 mmHg. Arterial pressure fell with less blood loss in P rabbits [28 ± 2% (P) vs. 39 ± 2% (NP) of initial blood volume; P < 0.001]. Terminal aortic conductance decreased ( P < 0.001) before the pressure fall in both groups, but the response was reduced in P rabbits. Mesenteric and renal conductances did not change in either group before the blood pressure fall. During the pressure fall, terminal aortic conductance increased ( P < 0.05) only in NP rabbits. Mesenteric conductance increased in both groups. In summary, rabbits in late gestation are less able to maintain arterial pressure during hemorrhage, at least in part because of reduced vasoconstriction in tissues perfused by the terminal aorta.

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The effect of pregnancy on the changes in hind‐limb vascular resistance following haemorrhage in the rabbit.

Cited by 3 publications

References 14 publications

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Hemodynamic and hormonal responses to hemorrhage in conscious rabbits at mid- and late gestation

Regional conductance changes during hemorrhage in pregnant and nonpregnant conscious rabbits

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