The effects of haemorrhage in the unanaesthetized rabbit

Chalmers, John; Korner, Paul I.; White, Saxon William

doi:10.1113/jphysiol.1967.sp008174

Cited by 49 publications

(35 citation statements)

References 37 publications

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“…Because pretreatment of animals with ␤-blockers to eliminate sympathetic influences on the heart does not significantly modify the hemodynamic responses to hemorrhage, it appears that reflex increases in heart rate or cardiac contractility are not required for cardiac output and arterial pressure maintenance (12,17,20). Instead, relative maintenance of preload, due primarily to decreases in venous capacity, may limit decreases in cardiac output despite decreases in blood volume (7,17).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, immediate and more profound decreases in stroke volume were observed. Given the evidence that cardiac output maintenance is mediated by decreases in venous capacity (7,17), the greater falls in cardiac output and stroke volume may be due to an attenuation of reflex increases in sympathetic activity to veins and therefore less venoconstriction. Another possible factor is the rate of fluid movement from the interstitium to the vascular compartment.…”

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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“…The incision was closed and the rabbit returned to the animal house for a 2 week recovery period. Following this recovery period the rabbits were subjected to a second operation (same induction and anaesthesia as above) which involved a sinoaortic denervation (SAD) or sham denervation (Chalmers, Korner & White, 1967) and installation of an inferior vena cava (IVC) 'bleed' cannula. The IVC cannula was filled with a mixture of 10% (Macrodex-70) dextran saline containing heparin and the end of the cannula was tunnelled subcutaneously and buried in the mid-iliac region.…”

Section: Animals and Operation8mentioning

confidence: 99%

Neurohumoral mechanisms and the role of arterial baroreceptors in the reno‐vascular response to haemorrhage in rabbits.

Courneya

Korner

1991

The Journal of Physiology

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SUMMARY1. Conscious rabbits, with implanted renal artery Doppler flow probes were bled at a constant rate (4 ml min-'). We assessed the contribution of autonomic, hormonal and local factors to the renal vasoconstrictor response to 20 % loss of blood volume (BV) and the role of the sinoaortic baroreceptors in the neurohumoral response.2. With intact autonomic effectors, 20 % BV loss was associated with a small fall in vascular conductance, which was completely unaffected by inhibition or blockade of the combined effects of the two major pressor hormones angiotensin II (All) and arginine vasopressin (AVP). Combined blockade of the autonomic effects plus those of the two pressor hormones resulted in marked elevation of vascular conductance, considered to be due to the local effects of haemorrhage. This response provided the baseline for assessing the constrictor response in the intact animal which, during 20% BV loss, was entirely due to reflex activity through the sympatho-adrenal system.3. In contrast to the early phase of haemorrhage (< 20% BV removal) both hormones played a role in the maintenance of mean arterial pressure immediately after haemorrhage and in the maintenance of renal vascular tone. This suggested that the contribution by hormones occurs only after more pronounced blood loss and hypotension.4. In the presence of autonomic blockade with mecamylamine plus methscopolamine (plus a constant infusion of noradrenaline to maintain resting blood pressure) the renal vasoconstrictor response was similar to that of the intact animal. We have previously found that this regime is associated with greatly enhanced release of AVP and plasma renin activity. Sinoaortic denervation had no effect on this hormonally mediated vasoconstriction.5. When the autonomic nervous system was intact but the effects of All and AVP were blocked to prevent the accentuated hormonally mediated vasoconstriction, sinoaortic denervation completely abolished the normal autonomic renal constrictor response, which is thus largely under control of the arterial baroreceptors.

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“…In the present study, coronary occlusion was performed to produce hypotension during only 1 min. Even in hemorrhagic shock, sympathetic nerve activity was reduced by prolonged hypotension due to hemorrhage (CHALMERS et al, 1967;CHIEN, 1967;GOOTMAN and COHEN, 1970 …”

Section: Discussionmentioning

confidence: 99%

“…Thus, further experiments are required to evaluate the net autonomic response to cardiogenic hypotension determining the central interactions of input from cardiac sympathetic afferents and from arterial baroreceptors and cardiac vagal afferents, and to determine more exact interaction with impaired cardiac function and cardiac sympathetic afferents during the hypotension induced by coronary occlusion. The role of the sympathetic nerves in the hypotensive response to hemorrhage has been well documented; the reduction of mean blood pressure due to hemorrhage in animals with neuraxis intact causes to reduce the afferent impulses from the arterial baroreceptors (CHALMERS et al, 1967;HEYMAN and NEIL, 1958;NEIL, 1962;NINOMIYA et a1.,1971) resulting in activation of the efferent sympathetic nerve activity to the heart and the peripheral blood vessels (CHIEN, 1967;NEIL, 1962;NINOMIYA et al, 1971). Thus, the removal of baroreceptors produced a precipitous fall in arterial pressure after hemorrhage (CHALMERS et al, 1967;CHIEN, 1967;DONALD and SHEPHERD, 1978) and even in orthostatic stress (KOYAMA et al, 1981).…”

Section: Discussionmentioning

confidence: 99%

Neural control of sympathetic nerve response to cardiogenic hypotension in anesthetized cat.

Koyama

1985

Jpn.J.Physiol

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The present study was designed to determine effect of the preganglionic splanchnic nerve activity (SNA) on the brief hypotension accompanied with the occlusion of left circumflex coronary artery (CxCAO) in chloralose anesthetized cats. Following CxCAO in animals with neuraxis intact, no significant alterations of SNA occurred despite the significant fall in mean blood pressure (MBP). A significant fall in MBP also occurred in vagotomized animals with arterial baroreceptors intact, but SNA was significantly augmented from 12.9±2.7 impulses/sec before CxCAO to 24.4±4.3 impulses/sec 60 sec after the occlusion. In vagotomized animals, in which their carotid sinuses were isolated and perfused with the constant pressure at a level equal to systemic blood pressure (112±6 mmHg) and with higher pressure (167±7 mmHg), SNA was not altered significantly during the hypotension due to CxCAO. When the carotid sinuses were perfused with lower pressure (53±8 mmHg), a significant increase in SNA occurred simultaneously with the decrease in MBP after CxCAO. The peak decreases in blood pressure during the coronary occlusion were significantly greater in the vagotomized group (-46±5 mmHg) and in the Low-CSP group (-50 ± 5 mmHg) than in other groups. Onset of this excitatory efferent sympathetic response to the hypotension due to the coronary occlusion in the vagotomized and Low-CSP groups was delayed significantly despite a significant fall in arterial blood pressure. These results show that vagal afferents from the heart may play a role of inhibiting the sympathetic augmentation mediated by arterial baroreceptors during cardiogenic hypotension. An excessive activation of cardiac receptors with sympathetic afferents may be induced by the profound fall in blood pressure, resulting in further impairment of cardiac function due to progressive myocardial ischemia under the condition of high sympathetic tone activated by baroreceptor reflex.

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The effects of haemorrhage in the unanaesthetized rabbit

Cited by 49 publications

References 37 publications

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Neurohumoral mechanisms and the role of arterial baroreceptors in the reno‐vascular response to haemorrhage in rabbits.

Neural control of sympathetic nerve response to cardiogenic hypotension in anesthetized cat.

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