The effect of a low-dose infusion of ritodrine on cardiac output distribution and uteroplacental blood flow in unanaesthetized pregnant guinea pigs

1. Ten healthy volunteers received intravenous infusions of arginine vasopressin (AVP) at 0.1 m-unit min−1 kg−1 and 5% d-glucose on separate days. AVP caused a small fall in forearm blood flow and small rises in mean arterial pressure and systemic vascular resistance. Cardiac output was unaffected. 2. When subjects were tilted to 50° the fall in forearm blood flow was much greater, mean fall being 44.8% with AVP compared with 18.2% with d-glucose. Cardiac output also fell significantly more with AVP, and diastolic pressure, mean arterial pressure and systemic vascular resistance rose significantly more on tilting during AVP infusion than with d-glucose. 3. Six of the same volunteers were given sequential infusions of ‘low dose’ (0.0125 m-unit min−1 kg−1) and ‘high dose’ (0.3 m-unit min−1 kg−1) AVP on a third occasion. Tilting still produced a mean fall in forearm blood flow of 41.2% during low dose infusion, despite a mean plasma AVP level of only 1.9 pg/ml, which is well within the physiological range. When the AVP concentration was increased 24-fold to the high dose, forearm blood flow fell only a further 8.8%. The low dose infusion was also associated with a marked fall in cardiac output on tilting and a rise in systemic vascular resistance. 4. We conclude that AVP has profound haemodynamic effects in man at physiological concentrations. Although these effects are modest in the supine position, they become marked on tilting, suggesting a possible role for AVP in the postural control of blood pressure.

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Cardiac output distribution and regional blood flow during hypocarbia in monkeys

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.4.1225 ◽

1985 ◽

Vol 58 (4) ◽

pp. 1225-1230 ◽

Cited By ~ 6

Author(s):

S. Gelman ◽

K. C. Fowler ◽

S. P. Bishop ◽

L. R. Smith

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Regional Blood Flow ◽

Arterial Blood Flow ◽

Tissue Blood Flow ◽

Base Line ◽

Output Distribution ◽

Arterial Blood ◽

Cardiac Output Distribution ◽

The Brain

Cardiac output distribution and regional blood flow were studied during hypocarbia independent of changes in ventilatory parameters. Fifteen cynomolgus monkeys were anesthetized with methohexital sodium (8 mg/kg im) and hyperventilated through an endotracheal tube. Hypocarbia at two levels, 28 +/- 1.8 and 17 +/- 0.6 Torr, was achieved by a stepwise decreasing CO2 flow into the semiclosed system. Regional blood flow was determined with labeled microspheres. At each stage of experiments two sets of microspheres (9 and 15 microns diam) were used simultaneously. The use of two microsphere sizes allowed evaluation of the relationship between total (nutritive and nonnutritive) tissue blood flow, determined with 15-microns spheres, and nutritive blood flow, determined with 9-microns spheres. There was no change in cardiac output or arterial pressure during both degrees of studied hypocarbia. Hypocarbia was accompanied by a decrease in myocardial blood flow determined with 15-microns spheres and preservation of the flow determined with 9-microns spheres. Splenic blood flow was decreased, whereas hepatic arterial blood flow was increased during both levels of hypocarbia. Blood flow through the brain, renal cortex, and gut showed a biphasic response to hypocarbia: during hypocarbia at 28 +/- 1.8 Torr, blood flow determined with 15-microns spheres was unchanged (in the gut) or decreased (in the brain and kidneys), whereas blood flow determined with 9-microns spheres was decreased. During hypocarbia at 17 +/- 0.6 Torr, blood flow determined with 9-microns spheres had a tendency to restore to base-line values.

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Uteroplacental Blood Flow during Pregnancy in Chronically Catheterized Guinea Pigs

Pediatric Research ◽

10.1203/00006450-198209000-00003 ◽

1982 ◽

Vol 16 (9) ◽

pp. 716-720 ◽

Cited By ~ 15

Author(s):

L L H Peeters ◽

J W Sparks ◽

G Grutters ◽

J Girard ◽

F C Battaglia

Keyword(s):

Blood Flow ◽

Guinea Pigs ◽

Uteroplacental Blood Flow

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A longitudinal study of cardiac output in unstressed pregnant guinea pigs

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.248.6.r698 ◽

1985 ◽

Vol 248 (6) ◽

pp. R698-R701

Author(s):

S. A. Myers ◽

H. Y. Tseng

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Longitudinal Study ◽

Guinea Pigs ◽

Mammalian Species ◽

Single Observation ◽

Multiple Observations ◽

Placental Blood ◽

Significant Change ◽

Placental Blood Flow

A previous study in pregnant guinea pigs failed to demonstrate any increase in cardiac output when a group of pregnant animals was compared with four nonpregnant animals. In the current study an increase in cardiac output of 35 +/- 14 (SE) ml/min, a 13% increase, was observed during an average 2-wk interval between 44 and 58 days of pregnancy (P less than 0.05, term 68 days, n = 8). A significant increase in placental blood flow of 14.8 +/- 6.2 ml/min (42% increase, P less than 0.05) was also observed during this interval without significant change in the percentage of cardiac output going to the uterus. The data on cardiac output and its distribution to the uteroplacental circulations are consistent with reports in other mammalian species; to accommodate the increased demands of the uteroplacental circulation, cardiac output increases as pregnancy advances. These data demonstrate that multiple observations in the same animal describe cardiac output and its distribution more accurately than a single observation.

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