Absence of fetal placental waterfall phenomenon in chronically prepared fetal lambs

1976 ◽  
Vol 230 (4) ◽  
pp. 886-892 ◽  
Author(s):  
KL Thornburg ◽  
JM Bissonnette ◽  
JJ Faber
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Arterial Blood Pressure ◽  
Umbilical Vein ◽  
Venous Pressure ◽  
Amniotic Cavity ◽  
Umbilical Blood ◽  
Arterial Blood ◽  
Placental Blood ◽  
Umbilical Blood Flow

An electromagnetic flow sensor was placed on the distal fetal aorta (umbilical flow fraction 78.1 +/- 1.6 SEM, %), an inflatable occluder was tied around the umbilical cord, and catheters were placed in distal branches of an umbilical artery and vein, a uterine vein, and in the amniotic cavity. An inflatalbe occluder was tied around the vagina of some of the ewes. Control values 3 days after surgery were (mean +/- SE): fetal femoral artery pH, 7.37 +/- 0.01; umbilical blood flow, 186 +/- 14 ml-min-1 .kg fetus-1; fetal arterial blood pressure, 39 +/- 3 mmHg; and umbilical venous pressure, 7.4 +/- 1.0 mmHg (above intrauterine pressure). Fetal weight at autopsy was 3.1 +/- 0.3 kg, n = 11. Small increases in umbilical vein pressure caused immediate decreases in placental blood flow without decreases in fetal arterial blood pressure. The relation between venous pressure and umbilical blood flow at constant arterial pressure was that of an inert system, i.e., no evidence of a surrounding pressure (Starling resistor effect or waterfall phenomenon) could be found with increases in venous pressures of 2-40 mmHg. The results were not affected by increases in uterine vein pressure between 2 and 30 mmHg, nor by anesthesia and supine position of the ewe, nor by ganglionic blockade of the fetal ANS. It was concluded that surrounding pressures in the fetal placental circulation could not be demonstrated.

Regulation of fetal placental blood flow in the lamb

1984 ◽  
Vol 247 (3) ◽  
pp. R567-R574 ◽  
Author(s):  
D. F. Anderson ◽  
J. J. Faber
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Arterial Blood Pressure ◽  
Fetal Growth ◽  
Control Value ◽  
Flow Restriction ◽  
Arterial Blood ◽  
Placental Blood ◽  
Carotid Arterial ◽  
Placental Blood Flow

Inflatable occluders were placed on the distal aorta of 11 fetal lambs. After 1 wk of control measurements, fetal placental blood flow was reduced to about two-thirds of its control value for an average period of 2 wk. No allowance was made for fetal growth. During the period of flow restriction, fetal growth was 2%/day. Femoral arterial blood pressure was reduced from a control value of 41 to 27 mmHg (P less than 0.001). There was an insignificant increase in carotid arterial blood pressure from 48 to 50 mmHg. Placental resistance to flow did not decrease more than could be accounted for by the increase in gestational age in the course of the experiment. It is concluded that fetal placental blood flow is not under feedback control, since neither of the determinants of flow (i.e., driving pressure and resistance) responded to its chronic reduction.

The Effect of Vibration on Blood Flow in Skeletal Muscle in the Rabbit

1978 ◽  
Vol 55 (5) ◽  
pp. 471-476 ◽  
Author(s):  
O. Hudlická ◽  
A. Wright
Keyword(s):  
Blood Pressure ◽  
Skeletal Muscle ◽  
Blood Flow ◽  
Arterial Blood Pressure ◽  
Perfusion Pressure ◽  
Venous Pressure ◽  
Arterial Blood ◽  
Resistance Vessels ◽  
Denervated Muscles ◽  
Initial Blood

1. The blood flow in rabbit gastrocnemius, as measured by photoelectric drop-counter, increased when the muscle was vibrated at frequencies of 22–62 Hz. 2. Blood flow increased rapidly within 1–2 s of the start of vibration, and lasted for the whole time vibration was applied. 3. The increase in blood flow was negatively correlated with the initial blood flow, being greater with lower flows. 4. The magnitude of increase was similar in both innervated and acutely denervated muscles. 5. The arterial blood pressure did not change apart from a very brief fall at the beginning of vibration. Venous pressure rose and, consequently, the perfusion pressure was lower. The increase in blood flow thus indicates a considerable dilatation in the resistance vessels of skeletal muscle.

Regulation of arterial blood pressure in the common green iguana

1975 ◽  
Vol 228 (2) ◽  
pp. 386-391 ◽  
Author(s):  
LA Hohnke
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Arterial Pressure ◽  
Arterial Blood Pressure ◽  
Venous Pressure ◽  
Arterial Blood Flow ◽  
Arterial Blood ◽  
Head Up Tilt ◽  
Carotid Arterial

Arterial blood pressure (ABP) responses to graded hemorrhage and passive head-up tilt were studied in restrained, anesthetized, and unanesthetized iguanas. The ABP fell slowly in response to hemorrhage up to a critical deficit of 35 plus or minus 19% of the estimated blood volume; the rate of ABP fall then increased nearly 40-fold to continued hemorrhage. Increased heart rate and decreased femoral arterial blood flow accompanied progressive hemorrhage. Propranolol (2-3 mug/kg) did not appreciably alter arterial pressure-hemorrhage curves but hemorrhage-induced increases in heart rate were diminished nearly 50%. Atropine had little effect on either the blood pressure or heart rate changes induced by hemorrhage. During passive tilts of 0-90 degrees carotid arterial pressure fell 33% before returning to control levels (2 min). Heart rate increased and femoral arterial blood flow and central venous pressure fell in response to head-up tilts. It is concluded that hemorrhage and passive head-up tilting can induce reflex cardiovascular changes that assist ABP regulation in iguanas.

Hepatic vascular response to norepinephrine

1962 ◽  
Vol 202 (6) ◽  
pp. 1175-1178 ◽  
Author(s):  
L. Newton Turk ◽  
William C. Shoemaker
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Pressure Gradient ◽  
Arterial Blood Pressure ◽  
Hepatic Blood Flow ◽  
Venous Pressure ◽  
Hepatic Venous Pressure Gradient ◽  
Portal Venous Pressure ◽  
Arterial Blood ◽  
Venous Resistance

Norepinephrine injected into the femoral vein or inferior vena cava in doses ranging from 1 to 10 µg/kg produced a prompt and definite decrease in hepatic blood flow; this response was, in general, more pronounced with increasing doses. Femoral venous injections also produced a prompt increase in arterial blood pressure followed by a decreased portal venous pressure and portal-hepatic venous pressure gradient. The calculated hepatic venous resistance increased, reaching a maximum at about 60 sec after injection. When the identical doses were injected into the portal vein in the same animals under comparable conditions, the arterial blood pressure and hepatic blood flow responses were delayed in time and attenuated in amount. However, within 10–15 sec of injection the portal venous pressure and portal-hepatic venous pressure gradient increased. The calculated hepatic venous resistance increased more rapidly after intraportal norepinephrine injection.

The relationship of blood flow velocity fluctuations to intracranial pressure B waves

1992 ◽  
Vol 76 (3) ◽  
pp. 415-421 ◽  
Author(s):  
David W. Newell ◽  
Rune Aaslid ◽  
Renate Stooss ◽  
Hans J. Reulen
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Intracranial Pressure ◽  
Arterial Blood Pressure ◽  
Wave Amplitude ◽  
Transcranial Doppler Ultrasound ◽  
Normal Subjects ◽  
Content Type ◽  
Arterial Blood ◽  
Flow Fluctuations

✓ Intracranial pressure (ICP) and continuous transcranial Doppler ultrasound signals were monitored in 20 head-injured patients and simultaneous synchronous fluctuations of middle cerebral artery (MCA) velocity and B waves of the ICP were observed. Continuous simultaneous monitoring of MCA velocity, ICP, arterial blood pressure, and expired CO2 revealed that both velocity waves and B waves occurred despite a constant CO2 concentration in ventilated patients and were usually not accompanied by fluctuations in the arterial blood pressure. Additional recordings from the extracranial carotid artery during the ICP B waves revealed similar synchronous fluctuations in the velocity of this artery, strongly supporting the hypothesis that blood flow fluctuations produce the velocity waves. The ratio between ICP wave amplitude and velocity wave amplitude was highly correlated to the ICP (r = 0.81, p < 0.001). Velocity waves of similar characteristics and frequency, but usually of shorter duration, were observed in seven of 10 normal subjects in whom MCA velocity was recorded for 1 hour. The findings in this report strongly suggest that B waves in the ICP are a secondary effect of vasomotor waves, producing cerebral blood flow fluctuations that become amplified in the ICP tracing, in states of reduced intracranial compliance.

Forearm and finger blood flow responses to passive body tilts

1979 ◽  
Vol 46 (2) ◽  
pp. 288-292 ◽  
Author(s):  
Y. A. Mengesha ◽  
G. H. Bell
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Arterial Blood Pressure ◽  
Vascular Resistance ◽  
Pulse Rate ◽  
Forearm Blood Flow ◽  
Body Tilt ◽  
Finger Blood Flow ◽  
Arterial Blood ◽  
Forearm Vascular Resistance

Ten to fifteen healthy subjects, ages 18--30 yr, were used to assess the correlation of forearm blood flow with graded passive body tilts and vascular resistance and also to discern the relative effects of body tilts on finger blood flow. In the head-up tilts forearm blood flow and arterial blood pressure fell progressively, whereas forearm vascular resistance and pulse rate increased. In the head-down tilts the forearm blood flow and the arterial blood pressure increased, whereas the forearm vascular resistance and pulse rate decreased. These changes were found to be significantly correlated with the different tilt angles and with one another. In a preliminary study it was found that infrared heating of the carpometacarpal region produced finger vasodilatation similar to the forearm vasodilatation observed by Crockford and Hellon (6). However, unlike forearm blood flow, finger blood flow showed no appreciable response to either the head-up or head-down tilts. This indicates that the sympathetic tone and the volume of blood in the finger are not appreciably altered by this test procedure at least 1 min after the body tilt is assumed.

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