scholarly journals Cardiovascular adjustments to acute hypoxemia superimposed on chronic hypoxemia in lambs

1995 ◽  
Vol 268 (3) ◽  
pp. H974-H979
Author(s):  
M. Dalinghaus ◽  
J. W. Gratama ◽  
W. G. Zijlstra ◽  
J. R. Kuipers
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Oxygen Supply ◽  
Pulmonary Stenosis ◽  
Arterial Oxygen Saturation ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Blood Flows ◽  
Regional Blood Flows ◽  
Chronic Hypoxemia

Cardiovascular responses to acute hypoxemia are in part mediated through adrenergic and chemoreceptor stimulation. In chronic hypoxemia the response to these stimuli may be blunted. Therefore, we determined whether the cardiovascular responses to acute hypoxemia superimposed on 3–4 wk of chronic hypoxemia were blunted in lambs with an experimental cardiac right-to-left shunt (combination of atrial septal defect and variable pulmonary stenosis). Cardiovascular variables and regional blood flows were determined during chronic hypoxemia and after acutely reducing the arterial oxygen saturation by increasing the cardiac right-to-left shunt. Arterial oxygen saturation decreased (65 +/- 7 to 40 +/- 7%, P < 0.001) and systemic blood flow increased (164 +/- 63 to 233 +/- 100 ml.min-1.kg-1, P < 0.01), maintaining systemic oxygen supply and oxygen uptake. Blood flow to the myocardium (P < 0.01), the adrenals (P < 0.05), and the brain (0.05 < P < 0.10) increased, and oxygen supply to these organs was maintained. Conversely, blood flow to the kidneys and the gastrointestinal tract was unaltered, so that oxygen supply to these organs was decreased. The responses to acute hypoxemia in chronically hypoxemic lambs were similar to those previously reported in normoxemic lambs. We conclude that the cardiovascular responses to acute hypoxemia in chronically hypoxemic lambs are not blunted.

Effect of increased whole blood viscosity on regional blood flows in chronically hypoxemic lambs

1994 ◽  
Vol 267 (2) ◽  
pp. H471-H476
Author(s):  
M. Dalinghaus ◽  
H. Knoester ◽  
J. W. Gratama ◽  
J. Van der Meer ◽  
W. G. Zijlstra ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Oxygen Supply ◽  
Arterial Oxygen ◽  
Organ Blood Flow ◽  
Whole Blood Viscosity ◽  
Blood Flows ◽  
Chronic Hypoxemia

In chronic hypoxemia blood flow and oxygen supply to vital organs are maintained, but to nonvital organs they are decreased. We measured organ blood flows (microspheres) and whole blood viscosity in 10 chronically hypoxemic lambs, with an atrial septal defect and pulmonary stenosis, and in 8 control lambs. Vascular hindrance (resistance/viscosity) was calculated to determine to what extent the effect of increased blood viscosity on organ blood flow was compensated for by a decrease in vascular tone. Arterial oxygen saturation was decreased (68 +/- 10 vs. 91 +/- 3%, P < 0.001), and both hemoglobin concentration (145 +/- 10 vs. 109 +/- 9 g/l, P < 0.05) and blood viscosity (4.4 +/- 0.6 vs. 3.6 +/- 0.6 mPa.s, P < 0.05) were increased in hypoxemic lambs. Systemic blood flow, oxygen supply, oxygen uptake, and blood pressures were not significantly different between hypoxemic and control lambs. Myocardial and cerebral blood flow was maintained in hypoxemic lambs, whereas renal, gastrointestinal, splenic, and thyroidal blood flows were at least 30% lower. Vascular hindrance was significantly decreased in the myocardium and tended to be lower in the brain of hypoxemic lambs, but in all other organs it was similar to that in control lambs. It is concluded that blood flow is redistributed in chronic hypoxemia in lambs; myocardial and cerebral blood flow is maintained, whereas blood flow to splanchnic organs, the kidneys, and the thyroids is decreased. The decreased blood flow to organs is a consequence of the increased whole blood viscosity.

AN EFFECT OF REDUCED BAROMETRIC PRESSURE ON THE PERIPHERAL CIRCULATION

1957 ◽  
Vol 35 (10) ◽  
pp. 777-783
Author(s):  
F. Girling ◽  
F. A. Sunahara
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Forearm Blood Flow ◽  
Human Subjects ◽  
Arterial Oxygen Saturation ◽  
Barometric Pressure ◽  
Peripheral Circulation ◽  
Arterial Oxygen ◽  
Blood Flows ◽  
The Past

Several groups of investigators have noted in the past that exposure to a reduced barometric pressure results in a decrease in peripheral blood flow.In the present study human subjects were exposed to a pressure of 225 mm. Hg with maintenace of arterial oxygen saturation, and forearm and hand blood flows were measured plethysmographically. Forearm blood flow was not affected by the exposure whereas hand blood flow was reduced in all subjects. Blood pressure and heart rate were also measured and showed no change during the experiment.

Effects of hematocrit variations on regional hemodynamics and oxygen transport in the dog

1980 ◽  
Vol 238 (4) ◽  
pp. H545-H522 ◽  
Author(s):  
F. C. Fan ◽  
R. Y. Chen ◽  
G. B. Schuessler ◽  
S. Chien
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Blood Vessels ◽  
Oxygen Transport ◽  
Oxygen Supply ◽  
Blood Flows ◽  
Regional Hemodynamics ◽  
Regional Blood Flows ◽  
Splenic Vessels ◽  
The Brain

The responses of alterations in regional hemodynamics and oxygen transport rate to hematocrit (Hct) were studied in 20 pentobarbitalized dogs. Hemodilution was carried out by isovolemic exchange with plasma in 12 dogs and the hemoconcentration with packed cells in 8 dogs. The cardiac output and regional blood flows were determined with the microsphere technique. In hemodilution, the increases of blood flow to the myocardium and the brain were out of proportion to the increase of cardiac output; the oxygen supply to the myocardium remained unchanged while that to the brain decreased only slightly. In hemoconcentration, vasodilation occurred in the myocardium and the brain to maintain constant oxygen supply. Splenic vessels had marked vasoconstriction with Hct alteration in either direction. Blood vessels in the liver, intestine, and kidney responded with a milder vasoconstriction and maintained a constant oxygen supply between Hct of 30-55%. Therefore, during Hct alteration, redistribution of blood flow to myocardium and brain occurred. The optimal Hct range for constant oxygen supply was different among various organs.

scholarly journals Brain Blood Flow in Andean and Himalayan High-Altitude Populations: Evidence of Different Traits for the Same Environmental Constraint

2010 ◽  
Vol 31 (2) ◽  
pp. 706-714 ◽  
Author(s):  
Gerard FA Jansen ◽  
Buddha Basnyat
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Arterial Oxygen Saturation ◽  
Oxygen Demand ◽  
Arterial Oxygen ◽  
The Tibetan Plateau ◽  
Brain Blood Flow ◽  
Organ Systems ◽  
Andean Altiplano ◽  
The Difference

Humans have populated the Tibetan plateau much longer than the Andean Altiplano. It is thought that the difference in length of occupation of these altitudes has led to different responses to the stress of hypoxia. As such, Andean populations have higher hematocrit levels than Himalayans. In contrast, Himalayans have increased circulation to certain organ systems to meet tissue oxygen demand. In this study, we hypothesize that cerebral blood flow ( CBF) is higher in Himalayans than in Andeans. Using a MEDLINE and EMBASE search, we included 10 studies that investigated CBF in Andeans and Himalayans between 3,658 and 4,330 m altitude. The CBF values were corrected for differences in hematocrit and arterial oxygen saturation. The data of these studies show a mean hematocrit of 50% in Himalayans and 54.1% in Andeans. Arterial oxygen saturation was 86.9% in Andeans and 88.4% in Himalayans. The CBF in Himalayans was slightly elevated compared with sea-level subjects, and was 24% higher compared with Andeans. After correction for hematorit and arterial oxygen saturation, CBF was ~20% higher in Himalayans compared with Andeans. Altered brain metabolism in Andeans, and/or increased nitric oxide availability in Himalayans may have a role to explain this difference in brain blood flow.

Effects of protoveratrine on coronary blood flow of the renal hypertensive dog

1963 ◽  
Vol 204 (5) ◽  
pp. 895-898 ◽  
Author(s):  
James W. West ◽  
Elwood L. Foltz
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Oxygen Saturation ◽  
Coronary Blood Flow ◽  
Arterial Oxygen Saturation ◽  
Renal Hypertension ◽  
Peripheral Resistance ◽  
Arterial Oxygen ◽  
Arterial Blood ◽  
Venous Oxygen Saturation

In renal hypertension, protoveratrine decreased coronary blood flow, cardiac oxygen consumption, arterial and venous oxygen saturation, coronary arteriovenous oxygen difference, mean arterial blood pressure, cardiac output, cardiac work, cardiac efficiency, cardiac rate, total peripheral resistance, coronary resistance, respiratory rate, and minute volume. The decrease was significant in all functions except coronary blood flow, coronary venous oxygen saturation, and cardiac output. The results of these experiments indicate that in the renal hypertensive animal, a therapeutically beneficial effect was derived from protoveratrine on the circulation by its ability to decrease the work of the heart (lowering the elevated mean arterial pressure) and the coronary vascular resistance while maintaining coronary blood flow and cardiac output within normal levels. The less advantageous effect of protoveratrine on circulation resulted from its respiratory inhibiting effect which reduced the arterial blood oxygen saturation. Although a small decline in coronary venous oxygen saturation was noted, the coronary flow and oxygen delivery in face of the reduced arterial oxygen saturation was apparently adequate to maintain a normal cardiac activity.

Use of the bidirectional cavopulmonary shunt in patients under one year of age

1995 ◽  
Vol 5 (1) ◽  
pp. 28-30
Author(s):  
Juan Calderón-Colmenero ◽  
Samuel Ramírez ◽  
Maria Rijlaarsdam ◽  
Alfonso Buendia ◽  
Carlos Zabal ◽  
...  
Keyword(s):  
Right Ventricle ◽  
Oxygen Saturation ◽  
Pulmonary Stenosis ◽  
Arterial Oxygen Saturation ◽  
Double Outlet Right Ventricle ◽  
Arterial Oxygen ◽  
Cardiothoracic Ratio ◽  
Bidirectional Cavopulmonary Shunt ◽  
One Year ◽  
Cavopulmonary Shunt

SummaryBetween January 1990 and March 1992, a bidirectional cavopulmonary shunt was performed in seven patients under one year of age for palliation of complex cyanotic congenital heart disease. Five cases had tricuspid atresia with a restrictive ventricular septal defect. One case presented with complete mirror imagery, right-sided heart, double inlet and double outlet right ventricle with pulmonary stenosis. Another case had isomerism of the left atrial appendages with common atrioventricular valve and double outlet right ventricle. All had a pulmonary arterial index greater than 250 mm/m2(Nakata index). Age and weights before surgery averaged five months (one to 11 months) and 5.6 kg (range 2.8 to 8.5 kg) respectively. Preoperative mean arterial oxygen saturation measured by cardiac catheterization was 60.05±14% and postoperative mean arterial oxygen saturation on room air was 79.85±6.03% (p<0.05). There were no deaths, although postoperative complications occurred in three patients, namely pleural effusion and pneumothorax. Mean follow-up was 10±4.2 months. The cardiothoracic ratio decreased in all cases. On subsequent echocardiographic studies with pulsed Doppler sampling, low velocity systolic-diastolic forward flow was registered in the pulmonary trunk. The velocity of flow increased clearly during inspiration. The bidirectional cavopulmonary shunt can be considered as primary palliation for complex cardiac malformations with restricted pulmonary flow independent of age and body weight.

Quantification of adult cerebral hemodynamics by near-infrared spectroscopy

1994 ◽  
Vol 77 (6) ◽  
pp. 2753-2760 ◽  
Author(s):  
C. E. Elwell ◽  
M. Cope ◽  
A. D. Edwards ◽  
J. S. Wyatt ◽  
D. T. Delpy ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Infrared Spectroscopy ◽  
Oxygen Saturation ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Arterial Oxygen Saturation ◽  
Cerebral Hemodynamics ◽  
Arterial Oxygen ◽  
The Mean

Near-infrared spectroscopy was used to measure global cerebral blood flow and volume in 10 healthy adult volunteers. High- and low-cerebral blood flow compartments were detected with mean flows for all 10 subjects of 59 +/- 21 (SD) and 11 +/- 4 ml.100 g-1.min-1, respectively. The mean cerebral blood volume of the group was 2.85 +/- 0.97 ml/100 g. Analysis of spontaneous changes in the cerebral concentrations of oxyhemoglobin and deoxyhemoglobin demonstrated strong correlations between respiratory rate and the oscillation frequency of cerebral oxyhemoglobin concentration (r = 0.99) and arterial oxygen saturation (SaO2) (r = 0.99). An estimate of the mean cerebral oxygen saturation for all subjects averaged 59.4 +/- 12.4% when their mean SaO2 was 91.8 +/- 2.4% (equivalent to 67.6 +/- 13.8% at a normoxic SaO2 of 98%). These results demonstrate that near-infrared spectroscopy can be used as a noninvasive bedside technique for both qualitative and quantitative evaluation of cerebral hemodynamics and oxygenation in adults.

scholarly journals Fetal endocrine responses to prolonged reduced uterine blood flow are altered following bilateral sectioning of the carotid sinus and vagus nerves

1998 ◽  
Vol 157 (1) ◽  
pp. 149-155 ◽  
Author(s):  
PE Stein ◽  
SE White ◽  
J Homan ◽  
L Fraher ◽  
HH McGarrigle ◽  
...  
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Carotid Sinus ◽  
Arterial Oxygen Saturation ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Uterine Blood Flow ◽  
Vagus Nerves ◽  
Fetal Sheep ◽  
Fetal Plasma

The present study examines the effect of carotid sinus/vagosympathetic denervation on fetal endocrine responses to prolonged reduced uterine blood flow (RUBF). Fetal sheep had vascular catheters inserted following bilateral sectioning of the carotid sinus and vagus nerves (denervated, n = 7) or sham denervation (intact, n = 7). Uterine blood flow was mechanically restricted at 126.1 +/- 0.7 days (mean +/- S.E.M.) for 24 h, decreasing arterial oxygen saturation by 47.3 +/- 2.6% (P < 0.01). Fetal plasma samples were obtained at -1, 3, 6, 12 and 24 h for subsequent analyses of arginine vasopressin (AVP), angiotensin II and catecholamines. The AVP response to prolonged RUBF was markedly attenuated in denervated fetuses (15.6 +/- 3.6 to 34.9 +/- 6.0 pg/ml) when compared with intact (10.0 +/- 1.4 to 127.3 +/- 28.4 pg/ml). In contrast, intact fetuses demonstrated no change in plasma angiotensin II concentrations with RUBF whereas denervated fetuses demonstrated a marked increase from 47.5 +/- 18.9 to 128.7 +/- 34.2 pg/ml. The norepinephrine and epinephrine responses to prolonged RUBF were attenuated in denervated fetuses (950.1 +/- 308.9 and 155.8 +/- 58.5 to 1268.3 +/- 474.6 and 290.6 +/- 160.2 pg/ml respectively) when compared with intact (1558.3 +/- 384.4 and 547.3 +/- 304.7 pg/ml to 3289.2 +/- 1219.8 and 896.8 +/- 467.8 pg/ml respectively). These results support a role for the peripheral chemoreceptors in mediating fetal endocrine responses to prolonged RUBF, which may in part lead to the altered cardiovascular responses observed in denervated fetuses under these conditions.

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