Mean Total Blood Flow Research Articles

Ultrasonic transit-time measurement of blood flow in the umbilical arteries and veins in the bovine fetus during stage II of labor

The vitality of the bovine fetus during parturition depends on an intact umbilical circulation to supply adequate amounts of oxygen and nutrients to the fetus. The goal of the present study was to measure the blood flow in the umbilical vessels during stage II of labor and to determine when blood flow ceases in the umbilical cord. In 20 cows, ultrasonographic transducers were placed on one umbilical vein and one umbilical artery after rupture of the allantochorionic sac, and the blood flow volume per unit time was measured. At the same time, a pressure transducer was placed into the uterus to measure uterine pressure. Parturition was spontaneous in all 20 cows. In 20 live calves born, pH, base excess and lactate concentration were measured in the blood immediately after birth. During the last 90 min before birth the mean total umbilical blood flow (artery and vein combined) was 1.186 ± 0.028 L/min. Calves with a blood pH ≥ 7.2 ( n = 13) had a higher mean total blood flow than calves with a pH < 7.2 ( n = 7; 1.243 ± 0.038 versus 1.095 ± 0.038 L/min). In calves with a blood pH < 7.2, the mean total blood flow decreased from 1.178 ± 0.134 at 20 min before birth to 0.959 ± 0.126 L/min at the end of stage II of labor. During this time period, the arterial blood flow did not differ between calves with a blood pH ≥ 7.2 and < 7.2, but venous blood flow decreased significantly in calves with a blood pH < 7.2. During uterine contractions, the total umbilical blood flow decreased significantly by 0.22 L/min. The blood flow in the umbilical artery and vein ceased before the calves were completely born.

Leukocytes trapped in the fetal membranes of newborn foals

The vitality of the bovine fetus during parturition depends on an intact umbilical circulation to supply adequate amounts of oxygen and nutrients to the fetus. The goal of the present study was to measure the blood flow in the umbilical vessels during stage II of labor and to determine when blood flow ceases in the umbilical cord. In 20 cows, ultrasonographic transducers were placed on one umbilical vein and one umbilical artery after rupture of the allantochorionic sac, and the blood flow volume per unit time was measured. At the same time, a pressure transducer was placed into the uterus to measure uterine pressure. Parturition was spontaneous in all 20 cows. In 20 live calves born, pH, base excess and lactate concentration were measured in the blood immediately after birth.During the last 90 min before birth the mean total umbilical blood flow (artery and vein combined) was 1.186 ± 0.028 L/min. Calves with a blood pH ≥ 7.2 (n = 13) had a higher mean total blood flow than calves with a pH < 7.2 (n = 7; 1.243 ± 0.038 versus 1.095 ± 0.038 L/min). In calves with a blood pH < 7.2, the mean total blood flow decreased from 1.178 ± 0.134 at 20 min before birth to 0.959 ± 0.126 L/min at the end of stage II of labor. During this time period, the arterial blood flow did not differ between calves with a blood pH ≥ 7.2 and < 7.2, but venous blood flow decreased significantly in calves with a blood pH < 7.2. During uterine contractions, the total umbilical blood flow decreased significantly by 0.22 L/min. The blood flow in the umbilical artery and vein ceased before the calves were completely born.

Complete arterial coronary revascularisation using radial artery conduit for double thoracic artery inlet flow: arterial sling operation.

Coronary artery bypass graft surgery with arterial revascularisation of all diseased coronary vessels is considered highly efficient because arterial grafts have an excellent long-term patency compared with venous grafts. However, problems to reach the infero-lateral wall with the in situ internal thoracic arteries usually require alternative techniques. We present the first results of a new surgical principle using a free radial artery segment to complete the arterial coronary revascularisation and concomitantly connect the internal thoracic arteries. In patients referred for coronary bypass surgery and three-vessel disease an end-to-end anastomosis of the right internal thoracic artery and the radial artery segment preceded cardiopulmonary bypass, during which side-to-side anastomoses of the radial artery segment were used to revascularise stenotic branches of the right coronary and circumflex arteries. The left internal thoracic artery was used for revascularisation of stenotic branches of the left anterior descending artery, and finally an end-to-side anastomosis of the radial artery segment to the left internal thoracic artery was performed. Coronary artery blood flow was measured in 41 patients with Doppler flow probe. One hundred and ninety-two coronary anastomoses (an average of 4.2 per patient) were performed in 46 patients. We measured a mean total blood flow in the arterial sling graft of 104ml/min (range 35-221ml/min), compared with 69 and 68ml/min of the single inlet right and left internal thoracic arteries, respectively (P<0.01). Flow capacities of 104 and 120ml/min of the right and left internal thoracic arteries were measured during clamp of both the aorta and the contralateral internal thoracic artery. The mean crossclamp duration was 77min (range 51-113min). Postoperative angiography demonstrated patent graft anastomoses to all coronary arteries. There were no perioperative deaths or myocardial infarctions. One patient had a minor postoperative stroke. Complete arterial revascularisation can be achieved by the arterial sling operation with an acceptable crossclamp time and a high early rate of graft patency. The double arterial inlet provides a 50% higher blood flow to the beating heart and two-fold increase in the flow reserve compared with a single inlet. Although further research including long-term follow-up of this new principle is required, the present findings seem promising and suggest that the arterial sling operation has a potential role for complete arterial coronary revascularisation.

Physiological evidence for arteriovenous anastomoses in the uterine circulation of late-pregnant ewes.

1. The objective of the present study was to determine whether arteriovenous anastomoses (AVA) are present in the uterine circulation of conscious, late-pregnant ewes. 2. Twenty late-pregnant ewes were assigned to two groups. In group 1, 15 microm coloured microspheres were injected into the uterine artery of the pregnant horn and the relative proportion of microspheres trapped in the uterus and lungs was determined. The percentage shunting of blood measured by this method was 17+/-3%, representing a blood flow of 164+/-39 mL/min (n = 12). Any contribution of ovarian, cervical, rectal and other vascular beds was specifically excluded in this group. 3. In group 2, total uterine capillary flow was measured using the reference blood flow method, by injecting 15 microm microspheres into the heart. Calibrated flow probes, placed on both main uterine arteries, concurrently measured total uterine blood flow. Total blood flow to the uterus (flow probe) was significantly greater (t = 3.415; P = 0.027) than uterine capillary flow (microspheres), indicating AVA shunting in the uterine circulation. Mean total blood flow to the uterus was 1749+/-160 mL/min, of which an average 25+/-5% (n = 5 sheep) was shunted. 4. The percentage AVA shunting for groups 1 and 2 was not significantly different (t = 1.219; P = 0.24) and, when combined, the mean percentage of uterine blood flow passing through AVA in the late-pregnant sheep was determined to be 19+/-3%. 5. The present study shows that AVA are present and patent in the uterine circulation of late-pregnant ewes and that they account for the shunting of approximately 20% of the uterine blood flow into the maternal venous circulation.

Influence of a delay on latissimus dorsi muscle flap blood flow

The regional and total blood flow of canine latissimus dorsi muscle flaps (LDMFs) were examined to study the effect of a delay procedure, ligation of the perforators, before complete flap elevation. The regional blood flow of the middle and distal regions of the nondelayed LDMFs was poor and significantly lower than the proximal region at rest. The regional blood flow during the exercise test was improved and significantly higher in the middle (62% increase) and distal regions (187% increase) of the delayed LDMFs as compared with the nondelayed LDMFs. The mean total blood flow of the delayed LDMFs was 14 mL.min-1.100(-1) g at rest, increased to 30 mL.min-1.100(-1) g during exercise tests with intermittent burst electrical stimulation, and was maximal at 40 mL.min-1.100(-1) g immediately after the exercise. The phasic arterial blood flow of the delayed LDMFs was inhibited during contraction at 9 mL.min-1.100(-1) g, whereas it was 44 mL.min-1.100(-1) g during relaxation. In contrast, the phasic venous blood flow was accentuated during contraction to 32 mL.min-1.100(-1) g compared with 16 mL.min-1.100(-1) g during relaxation.

Intracortical distribution of renal blood flow during saline infusion in dogs.

AbstractThe increase in sodium excretion induced by isotonic saline infusion has been attributed to a redistribution of blood flow within the cortex to “salt‐loosing” superficial nephrons. To test this hypothesis, mean blood flow to outer (OCF) and inner (ICF) cortex was measured in dogs before and during saline expansion, using H2‐clearance rates as indicator of local blood flow. Mean total blood flow (RBF) was measured with an electromagnetic flowmeter. During infusion of 0.9 % NaCI, 30 ml/min for 30–80 min, urine flow increased from 1.1 to 7.5 ml/min, glomerular filtration rate from 39.8 to 49.1 ml/min, RBF rose from 214 to 276 ml/min, OCF from 3.43 to 3.87 ml/min and ICF from 3.50 to 3.91 ml/min. OCF/ICF did not change significantly during saline expansion. Autoregulation of local blood flow was maintained after saline loading with no change in OCF/ICF within the pressure range of autoregulation. Since massive saline infusion is followed by a parallel increase in blood flow to outer and inner cortex, it is concluded that intracortical redistribution of blood flow is not the mechanism of natriuresis during saline loading.

Intrarenal blood flow distribution in canine puppies.

Extract: The present study was designed to examine the developmental changes in renal blood flow distribution in canine puppies utilizing the techniques of xenon-133 (133Xe) washout, anatomic measurements, and para-aminohippuric acid (PAH) clearances and extractions. The distribution patterns determined by analysis of the xenon washout curves were confirmed by studies of the intrarenal distribution of injected radioactive microspheres. The mean total blood flow was 1.2 ml/g kidney/min at 6 weeks of age and rose progressively to the adult value of 3.5 ml/g kidney/min at 14–16 weeks of age. The mean Component I flow, 1.7 ml/g/min at 6 weeks, increased to 4.7 ml/g/min at 14–16 weeks of age. The increase in Component I flow was associated with an increase in PAH extraction ratio. The low renal blood flow observed in the puppy less than 6 weeks of age appears to be due in large part to a small cortical volume. Anatomically, the amount of cortex/medulla ratio was less in the puppy than in the adult, and this was supported by the relatively low cortical volume of distribution noted in the washout studies. At 10 and 12 weeks of age, when the relative cortical mass approximated that found in the adult, the Component I flow rate was still low, but from age 12 weeks, Component I flow and total renal blood flow increased markedly. Renal blood flow increased during a period when cardiac output per kilogram body weight was constant and total peripheral resistance was rising. The progressive age-dependent increase that was noted in total renal blood flow was primarily due to an increase in cortical flow. The increased cortical flow was in part a consequence of cortical growth; change in sympathetic tone may also have contributed.