Total Systemic Blood Flow Research Articles

The Functioning of the Frog’s Single Ventricle

African clawed frog (Xenopus laevis) has double-inlet and single-outlet single ventricle supporting both systemic and pulmonary circulations, with normal lifespan of 25-30 years. The relationship between pulmonary and systemic blood flows was investigated using echocardiography. Twelve female African clawed frogs, age 18-24 months, mean weight 173±19 grams were studied. Heart rate, percutaneous oxygen saturation, echocardiography derived 2D and blood flow in all cardiovascular structures were measured in two temperature setting, 17◦C (normal environment for frogs) and 22 C. In eight frogs cerebral Near-Infra-Red Spectroscopy (NIRS) was measured. Mean oxygen saturation was 66±9% with temperature of 22◦C and 85±6% with 17◦C (P<0.001), while there was no statistical difference between mean heart rates, respectively 48 13 and 42±7 beats/min. Doppler echocardiography showed a mean total pulmonary blood flow (QP) =173.0 ml/min and mean total systemic blood flow (QS) = 99.3ml/min, with mean QP/QS of 1.74:1.00. The only statistical correlation between size of the cardiovascular structures and body weight was found for the pulmonary veins, with correlation coefficient = 0.71 (P=0.02). NIRS measurements showed a reverse correlation (coefficient = -0.21) with oxygen saturation. The frog’s heart has peculiar morphologic and functional characteristics allowing normal quality of life for many years despite the presence of single ventricle. Baseline QP/QS under general anesthesia was significant for increased total pulmonary blood flow. Exposure to environmental temperature 5◦C higher than normal caused peripheral vasodilatation, with subsequent decrease of QP/QS and reduced oxygenation.

Benefits and Risks of Delayed Surgery for Ventricular Septal Rupture after Acute Myocardial Infarction.

The timing of surgery for ventricular septal rupture (VSR) after acute myocardial infarction (AMI) remains controversial. This study investigated the benefits and risks of delayed surgery for post-AMI VSR and examined differences in echocardiographic findings between early and delay groups.A total of 38 consecutive patients with post-AMI VSR who underwent surgery at our hospital between May 2003 and November 2020 were retrospectively analyzed. Our strategy was to delay surgery until 2 weeks after AMI. If patients demonstrated organ dysfunction, we considered early surgery. Patients were divided into early (n = 20; 53%) and delay (n = 18; 47%) groups. Risks and benefits were investigated based on echocardiographic findings during the waiting period. The delay group had more preoperative intravenous catheter infections (P = 0.008) but fewer reoperations (P = 0.02) and lower operative mortality (P = 0.04) than the early group. The VSR defect diameter and total pulmonary blood flow to total systemic blood flow (Qp/Qs) increased in both groups while waiting. Nevertheless, the early group had a significantly higher Qp/Qs change rate than the delay group (P = 0.05). The 30 day and hospital mortality rates were 5.3% and 13.2%, respectively.The VSR defect diameter and Qp/Qs in both groups increased with time and can therefore become risk factors. Nonetheless, the benefit of waiting exceeded the risk because our outcomes were better than those previously reported.

MRI Phase-Contrast Blood Flow in Fasting Pediatric Patients with Fontan Circulation Correlates with Exercise Capacity.

To assess regional blood flow in fasting pediatric patients with Fontan circulation by using MRI and to explore associations with clinical parameters. In this retrospective study, pediatric patients who had undergone the Fontan procedure (<18 years of age) and had undergone clinical cardiac MRI, performed after at least 4 hours of fasting, between 2018 and 2021 were included. Regional blood flow was compared with published healthy volunteer data (n = 19) and assessed in relation to hemodynamic parameters and clinical status. Data are presented as medians, with first to third quartiles in parentheses. Mann-Whitney U, Kruskal-Wallis, χ2, and Spearman rank correlation tests were used. Fifty-five patients (38 boys) with median age at MRI of 14 years (IQR, 11-16 years) and median time from Fontan procedure to MRI of 10 years (IQR, 8-12 years) were included. Patients after Fontan procedure had lower ascending aortic, inferior vena cava, and total systemic blood flow compared with healthy volunteers (3.00 L/min/m2 [IQR, 2.75-3.30 L/min/m2] vs 3.61 L/min/m2 [IQR, 3.29-4.07 L/min/m2]; 1.73 L/min/m2 [IQR, 1.40-1.94 L/min/m2] vs 2.24 L/min/m2 [IQR, 2.06-2.75 L/min/m2]; 2.78 L/min/m2 [IQR, 2.45-3.10 L/min/m2] vs 3.95 L/min/m2 [IQR, 3.20-4.30 L/min/m2], respectively; P < .001). Portal vein flow was greater than hepatic vein flow in 25% of patients. Fontan blood flow was inversely correlated with pre-Fontan mean pulmonary artery pressure (Spearman rank correlation coefficient [rs ]= -0.42, P = .005) and ventricular end diastolic pressure (rs = -0.33, P = .04) and positively correlated with post-Fontan percent predicted oxygen consumption at peak workload (rs = 0.34, P = .02). Reference ranges are provided for regional systemic blood flow derived by using MRI in fasting pediatric patients with Fontan circulation, who had lower systemic blood flow compared with healthy volunteers. Lower fasting Fontan blood flow correlated with lower exercise capacity.Keywords: Pediatrics, Heart, Congenital, MR Imaging, Hemodynamics/Flow Dynamics, Cardiac Supplemental material is available for this article. © RSNA, 2022.

Contribution of active atrial contraction to cardiac output in anesthetized American alligators (Alligator mississippiensis).

Ventricular filling may occur directly from the venous circulation during early diastole or via atrial contraction in late diastole. The contribution of atrial contraction to ventricular filling is typically small in mammals (10-40%), but has been suggested to predominate in reptiles. We investigated the importance of atrial contraction in filling of the ventricle in American alligators (Alligator mississippiensis) by bypassing both atria (with the use of ligatures to prevent atrial filling) and measuring the resultant effects on cardiac output in anesthetized animals. Atrial ligation had no significant effects on total systemic blood flow before or after adrenaline injection. Unexpectedly, pulmonary flow was increased following atrial ligation prior to adrenaline treatment, but was unaffected after it. These findings suggest that the atria are non-essential (i.e. redundant) for ventricular filling in alligators, at least under anesthesia, but may serve as important volume reservoirs.

Systemic Blood Flow Relations in Conscious South American Rattlesnakes

Estimating total systemic blood flow based on measurements from a single aortic arch is common practice in cardiovascular stud- ies on reptiles to avoid heavy instrumentation and consequent stress responses. This practice requires the validation of a specific correction factor that expresses the relationship between the measured blood flow and the blood flow to be estimated. Misleading estimations may occur when correction factors are used in different conditions from those they were originally measured. Despite recognized as a problem, such misleading estimations are common in physiology. In the present study, we derived values for correction factors to estimate systemic blood flow in the South American rattlesnake, Crotalus durissus, following recovery from anesthesia, using serial measurements of blood flow in the three main systemic arteries, left or distal right aortic arches and the carotid artery. Blood flow recorded in the left aortic arch provided the most reliable and less variable correction factors. Different from previously published, blood flow distribution in the systemic circulation varied with temperature. We suggest the use of the specific correction factors present in this paper for different experimental protocols and temperatures. Furthermore, we can affirm that unilateral left vagotomy, which effectively ablated control of right-left shunts, does not affect systemic blood flow distribution, so the same correction factors can be used.

Oxygen Metabolism under Various bypass flow Conditions during Cardiopulmonary Support in Awake Goats

Despite its wide clinical application, patient recovery from cardiopulmonary support (CPS) is not necessarily satisfactory. To clarify what influence CPS has on organ perfusion, we investigated the oxygen metabolism under various bypass flow (BF) conditions in a series of chronic animal CPS experiments. The CPS system, which consists of a pulsatile ventricular assist device and a compact artificial lung was installed without anesthesia in 6 adult goats weighing 49-51 kg. BF was adjusted stepwise from 0% to 50%, 75%, 90%, and 100% of total systemic blood flow (TSF) by balancing the pulmonary arterial flow. The animals' TSF and oxygen delivery (DO2) were sufficiently maintained throughout the experiments. The oxygen consumption (VO2) and the oxygen extraction rate (ExO2) increased from 178+/-14 to 342+/-19 ml/min, and from 28+/-2% to 64+/-1%, respectively, in proportion to the increase of CPBF dependency from 0% to 100%. The blood lactate level did not change appreciably even at 90% BF from 5.7+/-0.3 to 11.2+/-1.2 mg/dl, but drastically elevated to 23.5+/-4.6 mg/dl at the total bypass. This indicates that CPS leads to a relative lack of oxygen and can induce organ dysfunction due to increasing VO2 and ExO2 in proportion to the increase of BF dependence even if TSF and DO2 are sufficiently maintained.

Hemodynamic effects of prostaglandins and catecholamines in graded reduction of pulmonary flow during venoarterial bypass in awake goats.

The roles of prostaglandins and catecholamines in the hypotensive hemodynamic change during cardiopulmonary support with a venoarterial bypass (VAB) were investigated in a series of chronic animal experiments of gradually reduced pulmonary arterial blood flow (PAF). The VAB system consisted of a pulsatile ventricular assist device, an artificial lung, and the right atrium uptake and descending aorta return cannulae in four adult goats weighing 49-51 kg. The PAF was adjusted to 50, 10, and 0% of the total systemic blood flow. Indomethacin, an inhibitor of prostaglandin production; phentolamine, an alpha-antagonist of catecholamine; and noradrenaline, an agonist of catecholamine were administered at each PAF condition. The mean aortic pressure (mAoP) and the systemic vascular resistance decreased in proportion to the decrease in PAF. Indomethacin increased the mAoP at all PAF conditions, indicating a relationship between prostaglandins and hypotension. Phentolamine decreased the mAoP at all PAF conditions, indicating a normal response of catecholamine receptors. However, noradrenaline increased the mAoP at 50 and 10% PAF, but did not appreciably increase the value at 0% PAF, indicating complete response of catecholamine receptors to endogenous catecholamines at 0% PAF only. In conclusion, prostaglandins play a substantial role in hypotension during VAB, and catecholamines may subsequently increase in compensation for extreme hypotension.

The mechanism of cardiac shunting in reptiles: a new synthesis.

The mechanism of cardiac shunting in reptiles is controversial. Recent evidence suggests that a right-to-left shunt in turtles results primarily from a washout mechanism. The mechanism that accounts for left-to-right (L-R) shunting is unresolved. This study used haemodynamic analysis and digital subtraction angiography to determine the mechanism of L-R cardiac shunting in the turtle Trachemys (Pseudemys) scripta. Animals were instrumented with ultrasonic blood flow probes (Transonic Systems, Inc.) for the measurement of total pulmonary blood flow and total systemic blood flow. In addition, catheters were inserted into the common pulmonary artery (PA), the systemic arteries, the left atrium and right atrium. These catheters were used for the measurement of blood pressure or for the infusion of radio-opaque material. Haemodynamic conditions were altered by electrical stimulation of the afferent (VAF) or efferent vagal nerves or by infusion of vasoactive drugs. Under control conditions, the peak systolic pressure in the systemic arteries was slightly higher than that in the PA (30.6 versus 28.3 mmHg; 4.08 versus 3.77 kPa), whereas diastolic pressure in the PA was significantly less than that in the systemic arteries (9.8 versus 24.4 mmHg; 1.31 versus 3.25 kPa). During VAF stimulation, the peak systolic pressures in the PA and aortae almost doubled. Diastolic pressure in the systemic arteries also doubled, but it increased by only 45% in the PA. Ejection of blood into the PA preceded that into the left aorta by 53 ms under control conditions. This difference increased (by as much as 200 ms) as the difference in the diastolic pressures between the two circulations increased during VAF stimulation. This resulted in the development of a large net L-R shunt. Under these conditions, digital subtraction angiography showed that the L-R shunt resulted from a combination of both washout and pressure mechanisms.

Regulation of central vascular blood flow in the turtle.

The purpose of this study was to determine the effects of vagal nerve stimulation on the pulmonary and systemic circulations in the turtle Pseudemys scripta. The heart rate (HR), systemic vascular resistance (Rsys), pulmonary vascular resistance (Rpul), total pulmonary blood flow (Qpul), and total systemic blood flow (Qsys) were measured during electrical stimulation of the vagal efferent and the vagal afferent nerves. Vagal efferent nerve stimulation resulted in a bradycardia, increased Rsys and Rpul, and a 60% reduction in the Qpul and Qsys. These cardiovascular changes were eliminated after an intravenous injection of atropine. In contrast, vagal afferent nerve stimulation resulted in a tachycardia, a twofold increase in Rsys, a reduction in Rpul, and an 85% increase in Qpul. These changes were eliminated after pretreating the animals with bretylium tosylate (10 mg/kg). An intravenous infusion of epinephrine (0.1 micrograms/kg) produced cardiovascular changes similar to vagal afferent stimulation. The cardiovascular changes resulting from afferent and efferent nerve stimulation were similar to the cardiovascular adjustments often associated with intermittent lung ventilation in reptiles. The results of our study suggest that such cardiovascular changes are under cholinergic and adrenergic control.

Intrapulmonary distribution of bronchial blood flow after moderate smoke inhalation

The systemic blood flow to the airways of the left lung was determined by the radioactive microsphere technique before and 17 h after smoke inhalation in six conscious sheep (smoke group) and six sheep insufflated with air alone (sham group). Smoke inhalation caused a sixfold increase in systemic blood flow to the lower trachea (baseline 10.6 +/- 1.7 vs. injury 60.9 +/- 16.1 ml.min-1.100 g-1) and an 11- to 14-fold increase to the intrapulmonary central airways (baseline range 9.5 +/- 1.9 to 13.5 +/- 3.7 ml.min-1.100 g-1 vs. injury 104.6 +/- 32.2 to 187.3 +/- 83.6 ml.min-1.100 g-1). There was a trend for this hyperemic response to be greater as airway diameter decreased from the trachea to 2-mm-diam central airways. In airways smaller than 2 mm, the hyperemic response appeared to diminish. The total systemic blood flow to whole lung is predominantly to small peripheral airways and showed no significant increase from its baseline level of 17.5 +/- 3.7 ml.min-1.100 g-1 in the lung homogenate. Occlusion of the bronchoesophageal artery decreased central airway blood flow 60-80% and peripheral airway blood flow 40-60% in both the sham and the smoke groups.

Blood Flow in Acute Hypoxia in A Cephalopod

ABSTRACT This paper reports a method of measuring blood flow in the dorsal aorta of Octopus vulgaris using fixed magnet flow meters. Blood flow, like blood pressure, falls progressively during acute hypoxia. Flow increases greatly as soon as the ambient rises, with values for a given external exceeding those found during the preceding development of hypoxia. On average, about 70 % of the total systemic blood flow runs down the aorta to the head and arms; the rest goes to the gonad, to the mantle, to the coronary circulation and to the guts. This pattern remains unchanged as the ambient falls.

PULMONARY VASCULAR EFFECTS OF POSTOPERATIVE ANESTHESIA IN CONGENITAL DIAPHRAGMATIC HERNIA

Because of persistent high mortality of patients(pts)with congenital diaphragmatic hernia (CDH), symptomatic within hours of birth, from persistent fetal circulation(PFC); we designed a protocol to assess the physiologic effects of general anesthesia(GA) after repair of CDH. In 12 months 10 pts, presenting at < 7hrs of age, underwent repair of left sided CDH. Cardiac catheterization was performed immediately after surgery. Postoperatively GA was maintained with fentanyl and pancuronium; using rapid ventilation (2 Hz-FiO2 1.0). Pulmonary artery(PA)and aortic pressures and prepost ductal PaO2s were continuously recorded. The ratio of shunt to total systemic blood flow(Qs/Qt) was calculated and recorded throughout the postoperative period. Three pts with severely hypoplastic lungs never improved and died from hypoxia and acidosis. Seven pts initially achieved a PaO2>150 torr after surgery 6(86%)survived; overall survival 60%. All 7pts who entered the 'honeymoon' period had a low pulmonary vascular resistance(PVR); 5 later developed suprasystemic PVR and PFC. In all but one, who died at 14 days of age, the PVR was controlled by fentanyl and ventilatory adjustments without the use of vasodilators. The Qs/Qt was initially greater than 50% in all but 2pts decreasing to less than 15% by 48hrs in all survivors. While closely monitoring the PA pressure and PaO2 the pts were gradually weaned from pressure ventilation and oxygen. These preliminary data suggest that those pts with CDH who enter the 'honeymoon' period after repair have sufficient lung tissue to survive. Prolonged GA with fentanyl may blunt the reactivity of the PVR allowing postnatal maturation of the pulmonary circulation, obviating the need for potentially dangerous vasodilators. When coupled with careful monitoring these techniques may improve the survival of pts with CDH.

Coronary blood flow during cardiopulmonary resuscitation in swine.

Recent papers have raised doubt as to the magnitude of coronary blood flow during closed-chest cardiopulmonary resuscitation. We will describe experiments that concern the methods of coronary flow measurement during cardiopulmonary resuscitation. Nine anesthetized swine were instrumented to allow simultaneous measurements of coronary blood flow by both electromagnetic cuff flow probes and by the radiomicrosphere technique. Cardiac arrest was caused by electrical fibrillation and closed-chest massage was performed by a Thumper (Dixie Medical Inc., Houston). The chest was compressed transversely at a rate of 66 strokes/min. Compression occupied one-half of the massage cycle. Three different Thumper piston strokes were studied: 1.5, 2, and 2.5 inches. Mean aortic pressure and total systemic blood flow measured by the radiomicrosphere technique increased as Thumper piston stroke was lengthened (mean +/- SD): 1.5 inch stroke, 23 +/- 4 mm Hg, 525 +/- 195 ml/min; 2 inch stroke, 33 +/- 5 mm Hg, 692 +/- 202 ml/min; 2.5 inch stroke, 40 +/- 6 mm Hg, 817 +/- 321 ml/min. Both methods of coronary flow measurement (electromagnetic [EMF] and radiomicrosphere [RMS]) gave similar results in technically successful preparations (data expressed as percent prearrest flow mean +/- 1 SD): 1.5 inch stroke, EMF 12 +/- 5%, RMS 16 +/- 5%; 2 inch stroke, EMF 30 +/- 6%, RMS 26 +/- 11%; 2.5 inch stroke, EMF 50 +/- 12%, RMS 40 +/- 20%. The phasic coronary flow signal during closed-chest compression indicated that all perfusion occurred during the relaxation phase of the massage cycle. We concluded that coronary blood flow is demonstrable during closed-chest massage, but that the magnitude is unlikely to be more than a fraction of normal.

HbO2 dissociation in man during prolonged work in chronic hypoxia.

In healthy human sojourners to 3,100 m we studied exercise-induced shifts in HbO2 dissociation: their regulation in femoral venous blood and their net effect on estimated capillary PO2 (PC-O2) in working skeletal muscle. Prolonged heavy work effected an increase of 10.3 plus or minus 0.9 mmHg in in vivo P50 (7.30 PH-v, 41 degrees C-v, and 45 Pv-CO2); due entirely to the additive effects of increased venous temperature and [H+]. The rightward curve shift during work at 3,000 m, compared to that at 250 m, produced a similar increase in in vivo P50 but a reduced net effect on PC-O2, because Cv-02 at 3,100 m was reduced similar to 2 ml/100 ml to the lower converging portions of the curve. The lower Cv-O2 (and Pv-O2) at 3,100 M was attributable to a small decrease in total systemic blood flow. The net effect of the rightward curve shift during exercise on mean to end-capillary PO2 was positive in most cases (+1 to +8 mmHg PCO2). However, it was shown that the levels of mean to end-capillary PO2 (28-13 mmHg), which would have been obtained during exercise in the absence of any rightward curve shift, were more than adequate to sustain a steady state of aerobic energy production in working skeletal muscle. These data do not support the concept of a significant contribution to oxygen delivery to working skeletal muscle from in vivo shifts in HbO2 dissociation, during either acclimatization to high altitude or during prolonged muscular work.

Alterations of the fetal ECG as an early indication of intra-uterine asphyxia

During the study of the cerebral reactions of the fetal lamb to asphyxia the fetal ECG was found to react to asphyxia with elevation of the ST-segment and high and peaked T-waves. These alterations of the ECG occurred earlier than the typical changes in heart rate - bradycardia, dropped beats, A-V block. The ECG changes were well correlated to the cerebral reactions in terms of the somatosensory evoked EEG responses. To evaluate the relations between the ECG changes and hemodynamic variables ten experiments were conducted on mature lamb fetuses. In acutely exteriorized preparations ECG, arterial blood pressure, left ventricular pressure, myocardial contractility (dP/dt), heart rate and systemic blood flow (thermo-dilution) were measured and the fetus was subjected to varying degrees of hypoxia and hypercarbia. A close relation between the ECG changes and the total systemic blood flow and the myocardial contractility was obtained. Arterial blood pressure and heart rate deteriorated at a later stage and at more severe degrees of hypoxia than the ECG. It is concluded that the ECG pattern conveys information on hypoxia before typical effects of hypoxia on the heart rate appear in the fetal lamb.

Venoarterial pumping for relief of intractable cardiac failure in man.

The use of mechanical substitutes for the heart to pump blood from the great veins to the aorta in congestive failure has been proposed,^1,2and a heart-lung machine has been used in the support of patients with myocardial infarction.³Experimental work suggests that acute heart failure in animals may be relieved by venoarterial pumping without an oxygenator.⁴Our own animal studies⁵have shown that it is possible to pump about half the systemic venous return into the lower aorta without significant impairment of the oxygen supply to the vital organs. In normal animals the cardiac output is reduced by this procedure, and there may be an increase in the total systemic blood flow. Venoarterial pumping has been maintained for as long as 53 hours in a dog without serious effects and with subsequent survival. The present paper reports our experience with the first human case. <h3>Report</h3>

The Potter electroturbinometer; an instrument for recording total systemic blood flow in the dog.

The flowmeter described is a turbine which can be driven by the bloodstream. In the turbine is a magnet which induces a recordable signal in an adjacent coil. The flowmeter records pulsating flow as well as steady flow; it is insensitive to temperature and wide variations of blood viscosity. The pressure drop is rather high. The baseline and calibration are steady over long periods of time. The flowmeter has been successfully used for continuously recording the systemic output in the dog.