Arterial Blood Inflow Research Articles

Arterial Spin-Labeling MR Imaging Measurements of Timing Parameters in Patients with a Carotid Artery Occlusion

Arterial spin-labeling (ASL) with image acquisition at multiple delay times can be exploited in perfusion MR imaging to visualize and quantify the temporal dynamics of arterial blood inflow. In this study, we investigated the consequences of an internal carotid artery (ICA) occlusion and collateral blood flow on regional timing parameters. Seventeen functionally independent patients with a symptomatic ICA occlusion (15 men, 2 women; mean age, 57 years) and 29 sex- and age-matched control subjects were investigated. ASL at multiple delay times was used to quantify regional cerebral blood flow (CBF) and the transit and trailing edge times (arterial timing parameters) reflecting, respectively, the beginning and end of the labeled bolus. Intra-arterial digital subtraction angiography and MR angiography were used to grade collaterals. In the hemisphere ipsilateral to the ICA occlusion, the CBF was lower in the anterior frontal (31 +/- 4 versus 47 +/- 3 mL/min/100 g, P < .01), posterior frontal (39 +/- 4 versus 55 +/- 2 mL/min/100 g, P < .01), and frontal parietal region (49 +/- 3 versus 61 +/- 3 mL/min/100 g, P = .04) than that in control subjects. The trailing edge of the frontal-parietal region was longer in the hemisphere ipsilateral to the ICA occlusion compared with that in control subjects (2225 +/- 167 versus 1593 +/- 35 ms, P < .01). In patients with leptomeningeal collateral flow, the trailing edge was longer in the anterior frontal region (2436 +/- 275 versus 1648 +/- 201 ms, P = .03) and shorter in the occipital region (1815 +/- 128 versus 2388 +/- 203 ms, P = .04), compared with patients without leptomeningeal collaterals. Regional assessment of timing parameters with ASL may provide valuable information on the cerebral hemodynamic status. In patients with leptomeningeal collaterals, the most impaired territory was found in the frontal lobe.

The effect of craniotomy on the intracranial hemodynamics and cerebrospinal fluid dynamics in humans

The goal of the research was to study the effect of the trephination of the human cranial cavity on the intracranial hemodynamics and cerebrospinal fluid (CSF) dynamics. The sample comprised 15 patients of a neurosurgical clinic in whom a trephine opening in the cranial bones was made for medical indications. In these patients, at rest and during an appropriate functional load, we recorded pulse changes in blood circulation (by transcranial Doppler sonography) and in the ratio between the pulse fluctuations in the blood and CSF volumes (by rheoencephalography) before and after surgery. Simultaneous recording of these parameters followed by computer pattern and phase analyses allowed evaluation of the complex biomedical compliance of the cranium during successive phases of the cardiac rhythm: the inflow of arterial blood, the redistribution of blood/CSF volumes, and the outflow of venous blood. Analysis of the results showed a beneficial influence of craniotomy on the intracranial hemodynamics and CSF dynamics. This was reflected in an increase in the cranial compliance, which increased the pulse increment in the volume of the arterial blood in the skull almost twofold. After craniotomy, the cross-flow of CSF between the cranial and spinal cavities decreased significantly, giving way to volumetric compensatory translocations of blood and CSF within the cranial cavity per se during the cardiac cycle, which increased the intracranial utilization of the energy of the cardiac output and contributed to the outflow of venous blood from the cranium. The results suggest a beneficial effect of craniotomy on the physiological mechanisms of the circulatory and metabolic maintenance of the brain activity.

Effect of Recipient Arterial Blood Inflow on Free Flap Survival Area

The influence of using different recipient arteries on free flap survival area has not been well studied. The purpose of the authors' present study was to compare the survival areas of free flaps transferred to different recipient arteries with different blood inflow and to investigate the vascular structural changes in the flaps. The authors developed a free three-territory flap model on the back of a rat. This three-territory flap was elevated based on the thoracodorsal vessels, which were dissected to the axillary vessels. In group 1, the control group (n = 16), the flap was transferred to the abdominal skin defect as a pedicled flap after 60 minutes of clamp ischemia. Groups 2 (n = 24) and 3 (n = 24) were free flap models that were transferred to different recipient vessels. The axillary vessels were anastomosed to the common carotid artery and the external jugular vein in group 2, and to the femoral vessels in group 3. On day 5, evaluation of the survival area of the flap, whole-body angiography, and measurement of arterial inflow to the flap were performed. The greatest mean flap survival was seen in group 2 (94.3 percent). The differences between groups 1 and 2 and groups 2 and 3 were statistically significant. Angiographic studies demonstrated that the second choke zone in group 2 dilated extensively, but in groups 1 and 3, the second choke zone dilated only slightly or remained unopened. The results suggest that augmenting the arterial inflow of a free flap could open the second choke zone and improve flap survival area.

The Use of Transcatheter Superselective Embolization to Treat High Flow Priapism (Arteriocavernosal Fistula) Caused by Straddle Injury

A28-year-old white male presented with persistent partial erections after an industrial straddle injury 5 months earlier. Immediately following the injury the patient experienced moderate perineal and penile pain with extensive bruising and a small laceration on the perineum. There was no evidence of urethral bleeding at the time of injury. The pain eventually subsided but the patient experienced chronic unwanted erections that were approximately 30% to 40% of full rigidity. The patient was unable to achieve an erection adequate for sexual penetration despite a normal libido. He reported no nocturnal erectile activity or urinary complaints. The patient had a supportive spouse. Otherwise all medical history was noncontributory. The patient was a well developed male with a moderate degree of anxiety. Genitourinary examination revealed moderate rigidity and slight tenderness along the left corporal body with a soft glans. The remaining physical examination was unremarkable. Results from the penile color duplex Doppler ultrasound study revealed 60 cm per second inflow in the left cavernosal artery with a corresponding 24 cm per second venous outflow. There was approximately 80% tumescence with 40% rigidity of the penis during the study. Based on history and Doppler study, diagnosis was left high flow priapism with a venous leakage component, and a pudendal arteriogram with possible embolization was scheduled. Superselective injection of the deep penile artery showed a deep penile arteriocavernosal fistula (part A of figure, arrow) causing massive opacification of the corporum cavernosum (part A of figure, arrowhead). To protect the glans penis against inadvertent embolization which could cause loss of sensitivity, a 0.014 platinum guide wire was temporarily placed into the dorsal penile artery (part B of figure, arrow) through a double lumen catheter while embolizing the fistula through the microcatheter advanced through the second lumen. Following superselective embolization of the fistula with AMICAR® enforced autologous blood clot, salutary occlusion of the fistula with no further opacification of the corpora was observed (part C of figure). Upon successful occlusion the penis became soft and rapidly collapsed. High flow priapism is a rare form that occurs with unregulated inflow of arterial blood into the corpora through an arteriocavernosal fistula, and is usually preceded by some form of perineal or penile trauma. Because there is perfusion of well oxygenated blood, high flow priapism (arterial priapism) is nonpainful, nonischemic and not an acute urological emergency. Thus, there is time for initial pharmacological therapeutic modalities. For high flow priapism refractory to this conservative management, radiological transcatheter superselective embolization has become the treatment of choice. 1 Selective embolization can be conducted using a variety of agents including autologous blood clot, metallic microcoils, gel foam and N-butyl cyanoacrylate. 2 Although there is a paucity of data, current theory suggests that embolization should be done with temporary occlusive agents to prevent irreversible changes in erectile function. Thus, autologous blood clots have become the mainstay of treatment for high flow priapism, with long-term followup rates of resolution at 100% and restoration of erectile function at 86%. 3

The Isometric Torque at Which Knee-Extensor Muscle Reoxygenation Stops

We investigated the knee-extensor torque at which reoxygenation (inflow of arterial blood) during an isometric contraction stopped, whether this torque depended on maximal torque capacity (MTC), and whether there were differences among the synergists. Isometric knee-extension torque was measured using a dynamometer with 90 degrees angles in the hip and knee. Maximal voluntary activation (established with superimposed nerve stimulation) was > 90% in the 15 healthy male subjects (20-30 yr). Near-infrared spectroscopy (NIRS) was used to measure changes in muscle oxygenation of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscle during submaximal isometric contractions at intensities of 20-45% MTC with 5% increments, applied in randomized order and divided over 2 d. At each torque, a contraction with an inflated pressure cuff (450 mm Hg), inducing full arterial occlusion, was followed (10 min of rest) by a second contraction without the cuff. MTC ranged from 178 to 348 N.m. The torque at which maximal deoxygenation (all oxygen consumed) during contraction without the cuff became similar (P < 0.05) to the maximal deoxygenation reached with the cuff (indicative for complete occlusion of blood flow during the contraction without the cuff) was significantly higher for the RF (35% MTC) than for both vasti (25% MTC). There was no significant relation between MTC and relative (% MTC) torque at which muscle reoxygenation stopped. Knee-extensor reoxygenation stopped at lower torques than previously reported for blood flow in this muscle, and this occurred at the same % MTC in subjects of different strength but at different % MTC for the different synergists.

Simulation of cerebrospinal fluid transport

The pulsatile nature of the CSF movement is a result of the cardiac-related pulsations in blood volume in cranial region. According to Monro–Kellie Doctrine, the net inflow of arterial blood during systole is compensated by an equal outflow of venous blood and by caudal displacement of the CSF. Knowledge of the distribution of physical properties (compliance, resistance) along the craniospinal system is crucial for understanding of the CSF hydrodynamics. The synthesis of both invasively and non-invasively obtained data is needed. The aim of our project was to develop a lumped-parameter compartment model of the craniospinal system and, in relation to the cardiac-related blood-volume pulsations, to describe its basic hydrodynamic properties. The model consists of six compartments representing major parts of the craniospinal system. Each compartment has its own set of physical properties which describe its behavior. The pressure transmission from head arteries to the brain compartment serves as a source of pulsations. The simulation tightly mimics pressure waves of the CSF and thus the flow characteristics and magnitudes. The fitted compliance of the spinal compartment in our model was two orders higher (9 × 10 −10 m 3/Pa) then the cranial compartment (5.2 × 10 −12 m 3/Pa): only in this adjustment pulsations were present. It makes 99.5% of compliance related to the spinal canal and 0.5% to the intracranial structures. Our fitting showed that this model might be used in medical education as well as in medical practice.

Association between arterial inflow and venous outflow in idiopathic and secondary intracranial hypertension

Twenty-four patients with a clinical diagnosis of idiopathic intracranial hypertension underwent standard magnetic resonance (MR) imaging. On the basis of MR venography, two groups of patients could be identified: (i) one group with an intrinsic venous outflow obstruction (intrinsic); and (ii) a non-intrinsically obstructed (extrinsic) group. MRI flow quantification studies of the cerebral arteries and veins, measuring arterial blood inflow as well as superior sagittal sinus (SSS) and straight sinus (ST) outflow, were performed. The MR venography confirmed that there were 12 intrinsic patients and 12 extrinsic patients. In the intrinsic group, total arterial inflow was normal; however, the SSS outflow was reduced by 35% ( p = 0.0001). Arterial inflow in extrinsic patients was 55% higher than normal ( p = 0.0001); however, the SSS flow was normal. In intrinsic venous outflow obstruction, total cerebral inflow is maintained despite a reduction in outflow. In the idiopathic cases, there was cerebral hyperaemia suggesting a derangement of autoregulation.

State of the Art X: Revascularization Surgery in 2004: L8: Revascularization Surgery in 2004

While there are a large variety of surgical and nonsurgical options, penile revascularization is currently the only modality of therapy that has the potential to permanently cure patients. The overall goal of penile revascularization surgery is to bypass obstructive arterial lesions in the hypogastric‐cavernous arterial bed. The specific objective of the surgery is to increase the cavernosal arterial perfusion pressure and blood inflow in patients with vasculogenic erectile dysfunction secondary to pure arterial insufficiency.

Noninvasive intracranial compliance and pressure based on dynamic magnetic resonance imaging of blood flow and cerebrospinal fluid flow: review of principles, implementation, and other noninvasive approaches

Current techniques for intracranial pressure (ICP) measurement are invasive. All require a surgical procedure for placement of a pressure probe in the central nervous system and, as such, are associated with risk and morbidity. These considerations have driven investigators to develop noninvasive techniques for pressure estimation. A recently developed magnetic resonance (MR) imaging-based method to measure intracranial compliance and pressure is described. In this method the small changes in intracranial volume and ICP that occur naturally with each cardiac cycle are considered. The pressure change during the cardiac cycle is derived from the cerebrospinal fluid (CSF) pressure gradient waveform calculated from the CSF velocities. The intracranial volume change is determined by the instantaneous differences between arterial blood inflow, venous blood outflow, and CSF volumetric flow rates into and out of the cranial vault. Elastance (the inverse of compliance) is derived from the ratio of the measured pressure and volume changes. A mean ICP value is then derived based on a linear relationship that exists between intracranial elastance and ICP. The method has been validated in baboons, flow phantoms, and computer simulations. To date studies in humans demonstrate good measurement reproducibility and reliability. Several other noninvasive approaches for ICP measurement, mostly nonimaging based, are also reviewed. Magnetic resonance imaging-based ICP measurement may prove valuable in the diagnosis and serial evaluation of patients with a variety of disorders associated with alterations in ICP.

Retalho venoso unipediculado transposto comparado ao não transposto: estudo experimental em coelhos

Retalhos venosos são aqueles que apresentam em seu pedículo apenas uma veia, diferente dos retalhos convencionais que são caracterizados por entrada de sangue arterial e saída de sangue venoso. O objetivo deste trabalho foi determinar se a transposição do retalho venoso unipediculado modifica a sua área de sobrevida e vascularização. As orelhas de oito coelhos foram submetidas à realização de retalhos venosos. Dissecou-se um retalho de pele de dois por dois centímetros baseado no pedículo distal da veia marginal anterior. Os retalhos foram divididos em dois grupos: no grupo I(n=8), os retalhos venosos foram levantados e suturados na mesma posição; no grupo II (n=8), os retalhos foram levantados e transpostos 90 graus. Estes dois grupos foram comparados entre si e ao grupo III(n=8), no qual foi realizado enxerto de pele com subcutâneo sobre um leito bem vascularizado. A área média de necrose no grupo I (6,5%) foi significativamente menor que no grupo II (43,75%), e as áreas de necrose dos grupos I e II foram significativamente menor do que no grupo III (88,75%). O estudo angiográfico não mostrou alterações no padrão vascular comparando-se os grupos I e II. A veia marginal anterior foi importante para a sobrevida do retalho. Houve uma maior área de necrose do grupo II, em que foi realizada transposição, em relação ao grupo I.

Anatomical and Physiological Studies on the Aqueous Sinus Artery of the Pigeon Eye

Purpose: To test the hypothesis that ischemia of the Schlemm's canal endothelium is involved in the control of intraocular pressure (IOP). Methods: Experiments were conducted on pigeons. The course of the aqueous sinus and the aqueous sinus artery was determined by examining serial sections and the distribution of polymerized resin in the limbal region of the pigeon eye. Ischemia was produced by blocking two major arteries to the aqueous sinus artery and then determining the effect on the IOP. Results: The anatomy and course of the pigeon aqueous sinus and aqueous sinus artery indicated that they are homologous to the human Schlemm's canal and Schlemm's canal artery, respectively. When the arterial inflow to the aqueous sinus artery was blocked by laser treatment, injected resin was absent in the artery but a small amount invaded the aqueous sinus. Blockage of the two major arteries to the aqueous sinus artery did not alter the IOP. Conclusions: The similarity of the pigeon aqueous sinus and aqueous sinus artery to the human Schlemm's canal and Schlemm's canal artery indicates that the pigeon eye can be used to study the relationship between ischemia of the endothelial meshwork cells and IOP. The lack of a change in IOP in pigeons after ischemia induction was probably the result of anastomotic arterial blood inflow to the aqueous sinus directly, and thus ischemia was not produced by blocking the two major arteries to the aqueous sinus artery.

Contribution of mathematical modelling to the interpretation of bedside tests of cerebrovascular autoregulation

OBJECTIVESCerebral haemodynamic responses to short and longlasting episodes of decreased cerebral perfusion pressure contain information about the state of autoregulation of cerebral blood flow. Mathematical simulation may help to elucidate...

Colored microsphere technique as a new method for quantitative-multiple estimation of regional hepatic and portal blood flow

A new method for multiple, quantitative estimation of regional splanchnic blood flow is presented which overcomes all the limitations of the radionuclide microsphere technique. By direct comparison of two methods, i.e., simultaneous blood flow measurement with radionuclide-labeled and colored microspheres, it was shown that the quality of flow measure was quite similar. Simultaneous measurement using paired radionuclide-labeled microspheres yielded an excellent correlation between both values of r = 0.997, a variability of 4.58 +/- 3.84% and a SEE-value of 0.167 ml/g/min. The colored microsphere technique produced corresponding values with r = 0.998, a variability of 5.94 +/- 7.80% and a SEE-value of 0.212 ml/g/min (n.s.). This is also shown for five different abdominal organs and tissues with quite different flow rates under normal physiological conditions. Thus, the colored microsphere technique is a suitable experimental method for making multiple and quantitative measures of the nutritive blood flow through splanchnic organs and tissues and yields values of arterial blood inflow into the liver and into the circulatory bed which is drained by the portal vein.

The arterialised venous flap: experimental studies and a clinical case

It is accepted that small arterialised venous flaps (AVF) can survive on a recipient bed with poor blood supply but survival of larger flaps is not always satisfactory. Possible reasons for this include the flap anatomy, particularly the pattern of the venous network, or factors at the recipient site. To investigate the possible factors in the flap design and the recipient site of an arterialised venous flap, we studied the relationship between (1) size of the artery used to arterialise the flap at the recipient site and the survival rate and (2) the number of draining veins and the survival rate, using rabbit ear skin flap models. Our results suggest that AVFs may become necrotic in the presence of a relative excess of arterial blood inflow, and that two exit veins are more effective than one. We also report a case where a 10 × 15 cm sized free AVF harvested from the lower extremity survived on the forearm.

Influence of lung volume and left atrial pressure on reverse pulmonary venous blood flow

Infarction of the lung is uncommon even when both the pulmonary and the bronchial blood supplies are interrupted. We studied the possibility that a tidal reverse pulmonary venous flow is driven by the alternating distension and compression of alveolar and extra-alveolar vessels with the lung volume changes of breathing and also that a pulsatile reverse flow is caused by left atrial pressure transients. We infused SF6, a relatively insoluble inert gas, into the left atrium of anesthetized goats in which we had interrupted the left pulmonary artery and the bronchial circulation. SF6 was measured in the left lung exhalate as a reflection of the reverse pulmonary venous flow. No SF6 was exhaled when the pulmonary veins were occluded. SF6 was exhaled in increasing amounts as left atrial pressure, tidal volume, and ventilatory rates rose during mechanical ventilation. SF6 was not excreted when we increased left atrial pressure transients by causing mitral insufficiency in the absence of lung volume changes (continuous flow ventilation). Markers injected into the left atrial blood reached the alveolar capillaries. We conclude that reverse pulmonary venous flow is driven by tidal ventilation but not by left atrial pressure transients. It reaches the alveoli and could nourish the alveolar tissues when there is no inflow of arterial blood.

The anatomy of erection.

Erection is due to a neurovascular mechanism: an inflow of arterial blood and an obstruction of venous return. The direction of this mechanism is of neurologic origin: (1) control of the smooth muscle tissue of the corpora cavernosa by the autonomic system controlled by reflex centers in the cord or cortical centers accessible to multiple (visual) stimuli (2) control of the perineal muscles by the somatic system. Tumescence is due to a reduction in the alpha-sympathetic tonus of the cavernous tissue permitting influx of arterial blood, and to decreased venous flow from compression of the subalbugineal venous network against the tunica albuginea of the corpus cavernosum. Once this obstruction to the venous return has been achieved, the arterial flow in the corpora cavernosa decreases but persists; the arterial blood in the corpora cavernosa is renewed and not shut off. Rigidity is due to an increase in intracavernous arterial pressure simultaneous with contraction of the perineal muscles (ischiocavernosus) under the somatic control of the pudendal nerve.

Spectrophotometric monitoring of arterial oxygen saturation in the fingertip.

A noninvasive oximeter that analyses the oxygen saturation of arterial blood in the fingertip is described. The light, after attenuating the infrared portion to avoid thermal injury, is applied to the fingertip through an optical transmitter made of glass fibres. The transmitted light is transferred to an optical reception system where a spectrophotometric determination of oxygen saturation is performed. The determination is performed by considering only the change in the attenuation of light caused by the inflow of arterial blood into the fingertip. The correlation between the oxygen saturation measured with the present instrument (y) and that with the blood-gas method (x), was y=0·907x+8·592 with a standard deviation and a correlation coefficient of 0·135% and 0·983, respectively. The reproducibility was assessed in a healthy subject by measuring the oxygen saturation repeatedly 60 times. The mean saturation was 95·82±0·675% (mean±standard deviation). The instrument has been useful in monitoring arterial oxygenation in patients with respiratory failure in our intensive-care unit. One of the disadvantages of the instrument is that the measurement is interrupted when the fingertip changes its position against the light beam.

Effects of ethacrynic acid on vascular resistance, metabolism, and electrolyte flux in the canine gracilis muscle.

The effects of intra-arterial ethacrynic acid (EA) on vascular resistance, metabolism, and electrolyte flux was studied in the isolated denervated canine gracilis muscle perfused with a constant inflow of arterial blood. Skeletal muscle vascular resistance was markedly reduced from baseline by 25-min infusions of EA producing blood concentrations of 10−3 M but not at concentrations of 10−5 M. There were no consistent alterations in the uptake of glucose, production of lactate, or flux of potassium in the gracilis muscle during the drug infusions or 45 min postinfusion period. Venous osmolality did not change. However, the arterio venous difference for oxygen saturation across this skeletal muscle was significantly reduced by EA treatment suggesting that oxygen utilization had been inhibited. Thus, EA has a direct vasodilatory effect which is independent of measurable changes in gracilis muscle electrolyte flux or metabolism other than a possible reduction in oxygen uptake or utilization by this muscle.

Comparative effects of ethacrynic acid, furosemide, and diazoxide in the perfused dog hindlimb.

The vasodilator effects of intravenous ethacrynic acid (EA), furosemide (F), and diazoxide (DZ) were compared in the hindlimb of anesthetized anephric dogs, perfused with a constant inflow of arterial blood. A dose-response relationship was demonstrated for all three agents. The curves for EA and F were parallel and relatively flat, with EA being 10 times more potent than F in producing vasodilatation of the perfused limb. The dose–response for DZ was steep and the maximal vasodilator response observed at the lowest dose of DZ (5 mg/kg) did not differ from that at the highest doses of EA (10 mg/kg) or F (100 mg/kg). The maximal vasodilator effect of DZ in the perfused hindlimb occurred within 2 min after intravenous administration. After the higher doses of F there was a transitory vasodilator effect within 2 min but the maximal and more persistent effect was not observed until much later. The mean time for maximal effect was 40 min for EA, 46 min for F, and 2 min for DZ. The time course of vasodilator effect and maximal observed effect for EA and F was not altered by intraarterial administration nor by sympathetic decentralization of the perfused hindlimb. We conclude that F, like EA, has a direct vasodilating effect on peripheral arterioles and both EA and F probably act by a different mechanism than DZ.

Plethysmographic and rheographic investigation of the effector structure of vascular reflexes

Peripheral vascular responses in the orienting reflex were studied by comparing changes in the digital plethysmogram and in the rheographic inflow index (RII), the value of which was obtained by summation of the amplitudes of the rheographic waves (of neighboring digits) over a certain period of time (measured in minutes). The decrease in blood filling in the orienting reflex may take place through the participation of at least two predominant mechanisms: a decrease in the inflow of arterial blood and an increase in the venous outflow. This can be observed in the same individual during the same investigation. Facts characterizing the behavior of the cerebral vessels (as shown by rheoencephalography) involved in the orienting reflex are also described. These demonstrate that it has certain features in common with the peripheral circulation, but also features of independence.