Intravascular streaming and variable delivery to brain following carotid artery infusions in the Sprague-Dawley rat

Case Series of Precision Delivery of Methylprednisolone in Pediatric Inflammatory Bowel Disease: Feasibility, Clinical Outcomes, and Identification of a Vasculitic Transcriptional Program

Systemic steroid exposure, while useful for the treatment of acute flares in inflammatory bowel disease (IBD), is associated with an array of side effects that are particularly significant in children. Technical advancements have enabled locoregional intraarterial steroid delivery directly into specific segments of the gastrointestinal tract, thereby maximizing tissue concentration while limiting systemic exposure. We investigated the feasibility of intraarterial steroid administration into the bowel in a cohort of nine pediatric patients who had IBD. This treatment approach provided symptom relief in all patients, with sustained relief (>2 weeks) in seven out of nine; no serious adverse effects occurred in any patient. In addition, we identified patterns of vascular morphologic changes indicative of a vasculopathy within the mesenteric circulation of inflamed segments of the bowel in pediatric patients with Crohn's disease, which correlated with disease activity. An analysis of publicly available transcriptomic studies identified vasculitis-associated molecular pathways activated in the endothelial cells of patients with active Crohn's disease, suggesting a possible shared transcriptional program between vasculitis and IBD. Intraarterial corticosteroid treatment is safe and has the potential to be widely accepted as a locoregional approach for therapy delivery directly into the bowel; however, this approach still warrants further consideration as a short-term "bridge" between therapy transitions for symptomatic IBD patients with refractory disease, as part of a broader steroid-minimizing treatment strategy.

Effect of methylprednisolone on experimental brain edema in rats - own experience reviewed

Brain edema - a frequently fatal pathological state in which brain volume increases resulting in intracranial pressure elevation - can result from almost any insult to the brain, including traumatic brain injury. For many years, the objective of experimental studies was to find a method to prevent the development of brain edema at the onset. From this perspective, the use of methylprednisolone (MP) appears promising. High molecular MP (MW>50 kDa) can be incorporated into the brain - in the conditions of the experimental model - either by osmotic blood-brain barrier disruption (BBBd) or during the induction of cellular edema by water intoxication (WI) - a condition that increases the BBB permeability. The time window for administration of the MP should be at the earliest stages of edema. The neuroprotective effect of MP on the permeability of cytoplasmatic membranes of neuronal populations was proved. MP was administrated in three alternative ways: intraperitoneally during the induction of cytotoxic edema or immediately after finishing cytotoxic edema induction in a dose of 100 mg/kg b.w.; into the internal carotid artery within 2 h after finishing cytotoxic edema induction in a dose of 50 mg/kg b.w.; into internal carotid artery 10 min after edema induction by BBBd in a dose of 50 mg/kg b.w.

Single-cell, high-throughput analysis of cell docking to vessel wall

Therapeutic potential of mesenchymal stem cells (MSCs) has been reported consistently in animal models of stroke, with mechanism mainly through immunomodulation and paracrine activity. Intravenous injection has been a prevailing route for MSCs administration, but cell quantities needed when scaling-up from mouse to human are extremely high putting into question feasibility of that approach. Intra-arterial delivery directly routes the cells to the brain thus lowering the required dose. Cell engineering may additionally improve cell homing, further potentiating the value of intra-arterial route. Therefore, our goal was to create microfluidic platform for screening and fast selection of molecules that enhance the docking of stem cells to vessel wall. We hypothesized that our software will be capable of detecting distinct docking properties of naïve and ITGA4-engineered MSCs. Indeed, the cell flow tracker analysis revealed positive effect of cell engineering on docking frequency of MSCs (42% vs. 9%, engineered vs. control cells, p < 0.001). These observations were then confirmed in an animal model of focal brain injury where cell engineering resulted in improved homing to the brain. To conclude, we developed a platform to study the docking of cells to the vessel wall which is highly relevant for intraarterial cell targeting or studies on neuroinflammation.

Revisiting intra-arterial drug delivery for treating brain diseases or is it "déjà-vu, all over again"?

For over six decades intra-arterial (IA) drugs have been sporadically used for the treatment of lethal brain diseases. In recent years considerable advance has been made in the IA treatment of retinoblastomas, liver and locally invasive breast cancers, but relatively little progress has been made in the treatment of brain cancers. High resting blood flow and the presence of the blood-brain barrier (BBB), makes IA delivery to the brain tissue far more challenging, compared to other organs. The lack of advance in the field is also partly due to the inability to understand the complex pharmacokinetics of IA drugs as it is difficult to track drug concentrations in sub-second time frame by conventional chemical methods. The advances in optical imaging now provide unprecedented insights into the pharmacokinetics of IA drug and optical tracer delivery. Novel delivery methods, improved IA drug formulations, and optical pharmacokinetics, present us with untested paradigms in pharmacology that could lead to new therapeutic interventions for brain cancers and stroke. The object of this review is to bring into focus the current practice, problems, and the potential of IA drug delivery for treating brain diseases. A concerted effort is needed at basic sciences (pharmacology and drug imaging), and translational (drug delivery techniques and protocol development) levels by the interventional neuroradiology community to advance the field.

A simple method to ensure homogeneous drug distribution during intrarenal infusion

Intrarenal drug infusion plays an important role in renal experimental research. Laminar flow of the blood can cause streaming and inhomogeneous intrarenal distribution of infused drugs. We suggest a simple method to achieve a homogeneous intravascular distribution of drugs infused into the renal artery of anesthetized rats. The method employs a multiple sidehole catheter inserted into the renal artery, which enables an efficient drug mixing with the arterial blood. To verify the efficiency of this method, we use laser speckle imaging and renal artery flowmetry. The results show that, compared with the conventional single-hole catheter, the multiple sidehole catheter provides a more uniform drug distribution and a homogenous vascular response on the surface of the kidney.

Localization and mobility of glucose-coated gold nanoparticles within the brain

Aim: To identify the localization of glucose-coated gold nanoparticles within cells of the brain after intravascular infusion which may point to the mechanism by which they cross the blood–brain barrier. Materials & methods: Tissue distribution of the nanoparticles was measured by inductively-coupled-mass spectrometry and localization within the brain by histochemistry and electron microscopy. Results & conclusion: Nanoparticles were identified within neurons and glial cells more than 10 μm from the nearest microvessel within 10 min of intracarotid infusion. Their distribution indicated movement across the endothelial cytosol, and direct transfer between cells of the brain. The rapid movement of this class of nanoparticle (<5 nm) into the brain demonstrates their potential to carry therapeutic biomolecules or imaging reagents.

Reassessing the Role of Intra-Arterial Drug Delivery for Glioblastoma Multiforme Treatment

Effective treatment for glioblastoma (GBM) will likely require targeted delivery of several specific pharmacological agents simultaneously. Intra-arterial (IA) delivery is one technique for targeting the tumor site with multiple agents. Although IA chemotherapy for glioblastoma (GBM) has been attempted since the 1950s, the predicted benefits remain unproven in clinical practice. This review focuses on innovative approaches to IA drug delivery in treating GBM. Guided by novel in vitro and in vivo optical measurements, newer pharmacokinetic models promise to better define the complex relationship between background cerebral blood flow and drug injection parameters. Advanced optical technologies and tracers, unique nanoparticles designs, new cellular targets, and rational drug formulations are continuously modifying the therapeutic landscape for GBM. Personalized treatment approaches are emerging; however, such tailored approaches will largely depend on effective drug delivery techniques and on the ability to simultaneously deliver multidrug regimens. These new paradigms for tumor-selective drug delivery herald dramatic improvements in the effectiveness of IA chemotherapy for GBM. Therefore, within this context of so-called "precision medicine," the role of IA delivery for GBM is thoroughly reassessed.

Cationic surface charge enhances early regional deposition of liposomes after intracarotid injection

Rapid first pass uptake of drugs is necessary to increase tissue deposition after intraarterial (IA) injection. Here we tested whether brain tissue deposition of a nanoparticulate liposomal carrier could be enhanced by coordinated manipulation of liposome surface charge and physiological parameters, such as IA injection during transient cerebral hypoperfusion (TCH). Different degrees of blood-brain barrier disruption were induced by focused ultrasound in three sets of Sprague-Dawley rats. Brain tissue retention was then compared for anionic, cationic, and charge-neutral liposomes after IA injection combined with TCH. The liposomes contained a non-exchangeable carbocyanine membrane optical label that could be quantified using diffuse reflectance spectroscopy (DRS) or visualized by multispectral imaging. Real-time concentration-time curves in brain were obtained after each liposomal injection. Having observed greater tissue retention of cationic liposomes compared to other liposomes in all three groups, we tested uptake of cationic liposomes in C6 tumor bearing rats. DRS and multispectral imaging of postmortem sections revealed increased liposomal uptake by the C6 brain tumor as compared to non-tumor contralateral hemisphere. We conclude that regional deposition of liposomes can be enhanced without BBB disruption using IA injection of cationic liposomal formulations in healthy and C6 tumor bearing rats.

Selective intra-arterial administration of ¹⁸F-FDG to the rat brain -- effects on hemispheric uptake

Introduction

The purpose of this study was to investigate the radioligand uptake and iodine contrast distribution in the intra- and extracranial circulation of the rat, after intra-arterial injections to the common carotid artery and different parts of the internal carotid artery.

Methods

All animal experiments were carried out in accordance with Karolinska Institutet’s guidelines and were approved by the local laboratory animal ethics committee. We used clinical neurointerventional systems to place microcatheters in the extra- or intracranial carotid artery of 15 Sprague–Dawley rats. Here, injection dynamics of iodine contrast was assessed using digital subtraction angiography. Maintaining the catheter position, the animals were placed in a micro PET and small-animal positron emission tomography (PET) was used to analyze injections [2-¹⁸F]-2-fluoro-2-deoxy-d-glucose (¹⁸F-FDG).

Results

Microcatheters had to be placed in the intracranial carotid artery (iICA) for the infusate to distribute to the brain. Selective injection via the iICA resulted in a 9-fold higher uptake of ¹⁸F-FDG in the injected hemisphere (p < 0.005) compared to both intravenous and more proximal carotid artery injections. Furthermore, selective injection gave a dramatically improved contrast between the brain and extracranial tissue.

Conclusion

Intra-arterial injection increases the cerebral uptake of a radiotracer dramatically compared to systemic injection. This technique has potential applications for endovascular treatment of malignancies allowing intra-interventional modifications of injection strategy, based on information on tumor perfusion and risk to surrounding normal parenchyma. Furthermore the technique may increase diagnostic sensitivity and avoid problems due to peripheral pharmacological barriers and first passage metabolism of labile tracers.

Treatment of recurrent glioblastoma with intra-arterial BCNU [1, 3-bis (2-chloroethyl)-1-nitrosourea]

Contemporary therapies for patients with glioblastomas remain marginally efficient, and recurrence following surgery, radiation therapy and adjuvant chemotherapy is practically universal. The major obstacles to the successful use of chemotherapy for CNS tumors are the drug delivery to the tumor site and the infusion of chemotherapeutic agents directly into the arterial supply of a tumor. The latter could provide a pharmacokinetic advantage by enhancing drug delivery to the tumor. Sixteen patients with recurrent unilateral glioblastomas treated with intra-arterial BCNU were evaluated retrospectively. During the infusion, eleven patients referred pain in the ipsilateral eye, five patients were nauseated, three reported headache, one patient presented mental confusion, while two presented focal signs. There were two deaths during the course of therapy. Four patients achieved temporary clinical improvement, seven showed disease stability, and three presented clinical deterioration. The median total survival time was 87.9 weeks. Unilateral vision loss and focal signs were observed as delayed complications of this treatment. This study has confirmed previous reports indicating that arterial chemotherapy is clearly not curative, and presents serious toxicity. Only through a randomized prospective study performed in a large series of patients can the questions concerning survival period increment be answered properly

Intracarotid delivery of drugs: the potential and the pitfalls

The major efforts to selectively deliver drugs to the brain in the past decade have relied on smart molecular techniques to penetrate the blood-brain barrier, whereas intraarterial drug delivery has drawn relatively little attention. Meanwhile, rapid progress has been made in the field of endovascular surgery. Modern endovascular procedures can permit highly targeted drug delivery by the intracarotid route. Intracarotid drug delivery can be the primary route of drug delivery or it could be used to facilitate the delivery of smart neuropharmaceuticals. There have been few attempts to systematically understand the kinetics of intracarotid drugs. Anecdotal data suggest that intracarotid drug delivery is effective in the treatment of cerebral vasospasm, thromboembolic strokes, and neoplasms. Neuroanesthesiologists are frequently involved in the care of such high-risk patients. Therefore, it is necessary to understand the applications of intracarotid drug delivery and the unusual kinetics of intracarotid drugs.

Intra-arterial drug delivery: a concise review

The therapeutic potential of intra-arterial (IA) drug delivery to the brain has received limited attention in the last decade. In the 1980s, efforts to treat brain tumors with IA chemotherapy, the leading application of this technology, yielded modest results. Poor control of tissue drug concentrations and the potential risk of permanent neurologic injury further prevented the wider use of IA drugs. Yet, IA drugs were anecdotally used for treating a wide spectrum of brain diseases. Recent advances in endovascular technology and the increased safety of angiographic procedures now compel us to reevaluate IA drug delivery. This review describes the pharmacologic principles, applications, and pitfalls of IA drug delivery to the brain.

Bolus configuration affects dose requirements of intracarotid propofol for electroencephalographic silence

We hypothesized that an intracarotid bolus injection of propofol to produce electroencephalographic (EEG) silence would require a smaller dose of the drug compared with the continuous infusion of the drug. Furthermore, the bolus propofol dose will be a function of the bolus characteristics in each bolus (mass/volume). We compared the dose requirements of intracarotid propofol needed to maintain EEG silence when delivered as bolus injections to continuous infusions in rabbits. Subsequently, we compared whether four different bolus characteristics (concentration and volume) of propofol (0.33% x 0.1 mL, 0.33% x 0.3 mL, 1% x 0.1 mL, and 1% x 0.3 mL) affected the dose required to produce EEG silence. We found that the infusion rate of propofol required to sustain EEG silence was three-fold larger than the dose required by bolus injections, 22.8 +/- 11.9 vs 6.2 +/- 2.9 mL/h for infusion versus bolus, respectively (n = 7, P < 0.004). Furthermore, during bolus injection, the doses of propofol required to produce EEG silence were a direct function of the bolus volume and the mass of drug in each bolus, total dose = 3.6 + 29 x mg/bolus, n = 32, r = 0.85. For maximum regional effects of the bolus intracarotid drug injection, the bolus characteristics (volume and drug concentration) have to be optimized.

Reducing cerebral blood flow increases the duration of electroencephalographic silence by intracarotid thiopental

The effects of IV anesthetics are enhanced by increased cerebral blood flow (CBF) because of a greater delivery of drugs to the brain. In contrast, mathematical simulations suggest that a decrease in CBF, by increasing regional drug uptake and decreasing drug washout, enhances the efficacy of intraarterial drugs. We hypothesized that administrating intracarotid anesthetics during cerebral hypoperfusion will significantly prolong the duration of electroencephalographic (EEG) silence. We tested our hypothesis on New Zealand White rabbits. In the first group of 7 animals, we observed that decreasing CBF by approximately 70% attenuated, but did not abolish, EEG activity. Subsequently, 9 animals received 3 intracarotid injections of 3 mg of thiopental (thiopental-1, thiopental + hypoperfusion, and thiopental-2). The first and third injections were made under physiological conditions. The second drug injection was made during cerebral hypoperfusion. Compared with injection of thiopental-1 and -2, thiopental + hypoperfusion resulted in a profound increase in EEG silence (from 45 +/- 5 and 67 +/- 27 s, to 206 +/- 46 s, respectively, n = 9, P < 0.0001). The EEG recovery profile was similar during all three thiopental challenges. The study suggests that modulation of CBF is an important tool for enhancing intraarterial drug delivery to the brain.

A vibrator prevents streaming during close-arterial infusion into the kidney

Close-arterial infusion of test substances allows one to study the responses of a selected vascular bed without inducing confounding systemic effects. Unfortunately, laminar flow patterns within the artery cause streaming of the injected factor, so that distribution within the target organ is not homogeneous. We describe a reliable method of overcoming these problems. Specifically, we attach a vibrator (i-Vibe egg) to the syringe containing the test substance. We showed that, without vibration, infusion of a solution of Evans blue (0.5% wt/vol) results in uneven distribution of the dye in the kidney. Vibration of the syringe during infusion allows for uniform coloration of the kidney surface. There is also functional improvement of drug distribution during vibration. Renal blood flow was measured during intrarenal infusion of phenylephrine (150 μl, 0.05–0.5 μg). Vibration caused a significant leftward shift in the dose-response curve, i.e., the phenylephrine-induced reduction in renal blood flow was enhanced by vibration. This cheap, simple method for ensuring adequate mixing of intra-arterially infused substances will facilitate not only the study of renal function in the rat but also infusion of test and therapeutic substances into other organs.

Mixing during intravertebral arterial infusions in an in vitro model

Regional delivery of drugs can offer a pharmacokinetic advantage in the treatment of localized tumors. One method of regional delivery is by intra-arterial infusion into the basilar/vertebral artery network that provides local access to infratentorial tumors, which are frequent locations of childhood brain cancers. Proper delivery of drug by infused solutions requires adequate mixing of the infusate at the site of infusion within the artery lumen. Our mixing studies with an in vitro model of the vertebral artery network indicate that streaming of drug solution is likely to occur at low, steady infusion rates of 2 ml/min. Streaming leads to maldistribution of drug to distal perfused brain regions and may result in toxic levels in some regions while concurrently yielding subtherapeutic levels in adjacent regions. According to our model findings, distribution to both brain hemispheres is not likely following infusion into a single vertebral artery even if the infusate is well-mixed at the infusion site. This outcome results from the unique fluid flow properties of two converging channels, which are represented by the left and right vertebral branches converging into the basilar. Fluid in the model remains stratified on the side of the basilar artery served by the infused vertebral artery. Careful thought and planning of the methods of intravertebral drug infusions for treating posterior fossa tumors are required to assure proper distribution of the drug to the desired tissue regions. Improper delivery may be responsible for some noted toxicities or for failure of the treatments.

Effect of hyperosmotic solutions on salt excretion and thirst in rats

We investigated urinary changes and thirst induced by infusion of hyperosmotic solutions in freely moving rats. Intracarotid infusions of 0.3 M NaCl (4 ml/20 min, split between both internal carotid arteries) caused a larger increase in excretion of Na(+) and K(+) than intravenous infusions, indicating that cephalic sensors were involved in the response to intracarotid infusions. Intravenous and intracarotid infusions of hyperosmotic glycerol or urea (300 mM in 150 mM NaCl) had little or no effect, suggesting the sensors were outside the blood-brain barrier (BBB). Intracarotid infusion of hypertonic mannitol (300 mM in 150 mM NaCl) was more effective than intravenous infusion, suggesting that cell volume rather than Na(+) concentration of the blood was critical. Similarly, intracarotid infusion (2 ml/20 min, split between both sides), but not intravenous infusion of hypertonic NaCl or mannitol caused thirst. Hyperosmotic glycerol, infused intravenously or into the carotid arteries, did not cause thirst. We conclude that both thirst and electrolyte excretion depend on a cell volume sensor that is located in the head, but outside the BBB.

A clinical role for 99mTc-HMPAO SPECT in the investigation of dementia?

OBJECTIVES

To provide the clinician with a guide to the clinical utility of 99mTc-HMPAO single photon emission computed tomography (SPECT) and to the interpretation of specific test results in the differential diagnosis of dementia.

METHODS

Three hundred and sixty three patients with dementia were studied prospectively for a median three (range 1-6) years and classified into disease groups on the basis of established clinical criteria. The degree to which different patterns of cerebral blood flow (CBF) abnormality found on 99mTc-HMPAO SPECT imaging at the time of initial patient presentation modified clinical diagnoses was determined by calculating the likelihood ratios for pairwise disease group comparisons. The optimal clinical usage of 99mTc-HMPAO SPECT was determined by calculating the percentage of significant test results for each pairwise disease group comparison.

RESULTS

Bilateral posterior CBF abnormality was found to significantly increase the odds of a patient having Alzheimer's disease as opposed to vascular dementia or frontotemporal dementia. Bilateral anterior CBF abnormality significantly increased the odds of a patient having frontotemporal dementia as opposed to Alzheimer's disease, vascular dementia, or Lewy body disease. "Patchy" CBF changes significantly increased the odds of a patient having vascular dementia as opposed to Alzheimer's disease. Unilateral anterior, unilateral anterior plus unilateral posterior, and generalised CBF abnormality failed to contribute to the differentiation of any of these forms of dementia.

CONCLUSIONS

99mTc-HMPAO SPECT was found to be most useful in distinguishing Alzheimer's disease from vascular dementia and fronto temporal dementia, and least useful in differentiating between Alzheimer's disease and Lewy body disease, and between vascular dementia, frontotemporal dementia, and progressive aphasia. It is suggested that CBF SPECT should be used selectively and as an adjunct to clinical evaluation and CT.

Permeability change and brain tissue damage after intracarotid administration of cisplatin studied by double-tracer autoradiography in rats

The present study was designed to find the reliable parameter(s) for the detection of early neurotoxicity following intracarotid (IC) administration of cisplatin. IC administration was performed for 60 minutes in female Wistar rats derived into four groups according to the dose given (1 mg, 1.2 mg, and 1.5 mg of cisplatin, and normal saline in control rats). Blood-brain barrier (BBB) permeability and local cerebral blood flow (LCBF) were measured by a double-tracer autoradiography technique using 1-[14C]-alpha-aminoisobutyric acid (14C-AIB) and 4-[18F] fluoroantipyrine (18F-FAP), respectively. Blood chemistry and neuropathology were also examined. BBB permeability was increased only on the ipsilateral side. This increase was dose-dependent, preceded the brain necrosis, and was statistically significant in the hypothalamus (1.2 mg group), auditory cortex and caudoputamen (1.5 mg group). Renal dysfunction was often observed. The changes in the LCBF did not occur until brain necrosis was noticeable. These findings demonstrate that the increase in the BBB permeability provides a sensitive and reliable indication of an early toxicity to brain tissue following IC administration of cisplatin.

Effect of phorbol myristate acetate on cerebral blood flow in normal and neutrophil-depleted rats

BACKGROUND AND PURPOSE

Recent evidence suggests a possible role for leukocytes in ischemic brain injury. This study examined the effect of activation of endogenous circulating leukocytes on cerebral blood flow in normal and neutrophil-depleted rats.

METHODS

Leukocytes were activated by rapid injection of either 50 micrograms/kg phorbol 12-myristate 13-acetate, a protein kinase C activator, or an equimolar amount of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine, into the right carotid artery. Control rats received an equal volume of dimethyl sulfoxide in saline vehicle. H2-clearance cerebral blood flow was measured in each of the three groups and in vinblastine-treated, neutrophil-depleted rats after carotid artery injection of phorbol.

RESULTS

Phorbol 12-myristate 13-acetate dramatically decreased circulating leukocyte and platelet counts from 5 to 120 minutes after infusion and decreased regional cerebral blood flow in the ipsilateral parietal cortex from a baseline of 119 +/- 14 mL.min-1.100 g-1 (mean +/- SEM) to 49 +/- 5 mL.min-1.100 g-1 at 30 minutes (P < .05). Decreased flow persisted for the 2-hour study. Neither N-formyl-methionyl-leucyl-phenylalanine or vehicle had an effect on cerebral blood flow. In the neutrophil-depleted rats the initial decrease in cerebral blood flow at 30 and 60 minutes after infusion of phorbol was observed, but cerebral blood flow was restored to 70% to 80% of its baseline value (P > .05 versus baseline) by 90 to 120 minutes.

CONCLUSIONS

The early phorbol 12-myristate 13-acetate-induced decrease in cerebral blood flow may be due to the effects of protein kinase C activation on vascular smooth muscle or on platelet aggregation, whereas the persistent decrease in cerebral blood flow appears to be mediated in part by neutrophil activation.

Delivery of a novel nitrosourea, MCNU, to the brain tissue in glioma-bearing rats. Intracarotid versus intravenous infusion

We observed the tissue delivery of a novel water-soluble nitrosourea, 1-(2-chloroethyl)-3-(methyl-alpha-D-glucopyranos-6-yl)-1-nitros our ea (MCNU) in rats bearing experimental brain tumors by conducting autoradiography on all. Prior to this study, the development of a streaming phenomenon was ascertained (and thus finding the optimum velocity for intra-arterial infusion) by 14C-iodoantipyrine (IAP) autoradiography. Furthermore, a single pass extraction value of MCNU was measured. At an arterial infusion rate of 0.2 ml/min., the streaming phenomenon was recognized but the tracer was fairly evenly distributed at a rate of 1.0 ml/min. On the other hand, the single pass extraction value for MCNU was 0.18 +/- 0.036 (mean +/- S.D., n = 3, under pentobarbital anesthesia). It was suggested that MCNU is very unlikely to be transported into the normal rat brain. We conducted 14C-MCNU autoradiography to observe tissue distribution of MCNU following its intra-arterial and intravenous infusions in a brain tumor model using rats. The normal side (the side where no infusions were given) and the cerebral cortex at the side affected by the tumor (the side where the infusion was given) showed hardly any uptake of 14C-MCNU in both the intra-arterial and intravenous infusion groups. The tumorous section was divided into the periphery and the center to measure tissue concentration of the tracer in each section. Compared against the cortical section, the periphery and the center showed significant increases in the concentration (approximately 11 to 15 times and 3 to 7 times, respectively, the figure for the cortical region) for both the intra-arterial and intravenous groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intracarotid infusion of neuropeptide Y on cerebral blood flow in rats

Neuropeptide Y (NPY) was continuously administered to Wistar rats intracarotidly via the external carotid artery and local cerebral blood flow (LCBF) was measured by a quantitative autoradiography using [14C]iodoantipyrine. A remarkable reduction in LCBF was observed in the NPY infused hemisphere. This depression was irregular and was particularly evident in the hippocampus, selective thalamic nuclei and the cerebral cortex.

Oleic acid reversibly opens the blood-brain barrier

This study examined the effect of intracarotid oleic acid infusion on blood-brain barrier permeability. Oleic acid was infused for 30 s at a rate of 6 ml/min into the right internal carotid artery at concentrations of 10(-6), 10(-5), 2 x 10(-5) and 5 10(-5) M. Extensive Evans blue-albumin extravasation was observed 15 min after the administration of 2 x 10(-5) M oleic acid. The permeability surface area product for alpha-aminoisobutyric acid (AIB), determined 1-11 min following the infusion of oleic acid was increased 10-fold following infusion of 10(-5) M oleic acid and 20-fold following the administration of 5 x 10(-5) M oleate. The blood-brain barrier opening to AIB proved to be reversible 80-90 min after the infusion of 2 x 10(-5) M oleic acid. The possible mechanisms of the oleic acid effect are discussed.

Intravascular streaming during carotid artery infusions. Demonstration in humans and reduction using diastole-phased pulsatile administration

Intra-arterial carotid artery chemotherapy for malignant gliomas is limited by focal injuries to the eye and brain which may be caused by poor mixing of the drug with blood at the infusion site. This inadequate mixing can be eliminated in animal models with diastole-phased pulsatile infusion (DPPI) which creates 1-ml/sec spurts during the slow blood flow phase of diastole. Before treatment with intracarotid cisplatin, 10 patients with malignant gliomas were studied to determine whether intravascular streaming occurs after intracarotid infusion in humans, and if so, if it is reduced with DPPI. Regional cerebral blood flow (rCBF) studies were performed by intravenous injection of H2(15)O and positron emission tomography. This was followed by supra- or infraophthalmic internal carotid artery (ICA) injections of H2(15)O with either continuous infusion or DPPI. Local H2(15)O concentration in the brain was determined and the images of radiotracer distribution in the continuous infusion and DPPI studies were compared to the rCBF images. Intravascular streaming of the infusate was identified by a heterogeneous distribution of the infused H2(15)O in brain compared to rCBF. Extensive and variable intravascular streaming occurred in three patients who received infusions into the supraophthalmic segment of the ICA. Some brain areas received up to 11 times the expected radiotracer delivery, while other regions received as little as one-tenth. This streaming pattern was markedly reduced or eliminated by DPPI. In the five patients who received infraophthalmic infusions, a minimally heterogeneous distribution of the infusate was detected. The authors conclude that extensive intravascular streaming accompanies supraophthalmic ICA infusions in patients. The magnitude of streaming can be substantially reduced or eliminated with DPPI. Those who perform intra-arterial infusion should consider using DPPI to assure uniform drug delivery to brain.

Mixing in the human carotid artery during carotid drug infusion studied with PET

The safety and efficacy of drug infusion into the carotid artery require adequate mixing of the infused solution with carotid blood. Using positron emission tomography (PET), we studied the mixing of solutions infused into the human carotid artery in seven patients by analyzing the distribution of [15O]H2O infused into the carotid artery and by vein. At four infusion rates ranging from 0.5 to 10 ml/min, the variability in distribution averaged 16.5-17.8% among the pixels in a large volume of interest, without dependence on the infusion rate. The overall correlation between [15O]H2O influx with arterial infusion and [15O]H2O influx with venous injection was 0.78-0.82 at the four infusion rates, with no trend toward higher correlations at the faster infusion rates. The distribution into the anterior, middle, and posterior cerebral artery territories differed from distribution throughout the entire carotid territory by an average of 6.2-9.6% at the four infusion rates, with no trend toward smaller differences at the faster infusion rates. Infusions performed into a vinyl tube simulating the carotid artery indicated that at 0.5 ml/min, the velocity of fluid exiting the catheter makes no apparent contribution to mixing. We conclude that with infusions at the carotid bifurcation, mixing in the human carotid artery is complete or nearly complete over a wide range of infusion rates. The mixing appears to result from the patterns of blood flow within the artery, and not from jet effects at the catheter tip.