Effects of beta-adrenoreceptor blockade and nitroglycerin on myocardial oxygenation.
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Adrenergic beta-Antagonists↗
Biomedical subjects
H R Weiss
Publications and source records attributed to H R Weiss.
Perfused capillary morphometry in the senescent brain.
This study compared quantitative indices of capillary morphometry in the perfused vs. total capillary bed of conscious young (8-10 month old) and senescent (28-33 month old) rat brains. The total capillary bed was identified through alkaline phosphatase staining of tissue sections cut from specific brain regions. The perfused capillary bed was identified by the presence of fluorescein isothiocyanate (FITC) dextran in the microvessels. Average capillary volume fraction, VV (mm3/mm3, mean +/- S.E.M.) was 0.040 +/- 0.002 and 0.033 +/- 0.001 in the total capillary bed of the young and old animals, respectively. These values were not statistically different. Perfused VV averaged 0.020 +/- 0.001 and 0.017 +/- 0.001 mm3/mm3 in the young and old animals, respectively. Average perfused VV was 50% in the young and 49% in the senescent rat brains. Young and senescent brains utilize similar proportions of their "capillary reserves." In the areas examined in the brains of young animals, differences were found in the percentage of capillary volume/mm3, VV, and surface area/mm3, SV, perfused which were not present in old animals. The structural and neurochemical changes noted by others in the brain during aging were not related to alterations in indices of average and regional total or perfused cerebral capillary bed morphometry. However, differences in percent perfused VV, SV, length, LV, and number, Na, present in the younger rat brains were not present in the senescent rat brains.
Aging↗
Effect of AF64A on cerebral oxygen consumption in young and old rats.
Regional brain O2 consumption was determined in conscious Fischer-344 rats 3- and 33-months of age after intrahippocampal injection of the selective presynaptic cholinergic neurotoxin AF64A to investigate the influence of acetylcholine on this parameter. Regional cerebral blood flow (rCBF) was determined with 14[C]-iodoantipyrine. Regional arterial and venous oxygen saturation was measured microspectrophotometrically. Regional cerebral oxygen consumption was calculated by multiplying rCBF and cerebral oxygen extraction. Systemic hemodynamic and blood gas parameters were not altered by aging or AF64A. Aging or sham injection per se did not have any significant effect on rCBF, oxygen extraction and cerebral oxygen consumption. In 3-month-old AF64A-treated rats, rCBF, oxygen extraction or cerebral oxygen consumption were significantly lower than in the control group of the same age. Old AF64A-treated animals demonstrated a significant decrease in rCBF and cerebral oxygen consumption but not in cerebral oxygen extraction when compared to the sham-lesioned group of the same age. Oxygen consumption was significantly decreased by AF64A in each examined region of both young and old groups of rats, although the decreases were less severe in the older rats. This may be related to the lesser influence of the cholinergic system on cerebral oxygen consumption in old animals or a decreased toxicity of AF64A in older animals.
Aging↗
Cerebral oxygen consumption and blood flow in Fischer-344 rats of different ages.
Regional cerebral oxygen consumption and blood flow were determined and compared in conscious male Fischer-344 rats at 3, 12, 24 and 33 months of age to correlate the reported regional neurochemical and morphological changes which occur in these parameters during development, maturation, aging and senescence. Cerebral blood flow was determined with 14[C]-labelled iodoantipyrine and regional cerebral arterial and venous oxygen saturation was measured microspectrophotometrically. Oxygen consumption was obtained by multiplying cerebral blood flow and oxygen extraction. Systolic and diastolic blood pressure and heart rate decreased significantly with age. Average cerebral blood flow, oxygen extraction and oxygen consumption/100 g did not differ significantly between the four age groups examined. Oxygen consumption averaged 2.9 +/- 0.1 ml O2/min/100 g (mean +/- S.E.M.) in the 3-month-old group and 3.6 +/- 0.1 ml O2/min/100 g in the 33-month-old group. Differences in flow among the examined brain regions, which were present in the mature, 12-month-old brain, were not present in the developing, aging or senescent rat brain. Compensatory alterations in the efficiency or organization of neurochemical activity which occur during development, aging and senescence may modify the inter-regional differences in cerebral blood flow and oxygen consumption noted during maturation. There was no correlation found between the neurochemical and morphological changes which have been reported during maturation, aging or senescence and regional cerebral oxygen consumption.
Aging↗
[Anthropometric 3D-body scanning in idiopathic scoliosis].
PURPOSE: A new, non-invasive method of 3D-measurement is presented which allows the spatial recording of the entire body surface in scoliotic deformities. The application of the system is examined to raise automatically anthropometric data of patients with scoliosis. METHOD: 32 patients with idiopathic scoliosis were examined (average age 15.3 years, 25 girls and 7 boys, Cobb angles between 11 and 72 degrees). The whole body recording is carried out with a 3D laser scanner. During the measuring process the patient is standing in a frame. Within the measuring time of 15 seconds the body surface is registered by lasers and four cameras. The measured values are converted to a digital 3D model. The resolution is up to 1 mm. On the digital 3D model an automatic calculation of defined anthropometric parameters were carried out. Each patient was measured twice. RESULTS: In all patients a virtual 3D model with a high surface accuracy was obtained. Was the model the typical body asymmetries in scoliotic deformities were visible. The automatic calculation shows a mean deviation of the second measurements between 0.23 and 0.71 cm. The reproducibility depended on the type of the measured parameters. CONCLUSIONS: The laser scanning system allows a rapid, touchless and accurate 3D measurement of the whole body in scoliotic deformities. To determine anthropometric parameters the reproducibility of the automatic calculation is sufficient in most parameters.
Adolescent↗
[The Schroth scoliosis-specific back school--initial results of a prospective follow-up study].
The prospective study reported here was instituted in 1987 to obtain more detailed data on the efficacy of scoliosis-specific spinal rehabilitation after Schroth. Inclusion criteria were 1) idiopathic scoliosis, 2) Risser stage < 4, 3) no treatment with corset or electrical stimulation, 4) first examination between 1 and 3 years postoperatively, 5) usable total X-rays taken with the patient standing not more than 6 months prior to admission. A total of 181 scoliosis patients with an average age of 12.76 years and an average Cobb angle of 27 degrees were included in the study. The average Risser's sign was 1.4 and the average follow-up period was 33 months. No cases of relative progression (annual increase in curvature of 5 degrees or more) were observed. For the purpose of comparison with the spontaneous course, the patients were grouped by age and severity of scoliosis. Both the absence of any relative progression as well as direct comparison of the development of scoliosis under therapy with the spontaneous course confirmed the efficacy of the stationary rehabilitation programme notably in cases with poor prognosis, i.e. with large scoliosis angles and unfavourable curvatures.
Adolescent↗
Effect of dopamine and blockade of dopaminergic and adrenergic receptors on coronary blood flow in ischemic rabbit myocardium.
The effect of a broad dose range of dopamine on coronary blood flow was studied in rabbits with coronary artery occlusion. Dopaminergic and adrenergic receptor blockade was established to distinguish the mechanism of the dopamine-induced increase in coronary blood flow. Dopamine, 10, 100, or 1,000 micrograms/kg/min, was infused in the presence of dopaminergic, beta-, or alpha-adrenergic receptor blockade. Coronary blood flow, as measured by radiolabeled microspheres, and hemodynamic parameters were monitored in 60 anesthetized open-chest rabbits. Dopamine, 1,000 micrograms/kg/min, significantly increased coronary blood flow 157% in normal and 118% in occluded rabbit myocardium. Propranolol (2 mg/kg) prevented the dopamine-induced increases in coronary blood flow within occluded and nonoccluded myocardium. Practolol (2 mg/kg) blunted the coronary blood flow increases within occluded myocardium, but flow within normal myocardium remained significantly elevated. In animals given phenoxybenzamine (2 mg/kg), dopamine infusion produced significant blood pressure reductions along with no change in either occluded or nonoccluded coronary blood flow. Bulbocapnine (8 mg/kg), a dopamine receptor antagonist, did not block blood flow increases in normal myocardium, but prevented significant increases in blood flow within occluded myocardium. It can be concluded that direct or indirect vasodilator receptors (dopaminergic, beta 1-, and beta 2-adrenoceptors) must be stimulated and perfusion pressure must not fall in order for dopamine to produce increases of coronary blood flow within occluded myocardium.
Animals↗
Nitroglycerin improves the distribution of regional oxygenation in partially ischemic canine myocardium.
The effect of nitroglycerin administration on regional oxygen supply and consumption of partially ischemic areas of myocardium was investigated in 14 open-chest anesthetized dogs. Flow in the left anterior descending coronary artery (LAD) was reduced by 50% with the aid of a specially designed screw clamp placed below the first bifurcation. Seven animals received nitroglycerin (20 micrograms/kg i.v.) 5 min following partial occlusion. The remaining animals served as controls. Regional blood flow as measured with radioactive microspheres (15 +/- 3 micron in diameter) was determined before and 10 min following partial occlusion. Regional O2 saturations in small arteries and veins were determined using a microspectrophotometric technique. Oxygen supply, A-V O2 difference, and consumption were calculated in both subepicardial and subendocardial regions of ischemic and non-ischemic myocardium after occlusion. Tissue blood flow to the partially occluded regions was reduced by about 40% in both treated and untreated animals. Nitroglycerin prevented a significant reduction in arterial and venous O2 saturation of the partially occluded region. In the occluded subendocardium, nitroglycerin reduced the skewness of the venous O2 saturation distribution. The O2 supply/consumption ratio was significantly improved by nitroglycerin in the ischemic subendocardium, compared with the same region in the control group. It is suggested that nitroglycerin improves the microregional relationship between blood flow and metabolism even in the absence of a change in total regional blood supply.
Animals↗
Pentaerythritol trinitrate and glyceryl trinitrate on intramyocardial oxygenation and perfusion in the dog. Krogh analysis of transmural metabolism.
1. The effect of intravenous pentaerythritol trinitrate and glyceryl trinitrate on left ventricular subepicardial (epi) and subendocardial (endo) PO2 and perfusion were compared in anaesthetized open-chest mongrel dogs. Tissue PO2 was determined simultaneously at a depth of 3 mm (epicardial) and 9 mm (endocardial) with small platinum electrodes by polarography. In a separate series of dogs tissue perfusion of those regions was measured by hydrogen (H2) clearance using similar electrodes. 2. Both nitrates increased endocardial PO2 while epicardial PO2 was not altered. Perfusion was determined at the point of the maximal rise in endocardial PO2 (4-7 min after injection of either nitrate). At that period average coronary artery inflow and epicardial perfusion were decreased but endocardial perfusion was not significantly altered. 3. Using the data on PO2, hydrogen clearance and intercapillary distance, the effect of the nitrates on transmural metabolism (oxygen consumption) was estimated by Krogh analysis. Basal endocardial metabolism was 20-30% higher than epicardial metabolism. The nitrates reduced metabolism in each region. The absolute decrease in oxygen consumption was greater in the endocardium. 4. The results show that both pentaerythritol trinitrate and glyceryl trinitrate improve endocardial oxygenation by producing a more favourable balance between perfusion and oxygen requirements in that region.
Animals↗
Blood flow and relative tissue oxygenation of normal and partially ischaemic myocardium: effect of CO2.
1. Ischaemia of a portion of the myocardium in the dog heart was produced by tying off a small branch of a coronary artery: flow in the occluded region was reduced from 5 to 82% of the initial value. 2. The effect of inhalation of 5% CO2 in air on relative tissue PO2 and perfusion in normal and partially ischaemic myocardium was determined. 3. After 10 min inhalation of 5% CO2, there was an increase in tissue perfusion as measured by hydrogen desaturation; the increase was inversely proportional to the degree of flow reduction. 4. Relative intramyocardial PO2 measured polarographically, decreased with occlusion and increased after CO2 inhalation; the changes were inversely proportional to the degree of reduction in PO2. 5. The increase in flow after CO2 inhalation suggests that partially ischaemic myocardial tissue is capable of further vasodilation.
Animals↗
Regional O2 supply/consumption in normal and ischaemic rabbit myocardium: effect of nifedipine.
The effect of nifedipine infusion on myocardial O2 supply and consumption in flow-restricted and normal regions of the left ventricle was tested in anaesthetized open-chest rabbits after ligation of the left anterior descending coronary artery for one hour. Ten min after occlusion, nifedipine-treated animals were given either a low or high dose of the drug: a 5 micrograms/kg bolus followed by 1 micrograms/kg per min infusion or a 10 micrograms/kg bolus and 10 micrograms/kg per min infusion, respectively. Regional blood flow was measured before and after occlusion using radioactive microspheres and O2 saturation was measured microspectrophotometrically; the Fick Principle was then employed to determine regional O2 consumption. After a 60 min occlusion, blood flow was reduced overall to 51% of pre-ligation flows in the occluded region, and treatment with nifedipine or vehicle did not significantly alter this flow reduction. Blood flow in nonoccluded regions increased 1.6-fold only with the high dose of nifedipine and was unchanged in all other groups. Microspectrophotometric analysis of low dose nifedipine and control hearts showed that O2 extraction was greater in occluded than in normal myocardium (9.0, s.d. = 0.9, ml O2/100 ml blood vs 7.2, s.d. = 0.7, respectively) and that subendocardial extraction exceeded subepicardial. These data suggest that nifedipine administration at this dose had no apparent beneficial effect on O2 supply or O2 consumption in normal or flow-restricted regions of the left ventricle during 1 h of coronary artery occlusion.
Animals↗
Regional myocardial efficiency is improved in experimental aorto-caval shunt.
We determined whether regional myocardial work efficiency (segment work/regional O2 consumption) would be elevated by surgically-augmented inflow. In 10 anesthetized open-chest dogs, shunt between the ascending aorta and the superior vena cava was used to increase cardiac output. Hetastarch (15 ml/kg) was infused before opening the shunt to maintain coronary perfusion pressure. Regional myocardial segment work and O2 consumption (MVO2) were measured, during control and two levels of elevated flow. Regional segment work (g.mm/min) was calculated as the integrated products of force (g - miniature transducer) and segment shortening (mm - ultrasonic dimension gauge) during an averaged beat expressed per minute. Local MVO2 (ml O2/min/100g) was calculated from regional blood flow (microspheres) and O2 saturations (microspectrophotometry). It was found that regional myocardial segment work increased significantly (P < 0.05) from 926 +/- 94 to 1656 +/- 220 to 1479 +/- 309 (g.mm/min) for closed, half-open, and open shunt. This increase was primarily associated with increased segment shortening (from 147 +/- 14.1 to 204.4 +/- 20.1 to 232 +/- 26.1 mm/min). Both force development and regional MVO2 were unchanged during the experiment. Regional myocardial efficiency was significantly elevated during shunt function (from 95 +/- 12 to 187 +/- 31 to 213 +/- 57 g.mm/ml O2/100g). Systolic ejection stiffness (defined as the slope of the force-length relationship during the period of ejection) decreased from 8.0 +/- 0.9 to 4.7 +/- 0.4 to 4.5 +/- 0.9 g/mm during elevated inflow. It is concluded that when cardiac work is augmented primarily by segment shortening, regional myocardial efficiency is improved. This improvement is associated with decreased resistance to shortening (stiffness).
Animals↗
Preliminary results and worst-case analysis of in patient scoliosis rehabilitation.
The purpose of this study was to assess the effectiveness of a scoliosis-specific rehabilitation programme as it is carried out in the Katharina Schroth Spinal Deformities Rehabilitation Center. Physiotherapy in the treatment of scoliosis patients is still regarded as ineffective since the study by the American Orthopedic Association in 1941, which showed that general exercises could not influence the natural history of scoliosis. However, specific exercise programmes were not known in the USA at that time. This preliminary study started in 1989 with the following inclusion criteria: (1) diagnosis of idiopathic scoliosis; (2) risser sign < 4; (3) no treatment other than physiotherapy; (4) first control after 1-3 years during repeated in patient treatment; (5) standing AP radiograph taken not more than 6 months before the first in patient treatment. A total of 181 scoliosis patients, with an average age of 12.7 years and an average angle of curvature of 27% according to Cobb, were included in this study. The average risser sign was 1.4, the average follow-up 33 months. The Cobb angle of the major curve was measured in a standardized way. The results of our preliminary study were compared to natural history as known from literature. For the worst-case analysis additionally a questionnaire was sent to the non-repeaters treated at our centre at the same time (1989 and 1990) as the patient sample described above, taking into account the same inclusion criteria for this patient sample except point 4. Results showed that progression as usually defined (increase in curvature of 5 degrees or more per year) has not been found in the preliminary study. The patient sample of this study was divided into different age groups and different groups of curve magnitude, for comparison with other studies. Additional to the patient sample of the preliminary study, 116 of the patients from the years 1989 and 1990 fulfilled the inclusion criteria of the preliminary study with the exception of point 4. These patients formed the questionnaire sample for the worst-case analysis showing that the progression rate of the 181 patients from the preliminary study and the 116 patients of the questionnaire sample together was still better than natural history even if all drop-outs were considered to be failures. The fact that there was no relative progression in our patients sample treated solely by physiotherapy (preliminary study), seems to show the effectiveness of the inpatient rehabilitation programme even in cases with a bad prognosis, severe angles of curvature and unfavourable curvature patterns. A worst-case analysis does not prevent this conclusion, even if all dropouts from the non-repeaters group were considered as failures.
Adolescent↗
Microvascular, flow and O2 consumption responses of ischemic myocardium to prazosin.
The effects of selective alpha 1-adrenoceptor blockade with prazosin were investigated in ischemic rabbit heart. Using labeled microspheres, regional coronary blood flow was measured before and 1 hr after occlusion of the circumflex coronary artery in controls and animals given 1 mg/kg of prazosin 10 min after ligation. Small artery and vein O2 saturations were obtained microspectrophotometrically from hearts of anesthetized rabbits. Fluorescein isothiocyanate-dextran (150 mg/kg) was administered to mark the perfused microvessels and alkaline phosphatase stain was used to locate the total microvasculature. Prazosin depressed the arterial blood pressure. Coronary flow and O2 consumption (10.9 +/- 4.5 and 6.1 +/- 1.8 ml O2/min/100 g, nonoccluded and occluded) were significantly lower in the occluded region in the control group, while O2 extraction (4.9 +/- 1.4 and 6.8 +/- 2.6 ml O2/100 ml) was locally elevated. The results of occlusion in the prazosin-treated group were similar for flow, O2 consumption (9.9 +/- 4.5 and 6.7 +/- 5.3 ml O2/min/100 g, nonoccluded and occluded) and O2 extraction (6.6 +/- 2.3 and 8.2 +/- 2.3 ml O2/100 ml). The per cent of perfused microvessels was not significantly altered by occlusion in the control group. In the prazosin group, the percentage of occluded region subendocardial capillaries and arterioles perfused was significantly greater than in the control group, e.g., 65 +/- 9% perfused capillaries/mm2 in control occluded subendocardium vs 78 +/- 9% perfused capillaries/mm2 in prazosin-treated occluded subendocardium. Thus, the slight increase in microvessel utilization with prazosin was not sufficient to improve the flow or the O2 consumption in the ischemic myocardium.
Alkaline Phosphatase↗
Coronary alpha-adrenergic stimulation does not alter the heterogeneity of myocardial blood flow and oxygen utilization.
Previous studies have suggested an uneven distribution of alpha-adrenergic receptors within the coronary arterial tree. We hypothesized that stimulation of these receptors would alter the regional and microregional variability of oxygen supply and utilization. Accordingly, we measured the heterogeneity of coronary blood flow to 0.5 g tissue samples and O2 saturation of small cardiac veins during coronary alpha-adrenergic stimulation. In 14 dogs we cannulated and perfused a branch of the left coronary artery. In seven dogs, an intracoronary infusion of the alpha-adrenergic agonist phenylephrine was established after prior beta-adrenergic blockade. Phenylephrine infusion decreased subendocardial venous O2 saturation (41.6 +/- 5.6 vs 45.4 +/- 5.8% saturated, P less than 0.05). It did not change the heterogeneity or distribution of the O2 saturations relative to the normally-perfused region (coefficient of variation = 22.4 +/- 6.7 vs. 19.7 +/- 4.8%, P = 0.20). Regional blood flows were made during control, beta-adrenergic blockade, and phenylephrine infusion conditions in the remaining dogs. The coefficient of variation of blood flow to samples from the perfused region was 27.1 +/- 9.8, 27.8 +/- 10.8, and 24.7 +/- 7.5% (P greater than 0.25), respectively. The results indicate that coronary alpha-adrenergic stimulation does not alter O2 supply/utilization heterogeneity, and suggest a fairly uniform distribution and/or effect of alpha-adrenergic receptors within the coronary resistance vessels.
Animals↗
Effects of magnesium sulfate and nifedipine on regional cerebral blood flow during middle cerebral artery ligation in the rat.
The effects of magnesium sulfate and nifedipine on regional cerebral blood flow were compared after ligation of the middle cerebral artery in rats. Twenty-one rats were divided into 3 groups of 7 each. The groups were the magnesium group, the nifedipine group, and the control group. Animals were anesthetized with pentobarbital. The middle cerebral artery was ligated, and magnesium sulfate was infused at a rate of 16 mg/kg/min for 30 min in the magnesium group, and nifedipine was infused at a rate of 10 micrograms/kg/min for 45 min in the nifedipine group. Using [14C]-iodoantipyrine, regional cerebral blood flow was measured 1 hr after middle cerebral artery ligation in the ischemic cortex, contralateral cortex, thalamus, hypothalamus, pons, medulla and cerebellum. In the control group, the mean cerebral blood flow was 30.7 +/- 12.2 ml/min/100 g in the middle cerebral artery-ligated cortex, and 75.9 +/- 10.5 ml/min/100 g in the contralateral cortex. Nifedipine did not significantly alter the cerebral blood flow in any of the brain regions studied. However, in the magnesium group, the regional cerebral blood flow in the middle cerebral artery-ligated cortex was significantly higher (64.2 +/- 8.8 ml/min/100 g) than that recorded in the control and nifedipine groups, whereas the regional cerebral blood flow in the contralateral cortex was not significantly different from other groups. Our data showed that magnesium was effective and superior to nifedipine in improving blood flow in the ischemic area of the brain.
Animals↗
Effect of beta-adrenoceptor stimulation or blockade on regional myocardial function and regional O2 consumption during myocardial ischemia.
The purpose of this study was to determine the effect of beta-adrenoceptor activation and blockade on the relationship between regional myocardial function and regional O2 consumption in ischemic and nonischemic myocardium. Myocardial regional segmental function was assessed in 28 open chest, anesthetized dogs using subepicardial dimension gauges. Ten min after LAD (left anterior descending coronary artery) occlusion, dogs were given i.v. saline, 2 mg/kg propranolol, 0.2 mg/kg pindolol, or 1 microgram/kg/min isoproterenol. Coronary blood flow was determined using radioactive microspheres before LAD occlusion, 10 min after occlusion, and 2 hr after LAD occlusion. Regional O2 consumption was determined using microspectrophotometry. LAD occlusion did not alter any index of myocardial function measured in the nonischemic region, but in the ischemic region, end systolic length (ESL) was increased 20% while shortening was converted to systolic bulging. No agent resulted in an improved ischemic regional function or an altered O2 consumption during LAD occlusion. In the nonischemic region the per cent shortening was increased 60% with isoproterenol compared to control. Propranolol and pindolol both increased the non-schemic regional ratio of per cent shortening vs O2 consumption significantly, suggesting an improved efficiency while isoproterenol lowered this ratio. When per cent shortening was plotted vs regional O2 consumption for all treatments, a significant linear relationship was observed in the nonischemic region. Thus, no drug treatment used in this study significantly improved central ischemic regional function, or O2 consumption, but both beta-adrenoceptor blockers seemed to result in an improved relationship between segmental shortening and O2 consumption in the nonischemic region.
Adrenergic beta-Agonists↗
Effect of hypoxia and adenosine on the microvascular reserve in the rabbit heart.
This study was done to determine if the unperfused reserves of arterioles and capillaries in the rabbit heart can be utilized independently. Anesthetized, open-chest rabbits were subjected to control, hypoxia or adenosine treatment. The animals were given 100 mg/kg FITC-dextran and the hearts were removed and sectioned for analysis of perfused and total arteriolar and capillary morphology. The fluorescence was used to photograph the perfused microvessels and the slides were then stained for visualization of all microvessels. Standard morphometric techniques were used to determine total and perfused morphometric indices for these microvessels. Mean arteriolar total density (Na) was 4.4 arterioles/mm2 for control, adenosine, and hypoxia groups with approximately half (52%) of control arterioles perfused. Most of the adenosine (92%) and hypoxia (82%) group arterioles were perfused. Mean capillary total Na was 2143 capillaries/mm2 for all groups with approximately half (60%) of control capillaries being perfused. Nearly all capillaries were perfused during hypoxia (96%) while the percent perfused capillarity with adenosine (80%) was between those numbers for control and hypoxia groups despite completely perfused arterioles. The arteriolar and capillary reserves can be utilized independently as adenosine treatment resulted in complete arteriolar perfusion while not resulting in complete capillary perfusion.
Adenosine↗