RESUMEN
OBJECTIVE: To evaluate the cardiovascular response to short-term prone positioning in neonates. STUDY DESIGN: In this prospective study, we continuously monitored heart rate (HR), stroke volume (SV) and cardiac output (CO) by electrical velocimetry in hemodynamically stable neonates in each of the following positions for 10 min: supine, prone and back-to-supine position. Skin blood flow (SBF) was also continuously assessed on the forehead or foot using Laser Doppler technology. Systemic vascular resistance (SVR) index was calculated as mean blood pressure (BP)/CO. Data were analyzed using repeated measures analysis of variance. RESULTS: Thirty neonates (gestational age: 35±4 weeks; postmenstrual age: 36±3 weeks) were enrolled. HR did not change in response to positioning. However, in prone position, SV, CO and SBF decreased and SVR index increased from 1.5±0.3 to 1.3±0.3 ml kg(-1) (mean ±s.d., P<0.01), 206±44 to 180±41 ml kg(-1) min(-1) (P<0.01), 0.54±0.30 to 0.44±0.29 perfusion units (P<0.01) and 0.25±0.06 to 0.30±0.07 mm Hg ml(-1) kg(-1) min(-1) (P<0.01), respectively. After placing the infants back-to-supine position, SV, CO, SBF and SVR index returned to baseline. The above pattern of cardiovascular changes was consistent in vast majority of the studied neonates. CONCLUSIONS: Short-term prone positioning is associated with decreased SV, CO and SBF and increased calculated SVR index.
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Gasto Cardíaco/fisiología , Recién Nacido/fisiología , Posición Prona/fisiología , Resistencia Vascular/fisiología , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Flujometría por Láser-Doppler , Masculino , Estudios Prospectivos , Piel/irrigación sanguínea , Volumen Sistólico/fisiología , Posición Supina/fisiologíaRESUMEN
A dilemma in behavioral brain mapping is that conventional techniques immobilize the subject, extinguishing all but the simplest behaviors. This is avoided if brain activation is imaged after completion of the behavior and tissue capture of the tracer. A single-pass flow tracer proposed for positron emission tomography (PET) is a radiolabeled copper(II) complex of pyruvaldehyde bis(N(4)-methylthiosemicarbazone), [Cu(64)]-PTSM. [Cu(64)]-PTSM reaches steady-state cerebral distribution more rapidly than the metabolic tracer [(18)F]-fluorodeoxyglucose, allowing imaging with substantially greater temporal resolution. Using dual-label autoradiography, this study compares the relative regional cerebral blood flow tracer distribution (CBF-TR) of [(64)Cu]-PTSM to that of the classic perfusion tracer [(14)C]-iodoantipyrine in a rat model during treadmill walking. Rats were exposed to continuous walking on a treadmill and compared to quiescent controls. [(64)Cu]-PTSM was bolus injected (iv) after 1 min, followed by a 5-minute uptake and subsequent bolus injection of [(14)C]-iodoantipyrine. CBF-TR was quantified by autoradiography and analyzed in the three-dimensionally reconstructed brain by statistical parametric mapping, as well as by region-of-interest analysis. A high homology was found between the [(64)Cu]-PTSM and [(14)C]-iodoantipyrine patterns of cerebral activation in cortical and subcortical regions. For white matter, however, [(64)Cu]-PTSM showed lower perfusion than [(14)Cu]-iodoantipyrine. [(64)Cu]-PTSM is a useful tracer for functional brain mapping in freely-moving subjects. Its application in conjunction with PET promises to increase our understanding of the neural circuitry of behaviors dependent on locomotion.
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Antipirina/análogos & derivados , Encéfalo/diagnóstico por imagen , Encéfalo/fisiología , Circulación Cerebrovascular/fisiología , Compuestos Organometálicos , Radiofármacos , Tiosemicarbazonas , Animales , Autorradiografía , Mapeo Encefálico , Corteza Cerebral/irrigación sanguínea , Procesamiento de Imagen Asistido por Computador , Masculino , Actividad Motora/fisiología , Tomografía de Emisión de Positrones , Ratas , Ratas Sprague-Dawley , Caminata/fisiologíaRESUMEN
Brain mapping in the freely moving animal is useful for studying motor circuits, not only because it avoids the potential confound of sedation or restraints, but because activated brain states may serve to accentuate differences that only manifest partially while a subject is in the resting state. Perfusion or metabolic mapping using autoradiography allows one to examine changes in brain function at the circuit level across the entire brain with a spatial resolution (approximately 100 micro) appropriate for the rat or mouse brain, and a temporal resolution (seconds-minutes) sufficient for capturing acute brain changes. Here we summarize the application of these methods to the functional brain mapping of behaviors involving locomotion of small animals, methods for the three-dimensional reconstruction of the brain from autoradiographic sections, voxel based analysis of the whole brain, and generation of maps of the flattened rat cortex. Application of these methods in animal models promises utility in improving our understanding of motor function in the normal brain, and of the effects of neuropathology and treatment interventions such as exercise have on the reorganization of motor circuits.
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Mapeo Encefálico/métodos , Encéfalo/fisiología , Actividad Motora/fisiología , Animales , Mapeo Encefálico/instrumentación , Ratones , Modelos Animales , RatasRESUMEN
We describe a method for the measurement, analysis and display of cerebral cortical data obtained from coronal brain sections of the adult rat. In this method, regions-of-interest (ROI) are selected in the cortical mantle in a semiautomated fashion using a radial grid overlay, spaced in 15 degrees intervals from the midline. ROI measurements of intensity are mapped on a flattened two-dimensional surface. Topographic maps of statistical significance at each ROI allow for the rapid viewing of group differences. Cortical z-scores are displayed with the boundaries of brain regions defined according to a standard atlas of the rat brain. This method and accompanying software implementation (Matlab, Labview) allow for compact data display in a variety of autoradiographic and histologic studies of the structure and function of the rat brain.
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Mapeo Encefálico/instrumentación , Mapeo Encefálico/métodos , Corteza Cerebral/fisiología , Programas Informáticos , Animales , Antipirina/análogos & derivados , Antipirina/farmacocinética , Autorradiografía , Radioisótopos de Carbono , Corteza Cerebral/diagnóstico por imagen , Cintigrafía , RatasRESUMEN
Exercise training (ET) causes functional and morphologic changes in normal and injured brain. While studies have examined effects of short-term (same day) training on functional brain activation, less work has evaluated effects of long-term training, in particular treadmill running. An improved understanding is relevant as changes in neural reorganization typically require days to weeks, and treadmill training is a component of many neurorehabilitation programs. Adult, male rats (n=10) trained to run for 40 min/day, 5 days/week on a Rotarod treadmill at 11.5 cm/s, while control animals (n=10) walked for 1 min/day at 1.2 cm/s. Six weeks later, [(14)C]-iodoantipyrine was injected intravenously during treadmill walking. Regional cerebral blood flow-related tissue radioactivity was quantified by autoradiography and analyzed in the three-dimensionally reconstructed brain by statistical parametric mapping. Exercised compared to nonexercised rats demonstrated increased influence of the cerebellar-thalamic-cortical (CbTC) circuit, with relative increases in perfusion in deep cerebellar nuclei (medial, interposed, lateral), thalamus (ventrolateral, midline, intralaminar), and paravermis, but with decreases in the vermis. In the basal ganglia-thalamic-cortical circuit, significant decreases were noted in sensorimotor cortex and striatum, with associated increases in the globus pallidus. Additional significant changes were noted in the ventral pallidum, superior colliculus, dentate gyrus (increases), and red nucleus (decreases). Following ET, the new dynamic equilibrium of the brain is characterized by increases in the efficiency of neural processing (sensorimotor cortex, striatum, vermis) and an increased influence of the CbTC circuit. Cerebral regions demonstrating changes in neural activation may point to alternate circuits, which may be mobilized during neurorehabilitation.
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Mapeo Encefálico , Cerebelo/fisiología , Corteza Cerebral/fisiología , Plasticidad Neuronal/fisiología , Condicionamiento Físico Animal , Tálamo/fisiología , Animales , Antipirina/análogos & derivados , Antipirina/metabolismo , Autorradiografía , Conducta Animal , Circulación Cerebrovascular , Procesamiento de Imagen Asistido por Computador , Masculino , Modelos Biológicos , Vías Nerviosas/fisiología , Ratas , Ratas Sprague-Dawley , Tritio/metabolismoRESUMEN
To evaluate functional neuronal compensation after partial damage to the nigrostriatal system, we lesioned rats unilaterally in the striatum with 6-hydroxydopamine. Five weeks later, cerebral perfusion was mapped at rest or during treadmill walking using [(14)C]-iodoantipyrine. Regional CBF-related tissue radioactivity (CBF-TR) was quantified by autoradiography and analyzed by statistical parametric mapping and region-of- interest analysis. Lesions were confirmed by tyrosine hydroxylase immunohistochemistry and changes in rotational locomotor activity. Functional compensations were bilateral and differed at rest and during treadmill walking. Consistent with the classic view of striatopallidal connections, CBF-TR of lesioned compared to sham-lesioned rats increased in the ipsilateral subthalamic nucleus (STN) and internal globus pallidus, and decreased in the striatum and external globus pallidus. Contrary to the classic view, CBF-TR increased in the ipsilateral ventral lateral, ventral anterior thalamus and motor cortex, as well as in the central medial thalamus, midline cerebellum, and contralateral STN. During walking, perfusion decreased in lesioned compared to sham-lesioned rats across the ipsilateral striato-pallidal-thalamic-cortical motor circuit. Compensatory increases were seen bilaterally in the ventromedial thalamus and red nucleus, in the contralateral STN, anterior substantia nigra, subiculum, motor cortex, and in midline cerebellum. Enhanced recruitment of associative sensory areas was noted cortically and subcortically. Future models of compensatory changes after nigrostriatal damage need to address the effects of increased neural activity by residual dopaminergic neurons, interhemispheric interactions and differences between resting and locomotor states. Identification of sites at which functional compensation occurs may define useful future targets for neurorehabilitative or neurorestorative interventions in Parkinson's disease.
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Daño Encefálico Crónico/fisiopatología , Encéfalo/fisiopatología , Lateralidad Funcional/fisiología , Locomoción/fisiología , Descanso/fisiología , Anfetamina/farmacología , Animales , Autorradiografía , Daño Encefálico Crónico/líquido cefalorraquídeo , Daño Encefálico Crónico/inducido químicamente , Mapeo Encefálico , Estimulantes del Sistema Nervioso Central/farmacología , Cerebelo/fisiopatología , Globo Pálido/fisiopatología , Procesamiento de Imagen Asistido por Computador , Masculino , Modelos Neurológicos , Neostriado/fisiopatología , Oxidopamina , Ratas , Ratas Sprague-Dawley , Núcleo Subtalámico/fisiopatología , Tirosina 3-Monooxigenasa/metabolismo , Caminata/fisiologíaRESUMEN
Conditioned fear (CF) is one of the most frequently used behavioral paradigms; however, little work has mapped changes in cerebral perfusion during CF in the rat-the species which has dominated CF research. Adult rats carrying an implanted minipump were exposed to a tone (controls, n = 8) or a tone conditioned in association with footshocks (CS group, n = 9). During reexposure to the tone 24 h later, animals were injected intravenously by remote activation with [14C]-iodoantipyrine using the pump. Significant group differences in regional CBF-related tissue radioactivity (CBF-TR) were determined by region-of-interest analysis of brain autoradiographs, as well as in the reconstructed, three-dimensional brain by statistical parametric mapping (SPM). CS animals demonstrated significantly greater, fear-enhanced increases in CBF-TR in auditory cortex than controls. The lateral amygdala was activated, whereas the basolateral/basomedial and central amygdala were deactivated. In the hippocampus and medial prefrontal cortex, CBF-TR increased significantly ventrally but not dorsally. Significant activations were noted in medial striatum and the thalamic midline and intralaminar nuclei. However, the ventrolateral/dorsolateral striatum and its afferents from motor and somatosensory cortex were deactivated, consistent with the behavioral immobility seen during CF. Significant activations were also noted in the lateral septum, periaqueductal gray, and deep mesencephalic nucleus/tegmental tract. Our results show that auditory stimuli endowed with aversive properties through conditioning result in significant redistribution of cerebral perfusion. SPM is a useful tool in the brain mapping of complex rodent behaviors, in particular the changes in activation patterns in limbic, thalamic, motor, and cortical circuits during CF.
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Aprendizaje por Asociación/fisiología , Percepción Auditiva/fisiología , Encéfalo/irrigación sanguínea , Condicionamiento Clásico/fisiología , Miedo/fisiología , Procesamiento de Imagen Asistido por Computador , Imagenología Tridimensional , Imagen por Resonancia Magnética , Animales , Nivel de Alerta/fisiología , Señales (Psicología) , Masculino , Red Nerviosa/fisiología , Ratas , Ratas Wistar , Flujo Sanguíneo Regional/fisiologíaRESUMEN
Most brain mapping techniques require immobilization of the subject, which extinguishes all but the simplest behaviors. We applied in freely moving rats an implantable microbolus infusion pump (MIP) which can be triggered by remote activation for the injection of the cerebral blood flow tracer [(14)C]iodoantipyrine during behavioral activation. Consistent with previous electrophysiological, metabolic and brain anatomic studies, CBF-related tissue radioactivity (CBF-TR) increased in acoustic cortex during a 1000 Hz/8000 Hz alternating tone. In response to an acute foot-shock, CBF-TR increased in visual cortex, parietal association cortex, and extended into primary motor cortex, and primary somatosensory cortex mapping the trunk. These results support the utility of implantable pumps as adjunct tools for studying cerebral activation during behavioral challenges in nontethered, nonrestrained animals.
Asunto(s)
Antipirina/análogos & derivados , Corteza Auditiva/fisiología , Mapeo Encefálico/métodos , Circulación Cerebrovascular , Estrés Fisiológico/fisiopatología , Estimulación Acústica , Animales , Antipirina/farmacocinética , Corteza Auditiva/irrigación sanguínea , Corteza Auditiva/diagnóstico por imagen , Autorradiografía , Radioisótopos de Carbono , Electrochoque , Masculino , Actividad Motora , Cintigrafía , Ratas , Ratas Sprague-Dawley , Estrés Fisiológico/diagnóstico por imagenRESUMEN
A dilemma in functional neuroimaging is that immobilization of the subject, necessary to avoid movement artifact, extinguishes all but the simplest behaviors. Recently, we developed an implantable microbolus infusion pump (MIP) that allows bolus injection of radiotracers by remote activation in freely moving, nontethered animals. The MIP is examined as a tool for brain mapping in rats during a locomotor task. Cerebral blood flow-related tissue radioactivity (CBF-TR) was measured using [14C]-iodoantipyrine with an indicator-fractionation method, followed by autoradiography. Rats exposed to walking on a treadmill, compared to quiescent controls, showed increases in CBF-TR in motor circuits (primary motor cortex, dorsolateral striatum, ventrolateral thalamus, midline cerebellum, copula pyramis, paramedian lobule), in primary somatosensory cortex mapping the forelimbs, hindlimbs and trunk, as well as in secondary visual cortex. These results support the use of implantable pumps as adjunct tools for functional neuroimaging of behaviors that cannot be elicited in restrained or tethered animals.
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Antipirina/análogos & derivados , Mapeo Encefálico/métodos , Prueba de Esfuerzo , Animales , Radioisótopos de Carbono , Bombas de Infusión Implantables , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
One of the current constraints on functional neuroimaging in animals is that to avoid movement artifacts during data acquisition, subjects need to be immobilized, sedated, or anesthetized. Such measures limit the behaviors that can be examined, and introduce the additional variables of stress or anesthetic agents that may confound meaningful interpretation. This study provides a description of the design and characteristics of a self-contained, implantable microbolus infusion pump (MIP) that allows triggering of a bolus injection at a distance in conscious, behaving rats that are not restrained or tethered. The MIP is externally triggered by a pulse of infrared light and allows in vivo bolus drug delivery. We describe application of this technology to the intravenous bolus delivery of iodo[(14)C]antipyrine in a freely moving animal, followed immediately by lethal injection, rapid removal of the brain, and analysis of regional cerebral blood flow tissue radioactivity with the use of autoradiography. The ability to investigate changes in brain activation in nonrestrained animals makes the MIP a powerful tool for evaluation of complex behaviors.
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Antiinflamatorios no Esteroideos/farmacocinética , Antipirina/farmacocinética , Conducta Animal , Bombas de Infusión Implantables , Animales , Autorradiografía , Radioisótopos de Carbono , Circulación Cerebrovascular/fisiología , Masculino , Actividad Motora , Ratas , Ratas Sprague-DawleyRESUMEN
Lesion composition plays a significant role in atherosclerotic lesion instability and rupture. Current clinical techniques cannot fully characterize lesion composition or accurately identify unstable lesions. This study investigates the use of time-resolved fluorescence spectroscopy for unstable atherosclerotic lesion diagnosis. The fluorescence of human coronary artery samples was induced with nitrogen laser and detected in the 360- to 510-nm wavelength range. The samples were sorted into 7 groups according to the AHA classification: normal wall and types I, II(a) (fatty streaks), III (preatheroma), IV (atheroma), V(a) (fibrous), and V(b) (calcified) lesions. Spectral intensities and time-dependent parameters [average lifetime tau(f); decay constants: tau(1) (fast-term), tau(2) (slow-term), A(1) (fast-term amplitude contribution)] derived from the time-resolved spectra of coronary samples were used for tissue characterization. We determined that a few intensity values at longer wavelengths (>430 nm) and time-dependent parameters at peak emission region (390 nm) discriminate between all types of arterial samples except between normal wall and type I lesions. The lipid-rich lesions (more unstable) can be discriminated from fibrous lesions (more stable) on the basis of time-dependent parameters (lifetime and fast-term decay). We inferred that features of lipid fluorescence are reflected on lipid-rich lesion emission. Our results demonstrate that analysis of the time-resolved spectra may be used to enhance the discrimination between different grades of atherosclerotic lesions and provide a means of discrimination between lipid-rich and fibrous lesions.
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Enfermedad de la Arteria Coronaria/patología , Rayos Láser , Metabolismo de los Lípidos , Espectrometría de Fluorescencia/métodos , Adolescente , Adulto , Anciano , Aorta/patología , Niño , Vasos Coronarios/patología , Humanos , Persona de Mediana Edad , Factores de TiempoRESUMEN
Indocyanine green (ICG) has been widely used in cardiovascular, hepatic, and ophthalmologic studies. Application of this fluorescent dye has been handicapped by its poor stability in solution and by the complex dependence of its fluorescence intensity on concentration. Noncovalent interactions between ICG and sodium polyaspartate (PASP) stabilize ICG fluorescence in aqueous solution, but the effect of PASP on ICG fluorescence in blood has not been described. The current study had two main goals: first, to characterize in vitro in blood the relationship between fluorescence intensity and concentration of ICG-PASP (ICG) and the stability of this relationship over time; second, to test a new phenomenological model describing the dependence of ICG fluorescence on concentration. Freshly-prepared ICG and ICG-PASP solutions produced the same fluorescence intensity over a wide range of concentrations (0.0005-0.1271 mg/ml). The peak fluorescence of ICG was reduced by 11% after 10 h and by 72% at 7 days. In contrast, the peak fluorescence intensity of ICG-PASP solutions was nearly unchanged for up to 14 days. The dependence of the fluorescence intensity on concentration was accurately represented by our model that accounted for the generation of fluorescence following light absorption, and for the reabsorption of the emitted fluorescence by ICG.
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Colorantes Fluorescentes/química , Verde de Indocianina/química , Péptidos/química , Fluorescencia , Modelos Químicos , SolucionesRESUMEN
BACKGROUND AND OBJECTIVE: This study characterized aortic time-resolved fluorescence spectra for stratified levels of atherosclerosis and proposed interpretation of spectrotemporal variations in terms of histologic changes. STUDY DESIGN/MATERIALS AND METHODS: Fluorescence emission transients were measured at 370-510 nm (337 nm excitation) on 94 excised human aortic samples, ranging from normal to advanced fibrous atherosclerotic lesion. Global analysis yielded a three-exponential approximation of the time-resolved spectra from which average lifetime and decay-associated spectra were derived. RESULTS: Average lifetime at 390 nm gradually increased from 2.4+/-0.1 nsec (normal aorta) to 3.9+/-0.1 nsec (advanced lesion). Fluorescence intensity was markedly decreased above 430 nm in intermediate and advanced lesions. Spectral intensity associated with the intermediate decay increased at 470-490 nm for early and intermediate lipid-rich lesions. CONCLUSION: Time-resolved fluorescence spectra of aortic samples presented distinctive features for each atherosclerotic lesion type, which could serve as characteristic markers for optical analysis of the aortic wall.
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Aorta/patología , Arteriosclerosis/diagnóstico , Endotelio Vascular/patología , Rayos Láser , Espectrometría de Fluorescencia/métodos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Arteriosclerosis/patología , Biomarcadores , Cadáver , Niño , Humanos , Persona de Mediana Edad , Índice de Severidad de la Enfermedad , Factores de TiempoRESUMEN
The time-resolved fluorescence spectra of the main arterial fluorescent compounds were retrieved using a new algorithm based on the Laguerre expansion of kernels technique. Samples of elastin, collagen and cholesterol were excited with a pulsed nitrogen laser and the emission was measured at 29 discrete wavelengths between 370 and 510 nm. The expansion of the fluorescence impulse response function on the Laguerre basis of functions was optimized to reproduce the observed fluorescence emission. Collagen lifetime (5.3 ns at 390 nm) was substantially larger than that of elastin (2.3 ns) and cholesterol (1.3 ns). Two decay components were identified in the emission decay of the compounds. For collagen, the decay components were markedly wavelength dependent and hydration dependent such that the emission decay became shorter at higher emission wavelengths and with hydration. The decay characteristics of elastin and cholesterol were relatively unchanged with wavelength and with hydration. The observed variations in the time-resolved spectra of elastin, collagen and cholesterol were consistent with the existence of several fluorophores with different emission characteristics. Because the compounds are present in different proportions in healthy and atherosclerotic arterial walls, characteristic differences in their time-resolved emission spectra could be exploited to assess optically the severity of atherosclerotic lesions.
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Arterias/química , Arteriosclerosis/metabolismo , Colesterol/química , Colágeno/química , Elastina/química , Procesamiento de Imagen Asistido por Computador/métodos , Arterias/patología , Humanos , Espectrometría de Fluorescencia/instrumentación , Espectrometría de Fluorescencia/métodos , Factores de TiempoRESUMEN
To study the photobleaching of the main fluorescent compounds of the arterial wall, we repeatedly measured the time-resolved fluorescence of elastin, collagen and cholesterol during 560 s of excitation with nitrogen laser pulses. Three fluence rate levels were used: 0.72, 7.25 and 21.75 microW/mm2. The irradiation-related changes of the fluorescence intensity and of the time-resolved fluorescence decay constants were characterized for the emission at 390, 430 and 470 nm. The fluorescence intensity at 390 nm decreased by 25-35% when the fluence delivered was 4 mJ/mm2, a common value in fluorescence studies of the arterial wall. Cholesterol fluorescence photobleached the most, and elastin fluorescence photobleached the least. Photobleaching was most intense at 390 nm and least intense at 470 nm such that the emission spectra of the three compounds were markedly distorted by photobleaching. The time-resolved decay constants and the fluorescence lifetime were not altered by irradiation when the fluence was below 4 mJ/mm2. The spectral distortions associated with photobleaching complicate the interpretation of arterial wall fluorescence in terms of tissue content in elastin, collagen and cholesterol. Use of the time-dependent features of the emission that are not altered by photobleaching should increase the accuracy of arterial wall analysis by fluorescence spectroscopy.
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Arterias/química , Colesterol/efectos de la radiación , Colágeno/efectos de la radiación , Elastina/efectos de la radiación , Animales , Arteriosclerosis/diagnóstico , Bovinos , Colesterol/química , Colágeno/química , Elastina/química , Colorantes Fluorescentes , Técnicas In Vitro , Fotoquímica , Espectrometría de Fluorescencia/instrumentación , Rayos UltravioletaRESUMEN
The reliability of pulse oximetry in neonates receiving inotropic drugs because of hypotension and microcirculatory perfusion failure has not been well documented. Signal loss of the pulse oximeter in adult patients receiving dopamine infusions has been reported. To evaluate the relationship between pulse oximeter oxygen saturation (SaO2) and co-oximeter directly measured oxygen saturation, we studied 30 infants in the first 4 days of life (birth weight 620 to 4285 gm, gestational age 26 to 43 weeks) receiving dopamine (30 patients) and dobutamine (10 infants). Infants had normal blood pressures at the time of the study. To minimize motion artifact a Nellcor N-200 (Nellcor Incorporated, Hayward, Calif.) oximeter with electrocardiographic synchronization was used. We compared pulse oximeter values with simultaneous arterial samples analyzed for oxygen saturation with an IL 282 co-oximeter (Instrumentation Laboratory, Inc., Lexington, Mass.). The values were corrected for spuriously elevated carboxyhemoglobin levels and fetal hemoglobin level was quantitatively measured. The partial pressure of oxygen at 90% hemoglobin saturation for each patient was calculated. The dosage of dopamine ranged from 4 to 28 micrograms/kg per minute and the dosage of dobutamine varied from 4 to 24 micrograms/kg per minute. Over a wide range of values for mean blood pressure (23 to 66 mm Hg), partial pressure of oxygen at 90% hemoglobin saturation (43.1 to 70.2 mm Hg), and oxygen saturation (SaO2 80% to 100%), linear regression analysis revealed a close correlation between pulse oximeter SaO2 and co-oximeter SaO2 values (r = 0.83, standard error of the estimate 2.2%, p < 0.0001). Our findings indicate that pulse oximetry can be used reliably for continuous oxygen monitoring in normotensive neonates with an SaO2 of 80% to 100% who are receiving dopamine and dobutamine.
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Peso al Nacer , Enfermedades Cardiovasculares/tratamiento farmacológico , Dobutamina/uso terapéutico , Dopamina/uso terapéutico , Recién Nacido , Oximetría , Enfermedades Cardiovasculares/sangre , Humanos , Oxígeno/sangre , Estudios ProspectivosRESUMEN
Diaphragm and latissimus dorsi muscle functions, histochemistries, and morphometries were studied in anesthetized male Yucatan minipigs with congestive heart failure (CHF) induced by supraventricular tachycardia (n = 5). Sham-operated animals served as a control group (n = 5). In CHF animals, transdiaphragmatic pressure measured during supramaximal phrenic stimulation was reduced by 40% at low frequencies (< or = 20 Hz) and by 60% at higher frequencies. Twitch amplitude and half-relaxation time were also decreased. The cross-sectional areas of type I, IIa, and IIb fibers were reduced in the diaphragm. The proportion of type I fibers increased, whereas type IIa fibers decreased. Succinate dehydrogenase activity was elevated in type IIa and IIb fibers, but diaphragmatic fatigability was not altered. CHF reduced latissimus dorsi isometric force by 40% for stimulation frequencies > or = 30 Hz. The cross-sectional area of latissimus dorsi type IIb fibers was decreased, but twitch characteristics, fiber type composition, succinate dehydrogenase activity, and fatigability were unchanged. Experimental CHF appears to cause greater intrinsic adaptive changes in the diaphragm compared with those in the latissimus dorsi in the minipig. For both muscles, reduced contractile function was associated with atrophy. Impaired performance of the diaphragm may also be attributed to an increase in the relative contribution of type I fibers to the total tension-generating capacity of the muscle and to the pathophysiological mechanisms underlying the shortened relaxation time of the twitch response.
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Diafragma/fisiopatología , Insuficiencia Cardíaca/fisiopatología , Músculo Esquelético/fisiopatología , Adaptación Fisiológica , Animales , Diafragma/enzimología , Diafragma/patología , Electrocardiografía , Insuficiencia Cardíaca/enzimología , Insuficiencia Cardíaca/patología , Hemodinámica/fisiología , Masculino , Contracción Muscular/fisiología , Fatiga Muscular/fisiología , Fibras Musculares Esqueléticas/fisiología , Músculo Esquelético/enzimología , Músculo Esquelético/patología , Tamaño de los Órganos/fisiología , Porcinos , Porcinos Enanos , Taquicardia Supraventricular/enzimología , Taquicardia Supraventricular/patología , Taquicardia Supraventricular/fisiopatologíaRESUMEN
We studied in isolated rabbit lungs the effects of oleic acid (OA) injury on the segmental distribution of vascular resistance. Vascular occlusion pressures were measured in control and OA-injured preparations over 90 min. Capillary filtration coefficient KF,C increased from 0.61 (+/- 0.10) to 0.91 (+/- 0.14) g.min-1.mmHg-1.(100 g)-1 in OA-injured lungs whereas it remained constant in control lungs. Total pulmonary vascular resistance changed little in both control and OA-injured lungs. OA injury resulted in a 15% increase of the double occlusion capillary pressure. In addition, the contribution of the microvascular to the total vascular resistance rose from 8% to 22%. The increase in microvascular resistance was significant 15 min after OA on the arteriolar side and became significant 30 min later on the venular side. Oleic acid injury does not change the total pulmonary vascular resistance but alters the distribution of segmental resistances in the isolated rabbit lung, thereby contributing to the accumulation of lung water in this model of low pressure permeability edema.
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Pulmón/irrigación sanguínea , Circulación Pulmonar/fisiología , Síndrome de Dificultad Respiratoria/fisiopatología , Resistencia Vascular/fisiología , Animales , Presión Sanguínea , Agua Pulmonar Extravascular , Inyecciones Intravenosas , Ácido Oléico , Ácidos Oléicos , Edema Pulmonar/fisiopatología , Conejos , Síndrome de Dificultad Respiratoria/inducido químicamenteRESUMEN
The periodic variations of the pulmonary microvascular pressure during pulsatile perfusion were studied in isolated left lower lobes of canine lungs by the arterial occlusion (AO) and double occlusion (DO) techniques. Sixteen AO and eight DO maneuvers evenly distributed within the pump cycle were performed for each of four frequencies: 36, 54, 72, and 90 beats/min. Nearly identical microvascular pressure contours were reconstructed from the AO and DO maneuvers by relocating the measured occlusion pressures in time. These contours lagged behind the pulmonary arterial pressure waveform. Their amplitude decreased from 25 to 14% of the arterial pulse pressure as the pump frequency was increased from 36 to 90 beats/min. The modulus of the pressure transfer function at the site of arterial occlusion decreased as the frequency increased. The phase was negative for all frequencies and it approached -90 degrees for the higher frequencies. Vasoconstriction induced by serotonin resulted in an increase of the magnitude of the AO pressure contour that was nearly proportional to the increase of the pulmonary arterial pulse pressure. In contrast, elevation of the lobar venous pressure to 10 mmHg increased the amplitude of the AO pressure contour, whereas it slightly decreased the pulmonary arterial pulse pressure. These experiments demonstrate that the AO and DO pressures fluctuate markedly during pulsatile perfusion. Their oscillations would be indicative of the pulsatility in the pulmonary microvascular bed.
Asunto(s)
Circulación Pulmonar/fisiología , Animales , Presión Sanguínea/fisiología , Perros , Técnicas In Vitro , Microcirculación/fisiología , Flujo Pulsátil/fisiología , Resistencia Vascular/fisiología , Vasoconstricción/fisiologíaRESUMEN
We measured arterial and venous occlusion pressure profiles in left lower lobes of dog lungs perfused in constant flow and pulsatile flow. Initially, pulmonary arterial pressure, flow rate, and venous pressure were recorded during a series of inflow and outflow occlusions effected during constant flow perfusion. The perfusion was then made pulsatile and while keeping the same flow rate, a second series of vascular occlusions was performed. The arterial occlusion pressures measured with the two modes of perfusion were similar. During pulsatile perfusion, the variation in arterial pressure following an arterial occlusion varied with the timing of occlusion in the pressure cycle. The arterial pressure drop could be recovered by selecting the time-averaged pulmonary arterial pressure as the upstream pressure. During both types of perfusion, the venous occlusion curves were similar. The arterial and venous pressure drops were approximately 4.8 mm Hg and 4.2 mm Hg, respectively. We concluded that the longitudinal distribution of pulmonary vascular pressures can be inferred from occlusion measurements obtained in pulsatile flow.