RESUMEN
PURPOSE: To investigate retinal blood flow and oxygen saturation changes in patients diagnosed with retinopathy following plaque radiation treatment to treat choroidal melanoma. METHODS: Eight patients (mean age 55.75 years, SD 12.58 years) who have developed unilateral ischaemic radiation-related retinopathy as confirmed by wide-field fluorescein angiography were recruited for the study. The fellow eye with no other ocular or retinal pathology was used as control. Both eyes underwent measurement of total retinal blood flow (TRBF) and retinal blood oxygen saturation using prototype methodologies of Doppler Spectral Domain Optical Coherence Tomography (OCT) and Hyperspectral Retinal Camera, respectively. RESULTS: The average TRBF in the retinopathy eye was significantly lower compared to the fellow eye (33.48 ± 12.73 µl/min versus 50.37 ± 15.26 µl/min; p = 0.013). The arteriolar oxygen saturation (SaO2 ) and venular oxygen saturation (SvO2 ) were higher in the retinopathy eye compared to the fellow eye (101.11 ± 4.26%, versus 94.45 ± 5.79%; p = 0.008) and (62.96 ± 11.05% versus 51.24 ± 6.88%, p = 0.051), respectively. CONCLUSION: The ionizing radiation seems to have an impact on the TRBF, SaO2 and SvO2 , clinically presenting similar to a rapidly developing diabetic retinopathy. The results show an altered retinal vascular physiology in patients with radiation-related retinopathy.
Asunto(s)
Angiografía con Fluoresceína/métodos , Traumatismos por Radiación/complicaciones , Flujo Sanguíneo Regional/fisiología , Enfermedades de la Retina/fisiopatología , Vasos Retinianos/fisiopatología , Tomografía de Coherencia Óptica/métodos , Neoplasias de la Coroides/radioterapia , Progresión de la Enfermedad , Femenino , Fondo de Ojo , Humanos , Melanoma/radioterapia , Persona de Mediana Edad , Traumatismos por Radiación/diagnóstico , Traumatismos por Radiación/fisiopatología , Enfermedades de la Retina/diagnóstico , Enfermedades de la Retina/etiología , Vasos Retinianos/diagnóstico por imagen , Vasos Retinianos/efectos de la radiaciónRESUMEN
PURPOSE: The aim of the study is to validate and calibrate the Doppler spectral-domain optical coherence tomography (SD-OCT) derived total retinal blood flow (TRBF) and metabolic hyperspectral retinal camera (MHRC) derived oxygen saturation (SO2) of major retinal vessels in human volunteers using a novel and exact provocation technique (RespirAct) that allows the precise control of the end-tidal partial pressure of oxygen (PETO2). Between visit repeatability of the TRBF and retinal blood SO2 also were studied. METHODS: One eye of 11 young healthy subjects was chosen randomly for the study. Total retinal blood flow and retinal SO2 measurements were obtained under conditions of normoxia, hyperoxia, and hypoxia. The order of hyperoxia and hypoxia was randomized between subjects. The measurements were repeated after a week interval. RESULTS: When the arterial PETO2 was increased from baseline (PETO2 = 100 mm Hg) to 200 and 300 mm Hg, the TRBF significantly reduced (P = 0.02) from 44.60 (±8.9) to 40.28 (±8.9) and 36.23 (±4.6) µL/min. Lowering the arterial PETO2, from baseline to 80, 60, and 50 mm Hg, TRBF significantly increased (P = 0.04) from 43.17 (±12.7) to 45.19 (±5.5), 49.71 (±13.4), and 52.89 (±10.9) µL/min with simultaneous reduction in the arterial blood SO2 content from 99.3% (±5.8) to 95.6% (±5.1), 89.6% (±2.8), and 83.3% (±3.9), respectively (P = 0.00). The coefficient of repeatability (COR) of TRBF, retinal arterial, and venous blood SO2 values are 21.8 µL/min, 18.4%, and 15.2%, respectively. CONCLUSIONS: Total retinal blood flow and retinal blood SO2 measurements performed under safe levels of hypoxia and hyperoxia were repeatable in healthy adults over the range of SO2 investigated.
Asunto(s)
Flujometría por Láser-Doppler/métodos , Oximetría/métodos , Consumo de Oxígeno , Oxígeno/sangre , Flujo Sanguíneo Regional/fisiología , Vasos Retinianos/fisiología , Adulto , Femenino , Humanos , Masculino , Valores de Referencia , Vasos Retinianos/citología , Tomografía de Coherencia Óptica/métodosRESUMEN
BACKGROUND: Monitoring cerebral saturation is increasingly seen as an aid to management of patients in the operating room and in neurocritical care. How best to manipulate cerebral saturation is not fully known. We examined cerebral saturation with graded changes in carbon dioxide tension while isoxic and with graded changes in oxygen tension while isocapnic. METHODOLOGY/PRINCIPAL FINDINGS: The study was approved by the Research Ethics Board of the University Health Network at the University of Toronto. Thirteen studies were undertaken in healthy adults with cerebral oximetry by near infrared spectroscopy. End-tidal gas concentrations were manipulated using a model-based prospective end-tidal targeting device. End-tidal carbon dioxide was altered ±15 mmHg from baseline in 5 mmHg increments with isoxia (clamped at 110±4 mmHg). End-tidal oxygen was changed to 300, 400, 500, 80, 60 and 50 mmHg under isocapnia (37±2 mmHg). Twelve studies were completed. The end-tidal carbon dioxide versus cerebral saturation fit a linear relationship (R(2)â=â0.92±0.06). The end-tidal oxygen versus cerebral saturation followed log-linear behaviour and best fit a hyperbolic relationship (R(2)â=â0.85±0.10). Cerebral saturation was maximized in isoxia at end-tidal carbon dioxide of baseline +15 mmHg (77±3 percent). Cerebral saturation was minimal in isocapnia at an end-tidal oxygen tension of 50 mmHg (61±3 percent). The cerebral saturation during normoxic hypocapnia was equivalent to normocapnic hypoxia of 60 mmHg. CONCLUSIONS/SIGNIFICANCE: Hypocapnia reduces cerebral saturation to an extent equivalent to moderate hypoxia.