Near-Infrared Spectroscopy Cerebral Oxygen Saturation Thresholds for Hypoxia–Ischemia in Piglets

Abstract

Summary:Detection of cerebral hypoxia-ischemia remains problematic in neonates. Near-infrared spectroscopy, a noninvasive bedside technology has potential, although thresholds for cerebral hypoxia-ischemia have not been defined. This study determined hypoxic-ischemic thresholds for cerebral oxygen saturation (ScO 2 ) in terms of EEG, brain ATP, and lactate concentrations, and compared these values with CBF and sagittal sinus oxygen saturation (SvO 2 ). Sixty anesthetized piglets were equipped with near-infrared spectroscopy, EEG, laser-Doppler flowmetry, and a sagittal sinus catheter. After baseline, ScO 2 levels of less than 20%, 20% to 29%, 30% to 39%, 40% to 49%, 50% to 59%, 60% to 79%, or 80% or greater were recorded for 30 minutes of normoxic normocapnia, hypercapnic hyperoxia, or bilateral carotid occlusion with or without arterial hypoxia. Brain ATP and lactate concentrations were measured biochemically. Logistic and linear regression determined the ScO 2, , CBF, and SvO 2 thresholds for abnormal EEG, ATP, and lactate findings. Baseline ScO 2 was 68 + 5%. The ScO 2 thresholds for increased lactate, minor and major EEG change, and decreased ATP were 44 ± 1%, 42 ± 5%, 37 ± 1%, and 33 ± 1%. The ScO 2 correlated linearly with SvO 2 (r ‫ס‬ 0.98) and CBF (r ‫ס‬ 0.89), with corresponding SvO 2 thresholds of 23%, 20%, 13%, and 8%, and CBF thresholds (% baseline) of 56%, 52%, 42%, and 36%. Thus, cerebral hypoxia-ischemia near-infrared spectroscopy thresholds for functional impairment are ScO 2 33% to 44%, a range that is well below baseline ScO 2 of 68%, suggesting a buffer between normal and dysfunction that also exists for CBF and SvO 2 .

Tissue Oxygen Saturation Mapping with Magnetic Resonance Imaging

“…The pimonidazole staining is described to highlight deep-tissue hypoxia (pO 2 o10 mm Hg), 26 while in our experiment the MR_StO 2 values in the trauma area stayed above the limit of deep hypoxia (440%). 15 These data are thus consistent with the presence of a mild brain hypoxia in the impact-acceleration model that is not deep enough to retain pimonidazole. tumor and in the contralateral cortex were similar (4.0% ± 0.5% versus 4.5% ± 0.6%, P ¼ 0.082, respectively), while the ADC was higher in the tumor than in the contralateral cortex (1,184±79 versus 780±28 mm 2 /s, respectively, Po0.001).…”

“…26 In the most hypoxic rats of our gas challenge study, PbtO 2 was 6.2±1.6 mm Hg and SvO 2 was 41.4%±4.4%, in good agreement with the oxygen saturation threshold for tissue hypoxia found elsewhere. 15 Altogether, our results suggest that MR_StO 2 can be a surrogate marker of mild and severe tissue hypoxia. In patients with stroke, this could be useful to better delineate the ischemic penumbra, 35 as clinicians cannot currently clearly define the tissue at risk.…”

The effects of CO2-insufflation with 5 and 10 mmHg during thoracoscopy on cerebral oxygenation and hemodynamics in piglets: an animal experimental study

“…In order to draw valid conclusions, we used conservative statistical tests, which all became highly significant. Furthermore, piglets are not the same as neonates, with a lower cerebral oxygenation like we observed according to Kurth et al [24] and Chien et al [25]. However, we do think these results are representative as the trend of the cerebral oxygenation is more important than the absolute value [19].…”

Disfunción cognitiva después de cirugía cardiaca: Saturación cerebral e índice biespectral: estudio longitudinal

“…Dos estudios recientes han encontrado correlación entre desaturación cerebral y DCPO precoz 23,24 , no así con DCPO tardía. La SrO 2 C evalúa una muestra circunscrita de la corteza frontal, infl uida fundamentalmente por el componente venoso 56,57 . Las disminuciones de SrO 2 C refl ejarían una disminución relativa en la perfusión cerebral 55,58 .…”