Near-infrared spectroscopy: a tool to monitor cerebral hemodynamic and metabolic changes after cardiac arrest in rats

Introduction: Cardiac arrest (CA) is associated with poor neurological outcome and is associated with a poor understanding of the cerebral hemodynamic and metabolic changes. The objective of this study was to determine the applicability of near-infrared spectroscopy (NIRS), to observe the changes in cerebral total hemoglobin (T-Hb) reflecting cerebral blood volume, oxygenation state of Hb, oxidized cytochrome oxidase (Cyto-C), and brain water content following CA. Methods: Fourteen rats were subjected to normothermic (37.5 °C) or hypothermic (34 °C) CA induced by 8 min of asphyxiation. Animals were resuscitated with ventilation, cardiopulmonary resuscitation (CPR), and epinephrine (adrenaline). Hypothermia was induced before CA. NIRS was applied to the animal head to measure T-Hb with a wavelength of 808 nm ( n = 10) and oxygenated/deoxygenated Hb, Cyto-C, and brain water content with wavelengths of 620–1120 nm ( n = 4). Results: There were no technical difficulties in applying NIRS to the animal, and the signals were strong and consistent. Normothermic CA caused post-resuscitation hyperemia followed by hypoperfusion determined by the level of T-Hb. Hypothermic CA blunted post-resuscitation hyperemia and resulted in more prominent post-resuscitation hypoperfusion. Both, normothermic and hypothermic CA resulted in a sharp decrease in oxygenated Hb and Cyto-C, and the level of oxygenated Hb was higher in hypothermic CA after resuscitation. There was a rapid increase in brain water signals following CA. Hypothermic CA attenuated increased water signals in normothermic CA following resuscitation. Conclusion: NIRS can be applied to monitor cerebral blood volume, oxygenation state of Hb, Cyto-C, and water content following CA in rats. Introdução: A paragem cardı́aca (CA) está associada a maus resultados neurológicos, parcialmente devido a uma má compreensão das alterações hemodinâmicas e metabólicas cerebrais. O objectivo deste estudo foi determinar a aplicabilidade da espectroscopia próximo do infra-vermelho (NIRS), para observar as alterações na hemoglobina total (T-Hb) cerebral, reflectindo o volume sanguı́neo cerebral, o estado de oxigenação da Hb, a citocromo oxidase oxidada (Cyto-C) e o conteúdo cerebral de água após CA. Métodos: 14 ratos foram submetidos a CA normotérmica (37.5°) ou hipotérmica (34°) induzida por 8 minutos de asfixia. Os animais foram reanimados com ventilação, reanimação cárdio-pulmonar (RCP) e epinefrina. A hipotermia foi induzida antes