低碳酸血症在急性脑损伤中的研究进展

Research progress of hypocapnia in acute brain injury

摘要:

低碳酸血症是急性脑损伤（ABI）患者常见的病理生理异常，与中枢呼吸调控紊乱、应激反应、机械通气设置及医源性过度通气等因素密切相关。既往低碳酸血症常被作为短时降低颅内压的干预手段，但近年来研究显示，持续或明显降低的动脉二氧化碳分压（PaCO?）可通过降低脑血流量、限制脑组织氧释放及增强神经兴奋性等途径，加重继发性脑损伤并影响患者预后。目前，ABI后低碳酸血症的严重程度尚缺乏统一分级标准，其临床意义不应仅依据单次PaCO?阈值判断，而应综合考虑低碳酸血症的程度、持续时间、动态轨迹、暴露负荷以及不同ABI亚型的病理生理差异。在监测方面，动脉血气分析仍是诊断低碳酸血症的金标准，呼气末二氧化碳分压监测可用于连续趋势观察，但需结合动脉血气定期校准；对于脑缺血风险较高的患者，可联合颅内压、脑组织氧分压或近红外光谱技术等多模态监测，以指导个体化PaCO?调控。该文旨在回顾近年来ABI后低碳酸血症的相关研究，梳理这一并发症的发生、损伤机制、监测处理及面临的挑战，以期帮助人们加深理解和继续优化个体化管理。

Abstract:

Hypocapnia is a common pathophysiological abnormality in patients with acute brain injury (ABI) and is closely associated with impaired central respiratory regulation, stress responses, mechanical ventilator settings, and iatrogenic hyperventilation. Traditionally, hypocapnia has been used as a short-term intervention to reduce intracranial pressure. However, recent studies have shown that sustained or marked reductions in the arterial partial pressure of carbon dioxide (PaCO?) may aggravate secondary brain injury and affect patient outcomes by decreasing cerebral blood flow, impairing cerebral oxygen unloading, and increasing neuronal excitability. At present, there is no unified classification system for the severity of hypocapnia after ABI. Its clinical significance should not be determined solely by a single PaCO? threshold, but should be assessed comprehensively according to the degree and duration of hypocapnia, dynamic PaCO? trajectories, cumulative exposure burden, and pathophysiological differences among ABI subtypes. Regarding monitoring, arterial blood gas analysis remains the gold standard for diagnosing hypocapnia, whereas end-tidal carbon dioxide monitoring provides continuous trend information but requires regular calibration with arterial blood gas measurements. In patients at high risk of cerebral ischemia, multimodal monitoring, including intracranial pressure, brain tissue oxygen tension, and near-infrared spectroscopy, may be combined to guide individualized PaCO? regulation. This review summarizes recent research on hypocapnia after ABI, focusing on its occurrence, injury mechanisms, monitoring and management strategies, and current challenges, with the aim of improving understanding and further optimizing individualized management.