Departments of Pediatrics, Physiology, and Medicine, The Maria Fareri Children’s Hospital, NY, USA.
Pediatrics. 2013 May;131(5):968-80. doi: 10.1542/peds.2012-2610. Epub 2013 Apr 8.
The autonomic nervous system, adequate blood volume, and intact skeletal and respiratory muscle pumps are essential components for rapid cardiovascular adjustments to upright posture (orthostasis). Patients lacking sufficient blood volume or having defective sympathetic adrenergic vasoconstriction develop orthostatic hypotension (OH), prohibiting effective upright activities. OH is one form of orthostatic intolerance (OI) defined by signs, such as hypotension, and symptoms, such as lightheadedness, that occur when upright and are relieved by recumbence. Mild OI is commonly experienced during intercurrent illnesses and when standing up rapidly. The latter is denoted "initial OH" and represents a normal cardiovascular adjustment to the blood volume shifts during standing. Some people experience episodic acute OI, such as postural vasovagal syncope (fainting), or chronic OI, such as postural tachycardia syndrome, which can significantly reduce quality of life. The lifetime incidence of ≥1 fainting episodes is ∼40%. For the most part, these episodes are benign and self-limited, although frequent syncope episodes can be debilitating, and injury may occur from sudden falls. In this article, mechanisms for OI having components of adrenergic hypofunction, adrenergic hyperfunction, hyperpnea, and regional blood volume redistribution are discussed. Therapeutic strategies to cope with OI are proposed.
自主神经系统、充足的血容量以及完整的骨骼和呼吸肌泵是快速心血管适应直立姿势（体位）的重要组成部分。血容量不足或交感肾上腺素能血管收缩功能缺陷的患者会出现体位性低血压（OH），从而无法进行有效的直立活动。OH 是体位不耐受（OI）的一种形式，其特征为直立时出现低血压和头晕等症状，平卧后缓解。轻度 OI 常见于偶发性疾病和快速站立时。后者称为“初始 OH”，代表直立时血液容量变化的正常心血管适应。有些人会间歇性地出现急性 OI，如体位性血管迷走神经性晕厥（晕厥），或慢性 OI，如体位性心动过速综合征，这会显著降低生活质量。≥1 次晕厥发作的终生发生率约为 40%。大多数情况下，这些发作是良性和自限性的，尽管频繁的晕厥发作可能使人虚弱，并且突然跌倒可能会受伤。本文讨论了 OI 的发生机制，其包括肾上腺素能功能低下、肾上腺素能功能亢进、过度通气和区域性血容量再分布等成分。还提出了应对 OI 的治疗策略。
