低钾血症,新PPT演示.ppt

Hypokalemia
苏颋为 MD
上海交通大学医学院附属瑞金医院内分泌代谢科上海内分泌代谢病研究所上海市内分泌代谢病临床医学中心上海市瑞金二路197号 200025
STW11102@
Shanghai Clinical Center for Endocrine and Metabolic Diseases; Shanghai Institute of Endocrine and Metabolic Diseases; Department of Endocrine and Metabolic Diseases, Ruijin Hospital, School of medicine, Shanghai Jiao-Tong University.  Ruijin Er Road, Shanghai, 200025
血钾稳态的维持
Key Hormones Involved in Normal Potassium Homeostasis.
Insulin and b-adrenergic catecholamines promote the entry of potassium into muscle cells by stimulating NA+/K+–ATPase. Aldosterone promotes potassium excretion through its effects on NA+/K+–ATPase and epithelial sodium and potassium channels in collecting-duct cells.
Angiotensin II has a synergistic effect on the stimulation of aldosterone production induced by hyperkalemia. Plus signs denote stimulation, and minus signs inhibition. Modified from Gennari
Thyroid hormone
低钾血症对神经肌肉、心肌的影响
膜电位
The Effects of Serum K+ Concentration on Neuromuscular Irritability
State Em Et (Em-Et) Neuromuscular Irritability
Normal -90 -65 25 Normal
Hypokalemia ↑(more negative) -65 ↑(Hyperpolarization) ↓
Hyperkalemia ↓(less negative) -65 ↓(partial depolarization) ↑→↓
低钾血症对神经肌肉、心肌的影响
■单纯低钾血症
膜电位异常(骨骼肌弛缓性麻痹和心率失常)
■机体缺钾
细胞代谢障碍
■缺钾、低钾血症
酸碱异常
低钾血症对神经肌肉、心肌的影响
低钾血症对神经肌肉、心肌的影响
-肌肉兴奋性的影响
轻度(血清钾<) 四肢无力、肠蠕动↓、肠鸣音
重度(血清钾<) 软瘫肌张力↓、腱反射消失、呼吸肌麻痹
■急性低钾血症
[K+]e↓、[K+]i不变[K+]i /[K+]e↑细胞内K+外移↑ Em负值增大骨骼肌、平滑肌超级化阻滞状态兴奋性↓ Em-Et间距↑
■慢性低钾血症
细胞内外的钾离子浓度相对平衡——骨骼肌、平滑肌超级化阻滞状态不明显
低钾血症对神经肌肉、心肌的影响
■传导性(Conduction)
[K+]e↓静息Em负值变小 Em-Et间距缩小
0期除极化幅度、速度↓
兴奋扩布↓心肌传导性↓
■收缩性(Contraction)
急性低钾血症
2期膜对Ca2+通透性↑ Ca2+内流加速收缩性↑
慢性低钾血症细胞内缺钾收缩性↓
(2)心电图( Electrocardiogram, ECG)特征
■ QRS波增宽
[K+]e↓传导性↓ P-R间期延长 QRS波(轻度)增宽。
■ ST段下降
[K+]e↓ K+通透性↓、Ca2+内流↑ ST段不能回基线而呈斜线状
低钾血症对神经肌肉、心肌的影响
■ T波低平
[K+]e↓膜K+的通透性↓心肌超长期延长 T波低平
[K+]e↓ Purkinje纤维3期复极化延长 U波增高
■自律性增高
■低钾血症时心律失常的表现
易发生早搏、房室传导阻滞、心室纤维颤动等表现。
原因:心肌兴奋性↑、超常期延长、异位起搏点、兴奋折返。
低钾血症对神经肌肉、心肌的影响