低容量性高钠血症.ppt

2021/3/27 * 2021/3/27 * 5）对心电图的影响 ①T波高尖:心肌细胞膜对K+的通透性增加,3期复极加快。Q-T间期缩短,动作电位时程缩短,复极加快，不应期缩短。 ②P波及QRS波增宽、P-R间期、P-Q间期延长:因为房室传导时间延长。 ③多种类型的心率失常:窦性心动过缓、窦性停博、各种传导阻滞、室颤等。 2021/3/27 * （2）对神经肌肉的影响 与对心肌的影响相似,轻度高钾血症（K+浓度为5.5～7.0mmol/L）时,静息膜电位降低,负值变小，骨骼肌细胞部分去极化，肌肉兴奋性增强，肌肉轻度震颤、刺痛和感觉异常。;重度高钾血症（K+浓度为7.0～9.0mmol/L）时，静息膜电位过小，钠通道失活，难以形成动作电位，肌肉不易兴奋，称为去极化阻滞（depolarized block）。表现为四肢软弱无力、发生迟缓性麻痹。 2021/3/27 * Et Em [K+] ↑ K+ Na+ Em 去极化阻滞（depolarized block） 2021/3/27 * Depolarization blocking In severe acute hyperkalemia, the resting membrane potential decreases and may fall close to the threshold potential. At this time, the cell membrane is too depolarized, which causes many voltage-gated Na+ channels to inactivate, and the action potential will not be initiated by any normal stimulus. That is, the irritability of the nerve and muscle cells is decreased. This phenomenon is termed depolarization blocking. 2021/3/27 * （3）对酸碱平衡的影响 因细胞外液K+与细胞内H+交换及肾小管上皮细胞K+-Na+交换增强而H+-Na+交换减弱等,故易诱发代谢性酸中毒。因一般酸中毒时,机体的代偿反应为增加肾脏排酸保碱使尿液呈酸性才对机体有益,但高血钾引起的酸中毒时机体排出碱性尿液，这种现象称为“反常性碱性尿”。 2021/3/27 * K+ K+ K+ H+ H+ H+ H+ K+ 反常性碱性尿 K+ K+ K+ K+ H+ 2021/3/27 * 4.防治的病理生理基础 （1）防治原发病; （2）血钾过高时常需紧急处理。重症者须降血钾以保护心脏,措施有: 1）对抗K+的毒性:静滴葡萄糖酸钙或高渗氯化钠、乳酸钠溶液 2）促进K+进入细胞内:使用碱性药、应用胰岛素+葡萄糖 3）促进K+从的排出：可从肠道途径（离子交换树脂）或透析疗法 * * * * * * * * * * * * * * * * * * * 2021/3/27 * K+ - + - + - + - + + + Na+ + 刺激 + - - 2021/3/27 * Et Em [K+] ↓ K+ Na+ Em 超极化状态 - + - + - + - + 2021/3/27 * Hyperpolarization blocking In acute hypokalemia, the ICF/ECF ratio of K+ concentration increases, and the K+ efflux out of cells increases, so the voltage of the membrane potential becomes more negative than the normal resting membrane potential. At this time, the membrane becomes hyperpolarized; the difference between the resting membrane potential and the threshold potential increases with the hyperpolarization of the cell membrane; the