Etiology and Classification

病因与分类

There are several mechanisms of organ hypoperfusion and shock. Shock may be due to low circulating volume (hypovolemic shock), vasodilation (distributive shock), primary decrease in cardiac output (both cardiogenic and obstructive shock), or a combination.

器官血流灌注不足和休克可有多种机制引起。休克可能是由于低循环量（低血容量性休克)、血管舒张（分布性休克)、心排量基本下降（心源性休克和阻塞性休克)，或多种因素结合。

Hypovolemic shock: Hypovolemic shock is caused by a critical decrease in intravascular volume. Diminished venous return (preload) results in decreased ventricular filling and reduced stroke volume. Unless compensated for by increased heart rate, cardiac output decreases.

低血容量性休克：低血容量性休克是由血管内容量严重下降引起的。静脉回流减少（前负荷)导致心室充盈下降和每搏量减少。如果增加心率仍不能代偿，心排量就会减少。

A common cause is bleeding (hemorrhagic shock), typically from trauma, surgical interventions, peptic ulcer, esophageal varices, or aortic aneurysm. Bleeding may be overt (eg, hematemesis or melena) or concealed (eg, ruptured ectopic pregnancy).

常见原因有出血（出血性休克)，主要是有外伤、手术、消化性溃疡、食管静脉曲张或主动脉瘤等引起。出血有明显出血（如呕血、黑粪症)或隐性出血（如异位妊娠破裂)。

Hypovolemic shock may also follow increased losses of body fluids other than blood (see Table 1: Shock and Fluid Resuscitation: Hypovolemic Shock Caused by Body Fluid Loss).

除失血外，体液丢失增加后也会出现低血容量性休克（见表1：休克和体液复苏：体液丢失引起的低血容量性休克)。

Hypovolemic shock may be due to inadequate fluid intake (with or without increased fluid loss). Water may be unavailable, neurologic disability may impair the thirst mechanism, or physical disability may impair access.

低血容量性休克也可能是由于液体摄入不足（伴或未伴体液丢失增加)。缺水、神经功能障碍损伤渴感机制，或身体健康状况影响用水。

In hospitalized patients, hypovolemia can be compounded if early signs of circulatory insufficiency are incorrectly ascribed to heart failure and fluids are withheld or diuretics are given.医学全在线www.med126.com

住院病人循环功能不全的早期症状若被误诊为心力衰竭，并因此而停止补液或给服利尿剂，可致低血容量加剧。

Distributive shock: Distributive shock results from a relative inadequacy of intravascular volume caused by arterial or venous vasodilation; circulating blood volume is normal. In some cases, cardiac output (and DO2) is high, but increased blood flow through arteriovenous shunts bypasses capillary beds, causing cellular hypoperfusion (demonstrated by decreased O2 consumption). In other situations, blood pools in venous capacitance beds and cardiac output falls.

分布性休克：分布性休克源于因动脉或静脉扩张引起的血管内容量的相对不足，其循环血量正常。有些病例的心排量（和DO2)高，但通过动静脉分路使更多的血流绕过毛细管床，造成细胞性血流灌注不足（表现为O2消耗下降)。其他病例则见静脉容量床血液积聚，心排量下降。

Distributive shock may be caused by anaphylaxis (anaphylactic shock); bacterial infection with endotoxin release (septic shock); severe injury to the brain or spinal cord (neurogenic shock); and ingestion of certain drugs or poisons, such as nitrates, opioids, and adrenergic blockers. Anaphylactic shock and septic shock often have a component of hypovolemia as well.

分布性休克可能原因有：过敏症（过敏性休克)、细菌性感染伴内毒素释放（败血症性休克)、大脑或脊髓严重损伤（神经性休克)和摄食某些药物或毒物，如硝酸盐、类罂粟碱及肾上腺素能神经阻断药等。过敏性休克和败血症性休克也会出现血容量不足。

Cardiogenic and obstructive shock: Cardiogenic shock is a relative or absolute reduction in cardiac output due to a primary cardiac disorder. Mechanical factors that interfere with filling or emptying of the heart or great vessels explain obstructive shock. Causes are listed in Table 2: Shock and Fluid Resuscitation: Mechanisms of Cardiogenic and Obstructive Shock.

心源性和阻塞性休克：心源性休克是缘于初期心脏疾病心排量的相对或绝对减少。影响心脏或大血管充盈或排空的机械因素可说明阻塞性休克的原因。原因见表2：心源性和阻塞性休克机制。