[每周一问]No.5之周中问：关于PONV
2014-12-14 19:58:10   来源：   作者：  评论：0 点击：

[每周一问]No.5之周中问：关于PONV

This week we'll be discussing one of the more frequent complications associated with anesthesia and surgery, postoperative nausea and vomiting (PONV). Today, we'll focus on the physiology of the problem.
1. What is the chemoreceptor trigger zone (CTZ) and what receptors are present there?
2. Are there other centers active in the production of PONV?
3. What is the function of the emetic/vomiting center (VC)?
4. What other efferent pathways are involved in the vomiting response?
本周我们讨论PONV的生理学问题。
1. 什么是催吐化学感受区（CTZ）？其受体主要是什么？
2. 在PONV发生过程中是否有其他中心的活动（感受区）？
3. 呕吐中枢（VC）的功能是什么？
4. 呕吐反射中还涉及到什么别的传出通路？
[每周一问]No.5之周中问：关于PONV 参考答案
1.什么是催吐化学感受区（CTZ）？其受体主要是什么？
催吐化学感受区（CTZ），是发挥化学感受功能的位于极后区的解剖学位置。如果不同类型的受体（下表）受到刺激，CTZ向呕吐中枢发送信号。CTZ可以在该区域没有有效血脑屏障存在情况下被化学刺激所激活，这些化学刺激来自血液或者脑脊液。
如图。
有趣的是，除了CTZ在呕吐中的重要性，与其他神经生理学中枢（比如呕吐中枢）相比，在产生呕吐的过程中没有直接电刺激现象。

2.在PONV发生过程中是否有其他中心的活动（感受区）？
许多其他中枢可能在PONV中发挥作用。孤束核富含脑磷脂、组织胺及毒蕈碱胆碱能受体。此外，已知胃肠道也包含有在CTZ发现的几种受体。最后，大量的内脏与躯体外周途径与之相关，包括第八对颅神经的前庭部。有趣的是，自从1882年发现一些聋人对于晕船具有免疫性，人们对前庭系统的兴趣逐渐增加。

3.呕吐中枢（VC）的功能是什么？
呕吐中枢，也被认为是细胞网状结构，位于髓质深部网状结构的侧面，和传入、传出到与呕吐相关的呼吸、胃肠、腹部肌肉系统的信号（主要来自于CTZ）相关。

4.呕吐反射中还涉及到什么别的传出通路？
控制膈肌与腹壁肌肉的传出神经系统象其他内脏和躯体结构一样，与呕吐反射直接相关。同时，许多颅神经(V, VIII, IX, X, XII)与呕吐相关。最后，交感和副交感反射发生，导致心率与血压的典型上升。


[每周一问]No.5之周中问：关于PONV 参考答案
What is the chemoreceptor trigger zone (CTZ) and what receptors are present there?
The chemoreceptor trigger zone is an anatomic site located in the area postrema which serves as a chemosensor. Should stimulation of its many different types of receptors (listed below) occur, the CTZ signals the vomiting center. The CTZ can be activated by chemical stimuli received either through the blood or cerebral spinal fluid, as no effective blood-brain barrier exists for this area.
Interestingly, in contrast to a number of other neurophysiologic centers (such as the vomiting center) and despite the importance of the CTZ to emesis, direct electrical stimulation has not been successful in producing emesis (1).

Are there other centers active in the production of PONV?
A number of other centers may play a role in PONV. The nucleus tractus solitarius is rich in encephalins and histaminic and muscarinic cholinergic receptors. In addition, the gastrointestinal tract is known to contain several of the receptors found in the CTZ (2). Finally, a number of the visceral and somatic pathways may contribute, including the vestibular portion of the 8th cranial nerve. Of interest, since the discovery in 1882 that some deaf people were immune to seasickness (3), interest in the vestibular system has grown.

What is the function of the emetic/vomiting center (VC)?
The vomiting center, also known as the parvicellular reticular formation, is located in the lateral reticular formation deep in the medulla and coordinates afferent inputs (mostly from the CTZ) and efferent signals to the respiratory, gastrointestinal and abdominal musculature involved in the process of vomiting (4).

What other efferent pathways are involved in the vomiting response?
The efferent nervous systems controlling the diaphragm and abdominal muscles as well as other visceral and somatic structures are directly involved in the vomiting response (3). In addition, a number of craniofacial nerves (V, VIII, IX, X, XII) contribute to emesis. Finally, sympathetic and parasympathetic responses occur, accounting for the increase in heart rate and blood pressure typically witnessed.

Question Author: Lawrence Tsen, MD, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School
References:
1. Borison HL. Area postrema: chemoreceptor circumventricular organ of the medulla oblongata. Prog Neurobiol 1989;32:351-90.
2. Bharucha AE, Camilleri M, Haydock S, et al. Effects of a serotonin 5-HT(4) receptor antagonist SB-207266 on gastrointestinal motor and sensory function in humans. Gut 2000;47(5):667-74.
3. McGoldrick KE. Postoperative nausea and vomiting. Probl Anesth 2000;12:274-86.
4. Andrews PL. Physiology of nausea and vomiting. Br J Anaesth 1992;69 (suppl): 2S-19S.



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