最简单的解释是腰麻时硬膜外针未在硬膜外间隙。

The simplest explanation is that the epidural needle is not actually in the epidural space at the time of attempted spinal puncture.

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在使用硬膜外麻醉之前和之间，留置针经常性的被用来管理，以减少发生低血压的概率，这是无痛麻醉经常会出现的副作用。

IV fluids are routinely administered before and during the placement of an epidural to reduce the chance of a drop in blood pressure, a common side effect of this pain relief route.

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操作者使用胨x线(称为透视)的引导，可以看到针穿入颈椎硬膜外腔。

X-ray guidance, called fluoroscopy, is used so the practitioner can visualize the needle going into the cervical epidural space.

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