Editing Anesthesia (section)

==== Spinal, epidural and caudal anesthesia ====
{{Further|Neuraxial blockade|History of neuraxial anesthesia}}

[[Neuraxial blockade|Central neuraxial anesthesia]] is the injection of [[local anesthetic]] around the [[spinal cord]] to provide analgesia in the [[abdomen]], [[human pelvis|pelvis]] or [[Human leg|lower extremities]].  It is divided into either spinal (injection into the [[subarachnoid space]]), epidural (injection outside of the subarachnoid space into the [[epidural]] space) and caudal (injection into the [[cauda equina]] or tail end of the spinal cord).  Spinal and epidural are the most commonly used forms of central neuraxial blockade.

[[Spinal anesthesia]] is a "one-shot" injection that provides rapid onset and profound sensory anesthesia with lower doses of anesthetic, and is usually associated with [[neuromuscular blockade]] (loss of muscle control). [[Epidural anesthesia]] uses larger doses of anesthetic infused through an indwelling catheter which allows the anesthetic to be augmented should the effects begin to dissipate. Epidural anesthesia does not typically affect muscle control.

Because central neuraxial blockade causes [[arterial]] and [[venous]] [[vasodilation]], a drop in [[blood pressure]] is common. This drop is largely dictated by the venous side of the [[circulatory system]] which holds 75% of the circulating [[blood volume]].  The physiologic effects are much greater when the block is placed above the 5th [[thoracic vertebrae|thoracic vertebra]].  An ineffective block is most often due to inadequate [[anxiolysis]] or [[sedation]] rather than a failure of the block itself.<ref name="Miller 2010" />{{rp|1611}}