1.What is hemianesthesia? The spinal nerves manage the sensation and movement of different parts of the body due to their different locations. Using this principle, we inject anesthetic from behind to temporarily block the action of certain spinal nerves in order to achieve the purpose of surgery on the area managed by the spinal nerves without the patient feeling pain. In this type of anesthesia, the patient does not lose consciousness, but only the lower half of the body cannot move, so it becomes hemianesthesia. 2.What are hemi-anesthesia? Subarachnoid sacral anesthesia: A very fine needle is used to inject anesthetic into the subarachnoid space where the spinal nerves are located to achieve the effect of blocking the spinal nerves. Epidural cavity block anesthesia: The anesthetic is injected into the epidural cavity with a fine needle (but thicker than that of spinal anesthesia) and acts directly on the spinal nerve roots. Its onset time is slower than that of spinal anesthesia, and the degree of blockage of sensory and motor nerves is smaller than that of spinal anesthesia, and selective blockage is carried out in a segmented manner, and the drug can be administered several times depending on the time and needs of anesthesia. 3.Will hemi-anesthesia hurt the spine? Because hemi-anesthesia is administered through the interspinal space to temporarily block nerves, it will not injure the spine. Because the needle is very small (23G~26G), there may be a slight local swelling and pain similar to intramuscular injection, which can be recovered in 1~2 days and will not cause after-effects of back pain. 4.What are the possible after-effects of hemi-anesthesia? Possible sequelae of hemi-anesthesia include urinary retention, nerve damage, infection, etc., but they are rare; the most common one is headache after subarachnoid block anesthesia (can be prevented by lying down for 24 hours after anesthesia). 5.Is it easy to have back pain after receiving hemi-anesthesia? The incidence of back pain after semi-body anesthesia is the same as that of general anesthesia, and most of them can be cured spontaneously. The effect of spinal anesthesia usually begins to wear off two hours after anesthesia, and it takes 8 hours before all sensation is fully restored. If you can keep lying down for 6 hours after anesthesia, drink more water after getting up, and slowly get out of bed to move around, you will not have back pain. 6.Why do I still feel the sensation after anesthesia? After anesthesia, many patients will ask the anesthesiologist this question. In fact, except for general anesthesia, most anesthesia methods do not affect the consciousness, the patient remains awake, and the nerve blocked area (anesthetized area) is not devoid of all sensations. Since most patients will be nervous to varying degrees after entering the operating room, the anesthesiologist will usually give appropriate medication to sedate the patient to sleep, so there is no need to worry at all.