<unk> , (or commonly called<unk>  anesthesia) is a form of regional anaesthesia involving injection of a local anaesthetic into the cerebrospinal fluid (CSF), generally through a long, fine needle.
There are hyperbaric, isobaric, hypobaric solutions of anesthetics to choose for the<unk>  anesthesia. Usually, the hyperbaric is chosen. Bupivacaine is the local anesthetic most commonly used, although lignocaine, ropivacaine, levobupivicaine and cinchocaine are also available.  Regardless of the anaesthetic agent used, the desired effect is to block the transmission of nerve signals to and from the affected area.  Sensory signals from the site are blocked, thereby eliminating pain, and motor signals to the area eliminate movement.  In effect, the result is total numbness of the area and paralysis.  This allows medical procedures to be performed with little or no sensation whatsoever to the person undergoing the procedure, and provides a still patient or area for the surgeon to work on.  Some sedation is sometimes provided to help the patient relax and pass the time during the procedure, but with a successful<unk>  anesthetic the surgery can be performed with the patient wide awake.<unk>  anesthetics are limited to procedures involving most structures below the upper abdomen, as to administer a<unk>  anesthetic higher may affect the ability to breathe by paralyzing the intercostal respiratory muscles, or even the diaphragm in extreme cases (called a "high<unk> ", or a "total<unk> ",  with which consciousness is lost), as well as the body's ability to control the heart rate via the cardiac accelerator fibers.
Baricity refers to the density of a substance compared to the density of human cerebral<unk>  fluid. Baricity is used in anesthesia to determine the manner in which a particular drug will spread in the intrathecal space.
Spinal analgesia
Regional anesthesia
Local anesthesia
General anaesthetic
General anaesthesia
Anesthesia
Trifascicular block
Pain management