Abstract

Spinal anesthesia is a widely used technique in medical practice nowadays. Generally, nervous blockage is determined by three main factors. The first of them is the distribution of the local anesthetic in the cerebrospinal fluid (CSF), which can be affected by numerous factors, the most important of them being CSF volume. The second is absorption, which is greatest at the sites with higher drug concentration: this is the result of the accessibility, lipidic content and vascular irrigation of each area. The last of these factors is elimination, mediated mainly by the irrigation of the different compartments, and whose order differs from the mirror image of the onset's action order. The previously mentioned elements are the main sources of variation for the time needed to achieve desired effects, order in which fibers are affected and differential blockage. This text describes the principal mechanisms through which spinal anesthesia works, and the factors which can result in variations of its results.