In spinal anesthesia, the "recession" of the block refers to the gradual wearing off (regression) of the medication, starting with the highest dermatome levels. Because visceral sensation is carried by unmyelinated C-fibers, this deep dull pain can sometimes break through long before somatic (incisional) pain wears off. Why Visceral Pain Returns During regression, the local anesthetic in the cerebrospinal fluid (CSF) dilutes and gets absorbed.
As concentrations fall: Fibers Reclaim Function: The unmyelinated C-fibers, which require a higher concentration of anesthetic to remain blocked, regain function faster than the larger myelinated A-delta fibers. Surgical Stimulation: Patients may still experience deep cramping, pressure, or vague discomfort (e.g., during uterine manipulation in a cesarean section) while remaining completely numb to superficial skin cuts. Factors Affecting…
