Abstract

Introduction

CSF was discovered by Domenico Catugno in 1764. First spinal anesthesia was given by J Leonard Coming in the year 1885. First planned spinal analgesia was given by August Bier on 11th August 1898. Local anesthetic solution injected into the subarachnoid space blocks conduction of impulses along all nerves with which it comes in contact, although some nerves are most easily blocked than others. Stimulation of motor nerves causes muscle paralysis. Generally autonomic and sensory fibers are blocked before motor fibers. Local anesthetic interacts with the receptors situated within the voltage sensitive sodium channels and raises the threshold of channel opening thereby decreasing the entry of sodium ions during upstroke of action potential. Local depolarization fails to reach the threshold potential and conduction block ensues. Intrathecal local anesthetics act on the neurons of the sacral spinal cord segments (S2–S4) by blocking the transmission of the afferent and efferent action potentials on the nervous fibers from and to the bladder. The detrusor contraction (detrusor block) is completely abolished 2–5 min after the injection of spinal anesthesia, and its recovery depends on the duration of sensory block above the S2 and S3 sacral segments. Fifteen minutes after the level of analgesia regressed to L5 or lower (S2–S3), the strength of detrusor starts to return to normal values, allowing the patient to void. Complete normalization of detrusor strength occurs 1–3.5 h after ambulation. Several studies have been conducted to study the risk factors for post subarachnoid block urinary retention.