Background: For surgery below the umbilicus, spinal anaesthesia is still the favoured choice of regional anaesthetic because it can be used to establish anaesthetic quickly, it allows for a reliable sensory blockade and motor blockade, there are excellent operating conditions during surgery, prolonged pain relief with fewer complications of general anaesthesia. Intrathecal local anaesthetics used most commonly include mepivacaine, bupivacaine, isobaric and hyperbaric, and this is the preferred choice. Depending on their density, these drugs affect whether or not will spread in CSF, rate of neural blockade, duration of anaesthesia and clinical effect. A number of factors

Spinal Anaesthesia, Isobaric Bupivacaine, Hyperbaric Bupivacaine, Intrathecal Fentanyl, Infraumbilical Surgery, Sensory Blockade, Motor Blockade.