Prolongation of subarachnoid block for prolapsed intervertebral disc surgery by intra-operative subdural injection under direct vision

A 45 yearsold male, weighing 70 kg suffering from prolapsed intervertebral discs [PIVD] and was scheduled for decompression surgery at L3-L4, L4-L5 spinal levels. Spinal anesthesia was administered at L3-L4 interspace in the sitting position using 25gauge spinal needle and 3 ml of 0.5% hyperbaric bupivacaine was injected. The patient was turned prone after 5 min. After about two hours of surgery the patient complained of pain. A decision to administer spinal anesthesia again was undertaken as the dura mater was already exposed at the surgical site. Hyperbaric bupivacaine 1.5 ml was injected in the subarachnoid space under direct vision using 25G spinal needle. Adequate block was achieved and surgery was completed without