INFLAMMATORY CHANGES AFTER EXTRADURAL ANESTHESIA MAY AFFECT THE SPREAD OF LOCAL-ANESTHETIC WITHIN THE EXTRADURAL SPACE

We have assessed cephalad spread of analgesia in 491 patients undergoi ng extradural anaesthesia at the L2-3 or L3-4 interspace. Patients wer e classified into one of three groups based on the number of previous lumbar extradural anaesthesia procedures: none (group I, n = 339), one (group II, n = 82), and two or more (group III, n = 70). Cephalad spr ead of analgesia was greater in group I than in groups II and III, reg ardless of the puncture site. In addition, we examined the extradural space using a flexible extraduroscope in 32 patients who were excluded from the analysis of spread. Extraduroscopy showed the extradural spa ce to be patent in patients with no history of prior lumbar extradural anaesthesia, but it was not clearly identified in patients who had re ceived extradural anaesthesia one or more times because of aseptic inf lammatory changes, including proliferation of connective tissue, adhes ions between the dura mater and the ligamentum flavum, granulation and changes in the ligamentum flavum. Extradural anaesthesia may cause as eptic inflammatory changes in the extradural space which may reduce th e spread of analgesia.