A MULTIFACTORIAL ANALYSIS TO EXPLAIN INADEQUATE SURGICAL ANALGESIA AFTER EXTRADURAL BLOCK

A multivariate analysis of inadequate extradural analgesia was carried out prospectively on 1051 patients undergoing lumbar extradural anaes thesia for surgery performed on structures innervated by T10-S5. Ninet y-six patients (9%) experienced pain during surgery. Age, extradural f entanyl, diazepam sedation and duration of surgery had no significant influence. We found some weak evidence that the type of surgery affect s the risk of feeling pain. The probability of pain increased with inc reasing weight, except in overweight women, and was significantly grea ter for both shorter and taller patients, relative to patients of aver age height. The probability of pain decreased with increasing dose of local anaesthetic, increasing spread of extradural analgesia, addition of adrenaline, and fentanyl or thiopentone sedation. In conclusion, p atient-, surgery- and anaesthesia-related factors influence the risk o f inadequate extradural analgesia. If such factors are taken into acco unt, an increase in the success rate may be anticipated.