Comparison of hyperbaric solutions of bupivacaine and tetracaine during continuous spinal anaesthesia

The aim of this study was to compare two equipotent solutions of hyperbaric bupivacaine and tetracaine in 30 elderly patients undergoing elective hip surgery under continuous spinal anaesthesia. With the patient in the supine position, 2 ml (8 mg) of either hyperbaric solution (density 1.030) were administered in a double-blind and randomized fashion. The median maximum sensory and temperature discrimination levels (T5 and T4) were similar with both solutions. The duration of analgesia was not different (114 +/- 23 min for bupivacaine and 125 +/- 35 min for tetracaine). Thirteen out of fifteen patients receiving bupivacaine and all 15 patients receiving tetracaine had complete motor blockade. The haemodynamic changes and vasopressor requirements were comparable. The plasma catecholamine levels measured at four different times remained unchanged and were not different between the two groups at any time. The authors conclude that, during continuous spinal anaesthesia, equipotent hyperbaric solutions of bupivacaine and tetracaine have similar anaesthetic and haemodynamic effects.