A directional needle improves effectiveness and reduces complications of microcatheter continuous spinal anaesthesia.

The present prospective randomized study compares the impact of two different spinal needle designs--non-directional versus directional--on the effectiveness of continuous spinal anaesthesia provided via a microcatheter in orthopaedic patients. Using the midline approach, a 28-gauge spinal catheter was inserted either through a 22-gauge Quincke needle (non-directional, Group 1, n = 21) or a 22-gauge Sprotte needle (directional, Group 2, n = 21) under standardized conditions. The incidence of technical difficulties and postoperative complaints, onset time of analgesia at the level of T10 and dose requirement of plain bupivacaine 0.5% were recorded. Postoperatively, the subarachnoid position of the catheters was radiographically evaluated. There was a higher incidence of technical problems during catheter insertion in Group 1 compared with Group 2 (71% vs 19%, P < 0.05). Onset time of analgesia was shorter (P < 0.05) and anaesthetic dose requirement was lower in patients in Group 2 than in Group 1. While 40% of the catheters were found in a caudal position in Group 1, all catheters were in a cranial position or at the level of the puncture site in Group 2 (P < 0.05). There was no difference in the incidence of postoperative complaints between the groups. The faster onset of analgesia and lower dose requirement of local anaesthetics associated with a lower incidence of technical problems suggest that there is greater effectiveness and safety when microcatheters are inserted using directional needles rather than non-directional needles.