[The effect of puncture needle on the subarachnoid catheter position in continuous spinal ansthesia]

The subarachnoid position of the microcatheter has an impact on the outcome of continuous spinal anaesthesia (CSA). The present prospective, randomised study investigated the influence of two different spinal needles on the radiographically documented subarachnoid positions of microcatheters in CSA. In addition, the influence of the subarachnoid position of the microcatheter on onset time of analgesia, dose requirement of local anaesthetics, and level of analgesia was examined. METHODS. Forty orthopaedic patients received CSA using a 28-gauge spinal catheter inserted either through a non-directional 22-gauge Quincke needle (group 1) or a directional 22-gauge Sprotte needle (group 2). After initial injection of 2 ml to a maximum of 5 ml of supplemental doses of 0.5% plain bupivacaine, onset time of analgesia at the level of T 10, dose requirement of bupivacaine, and the achieved analgesic level were registered. After surgery, a dye-enhanced AP X-ray film of the lumbar spine was performed for radiological control of the subarachnoid catheter position. RESULTS. There was a higher number of cranial catheter positions in group 2 (60%) compared with group 1 (40%, P = 0.037). In contrast to group 1, with 35% caudally directed catheters, no catheter was seen in a caudal position in group 2. Onset time of analgesia (P = 0.0002) and anaesthetic dose requirement (P = 0.037) were lower in patients with cranially directed catheters compared to patients with the catheters situated at the level of the puncture site or in a caudal position. Maximal analgesic levels were higher in cranially directed catheters compared with other localisations (P = 0.022). CONCLUSIONS. Sprotte needles provide a higher number of cranially directed microcatheters, which are associated with faster onset of analgesia, lower dose requirement of local anaesthetics, and higher analgesic levels in CSA. The results suggest more effectiveness and probably more safety in microcatheter CSA using Sprotte needles for catheter insertion.