Radiological examination of the intrathecal position of microcatheters in continuous spinal anaesthesia.

There have been few studies of the intrathecal position of spinal catheters in continuous spinal anaesthesia. This prospective study was designed to examine radiologically the intrathecal position of 28-gauge spinal catheters. We studied the entry into the subarachnoid space and the intrathecal position of 68 spinal catheters. In 50%, the catheters passed in a cranial direction, in 34% the catheters remained at the level of the puncture site and in 16% the catheters were directed caudally. The intrathecal position of the catheters did not depend on the level of the lumbar puncture (P = 0.6246), but was dependent on the position of the patient during insertion of the catheter (P = 0.0093), and on the depth of insertion (P = 0.0099). Our study suggests that patients should be in a sitting position during insertion of a subarachnoid microcatheter and that the depth of insertion should not exceed 4 cm.