Continuous spinal anesthesia: mechanical and technical problems of catheter placement

Although continuous spinal anesthesia with microcatheters has a number of advantages, there are also some drawbacks: technical problems in advancing the catheter, the possibility of traumatizing neural structures, the development of cauda equina syndrome, and maldistribution of the local anesthetic.

Spinaloscopy was performed with a 2-mm-diameter endoscope in fresh cadavers to visualize the fate of the catheters, as well as the distribution of the local anesthetic administered through these fine-bore catheters. Midline and paramedian approach achieved an easy insertion of the 28-gauge catheter as long as the 22-gauge needle was not advanced too far into the subarachnoid space, thereby making it impossible for the catheter to bend at the anterior wall of the dura mater.

Injection of methylene blue-colored hyperbaric local anesthetic through the catheter revealed an inhomogenous distribution with pooling in the caudal segments. After the catheter tip leaves the needle, the catheter should be advanced only 2-3 cm to avoid coiling, possible damage of the nerve roots, or malpositioning in preformed pouches.

To take advantage of continuous spinal anesthesia, a meticulous technique is required.