The Evacuation of Pantopaque from the Lumbar Spinal Canal by Siphon Action

An important, often vexing, and sometimes painful aspect of myelography is the removal of the contrast material from the spinal canal. Kubik and Hampton (3) made myelography an acceptable procedure when they first reported on the aspiration of Lipiodol through the lumbar puncture needle left in situ during the examination. The effect of coughing and straining on the movement of fluid within the spinal canal was described by Reitan (4) and by Epstein (1). They observed that during such efforts the opaque column moved upward from 1 to about 5 or 6 cm. This was attributed to the compressive action of engorgement of the intraspinal veins which caused a squeezing pressure on the dural sac. Scott and Furlow (5) utilized this maneuver, the classical Valsalva experiment, to remove Pantopaque from the spinal canal by permitting it to flow out from the open needle while the patient strained. Today both technics are employed for the evacuation of Pantopaque after myelography. It is accepted that the removal of the medium is facilitated by having the needle tip directly in the midline and close to the bottom of the canal. Otherwise, only clear fluid or fluid mixed with Pantopaque is obtained. Our experience is that aspiration from capacious spinal canals is much easier than from those of lesser diameter. Easy evacuation of the contrast material from a wide canal with the needle tip quite off-center is not unusual. On the other hand, difficulty is often encountered in both the instillation and the withdrawal of Pantopaque from narrow spinal canals even if the needle tip is well centered. Canals with sagittal diameters less than 1.3 cm. present this problem most often (2). Not infrequently the first 1 or 2 c.c. of Pantopaque is removed easily. Then, despite all efforts, the flow stops. Rotation of the needle tip, reinsertion of the stylet, gentle aspiration or straining are of no avail. More forceful efforts produce nothing but pain and prove equally futile. When this happens, the author prefers to remove the needle and perform another tap, preferably at the lumbosacral interspace. The Pantopaque first is permitted to flow by gravity, and the remainder is aspirated or squeezed out. Recently, another method for the evacuation of Pantopaque from the spinal canal was evolved, employing the creation of a siphon. After the myelographic examination is completed and the spot-films are reviewed, the stylet is removed and the male end of a 50 cm. sterile Venotube is inserted into the hub of the needle. A stopcock is placed at the distal end of the Venotube, and the siphon action is started by having the patient strain or by gentle suction. Once the fluid is below the level of the spinal canal flow continues. The Pantopaque and fluid are collected in a sterile container. The entire procedure is performed under image intensification, which permits accurate judgment of the position of the medium in relation to the needle tip.