Fig. 19.1
Placement of intrathecal catheter through Tuohy needle after accessing CSF. Note: Black suture is purse-string placed around needle as it passes through fascia which, at this point, remains untied
Once the fascial entry site is prepared, the intrathecal catheter is placed under fluoroscopic guidance (Fig. 19.2). The ideal location of the catheter tip is dorsal to the spinal cord. Frequently, placement is quite smooth and the proper spinal level is easily attained. However, it is useful to know strategies for those cases in which this is not the case. The CSF space changes with the cardiac cycle. Sometimes, attempting to advance the catheter in time with the audible pulse oximeter can allow the catheter to advance during the phase of maximal thecal sac diameter. Another technique involves gross manipulation of the patient’s shoulder in a dorsoventral plane while advancing the catheter, changing the orientation of the catheter within the thecal sac and sometimes allowing it to pass through an area of obstruction. Lastly, spinning the hub of the catheter—with or without placing a small bend in the tip of the stylet—can sometimes allow the catheter to find a path through the obstruction. Once the catheter tip is at the appropriate level, the stylet and needle are withdrawn and intrathecal placement, if needed, is verified using contrast (e.g., iohexol) and subtraction fluoroscopy.
Fig. 19.2
Radio-opaque intrathecal catheter after cervical placement
Pump Pocket and Tunneling
In creating the pump pocket, it is important to maintain the manufacturer-recommended depth from the skin surface to facilitate communication and refills. If at all possible, it is optimal to expose the pocket along the fascia to allow for adequate anchoring, thereby preventing “flipping” of the pump. Meticulous hemostasis is required to reduce the incidence of pocket hematoma. Once this has been achieved, four non-absorbable sutures are placed in the quadrants of the pocket, secured to the fascia. The catheter is tunneled subcutaneously into the pump pocket with care to maintain a subcutaneous level. Too shallow placement can result in pain and erosion; too deep placement when tunneling between the back and the abdomen can result in soft tissue injury and/or entry into the peritoneal cavity (see below).
Once the catheter is in the pump pocket, the pump is attached to its proximal end and placed into the pocket (Fig. 19.3). Excess catheter is coiled underneath the pump to reduce the possibility of damaging it during pump needle access. Vancomycin powder can be placed prior to pump placement (see below). Once the pump and catheter are in their final position, the catheter is accessed using the appropriate needle and the proper port and enough CSF are withdrawn to confirm catheter patency and empty it of any residual dye. A multilayered, tension-free closure is performed on both the pocket and the catheter incision, with particular attention to a watertight closure of the lumbar incision.
Fig. 19.3
Pump within pump pocket. Anchoring sutures are being tied
Infection Prevention
Infection of an IDD system is a potentially preventable complication that can have devastating consequences. Not only is there significant clinical risk, possibly including meningitis, but there are also psychological consequences of having to remove a successful implant and the economic costs of ultimately replacing the system. Therefore, infection prevention is exceedingly important.
The mainstay of infection prevention, as is true for most surgical procedures, is meticulous attention to tissue handling, hemostasis, and closure. Preoperative antibiotics should be dosed and timed appropriately. Excessive cautery, resulting in retained dead tissue, should be avoided. An iodine-impregnated surgical adhesive drape should be used, as well as silver-impregnated surgical bandages.
There are several low-cost techniques that will almost certainly result in a lower infection rate, although no high-quality clinical data on these strategies have been collected. Frequent and copious irrigation with antibiotic solution is recommended, along with stapling antibiotic-soaked sponges to the skin edges of each incision prior to placing any material that will remain in the body after closure. Vancomycin powder is inexpensive and can be used in both the pump pocket and catheter incision.
Revision Strategies
Revision of an IDD system can range from a simple pump replacement to a diagnostic exploration. The general principles are the same as with primary implantation. Low-energy electrocautery can be quite helpful and expeditious in dissecting out catheter embedded in scar without damaging it. At times, it may be necessary to place a new intrathecal catheter, in which case the prior catheter can be tied off and left in place, avoiding the significant risk of persistent CSF leak if it is removed. If removal is necessary and the track to the dura is persistent, fibrin glue injection down that track prior to closing it can be helpful in preventing a CSF leak.
Documentation
Adequate documentation of the implant procedure is necessary, both to provide information to the implanter in the future and to provide a new health care provider with enough information to care for the patient. Minimally, the operative note should include the precise system being implanted, the final spinal level of the catheter tip, and whether it is dorsal or ventral to the spinal cord. This latter information can be important in interpreting new neurological symptoms. This same information, along with the name of the implanter and date of implantation, can often also be placed into memory on the pump, providing an emergency backup if the operative note is unavailable.
Special Circumstances
Tunneled Externalized Catheter for Palliation
For end-of-life palliation, as well as for permanent catheter trials (see above), it may be desirable to place an externalized, tunneled intrathecal catheter and connect it to an external pump [4, 5]. This can be very cost effective when the patient’s life expectancy is short and, if done properly, can be internalized to an implanted pump if the clinical situation significantly changes (or the trial is successful).
The catheter implantation procedure for an externalized catheter is described above. A small incision is made in another area, often a smaller incision along the course of that which would be used for pump placement, if applicable. The catheter is tunneled subcutaneously into the second field; an extension is attached, brought out through a separate stab incision, and attached to a pump. Attachment of the catheter to the external pump tubing can be challenging and require ingenuity, as there is no standard system for achieving this.
If pump implantation is desired, the anticipated pump incision is prepped and the exit site of the catheter is draped out of the field. The pump incision is made, the catheter exposed, and the extension disconnected and removed by the circulating nurse from outside the sterile field. Implantation of the pump can then proceed as usual.
Open Catheter Placement via Laminotomy
On rare occasion, placement of an intrathecal catheter using a needle-based technique is impossible. If warranted, a catheter can be placed under direct visualization via laminotomy using standard neurosurgical principles. In such cases, a purse-string suture in the dura around the catheter can often help to prevent persistent CSF leak.
C1/2 Puncture for Catheter Placement
Even less common are cases requiring placement of the catheter through a C1/2 puncture (Fig. 19.4). The principles as outlined above are similar, although steering the catheter caudally to the desired level can be challenging because of the necessary perpendicular angle of the needle.
Fig. 19.4
C1/2 placement of intrathecal catheter. The catheter can be seen exiting the needle (black arrows) and being placed caudally to the T1/2 level (inset, blue arrows)
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