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Surgical Technique: Intrathecal Medication Delivery System Implantation
C H A P T E R
40 Surgical Technique: Intrathecal Medication Delivery System Implantation Joshua M. Rosenow Northwestern University Feinberg School of Medicine, Chicago, IL, United States
O U T L I N E Surgical Planning/Preoperative Considerations
537
Closure541
Positioning and Surgical Preparation
538
Postoperative Considerations
Catheter Insertion
539
References541
Pump Preparation and Insertion
540
SURGICAL PLANNING/PREOPERATIVE CONSIDERATIONS Planning for the implantation of an implantable drug delivery system (IDDS) requires considerations for the prevention of hardware infection, ergonomics of system function and comfort of the patient, prevention of pump pocket and catheter complications, and prevention of cerebrospinal fluid (CSF) leak. An IDDS consists of an intrathecal (IT) segment of catheter, a subcutaneous segment of catheter, and an implanted pump. The IT and subcutaneous catheter segments may be either part of the same catheter (one-piece catheter) or separate catheters joined with a connecting pin (two-piece catheter system). The choice of either a one-piece catheter or two-piece catheter system is determined by the preference of the implanter. A one-piece catheter eliminates the need for connecting pins and the related considerations that go with connecting two catheters together including assuring that the two catheters will not pull apart, etc. A one-piece catheter is also longer in total length than the IT segment of the two-piece system and thus can be used to reach higher vertebral levels (upper thoracic or cervical) that may be difficult
Neuromodulation, Second Edition http://dx.doi.org/10.1016/B978-0-12-805353-9.00040-1
541
to reach with a two-piece catheter system. Conversely, a two-piece catheter system may be easier to handle when revising the IT catheter because the IT portion may be disconnected and interrogated in the back, unlike the one-piece system, which must be cut and then connected with a new connecting pin following open interrogation or replacement of part, unless an entirely new one-piece catheter is implanted. There are newer two-piece catheter systems that are longer (like the one-piece systems) and are segmented into a very long section that is implanted into the IT space and then tunneled to the abdomen and a very short section that essentially becomes only the pump connector. Given that the pump footprint is somewhat large, the placement location of the pump is not a small consideration both technically and, to the patient, cosmetically and ergonomically. The most common programmable pump for implantation in the United States is the Synchromed II (Medtronic, Inc., Minneapolis, MN), which comes in two sizes and holds either 20 mL or 40 L of medication. It is my opinion that when using these programmable pumps, patients should be shown models of each pump so that they can grasp the magnitude of the implanted device and can express their opinion as to
537
© 2018 Elsevier Ltd. All rights reserved.
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40. SURGICAL TECHNIQUE: INTRATHECAL MEDICATION DELIVERY SYSTEM IMPLANTATION
which size they prefer, understanding that the smallercapacity pump must be refilled more often. These two pumps have the same footprint, but the actual thickness difference between the two pumps is not great: 19.5 versus 26 mm, respectively. The Prometra II pump (Flowonix Medical, Mt. Olive, NJ) is 69 mm in diameter and 24 mm thick and holds 20 mL. The patient should be queried as to the usual location of the waistband of their pants, as it is desirable to prevent this from rubbing on the pump and contributing to erosion of the hardware through the skin. The pump should be sited on the patient in both the supine and seated positions, to ensure that it will be placed in a position that is comfortable for the patient. The pump should affect neither the lower costal margin nor the iliac crest. For most patients, the pump may be comfortably placed in a paramedian location with the superior aspect near the level of the umbilicus, adjusted as needed for individual anatomy. When possible, the site of implant should be chosen so as to avoid other implanted devices such as ventriculoperitoneal shunts, gastrostomy tubes, and other implantable devices such as an implantable pulse generator for spinal cord stimulation. If a pump is being reimplanted following removal of a prior one due to infection, it is desirable to use the contralateral abdomen if possible. While pump pocket or hardware infections are rarely life threatening, they result in interruptions in therapy, further trips to the operating room, increased healthcare costs, and frustration for all involved. It is rare to salvage an infected pump, although there are reports of this salvage occurring in the literature (Atiyeh et al., 2006). Patients must be free of infection at the time of implantation. This includes urinary and respiratory tract infections, as well as infected decubitus or other skin ulcers. Most pump infections are due to skin contaminants, such as Staphylococcus sp. Preoperative bathing for several days with a solution containing chlorhexidine gluconate may decrease skin colonization with both sensitive and antibiotic resistant organisms (Motta et al., 2007). Intranasal mupirocin ointment, twice daily, may help decrease the rate of intranasal carriage of resistant Staphylococcus sp. (Mehtar, 1998; Sanderson, 2001). Antibiotics such as cefazolin or oxacillin, which cover common skin organisms, are usually sufficient for prophylaxis; however, some physicians recommend that all patients be given vancomycin preoperatively to cover methicillin-resistant Staphylococcus aureus (MRSA) bacteria. It is my opinion that preoperative cross-sectional imaging studies (either magnetic resonance imaging [MRI] or computed tomography [CT]) should be obtained from the planned catheter insertion site to the proposed tip location so that the surgeon may have advance knowledge of any anatomic variants or barriers to catheter insertion or passage. The level of the conus should be noted.
POSITIONING AND SURGICAL PREPARATION The patient is placed on the operating table in the supine position. After the induction of general endotracheal anesthesia, the pump implant site is then marked on the abdomen (if this has not been done before coming to the operating room). It is important to do this before the patient is turned into the lateral decubitus position, as the abdominal skin can shift greatly, especially if the patient has a pendulous abdomen. The patient is turned into the lateral decubitus position with the planned pump implant side up. An axillary roll is placed to relieve traction and pressure on the brachial plexus. Padding is also placed between all bony protuberances to prevent pressure and possible sequelae including pressure sores. Both arms are placed such that they are as far superiorly as is comfortably possible for the patient. This facilitates visualization of the spine and catheter with fluoroscopy. The lower arm is either placed on an arm board and the upper one on an “airplane-type,” arm holder or both arms, separated by padding, are placed in the “praying mantis” position and secured in that position. Each arm is thoroughly padded to prevent pressure on the ulnar nerves. Some surgeons secure the patient in the lateral decubitus position using wide cloth tape, and some secure the patient in that position using a “beanbag.” If a beanbagtype pad is used, it may be wrapped around the patient and suction applied to harden it and support the patient. Care should be taken in doing this so that neither the lumbar nor the abdominal operative site is obscured by the bean bag. The beanbag should not rise as high as the lumbar spinous processes or the umbilicus. Care should also be taken to ensure that sharp points to not cut into the patient. Sturdy fabric tape is applied across the patient’s hips (padded as well) to prevent rotation during the procedure. The fluoroscope is brought in, and anteroposterior images are obtained. The fluoroscope should be aligned to the patient’s spinal anatomy such that the spinous processes are centered between the pedicles and the vertebral end plates are visualized, end on. In patients without prior lumbar fusion, the catheter is often inserted at the L1-2 or L2-3 interspace. For this, the incision should be centered over the skin representation of the L3 or L4 pedicle, respectively, on the side of the pump implant, so that the catheter does not cross the midline. There are many methods to surgical preparation. This author’s preferred technique involves initial skin decontamination with isopropyl alcohol, followed by marking of the lumbar incision and remarking of the abdominal incision. The operative field is then outlined with a border of Mastisol solution (Ferndale Labs, Ferndale, MI). Plastic drapes (Number 1010, 3M, St. Paul, MN) are then
VII. SURGICAL PROCEDURES AND TECHNIQUES
Catheter Insertion
placed to isolate the operative field. A typical scrub and paint preparation is then performed with either povidone-iodine or chlorhexidine solutions. Once the paint has dried, the incisions are remarked with a sterile surgical marker, and a layer of Duraprep (3M) or Chloroprep (CareFusion; Becton Dickinson, Franklin Lakes, NJ) is applied. The operative field is outlined in sterile towels, and an iodine-impregnated drape (Ioban 2; 3M) is applied before the final draping. Double gloving is used during the procedure, and outer gloves are changed after draping and before starting the procedure. After a time-out procedure, the incisions are infiltrated with generous amounts of local anesthetic. This author prefers a 1:1 mixture of lidocaine with epinephrine (1:100,000 or 1:200,000) and 0.5% bupivacaine because of its combination of rapid onset (due to the lidocaine) and long duration (due to the bupivacaine).
CATHETER INSERTION The low-complication catheter placement technique described here is intended to minimize catheter breakage by reducing stress on the implanted catheter. These stressors include compression by the spinous processes and acute angles of passage. It also is intended to reduce the incidence of CSF leakage along the catheter track (Follett et al., 2003). Once the lumbar incision is made, electrocautery or sharp dissection is used to expose the lumbodorsal fascia. Some authors (Albright, 2006) advocate lining the incision edges with iodine-soaked cottonoids to reduce the incidence of infection, but this author has not found this to be necessary. The catheter will be anchored to the fascia, so the fascia should be meticulously cleaned of all loose areolar tissue and fat, as they do not provide the stability required and interfere with proper anchoring. Using fluoroscopy, a Touhy-type epidural needle is guided to a midline puncture of the thecal sac beginning from a paramedian fascial entry point over the ipsilateral pedicle. The intended level of thecal sac puncture is at least one level above the pedicular level of insertion. For example, entry into the fascia over the L4 pedicle should lead to a puncture of the thecal sac at no lower than L2-3. Either live or intermittent fluoroscopy may be used during this part of the procedure. The paramedian shallow approach prevents the catheter from being intermittently compressed by the spinous processes during lumbar extension and eventually fracturing. Moreover, it provides a shallow angle of catheter entry into the CSF. This not only facilitates catheter passage but also reduces bending stress on the catheter and reduces catheter kinking and fracture. The bevel is oriented so that the opening faces laterally during the dural puncture. This allows for more of a fiber-splitting approach
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through the ligamentum flavum. Once tactile feedback of sac puncture has been obtained, the stylet is removed and flow of CSF is confirmed. The bevel is then rotated to face cranially for catheter passage. A common problem often encountered by physicians performing IT catheter placement is inadvertent multiple dural punctures because the surgeon cannot “find” the thecal sac. Multiple punctures into the thecal sac can lead to excessive CSF leak and post–dural puncture headache (PDPH) (Grady et al., 1999) and neural trauma, which, in turn, can lead to neuropathic pain, paresis, loss of bowel and bladder control, loss of sexual function, paresis, and even paralysis. In addition to these complications of low-pressure headache or neural trauma, multiple attempts and failures at “finding” the IT space can lead to excessive epidural bleeding, possibly resulting in epidural hematoma (Noli et al., 2001) or installation of bacteria, resulting in epidural infection or meningitis (Pray, 1941). To help facilitate catheter placement, Haddadan and Krames (2007) proposed a technique whereby the midline of the epidural space is identified by using a lossof-resistance technique. The dural sac is then identified in the lateral fluoroscopic position by injecting nonionic radiograph dye into the epidural space and visualizing the dye as it layers on the thecal sac (Fig. 40.1A). The needle is then advanced slowly under fluoroscopic control until the needle first tents the dural and subdural layers and then enters the thecal sac (Fig. 40.1B). Confirmation of placement is made by further injecting dye and visualizing the dye layering on the anterior dural membrane (Fig. 40.1C). The catheter is then passed cephalad until it reaches its intended target within the thecal sac. Under fluoroscopic guidance, the catheter is then threaded through the needle to the desired spinal level. The catheter should pass easily and smoothly without obstruction, resistance, or visualized kinking. Any indication of these issues should prompt retraction of the catheter through the needle. However, any retraction of the catheter should be done slowly to avoid shearing of the catheter at the needle tip. A steeper angle of entry into the thecal sac increases the risk of this complication. If the catheter presents some resistance to retraction, the needle and catheter should be removed together to avoid shearing. The needle is then reinserted, and the catheter is once again advanced within the thecal sac. Of course, removal of the catheter and needle as one will increase the risk of post–dural puncture headache and other sequelae of decreased intracranial pressure. There is no firm rule for the preferred spinal levels for catheter tip placement. Kroin et al. (1993) demonstrated a significant concentration gradient of IT medication that may influence this decision. The catheter tip is typically placed at T7-10 for spastic paraparesis or IT medication administration for axial low back pain. Some
VII. SURGICAL PROCEDURES AND TECHNIQUES
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40. SURGICAL TECHNIQUE: INTRATHECAL MEDICATION DELIVERY SYSTEM IMPLANTATION
FIGURE 40.1 (A) The epidural needle enters the epidural space using a loss of resistance technique and 0.5 L of contrast dye is injected. Dye is seen layering out along the thecal sac. (B) The epidural needle is slowly advanced against the resistance of the dura mater. Dye is now seen tented along the dura mater and along the subdural membrane. (C) The needle is advanced farther until there is a discernible loss of resistance or feeling of a “pop” and dye is again injected. Seen posteriorly is the tenting of the dura and subdural membranes and anteriorly is the layering of dye along the anterior thecal sac. Confirmation of placement is made by observing a free flow of cerebrospinal fluid.
implanters place the catheter tip higher (between C4 and T4) for spastic quadriparesis or cervical pain. For those patients with dystonia, the catheter may be placed as high as C1-4 (Albright, 2006). For the placement of IT analgesic agents, Krames recommends that the catheter tip be placed as close as possible to the cord level that is processing the patient’s pain (Krames, 1993). Once the catheter is at the desired targeted level, the catheter stylet is removed and spontaneous CSF flow from the end of the catheter should be observed. The stylet is partially replaced and a nonabsorbable pursestring suture is placed through the fascia around the needle entry point. The needle and stylet are then removed while using fluoroscopy to ensure constant position of the catheter tip. Be aware that some newer catheter models such as the Ascenda (Medtronic) catheter may not be visible on fluoroscopy after the stylet is removed. There is often a small radiopaque tip but this is sometimes also difficult to see, intraoperatively. CSF flow from the end of the catheter is again verified once this is completed and then again after the purse-string suture is tied down. The catheter is clamped off to prevent undue loss of CSF, and an anchor (provided by the manufacturer) is threaded over the catheter to its fascial entry point. The anchor is secured right at the catheter entry point to provide both stability and strain relief. If a “butterfly” anchor is used, two nonabsorbable sutures are placed, one through fascia and both eyes of the wings and another through the fascia and around the necks of the wings. Some newer anchors self-adhere to the catheter and require suturing only to the fascia. CSF flow is once again verified and the catheter end is again clamped off to prevent further loss of CSF.
If the patient has a history of prior spinal headaches, an epidural injection of autologous blood may be performed at the level of catheter insertion (or one level below) through a separately inserted 18-gauge or smaller spinal needle to help prevent a recurrence of this problem, postoperatively. If this is to be done with the patient under general anesthesia and unable to respond, extra care must be taken not to overinfuse blood so as to cause neurologic symptoms.
PUMP PREPARATION AND INSERTION Once the catheter is inserted to its intended IT target area within the CSF and anchored, an incision is made for pump pocket creation. Electrocautery and/or sharp dissection is used to expose the rectus and external oblique fascia. All of the subcutaneous fat superficial to the pump is kept with the skin. Some obese patients will need to have the subcutaneous fat thinned out to facilitate pump refills and communication with the external programmer. Alternatively, some extremely thin patients may need their pockets created subfascially (Kopell et al., 2001). This reduces the size of the pump bulge and protects it against erosion through the skin. Almost all of the pocket dissection is done inferior to the incision, but the upper flap should be lifted as well to help cover the top of the pump. Ideally, the top of the pump should sit just below the incision, with none of the pump lying directly under the incision. There are often substantial vessels that penetrate the fascia and extend into the fat. These should be thoroughly coagulated, so that they do not result in a pocket hematoma.
VII. SURGICAL PROCEDURES AND TECHNIQUES
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References
Once the pump pocket is created to be just larger than the pump, a one-piece IT catheter is tunneled from the lumbar incision to the abdominal pocket. If a two-piece catheter system is used, the tunneling tool is passed from the lumbar incision to the abdominal pocket, and the proximal pump catheter, which has a connector for the pump on one end, is passed through the tunneler from the pocket to the lumbar incision. Only very rarely is a midflank passing incision required to accomplish this. The one-piece catheters and newer Ascenda catheters made by Medtronic have no preattached connector on the end but instead come with a short extension catheter with the pump connector. For this system, the tunneling tool is passed from the abdominal incision to the lumbar region. The IT catheter of the traditional two-piece system is then trimmed to the appropriate size for the patient. This author prefers to trim enough catheter such that there is only a single gentle bend of catheter remaining in the lumbar incision and the connection between the two catheters is located just lateral to the incision. This places this connection in an easily accessible position should it be necessary to retrieve it during a revision procedure. Some implanters always place a single or double loop within the lumbar incision after creation of a “lumbar catheter pocket.” This single or double loop provides strain relief for the catheter within the thecal sac but may introduce more risk of kinking. The two-piece catheter system requires that the catheters be connected. Some systems have a connecting pin preset into the end of the extension catheter. A strain relief boot is placed on the IT catheter and the catheters are then connected, taking care not to poke the connecting pin through the end of the IT catheter. The boot is slid into place and secured with a nonabsorbable suture tie. The trimmed piece of catheter is saved and measured for use in the dosing of the catheter priming bolus. The pump is prepared on the back table. The sterile water that comes prefilled in the pump is emptied, and the desired preservative-free medication is then loaded into the pump. It is important to ensure that the pump is completely emptied before filling, as any residual sterile water will dilute the drug and result in underdosing. Extraneous catheter is then taken up at the abdominal end to allow only a single gentle bend of catheter (or the desired number of loops) to remain in the lumbar incision. The pump and catheter are then connected. The newer, sutureless connectors simply click onto the pump. The older connectors are snapped onto the pump nozzle and then secured with a single nonabsorbable suture tie. The pump is then placed within the pocket with an extra extension catheter coiled gently beneath it. Some surgeons prefer to trim the extension catheter before connecting it to the pump to eliminate significant coils behind the pump. This is done in the hope of preventing kinking of this extraneous length of catheter. The pump is then secured to the fascia using nonabsorbable suture through
the fascia and through at least two pump loops. It is important to inspect the sutures before tying them down to visually ensure that the pump catheter is not caught and constricted by the sutures. An alternative to this is the use of a Dacron sock (provided by the manufacturer) that encases the pump and firmly scars in over time, thus reducing the likelihood of pump rotation. Patients who are obese may need this Dacron sock encasing the pump because the larger pocket (after thinning of subcutaneous fat) leaves more room for the pump to flip over.
CLOSURE Once hemostasis is achieved, all incisions are thoroughly irrigated with antibiotic-impregnated saline solution. The author prefers to close the incisions with two layers of absorbable sutures beneath the skin, in addition to skin closures. The deeper fat is brought together not in an attempt to add strength to the closure but instead to provide another closed layer of tissue between the hardware and the external environment. This reduces the risk that the pump or catheter will erode through the skin at the incision. The skin may be closed as per the surgeon’s preference. Staples, sutures, or subcuticular closure with skin adhesive are all acceptable. Before closing, it is essential that all bleeding vessels are cauterized to avoid a pump pocket hematoma. After closure, the pump is then programmed for the appropriate priming bolus and starting dose.
POSTOPERATIVE CONSIDERATIONS It is this author’s preference that all patients receive an abdominal binder to wear for the first postoperative week. This is intended to reduce the formation of a seroma within the pump pocket and to help hold the pump in place until it firmly scars in. Patients are kept flat for 2 h postoperatively and longer if they have a history of spinal headaches. This is not absolutely necessary, but this author has found it helpful. Antibiotics are continued for 24 h postoperatively. Radiographs of the entire pump system are obtained in both the anteroposterior and lateral views. This includes all spinal segments containing the catheter as well as the abdomen. These images provide baseline views against which any further investigations may be compared if there is a question of hardware disconnection or migration.
References Albright, A.L., 2006. Intraventricular baclofen infusion for dystonia. Report of two cases. J. Neurosurg. 105, 71–74. Atiyeh, B.S., Hayek, S.N., Skaf, G.S., Al Araj, A., Chamoun, R.B., March 2006. Baclofen pump pocket infection: a case report of successful salvage with muscle flap. Int. Wound J. 3 (1), 23–28.
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40. SURGICAL TECHNIQUE: INTRATHECAL MEDICATION DELIVERY SYSTEM IMPLANTATION
Follett, K.A., et al., 2003. Prevention of intrathecal drug delivery catheter-related complications. Neuromodulation 6, 32–41. Grady, R.E., et al., 1999. Neurologic complications after placement of cerebrospinal fluid drainage catheters and needles in anesthetized patients: implications for regional anesthesia. Mayo Perioperative Outcomes Group. Anesth. Analg. 88, 388–392. Haddadan, K., Krames, E., 2007. Technique that better localizes the dura mater during intrathecal catheterization should reduce inadvertent multiple dural punctures and reduce complications. Neuromodulation 10, 164–166. Kopell, B.H., et al., 2001. Subfascial implantation of intrathecal baclofen pumps in children: technical note. Neurosurgery 49, 753–756, discussion 756–757. Krames, E.S., January 1993. Intrathecal infusional therapies for intractable pain: patient management guidelines. J. Pain Symptom Manag. 8, 36–46.
Kroin, J.S., et al., 1993. The distribution of medication along the spinal canal after chronic intrathecal administration. Neurosurgery 33, 226–230, discussion 230. Mehtar, S., 1998. New strategies for the use of mupirocin for the prevention of serious infection. J. Hosp. Infect. 40 (Suppl. B), S39–S44. Motta, F., et al., 2007. The use of intrathecal baclofen pump implants in children and adolescents: safety and complications in 200 consecutive cases. J. Neurosurg. 107, 32–35. Noli, M., et al., 2001. Diagnosis and therapy of IT bleeding. Minerva Anestesiol. 67, 82–91. Pray, L.G., 1941. Lumbar puncture as a factor in the pathogenesis of meningitis. Am. J. Dis. Child 295, 62–68. Sanderson, P.J., 2001. The role of methicillin-resistant Staphylococcus aureus in orthopaedic implant surgery. J. Chemother. 13 (Spec No 1), 89–95.
VII. SURGICAL PROCEDURES AND TECHNIQUES
40 Surgical Technique: Intrathecal Medication Delivery System Implantation Joshua M. Rosenow Northwestern University Feinberg School of Medicine, Chicago, IL, United States
O U T L I N E Surgical Planning/Preoperative Considerations
537
Closure541
Positioning and Surgical Preparation
538
Postoperative Considerations
Catheter Insertion
539
References541
Pump Preparation and Insertion
540
SURGICAL PLANNING/PREOPERATIVE CONSIDERATIONS Planning for the implantation of an implantable drug delivery system (IDDS) requires considerations for the prevention of hardware infection, ergonomics of system function and comfort of the patient, prevention of pump pocket and catheter complications, and prevention of cerebrospinal fluid (CSF) leak. An IDDS consists of an intrathecal (IT) segment of catheter, a subcutaneous segment of catheter, and an implanted pump. The IT and subcutaneous catheter segments may be either part of the same catheter (one-piece catheter) or separate catheters joined with a connecting pin (two-piece catheter system). The choice of either a one-piece catheter or two-piece catheter system is determined by the preference of the implanter. A one-piece catheter eliminates the need for connecting pins and the related considerations that go with connecting two catheters together including assuring that the two catheters will not pull apart, etc. A one-piece catheter is also longer in total length than the IT segment of the two-piece system and thus can be used to reach higher vertebral levels (upper thoracic or cervical) that may be difficult
Neuromodulation, Second Edition http://dx.doi.org/10.1016/B978-0-12-805353-9.00040-1
541
to reach with a two-piece catheter system. Conversely, a two-piece catheter system may be easier to handle when revising the IT catheter because the IT portion may be disconnected and interrogated in the back, unlike the one-piece system, which must be cut and then connected with a new connecting pin following open interrogation or replacement of part, unless an entirely new one-piece catheter is implanted. There are newer two-piece catheter systems that are longer (like the one-piece systems) and are segmented into a very long section that is implanted into the IT space and then tunneled to the abdomen and a very short section that essentially becomes only the pump connector. Given that the pump footprint is somewhat large, the placement location of the pump is not a small consideration both technically and, to the patient, cosmetically and ergonomically. The most common programmable pump for implantation in the United States is the Synchromed II (Medtronic, Inc., Minneapolis, MN), which comes in two sizes and holds either 20 mL or 40 L of medication. It is my opinion that when using these programmable pumps, patients should be shown models of each pump so that they can grasp the magnitude of the implanted device and can express their opinion as to
537
© 2018 Elsevier Ltd. All rights reserved.
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40. SURGICAL TECHNIQUE: INTRATHECAL MEDICATION DELIVERY SYSTEM IMPLANTATION
which size they prefer, understanding that the smallercapacity pump must be refilled more often. These two pumps have the same footprint, but the actual thickness difference between the two pumps is not great: 19.5 versus 26 mm, respectively. The Prometra II pump (Flowonix Medical, Mt. Olive, NJ) is 69 mm in diameter and 24 mm thick and holds 20 mL. The patient should be queried as to the usual location of the waistband of their pants, as it is desirable to prevent this from rubbing on the pump and contributing to erosion of the hardware through the skin. The pump should be sited on the patient in both the supine and seated positions, to ensure that it will be placed in a position that is comfortable for the patient. The pump should affect neither the lower costal margin nor the iliac crest. For most patients, the pump may be comfortably placed in a paramedian location with the superior aspect near the level of the umbilicus, adjusted as needed for individual anatomy. When possible, the site of implant should be chosen so as to avoid other implanted devices such as ventriculoperitoneal shunts, gastrostomy tubes, and other implantable devices such as an implantable pulse generator for spinal cord stimulation. If a pump is being reimplanted following removal of a prior one due to infection, it is desirable to use the contralateral abdomen if possible. While pump pocket or hardware infections are rarely life threatening, they result in interruptions in therapy, further trips to the operating room, increased healthcare costs, and frustration for all involved. It is rare to salvage an infected pump, although there are reports of this salvage occurring in the literature (Atiyeh et al., 2006). Patients must be free of infection at the time of implantation. This includes urinary and respiratory tract infections, as well as infected decubitus or other skin ulcers. Most pump infections are due to skin contaminants, such as Staphylococcus sp. Preoperative bathing for several days with a solution containing chlorhexidine gluconate may decrease skin colonization with both sensitive and antibiotic resistant organisms (Motta et al., 2007). Intranasal mupirocin ointment, twice daily, may help decrease the rate of intranasal carriage of resistant Staphylococcus sp. (Mehtar, 1998; Sanderson, 2001). Antibiotics such as cefazolin or oxacillin, which cover common skin organisms, are usually sufficient for prophylaxis; however, some physicians recommend that all patients be given vancomycin preoperatively to cover methicillin-resistant Staphylococcus aureus (MRSA) bacteria. It is my opinion that preoperative cross-sectional imaging studies (either magnetic resonance imaging [MRI] or computed tomography [CT]) should be obtained from the planned catheter insertion site to the proposed tip location so that the surgeon may have advance knowledge of any anatomic variants or barriers to catheter insertion or passage. The level of the conus should be noted.
POSITIONING AND SURGICAL PREPARATION The patient is placed on the operating table in the supine position. After the induction of general endotracheal anesthesia, the pump implant site is then marked on the abdomen (if this has not been done before coming to the operating room). It is important to do this before the patient is turned into the lateral decubitus position, as the abdominal skin can shift greatly, especially if the patient has a pendulous abdomen. The patient is turned into the lateral decubitus position with the planned pump implant side up. An axillary roll is placed to relieve traction and pressure on the brachial plexus. Padding is also placed between all bony protuberances to prevent pressure and possible sequelae including pressure sores. Both arms are placed such that they are as far superiorly as is comfortably possible for the patient. This facilitates visualization of the spine and catheter with fluoroscopy. The lower arm is either placed on an arm board and the upper one on an “airplane-type,” arm holder or both arms, separated by padding, are placed in the “praying mantis” position and secured in that position. Each arm is thoroughly padded to prevent pressure on the ulnar nerves. Some surgeons secure the patient in the lateral decubitus position using wide cloth tape, and some secure the patient in that position using a “beanbag.” If a beanbagtype pad is used, it may be wrapped around the patient and suction applied to harden it and support the patient. Care should be taken in doing this so that neither the lumbar nor the abdominal operative site is obscured by the bean bag. The beanbag should not rise as high as the lumbar spinous processes or the umbilicus. Care should also be taken to ensure that sharp points to not cut into the patient. Sturdy fabric tape is applied across the patient’s hips (padded as well) to prevent rotation during the procedure. The fluoroscope is brought in, and anteroposterior images are obtained. The fluoroscope should be aligned to the patient’s spinal anatomy such that the spinous processes are centered between the pedicles and the vertebral end plates are visualized, end on. In patients without prior lumbar fusion, the catheter is often inserted at the L1-2 or L2-3 interspace. For this, the incision should be centered over the skin representation of the L3 or L4 pedicle, respectively, on the side of the pump implant, so that the catheter does not cross the midline. There are many methods to surgical preparation. This author’s preferred technique involves initial skin decontamination with isopropyl alcohol, followed by marking of the lumbar incision and remarking of the abdominal incision. The operative field is then outlined with a border of Mastisol solution (Ferndale Labs, Ferndale, MI). Plastic drapes (Number 1010, 3M, St. Paul, MN) are then
VII. SURGICAL PROCEDURES AND TECHNIQUES
Catheter Insertion
placed to isolate the operative field. A typical scrub and paint preparation is then performed with either povidone-iodine or chlorhexidine solutions. Once the paint has dried, the incisions are remarked with a sterile surgical marker, and a layer of Duraprep (3M) or Chloroprep (CareFusion; Becton Dickinson, Franklin Lakes, NJ) is applied. The operative field is outlined in sterile towels, and an iodine-impregnated drape (Ioban 2; 3M) is applied before the final draping. Double gloving is used during the procedure, and outer gloves are changed after draping and before starting the procedure. After a time-out procedure, the incisions are infiltrated with generous amounts of local anesthetic. This author prefers a 1:1 mixture of lidocaine with epinephrine (1:100,000 or 1:200,000) and 0.5% bupivacaine because of its combination of rapid onset (due to the lidocaine) and long duration (due to the bupivacaine).
CATHETER INSERTION The low-complication catheter placement technique described here is intended to minimize catheter breakage by reducing stress on the implanted catheter. These stressors include compression by the spinous processes and acute angles of passage. It also is intended to reduce the incidence of CSF leakage along the catheter track (Follett et al., 2003). Once the lumbar incision is made, electrocautery or sharp dissection is used to expose the lumbodorsal fascia. Some authors (Albright, 2006) advocate lining the incision edges with iodine-soaked cottonoids to reduce the incidence of infection, but this author has not found this to be necessary. The catheter will be anchored to the fascia, so the fascia should be meticulously cleaned of all loose areolar tissue and fat, as they do not provide the stability required and interfere with proper anchoring. Using fluoroscopy, a Touhy-type epidural needle is guided to a midline puncture of the thecal sac beginning from a paramedian fascial entry point over the ipsilateral pedicle. The intended level of thecal sac puncture is at least one level above the pedicular level of insertion. For example, entry into the fascia over the L4 pedicle should lead to a puncture of the thecal sac at no lower than L2-3. Either live or intermittent fluoroscopy may be used during this part of the procedure. The paramedian shallow approach prevents the catheter from being intermittently compressed by the spinous processes during lumbar extension and eventually fracturing. Moreover, it provides a shallow angle of catheter entry into the CSF. This not only facilitates catheter passage but also reduces bending stress on the catheter and reduces catheter kinking and fracture. The bevel is oriented so that the opening faces laterally during the dural puncture. This allows for more of a fiber-splitting approach
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through the ligamentum flavum. Once tactile feedback of sac puncture has been obtained, the stylet is removed and flow of CSF is confirmed. The bevel is then rotated to face cranially for catheter passage. A common problem often encountered by physicians performing IT catheter placement is inadvertent multiple dural punctures because the surgeon cannot “find” the thecal sac. Multiple punctures into the thecal sac can lead to excessive CSF leak and post–dural puncture headache (PDPH) (Grady et al., 1999) and neural trauma, which, in turn, can lead to neuropathic pain, paresis, loss of bowel and bladder control, loss of sexual function, paresis, and even paralysis. In addition to these complications of low-pressure headache or neural trauma, multiple attempts and failures at “finding” the IT space can lead to excessive epidural bleeding, possibly resulting in epidural hematoma (Noli et al., 2001) or installation of bacteria, resulting in epidural infection or meningitis (Pray, 1941). To help facilitate catheter placement, Haddadan and Krames (2007) proposed a technique whereby the midline of the epidural space is identified by using a lossof-resistance technique. The dural sac is then identified in the lateral fluoroscopic position by injecting nonionic radiograph dye into the epidural space and visualizing the dye as it layers on the thecal sac (Fig. 40.1A). The needle is then advanced slowly under fluoroscopic control until the needle first tents the dural and subdural layers and then enters the thecal sac (Fig. 40.1B). Confirmation of placement is made by further injecting dye and visualizing the dye layering on the anterior dural membrane (Fig. 40.1C). The catheter is then passed cephalad until it reaches its intended target within the thecal sac. Under fluoroscopic guidance, the catheter is then threaded through the needle to the desired spinal level. The catheter should pass easily and smoothly without obstruction, resistance, or visualized kinking. Any indication of these issues should prompt retraction of the catheter through the needle. However, any retraction of the catheter should be done slowly to avoid shearing of the catheter at the needle tip. A steeper angle of entry into the thecal sac increases the risk of this complication. If the catheter presents some resistance to retraction, the needle and catheter should be removed together to avoid shearing. The needle is then reinserted, and the catheter is once again advanced within the thecal sac. Of course, removal of the catheter and needle as one will increase the risk of post–dural puncture headache and other sequelae of decreased intracranial pressure. There is no firm rule for the preferred spinal levels for catheter tip placement. Kroin et al. (1993) demonstrated a significant concentration gradient of IT medication that may influence this decision. The catheter tip is typically placed at T7-10 for spastic paraparesis or IT medication administration for axial low back pain. Some
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FIGURE 40.1 (A) The epidural needle enters the epidural space using a loss of resistance technique and 0.5 L of contrast dye is injected. Dye is seen layering out along the thecal sac. (B) The epidural needle is slowly advanced against the resistance of the dura mater. Dye is now seen tented along the dura mater and along the subdural membrane. (C) The needle is advanced farther until there is a discernible loss of resistance or feeling of a “pop” and dye is again injected. Seen posteriorly is the tenting of the dura and subdural membranes and anteriorly is the layering of dye along the anterior thecal sac. Confirmation of placement is made by observing a free flow of cerebrospinal fluid.
implanters place the catheter tip higher (between C4 and T4) for spastic quadriparesis or cervical pain. For those patients with dystonia, the catheter may be placed as high as C1-4 (Albright, 2006). For the placement of IT analgesic agents, Krames recommends that the catheter tip be placed as close as possible to the cord level that is processing the patient’s pain (Krames, 1993). Once the catheter is at the desired targeted level, the catheter stylet is removed and spontaneous CSF flow from the end of the catheter should be observed. The stylet is partially replaced and a nonabsorbable pursestring suture is placed through the fascia around the needle entry point. The needle and stylet are then removed while using fluoroscopy to ensure constant position of the catheter tip. Be aware that some newer catheter models such as the Ascenda (Medtronic) catheter may not be visible on fluoroscopy after the stylet is removed. There is often a small radiopaque tip but this is sometimes also difficult to see, intraoperatively. CSF flow from the end of the catheter is again verified once this is completed and then again after the purse-string suture is tied down. The catheter is clamped off to prevent undue loss of CSF, and an anchor (provided by the manufacturer) is threaded over the catheter to its fascial entry point. The anchor is secured right at the catheter entry point to provide both stability and strain relief. If a “butterfly” anchor is used, two nonabsorbable sutures are placed, one through fascia and both eyes of the wings and another through the fascia and around the necks of the wings. Some newer anchors self-adhere to the catheter and require suturing only to the fascia. CSF flow is once again verified and the catheter end is again clamped off to prevent further loss of CSF.
If the patient has a history of prior spinal headaches, an epidural injection of autologous blood may be performed at the level of catheter insertion (or one level below) through a separately inserted 18-gauge or smaller spinal needle to help prevent a recurrence of this problem, postoperatively. If this is to be done with the patient under general anesthesia and unable to respond, extra care must be taken not to overinfuse blood so as to cause neurologic symptoms.
PUMP PREPARATION AND INSERTION Once the catheter is inserted to its intended IT target area within the CSF and anchored, an incision is made for pump pocket creation. Electrocautery and/or sharp dissection is used to expose the rectus and external oblique fascia. All of the subcutaneous fat superficial to the pump is kept with the skin. Some obese patients will need to have the subcutaneous fat thinned out to facilitate pump refills and communication with the external programmer. Alternatively, some extremely thin patients may need their pockets created subfascially (Kopell et al., 2001). This reduces the size of the pump bulge and protects it against erosion through the skin. Almost all of the pocket dissection is done inferior to the incision, but the upper flap should be lifted as well to help cover the top of the pump. Ideally, the top of the pump should sit just below the incision, with none of the pump lying directly under the incision. There are often substantial vessels that penetrate the fascia and extend into the fat. These should be thoroughly coagulated, so that they do not result in a pocket hematoma.
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References
Once the pump pocket is created to be just larger than the pump, a one-piece IT catheter is tunneled from the lumbar incision to the abdominal pocket. If a two-piece catheter system is used, the tunneling tool is passed from the lumbar incision to the abdominal pocket, and the proximal pump catheter, which has a connector for the pump on one end, is passed through the tunneler from the pocket to the lumbar incision. Only very rarely is a midflank passing incision required to accomplish this. The one-piece catheters and newer Ascenda catheters made by Medtronic have no preattached connector on the end but instead come with a short extension catheter with the pump connector. For this system, the tunneling tool is passed from the abdominal incision to the lumbar region. The IT catheter of the traditional two-piece system is then trimmed to the appropriate size for the patient. This author prefers to trim enough catheter such that there is only a single gentle bend of catheter remaining in the lumbar incision and the connection between the two catheters is located just lateral to the incision. This places this connection in an easily accessible position should it be necessary to retrieve it during a revision procedure. Some implanters always place a single or double loop within the lumbar incision after creation of a “lumbar catheter pocket.” This single or double loop provides strain relief for the catheter within the thecal sac but may introduce more risk of kinking. The two-piece catheter system requires that the catheters be connected. Some systems have a connecting pin preset into the end of the extension catheter. A strain relief boot is placed on the IT catheter and the catheters are then connected, taking care not to poke the connecting pin through the end of the IT catheter. The boot is slid into place and secured with a nonabsorbable suture tie. The trimmed piece of catheter is saved and measured for use in the dosing of the catheter priming bolus. The pump is prepared on the back table. The sterile water that comes prefilled in the pump is emptied, and the desired preservative-free medication is then loaded into the pump. It is important to ensure that the pump is completely emptied before filling, as any residual sterile water will dilute the drug and result in underdosing. Extraneous catheter is then taken up at the abdominal end to allow only a single gentle bend of catheter (or the desired number of loops) to remain in the lumbar incision. The pump and catheter are then connected. The newer, sutureless connectors simply click onto the pump. The older connectors are snapped onto the pump nozzle and then secured with a single nonabsorbable suture tie. The pump is then placed within the pocket with an extra extension catheter coiled gently beneath it. Some surgeons prefer to trim the extension catheter before connecting it to the pump to eliminate significant coils behind the pump. This is done in the hope of preventing kinking of this extraneous length of catheter. The pump is then secured to the fascia using nonabsorbable suture through
the fascia and through at least two pump loops. It is important to inspect the sutures before tying them down to visually ensure that the pump catheter is not caught and constricted by the sutures. An alternative to this is the use of a Dacron sock (provided by the manufacturer) that encases the pump and firmly scars in over time, thus reducing the likelihood of pump rotation. Patients who are obese may need this Dacron sock encasing the pump because the larger pocket (after thinning of subcutaneous fat) leaves more room for the pump to flip over.
CLOSURE Once hemostasis is achieved, all incisions are thoroughly irrigated with antibiotic-impregnated saline solution. The author prefers to close the incisions with two layers of absorbable sutures beneath the skin, in addition to skin closures. The deeper fat is brought together not in an attempt to add strength to the closure but instead to provide another closed layer of tissue between the hardware and the external environment. This reduces the risk that the pump or catheter will erode through the skin at the incision. The skin may be closed as per the surgeon’s preference. Staples, sutures, or subcuticular closure with skin adhesive are all acceptable. Before closing, it is essential that all bleeding vessels are cauterized to avoid a pump pocket hematoma. After closure, the pump is then programmed for the appropriate priming bolus and starting dose.
POSTOPERATIVE CONSIDERATIONS It is this author’s preference that all patients receive an abdominal binder to wear for the first postoperative week. This is intended to reduce the formation of a seroma within the pump pocket and to help hold the pump in place until it firmly scars in. Patients are kept flat for 2 h postoperatively and longer if they have a history of spinal headaches. This is not absolutely necessary, but this author has found it helpful. Antibiotics are continued for 24 h postoperatively. Radiographs of the entire pump system are obtained in both the anteroposterior and lateral views. This includes all spinal segments containing the catheter as well as the abdomen. These images provide baseline views against which any further investigations may be compared if there is a question of hardware disconnection or migration.
References Albright, A.L., 2006. Intraventricular baclofen infusion for dystonia. Report of two cases. J. Neurosurg. 105, 71–74. Atiyeh, B.S., Hayek, S.N., Skaf, G.S., Al Araj, A., Chamoun, R.B., March 2006. Baclofen pump pocket infection: a case report of successful salvage with muscle flap. Int. Wound J. 3 (1), 23–28.
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Follett, K.A., et al., 2003. Prevention of intrathecal drug delivery catheter-related complications. Neuromodulation 6, 32–41. Grady, R.E., et al., 1999. Neurologic complications after placement of cerebrospinal fluid drainage catheters and needles in anesthetized patients: implications for regional anesthesia. Mayo Perioperative Outcomes Group. Anesth. Analg. 88, 388–392. Haddadan, K., Krames, E., 2007. Technique that better localizes the dura mater during intrathecal catheterization should reduce inadvertent multiple dural punctures and reduce complications. Neuromodulation 10, 164–166. Kopell, B.H., et al., 2001. Subfascial implantation of intrathecal baclofen pumps in children: technical note. Neurosurgery 49, 753–756, discussion 756–757. Krames, E.S., January 1993. Intrathecal infusional therapies for intractable pain: patient management guidelines. J. Pain Symptom Manag. 8, 36–46.
Kroin, J.S., et al., 1993. The distribution of medication along the spinal canal after chronic intrathecal administration. Neurosurgery 33, 226–230, discussion 230. Mehtar, S., 1998. New strategies for the use of mupirocin for the prevention of serious infection. J. Hosp. Infect. 40 (Suppl. B), S39–S44. Motta, F., et al., 2007. The use of intrathecal baclofen pump implants in children and adolescents: safety and complications in 200 consecutive cases. J. Neurosurg. 107, 32–35. Noli, M., et al., 2001. Diagnosis and therapy of IT bleeding. Minerva Anestesiol. 67, 82–91. Pray, L.G., 1941. Lumbar puncture as a factor in the pathogenesis of meningitis. Am. J. Dis. Child 295, 62–68. Sanderson, P.J., 2001. The role of methicillin-resistant Staphylococcus aureus in orthopaedic implant surgery. J. Chemother. 13 (Spec No 1), 89–95.
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