Intrathecal drug delivery involves the placement of a needle and catheter into the thecal sac. This can lead to an injury to the spinal cord, nerve root, or other neuraxial tissue, along with bleeding. Certainly, prior to the consideration of an intrathecal pump placement, the practitioner must consider the complexity of the anatomical spinal space, including spinal stenosis or arachnoiditis, into which the pump is to be implanted because disease pathology, medical characteristics, and variations in spinal anatomy may complicate the procedure.

At the time of placement, it is important to keep the patient as responsive and cogent as possible during needle placement, along with catheter placement, within the intrathecal space. A theoretical risk could include direct injury of the spinal cord; the risk of needle injury is much more likely when the needle entry is above the conus medullaris, which is usually located at L1. Direct needle injury of the spinal cord or the exiting nerves below this level is highly unlikely because the nerves float in the cerebrospinal fluid (CSF) and are usually pushed away by the needle approach, especially if the needle is advanced in the lateral fluoroscopic view and a blunt-tip needle is employed. The catheter can be threaded directly into the conus medullaris or other portions of the spinal cord, causing a new radicular pain, best treated with immediate withdrawal and an attempted repass of the catheter, underscoring the importance of catheter placement in an awake patient, if possible.

Infectious complications are uncommon, but these may include epidural abscess or intrathecal infection/meningitis. Superficial infections may occur at the reservoir site or neuroaxilla near catheter placement and anchoring. Reports of viral-induced transverse myelitis have been reported with pump catheters, but these reports are difficult to differentiate from chemical injury to the tissue. As a precaution perioperative antibiotic use, typically gram-positive coverage, is essential prior to pump placement. Antibiotic irrigation is also used by some practitioners [2]. If an infection is discovered within the neuraxial space (as opposed to a superficial wound infection), it is essential to remove both catheter and pump to prevent ongoing infection or progression and to consult a local infectious disease specialist.

In terms of later postoperative neuraxial complications, it is also possible for neurological sequelae to occur with the formation of granuloma, particularly with long-term use of high-concentration or high-dose opioids. Granuloma is a noninfectious inflammatory mass that appears to be a chronic fibrotic that develops at the tip of the intrathecal catheter with clinical presentations ranging from an asymptomatic problem to a major insult that can cause compressive symptoms. Fortunately, inflammatory masses develop slowly over time and in many cases are detected early based on the development of new clinical signs and symptoms, namely loss of treatment efficacy or new neurological symptoms or signs. The most common clinical presentations are loss of effect, sensory changes, pain in the distribution of the catheter tip, and loss of proprioception. Motor loss usually occurs late in the progression and may increase the urgency of intervention.

The cause of granuloma appears to occur from the long-term use of high-concentration opioids or high daily doses of opioid medications and may represent an example in pharmacokinetic failure based on new insights garnered from CSF hydrodynamics. The most commonly reported opioids are morphine and hydromorphone. In a recent analysis, a consensus panel recommended reducing the drug concentrations when possible to a concentration of morphine not greater than 20 mg/mL and the concentration of hydromorphone not greater than 15 mg/mL, which was increased from the 2007 consensus conference recommendations. In addition to reducing the concentration of opioids, other theories have been developed including using smaller, more lipophilic, molecules such as fentanyl and sufentanil or adding bupivacaine to reduce the dose of opioid required, which has been reflected in the 2012 Polyanalgesic Consensus Conference guidelines (see Chap. 41). Some have theorized a protective effect of clonidine in reducing the formation of granuloma, but this has not been proven prospectively.

There has been one case of granuloma formation with ziconotide reported to the U.S. Food and Drug Administration (FDA) between January 2004 and October 2012 of the 1,753 granuloma formations reported in total, although the case is clouded by prior opioid therapy before ziconotide initiation and granuloma discovery. Thus the relative safety of ziconotide, with regards to granuloma formation, is still quite favorable. In 2010 there is one published case report in the European literature describing a patient who developed two sequential granuloma formations with a ziconotide intrathecal pump within a 10-month period.

The diagnosis of either abscess or granuloma is confirmed by magnetic resonance imaging (MRI), but physical examination and history are very important in making the initial diagnosis. The MRI may be diagnostic with gadolinium depending on the size and location of the mass. Computed tomography (CT) myelogram is an option if the patient has a contraindication to MRI (e.g., cardiac pacemaker, insulin pump, neurostimulator, cochlear implant).

Another complication that can occur is a CSF leak, which may occur in as many as 20 % of patients with intrathecal drug delivery systems [2]. Such leaks may present clinically with symptoms of a post–dural puncture headache (PDPH; e.g., nuchal rigidity, positional headache). Treatment is similar to that of any patient with a PDPH (e.g., caffeine, fluids, conservative management), but interventional epidural blood patch may be pursued with caution to avoid any possibility of intrathecal catheter damage.

Infection of the pump or catheter can lead to explant of the device. The rate of infection varies from practice to practice but is reported from 0 to 4.5 % globally for surgical procedures. Infection is obvious in some cases with redness, purulent drainage, and swelling, but in some cases it may be difficult to differentiate from postoperative skin irritation. The presence of a fever, elevated white blood count with a left shift in neutrophiles, elevated C-reactive protein, and elevated erythrocyte sedimentation rate raises the index of suspicion toward an infectious process. The diagnosis may be confirmed by Gram stain and culture. The diagnosis can be confusing in the immunocompromised patient, such a patient on long-term steroids or a patient with advanced cancer, because the tissue reaction and blood marker elevations may be blunted. In addition to device infection, the clinician should consider other more common sources of fever, such as atelectasis, urinary tract infection, and drug reaction in the acute postoperative, postimplantation period. Vigilance is paramount when managing a suspected infection, and clinical signs and symptoms of an infection are present, it is recommended to manage the patient conservatively and consider explantion of the device.

The noninfectious buildup of serosanguineous fluid, termed seroma, may impede the ability of the wound to heal. This may be very similar to an infection in tissue appearance and may be associated with an elevation of the white blood count. Diagnosis is confirmed by aspiration of straw-colored noninfectious fluid. Seroma formation can be lessened by limited aggressive blunt dissection, the use of sharp dissection, excellent hemostasis, closure of deadspace, and use of compression postoperatively, commonly via an abdominal binder. Treatment may include surgical drainage, simple aspiration, or conservative management.

Although extremely rare, bleeding from the pocket reservoir site or spinal incision can lead to wound dehiscence, pain, and the need for surgical drainage. Diagnosis is made by an expanding wound with pain or by frank bleeding. Small hematoma formation is possible, but an expanding wound may require further intervention. Subdural migration has been reported and can lead to decreased efficacy or in some cases overdose. In addition subdural hematoma is a rare but possible occurrence and presents clinically with severe headache and neurological sequelae requiring urgent surgical intervention. Transverse myelitis has been associated with intrathecal catheters in very rare situations. If a progressive myelopathy develops in the presence of a normal MRI, a neurology consult should be obtained.

The pump can cause pain because of flipping in the tissues, contact with bony landmarks, or erosion of the device through the skin. Erosion is most commonly associated with significant weight loss and a diminished subcutaneous adipose layer. This may develop from an overall decrease in body mass index or by redistribution of fat with aging or diseases. Also, if a pump becomes flipped, this may inhibit the ability to refill the pump with maintenance drug without the use of image guidance and may require acute intervention to prevent medication withdrawal side effects.

Historically, the most common type of hardware complications in intrathecal drug delivery systems are catheter related. Possible problems seen with intrathecal catheters include kinking, fracture, leak, and migration. Migration of the catheter is rare if proper anchoring and purse-string suturing are utilized. The movement of the catheter out of the spinal canal can lead to loss of pain relief or withdrawal from the infused drug.

Catheter kinking, scarring, and leakage can lead to multiple clinical problems. The problem is suspected with the loss of clinical efficacy, because a higher than suspected volume of the pump reservoir at the time of refill is not clinically reliable. The workup includes a side-port catheter evaluation under fluoroscopy, where an aspiration is attempted from the catheter side port. If 2 mL is able to be withdrawn freely from the catheter, then dye is injected to perform a myelogram surrounding the catheter to inspect for filling defects. If the side-port study suggests a noncongruent system within the intrathecal space, surgical exploration and catheter revision are recommended.

Advancements in catheter technology have remedied some of the historical challenges with catheter malfunctions

Intrathecal pump patients require intermittent refills to continue to deliver drugs, as the reservoir is depleted with slow continuous infusion. This process requires access to the Silastic port. The risks of refill include infection, seroma formation, inadvertent catheter access, inadvertent deposit of drugs outside the pump, termed a “pocket fill,” and inability to access the pump. The risk of infection can be significantly reduced by maintaining appropriate sterile technique and using a bactereostatic filter; there may be additional antibacterial effects of local anesthetics themselves when included in the infused agent. Infections appear to be less than 1 in 1,000 when proper technique is used.

Most commonly, the body creates a fibrous pocket around the pump and may stabilize the device. In patients with poor tissue integrity, such as patients with cancer, diabetes, active smokers, and long-term steroid therapy, formation of this pocket may not develop and the device may be prone to flipping and to creating discomfort. These patients may require a Dacron pouch around the pump to establish a localized tissue reaction or placement of “stay sutures” through the suture loops of the device reservoir. Ultimately these patients may require surgical adjustment if the pump is unable to be returned to its proper position.

Rotor failure is a risk of currently approved programmable pumps manufactured by Medtronic (Minneapolis, MN). The problem can be diagnosed by an x-ray after the pump is programmed to give a bolus that will result in a turn of the rotor on films if it is functioning correctly. Motor stalls occur more commonly when off-label medications are employed within the pump, either in combination or as monotherapy. Newly developed devices, such as the Prometra Programmable Infusion Pump system (Flowonix; Mt. Olive, NJ), approved in 2012, employs a valve-gated system that is nonperistaltic and may mitigate the challenges with off-label therapy. Another pump company innovation by Codman (Codman and Shurtleff; Raynham, MA) allows to access the actual volume in the computer without aspirating the pump, as compared with current methods of pump volume as determined by health care provider input. Because this is a relatively newly approved device, complications of these new pump mechanisms are not currently known, and careful observation will be necessary when these products become commercially available.

Typical intrathecal pumps contain a pump side port with a main pump access port entered by noncoring needles that reduce trauma to the materials. These needles are specific to the port of intended refill to reduce the risk of inadvertent refill into the wrong port. Unfortunately, but thankfully very uncommon, the pump can experience failure of the lumen or side port over time that leads to a leakage of drug and a need for a surgical revision.

Patients with drug abuse histories can sometimes be treated successfully with a pump, although pump maintenance and candidacy requires medical compliance. Although intrathecal therapy and use of the patient therapy manager provides the clinician a greater amount of control, all patients with potential risk for drug diversion, secondary gain, or substance abuse should be rigorously screened prior to pump implantation and closely monitored throughout treatment if intrathecal pump implantation is deemed an appropriate therapy.

Long-term opioid infusions can lead to complications (Tables 43.1 and 43.2). A multicenter analysis of complications has shown that these complications can affect several body systems. Intrathecally administered opioids cause multiple side effects including nausea and vomiting (25.2 %), pruritus (13.3 %), edema (11.7 %), diaphoresis (7.2 %), weakness (7.2 %), weight gain (5.4 %), and diminished libido (4.9 %).