Bleeding

During the placement of an intrathecal catheter, the needle typically passes through the epidural space with little trauma. However, in anticoagulated patients and in patients with bleeding dyscrasias, epidural bleeding and resultant epidural hematomas are a significant risk (Table 5-1). Epidural bleeding is likely common but usually goes unnoticed in the absence of postoperative imaging studies. Rarely, an epidural bleed may produce a clinically significant epidural hematoma. Untreated, an epidural hematoma can progress and result in numbness, weakness, increased pain, and ultimately paralysis. If the development of an epidural hematoma is suspected, the patient should undergo immediate magnetic resonance imaging (MRI) and surgical evaluation. Prompt hematoma evacuation should be performed within 12 hours of the onset of symptoms because evacuation within this time frame has been associated with better neurological outcomes. Any patient complaining of weakness in the postoperative period should undergo immediate evaluation for the presence of an epidural hematoma (Box 5-1).

Table 5-1 Commonly Used Drugs That May Result in Increased Risk of Bleeding Complications

Infection

Epidural abscess formation can result in compression of neurologic structures and symptoms similar to those of epidural hematoma formation. Although the risk of epidural abscess formation is probably less than one in 1000, any patient who complains of increasing pain at the catheter insertion site, develops a clinically significant fever over 101°F or greater, or complains of weakness or numbness should undergo urgent MRI with proper precautions and surgical evaluation if warranted. It is important for the physician to be aware that epidural abscess may initially present as pain around the catheter insertion point and may evolve to include severe radiating pain if the infection invades the neural foramen or compresses the spinal cord.

Discitis and meningitis are serious complications that must undergo immediate treatment if suspected. Superficial wound infections are much more common but still require prompt attention to prevent penetration of the deep tissue layers and involvement of the implant. It is recommended that an infectious disease consultation be obtained in any infection that is suspected of penetrating beyond the superficial layers. Prompt neurosurgical consultation is mandatory in any patient suspected of having an epidural abscess.

Risks factors for infection include any patient with a history of immunocompromised state such as HIV infection, history of methicillin-resistant Staphylococcus aureus infection, organ transplantation, cancer, diabetes mellitus, and skin infections at the time of implantation (Box 5-2). Transverse myelitis is uncommon but is seen with catheter infections and may not be present with known infection.² Routine laboratory studies, including C-reactive protein (CRP), complete blood count (CBC) with differential, and erythrocyte sedimentation rate (ESR), should be obtained in patients with clinical symptoms of infection.

Neurologic Injury

Damage to spinal neurologic structures may result from direct needle trauma during intrathecal needle placement. The conus medullaris is located at the L1–L2 level in most adults with the cauda equina floating freely in the cerebrospinal fluid (CSF) below. Thus it is recommended that needle placement occur below the L1–L2 level. Monitored anesthesia care is recommended with the patient freely arousable and communicating with the surgeon during needle placement. However, it is important to realize that catheter placement in the conus medullaris is possible in an awake patient without the patient complaining of pain. In some patients, particularly very ill cancer patients, it is necessary to perform the implantation under general anesthesia. In these patients, needle placement should be performed well below the conus medullaris.

A paramedian approach with a needle entry angle of 30 to 45 degrees should minimize the chance of inadvertent penetration of the spinal cord. Additionally, obtaining later fluoroscopic images during the advancement of the needle into the intrathecal space may minimize the possibility of neurologic trauma because a steep needle angle is more easily recognized in the lateral view.

It is advisable to examine the patient in the postanesthesia recovery unit and document either the absence or the presence of new focal neurologic findings. If neurologic injury is suspected, the physician should obtain an MRI as soon as practical with the appropriate precautions. Additionally, an electromyogram and nerve conduction study may be useful to characterize the extent of neurologic damage but may not show any abnormalities for several days after the insult. Many patients suspected of neurologic injury may have a contusion of neuritis that usually resolves in time with conservative treatment and observation. Finally, administration of intravenous steroids should be considered in the immediate postoperative period in any patient suspected of neurologic injury.

Postpuncture dural headache (PDPH) may result from dural tear during intrathecal needle placement. A persistent CSF leak and hygroma are other complications that can result in significant patient discomfort and eventual neurologic injury if not managed properly. Many physicians advocate placement of purse-string sutures deep within the fascia surrounding the needle and catheter before removal of the catheter. This may compress the tissue around the catheter and prevent persistent dural leak and hygroma formation. Additionally, abdominal binders should be placed in the immediate postoperative period. PDPHs are usually managed successfully with conservative treatments consisting of hydration, caffeine, and intramuscular sumatriptan in refractory cases. A neurologic consultation should be considered in any patient exhibiting evidence of cranial nerve palsy.

Infectious Complications

Infectious complications as they relate to needle placement in the intrathecal space were discussed earlier in this chapter and are essentially the same for intrathecal catheters.

Granuloma Formation

Aside from infection, the development of catheter granulomas is one of the most serious complications associated with intrathecal catheters. First reported in 1999, granulomas (Fig. 5-1) appear to be inflammatory, fibrotic, noninfectious masses that develop at the tip of the catheter.³ The mass formation usually develops over months to years and is more likely to form in patients receiving high concentrations of morphine and hydromorphone.⁴ Consensus recommendations have suggested limiting morphine to 20 mg/cc and hydromorphone to 10 mg/cc (Table 5-2).

Fig. 5-1 Intrathecal granuloma.

Table 5-2 Maximum Drug Concentrations and Doses

Granuloma should be suspected when granulomagenic medications are employed intrathecally, especially outside the maximum concentration or daily dose recommendations, and heralded by a change in analgesia, new sensory or motor deficits, and often times is accompanied by an abnormal catheter evaluation. Although some physicians routinely obtain computed tomography (CT) scans to screen for asymptomatic granulomas, there is insufficient evidence to recommend surveillance CT scans or MRIs. Any patient suspected of a granuloma should undergo a T1-weighted MRI with and without gadolinium.

Mechanical Complications

Catheter fracture may occur throughout the length of the catheter but frequently occurs at points of higher stress, which include the site of anchor, catheter splice junctions such as in two-piece catheters, and on the nipple of the reservoir. Catheter failure has been reported to be 4.5% during the first nine months following implantation.⁵ It is important to obtain control of the distal piece of the fractured catheter that typically occurs at the anchoring site. This can be accomplished by opening the anchor incision first and removing the distal catheter before opening the reservoir pocket. In some cases, catheter fracture may be managed with a splicing kit. If the distal catheter piece is irretrievable, a neurosurgical consultation should be obtained.

Another possible complication may result from migration of the catheter from the intrathecal space (Fig. 5-2). This obviously requires catheter revision and can result in side effects that range from the mundane to the serious. Migration into the epidural space may lead to CSF leak with resultant headache, loss of analgesia, and possibly hygroma formation. It is possible for the catheter to migrate into the neural foramen, which may lead to nerve root irritation and the development of radicular symptoms. Migration into the spinal cord is possible with the development of severe neurologic deficits. Any patient suspected of catheter malfunction should undergo plane radiographic imaging to assess for catheter integrity and MRI imaging with appropriate precautions if migration is suspected. Improper catheter anchoring techniques, such as failure to anchor to the thoracolumbar fascia, increase the likelihood of catheter migration.

Fig. 5-2 Catheter migration out of the intrathecal space.

Placement of intrathecal catheters under deep sedation or general endotracheal anesthesia may result in intraparenchymal needle and catheter placement. For this reason, it is recommended that catheter placement be placed under monitored anesthesia care.

Infection

Infectious complications of the pocket and anchor site incisions related to ITDD devices have been reported to range from 2.5% to 9.0% and represent the most common type of infectious complications that the physician implanter is likely to encounter.⁶ Risk factors for infections of the reservoir pocket and anchor site are the same as discussed previously regarding catheter-related infections. Any patient presenting with pain over the incision site, swelling, rubor, or purulent discharge should be suspected of infection (Figs. 5-3 and 5-4). Aggressive management of superficial infections may prevent penetration into the subfascial layers and compromise of the device.

Fig. 5-3 Wound dehiscence caused by infection.

Fig. 5-4 Infected pocket.

In addition to obtaining wound cultures for antibiotic selection, prudent physicians may choose to perform an incision and drainage procedure with pulsed lavage. It is important to inspect the incision for evidence of compromise of the deep fascial planes. In patients suspected of fascial compromise, explantation of the device should be considered as the safest course of management. Chronic slowly growing infections are possible in patients who appear to initially respond to antibiotic treatment and are often accompanied by recurrent clinical fever. Routine laboratory values, including CRP, CBC with differential, and ESR, should be obtained in any patient suspected of wound infection. Additionally, physicians should consider an infectious disease consultation in patients with infection penetrating the deep fascial layers.

Hematoma

Careful attention to wound hemostasis, including meticulous tissue dissection, suturing of arterial bleeding, and use of coagulation for small vessel bleeding, may prevent the development of wound hematomas. The physician implanter should assess the patient’s risk of bleeding preoperatively. If a wound hematoma develops (Fig. 5-5), the physician should consider prompt evacuation and correction of any bleeding diathesis to prevent wound dehiscence and loss of the implant. Additionally, hematomas may predispose the implant to infection.

Fig. 5-5 Wound hematoma.

Seromas

Some patients my develop redness and swelling of the wound resulting from the buildup of serosanguineous fluid. Seromas are sterile and typically present with lack of fever and normal white blood cell count. Typically, seromas can be managed conservatively and can be prevented by using careful surgical dissection, meticulous wound hemostasis, and placement of an abdominal binder, and in rare cases, a patient with a seroma may develop a fever, which necessitates surgical evaluation of the wound with Gram stain and culture to rule out an infectious process. Fortunately, most cases of seroma formation do not lead to device removal.

Painful Reservoir Site

Pain in the reservoir site usually results from tissue irritation because of improper size or location selection. Placement of the reservoir over or near bony landmarks, especially near the inferior subchondral region, may predispose the patient to pain around the reservoir pocket. Failure to anchor the pump, especially when placed in an oversized pocket, may result in tissue irritation, pain, and the development of a pocket seroma. It is strongly recommended that nonabsorbable anchoring sutures placed in the fascia be used to secure the pump in place. Neuroma formation, although rare, may result in significant pain surrounding the reservoir pocket and may be prevented by careful surgical dissection. The presence of complex regional pain syndrome may also be a risk factor for development of chronic postoperative pain in the pocket. Management of the painful pocket includes local anesthetic or steroid injection, Lidoderm patches or compounding cream, and revision in refractory cases.