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.