Complications

Generally, complications following fluoroscopically guided injections are minor and resolve without morbidity.35,36 Obviously, the complication rate associated with spinal injections is higher in inexperienced hands. Minor complications and failures occurred early in the author's experience and were seen in fewer than 1% of patients.37 Burn and Langdon reported a 5.8% incidence of complications (none of which were serious) in their first year of experience.14 The use of imaging and

Figure 9.9. Radiographs demonstrate opacification of the right L4 nerve root with minimal epidural reflux: (A) oblique and (B) AP views. The unopacified nerve root is surrounded by contrast.

L4nerve Root BlockIodine Contrast Side EffectsEpidural Injections The Vertebrae

Figure 9.10. Radiographs following injection of 1 mL of nonionic contrast showing (A) oblique and (B) AP views. The left C7 nerve sheath is opacified without demonstrable epidural reflux. Following filming, 1.0 mL of a therapeutic mixture consisting of two parts lido-caine 2% to one part steroid suspension is injected.

Allergic Reaction Contrast

epidurography prior to injection of therapeutic substances significantly minimizes the risks of procedures.

Allergic reaction to contrast material is a known risk when iodinated contrast is used. Complications or side effects specific to epidural steroid injections include headache, which is most likely following thecal puncture. When a dural puncture occurs, it is easy to recognize after contrast administration, and neither steroid nor local anesthetic should be administered at that level. Instead, the needle is removed, and the epidural space is accessed at another level. The possibility of intrathe-cal injection is the reason for using a nonionic contrast medium that has been approved for myelography. If dural puncture occurs, the patient is given postmyelogram instructions (oral hydration and 12- to 24-hour bed rest). By diagnosing a thecal puncture and avoiding intrathecal steroid administration, significant side effects may be avoided.33

There have been reports of arachnoiditis following intrathecal injection of therapeutic materials.38 It is unlikely that a single subarachnoid injection of a water-soluble steroid preparation will result in permanent sequelae. In fact, intrathecal injections of steroids were once used to treat certain conditions such as multiple sclerosis. Nonetheless, the precautions described earlier for avoiding intrathecal steroid injections are important, since arachnoiditis may be a devastating clinical condition. More acutely, injection of local anesthetic into the thecal sac may result in profound hypotension and transient anesthesia. Transient anesthesia in the lumbar area will wear off in 1 to 3 hours and is usually only inconvenient. In the cervical region, this effect may result in respiratory arrest, necessitating intubation and respiratory support. This is generally avoided by not using anesthetics in cervical epidural injections.

Infection (epidural empyema/abscess or meningitis) is a potential and serious complication that may occur from contamination following skin puncture. Only a small inoculate can cause a significant infection. Such contamination is especially dangerous in the cervical spine. Meningitis may result, with the potential for rapid dissemination within the central nervous system. Obviously, the same meticulous attention to sterile technique that is used for myelography must be exercised for epidural injections.

High volumes of injectate into the epidural space may result in vitreal hemorrhage.39,40 Therefore, the total volume of injected materials (including contrast) should be limited to 10 to 13 mL. Transient paralysis also has been described following lumbar epidural injection, but this is extremely rare.41 This was postulated to be caused by either inadvertent thecal penetration or loculation of the injected fluid (causing transient nerve compression).41 Another reported side effect is water retention, which is generally short-lived.12 Some trials reported no side effects in the patients studied.17,42,43

Failure to use fluoroscopy may result in nerve injury and exacerbation of pain symptoms.44,45 A published report describing a complication in two patients highlights the importance of performing injections while the patient is awake and carefully monitoring the procedure flu-oroscopically.46 The patients in this report were sedated intravenously prior to fluoroscopically guided cervical epidural injection procedures.

A heavily sedated patient will not display the expected pain response or experience paresthesias resulting from misguided needle placement into the spinal cord. The subsequent injection into the cord produced intrinsic spinal cord injury with permanent symptoms. Fluoroscopy and constant awareness of needle tip position, performing epidurog-raphy before steroid injection, and interaction with an awake patient will significantly decrease the chance of such misadventure. Of course, the use of fluoroscopy alone will not ensure against cord injury or the-cal sac puncture.

Additional complications may result in anterior radicular arteries due to injection or injury of major feeding anterior radicular arteries to the spinal cord. This is likely the cause of profound complications, such as spinal cord infarction.47 Failure to aspirate blood is not a sensitive means of excluding intravascular needle placement.48

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