Pain Management

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Intraoperative neuromonitoring has become the standard of care in spine, neuro and orthopedic surgical procedures, because it adds a layer of protection to the procedure. With patient safety as the main concern, it also seem logical to utilize IONM in pain management procedure.

With IONM, specific nerve or nerve roots can be identified/verified prior to

proceeding with ablation and ESI. It also aid as a tool to verify the integrity of the spinal cord, while providing real-time feedback on the state of the nerve during kyphoplasty and cord stimulator placement.

Epidural steroid injections (ESIs) are an acceptable treatment method for discogenic and radicular pain emanating from the cervical, thoracic, and lumbar spine (2, 3, 9, 11, 12, 16, 17, 18,19). ESIs are also utilized in the treatment of spondylosis, nonspecific radiculitis, and spinal stenosis. Other uses reported in the literature and in clinical settings include the treatment of pain from post laminectomy syndrome, post herpetic or post traumatic (including intercostal) neuralgia, muscle contraction headaches, or from a subacute inflammatory spine pain syndrome unresponsive to more conservative treatment (3, 5). Epidurals have also been used to treat pain from malignant syndromes, from viral brachial plexitis or from reflex sympathetic dystrophy. Support for lumbar epidural steroid injections comes mainly from uncontrolled case studies or trials in which 33% to 77% of injected patients reported pain reduction. The success of the injections, as with all therapeutic interventions, depends on patient selection and technique. Unfortunately, even the controlled studies available on epidural steroids are limited methodologically by mixed or nonspecific diagnoses, by lack of functional outcome data, by insufficient patient numbers in control or treatment groups, and by failure to confirm delivery to the epidural space through use of fluoroscopy (4, 8).

Risks associated with needle placement or with the injection of diagnostic/therapeutic substances, including the local anesthetic and steroid suspension, include, infection, bleeding,nerve injury, transient

numbness or weakness, paralysis contrast reaction (allergy), adrenal suppression, and fluid retention with systemic manifestations which may include peripheral swelling. Pneumothorax may occur if undergoing a thoracic procedure. Total spinal blockade is possible with cervical procedures. There is also a potential for minor subcutaneous infection, vasovagal episode, as well as failure to obtain a definitive diagnosis or positive therapeutic injection with persistence of chronic pain. Dural puncture with subsequent spinal (positional) headache has been reported to occur as high as 5% of the time in translaminar injections. However it is

accepted that medical procedures, by their very nature, contain a certain risk to benefit ratio that needs to be taken into consideration when deciding upon a responsible treatment modality, and/or prior to initiating interventional therapies. Procedures that are used primarily as a means of temporary chronic pain control are certainly no exception and currently there are no official safety or procedural guidelines enjoying widespread acceptance in existence, for physicians who routinely perform epidural injection procedures. Such guidelines could potentially be utilized to help reduce or alleviate many of the potential inherent procedural risks. Absolute contraindications to performing epidural injections include known hypersensitivity to agents, local or systemic

infection, local malignancy, bleeding diathesis, congestive heart failure, and uncontrolled diabetes mellitus. Insulin dependent diabetics can

obtain substantial elevations in their blood sugars following epidural steroid injections.

To evaluate the failure rate, patient acceptance, effective volumes of local anesthetic solution, and incidence of neurologic complications after peripheral nerve block performed using the multiple injection technique with a nerve stimulator, we prospectively studied 3996 patients undergoing combined sciatic-femoral nerve block (n = 2175), axillary blocks (n = 1650), and interscalene blocks (n = 171). The success rate and mean injected volumes of local anesthetic were: 93% with 22.6 +/-4.5 mL in the axillary, 94% with 24.5 +/-5.4 mL in the interscalene, and 93% with 28.1 +/-4.4 mL in the sciatic-femoral nerve blocks. Patients receiving combined sciatic-femoral nerve block showed more discomfort during block placement and worse acceptance of the anesthetic procedure than patients receiving brachial plexus anesthesia. During the first month after surgery, 69 patients (1.7%) developed neurologic dysfunction on the operated limb. Complete recovery required 4-12 wkin all patients but one, who required 25 wk. The only variable showing significant association with the development of postoperative neurologic dysfunction was the tourniquet inflation pressure (<400 mm Hg compared with >400 mm Hg, odds ratio 2.9, 95% confidence intervals 1.6-5.4; P < 0.001). We conclude that using the multiple injections technique with a nerve stimulator results in a success rate of >90% with a volume of <30 mL of local anesthetic solution and an incidence of transient neurologic complication of <2%.

Implications: Based on a prospective evaluation of 3996 consecutive peripheral nerve blocks, the multiple injection technique with nerve stimulator allows for up to 94% successful nerve block with <30 mL of local anesthetic solution. Although the data collection regarding neurologic dysfunction was limited, the withdrawal and redirection of the stimulating needle was not associated with an increased incidence of neurologic complications. Sedation/analgesia should be advocated during block placement to improve patient acceptance.

“Seeking paresthesiae when performing a peripheral nerve block may increase the risk of post- anesthetic neurological sequelae. To test this hypothesis, we prospectively followed two groups of patients who underwent hand surgery with an axillary block. In one group, the axillary plexus was located by actively seeking paresthesiae; in the other, pulsations of the axillary artery indicated an adequate position of the injection needle. Mepivacaine 10 mg/ml, with or without adrenaline, was used. The study included 533 patients, 290 in the paresthesia group and 243 in the artery group. Although unintentional, paresthesiae were elicited in 40% of patients in the artery group. Postanesthetic nerve lesions were seen in ten patients, eight in the paresthesia group and two in the artery group, all of whom had been blocked by mepivacaine with adrenaline. Symptoms varied between light paresthesiae lasting a few weeks, and severe paresthesiae, ache and paresis lasting more than 1 year. The etiology suspected was needle and perhaps injection trauma to the nerves during blocking. We conclude that whenever possible nerve blocks should be performed without searching for paresthesiae.”