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 Management of Pain in the Neurosurgical Patient

It has been 30 years since John Bonica, the great anesthesia-based pain educator, expressed concern that pain was not well controlled because of the failure of physicians to apply available knowledge. That thought may hold more credence in the area of neurosurgery than in any other area of postoperative pain treatment. The shortcomings in this arena can be attributed to the common belief of clinicians that pain is minimal after intracranial procedures. Because of this controversial notion, many patients are undertreated in the immediate postoperative period.
A comprehensive look at the issue of postoperative pain in the patient undergoing intracranial surgery led to some clarification of the issue. Dunbar compared those undergoing intracranial surgery to those with select extracranial procedures. In this 200-patient retrospective study, the intracranial group did have significantly less pain than the comparison group (p<0.05). A subset of intracranial patients did have significantly more pain than others in the group. Those requiring frontal craniotomies did have an increased need for opioids, and elevated heart rates, blood pressure, and intracranial pressure (ICP). Based on this analysis, a general statement cannot be made about all patients undergoing intracranial procedures.
Other factors, including the need to monitor neurologic and cognitive functions closely, contribute to this problem. This monitoring can be affected adversely if the patient is sedated or obtunded. This conflict of treatment goals can lead to withholding pain medication and techniques. It has also led to the use of less potent opioids and banning morphine from some neurosurgical intensive care units. Recent studies have shown that when morphine and other potent opioids are titrated it does not alter the outcomes or postsurgical monitoring.
Another factor complicates postoperative pain treatment in modern times. The use of new rapidly acting intravenous agents has led to rapid wake-up and recovery and unfortunately to the increased importance of postoperative pain assessment. With the rapid breakdown of these agents, the patient has no opioid level present and may experience significant pain on awakening.
It is critical to realize that the treatment of pain in the neurosurgical patient may influence outcomes in a variety of ways. Studies have shown that pain in the postoperative period can adversely influence ICP. Proper pain control may stabilize hemodynamics and blood pressure as well as lower the ICP. In addition to pain issues, the perioperative period in the intracranial patient is complex in a systemic fashion. Recovery from neurosurgical anesthesia is followed by elevations in body oxygen consumption and serum catecholamine concentrations. Systemic hypertension is often present after neurosurgical procedures and has been linked to intracranial hemorrhage. The cerebral consequences of the recovery period can lead to cerebral hyperemia and increased ICP. Prevention or control of pain is one of the major factors in limiting these adverse systemic effects.
Over the past decade, developments in intravenous opioids, new regional techniques, and local anesthetics have greatly enhanced our abilities to treat this patient group. Preemptive analgesia may lead to the improved stability of the patient throughout the surgical experience. To minimize pain and decrease the stress response and hemodynamic changes, the surgeon and the anesthesiologist must work as a team. The importance of the anesthesiologist in decreasing anxiety, creating a treatment plan, and executing the plan is crucial to a successful surgical experience.
The opportunities to have an effect on the pain pathway are numerous. The pain response has a three-part complex. Pain transduction is the initial impulse. Pain transmission is the transfer of pain information via the C and A delta fibers through the spinothalamic tracts to the thalamus and cortex. Pain modulation is the interpretation of the pain signal. The cortex then processes this pathway into an emotional interpretation. The patient's genetic, social, and cultural backgrounds influence this interpretation. By understanding this complex pain neural network, the opportunity to impact the pain response is great. The method chosen to impact the pain network depends on the surgical procedure and patient comorbidities.

I. Preoperative assessment

Preadmission or presurgical considerations

Reducing anxiety. Recent studies have shown that reducing anxiety preoperatively or in the immediate postoperative period enhances the ease of controlling pain. In the preoperative and postoperative patient groups, the need for medication has been reduced. There was a decrease in pain scales and hypertension. It is important for the anesthesiologist to use part of the preoperative interview to discuss the plan for postoperative pain treatment. Studies have shown that a discussion of the patient's previous experiences, expectations, and fears can be as useful as some anxiolytic medications. Patients should have a chance to ask questions and express concerns prior to the scheduled procedure.
Pain treatment history. The prolonged use of oral opioids for chronic pain makes determining the baseline dose of opioids in chronic pain patients somewhat difficult. The tolerance to opioid medication can influence dosing in both the intraoperative anesthetic and postoperative pain course. It is important to realize that the use of chronic medications is for a stable pain condition and it will be necessary to supplement this baseline dose with additional medication. It is helpful to obtain a history of previous experiences with postoperative pain treatment, complications, and adverse reactions. The anesthesiologists should explain in detail the pain treatment plan; patient reassurance should be a high priority.
Understanding the procedure. The physician providing the postoperative pain relief should understand the procedure being performed. An understanding of the patient's postsurgical mental status is helpful when the physician chooses a pain treatment plan. Techniques that require an alert patient, such as patient-controlled analgesia, should be offered only to those who are able to comply with instructions. Regional anesthesia is possible if the procedure involves only limited portions of the spine.
Role of coexisting disease. The patient's nonsurgical disease processes must be considered when tailoring a pain treatment plan. The review of systems is critical in determining what recommendations should be made. The following factors should be considered in a presurgical assessment.
Neurologic system. The site of surgery and the perioperative morbidity should be considered. The patient's baseline cognitive function also determines whether a patient-controlled analgesia (PCA) system can be used. PCA can be used in children as young as 5 years but should be instituted with caution and requires the education of both patients and their parents.
Renal system. A patient with renal disease is prone to complications from drugs with metabolites removed by the kidneys. Meperidine, for example, breaks down to normeperidine, which can cause seizures in these patients. Meperidine should be used in a limited fashion in any postsurgical patient but the risk is high in those with renal impairment.
Infectious disease. Neuroaxial procedures may be contraindicated in the patient with systemic infection or local infection at the site of the proposed procedure. If a patient is bacteremic or has local site infections, regional anesthesia is contraindicated.
Hematologic system. The epidural hematoma is a rare but disastrous complication of regional anesthesia. Factors that may contribute to this adverse outcome include abnormalities of the clotting cascade, a history of bleeding during previous surgery, and the use of low molecular weight heparin and other coagulants during the postoperative period. This condition may be evaluated both historically and by laboratory values.
Cardiovascular system. The physiological response to intracranial surgery includes hypertension, tachycardia, and catecholamine surges. An increase in blood pressure, heart rate and catecholamine results in an increase in cardiac workload and may lead to ischemia in those with perioperative risks. When in doubt, a cardiology consultation may be useful in planning the postoperative pain treatment plan. The other risk of the anesthetic and pain treatment is the issue of patients who are cardiovascularly unstable and require support.
Gastrointestinal system. A history of ileus may be a cause for concern for the surgeon in regard to a local anesthetic infusion and use of narcotics. In these cases, it is important to implement a bowel support regimen as a standard part of the program when using intravenous or oral opioids or epidural infusions.
Summary of the preoperative period. The preoperative period is crucial in the overall success of the neurosurgical pain treatment program. The clinician should develop a mental checklist of assessment points prior to bringing the patient to the operating theater.

II. The importance of pain treatment

The patient undergoing neurosurgical intervention may develop many perioperative changes that can affect the overall outcome without attempts at intervention. The stress response, which is somewhat dependent on the complexity and site of surgery, can affect the immunologic response, coagulation, cardiac function, hormonal response, and other systems crucial to the recovery of the neurosurgical patient. The anesthesiologist has several options to blunt the stress response, but these methods are successful only when the appropriate procedure is matched with the right patient.
In some areas of anesthesia, the technique of postoperative pain control has been shown to have a major impact on outcomes and pain reduction. An example of this impact occurs in thoracic surgery. At the current time, no significant studies exist in the neurologic patient, and the significance of postoperative pain is unclear.

III. The stress response: an overview

Changes in other organ systems. The patient undergoing neurologic surgery is often very sensitive to subtle changes in other organ systems. The pathophysiologic changes associated with the stress response from surgical trauma can greatly affect the outcome from procedures with high risk of morbidity and mortality.
Physiologic effects of the stress response. The stress response includes an initial depressed phase and a subsequent hyperdynamic phase.
The depressed phase. In the initial portion of the response, the body responds by depressing most physiologic functions. This phase is brief in the surgical patient and might be unidentifiable in some patients.
The hyperdynamic phase. The portion of the stress response of most concern to the anesthesiologist and most involved in morbidity and mortality in the neurosurgical patient is the period of recovery after surgery. This lasts for a period of time that is directly proportional to the amount of tissue trauma and the patient's preexisting disease state. A characterization of this response is given below.
Endocrinologic changes. Both catabolic and anabolic responses are seen during this phase of response.
(1) Catabolic changes include increases in several hormones: catecholamines, renin, angiotensin II, aldosterone, glucagon, cortisol, tumor necrosis factor, adrenocorticotropic hormone (ACTH), growth hormone, and interleukin (primarily IL-1 and IL-6). These changes lead to hemodynamic instability in some patients and perhaps to changes in cerebral blood flow (CBF) and ICP.
(2) Anabolic changes include decreases in insulin and testosterone. The changes can lead to imbalances in the hormonal axis and impact wound healing and response to tissue trauma.
Metabolic changes. The overall impact on the patient outcome by the stress response can be understood by considering the metabolic balance during this tumultuous time.
(1) The catabolic and anabolic effects noted here create intense changes in the patient's physiologic stability. These changes include shifts in insulin resistance, muscle breakdown, glucose intolerance, fat breakdown, increased tissue oxidation with the creation of free radicals, sodium and water retention, hyperglycemia, increased acute phase proteins, and fluid shifts and third spacing.
(2) The end effect is a change in fluid balance, protein metabolism, fat metabolism, and carbohydrate metabolism.
Body system responses to the stress response
Mechanisms to block the stress response have focused on beta blockade and blockade of other receptors. While these mechanisms are important, the physician should not forget the importance of impacting the pain pathways. Using both techniques enhances the chance of blocking the unstable response. The uninhibited stress response has been shown to increase cardiac workload; increase vascular tension; adversely affect platelet function; decrease fibrinolysis; decrease renal perfusion; decrease the urinary excretion of water, wastes, and electrolytes; decrease hepatic function; increase oxygen consumption; decrease immunocompetence; and decrease the centrally mediated temperature regulation mechanisms.
Considering these enormous changes in the unbridled stress response, the importance of blunting this response in enhancing outcomes becomes critical. Pain treatment mechanisms utilized in limiting this systemic response are detailed.

IV. Mechanisms of blunting the stress response to surgery

General anesthesia. The use of inhalational anesthetics and total intravenous anesthetic techniques including remifentanil have been responsible for tremendous advances in improving the surgical experience and reducing pain at the time of surgery. Unfortunately, although interrupting pain at the time of surgical insult, most agents have not been shown to substantially block the metabolic and endocrine response to tissue trauma. A few anesthetic agents have shown promise compared to alternatives.
Etomidate. When given by the intravenous route, etomidate may have some ability to blunt the adrenocortical system's response to stress. This effect is seen by a blunting of the rise in cortisol expected with similar tissue trauma. Etomidate is thought to accomplish this by blocking enzymes in the cortisol synthesis pathway. The clinical benefit of this drug has not been proved in prospective randomized trials. Its long recovery time may also limit its use as a neuroanesthetic agent.
Inhalational agents. Sevoflurane and isoflurane are both useful drugs in low concentrations in the patient undergoing intracranial surgery. The ability to use these drugs to limit the stress response is minimal because of the effects of higher concentrations in changing CBF, cerebral blood volume, and ICP.
High-dose opioids. Recent years have shown a dramatic increase in the utilization of high-potency short-acting opioids. Remifentanil, a compound of the 4-anilidopiperidine derivatives, is an ideal drug because of its ultrashort duration of action and metabolic independence of both hepatic and renal functions. The advantages of this drug may be some of the critical issues that lead to poor outcomes in regard to postprocedural pain complaints. The rapid increase in serum levels leads to an initial blunting of the stress response, but as the drug is discontinued, the patient is at risk for hyperalgesia and substantial increases in the stress response. It is critical that longer acting opioids be considered when the intravenous infusions of short-acting opioids are discontinued. Remifentanil, like other intravenous opioids, often leads to a stable hemodynamic course during the surgery.
Propofol. Propofol has been used to try to limit the wake-up time from general anesthesia and to blunt the initial stress and pain responses. Limited studies provide no evidence that this drug changes the immediate stress response even when a slow reduction of dosage lengthens the wake-up phase until the patient slowly recovers to baseline cognitive function.
Regional anesthesia: neuroaxial. Regional anesthetic techniques appear to have the greatest ability to block the stress response. The ability to use regional anesthetics in the neurosurgical patient is minimal and acceptable only in a few surgical techniques. Possible opportunities include spinal instrumentation, spinal repair surgeries, plexus operations, and surgery on peripheral nerves. The ability to use these techniques is also limited in surgery of the neuroaxis because it may delay the ability to do neurologic checks postsurgery. While studies have shown epidural or intrathecal analgesia has improved postoperative nitrogen balance, renal function, glucose metabolism, oxygen consumption, coagulation and fibrinolysis, and hepatic and immunologic function, and decreased cardiac workload, it has very little use in the neurosurgical patient.
Peripheral nerve blockade. Peripheral nerve blocks can blunt the initial response to surgery and may be used as a sole anesthetic. The use of this technique in neurosurgical patients is limited. Common locations for peripheral nerve blockade include the brachial plexus, the cervical plexus, the femoral nerve, and peripheral nerves of the lower extremities. The need to assess nerve function in the immediate postoperative period could limit the technique.
Adrenergic blockade. Clonidine has been used in patients with brain trauma and after extensive neurologic surgery to blunt the stress response. The drug has also been shown to blunt the possibilities of vasogenic edema. The use of spinal or epidural alpha-adrenergic blockade has also been shown to reduce the stress response. It is unclear whether the reduction in adrenergic response with epidural or intrathecal clonidine is a direct effect of the alpha-adrenergic blockade or a response to the clonidine-induced analgesia. The use of systemic beta-adrenergic and alpha-adrenergic agents has been shown to stabilize the hemodynamic response and the cerebral circulation.
Nonsteroidals. The perioperative use of nonsteroidal anti-inflammatory drugs (NSAIDs) may enhance the ability of other techniques such as regional analgesia and anesthesia in blocking the stress response. The enhancement of regional analgesia and anesthesia is thought to be directly related to the NSAIDs' action at peripheral receptors involved in the tissue trauma cascade. Recent data on dangers of cyclo-oxygenase 2 inhibition have led to exercise of caution in using this class of drugs in the perioperative period. These drugs have been linked to hypertension, stroke, myocardial infarction, and blood clotting.
Intravenous opioids. The use of PCA has led to markedly improved patient satisfaction and improved pain scores. Studies have shown that opioid-induced pain control can improve immunologic function in the patient undergoing neurosurgical procedures, which may lead to improved outcomes.
Transcutaneous electrical nerve stimulation (TENS). TENS has been used to treat postoperative pain. Current data do not support its efficacy or any effect on blunting stress response.
Psychological counseling. Biofeedback, music therapy, relaxation training, and simple conversation have been shown to lessen the stress response to surgery and lessen the overall stress response.

V. Intraoperative and postoperative pain treatment interventions

Preemptive analgesia
Preoperative local anesthetic infiltration of the surgical field. The blunting of the response to incision may be crucial to the overall ability to provide a stable postoperative pain treatment course, lessen amount of anesthetic involved, and blunt the initial stage of the surgical stress response. Combining local anesthetics with general anesthetics can result in lower minimum alveolar concentrations when compared with using general anesthetics alone. Recovery is also superior with this method. The combined use of general and local anesthetic may reduce the afferent barrage of surgery, and preemptive analgesia may lead to decreased postoperative pain and blunt the stress response. Local anesthetic should be considered for the wound field even when general anesthesia is the method of choice for the anesthetic.
Anesthetics and systemic opioids. There is no evidence that use of high-dose opioids or inhalational agents results in any change in postoperative pain levels or need for pain medications.
Neuroaxial anesthetic techniques. Recent randomized controlled studies in the Japanese literature show that using epidural anesthesia for spine surgery has a preemptive effect on postoperative pain and leads to less perioperative bleeding. An understanding of these techniques is important to be able to use them properly.
Neuroaxial infusion therapy: epidural. The use of epidural infusion therapy has increased in recent years as a primary method of acute pain control in patients undergoing surgical procedures involving peripheral nerves. The proper use of an epidural infusion requires a working knowledge of dermatomal anatomy, drug pharmacokinetics, drug synergies, and postoperative follow-up requirements.
Epidural location. This is important in the dosage requirement and infusion rate required for proper analgesia. Epidural placement should ideally be within two levels of the nerve root of primary focus of the surgical procedure.
Lipophilia. This is crucial in drug selection for postoperative pain. A lipophilic drug such as fentanyl requires placement of the catheter at a level near the nerve innervation of the surgical site. With morphine, which is much less lipid soluble, the catheter placement is less critical because the drug may cover several interspaces prior to being absorbed. Hydromorphone has intermediate properties.
Drug synergies. For more than a decade, data have demonstrated an antinociceptive synergy between intrathecal morphine and lidocaine during visceral and somatic nociception at dosages that do not impair motor function. The combination of local anesthetics and opioids offers a synergistic effect that leads to better analgesia than either drug infused alone. Local anesthetic infusion therapy has been shown to be the most effective method of blunting the stress response to tissue trauma. The addition of opioids helps eliminate the problem of tachyphylaxis that may develop with local anesthetics alone.
Neuroaxial infusion therapy: subarachnoid. The use of spinal blockade in neurosurgical procedures is somewhat limited. Continuous spinal infusion therapy is generally discouraged because of the risk of cerebrospinal fluid leaks and infection as well as the confusion of the neurologic examination.
Peripheral nerve blockade. Peripheral nerve infusions of local anesthetic can be beneficial in the intraoperative period as well as for postoperative pain control. Common sites for continuous infusion include the brachial plexus and the femoral nerve. A nerve stimulator or ultrasound is helpful in the proper placement of the catheter. In general, a blunt-tipped needle is preferable to a sharp beveled needle to reduce the risk of nerve injury.
PCA. The use of patient-controlled narcotic delivery may be applied to either intravenous opioid delivery or epidural infusion medications such as local anesthetics, opioids, or clonidine. The neurosurgical patient presents a dilemma in the decision-making process. Careful attention must be given equally to the baseline preoperative function in regard to the ability to understand the use of a PCA system and to the expected postoperative cognitive function and the ability to utilize the system. A team approach involving the surgeon, anesthesiologist, and patient is needed when this mode of treatment is considered.
Nurse-administered intermittent analgesia. The classic method of postoperative pain relief in the neurosurgical patient is to have a nurse administer intravenous medications. This involves administration either on the patient's demand or at scheduled times at the request of the surgeon or anesthesiologist. This mode of treatment is most appropriate in the patient with altered preoperative or postoperative cognitive function. The disadvantages of this method include delay in treatment, unnecessary suffering, and excessive sedation. It is also labor intensive.
TENS. There are no current data to support any change in postoperative outcome with the use of TENS for incisional pain. This method is difficult to use in the neurologic surgery population because of the technical difficulties of application.
Psychological counseling. The addition of a psychologist to the postoperative acute pain team is helpful in improving the patient's ability to cope with the emotional stress of pain and disease. Unfortunately, because no good studies on the cost-effectiveness of adding this service exist, reimbursement may be difficult to obtain.
Adjuvant drugs. Anticonvulsants are often used after intracranial surgery to prevent seizures. These drugs may also offer some improvement in neuropathic pain syndromes and reduce the opioid requirements. The classic drugs used for neuropathic pain are tegretol and dilantin; however, the most impressive data are with gabapentin. Baclofen has been used to treat spinal-induced spasticity and has been reported in some patients to improve pain of neuropathic origin. Cyclo-oxygenase 2 inhibitors are no longer recommended in the neurosurgical patient. Classic nonsteroidals may reduce opioid needs and improve outcomes. Intramuscular or intravenous ketorolac is generally the drug of choice; however, it should be avoided if the patient is at high risk of hemorrhage. The addition of antiemetics might also be helpful in controlling nausea that can accompany postoperative analgesics. Ondansetron is an attractive choice because it does not tend to potentiate the neurologic cognitive changes of the opioids and other pain medications. Tramadol is a mu-selective agent that has been shown in a few randomized studies to be less effective in the neurosurgical patient than either codeine or morphine. At higher doses up to 75 mg, tramadol had improved efficacy but was not tolerated because of nausea and vomiting.


VI. Creating a case-specific pain management plan

Intracranial procedures. The patient who has had an intracranial procedure presents one of the most difficult problems in pain management. The use of regional anesthesia is not an option. Oversedating the patient can lead to hypercarbia and hypoxemia. The cognitive function might be impaired because of the surgical area involved. Despite these limitations, controlling pain in this group is crucial because of the increased morbidity and mortality associated with uncontrolled hemodynamic response to pain and surgery. Pain treatment in this patient population must consider multiple factors.
Procedures of the extremities. The patient requiring surgery of the extremities gives the anesthesiologist many options. A discussion should occur regarding the patient's postoperative neurologic function and the need for serial functional checks. If the issue of sensory loss is minimal, the use of regional anesthesia is optimal because of the blunting of both pain and the stress response. Other techniques are also acceptable in this population.
Procedures involving the spine. When neurologic surgery is performed on the structures of the neuroaxis, regional anesthesia may result in improved outcomes with an effect on both postoperative pain and blood loss. These surgeries have no effect on cognitive response and are appropriate for postoperative PCA.

VII. Complications of neuroanesthesia pain management

Mental status changes. Serial neurologic checks are often an essential part of the postoperative course. If pain treatment interferes with this assessment, the overall benefit of the pain treatment may be lost. Establishing a team approach with the surgical team and the nursing team to balance the risks and benefits of pain therapies is crucial.
Elevation of arterial carbon dioxide (CO2). The importance of ICP varies in the neurosurgical population. In patients in whom this is an important factor, it is crucial to have some method of monitoring postsurgical CO2. Despite the benefits of improved hemodynamics in ensuring the stability of the patient with elevated ICP, the risk of excessive sedation and hypercarbis could be a possible problem, and the patient must be watched closely. Arterial CO2 and pH are ways to monitor for a possible problem and may be early indicators of impending problems.
Reduction of arterial O2. Hypoxemia may create multiple problems in the patient with neuronal tissue trauma. Anaerobic metabolism occurs when neurons do not have enough oxygen substrate, which can result in a reduction of adenosine triphosphate and subsequent cell death. The use of supplemental oxygen and oxygen saturation as well as serial arterial blood gas monitoring is essential in patients receiving systemic opioids.
Hypotension. In the patient with possible spinal cord trauma, the use of regional anesthesia can be helpful in controlling the stress response and subsequent systemic changes. The resultant decrease in mean arterial pressure can decrease perfusion to the neurologic tissue and create ischemia. Careful attention to blood pressure is crucial when using local anesthetics postoperatively.
Cerebrospinal fluid leak. The possibility of subarachnoid puncture when placing an epidural catheter must be weighed against the benefit of the catheter. The risks of brain herniation must also be discussed with the surgeon if there is any intracranial disease process.
Nerve injury. When using regional techniques in those with coexisting neurologic disease, a risk of nerve injury exists if the patient has abnormal nociception in the area of the proposed procedure. This risk also exists for the patient under general anesthesia or heavy sedation who may be unable to respond to inadvertent intraneural injection.
Infection
1. In the sedated patient, aspiration precautions should be ordered. This should be accompanied by frequent neurologic checks. If aspiration is a risk, sedating medications should be used with caution.
2. Regional anesthesia should be avoided in the patient with local infection at the site of the proposed regional procedure or in the patient with untreated or uncontrolled systemic infection.
3. The site of indwelling regional catheters should be checked regularly for infection. If the catheter is tunneled through a gel coat catheter, the risk of infection is more likely to be skin related.

VIII. Anesthesia methods for neuroaxial pain procedures

A social emphasis on the importance of treating patients with chronic pain has led to the increase in the number of practitioners performing procedures requiring anesthesia. Neurosurgeons, anesthesiologists, physiatrists, orthopedic surgeons, and neurologists now perform these procedures. Regardless of the practitioner involved, the anesthetic issues are important to achieve a stable course.
Spinal cord stimulation. This procedure is most commonly performed for pain involving the extremities. Recent expansion of indications includes pelvic pain, occipital neuralgia, angina, and pancreatitis. The procedure is often separated into stages.
The percutaneous trial. In either the operating room or radiology suite, a temporary stimulation system may be placed under the guidance of a fluoroscope. Anesthesia is difficult because many of these patients have taken oral opioids for long periods and are tolerant to this class of drugs. These patients may require sedation to place the lead in either the lumbar or cervical region but should remain alert and responsive to avoid nerve root injury. The patients also need to be cognitively functional for the computer screening, which involves connecting the epidural lead to the handheld computer and electrically stimulating the nerve tissue to obtain a paresthesia. This requirement for varying levels of sedation makes propofol and remifentanil attractive choices in this group of patients. Regional anesthesia should be avoided. In patients who are stoic, the procedure may be performed under local anesthesia; however, the patient selection for this technique should be very stringent.
The surgical lead. A surgical lead must be placed in some patients with more anatomically difficult spines or in whom a percutaneous lead has failed. This procedure usually requires a wake-up period so the patient can discuss the perception of stimulation. This may lead to a more difficult task because the procedure itself requires a hemilaminectomy. Some surgeons request a general anesthetic with evoked potential testing for this procedure. NSAIDs should be avoided in this population because of the increased risk of bleeding.
The permanent lead. In most cases, the permanent implant involves the placement of both the lead and generator. The permanent implant requires the use of a complex anesthetic because the patient needs to be conversing during the lead placement and more sedated for tunneling and pocket placement. In some cases, the lead placed for the trial procedure is used as a permanent lead. If that is the case, the patient is brought back to the operating room 1 to 4 weeks later for the connection to a permanent generator. This procedure is most often performed under monitored anesthesia care or general anesthesia. This stage requires no period of discussion. Thus, the anesthetic is much less complex. In either method, the placement of the generator pocket determines the patient's positioning. If the generator is placed in a different body area, repositioning and draping may be required, affecting the anesthetic level required.
  Intrathecal and epidural drug infusion systems. The use of neuroaxial infusions to treat pain that is unresponsive to oral or transdermal medications is becoming more common. Catheters may be tunneled and connected to an external infusion source or may be connected to an implantable system that is placed in the subcutaneous tissue.
Totally implantable infusion systems. Placing an intrathecal or epidural pump in the subcutaneous tissue involves two steps. First, a catheter must be placed in the epidural or intrathecal space. Once this has been successfully completed, the catheter can be connected to an infusion source. Anesthesia for these procedures might consist of sedation with local infiltration, subarachnoid or epidural block at the time of catheter placement, or general anesthesia. Each method has its risks and benefits. With general anesthesia, the patient is less likely to move, and the risk of nerve injury may be diminished. In the nonresponsive patient, the risk of nerve injury may be increased, however, if the patient cannot respond to development of parasthesia. The spinal or epidural technique avoids the general anesthetic, which may be advantageous for someone at high risk for pulmonary or cardiac complications. Use of sedation with local anesthetic infiltration reduces the risk of undiagnosed nerve injury at the time of catheter insertion. In some patients, the stimulation involved in the tunneling and pocketing component of the procedure might not be successfully blunted with sedation and local infiltration alone, and a conversion to general anesthesia might be required during the course of the procedure.

Externalized infusion systems. In patients in whom the need for infusion is short term or in those with a life expectancy of <3 months, an externalized system is often selected. The need for general anesthesia in this population is rare because of the lack of pocket creation. Although this procedure could be completed under neuroaxial blockade or general anesthesia, the more common scenario is to use monitored anesthesia care with local infiltration.

Radiofrequency nerve ablation. The cost-effectiveness of radiofrequency ablation has led to a vast increase in the number of procedures performed annually in the United States and Europe. Pulsed radiofrequency ablation is a new technique that has shown promise in treating peripheral nerve processes without larger procedures. This technique is also being utilized more commonly in ablating the sympathetic nervous system and selected peripheral nerves. The anesthetic in these cases is inherently difficult. The patient must be sufficiently sedated to permit the placement of a large radiofrequency cannula and then allowed to awaken rapidly to be able to answer important stimulation questions involving sensory, motor, and nociceptive input. The risks of nerve injury greatly increase in the patient who is not able to fully discern the computer stimulation pattern. Because of these issues, the infusion or injection of fast-acting and rapidly-waning drugs is often utilized. Options include propofol, midazolam, fentanyl, or local anesthetic as a sole agent.
Spinal endoscopy. In 1997, the United States Food and Drug Administration (FDA) approved the use of spinal endoscopy. In this method, the physician uses a fiberoptic scope to visualize and treat disease processes of the spine by an epidural route. This procedure is stimulating and requires sedation to be tolerated in most cases. The use of general anesthesia should be avoided because of the risks of nerve damage in the patient who is unable to report paresthesia.
Minimally invasive disc procedures. The use of new percutaneous techniques to treat contained disc herniations and leaks of the annulus are valuable options in patients who would like to avoid more invasive techniques such as fusion or artificial disc replacement. In these cases, there is a need to converse with the patient at all times. Anesthesia should be with local anesthesia with or without mild sedation.

IX. Summary

The neurosurgical patient is a tremendous challenge to the team providing pain relief. The balance of controlling pain and maintaining safety for the patient in the postoperative period is a difficult task. It is critical that the anesthesiologist, surgeon, and nursing staff work together to obtain a good result. As new drugs and techniques become available, it will be important to update our knowledge of the best methods to perform this complex task.


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