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10 Articles in Volume 10, Issue #2
Introduction to a Referred Sympathetic Pain Map
Deconstructing Complex Regional Pain Syndrome
Feedback and Response Regarding ACOEM’s Practice
Psychologists as Primary Care Providers
FDA’s Risk Evaluation and Mitigation Strategies Program
Avoiding Complications From Interventional Spine Techniques
Laser Therapy in the Management of Fibromyalgia
Expanding Ellipsoidal Decompression (EED®) of the Spine
Neurotechnology, Evidence, and Ethics
Sphenopalatine Ganglion Neuralgia Diagnosis and Treatment

Avoiding Complications From Interventional Spine Techniques

This first of two articles helps practitioners identify and avoid complications associated with spinal interventions and offers suggestions for resuscitation should a severe complication occur.

Residency training in the field of interventional pain medicine does not currently exist. While there are fellowship programs, they differ significantly in their approaches to teaching spinal interventions. Thus, there is no universally accepted means of gaining competency in the specialty, nor is there is an agreed upon standard of knowledge that interventional pain physicians must possess. While board exams do exist, none are ACGME-accredited and there is no requirement to sit for them.

Physicians enter the field of interventional pain medicine with divergent knowledge gained from their primary specialties. However, knowledge and training in interventional techniques are acquired by varied means.1 Some learn from experienced, well-qualified practitioners during a fellowship year. Others learn by observing or taking a weekend course. Still others enter the field with little more training than having read a textbook. When performing procedures, there is usually no trained observer in the procedure suite. This means that the operator is free to do whatever he or she thinks best. Given this, and the fact that there is as yet no standardized body of knowledge required for the field, it falls to the physicians themselves to possess the knowledge and abilities necessary to provide the standard of care expected of a well-trained physician. Individual physicians must police themselves as to their competency and qualifications for safe practice. Unfortunately, it appears that often this is not the case. Over the last several years, the number of interventional procedures performed has risen dramatically, as has the number of malpractice claims.2,3 A consistent theme in these cases is that prescribed protocols have not been followed or correct techniques have not been used.4

Interventional pain specialists, recognizing these difficulties, have begun taking steps to address them. Professional societies such as ISIS and ASIPP have written guidelines and protocols that provide recommendations for proper procedure performance and avoiding possible complications. Additionally, the ISIS guidelines were recently supplemented by an excellent review of complications from spinal procedures published by Bogduk et al.4 The article reviews correct surgical technique and recommends ways to avoid complications. The aim of this article is to further supplement the literature available in the field and to provide information on how to identify and avoid common risks associated with spinal injections.

Medical History for the Spinal Interventionalist

The first and most often overlooked means of avoiding complications is a directed history. The first encounter with the patient provides important information that aids in this task. There has been much written about methods for taking the history of a patient with pain. However, only a small amount of this literature has a focus specific to interventional pain. What are the historical elements that should be taken into account when planning an interventional procedure? The information needed comes from a diverse body of literature compiled from multiple specialties including surgery, anesthesia, PM&R, neurology and radiology.

Medical Conditions and Allergies

A patient history should include identification of bleeding disorders, immune suppression, medication allergies/anaphylaxis and cardiopulmonary status, pregnancy status, neurological and musculo-skeletal status, and history of difficult airway problems.5-8 Each of these conditions can set the patient up for a very serious, if not fatal, outcome. By recognizing and properly managing problematic conditions prior to the procedure, patients can safely undergo most procedures without incident.

Patients with coronary artery disease should have sympathetic stimulation minimized.5 Procedures such as lumbar sympathetic block, celiac plexus block and others can lower blood pressure and cause a compensatory tachycardia. Patients with a history of valvular heart disease, particularly aortic stenosis, should avoid injections that cause a sympathectomy, as any reduction in afterload can cause critical aortic stenosis and death.5 Examples of such procedures include bilateral sympathetic blocks or interlaminar injections with local anesthetics. Patients with a cardiac pacemaker should have it turned off during a radiofrequency procedure or spinal cord stimulator trial to prevent interference with the transmitter signals. Patients with pulmonary disease are at risk of increased morbidity/mortality from pneumothorax during such procedures as thoracic medial branch blocks, sympathetic procedures in the thoracic spine, and even thoracic transforaminal procedures.9 These procedures should not be done bilaterally due to potential for bilateral pneumothorax and respiratory failure. Patients with uncontrolled or poorly controlled hypertension should be referred to their primary care physician prior to undergoing a procedure.5 These patients are at risk for excessive lowering of blood pressure when undergoing procedures that routinely cause a mild blood pressure decline. They are also at risk for stroke should the procedure cause excessive stimulation due to pain. Patients with liver or renal disease may incompletely metabolize sedatives, which should be administered in lowered doses. Altered hepatic function can result in clotting factor abnormalities. Coagulation studies must be done prior to a procedure.5 In addition, infectious hepatitis may present a risk to the operator and should be known prior to the procedure. Patients with pulmonary disease are at risk for hypercapnia if sedation is administered.5-8,10 Patients with rheumatologic disease on oral steroids have an increased risk of infection. Neuro-muscular disease may increase risk of fall and hip fracture. A patient with an allergy to iodinated products may be at risk of reaction to contrast dye. A history of allergy to iodinated foods such as seafood is a contra-indication for administration of contrast dye.7

Past Medical History

Family, social, and past medical history can all be important in discovering conditions that make the outcome of a interventional procedure less than favorable. Questions pertaining to the use of alcohol, tobacco and illicit drug use should be taken into consideration.5 For example, patients with a history of an ongoing addiction may be less likely to have a positive outcome from an interventional procedure as they are rewarded for the continued complaint of pain by prescription of opiate analgesics. History of lawsuit in the workers’ compensation system may lessen the likelihood of a positive outcome although this has been debated back and forth in the literature.12,13 Certainly, it has been shown that work-related litigation for chronic pain has been associated with higher levels of disability due to pain.12 Finally, patients who have a significant psychological component to their pain should have this evaluated and treated prior to undergoing an interventional pain procedure.8

Medication History

Medication history is important as it can significantly impact patient outcome. The question of which medications should be continued or stopped prior to the procedure must be considered. In general, almost all medications can be continued up to the time of the procedure;5 only a few medications require special consideration. For example, many patients with diabetes may be administered glucophage. Although considered generally safe in patients with normal renal function, patients with significantly impaired renal function have a risk of developing lactic acidosis when undergoing procedures requiring large amounts of contrast dye. In such patients, glucophage should be temporarily discontinued on the day of the procedure. Diuretics should be stopped prior to the procedure to prevent electrolyte abnormalities.5 Management of insulin and oral hypoglycemics are controversial and operators are recommended to review published guidelines in anesthesia texts.5 Pain medications should always be continued up to the time of the procedure in order to prevent withdrawal.

Physical Examination

The physical exam is often helpful in confirming suspicions that arise during the patient history. Pay particularly close attention to the airway if sedation is considered. Patients with short fat necks or small jaws can be extremely difficult to intubate or even ventilate. These patients should be administered minimal to no sedation. A careful examination for cardiac and pulmonary disorders should be performed looking for evidence of wheezing rales, congestion, murmurs, and irregular heart rate. It is also important for the pain specialist to document preexisting neurological disorders and even to perform an EMG in some cases. Nerve injury was the most common complication from interventional procedures noted by the anesthesia closed claims project.3 Attorneys are aware of this and scrutinize cases where patients claim to have nerve damage caused by a procedure. A pre-procedure EMG not only guides therapy but can also be used as a baseline should such a claim be made. One should also carefully document musculoskeletal status prior to the procedure.

Imaging Studies

Imaging studies can be useful, particularly in evaluating abnormalities associated with the intervertebral disc. In particular, the physician should be aware of disc bulge, protrusion/extrusion, or degeneration. It should be noted that multiple studies have failed to show a correlation between abnormalities seen on clinical exam or imaging studies and response to diagnostic injections.1,14 For example, one can have severe facet hypertrophy and yet have no pain coming from the facet joint. On the other hand, one may have a normal X-ray and severe pain associated with the facet joint. This is due to the fact that facet joint pain is thought to be caused by a tearing of the joint capsule allowing slight subluxation and microscopic movement of the joint surfaces. This results in inflammation and pain. This is a dynamic process that is not capable of being imaged by current technology.

Complications and Side Effects of Medications Commonly Used By Spinal Interventionalists

Medications commonly used during interventional procedures are of particular concern for a spinal interventionalist. Patients are particularly at risk from medications such as steroids, local anesthetics, antibiotics and contrast dyes that are frequently administered during an interventional pain procedure. Practitioners should have an in-depth knowledge of each of these medications and the complications and side effects associated with them.

Local Anesthetics

Anesthetics are classified as either amino esters or amino amides. Amides are extremely stable compounds and primarily metabolized in the liver via cytochrome P450 enzymes. Thus, clearance of amino amide anesthetics is largely dependent on hepatic blood flow and function. Esters are hydrolyzed at the amino ester linkage in plasma through pseudocholinesterases and are quite unstable in solution. The breakdown of all amino ester anesthetics leads to the formation of p-aminobenzoic acid (PABA) which has been associated with allergic reactions. A variety of adverse events have been associated with the use of local anesthetics including neurologic and cardiac toxicity and allergic reactions. In general, adverse reactions from local anesthetics are rare.15

“The first and most often overlooked means of avoiding complications is a directed history. The first encounter with the patient provides important information that aids in this task.”

Allergic reactions can cause both local and systemic toxicities. They are mediated by both type I and IV reactions. Anaphylaxis is a type I, or antibody-mediated response. Type IV reactions are systemic, of slow onset and are secondary to release of histamine from lymphocytes. Allergic reactions, as opposed to systemic toxicities, are not dose dependent.16 While there have been reports of true allergic reactions to the ester group of local anesthetics, allergy to the amide class is extremely rare. More commonly, the reported “allergy” is due to epinephrine added to the preparation to prolong the anesthetic effect.

Local anesthetics can cause CNS toxicity by way of injection into an epidural vein, direct overdose, or intrathecal injection. When injected intravenously, initialy CNS stimulation occurs and is manifested by restlessness, tinnitus, anxiety, lightheadedness, tremor and possibly seizure.17,18 This excitatory response is thought to be secondary to blocking of inhibitory neurons in the cerebral cortex. Central stimulation precedes depression. This can be manifested as sleepiness, difficulty focusing, loss of consciousness, and respiratory depression or arrest.19 The maximum adult dose for lidocaine is 300-500mg, while for bupivicaine it is 175mg.20 This dose should be heeded when injecting a large volume of local anesthetic during a single procedure. Death is usually secondary to respiratory or cardiac failure. Treatment of CNS toxicity is primarily supportive. During seizures, an airway may need to be established to prevent aspiration and provide a means of ventilation. Administration of anticonvulsants is also indicated if the seizure persists.

A further complication of local anesthetics is intrathecal (IT) injection. If, during the performance of a spinal procedure IT injection is inadvertently performed, the symptoms that develop will depend on the spinal segments involved. The most commonly seen symptoms include hypotension with reflex tachycardia secondary to sympathetic block. Fluid bolus is usually all that is required for treatment. If a segmental block occurs in the upper thoracic area, the sympathetic fibers to the heart may be blocked resulting in hypotension and bradycardia. This may require more aggressive treatment with the addition of atropine and ephedrine. A high spinal block (involving the cervical segments) requires hemodynamic support with fluid boluses as well as ephedrine. Mechanical ventilation may also be necessary until adequate spontaneous ventilation returns.

Cardiac toxicity (CV) can occur with overdose of local anesthetics and has been more frequently reported with the use of bupivicaine. The risk of cardiac toxicity is extremely low. Recent studies show the incidence of CV collapse to be 1 in 40,000 during high epidural blocks21 and 0 in 25,000 brachial, caudal, and lumbar epidural blocks.22 However, local anesthetics at high concentrations can result in cardiac failure. The primary site of action is the myocardium where they cause a dose-dependent decrease in contractile force.23 The weakened contraction is thought to be due to calcium channel blockade. High concentrations can also cause arteriolar dilation. Cardiac toxicity usually occurs after CNS affects are produced. Bupivacaine inhibits cardiac contractility more than lidocaine. This is thought to be secondary to its higher potency as a calcium channel blocker.23

Cardiovascular collapse with bupivicaine occurs at 3.7 times the dose needed to cause seizures, while lidocaine requires 7.1 times the dose.24-27 CV toxicity from large intravascular doses of bupivicaine can be partially reversed by repeated large doses of epinephrine.28 Multiple anti-arrhythmic medications have also been advocated to stabilize cardiac excitability. In general, standard Advanced Cardiovascular Life Support (ACLS) protocols should be followed and one should expect the conduction block caused by bupivicaine to dissociate slowly.

When injected intrathecally, local anesthetics have the potential of causing neurotoxicity at high concentrations. For example, there have been reports of permanent neurologic damage with high concentrations of tetracaine injected intrathecally.29 Symptoms may be transient and characterized by pain or dysesthesia in the buttocks or lower extremities.30 Other mechanisms of neurotoxicity may result from ischemia associated with vasoconstrictors.

Steroids

In general, side effects from steroids during spinal injections are uncommon. Bogduk et al31 reviewed the literature on neurotoxic effects of epidural steroids. He concluded that there was no evidence of any deleterious effects of steroid preparations provided they were injected accurately into the epidural space, but that none of the commercially available formulations were free of potential neurotoxicity if injected deliberately or inadvertently into the intrathecal space. There have been reports of systemic effects from glucocorticoids (the steroids commonly used during spinal procedures) including facial flushing, insomnia, headache, nausea, rash, fluid retention, anxiety, psychosis, heart failure, hypertension, hyperglycemia, glycosuria, gastritis and adrenal suppression.20 The majority of occurrences are mild and transient when due to intermittently administered steroids, as with most spinal procedures. However, for patients at risk (those with heart failure, uncontrolled hypertension, diabetes, etc.), the dose should be reduced, if used at all. The most serious events directly related to steroid preparations are reports of meningitis caused by improperly compounded steroids.

Embolic phenomena caused by steroids have recently been of concern. There are several case reports of catastrophic events following transforaminal epidural steroid injections.32-39 The theorized cause of these events is particulate steroid injected into an end artery that serves to support perfusion of the anterior spinal or vertebral arteries.32 A brief understanding of the anatomy is helpful to clarify the mechanism of injury. A branch of each vertebral artery anastomoses to form the anterior spinal artery. This artery supports perfusion to the anterior part of the spinal cord. The blood supply to the anterior spinal artery is tenuous and requires support from medullary arteries that occur sporadically every few spinal segments from the cervical to sacral spine (see Figure 1).

Figure 1. Depiction of medullary artery showing connection to anterior spinal artery.

The largest of these arteries is called the artery of Adamkiewicz (see Figures 2 and 3). If either the vertebral artery or a medullary artery is “clogged,” the blood supply to the brain or spinal cord is compromised. Studies of large and medium particle steroids have shown clumping resulting in blocked perfusion to distal tissues.40 Reported injuries involved damage to the brain and spinal cord resulting in paraplegia or cerebrovascular accident (CVA). Brouwer et al34 reported C3 quadriplegia secondary to spinal cord infarct after a C6-7 transforaminal ESI with triamcinolone and bupivicaine. Rozin et al35 reported death as a result of brainstem infarct after a C7 TESI with methylprednisolone and bupivicaine. Houten and Errico32 reported on three cases of paraplegia after lumbar transforaminal injection. One case resulted in L1 paraplegia secondary to spinal cord edema after injection of betamethasone and bupivicaine using a transforaminal approach at the L3 and L4 levels. They also describe a case of T10 paraplegia after an S1 thoracic epidural steroid injection (TESI) with methylprednisolone and a case of low thoracic paraplegia secondary to spinal cord edema after L3-4 TESI using methylprednisolone.

Figure 2. Artery of Adamkewitz. Note that the flow goes to, but not beyond, the midline (AP view). Figure 3. Compare with contrast pattern seen with an epidural vein in which flow goes across midline.

The fact that corticosteroids differ significantly in microscopic size has become an important consideration. It has been shown that large particle sizes are most consistently associated with these types of complications.41-43 Methylprednisolone particles are the largest in size of the commonly used preparations. Triamcinolone and betamethasone particles are intermediate in size and have been shown to form extensive aggregations. There are no reports in the literature of embolic events occurring with dexamethasone. This is due to the fact that dexamethasone particles are small (5-10 times smaller than red blood cells) and the particles have not been shown to aggregate, thus implying they are less likely to block arterial flow.40

In a study by Dreyfuss et al, there was no difference in effectiveness of pain relief when a particulate steroid (triamcinalone) was compared to dexamethasone.44 Therefore, it seems reasonable to substitute dexamethasone for particulate steroids when performing procedures that put nervous tissue at risk.

Contrast Dyes

The use of contrast dyes in fluoroscopically-guided spinal procedures is imperative to assure proper placement of injectate as well as to recognize intravascular uptake. The dye functions as a harbinger of untoward effects from subsequently injected medications since it has been shown that intravascular injection can occur despite negative aspiration of blood.45

Pain management physicians will only rarely encounter severe contrast reactions. However, one must be prepared should the situation arise. The physician and staff must be able to recognize a potentially serious adverse reaction quickly since rapid response is critical. Procedure suites should be equipped with resuscitation equipment as a standard precaution. Contrast reaction scenarios should be routinely rehearsed in order to be adequately prepared should an event occur.

Contrast media include iodinated and gadolinium-based contrast products. Iodinated agents are classified as either ionic or nonionic and high, iso, or low osmolar compounds. With the use of ionic contrast material, adverse reactions have been reported in 4-12% of patients vs. 1-3% of patients receiving non-ionic contrast material.46 The largest study compared nonionic to ionic contrast agents injected intrathecally and found significantly fewer adverse reactions with the nonionic compound.47

Adverse reactions to contrast media can be broadly divided by mechanism into chemotoxic reactions and anaphylactoid reactions.48 Chemotoxic reactions primarily include cardiac and renal toxicity; these reactions are dose-related and concentration dependent. In the low volume administration used for most image-guided pain management interventions, chemotoxic reactions are highly unlikely. Anaphylactoid reactions are dose independent and unpredictable. As a direct antigen-antibody reaction cannot be identified with contrast media, these reactions are termed anaphylactoid rather than anaphylactic. This is an immediate sensitivity-type reaction with the release of histamine and mediators from mast cells and basophils.46 Contrast media can activate—directly or indirectly—the complement, coagulation, fibrinolytic, and kinin cascades.48

The great majority of adverse events are mild or moderate. The American College of Radiology quotes rates of serious contrast reaction as 1-2 per 1,000 administrations with high osmolar agents, and 1-2 per 10,000 with low osmolar agents.49 Severe reactions in the high osmolality group are largely anaphylactoid, while severe reactions in patients receiving low osmolality contrast media are now often chemotoxic—in part due to high volume, rapid infusions used for CT angiography. Contrast agents currently used in spinal procedures are nonionic and either iso, or low osmolar and have a low incidence of serious adverse reactions estimated at about 0.04%.50 Anaphylactoid reactions are the only realistic concern in pain management procedures.

Reactions from contrast media are often unpredictable but certain risk factors can be recognized. Prior anaphylactoid reaction to contrast media is associated with an increased likelihood of subsequent reaction. Allergic diathesis increases risk of anaphylactoid reaction. Patients with a history of allergies have a 6.9% chance of reacting to non-ionic contrast dye compared to a low 2.8% reaction rate in patients with no allergic diathesis.51 The prevalence appears to be independent of the type of allergy previously present.49 Patients with asthma and, to a lesser extent, cardiovascular disease are more likely to have a severe reaction.52 Anxiety disorders anecdotally have been associated with an increased risk of developing a contrast reactions.53

Gadolinium chelates are the contrast agent of choice for MRI examinations. They are less radiodense than iodine-based compounds, but can still be utilized in pain management procedures to exclude intravascular or intrathecal injection. Gadolinium has a much lower incidence of acute adverse reaction than iodine-based contrast agents. Adverse reactions from gadolinium have a frequency of 0.004% to 0.7% and anaphylactoid reactions are exceedingly rare, ranging from 0.001% to 0.01% in frequency.49

Iodine-based contrast agents can cause delayed or late reactions occurring from one hour to one week post-procedure. They usually occur within the first three days after a procedure and have an estimated frequency of 2%.54 Most often, these are skin reactions such as maculopapular rash (50%), angioedema, urticaria, and erythema.54 These reactions are usually self-limiting and do not require active treatment. Corticosteroids and antihistamines may be used in moderate to severe cases exhibiting urticaria and pruritis.

Anti-Coagulants

The most significant complication from a spinal intervention in a patient on anti-coagulants is epidural hematoma. Although rare, the consequences are devastating. The incidence is estimated to be between 1:40,000–1:150,000.55-58 The biggest risk factor for development of the complication is a traumatic procedure. In patients who underwent a traumatic procedure, the risk for hematoma was found to be 11.2 times higher in patients without anticoagulation and 35.4 times higher in those who were anticoagulated.59

In patients who developed hematoma without a traumatic procedure, the peri-operative management of anti-coagulants appeared to be appropriate. For example, Xu60 reported a case of epidural hematoma after an interlaminar lumbar epidural steroid injection. The patient was a 78-year-old female on Coumadin® and aspirin for atrial fibrillation. Both were discontinued six days prior to the procedure and Lovenox® substituted as bridging therapy. Lovenox was stopped 30 hours prior to the procedure. An INR on the day of the procedure was normal. The procedure was atraumatic and Coumadin was resumed eight hours post-injection. Lovenox therapy was reinstated 30 hours post-injection. The following day she developed progressive neurological deficits and an MRI revealed a large hematoma extending from L2 to L5.

In another unfortunate case,61 a similar event occurred in an 85-year-old female on Coumadin for atrial fibrillation and heart valve replacement. Coumadin was discontinued six days prior to the procedure and bridging therapy with Lovenox was stopped 24 hours prior to the injection. A lumbar epidural was performed without difficultly and Coumadin was restarted the evening of the procedure; lovenox was restarted at a therapeutic dose 12 hours post-procedure. Two days later she developed severe back pain and lower extremity weakness. MRI revealed a hematoma extending from L2-L4.

Operative Management to Prevent Complications

There are three phases to an interventional procedure: pre-operative, peri-operative, and post-operative. Each requires special consideration.

Pre-Operative Management

Prior to performance of any spinal intervention, careful pre-operative screening is done in an attempt to discover and prevent complications before they occur. Ideally, the prospective patient should answer negatively to all of the following screening questions:

  1. Are you allergic to iodine, betadine, or latex?
  2. Are you allergic to contrast dye?
  3. Do you have a bleeding disorder?
  4. Do you have joint replacements, heart valve replacements, or a pacemaker?
  5. Are you on anti-inflammatories?
  6. Are you on blood thinners?
  7. Do you have any current local or systemic infections?
  8. Are you pregnant?

If the patient answers affirmatively to any of the above questions, the injectionist must carefully consider options before proceeding.

In patients with an allergy to iodine or betadine, further questioning is required to reveal the nature of the incident. If it is confirmed that the patient has a true hypersensitivity reaction to iodine, then non-iodine based products can be substituted including hibiclens (chlorhexidine gluconate) and/or isopropyl alcohol.62 If an iodinated product is inadvertently used, the consequences are usually not serious. However, in one case report, Iododerma (a rare skin eruption usually induced by systemic use of iodide-containing radiographic contrast medium or treatment with oral potassium iodide therapy) occurred in a 42-year-old man who developed multiple pinpoint pustules in the lower extremities after topical application of iodine.63 In another case, a patient developed severe anaphylactic shock from iodinated povidone administered rectally.64

If the patient reports an allergy to latex, further questioning should be done to determine if a true hypersensitivity reaction exists. If so, then non-latex gloves should be used. The mechanism of the allergy appears to be latex particles that become airborne and are inhaled. In one study, the author compared the number and size or airborne particles released from powdered and non-powdered gloves. The results revealed a large amount of particles were detected from the use of powdered surgical latex gloves, none from the non-powdered.65

There are several options to manage a patient with a history of contrast dye allergy. First, the physician must assess the type of reaction. As noted above, true anaphylactoid reactions to low osmolar contrast dyes are rare. Pre-treatment to avoid such reactions during pain procedures is unusual. Instead one can substitute a gadolinium-based contrast agent. Pretreatment is only recommended when there is a history of anaphylactoid reaction to both iodine and gadolinium-based contrast agents. There are several options to minimize adverse reactions with pretreatment regimens. Use of methylprednisolone, 32mg orally, twelve and two hours before contrast administration66 was effective in reducing mild to moderate reactions, but only minimally improved the reaction rate in those with previous severe reactions. For more severe reactions, a suggested regimen of 50mg of prednisone administered orally thirteen, seven, and one hour before contrast administration, combined with 50mg diphenhydramine and 25mg ephedrine.67

The patient who answers in the affirmative when asked about bleeding disorders requires thoughtful consideration. First, one must weigh the risks and benefits of attempting to provide pain relief through an interventional procedure of any type. Patients taken off anticoagulants may be at risk for serious consequences including thromboembolic stroke. If stroke or other serious conditions that might result from discontinuation of anticoagulation, the patient must be placed on a heparin-containing product and followed by the prescribing physician through the peri-operative period. However, even proper anticoagulation management is not without complications. A prospective, multi-center study of 224 patients at risk for arterial embolism was conducted to assess the safety and efficacy of substituting low molecular weight heparin for warfarin prior to surgery. They found that, of the 224 patients enrolled in the study, eight had an episode of thromboembolism within the first three months after surgery despite substituting heparin for warfarin. They concluded that the optimal approach to management of patients on anticoagulants prior to surgery was uncertain. If, despite these cautions, one decides that a procedure is warranted, the patient must discontinue Coumadin at least five days prior to the procedure. An international normalized ratio (INR) checked on the day of the procedure should be below 1.3.68

“If the patient reports a history of joint replacement, prosthetic valve, previous endocarditis, congenital heart disease, surgical shunts or conduits, valvular heart disease, hypertrophic cardiomyopathy, or mitral valve prolapse with regurgitation, they will require prophylaxis with antibiotics.”

If the patient answers affirmatively to having a bleeding diathesis such as hemophilia, idiopathic thrombocytopenic purpura (ITP), or clotting factor disorders, the procedure should be delayed until medical records from the treating doctor have been reviewed. The decision to proceed must be agreed upon by both the patient and the treating physician.

The American Society of Regional Anesthesia has written guidelines for management of patients on blood thinners in the peri-operative period.69-71 NSAIDs are usually stopped 5-7 days prior to neuraxial blocks despite the fact that ASRA concluded that there is no significantly increased risk for hemorrhagic complications in patients on a regimen of NSAIDs who undergo neuraxial anesthesia.69,72,73 Coumadin must be stopped five days prior to procedure performance and the physician should ensure INR are within acceptable levels. Prophylactic heparin should be held for 12 hours and therapeutic heparin should be held for at least 24 hours.74 In general, ticlopidine should be held for 14 days, and clopidogrel should be held for 7 days prior to a neuraxial block.69,75-77 Vitamin E and herbal medications like garlic, ginseng, ginger, and ginkgo may increase the patient’s risk of bleeding. It is reasonable to consider stopping these for 2 to 3 weeks, especially in the presence of other associated patient or procedure-related risk factors. However, according to ASRA guidelines, herbal drugs by themselves appear to represent no added significant risk for the development of spinal hematoma in patients having epidural or spinal anesthesia. Cyclooxygenase-2 inhibitors were found to have minimal effect on platelet function and can be used in patients who require anti-inflammatory therapy in the presence of anticoagulation.

If the patient reports a history of joint replacement, prosthetic valve, previous endocarditis, congenital heart disease, surgical shunts or conduits, valvular heart disease, hypertrophic cardiomyopathy, or mitral valve prolapse with regurgitation, they will require prophylaxis with antibiotics. Standard prophylaxis is amoxicillin 2 g PO 1 hour prior to the procedure. For the penicillin-allergic patient, clindamycin 600mg PO, cephalexin or cefadroxil 2 gm PO, or clarithromycin or azithromycin 500mg PO should be given one hour before the procedure.78

In most cases, pregnant patients should wait until after they have delivered to have an interventional procedure. If the procedure is deemed necessary by both the patient and her attending obstetrician, she should be carefully apprised of the risks associated with the procedure and agree that the benefits outweigh the potential risks.

Patients with a history of current local or systemic infection must be postponed until the patient’s infection has cleared and they are afebrile.

In patients with a history of hepatitis C or HIV, universal precautions must be employed throughout the procedure to protect personnel performing the procedure.

In addition to the pre-procedure questions, patient should have vitals taken on the day of the procedure. Any abnormality is a potential reason for cancellation. In particular, blood pressure and oxygen saturation should be within normal limits. If necessary, the patient should be medically stabilized prior to the procedure.

Peri-Operative Management

Upon entering the procedure suite, the patient should once again be asked the pre-procedure screening questions, as their answers often change when asked a second time. They should then be questioned as to their understanding of the procedure to be performed, the expected consequences of the procedure, and the side of the body the procedure is to be performed on.

“Fluoroscopy with the use of nonionic contrast dye should be employed during all spinal procedures to decrease the chance of inadvertent vascular injection and to confirm needle placement at the intended target area.”

Operating room personnel should announce and confirm the patient’s name, diagnosis, procedure to be performed, and the side or location of the body. They should mark the location on the body with a marker, specifying right or left side. The clinic note requesting the procedure should be checked for medical necessity and correct diagnosis corresponding to the planned procedure. Informed consent should be signed.

Once the decision to move forward with the procedure is reached, the patient should be positioned properly on the OR table. This requires that areas of the body where nerves are vulnerable to compression or stretching be protected, especially if sedating medication is to be used. The ulnar nerve at the elbow, the brachial plexus, and common fibular nerve at the fibular head are particularly vulnerable to compression injuries. These types of considerations are more usual in patients undergoing a general anesthetic and patients should not usually be sedated to this extent.62

If sedation is to be given, nothing by mouth (NPO) guidelines established by the American Society of Anesthesiologists (ASA) should be followed to prevent aspiration of gastric contents. Sedated patients should be monitored by a separate individual whose primary purpose is care of the sedated patient. The most important monitor is a conscious patient. Patients should not be sedated to a level at which communication is not possible. The patient is instructed to report any discomfort or unusual sensations he or she experiences. This is especially important in patients with comorbid diseases. Typical monitoring includes mental status, blood pressure, pulse oximetry, respiratory rate and heart rate.

Patient positioning may include a bolster placed under the patient allowing the belly to hang in a pendulous manner. Windsor et al found that this position helped to evacuate Batson’s plexus decreasing the risk of epidural bleeding when spinal injection procedures were performed.62

Aseptic technique should be employed to prep the surgical site with povidone iodine or chlorhexidine. A triple scrub is required in the case of discography or any type of implant. The scrub should last at least five minutes and should be allowed to dry.62

The operator performing the intervention should usually draw up medications at the time of the procedure. The medication should be read off to the physician as it is drawn into the syringe and correctly labeled to avoid medication errors. If an assistant draws up medications, they should be clearly labeled. Failure to do so may result in a life-threatening event as was the case when a patient experienced a polymyoclonal seizure when traneximic acid was accidently injected instead of bupivicaine during spinal anesthesia. The ampules of bupivacaine (5mg/mL, Merck, Darmstadt, Germany) and tranexamic acid (500mg/5mL) and were similar in appearance. The patient was treated with phenytoin, sodium thiopental infusion, sodium valproate, and supportive care of the hemodynamic and respiratory systems and made a full recovery.79

The author had a near miss experience when attempting to draw up dexamethasone for an epidural injection. A brown bottle with a red and white label that looked like a typical dexamethasone vial was presented to the operator. However, when both the assistant and the physician read the medication label, it turned out to be epinephrine. Thus the error was discovered and corrected. The vial of epinephrine was moved to a different location in the surgery suite.

Only sterile equipment should be employed during the procedure. The operator should change into fresh gloves before doing the procedure and the procedure area should remain sterile. The needle tip should never be touched or handled by the gloved hand.1

The attention of OR personnel and the physician should be focused on the patient during the procedure. Communication should be clearly understood between OR personnel and the physician and discrepancies resolved.

Fluoroscopy with the use of nonionic contrast dye should be employed during all spinal procedures to decrease the chance of inadvertent vascular injection and to confirm needle placement at the intended target area. As mentioned above, there have been several reported cases of injury (most often in the cervical area but also in the thoracic, lumbar and even sacral spine) due to inadvertent vascular injection of arteries supplying the spinal cord, posterior brain and brainstem resulting in quadriplegia, coma, stroke and death. Verrills and colleagues make a case for the use of digital subtraction fluoroscopy (DSF), when available, for all cervical transforaminal injections (CTFI). They present a case report in which a cervical medullary artery was cannulated despite correct positioning of the needle and negative aspiration. The intra-arterial injection was only seen by DSF. He concludes that intra-arterial injection can still occur despite correct technique.80 Kim et al studied intravascular flow patterns injecting 3 mL of a mixture containing nonionic contrast and normal saline continuously at the rate of 0.3–0.5 mL/s with real-time fluoroscopic visualization. The study revealed that even after ideal needle position was confirmed by biplanar fluoroscopy, intravascular injection occurred in 30.8% percent of the cases and was more likely to occur in the cervical region than the lumbar area.81 A study by Furman showed that positive aspiration of blood was 97.9% specific but only 44.7% sensitive.45,80 This has led some experts to advocate abandoning CTFI altogether in favor of an interlaminar technique. However, the interlaminar technique has associated risks of epidural hematoma, injection into Batson’s plexus, and spinal cord trauma. In addition, when the two techniques were compared in a clinical study, there was no significant difference in minor or serious complications.82

Management of Intra-Operative Complications

The most common risk incurred when performing a procedure is vaso vagal syncope.83 The symptom is more common during a cervical than lumbar procedure (8% vs. 1%).84 Signs and symptoms include sweating, cold or clammy skin, bradycardia, hypotension, nausea and vomiting, disorientation, pallor and loss of consciousness.83,84 Conservative treatment includes turning the patient supine, elevating the legs above the heart, placing a cold washcloth on the head, administration of oxygen and IV fluid bolus. These simple measures will usually resolve the symptoms. If heart rate drops and remains below 45-50 beats per minute, one should consider administration of 0.4-1.0mg of Atropine IV. Use of a vasopressor such as ephedrine should also be considered in patients with hypotension not responding to atropine.

Complications associated with interlaminar epidural injections seem to occur more often, and are more severe, in the cervical spine. Spinal cord damage has occurred in heavily-sedated patients.84,85 This may be due to the morphology of the ligamentum flavum in the cervical and upper thoracic spinal levels. An anatomic study by Lirk et al showed that gaps in the ligamentum flavum are common at these levels such that one cannot rely on a perceptible loss of resistance to identity the epidural space.86 In addition to spinal cord injury, epidural hematoma, abscess, neuropathic symptoms, and death have all been reported after interlaminar cervical epidural steroid injection.85,87

Less frequently reported complications can result from aberrant needle placement. These include intravascular, intrathecal, subdural, intrapleural, intraneural and intraosseous injection.20 Direct neural trauma can occur during a procedure but is rare. This can cause both nerve root and spinal cord injury. Symptoms include an increase in pain, profound weakness or numbness, and loss of use of the injured extremity. Usually the symptoms are transient and no treatment is required. If symptoms do not resolve after several weeks, consider an EMG and referral to neurology for further evaluation.

Needles misplaced into the pleural cavity have been known to cause pneumothorax. The risk is highest after trigger point injections in the upper back or chest but it may also occur with any procedure performed in the area of the neck or thorax.3,83 These include stellate ganglion block, thoracic epidural steroid injection from both the inter-laminar and transforaminal approach, medial branch or facet block, and celiac plexus block. This can manifest immediately as shortness of breath, tachypnea and pleuritic-type chest pain. However, in some patients the symptom may take up to 12 hours to manifest. Usually patients with mild symptoms and pneumothorax of less than 25% of lung volume can be treated conservatively and followed with serial chest x-rays.83 Patients at risk of this complication should be informed of expected symptoms and told to go to an emergency room should they occur. In addition, they should be given an order for a chest x-ray and an explanation to the attending physician of the procedure performed, location and side of the body of the procedure.

“Intravascular injection of local anesthetic into any vessel can have severe adverse consequences. The most important advice is to evaluate the dye pattern prior to injection. If an unfamiliar dye pattern is present, it is best not to inject.”

Intrathecal injection of local anesthetics is a rare but very real possibility when performing procedures around the spine (see Figures 4 and 5). This can result in a so-called high spinal anesthetic. This usually requires a large volume of local anesthetic injected into the lumbar spine or small amounts injected in the upper thoracic and cervical spine. Symptoms usually occur within minutes of injection and include rapid onset of numbness often from the neck down, profound muscle weakness, shortness of breath, anxiety, hypotension, bradycardia (from blockade of the cardio-accelerator fibers), unconsciousness, and possible respiratory or cardiac arrest. Treatment involves support of both the respiratory and cardiac systems using ACLS measures. This will be discussed in detail in the next installment of this series.

Figure 4a. Typical contrast dye pattern of intrathecal injection, AP view. Figure 4b. Typical contrast dye pattern of intrathecal injection, lateral view. Courtesy of Milton Landers. Figure 5a.Typical contrast dye pattern of epidural injection, AP view. Figure 5b. Typical contrast dye pattern of epidural injection, lateral view. Courtesy of Milton Landers.

Another possible complication of attempted epidural injection is subdural block (see Figure 6). It usually manifests as a “patchy” sensory block in which the patient reports anesthesia in a wide area of the body with partial numbness. This complication is extremely rare but occurs more commonly when epidural injections are attempted in an area overlying previous spinal surgery.83 The block usually occurs 15-30 minutes after a neuraxial procedure and may require ACLS measures for support similar to IT injection.

Figure 6a. Subdural block showing typical “railroad track” appearance, AP view. Courtesy of Milton Landers Figure 6b. Subdural block, lateral view. Courtesy of Milton Landers.

Intrathecal injection, especially with large gauge needles, may result in a dural puncture headache. Signs and symptoms include positional headache with an onset within 48 hours of the procedure. Inadvertent dural puncture can occur in any region of the spine. The literature reports an incidence of inadvertent puncture in the lumbar spine ranging from 0.5-5%88 and in the cervical spine as high as 20%.89 50% of patients with dural puncture can develop post-dural puncture headache. Incidence is directly proportional to needle size. The actual mechanism of headache is unclear. Decrease in CSF pressure can cause traction on the meninges especially in the sitting or standing positions. Another possibility is that decreased CSF volume causes compensatory venodilation and increased blood flow to maintain intracranial volume homeostasis. It is thought that the venodilation causes irritation and is responsible for the headache.90 Treatment is somewhat controversial, with some advocating immediate blood patch and others conservative treatments. There is a barrage of strategies aimed at ameliorating the symptoms until the defect is healed. It has been found by a review of the literature that bed rest is ineffective.91 Other conservative strategies such as hydration, acetaminophen, non-steroidal anti-inflammatory drugs, opioids, and antiemetics have been found to control symptoms and sometimes can decrease the need for more definitive therapy,92 but rarely provide complete relief.93 The supine position is almost always the most comfortable. There is, however, no clinical evidence to support the maintenance of the supine position before or after the onset of the headache as a means of treatment.94 Several therapeutic measures have been suggested.

Pharmacological therapy has been used with variable success. Caffeine and triptans have both been tried. The most definitive treatment is epidural blood patch. The theory is that the blood, once introduced into the epidural space, will clot and occlude the perforation, preventing further CSF leak. There is no consensus as to the precise volume of blood required, but most agree that 20-30 ml is adequate.95 After the procedure, the patient should lie still in the supine position for about two hours96 and then can be mobilized. Contraindications to epidural blood patch include fever, local infection, coagulopathy, or patient refusal.

Stellate ganglion block (SGB) is associated with multiple possible complications including Horner’s syndrome, hoarseness, hematoma with airway compromise, seizure from vertebral artery injection, and death. Seizure is thought to be due to even a small amount of local anesthetic injected into the vertebral artery. Huntoon recently published his findings after anatomic dissection of the cervical spine in the area surrounding the location of injection. He suggests that, in addition to vertebral artery injection, the deep cervical vessels—located just anterior to the transverse process where SGB is usually performed—may be involved in causing seizure and hematoma after SGB.97

Lumbar sympathetic block can cause a sympathectomy as an expected side effect of the block and seizure from intravascular injection of local anesthetics. Sympathectomy can result in hypotension. The risk is greater when the block is performed bilaterally and when more concentrated solutions of local anesthetics are used. For a given volume and concentration of local anesthetic, the risk of sympathetic blockade is higher in the thoracic vs lumbar spine.83 The author has found that 5-10 cc of 0.125% bupivicaine is adequate to cause sympathectomy when the needle is accurately placed against the sympathetic chain or ganglion. Seizure results from inadvertent injection of local anesthetic into the major vessels located near the sympathetic chain. In particular, injection into the aorta can occur if intravascular placement is unrecognized. The use of contrast dye injected under live fluoroscopy is essential to avoid this complication. The author also recommends that every dose of local anesthetic be administered as a “test dose.” That is, inject no more than 1-2cc at a time and wait 30-60 seconds between doses. If seizure should occur, it is usually of short duration when dilute solutions of local anesthetics are used.

Intravascular injection of local anesthetic into any vessel can have severe adverse consequences. The most important advice is to evaluate the dye pattern prior to injection. If an unfamiliar dye pattern is present, it is best not to inject. Rather, send the patient home and try again on another day.

Post-Operative Management

Once the procedure is over, the patient should then be taken via wheelchair or gurney to the recovery area. Once there, he or she should be observed for at least 15-30 minutes and vital signs monitored. Prior to discharge the patient should be awake and conversant, have stable vital signs, and should be able to urinate. They should also have fully recovered from motor or sensory block caused by the use of local anesthetics. It is particularly important to test motor function and document full recovery to prevent the possibility of a fall and hip fracture.

As part of their discharge instructions, patients are told not to drive, to rest on the day of the procedure, and to use ice in the area of injection. The patient should not be allowed to leave the facility until it is determined that he or she has a ride available. The patient should be instructed to notify the treating physician or go to the emergency room immediately if any of the following symptoms were to occur: fever, chills, a change in mental status, severe neck or back pain, difficulty breathing, a prolonged, severe headache, numbness and/or weakness in the arms or legs, loss of control of the bladder and/or bowel, excessive redness, swelling, or drainage from the area of the injection.

Last updated on: March 18, 2013
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