It is approved for intravenous injection but not for intra-arterial injection. Dexamethasone also contains a preservative benzyl alcohol ,which makes it particulate. Derby and colleagues found that particles of dexamethasone are approximately one-tenth the size of a red blood cell and did not aggregate when mixed with lidocaine.
There is no direct proof that using dexamethasone instead of other corticosteroids prevents stroke, although it does seem to give an additional margin of safety with respect to particle size and aggregation. Local anesthetic agents are commonly added as part of the injectate used for numerous spinal and pain management injection procedures. Local anesthetics are sodium channel—blocking drugs that can halt electrical impulse conduction in peripheral nerves, spinal roots, and autonomic ganglia. To block nerve conduction, the local anesthetic must cover at least 3 consecutive sodium channels nodes of Ranvier Fig.
Image-Guided Spine Interventions, 2nd Edition
Binding to the sodium channel interrupts nerve impulse transmission. The binding is reversible reversibility varying with the length of action of each anesthetic. Differential blocking occurs because fibers carrying different types of information pain, sensory, motor are of different sizes. The smallest of these are the nociceptive pain fibers. These fibers experience calcium channel blockade with the smallest amount of anesthetic because a physically small amount of material spreads sufficiently far enough to cover 3 small sodium channel nociceptive receptors, whereas that amount may not adequately cover 3 larger receptors sensory or motor.
Progressively larger fibers require a larger volume of anesthetic to produce coverage that will block enough adjacent channels to stop conduction.
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This means that pain fibers are the most sensitive, followed by sensory fibers and then motor fibers, allowing the potential for pain relief without obligatory motor blockade. Local anesthetics are organic amines, with an intermediary ester or amide linkage separating the lipophilic ringed head from the hydrophilic hydrocarbon tail. The amino-ester group of anesthetics includes members such as procaine, tetracaine, and benzocaine. These anesthetics have been used for a long time and are known to have a higher allergic potential than the amide-linked group of anesthetics lidocaine, bupivacaine, and ropivacaine now in common usage.
The amino-ester group of anesthetics is thought to have allergic potential because of the metabolite para-aminobenzoic acid PABA. The amide group of anesthetics does not have this metabolite and is known to have a very low allergic potential and little cross-reactivity.
However, the amide group may contain the preservative methylparaben. This compound is metabolized to PABA and can produce cross-reactivity for potential allergic reactions with the ester group of anesthetics. Preservative-free amide anesthetics are therefore recommended for all injection procedures.
Lidocaine represented a common first-generation member of the amide anesthetic group. It is considered to be safe except in large quantities that generally exceeded mg. It has a relatively short duration of action usually lasting only several hours. Bupivacaine is a second-generation amide anesthetic that has a prolonged duration of action. It is, however, associated with cardiac and neurotoxic reactions and has a maximum recommended safe dose of mg. Because of the poorer cardiac profile of bupivacaine that resulted from long-term sodium channel blockade in heart muscle, third-generation amide anesthetics were developed.
Ropivacaine is a member of this group and produces local anesthesia for a longer period like bupivacaine but with a better cardiac profile. Injections of local anesthetic in percutaneous spine interventions are small enough that one should generally never approach the maximum allowable dosages. Bupivacaine and ropivacaine come in different concentrations 0. The lower dosages are useful for pain relief in epidural and nerve blockage injections. The more-concentrated dosages produce motor blockade, which is an unwanted side effect with these procedures. The amounts of these drugs used in outpatient, percutaneous procedures are small compared with that needed to produce cardiac or neurotoxic effects.
Antibiotics are needed only for selected procedures in spine intervention. These include discography, intradiscal electrothermal therapy, percutaneous discectomy, vertebroplasty and kyphoplasty, implantable pumps, and stimulators.
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Most routine injection procedures do not require antibiotics. The purpose of antibiotic coverage in most of these procedures is to decrease the chance of seeding bacteria in poorly vascularized sites, such as the disk or around foreign bodies implantables. The antibiotics used for these procedures are generally not the more toxic or sophisticated ones, from the infectious disease standpoint.
As penicillin allergy is not uncommon, a broad-spectrum antibiotic with minimal or no penicillin cross-reactivity is generally chosen. Cefazolin is the most common antibiotic used for this purpose and is given in a 1-g dosage intravenously [IV] or intramuscularly [IM] 30 minutes before the procedure. In addition, it can be added to the contrast for discography procedures usually 20— mg, with the upper range used when no IV antibiotics are given.
It must be born in mind that this antibiotic will cause grand mal seizure activity if given intrathecally. No antibiotic should be included if a transdural approach is used. In some patients, allergy or lack of access to an IV may make alternate choices better. All rights reserved. Some questions raised are pertinent, and others lack the complexity to elevate the essential issues to mind.
Some readers may find the summaries somewhat vague. Others may appreciate the basic approach. In summary, this text is a useful reference for common neurologic diseases and serves well as a review of the current management. However, it may not be complex enough for the more penetrating questions concerning neurologic disorders.
Caple A. Spence, MD, and David W.
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Image Guided Spine Intervention fills an important void in medical texts devoted to treatment of spinal disorders. Its particular strength is the quality of the illustrations that demonstrate the injection techniques, especially the anatomy that is pertinent to each procedure. For each injection procedure, a number of different types of images are typically shown, including drawings, photographs, cross sections from cadavers, radiographic images, magnetic resonance imaging scans and computed tomography CT scans and three-dimensional CT surface-rendered images.
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Presenting the subject matter in this fashion fosters three-dimensional thinking, which is crucial to performing precision injection procedures. Novice spinal injectionists are well advised to treat this book as they would one of their medical school textbooks, that is, to thoroughly study the appropriate chapter before attempting any of the procedures covered in the book.
Expert injectionists, on the other hand, should browse through the book at their leisure, much as they would a coffee table book, primarily for the purpose of appreciating the superb illustrations. Although I recommend this book for both novice and expert spinal injectionists, I do have some criticisms. Each chapter contains a discussion of the indications for the procedure, as well as a separate section that presents the perspective of a neurosurgeon. A more significant failing is the lack of a discussion on interpretation of pain responses to injections.
Mastering needle placement for injections is an important skill, but interpreting the pain responses to injections is perhaps more important to the overall success of the procedure.
Although this is a complicated topic, because it requires delving into the physiology of spinal pain, the book would have been strengthened by devoting a chapter to it. Although CT guidance is a particularly elegant method for performing injections, it does have a number of drawbacks.
Certainly, it is much more time consuming and expensive than fluoroscopically guided injections.
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Of more concern is that CT guidance does not allow for an assessment of vascular uptake during contrast injection. This is an important point because the risk associated with vascular uptake is high, particularly in the cervical spine where there have been case reports of spinal cord infarct, presumably resulting from injection of radiculomedullary arteries. The authors themselves demonstrate some ambivalence in their recommendations for CT guidance, because they recommend that cervical selective nerve root injections be performed under CT guidance and that transforaminal cervical epidural injections, which call for a technique virtually identical to that for cervical selective nerve root injections, be performed under fluoroscopic guidance.
Finally, the authors include sample dictations and Current Procedural Terminology codes for the various procedures performed, which seem to be included primarily to facilitate proper billing for these procedures. Although this is important information, it is out of place in a text of this nature. These relatively minor criticisms aside, Image Guided Spine Intervention is a superb atlas of interventional spine injection procedures.
I would highly recommend it for anyone who performs these procedures on a regular basis, novice and expert alike. However, anyone who is performing these procedures should also be aware that important considerations related to the indications for injections and interpretation of the pain responses to injections are not well represented in the book and must be obtained from other sources.
Cahill has left a tremendous legacy to the spine and neurosurgery communities. He was one of the few true renaissance surgeons. Not only was he an accomplished complex spine surgeon for which his prowess is commonly acknowledged , he also made a mark in cranial and cerebrovascular surgery, and as an academic leader. In the latter vein, he established the neurosurgery residency and spine fellowship programs at the University of South Florida.
These programs have reached national and international acclaim. He performed his surgical internship and his residency in neurology at the Medical College of Virginia and his surgical residency at the University of Maryland. While there, he was elected chief resident in He completed residency training in neurosurgery at the University of Maryland and became double board certified in neurology and neurosurgery.