Injection of medications in proximity to nerves, muscles, and skeletal structures (bursae, joints, and tendons) provides an important intervention in the management of pain and dysfunction. These medications can provide analgesia, reduce inflammation of the affected structure, and promote tissue healing directly and indirectly through facilitation of rehabilitation. Commonly, local anesthetics are used for immediate anesthesia and analgesia, corticosteroids are used to control inflammation, radiopaque contrast is used to assist any fluoroscopic confirmation, and vasoconstrictors are used to prolong local anesthetic effects or warn of intravascular injection. Injection techniques constitute both diagnostic and therapeutic modalities in many settings. As in all patient care, the origin of pain or dysfunction involves careful history taking and a complete physical examination.
Since antiquity, sharp objects have been used to inject various concoctions into the body as remedies for pain and dysfunction (1). The tools of modern-day injection procedures include the hollow needle developed by Rynd in 1845 (2) and the syringe developed by Pravaz in 1853 (3) and Wood in 1855 (4). Medications to inject for anesthesia were developed in the late 1800s, with extensive use of cocaine as a topical analgesic (5) and as an injected analgesic (6). The application of these devices and medications to achieve local anesthesia for relief of pain was described by Corning in 1894 (7). Historical information on neural blockade has been reviewed in detail by Brown and Fink (1).
Since the early 1900s, procaine had been injected into the synovium of inflamed joints for temporary relief of pain. In 1949, Hench (8) introduced systemic corticosteroids to suppress the inflammatory changes in rheumatoid arthritis. However, large doses of corticosteroids given systemically resulted in complications. In 1951, Hollander (9) introduced and reported on low-dose local (intraarticular and periarticular) injections of hydrocortisone acetate to control pain and inflammation caused by trauma and inflammatory joint disease. Historical information on intraarticular injection has been reviewed in detail by Hollander and colleagues (10). Tender points in the muscle were identified in the 1800s by multiple investigators (11,12). Kraus in 1937 (13) and Travell in 1942 (14) introduced the treatment of myofascial pain by direct trigger point injection and use of vapocoolant spray and emphasized the importance of exercise in the treatment of patients with trigger point mediated pain. Historical information on myofascial pain has been reviewed in detail by Simons (11).
The general principles for use of neural blockade were described in detail by Bonica in 1953 (15). Injections of local anesthetic agents have been shown to be effective in managing patients with acute and chronic pain. The mechanism of action is the blockade of nociceptive input along the pathway of transmission (16). Intraarticular and periarticular injections of corticosteroids have been shown to reduce inflammation and pain as well as to facilitate mobility and function (17). Unfortunately, injection of medication is often used in isolation for the management of many pain problems. It is important to use injections as one component in a vast armamentarium of techniques that are often best used in concert with each other. An injection unaccompanied by physical therapy, exercise, stretching, behavior modification, and optimization of coexisting psychological disorders is often incomplete in alleviating pain or restoring function. This is best demonstrated by the “block clinics,” which were highly popular in the 1930s and 1940s but have since been superseded by multidisciplinary pain clinics. Injection procedures should be performed within the context of comprehensive rehabilitation.
Knowledge and Training
Using injection procedures requires sufficient knowledge to understand the diagnosis and treatment of pain syndromes. Limitations, complications, advantages, and disadvantages of each procedure and alternative treatments must be understood when choosing the best therapy or combination of therapies. The practitioner must be highly skilled in injection techniques based on education, training, and experience. This requires a thorough knowledge of the anatomic basis of the procedure and the characteristics of the injectable medication, including expected side effects of the procedure as well as potential complications and their prevention and prompt treatment (16).
Injection procedures encompass a wide variety of techniques, including epidural, caudal, nerve, motor point, joint, and muscle. Although relative advantages and disadvantages exist, certain conditions comprise contraindications to perform any injection technique. Certain medical conditions also may preclude an injection. For example, a patient with severe lung disease should not have a rib block with its attendant risk for pneumothorax.
Absolute contraindications for injection procedures include patient refusal, localized infection, dermatologic conditions that preclude adequate skin preparation, existence of a tumor at the injection site, history of allergy to local anesthetic agents, the presence of severe hypovolemia, gross coagulation defects, increased intracranial pressure (for epidural procedures), and septicemia.
Among relative contraindications are the lack of education, training, and skill on the physician’s part. In addition, relative contraindications are the patient’s minor coagulation abnormalities or concurrent use of certain anticoagulants such as minidose heparin. Diabetes is a relative contraindication for injections with corticosteroids because of the possibility of hyperglycemia, glycosuria, electrolyte imbalance, and increased risk for infection.
Screening for Contraindications
Early in the interview process, the patient should be asked specific questions about conditions that would preclude the injection procedure. Firstly, anticoagulation issues must be addressed, and the patient should have been able to discontinue antiplatelet therapy (e.g., clopidogrel) or anticoagulation (e.g., unfractionated heparin or warfarin) for sufficient duration. The practitioners should be aware of current guidelines regarding anticoagulation and neuraxial procedures and have developed a standard practice ahead of time in regards to anticoagulation and injections. Secondly, the patient should have transportation and a responsible adult who can care for the patient after the procedure, especially if the injection has the potential to cause weakness or sedation. Thirdly, the patient should be appropriately fasted to reduce the chance of aspiration, particularly if he or she is likely to need sedation. Any allergies to the expected injection medications or to material such as latex should be documented and alternatives be used for the procedure.
Communication with the patient is essential at all steps involved in patient care, including injection. Providing the patient with a complete explanation of the procedure will result in the individual having increased confidence and reduced anxiety. During the procedure, the physician should continually inform and reassure the patient as to the progress of the procedure.
Although state laws vary in terms of the documentation required, informed consent involves providing enough information about the injection procedure so that the patient can intelligently decide whether or not to proceed (without external coercion or manipulation). This involves a thorough discussion of the procedure with the patient, including the possible benefits, alternative treatments, common side effects, and risks of complications. The patient should be given the opportunity to ask questions about details of the injection. The patient should not receive medications that could significantly impair responses or judgment before the consent is given. Depending on state regulations, the patient may or may not be required to sign an informed consent form. Significant complications of injection procedures are provided in Table 67-1.
Universal precautions are required for all injection techniques to reduce the incidence of transmission of infectious agents (18). These include the use of gloves and protective eye wear. Possible transmission of blood-borne pathogens during medical procedures is a common concern among patients and health care workers, owing to its potentially devastating consequences. Although this concern has largely focused on the human immunodeficiency virus (HIV), other agents, particularly hepatitis B, C, and G viruses, are of significantly greater risk. The data show that the risk to health care workers from patients is far greater than the risk to patients from health care workers (19). It is important that proper sharps disposal containers are maintained in all areas where needles are used. Hollow needle sticks pose the greatest risk for occupational transmission, with studies following health care workers after such exposures finding the following seroconversion rates: hepatitis B, 5% to 37%; hepatitis C, 3% to 10%; and HIV, 0.2% to 0.8% (19–23). Research shows that recapping a needle increases the risk for needle stick, hence needles should either be laid down in the sterile field or disposed uncapped in an appropriate container.
Optimal results of any injection depend on proper positioning of the patient before, during, and after the injection procedure. The proper position should facilitate access to the injection site, with the patient and provider being as comfortable as possible. Bony prominences should be cushioned where needed to avoid discomfort from pressure. When possible, the recumbent position is used because it is usually the most comfortable for the patient. It also minimizes the incidence of orthostatic hypotension caused by vasovagal reaction during the procedure. Positioning to avoid ergonomic stress on the patient and physician is essential. Consideration should be made for access to special equipment such as a fluoroscopic C-arm or ultrasound machine.
Strict aseptic preparation is required in all injection procedures, as well as intact skin at the site of injection. Preparation of the injection site is undertaken in a standard aseptic fashion over an area large enough to allow palpation of landmarks and any potential extension of the injection site, and sterile technique is used throughout the procedure to minimize the risks. Most injection techniques described in this chapter do not require full surgical draping; however, the phrase “sterile technique is used throughout the procedure” indicates an increased risk for major infectious complications, including epidural abscess, meningitis, and adhesive arachnoiditis.
The injection site is prepared with an antiseptic to reduce cutaneous microorganisms to the lowest level. Commonly used agents include chlorhexidine (Hibiclens, Zeneca Pharmaceuticals, Wilmington, DE), iodophors (Betadine, Purdue Frederick, Norwalk, CT), and alcohol (24). It is important for the clinician to wait about 2 minutes after the application of any of the above antiseptics to obtain maximal reduction in cutaneous bacteria. It is rarely justified to remove hair from the skin for an injection procedure (25). In addition to skin preparation, some procedures such as intradiscal procedures or prolonged catheter trial probably warrant systemic intravenous antibiotics prior to needle insertion (26). Many providers will wear a surgeon’s cap, filtration mask, and full surgical gown, although any differences in the rate of infections have been difficult to demonstrate.
General Procedural Sequence
Informed consent should be obtained from the patient, an intravenous catheter placed if sedation is to be used, and monitors applied (pulse oximeter, noninvasive blood pressure, and 3 to 5 lead EKG) if indicated based on use of sedation or on patient comorbidities. Resuscitation equipment, including oxygen source, mask and bag for ventilation, suction, code medications, and advanced airway equipment should be readily available. The patient should be properly positioned, and the injection site prepared and draped in standard aseptic fashion over an area large enough to allow palpation of landmarks. All medications, syringes, needles, and other equipment should be readily available. Syringes may vary from 3 to 12 mL. Needles may vary from as small as ½-in. (1-cm), 25-gauge needles to 3½-in. (9-cm), 21-gauge spinal needles. For convenience, an 18-gauge needle should be available to draw medications from the vial. All caregivers participating in the injection procedure should be gloved and practicing universal precautions. An audible “time-out” involving confirmation of the correct patient, injection site, and injection side (if applicable) should be performed. Then, as the procedure is underway, there should be periodic communication with the patient to screen for any problems, such as severe pain from the needle, signs of local anesthetic toxicity, paresthesias, etc. After the injection is complete, the patient should be monitored afterward for any side effects, and reexamined to evaluate for proper distribution and efficacy of analgesia. Discharge instructions should be given to the patient including symptoms to expect, symptoms which warrant calling a nurse or physician, activity restriction (if any), follow-up scheduling, and personal log to record duration and intensity of pain relief.
To reduce pain of the initial needle insertion, the skin may be stretched while rapidly piercing the skin. Once the skin is pierced, the tension is released and the needle is advanced slowly. Rapid infusion of medication may result in tissue distention, causing pain. Other methods of reducing pain with initial needle insertion include the use of topical anesthetics and vapocoolant sprays.
The procedures described in this chapter rarely require conscious sedation. In circumstances in which conscious sedation is used, monitoring should be applied to the patient as previously described, and advanced airway management tools should be readily available. Resuscitation equipment, medications, and personnel must be readily available. Any prior sedation records should be reviewed for previous sedation dose requirements and any anesthetic complications.