Management Methods

Management Methods (81)

Children categories

Injection Procedures

Injection Procedures (81)

The injection procedures outlined in this chapter are appropriately used in conjunction with other aspects of rehabilitation to reduce pain and increase function. Sterile technique and knowledge of anatomic relationships are required. Aspiration is performed before injecting and is repeated as necessary throughout administration of medication to prevent intravascular injection. For optimal results and safety with injection techniques, the practitioner needs the necessary skill, training, and education to perform the procedures. Haste and failure to observe the necessary precautions by the practitioner increase the risks for any procedure. Knowledge of the anatomy pertaining to each injection procedure is a requirement for safe and successful outcomes in even the simplest injection. 

 

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Thứ bảy, 01 Tháng 3 2014 22:12

Celiac Plexus Block

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Indications

Celiac plexus blockade is useful for diagnosing and treating pain of sympathetic origin. This includes pain involving the viscera, abdomen, and pelvis, secondary to cancer, complex regional pain syndrome, and vasospastic disorders.

Techniques

After informed consent is obtained, the patient is placed in the prone position with a pillow under the abdomen. The inferior edge of the spinous process of the first lumbar vertebra and the lower border of each 12th rib at 7 cm from the spinous process of the first lumbar vertebra is identified and marked. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. A 6-in. (15-cm), 22-gauge needle is inserted at the mark on the 12th rib toward the spinous process of L1 at 60 degrees from perpendicular. The needle is advanced until it contacts the lateral side of the L1 vertebra. The depth is noted at this point. The needle is pulled back to a subcutaneous level and reinserted at 45 degrees toward the spinous process of L1 and slightly cephalad until it slips off the edge of the vertebra. This is about 2 to 3 cm deeper than the original depth. After negative aspiration, 20 mL of local anesthetic is injected (Fig. 67-8).

FIGURE 67-8. Celiac plexus block. Approach for celiac plexus injection and neural blockade.

Comments

This technique is commonly used for differential diagnosis and is the preferred treatment of sympathetic mediated pain involving the viscera and pelvis. The celiac plexus is located in the prevertebral region at the level of the L1 vertebral body. It is formed by the right and left celiacs, superior mesenteric, and aorticorenal ganglia. Autonomic mediated pain does not usually correspond to segmental or peripheral nerve distribution. Lateral and anteroposterior fluoroscopic views are recommended to ensure that the needle is properly positioned. It is recommended that intravenous access be available before the block in the event of hypotension from sympathectomy or toxicity from intravascular injection. It is necessary to perform this procedure bilaterally for a complete celiac plexus block. Rarely are ablative nerve procedures (neurolysis) required in the management of sympathetic mediated pain.

Complications

These injections are normally completed with fluoroscopic guidance, as noted in Chapter 68. Performance of this procedure out of a fully monitored environment is not recommended. Resuscitation equipment and personnel must be readily available. Although appearing technically simple, this block has multiple hazards, owing to the proximity of the aorta, kidney, pancreas, diaphragm, thoracic duct, and other vascular structures. Intraarterial or intradural injection of local anesthetic may result in death, seizure, respiratory arrest, cardiac arrest, cerebral damage with multiple sequelae, and other lesser complications. The risk for intravascular injection may be reduced if a test dose is given, the total dose is injected incrementally, and aspiration is performed before each injection.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
Thứ bảy, 01 Tháng 3 2014 14:09

Spinal Nerve Root Block

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Indications

Nerve root blockade is useful in diagnosing and treating pain present in a dermatomal distribution.

Techniques

After informed consent is obtained, the patient is placed in the prone position, and a line perpendicular to the axis of the spine is drawn across the top of the spinous process. In the lumbar region, a line drawn along the inferior edges of the two transverse processes will intersect the spinous process of the same vertebra at its most cephalad point. In the thoracic region, this line can extend as much as two vertebral levels caudally, particularly in the midthoracic region. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and strict sterile technique is used throughout the procedure. A 4-in. (10-cm), 22-gauge needle is inserted 3 to 5 cm laterally from the midline, which should overlie the transverse process. The needle is advanced perpendicular to the skin until contact is made with the transverse process. The depth is noted at this point. The needle is pulled back to skin level and redirected to pass below the transverse process. Appropriate response with a nerve stimulator or paresthesia indicates correct placement. After negative aspiration, 2 to 5 mL of local anesthetic is injected to block the spinal nerve root (Fig. 67-7).

FIGURE 67-7. Spinal nerve root block. A: Fluoroscopic view for L5 nerve root block (arrow). B: Approach for spinal nerve root injection and neural blockade.

Comments

The technique of nerve root blockade is similar to that of the intercostal block. The transverse process serves as the depth marker for nerve roots. A sound knowledge of the relationship of the transverse process and the spinous process is necessary to locate precisely the selected nerve root. Any disorder that responds to intercostal blockade also should respond to selective nerve root blockade.

Complications

Complications usually occur from injection of local anesthetic agents into areas adjacent to the paravertebral space such as the epidural or subarachnoid space. Puncture of retroperitoneal organs and bleed also can occur if care is not taken to consider the anatomy fully.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
Thứ bảy, 01 Tháng 3 2014 03:07

Intercostal Nerve Block

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Indications

Intercostal blockade is used to treat pain from herpes zoster, rib fractures, and intercostal neuropathies. It is also used to diagnose unusual abdominal or chest wall pain.

Techniques

After informed consent is obtained, the patient is placed in either the prone or lateral position. In the lateral position, the injection site is along the midaxillary line, which may result in incomplete blockade of the lateral cutaneous branch of the intercostal nerve. In the prone position, the injection site is along the angle of the rib posteriorly. The ribs to be injected are marked at the angle of the rib or along the midaxillary line. If the ribs are not easily palpated, an alternative injection technique such as an epidural or root block may be considered. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and strict sterile technique is used throughout the procedure. The index finger of the nondominant hand is used to palpate the rib and identify the intercostal space. The tip of the finger is placed in the intercostal space and the skin slid over the superior rib. A 5 8-in. (1.5-cm), 25-gauge needle is inserted directly over the rib until contact is made with the rib. The long axis of the needle and syringe should have a slight cephalad tilt and be perpendicular to the long axis of the rib. The needle is then moved to the inferior edge of the rib by walking (i.e., repeatedly slightly withdrawing) the needle in the subcutaneous tissue and allowing the skin to move back slowly to its original position. The needle should retain its slight cephalad tilt. As the needle slips off the inferior ridge of the rib, the tip is advanced about 3 mm and then aspirated. If aspiration is positive for blood or air, the needle should be repositioned; otherwise, 2 to 5 mL of local anesthetic is injected to block the intercostal nerve (Fig. 67-6).

FIGURE 67-6. Intercostal nerve block. Approach for intercostal nerve injection and neural blockade with injection sites marked at the angle of the rib. A: The tip of the finger is placed in the intercostal space and the slid (arrow) slid over the superior rib. B: The needle is inserted directly over the rib until contact is made. C: The needle is walked (arrow) to the inferior edge of the rib while maintaining a slight cephalad tilt. D: As the needle slips off the inferior edge of the rib, advance the needle approximately 3 mm (arrow), where it is adjacent to the intercostal nerve.

Comments

A new needle should be used for each nerve blocked. Intercostal blocks are a simple and effective method of providing analgesia for painful disorders of the chest and abdominal walls. Because of the wide distribution of intercostal nerve innervation, the intercostal nerves above and below the level of pain must be blocked to gain optimal pain relief.

Complications

Intercostal blockade is often underused because of an exaggerated fear of pneumothorax. In actuality, less than 1% of all patients having an intercostal block develop a pneumothorax. Most can be easily treated with administration of supplemental oxygen and close observation and, when necessary, needle aspiration of air. Only those pneumothoraces that result in significant dyspnea or those under tension require chest tube thoracotomy and vacuum drainage. Local anesthetic toxicity can occur because of the rapid absorption after intercostal injection. Toxicity can easily be avoided by limiting the total amount injected to a known, safe level (see Table 67-4).

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
Thứ sáu, 28 Tháng 2 2014 12:16

Suprascapular Nerve Block

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Indication

The suprascapular nerve blockade is useful in patients as a therapeutic procedure for pain in the shoulder region. This block is used as an adjuvant to physical therapy in patients with limited range of motion secondary to arthritic shoulder pain, shoulder-hand syndrome, and shoulder pain.

Techniques

After informed consent is obtained, the patient is placed in the sitting position. The spine of the scapula is divided by a line formed by the bisection of the scapular angle. The upper outer quadrant formed from the spine of the scapula and the vertical line bisecting the angle of the scapula is marked, and a point is marked 2 cm anteriorly along this line for needle insertion. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. A 3-in. (8-cm), 23- to 25-gauge needle is inserted perpendicular to the skin and, using a nerve stimulator, advanced until needle placement is confirmed by movements of the supraspinatus and infraspinatus muscles. After negative aspiration, 5 mL of local anesthetic is injected (Fig. 67-5).

FIGURE 67-5. Suprascapular nerve block. Approach for suprascapular nerve injection and neural blockade.

Comments

The suprascapular nerve is a branch from the trunk of the brachial plexus, which enters the scapular region through the suprascapular notch on the cephalic border of the scapula. Confirmation of the block is determined when abduction of the arm is diminished over the first 15 degrees. If a nerve stimulator is not available, the same technique is used, with the needle advanced to the dorsal surface of the scapula. The needle is then walked along the edge of the scapula to the suprascapular notch.

Complications

Intraneural injection may result in nerve damage. Severe pain on injection suggests the possibility of an intraneural injection, and the needle should be repositioned immediately. Hematoma and intravascular injection are possible, owing to the close proximity of the suprascapular vessels. Pneumothorax is possible if the needle is advanced beyond the scapula and into the pleura. Most pneumothoraces can be treated easily with administration of supplemental oxygen and close observation and, when necessary, needle aspiration of air. Only those pneumothoraces that result in significant dyspnea or those under tension require chest tube thoracotomy and vacuum drainage.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice

Indications

Cervical epidural steroid injection (ESI) is primarily used to treat pain arising from cervical herniated discs or spinal stenosis.

Techniques

After informed consent is obtained, the patient is placed in the prone, lateral decubitus, or sitting position with the neck flexed. The sitting position, with the head resting on the examination table, provides better stabilization of the neck during the procedure but may be a problem if the patient is prone to light-headedness. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. Local skin anesthesia is provided with 1% to 2% lidocaine at the C7-T1 interspace. A Tuohy epidural needle is advanced in a midline, horizontal fashion until well seated in the posterior ligaments. A winged needle is preferred because it allows two-handed control of the needle as it is directed toward the epidural space. A midline or paramedian approach may be used, although large epidural veins lie laterally. The stylet is then removed, and a “loss-of-resistance” syringe is attached to the hub of the needle. Two to three mL of air or normal saline should be in the syringe. The needle is slowly advanced 1 to 2 mm at a time, with constant checking for loss of resistance by tapping on the plunger of the syringe. Alternatively, the needle can be advanced slowly and continuously with constant light pressure on the plunger. Once a distinct loss of resistance is obtained, the needle is halted, and an attempt is made to aspirate blood or CSF. After negative aspiration, 6 mg of betamethasone sodium phosphate and acetate or equivalent is injected. Care should be taken to flush the needle with normal saline and to replace the stylet before the needle is removed to avoid depositing steroid in the needle track to the skin.

Comments

Cervical epidural injections are similar in technique to lumbar epidural injections in some respects. The cervical spinous processes at C7 and T1 are oriented almost horizontally, as in the lumbar region. Of note, caution must be taken because the cervical ligamentum flavum is thinner in this region than at any other spinal level, and the width of the epidural space is only 3 to 4 mm. A catheter may be placed through a nonshearing needle to achieve the desired level under fluoroscopic guidance.

Complications

The most frequent complication of a cervical epidural injection is subarachnoid penetration (wet tap) due to the thinner ligamentum flavum and the reduced width of the cervical epidural space. Cervical epidural injections should only be attempted by those physicians with a great deal of experience with lumbar epidural techniques, because the spinal cord lies in close proximity to the epidural space. These injections are normally completed with fluoroscopic guidance, as noted in Chapter 68. Injection of local anesthetics into the cervical epidural space can result in respiratory depression, particularly if the phrenic nerve roots are blocked (C3 to C5).

Infection or bleeding into the closed epidural space also can result in significant neurologic deficits, including quadriplegia. Any complaint of increasing pain or neurologic changes should be investigated immediately. Early recognition can prevent permanent injury.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
Thứ năm, 27 Tháng 2 2014 23:12

Stellate Ganglion Block

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Indication

Stellate ganglion blockade is useful for diagnosing and treating pain of sympathetic origin. This includes pain involving the face, head, neck, and upper extremities secondary to complex regional pain syndrome, acute herpes zoster, and phantom limb pain.

Techniques

After informed consent is obtained, the patient is placed in the supine position with a pillow under the shoulders and the neck extended. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. The transverse process of the C6 vertebral body is palpated between the cricoid cartilage and the carotid artery. A 1½-in. (4-cm), 22-gauge needle is inserted vertically and advanced to touch the periosteum of the C6 transverse process. The needle is withdrawn slightly, and after negative aspiration, a 1-mL test dose of local anesthetic is injected. After unremarkable test dose and repeated aspiration, 9 mL of local anesthetic is injected, in divided doses with continuous monitoring, to block the stellate ganglion (Fig. 67-4).

FIGURE 67-4. Stellate ganglion block. Approach for stellate ganglion injection and neural blockade. Cross-section at C6.

Comments

This technique is commonly used for differential diagnosis and is the preferred treatment of sympathetic mediated pain involving the upper extremity. The stellate ganglion is located between the anterolateral surface of the seventh cervical vertebral body and neck of the first rib. It is formed by the inferior cervical ganglion and first thoracic sympathetic ganglion. Autonomic mediated pain does not usually correspond to segmental or peripheral nerve distribution.

This procedure requires full monitoring capability to include blood pressure, EKG, heart rate, level of consciousness, and pulse oximeter. Temperature should be monitored and recorded for each hand before, during, and after the procedure. The patient is continuously monitored for change and level of consciousness or for adverse reaction. Successful stellate ganglion blockade is suggested by rising temperature on the block side as well as evidence of a Horner’s syndrome (miosis, ptosis, anhydrosis, and enophthalmos). Nasal congestion and hoarseness may occur with this injection. It is recommended that intravenous access be available before the block in the event of intravascular injection resulting in seizure activity or cardiovascular instability (34). Rarely are ablative nerve procedures (neurolysis) recommended in the management of sympathetic mediated pain of the upper extremity.

Complications

Performance of this procedure outside of a fully monitored environment is not recommended. Resuscitation equipment and personnel must be readily available. Although appearing technically simple, this block has multiple potential hazards, owing to the proximity of the common carotid artery, vagus and recurrent laryngeal nerves, jugular vein, vertebral artery, trachea, esophagus, lung, and dura. Intraarterial and intradural injection of local anesthetic may result in death, seizure, respiratory arrest, cardiac arrest, cerebral damage with multiple sequelae, and other lesser complications. The risk for intervascular injection may be reduced if a test dose is given, the total dose is injected incrementally, and aspiration is performed before each injection.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
Thứ năm, 27 Tháng 2 2014 19:00

Occipital Nerve Block

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Indication

The occipital nerve blockade is used both diagnostically and therapeutically in the treatment of occipital neuralgia.

Techniques

After informed consent is obtained, the patient is placed in the sitting position with the head flexed forward. The occipital nerve is located at the midpoint between the mastoid process and the greater occipital protuberance at the superior nuchal line. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. A 1-in. (2.5-cm), 21- to 25-gauge needle is inserted perpendicular to the superior nuchal line. Before reaching the periosteum of the skull, paresthesias in the occipital nerve distribution may be elicited. If not, the periosteum is contacted and the needle withdrawn slightly. After negative aspiration, 3 to 5 mL of local anesthetic is injected to block the occipital nerve (Fig. 67-3).

FIGURE 67-3. Occipital nerve block. Approach for occipital nerve block and neural blockade.

Comments

Localization of the nerve may be accomplished by palpation of the occipital artery just lateral to the nuchal ridge. The nerve runs with the occipital artery, innervating the posterior portion of the skull. A nerve stimulator may be used for precise needle placement. An alternate approach may be used with the patient positioned as above with anatomic landmarks identified. A 2-in. (5-cm), 21- to 25-gauge needle is inserted subcutaneously along the middle third of the superior nuchal line.

After negative aspiration, 5 mL of local anesthetic is injected to block the greater and lesser occipital nerves (see Fig. 67-3).

Complications

Intravascular injection can occur, resulting in systemic toxicity and seizures, especially if larger volumes are used. Bleeding due to vascular injury also may occur. Nerve injury secondary to injection into the nerve may result in persistent numbness over the posterior portion of the scalp.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
Thứ năm, 27 Tháng 2 2014 15:48

Common Nerve Block Techniques

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General

The placement of local anesthetics at various sites along the neural axis is an important tool in the diagnosis and treatment of a variety of pain disorders, such as complex regional pain syndrome and postherpetic neuralgia. Peripheral nerve blocks also can provide muscle relaxation and pain relief to facilitate an active physical therapy program.

When the point of injection has been determined, it is best marked with the tip of a retracted ballpoint pen or a needle hub by pressing the skin to produce a temporary indentation to mark the point of entry. The skin is then prepared in a standard sterile fashion, and sterile technique is used throughout the procedure. The skin and subcutaneous tissue at the injection site may be anesthetized by injecting 1% lidocaine with no epinephrine using a 25- to 30-gauge needle. Alternatively, a vapocoolant spray or analgesic cream applied to the skin surface may be used to provide adequate anesthesia. Before injecting the medication, an attempt to aspirate should always be made to avoid accidental intravascular injection. After ensuring that the needle is in the joint space, the medication should be injected in a slow, steady fashion.

Indications for Nerve Blocks

Neural blockade may be used for the diagnosis, prognosis, and treatment of pain. Selective nerve blocks are indicated to determine the etiology of pain by isolation of specific anatomic structures. Selected nerve blockade is used to determine specific nociceptive pathways and other mechanisms involved in pain generation. Diagnostic blocks assist in narrowing the differential diagnosis of the site and cause of pain. Prognostic neural blockade is used to evaluate the possible outcome from neurolytic procedures. Therapeutic nerve blocks are indicated to decrease morbidity in acute postoperative pain, posttraumatic pain, and pain resulting from self-limiting conditions. Nerve blockade may provide rapid relief of pain and facilitate the patient’s participation in a comprehensive rehabilitation program. Therapeutic nerve blocks may interrupt the pain cycle sufficiently to provide prolonged pain relief.

Contraindications for Nerve Blocks

Absolute contraindications for regional anesthesia include patient refusal, localized infection, a skin condition that prevents adequate skin preparation, the existence of a tumor at the injection site, a history of allergy to local anesthetics, the presence of severe hypovolemia (for blocks that could result in significant sympathetic blockade), gross coagulation defects, septicemia, and increased intracranial pressure (spinal, caudal, and epidural).

Prilocaine should not be used in doses greater than 600 mg, because significant methemoglobinemia may result. The use of corticosteroids with preservatives is contraindicated in epidural and subarachnoid techniques because the preservative may result in seizures and permanent CNS damage.

Relative contraindications include general medical conditions that would put the patient at increased risk. These include aortic stenosis, severe lung disease, sickle cell anemia, and preexisting neurologic diseases such as multiple sclerosis or amyotrophic lateral sclerosis, which could be worsened during regional anesthesia.

Complications

Complications common to nerve blocks include hypotension from sympathetic blockade. This usually occurs in patients who are hypovolemic and receive a block covering a large portion of the sympathetic chain ganglia, for example, during spinal or epidural blockade. Local anesthetic overdose or intravascular injection can result in CNS toxicity and, in some cases, pulmonary and cardiac arrest. Nerve injury from contact with the needle may occur but is rare, especially when a short, beveled needle is used. Other complications are dependent on the location of the block and are discussed separately.

Techniques

Before the injection, the appropriate landmarks are located and marked. The skin is scrubbed with antiseptic and allowed to dry for 2 minutes. The wearing of sterile gloves is required so that the bony landmarks in the sterile field may be palpated throughout the procedure. The standard sterile technique is required to minimize the risk for infection. It is preferable to use single-dose vials of the local anesthetic because this further reduces the risk for infection. A 25- to 27-gauge needle is used with 1% lidocaine with no epinephrine to raise a small skin wheal for skin anesthesia. Routinely a 1½-in. (4-cm), 21- to 25-gauge needle transverses the skin, joint capsule, synovial lining and then slides smoothly into the joint cavity.

Aspiration is done to ensure there is no intravascular penetration. If penetration occurs, the needle should be repositioned and aspirated to ensure that blood vessels have been avoided; then the medication is slowly injected. After the medication has been injected, the needle should be cleared with a new syringe containing a small amount of lidocaine or saline. The needle is then withdrawn with pressure applied to minimize bleeding.

Nerve Stimulator

Peripheral nerves may be localized with a nerve stimulator using a small adjustable amount of electrical current to depolarize neural tissue in proximity to the needle. The cathode (negative) terminal is connected to the needle, and the anode (positive) terminal is connected to a grounding patch. The stimulator initially is set to deliver 10 to 20 mA of current to detect the general area of the nerve. The current is then reduced to further localize the nerve. The needle is positioned to produce the maximal twitch at the lowest stimulus. The needle is usually adjacent to the nerve when 0.5 to 0.1 mA produces motor stimulation with an insulated needle and 1 mA with an uninsulated needle (Fig. 67-1).

FIGURE 67-1. Nerve stimulator attached to regional block nerve. The negative (black) lead is attached to the exploring needle, whereas the positive (red) lead is connected to the reference electrocardiogram pad used as the ground reference. Note the current distribution pattern for this uninsulated needle. 

Nerve stimulators do not substitute for knowledge of anatomy and proper needle placement. Insulated needles increase the point of maximal current density at the needle tip and are used for precise localization of specific nerves. Uninsulated needles are often accurate enough for many nerve blocks; however, both the tip and shaft of the needle have sufficient current density to stimulate a nerve. Local muscle twitches from the shaft of the uninsulated needle should not be confused with the response from the nerve to be blocked (Fig. 67-2).

FIGURE 67-2. Current density pattern for insulated and uninsulated needles. 

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice

The injection procedures described here are associated with various side effects, although the risk for significant complications is very low. The physician who performs injection procedures should have the training and education to recognize and treat a wide range of potential complications (Table 67-4). Advanced cardiac life support (ACLS) protocols are used in airway management and cardiorespiratory resuscitation (27).

aSympathetic block above T-4 adds cardioaccelerator nerve blockade to the vasodilatation seen with blockade below T-4; total spinal block may have rapid onset.
From Covino BG. Clinical pharmacology of local anesthetic agents. In: Cousins MJ, Bridenbaugh PO, eds. Neural Blockade in Clinical Anesthesia and Management of Pain. 2nd ed. Philadelphia, PA: JB Lippincott; 1988:134, with permission.

Systemic Toxic Reaction

Various toxic reactions have been reported after use of local anesthetics, but with very low incidence. Local anesthetic agents are relatively lipid-soluble, low-molecular-weight compounds that readily cross the blood-brain barrier. As toxic levels are reached, disturbances of CNS function are observed initially, producing signs of CNS excitation. Early symptoms of overdose include headache, ringing in the ears, numbness in the tongue and mouth, twitching of facial muscles, and restlessness. As blood levels increase, generalized tonic-clonic seizures may occur. If sufficiently high blood levels are reached, the initial excitation is followed by generalized CNS depression. Respiratory depression and ultimately respiratory arrest may occur secondary to the toxic effect of the local anesthetic agent on the respiratory center in the medulla. Occasionally, the excitatory phase may not occur, and toxicity presents as CNS depression.

Cardiovascular system (CVS) effects either result indirectly from inhibition of autonomic pathways during regional anesthesia (as in high spinal or epidural block) or are directly due to depressant actions on the CVS. The CVS is generally more resistant to toxicity than the CNS. The CVS-to-CNS toxicity ratio is lower for bupivacaine and etidocaine than for lidocaine. Convulsive activity may initially be associated with an increase in heart rate, blood pressure, and cardiac output. As the blood concentration of a local anesthetic agent increases further, CVS depression occurs, resulting in a decrease in blood pressure secondary to myocardial depression, impaired cardiac conduction, and eventual peripheral vasodilation. Ultimately, circulatory collapse and cardiac arrest may result. In addition, certain agents such as bupivacaine may cause ventricular arrhythmias and fatal ventricular fibrillation. The onset of CVS depression with bupivacaine may occur relatively early and be resistant to usual therapeutic modalities. The pregnant patient is more sensitive to the cardiotoxic effects of bupivacaine. Systemic toxicity may be due to unintentional intravascular injection or drug overdose. Intravascular injection produces signs of toxicity (usually seizures) during the injection itself, especially if injected directly into blood vessels supplying to the brain (e.g., vertebral arteries). A relative overdose results in toxic reactions when peak blood levels are reached, about 20 to 30 minutes after the injection. Factors that affect the blood concentration (site of injection, drug, dosage, addition of vasoconstrictor, speed of injection) influence the potential for systemic toxic reactions to develop.

To minimize systemic reactions to local anesthetic agents, intravascular injection (the most common cause of seizures) should be avoided. Careful, intermittent aspiration should be used while injecting large quantities of local anesthetic agents. Patient complaints of metallic taste, numbness around the mouth, and ringing in the ears are suggestive of intravascular needle placement. Patients may be premedicated with midazolam or diazepam to raise the seizure threshold if necessary.

Systemic toxicity is treated with general supportive measures. If early signs of toxicity occur, constant verbal contact should be maintained, oxygen administered, breathing encouraged, and CVS function monitored. If seizure activity occurs, a clear airway should be maintained and oxygen administered by assisted or controlled ventilation. If seizures continue, thiopental (50 to 100 mg) or diazepam (5 to 10 mg) should be administered intravenously, avoiding large doses of thiopental, which may produce additional CVS or CNS depression. If airway maintenance is jeopardized, succinylcholine should be used to facilitate endotracheal intubation. Muscular convulsive activity is terminated with succinylcholine, but the seizure activity in the brain is not affected. If CVS depression occurs, hypotension should be treated by increasing intravenous fluids, positioning the patient properly (elevate the legs), and using vasopressors such as ephedrine or epinephrine (Table 67-5).

CNS, central nervous system; CVS, cardiovascular system; IV, intravenous.
From Covino BG. Clinical pharmacology of local anesthetic agents. In: Cousins MJ, Bridenbaugh PO, eds. Neural Blockade in Clinical Anesthesia and Management of Pain. 2nd ed. Philadelphia, PA: JB Lippincott; 1988:135, with permission.

Epinephrine Reaction

Reaction to epinephrine may sometimes be confused with local anesthetic overdose. Systemic absorption of epinephrine produces palpitations and restlessness about 1 to 2 minutes after completion of the injection. Avoiding epinephrine should be considered in patients who are sensitivity prone (e.g., hypertensive, or hyperthyroid, arrhythmic patients). Epinephrine should not be used for blocks of the fingers, toes, or penis, owing to the possibility of localized vasoconstriction. An epinephrine reaction is treated with a small dose of fast-acting barbiturate to reduce blood pressure to within normal limits. If hypertension persists, a vasodilator may be required.

Vasovagal Reaction

Vasovagal reaction is a frequent response to injection procedures that is attributable to physiologic and psychological factors. This response may result in bradycardia, hypotension, and loss of consciousness. This usually occurs in the initial portion of the procedure when skin is penetrated before any medication is injected. Vasovagal reaction is often mislabeled as an allergic reaction to the medication. This response is often preceded by dizziness, faintness, sweating, and pallor. Vasovagal reaction is rapidly reversible by removing painful stimuli and placing the patient in a head down and legs up position to improve venous blood return to the heart. If this fails to relieve the symptoms, then treatment with general supportive measures is indicated, including airway maintenance, oxygen, intravenous fluids, anticholinergics such as atropine, and vasopressors such as ephedrine (see Table 67-5).

Allergic Reaction

An allergic reaction to local anesthetic agents rarely occurs and in some instances may be confused with a vasovagal reaction or a reaction to epinephrine. Ester anesthetic agents (e.g., procaine, tetracaine) are more frequently associated with allergic reactions than amide anesthetic agents (e.g., lidocaine, ropivacaine), because esters are derivatives of paraaminobenzoic acid (PABA). However, the use of amides from multiple-dose vials may result in an allergic reaction secondary to the preservative methylparaben. Allergic reaction is treated with general supportive measures and the administration of fluids, antihistamine, steroids, and epinephrine (if warranted), as well as removal of any additional offending agent. The patient should be closely monitored for a clear airway.

Although this is a rare event, if there is a question of patient hypersensitivity to anesthetic agents, intradermal skin tests (injection with diluted [1:1,000] followed by undiluted local anesthetic) can be used successfully to diagnose adverse responses. However, false-positive results may occur. Anaphylactic shock is treated as systemic toxic reaction with attention to maintaining cardiovascular and ventilatory function (see Table 67-5).

Accidental Spinal Block

Inadvertent subarachnoid or epidural blockade can occur with any injection that is performed close to the spine. These injections include intercostal nerve blocks, sympathetic blocks, and nerve root injections. Proper equipment and staff should always be available to treat any possible complication. This includes the ability to administer fluids and vasopressors if the patient develops hypotension from sympathetic blockade and to maintain ventilation with oxygen if the patient has impaired respiratory function.

Concurrent Medical Episode

Concurrent medical problems may be exacerbated by injection procedures. Hypotension will reduce myocardial profusion and may be a major factor for reinfarction in patients with ischemic heart disease. Patients with poorly treated hypertension risk developing hypertensive crisis, myocardial infarction, or stroke triggered by the stress of the procedure. Patients with chronic renal failure are more susceptible to toxicity from local anesthetics. Diabetic patients have an increased sensitivity to the effects of corticosteroid injection. Patients with liver disease may have reduced metabolism of local anesthetic medications resulting in an increased possibility of toxicity at standard doses. Other medical illnesses may decompensate clinically, owing to mild toxicity and changes in fluid and electrolyte balance. These risks are minimized with appropriate monitoring and optimal medication regimes. Patients should be medically stable before undergoing elective injection procedures.

Infection

Although infectious complications rarely occur, cutaneous and joint infection, epidural abscess, bacterial meningitis, and adhesive arachnoiditis have been associated with injection procedures. Epidural abscess may cause spinal cord compression. Signs and symptoms of epidural abscess are severe back pain, localized tenderness, fever, leukocytosis, cervical rigidity, increased protein and leukocytes in the cerebral spinal fluid, progressive neurologic symptoms, and abnormal imaging studies of the spine. Early diagnosis and prompt treatment are essential to avoid catastrophic complications. Meningitis and adhesive arachnoiditis are the result of the introduction of bacterial or irritating contaminants into the spinal fluid as well as trauma during the procedure.

Pneumothorax

Injections into the thoracic region have the potential to cause a pneumothorax. In procedures that put the patient at risk for needle penetration of the lung, less than 1% develop a pneumothorax (32,33). Most of these patients can be easily treated with administration of 100% oxygen, close monitoring (e.g., O2 saturation, vital signs) of the patient, and, when necessary, needle aspiration of air. Only those pneumothoraces that result in significant dyspnea or those under tension require chest tube thoracostomy and vacuum drainage. Bilateral thoracic procedures should be undertaken with caution due to potential risk of bilateral pneumothorax.

Nerve Injury

Three major factors contribute to nerve injury during injections: trauma, toxicity, and ischemia, with all three contributing to most nerve injuries. Nerve blocks are the result of infiltration of anesthetic agents around the nerve, not directly into the neural tissue. Intraneural injections directly injure nerve fibers and cause a breakdown in the blood-nerve barrier. The use of short, beveled needles has significantly reduced nerve injuries from injections. Intense pain in the nerve distribution and high resistance upon injection are often the result of intraneural needle placement and necessitate immediate cessation of the injection and repositioning of the needle.

Other Complications

Local anesthetic agents used in recommended clinical concentrations have minimal irritating effects on the nerves, skin, and subcutaneous tissue. Complete recovery of function occurs after regional blocks. The administration of large doses of prilocaine may lead to methemoglobinemia, owing to the accumulation of a metabolite (OH-toluidine) that can convert hemoglobin to methemoglobin. It may be treated with intravenous methylene blue.

Hypotension may result from sympathetic blockade. This commonly occurs in patients who are hypovolemic and receive a spinal or epidural block involving a large portion of the sympathetic chain ganglia. Hypotension is treated with general supportive measures, including administration of intravenous fluids, vasopressors such as epinephrine to maintain blood pressure within normal limits, and proper positioning (elevating the legs). Bradycardia from blockade of sympathetic outflow from T1-4 may require prompt treatment.

Bleeding at the site of injection occurs commonly at the surface. Hematoma at the site of injection is a possibility but usually not clinically significant. If arterial puncture occurs, prolonged direct pressure is usually adequate to prevent the development of a hematoma.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
 

Injection procedures use three primary classes of medication: local anesthetic agents, neurolytic agents, and corticosteroids. All of these medications have multiple clinical applications and are documented to be safe and effective when used appropriately. It is incumbent on the practitioner to understand the efficacy, complications, and common side effects of these agents.

Anesthetic Agents

The mechanism of local anesthetic action is a reversible block of ion flux through the axon’s sodium channels. By blocking transmission from the peripheral nerves, no input is detected at the central nervous system (CNS). The degree of neural blockade depends on the properties, absorption, amount, location, and other characteristics of the drug injected (28,29) (Table 67-2). For purposes of attaining longer duration analgesia, agents such as bupivacaine or ropivacaine are acceptable and safe when used within the dosing guidelines. Anesthetic agents with fast onset, such as lidocaine, are useful particularly for skin infiltration prior to block insertion or for rapid diagnosis of the pain generator site. Local anesthetics should be chosen appropriately for both the purpose and the site of injection. For example, commercial preparations may come with preservatives, making them potentially neurotoxic if given intrathecally. Therefore, it is imperative to verify that the particular medication preparation is approved for the desired use. This information is available in many locations, including the package insert for the medication.

aProcaine = 1.
CNS, central nervous system; CVS, cerebrovascular system.

When higher doses of local anesthetics are used (i.e., near the upper limit of recommended dose), are injected near highly vascular structures (face, intercostals), or injected near the neuraxis (paravertebral, epidural, or intrathecal), monitoring of the patient is highly recommended. Verbal communication, constant screening for symptoms, and pulse oximetry can identify any CNS toxicity, while the electrocardiogram and blood pressure can identify any cardiovascular toxicity. If signs of toxicity or high spinal block are present, injection should be suspended and the patient closely evaluated and/or supported.

Neurolytic Agents

Neurolytic nerve blocks were popular in the early 1900s. However, improved use of analgesics, as well as the use of radiofrequency and cryoablative techniques, has replaced their use in most instances. Alcohol and phenol are the most widely used neurolytic agents in the United States. These agents indiscriminately affect motor and sensory nerves.

Phenol can be used intrathecally and epidurally, as well as for peripheral nerve and motor point blocks. It is poorly soluble in water and is often added to glycerin to achieve concentrations higher than 7%. It also can be added to radiographic contrast to allow fluoroscopic visualization of the spread during injection. Phenol has a local anesthetic effect, resulting in less pain after the injection. Because of this, long-term effects of the block cannot be evaluated for 24 to 48 hours after the effects of the local anesthetic dissipate. Doses greater than 100 mg can result in serious toxicity (30).

Alcohol is used primarily intrathecally for nerve roots and locally for sympathetic blockade. Patient positioning with intrathecal use is extremely important, because alcohol is hypobaric in cerebrospinal fluid (CSF). It is readily soluble in body tissues and produces intense burning on injection. It requires 12 to 24 hours before block effects can be determined.

Corticosteroids

Glucocorticosteroids are used in the injection treatment of inflammatory processes (31) (Table 67-3). Some of the commonly used forms of corticosteroid available for intraarticular injections are listed as follows:

  • • Betamethasone sodium phosphate and acetate (Celestone Soluspan), 6 mg/mL
  • • Methylprednisolone acetate (Depo-Medrol), 40 and 80 mg/mL
  • • Prednisolone sodium phosphate (Hydeltrasol), 20 mg/mL
  • • Prednisolone terbutate (Hydeltra-TBA), 20 mg/mL
  • • Triamcinolone acetonide (Kenalog), 40 mg/mL
  • • Triamcinolone hexacetonide (Aristospan) 20 mg/mL

aRelative to hydrocortisone.

These corticosteroids vary in strength, concentration, duration, and side effects, and all are effective. Triamcinolone hexacetonide has the longest duration of suppression of inflammatory activity. Fluorinated corticosteroids (e.g., triamcinolone) are rarely chosen for soft-tissue injection, because they are more likely to cause tissue atrophy. Prednisolone tebutate and methylprednisolone acetate are often used for soft-tissue injections because of their efficacy and cost.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
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