• Knox H. Todd, MD

        INTRODUCTION

Emergency physicians are called on to provide care for a variety of emergent, urgent, and often complex conditions. Many patients present with pain as a component of their illness or require diagnostic and/or therapeutic interventions that are inherently painful to perform. As a result, the management of analgesia in the emergency department (ED) is a critical skill and an important element in the overall care of patients in this setting. This chapter is an overview of acute pain in the context of the ED as well as potential therapies, including regional anesthetic techniques for the emergency physician.

        OLIGOANALGESIA: PAIN AS A PROBLEM IN THE ED

Pain is the single most common reason patients seek care in the ED, and it accounts for up to 79% of visits.¹ Given the prevalence of pain as a presenting complaint, one might expect emergency physicians to assign its treatment a high priority. However, pain is seemingly invisible to providers of emergency medical care. Oligoanalgesia, a term coined by Wilson and Pendleton² in 1989, is the inadequate use of methods to relieve pain. Multiple studies in the emergency medicine literature have observed that oligoanalgesia is a common occurrence.³ Notwithstanding the issue of providing compassionate care, pain that is not acknowledged and managed appropriately causes anxiety, depression, sleep disturbances, increased oxygen demands with the potential for endorgan ischemia, and decreased movement with an increased risk of venous thrombosis.^4,5 Failure to recognize and treat pain may also result in dissatisfaction with medical care, hostility toward the physician, unscheduled returns to the ED, delayed full return to full function, and a potential increased risk of litigation.⁶

        Several studies have attempted to define the prevalence of pain and oligoanalgesia in ED settings. Johnston and coworkers⁷ investigated the incidence and severity of pain among patients presenting to noncritical treatment areas within the EDs of two urban hospitals in Canada. Fifty-eight percent of adults and 47% of children reported pain on ED arrival. Approximately 50% of these patients described the pain as moderate to severe. At the time of discharge, one third of both groups continued to report pain of moderate to severe intensity. In fact, 11 % of children and adults in this study actually reported clinically important increases in pain intensity during their stay in the ED.

        Another prospective study found that among adults treated at one Chicago ED, 78% presented with pain as a chief complaint.⁸ Fifty-eight percent of all patients received analgesics or nonpharmacologic intervention, but only 15% received opioids, despite high levels of pain intensity. Guru and Dubinsky⁴ found that 50% of patients who were treated for acutely painful conditions did not receive prescriptions for pain management at discharge. Another review of urban, university-based EDs reported that 69% of patients with painful conditions, including thermal burns, long-bone fractures, and vaso-occlusive crises, received no pain medication at all and that 55% were discharged with no analgesic prescription.¹⁰

        A study by Brown et al.¹¹ revealed that pain medications were frequently not part of ED treatment for fractures, even for visits with documented moderate or severe pain.

        Despite a tendency for undertreatment of pain in the ED, patients continue to expect analgesia. Fosnocht and coworkers¹² used a 100?mm visual analog-type scale (VAS) to gauge patient expectation of pain relief in the ED (0 mm = no relief; 100 mm = complete relief). Patients with pain reported a mean expectation for pain relief of 72%, with 18% of patients expecting complete relief of their pain. It is interesting that this value was seemingly independent of the initial pain severity, so that those with mild pain expected the same degree of relief as those with severe pain. Other studies have suggested that patient expectations are very influential on both the patient’s experience of pain and satisfaction with their care.^13,14

        Why is pain being undertreated in the ED? Several factors may play a role. Difficulty in accurately assessing pain is a well-known problem to providers of emergency medical care. Caregivers have been shown in several studies to underestimate pain scores when compared with those reported by the patients themselves.¹⁵ The assessment may also be hindered by the limitations of commonly used verbal scales. For example, Rupp and Delaney³ point out that asking a patient to describe his or her pain in relation to the “worst pain imaginable” obviously results in different answers, depending on the patient’s particular frame of reference. Other factors leading to oligoanalgesia may include apprehension about dependency when prescribing opioids (both on the part of the patient and the physician),¹⁶ concern regarding side effects such as respiratory depression,¹⁷ and the desire to withhold pain medication until informed consent for a procedure has been obtained, and concern about not obscuring a diagnosis (eg, an acute abdomen). Attitudes toward this last practice are changing, although slowly, because of mounting evidence that adequate analgesia in these situations allows patients to relax. This removes voluntary guarding as a confounding factor and allows for a more precise evaluation of localized sensitivity.^3,18–20

        Some patient groups are known to carry a higher risk for oligoanalgesia (Figure 68-1). For example, multiple studies have documented lower rates of analgesic administration for both young children and the elderly when compared with other patients in pain.^10,21,22 Kozlowski and colleagues²³ reported that in patients with isolated lower extremity injuries, those with fractures were twice as likely to receive pain medication as those without fractures, even when controlling for the severity of pain. Patient gender appears to be unimportant with respect to analgesia in the ED according to one prospective study.²⁴

Figure 68-1. Factors contributing to oligoanalgesia in the emergency department.

        Patient ethnicity is perhaps the best-studied risk factor for oligoanalgesia in the ED. In 1993, Todd and colleagues²⁵ examined the medical records of all patients with acute, isolated, long-bone fractures seen at the UCLA Emergency Medicine Center in 1991 and 1992. Hispanic patients in this study were twice as likely as non-Hispanic white patients to receive no pain medications during their ED stay (RR 2.1; 95% Cl 1.4-3.3). This relative risk for ethnicity remained significant after controlling for covariates related to patient (gender, language, and insurance coverage), injury (open versus closed fracture, admittance versus discharge, need for reduction), and physician characteristics (ethnicity, gender, specialty). After multiple logistic regression analyses, patient ethnicity remained the strongest predictor of ED analgesic administration. In a follow-up study performed at a large, community, university-affiliated ED in urban Atlanta, Todd and colleagues²⁶ found similar disparities in analgesic treatment between white and African-American patients with isolated long-bone fractures despite similar documentation of pain complaints.

        The solution to these disparities may involve more than simply addressing cultural biases, however. Research into the genomic basis of pain sensation is beginning to show that different individuals, as well as groups of individuals, process pain signals differently.²⁷ This may help guide providers of analgesia as to which individuals may be experiencing more intense pain for the same injury or illness. In addition, response to analgesics may also be attributable in part to gene expression, just as cytochrome P450 receptor differences determine a patient’s ability to utilize codeine.²⁸

        PAIN ASSESSMENT IN THE ED

Recognizing that pain is a major public health problem, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has placed a great deal of emphasis on the importance of pain management, in part by implementing standards that create new expectations for the assessment and management of pain²⁹ (Table 68-1). These standards have been endorsed by the American Pain Society.

        One of the key take-home points of the JCAHO recommendations focuses on the usefulness of standardized scales so that frequent reassessment of a patient’s pain can be progressively documented and treated. Indeed, many hospital EDs have begun to include pain as the “fifth vital sign,” to encourage frequent and standardized reassessment.

        Several pain assessment tools are available for use in the ED. One of the most common is the visual analog scale (VAS)—easy to use and convenient for statistical analysis. Patients are asked to make a mark on a horizontal line corresponding to the intensity of their pain (Figure 68-2). This scale is attractive for acute care settings in which short-term changes in VAS can be used to guide titration of analgesic therapy. Todd and coworkers³⁰ conducted serial interviews with patients reporting acute pain and concluded that a change of less than 13 mm in the VAS is clinically insignificant. Another similar tool is the numeric rating scale (NRS), which asks the patient to verbally rate the pain on a numerical scale—usually 1-10. Both the VAS and NRS have been shown to be reliable and valid tools for assessing acute pain.^31,32

Figure 68-2. Visual Analog Scale.

        Mandated reporting of pain scores has been shown to result in improved frequency of analgesic administration for ED patients presenting with acute pain.³³

        MONITORING DURING SEDATION & ANALGESIA

Opioids are the most frequently used analgesic for moderate- to-severe pain in the ED, but they carry a risk of dosedependent respiratory depression as well as sedation and hypotension. In addition to treating pain as a presenting complaint, emergency physicians are often called on to perform diagnostic or therapeutic procedures that are associated with a brief but intense amount of pain. In these cases, sedatives such as benzodiazepines, opioids, and other anesthetic drugs are sometimes used to facilitate an expeditious and painless procedure. As such, emergency physicians must be skilled at monitoring patients who are sedated and must be able to manage potential complications resulting from sedation such as the need for advanced airway management.³⁴ In 2005, the American College of Emergency Physicians (ACEP) updated their guidelines for procedural sedation and analgesia in the ED, replacing guidelines set out in 1998. The recommendations appear as a series of “critical questions.” Key elements are as follows:

1.  What are the personnel requirements needed to provide procedural sedation and analgesia in the ED?

    •  During moderate and deep sedation, a qualified support person should be present for continuous monitoring of the patient.

    •  Patient must be supervised by an emergency physician or other appropriately trained and credentialed specialist.

        The literature is unclear about the number of personnel required during light sedation in addition to the physician performing the procedure.

2.  Is preprocedural fasting necessary before initiating procedural sedation?

    •  Recent food intake is not a contraindication for administering procedural sedation and analgesia, but should be considered in choosing the timing and target level of sedation.

        This guideline is based on the assertion that the combination of vomiting and loss of airway protective reflexes is an extremely rare occurrence with procedural sedation and analgesia. The American Society of Anesthesiologists recommends a minimum fast of 2 hours for clear liquids and 6 hours for solids, but it should be noted that both groups base their recommendations on consensus opinion rather than firm evidence. It is prudent to weigh the risks of sedation versus delaying the procedure when considering this issue for nonfasted ED patients.

3.  What equipment and supplies are required to provide sedation and analgesia?

    •  Oxygen, suction, reversal agents, and advanced life support medications and equipment should be available.

        These items should include immediate access to a bag- valve-mask device, oral and nasal airways, laryngoscopes, and endotracheal tubes.

4.  How should respiratory status be assessed?

    •  Pulse oximetry should be used in patients at increased risk of developing hypoxemia, such as patients on high doses or multiple drugs are used and when patients with significant comorbidity.

    •  Consider capnography to provide additional information regarding early identification of hypoventilation.

        Pulse oximetry is a low-risk, high-yield intervention that is unobtrusive, is easy to apply, and does not cause patient discomfort. The guidelines recommend obtaining and documenting vital signs (heart rate, respiratory rate, blood pressure and pulse oximetry) before, during, and after procedural sedation, but do not specify a recommended time interval. Response to verbal stimuli is a valuable monitor that is useful during sedation to monitor depth and guide further drug administration.

        It is convenient to classify depth of sedation into three categories: sedation/analgesia (formerly conscious sedation), in which patients can respond purposefully to verbal and tactile stimuli; deep sedation, in which patients with depressed consciousness are not easily arousable and do not respond to stimuli in a purposeful manner; and general anesthesia, which is a medically controlled state of unconsciousness accompanied by a loss of protective airway reflexes.³³ In reality, sedation and anesthesia are part of the same continuum, and using escalating doses of any sedative drug can push a patient into the next “level.” The ACEP guidelines state that a key to minimizing complications is the titration of drugs to the desired effect. Because of familiarity with the pharmacokinetic properties of commonly used drugs such as midazolam and fentanyl, this is usually achieved without incident. There is some controversy regarding the use of more potent anesthetic drugs such as etomidate³⁶ and, in particular, propofol,³⁷ in the ED setting. The extremely rapid onset of action and potent cardiorespiratory depressant effects of propofol have led some emergency physicians to caution against its widespread use in the ED,³⁸ citing studies showing an inability of physicians in the ED to avoid overshooting their sedation target when using the drug.³⁹ On the other hand, there is a growing body of evidence that propofol can be used safely by ED physicians for procedural sedation; it is likely that it will continue to gain popularity for this role.^40,41

        PHARMACOLOGIC STRATEGIES FOR ACUTE PAIN

Although many analgesic drugs are available to the emergency physician, it is important to tailor a pharmacologic regimen to each patient. For mild pain, simple analgesics often are all that is required. In contrast, moderate or severe pain may demand a more multifaceted approach to analgesia. We now know that pain is an extremely complex process involving many different classes of mediators and receptors. For this reason, the concept of multimodal analgesia is a crucial one in pain medicine. Multimodal analgesia is the combining of different classes of drugs to improve pain relief while minimizing the potential for side effects due to reduced reliance on one agent.⁴²

Acetaminophen

Acetaminophen has analgesic and antipyretic, but no antiinflammatory, properties. Its mechanism is unclear, but acetaminophen probably works via inhibiting prostaglandin synthesis. It is a good analgesic for mild to moderate pain, especially pain due to osteoarthritis, musculoskeletal pain, headache, earache, and dysmenorrhea. It is frequently used in combination with nonsteroidal antiinflammatories (NSAIDs) or opioids. The most serious adverse effect is hep- atotoxicity, which is rarely seen except in the case of an overdose far exceeding the daily recommended limits. Because of its long safety record and low incidence of adverse effects, acetaminophen is the most frequently used analgesic in North America and is often the base on which to build multimodal analgesia.

NSAIDs

“Nonsteroidals” are also very common in the management of acute pain. In addition to analgesic and antipyretic properties, these drugs are antiinflammatories and function by inhibiting cyclooxygenase (COX), an enzyme responsible for prostaglandin synthesis. This property renders NSAIDs useful for treating inflammatory and prostaglandin-related pain such as rheumatoid arthritis and dysmenorrhea, as well as renal and biliary colic, headache, and musculoskeletal injuries. The inhibition of COX is also responsible for its side-effect profile, which includes nephrotoxicity via decreased renal perfusion and an increased risk of gastroduodenal ulcer formation. These side effects are dose-dependent and are more likely to occur in the elderly and those with preexisting renal or peptic ulcer disease.⁴³ Other adverse effects include hypersensitivity, platelet dysfunction, and asthmatic exacerbation in sensitive individuals.⁴⁴

        There are many NSAIDs to choose from, and they appear to be relatively interchangeable as a class. In other words, with the correct dosing, ibuprofen is as effective as indomethacin or diclofenac. Ketorolac is unique in that it may be used parenterally, thereby ensuring a rapid onset, which is an attractive attribute in the ED. Ketorolac has been used favorably in emergency medicine for various types of acute pain.⁴⁵ The COX-2 inhibitor class of NSAIDs have not been adequately studied in the ED setting.⁴² This class of drugs has recently been associated with adverse cardiovascular outcomes in major clinical trials, and two of the major COX-2 inhibitors have been voluntarily withdrawn from the market pending further investigation.

Opioids

Intravenous opioids, titrated to effect, are the treatment of choice for patients with moderate-to-severe, acute pain in the ED.⁴⁶ Morphine is the standard against which most analgesic interventions are compared, although emergency physicians are using an increasingly wide spectrum of opioids, such as fentanyl and sufentanil, for their rapid onset and limited duration of action during procedural sedation and analgesia.⁴⁷ Other commonly used parenteral opioids are meperidine and hydromorphone, although use of the former is declining owing to its neurotoxic and anticholinergic side effects. Oral opioids such as codeine and oxycodone are a popular choice when prescribing discharge medications for moderate pain, especially in combination with acetaminophen or NSAIDs. Major side effects common to all opioids include dose-dependent respiratory depression, nausea, constipation, pruritus, and urinary retention. Owing to concerns about serious adverse effects as well as fear of punitive action by regulatory agencies, many physicians suffer from “opiophobia,” and underprescribe this potent and effective class of analgesics.³

Other Adjuvants

Many other nontraditional strategies have been used in the perioperative period to reduce the duration and severity of postoperative pain. Few of these have been applied to the acute pain setting in the ED. One example of a drug that has been used is ketamine, an NMDA (N-methyl-D-aspartate)- receptor antagonist that has a unique dissociative-anesthetic effect and is known for having potent analgesic properties. Ketamine is occasionally used for procedural sedation in children.⁴⁸ Inhaled nitrous oxide has both sedative and analgesic properties, but its popularity for use in the ED has waxed and waned over the years.⁴⁹ Other pharmacologic adjuvants that have promise in other areas of pain management but are infrequently used in the ED are clonidine, dexmedetomidine, gabapentin, neostigmine, and magnesium.

Combination or Multimodal Analgesia

Combining two or more drugs of different classes has been shown to reduce the side-effect profile of each and particularly for opioids, an effect termed “opioid-sparing.”

        For example, ketorolac plus morphine allows for less morphine use and a reduction in opioid-related side effects for postoperative pain.⁵⁰ Acetaminophen plus oxycodone provides more superior analgesia than controlled-release oxycodone after oral surgery.⁵¹ After adenoidectomy, children who received ibuprofen plus acetaminophen required less analgesia at home than those who received either drug alone.⁵² Techniques that aim at opioid sparing have been shown to reduce time to discharge from the ED and improve patient satisfaction.

        Although most of this research has been carried out in the perioperative setting, much of it is applicable to acute pain in the ED, despite barriers to adequate pain management, such as crowding and lack of continuity of care. Other techniques used by anesthesiologists that have potential applications for acute pain in the ED are aggressive titration protocols, continuous infusion pumps, and patient-controlled analgesia.⁵³

        LOCAL & REGIONAL ANESTHETIC TECHNIQUES IN THE ED

Whereas many pain relievers work by altering the transmission, perception or modulation of pain impulses at the spinal or brain level, local anesthetics primarily exert their effect by blocking axonal transmission in peripheral nerves, thereby preventing nociceptive signals from reaching the central nervous system. By stopping the pain impulses before they arrive at the dorsal horn of the spinal cord, regional anesthetic techniques reduce the degree of central sensitization, or “windup,” and allow for high-quality pain relief with minimal side effects.

        Regional and local anesthesia is particularly well suited to the ED, where many patients present with acute, localized painful injuries that are amenable to a short-term, selective peripheral blockade.

Topical Anesthetics

Topical anesthesia involves the application of local anesthetic directly to a mucosal or skin surface. It has the advantage of a needle-less technique, and many small lacerations and injuries can be effectively anesthetized by the application of these agents. Several studies have shown that the application of a topical local anesthetic mixture significantly reduced the severity of pain on injection and the time to discharge in patients with simple lacerations required suturing.^54,55

        For mucous membranes, lidocaine 1-4% provides adequate anesthesia after topical application and can be administered several different ways. Viscous jelly can be swished around the mouth; lidocaine can be nebulized for anesthesia of the oropharynx and airway; pledgets can be soaked and then applied directly to a mucosal area. Care must be taken when using local anesthetics on mucosal surfaces because uptake is rapid, especially when higher concentrations are used (eg, 4% lidocaine). Safe dosages should.be calculated in advance and adhered to.

        For intact skin, the most common form of topical anesthesia is eutectic mixture of local anesthesia (EMLA). EMLA cream is a 1:1 mixture of 2.5% lidocaine and 2.5% prilocaine and has been well established as a means to decrease pain from venipuncture and intravenous cannulation in children.⁵⁶ It is usually applied to skin, then covered with a barrier dressing while waiting for its anesthetic effect. Adverse effects are minimal, although cases of methemoglobinemia have been reported secondary to prilocaine toxicity.⁵⁷ One disadvantage with EMLA is the duration of application required for effective local anesthesia, usually between 45 and 60 minutes. EMLA has also been used for minor procedures such as infant penile circumcision.⁵⁸

        ELA-Max is a relatively new product that contains 4% lidocaine cream in a liposomal matrix. It is applied to the skin in a manner similar to that of EMLA and has been shown to be as effective as EMLA but with a faster onset of action (30 minutes versus 60 minutes).⁵⁹ Other methods of topical anesthesia for intact skin include the delivery of lidocaine by iontophoresis⁶⁰ and the use of jet injectors.⁶¹ Both have been used in the ED with success.

        Nonintact skin can be effectively anesthetized by the application of a liquid mixture of local anesthetic and vasoconstrictor. Examples include TAC (tetracaine 0.5%, adrenaline 0.05%, and cocaine 11.8%), LET (lidocaine 4%, epinephrine 0. 1%, and tetracaine 0.5%), and MAC (marcaine, adrenaline, and cocaine).^62,63 The mixture is applied to the wound and covered with moist gauze. Adequate anesthesia usually results after 25-30 minutes.

Local Infiltration

Injecting local anesthetics subcutaneously can result in sufficient anesthesia to allow for minor superficial procedures, such as suturing of wounds. Because anticipation of a needle stick is often emotionally traumatic for patients, especially children, the use of techniques to lessen the pain on injection is always appreciated. These include the use of small needles (ie, 27- to 30-gauge), slow administration of the anesthetic ( 1 mL over 30 seconds), and the buffering of local anesthetic by sodium bicarbonate.^64,65 Bartfield and colleagues⁶⁶ studied pain on injection at wound sites and found that local anesthesia is less painful when injected from within a laceration than through intact skin. Vasoconstrictors such as epinephrine added to local anesthetic increase the duration of the anesthesia (by decreasing local uptake) and provide better hemostasis at the wound site. Vasoconstrictors should not be used on the ear, nose, penis, fingers, or toes because ischemia and tissue necrosis may result.

Intravenous Regional Anesthesia or Bier’s Block

Intravenous regional anesthesia (IVRA) was first performed in 1908 by Karl August Bier, and the procedure has changed little since that time.⁶⁷ It has been shown to have an excellent safety record, to provide effective anesthesia of the isolated limb, and to be easy to perform.⁶⁸ The method for establishing the block is described elsewhere but essentially involves exsanguinating a limb using a compressive device, inflating a double tourniquet on the proximal end of the limb, then injecting local anesthetic intravenously into the isolated limb. The local anesthetic spreads throughout the venous channels of the arm or leg, diffusing out to act on both the free nerve endings in the tissues and the larger peripheral nerve branches. It is a popular form of anesthesia for reducing fractures in the ED, especially in children.⁶⁹ Complications are rare with IVRA but are usually caused by inappropriate management of the double cuff, leading to “washout” of local anesthetic into the central circulation and subsequent toxicity. Most authors recommend a minimum tourniquet time of 20-30 minutes before deflating, regardless of the duration of the procedure. Some also advocate a staged tourniquet deflation to allow for partial washout in an attempt to lower peak blood local anesthetic concentrations.

        The most common agent for IVRA is lidocaine, but other local anesthetics such as prilocaine have been used. Bupivacaine has fallen out of favor owing to the unnecessary risk of systemic toxicity. Some practitioners add narcotics or other adjuvants to the mixture such as ketorolac, tramadol, or clonidine. The traditional preparation is a high-volume, dilute concentration of lidocaine (eg, 40 mL of 0.5% for an upper arm tourniquet), but good results can be achieved with a low-volume, high-concentration technique (eg, 12-15 mL of 2% lidocaine). Onset of either is usually less than 5 minutes for full anesthesia.

Peripheral Nerve Blocks

In general, blocks of peripheral nerves have several advantages over local infiltration.⁷⁰ They are often less painful to perform and may cause less anxiety for the patient, especially when the procedure involves sensitive areas such as the palm or sole. Tissue distortion of the wound is usually avoided. Also, depending on the area, less local anesthetic may be required, reducing the risk of systemic toxicity. Compared with parenteral or oral analgesics, nerve blocks have been shown to provide superior analgesia and greater patient satisfaction for treatment of pain associated with femoral neck or shaft fractures.⁷¹

        Peripheral nerve blocks require some degree of specialized training but, with practice, can be implemented in the ED setting to great effect. Nerve blockade is often performed in the ED as a blind technique or one in which paresthesias are sought as confirmation of correct needle placement.⁷⁰ Nerve stimulation as a means of locating peripheral nerves has been slow to catch on in the ED setting, despite its almost universal use among anesthesiologists. This may be due in part to lack of experience with the nerve stimulators, and unfamiliarity with the technique. However, it has been shown to be both easy to learn and effective when performed by emergency physicians.⁷²

        Ultrasound-guided nerve blockade is a relatively new trend that is showing promise as a way to improve accuracy and block success.⁷³ This technique may be particularly attractive to emergency physicians, because most have experience in both performing ultrasound exams and using ultrasound for placement of intravenous lines.

        Regardless of the technique used, there is evidence that peripheral nerve blocks in the ED are underused as a means of acute pain management.⁷⁴ Emergency physicians should have an armamentarium of nerve blocks that can be used for the relief of acute pain in the ED. Finally, nerve blocks require proper patient education before the block is performed.

        Some blocks can be associated with some degree of discomfort (eg, ankle block). Adequate pre-block analgesia improves patient cooperation and ultimately satisfaction. The following is a brief overview of peripheral nerve blocks that are commonly performed in the ED setting. For a complete description of individual techniques, please refer to the respective chapter.

Digital Blocks

Digital blocks of the fingers and toes are more comfortable and easier to perform than local infiltration. Four nerves enter each digit—two on the volar aspect and two on the dorsal aspect—approximately at the 2,4,8, and 10 o’clock positions. The most consistent method for anesthetizing the finger or toe is to insert a fine-gauge (ie, 27-gauge) needle into the dorsal web space, just lateral to the bone. After raising a subcutaneous wheal with 0.5-1 mL of local anesthetic, the needle is advanced toward the palm or sole until it is just past the bone on the volar side. After negative aspiration, a further 1—1.5 mL is injected. Then the procedure is repeated on the other side of the digit. In this manner, all four nerves are blocked. Epinephrine-containing solutions should never be used in digital blocks as ischemia and necrosis may result.

Wrist Blocks

These blocks are appropriate for minor procedures on the palm or dorsum of the hand, or on the fingers when more than one digit is involved. The technique involves blocking the terminal branches of the median, ulnar, and radial nerves or any appropriate combination of these nerves, depending on the anatomic location of the injury. Most practitioners use a blind technique based on the relatively consistent location of these nerves at the wrist,⁷⁵ but they can also be performed using a nerve stimulator technique.⁷⁶ Wrist blocks are safe and easy to perform, but they require a good working knowledge of the anatomy of the hand and wrist.

Ankle Blocks

Ankle blocks are similar to wrist blocks to the extent that it is a blockade of the terminal branches of several peripheral nerves just before entering the foot. This block is suitable for relieving pain and/or performing procedures anywhere on the foot. Like the wrist block, selective blockade of individual peripheral nerves can be performed (eg, posterior tibial nerve block for suturing a sole laceration). On the other hand, blocking all five nerves (posterior tibial, sural, saphenous, and superficial and deep peroneal) provides complete anesthesia of the foot below the ankle. Some practitioners advocate five separate injections, whereas others recommend a three-puncture technique. The latter approach is carried out by first performing separate posterior tibial and sural blocks behind the medial and lateral malleoli, respectively, then using a single puncture site just lateral to the extensor hallucis longus tendon. With this maneuver, the deep peroneal nerve is blocked, followed by withdrawing the needle to just below the skin and redirecting both laterally and medially while depositing local anesthetic in a subcutaneous wheal to block the saphenous and superficial peroneal nerves. Ankle blocks are extremely useful but are somewhat uncomfortable and therefore require a moderate degree of sedation and analgesia.

Femoral Nerve Blocks

The femoral nerve block has been used for many years in the ED for treatment of pain associated with fractures of the femoral shaft or neck. It is also useful for pain associated with patellar and patellar tendon injuries as well as superficial injuries to the anterior thigh. This block confers anesthesia to the entire anterior thigh and most of the femur and knee joint. Because the saphenous nerve is a superficial sensory branch of the femoral nerve that extends along the medial aspect of the lower leg, anesthesia of this area is also achieved. The popularity of the femoral nerve block in the ED is probably due to its reliability and ease of performance. The femoral nerve is a superficial nerve at the level of the inguinal crease, and its reliable position next to the femoral vessels makes it easy to locate.⁷⁷ The block is often performed using a “double pop” technique, which corresponds to the penetration of both the fascia lata and the fascia iliaca layers, under which the femoral nerve resides. The clinician should feel two clicks or pops as the needle, preferably with a noncutting tip, passes through these fascial sheets.

        Alternatively, paresthesia may be sought in the femoral nerve distribution. Proximity to the femoral nerve with a nerve stimulator and stimulating needle results in quadriceps twitches and a jerking of the patella. Usually, 15-20 mL of local anesthetic are enough to provide quality anesthesia. Winnie and coworkers⁷⁸ described the 3-in-l block in 1973, which was designed to augment femoral nerve anesthesia with simultaneous blockade of the lateral femoral cutaneous nerve and the obturator nerve. The technique is performed by applying pressure to the femoral sheath just distal to the injection point and using a relatively high volume of local anesthetic, thereby forcing a proximal migration of the solution. The usefulness of the 3-in-l block has been questioned, because the blockade of the other two components is unreliable, probably owing to fascial septa in the femoral sheath.⁷⁹ Another approach, called a fascia iliaca block, involves a needle insertion site several centimeters lateral to the femoral nerve, thereby reducing concerns about vascular or nerve injury.⁸⁰ The distribution of anesthesia is similar to that of femoral nerve block. Overall, the complication rate is low for femoral nerve block. Some anecdotal reports of femoral nerve blockade masking the symptoms of a compartment syndrome of the thigh have been investigated and found to be lacking in evidence.⁸¹

Intercostal Nerve Blocks

The intercostal nerve block is most commonly used in the ED to provide analgesia for patients with broken or contused ribs. In this population, it has been shown to provide excellent analgesia for most rib fractures, but also to improve respiratory mechanics (as measured by peak expiratory flow rate) and arterial oxygen saturation.⁸² It should not be performed in patients with flail chest. Pneumothorax is the primary concern when performing this block, and it occurs in approximately 1.4% of nerves blocked.⁸³ This incidence increases in patients with obstructive lung disease. The block anesthetizes only the anterior and lateral chest wall because it is usually performed distal to where the posterior cutaneous diverges from the main intercostal nerve.

        The safest location to perform the intercostal nerve block is at the posterior axillary line, because it is here that the internal intercostal muscle lies between the nerve and the pleura. The ribs are used as landmarks, and a mobile needle is carefully walked off the inferior edge where the neurovascular bundle lies in the costal groove. Proper stabilization of the hands on the posterior chest wall is important to prevent inadvertent slipping of the needle into the intrapleural. After advancing 1-2 mm past the edge of the rib, the clinician aspirates to check for blood or air, and then injects 3-5 mL of local anesthetic slowly. Care must be taken with local anesthetic dosing because systemic uptake is high, owing to the close presence of the intercostal vessels. After 30 minutes, if no clinical signs of pneumothorax are present, the patient may be discharged with advice to return if dyspnea or chest pain appears.⁷⁰

Axillary Brachial Plexus Blocks

The brachial plexus is formed by the union of spinal roots C5 to Tl. These pass under the clavicle and through the axilla to form the peripheral branches of the nerves supplying the upper limb, namely, the musculocutaneous, radial, ulnar, and median nerves (as well as several smaller nerves). Although there are many approaches to the brachial plexus used in clinical anesthesia, such as the interscalene, supraclavicular, and infraclavicular, few emergency physicians have the level of comfort performing these without supplemental training.

        In contrast, the axillary approach is a favorable one for regional anesthesia novices owing to the presence of good landmarks, the close bundling of the nerves in a neurovascular sheath, and the low incidence of serious complications. The axillary arterial pulse is used as the primary landmark for all approaches, whether for seeking paresthesia, using a nerve stimulator, or performing a transarterial technique. The latter approach may in fact be the easiest because it requires no extra equipment apart form a 23-gauge needle and a small length of IV tubing attached to the local anesthetic syringe. With the nondominant hand palpating the axillary pulse, the needle is passed through the skin and into the axillary artery, which is evidenced by the return of bright red blood through the IV tubing. The needle is slowly advanced until the aspiration of blood ceases, which corresponds to the passage of the needle through the back wall of the artery. At this point, the needle tip should be within the fascial sheath that contains the radial, ulnar, and median nerves. After negative aspiration, the local anesthetic is injected. Some clinicians deposit local anesthetic in front of the artery as well after withdrawing back through the vessel. This block provides dense anesthesia of the forearm and hand and is useful for treating pain associated with fractures and deeper wounds of those areas. Note that the musculocutaneous nerve has already left the sheath at this point and, if desired, requires a separate blockade by injecting 5-10 mL of local anesthetic into the belly of the coracobrachialis muscle.

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. Preemptive Analgesia, Regional Anesthesia, & the Prevention of Chronic Postoperative Pain. Newer Amide Anesthetics & Sustained-Release Local Anesthetics1. Diagnosis & Management of Intraspinal, Epidural, & Peripheral Nerve Hematoma. Histology of Peripheral Nerves. Supraclavicular Brachial Plexus Block.