Reviewing various management and prevention strategies for the procedure.
A 73-year-old female presents to the Emergency Department (ED) with acute right sided hip pain after a fall at home. She states that she was walking down her staircase and tripped over the last step, landing on her right side. She was unable to bear weight after her fall and reports bruising and discoloration over the injury site. On exam, she is in significant discomfort with stable vital signs. Her right leg is shortened, externally rotated and there is tenderness to palpation of the right hip. Radiography reveals a right sided intertrochanteric hip fracture.
Over a century ago in August of 1898, Dr. August Bier performed the first successful spinal anesthetization in Germany by injecting 15 mg of cocaine intrathecally in a patient undergoing resection of a tuberculous ankle joint. 
Eighty years later, ultrasound was used to successfully localize the subclavian artery during a supraclavicular brachial plexus nerve block.  Since then, these interventions have become widely utilized in surgery and are increasingly utilized in Emergency Medicine. Their primary benefits are pain-control and to decrease the use of opiates and other analgesic medications, thus avoiding their adverse effects.
Procedures involving regional anesthesia, often referred to as a ‘nerve block,’ are generally safe, but are not completely without complications or risk. Fortunately, serious adverse events are rare although when they do occur, they can be devastating. There are obvious advantages to using ultrasound guided nerve blocks in the ED beyond just pain control, including, real time visualization of the needle, the neurovascular structures and decreased complications.
Regional anesthesia in the ED has been shown to reduce or eliminate prolonged opioid use.  Common uses of regional anesthesia in the ED include laceration repair and other soft tissue injuries, dislocations and fractures. Proximal extremity blocks, like brachial plexus blocks, are less common due to their more complex anatomy and technical difficulty. Potential acute complications of performing regional anesthesia in the ED include local and systemic toxicity, peripheral nerve injury, vascular puncture, hematoma, pneumothorax and infections.
Local Anesthetic Systemic Toxicity
Local Anesthetic Systemic Toxicity (LAST) refers to accidental administration of supratherapeutic doses of local anesthetics during surgery or other procedures. This complication is rare and typically occurs within minutes of injection and should be considered in any patient with cardiac arrest that presents from a surgical center. 
LAST typically occurs when the local anesthetic is erroneously injected into systemic circulation, but can also be the result of using excessive volume of the anesthetic and exceeding the maximum weight-based dose.  The most common presentations of local anesthetic systemic toxicity are manifested through disruption of the central nervous system. The earliest signs of toxicity may present as numbness of the tongue, lightheadedness, visual and audio disturbances, muscle twitching. As serum concentrations increase patients can exhibit more life-threatening symptoms such as convulsions, respiratory and cardiac arrest. 
Since local anesthetic agents are all sodium channel blockers, the cardiac system is involved during toxicity, commonly presenting early with hypertension and tachycardia, and later with profound hypotension, conduction defects, ventricular dysrhythmias and cardiac arrest.
With lidocaine toxicity, neurological symptoms will usually precede the cardiovascular symptoms and cardiovascular symptoms typically precede neurologic symptoms in bupivacaine toxicity. Benzocaine toxicity may also present with methemoglobinemia.
Risk factors include the location of injection, medication dose and drug formulation. To decrease the likelihood of this complication, it is important to be aware of the max dose for the local anesthetic agents commonly used in the ED (Table 1). [5,19] It is also imperative that you aspirate the syringe prior to injection to ensure the drug is not administered into a blood vessel and monitor the patient for onset of any worrisome symptoms. The use of Epinephrine in conjunction with the local anesthetic (i.e. lido + epi) decreases the likelihood of systemic toxicity and allows for a larger dose to be used. This is due to the vasoconstrictive properties of the Epinephrine, which “trap” the anesthetic more locally.
If anesthetic toxicity is suspected, stop administration of the agent and place the patient on continuous cardiac monitoring and obtain IV access if not already established. Do not wait for hemodynamic instability to intervene. 
Other interventions include using 100% FiO2 and hyperventilating for worsening hypercapnia, seizure management with benzodiazepines, epinephrine to improve cardiac output in cardiovascular collapse. Lipid Emulsion Therapy (Intralipid) has been shown to be effective for LAST and should be given if the patient is hemodynamically compromised.
Intralipid can be given as a bolus of 1-1.5ml/kg over one minute and repeated every three minutes to a total of 3.0 ml/kg or as an infusion of 0.25 ml/kg/min.  Due to the superior visualization of the target region, an ultrasound guided approach to nerve blocks has been shown to reduce the risk of developing LAST. 
|Anesthetic||Max dose (w/o Epi)||Max dose (w/ Epi)||Duration of Action|
|Lidocaine (1%)||5mk/kg||7mg/kg||30-90 minutes|
|Bupivacaine (0.5%)||2.5mg/kg||3mg/kg||6-8 hours|
|Ropivacaine (0.75%)||3mg/kg||4mg/kg||120-240 minutes|
|Mepivacaine (3%)||7mg/kg||8mg/kg||45-90 minutes|
Table 1: Common local anesthetic agents used in the Emergency Department and their maximum doses.
Iatrogenic Nerve Injury
Regional anesthesia induced nerve injury can range from minimal change in function to permanent sensory and motor dysfunction. Transient nerve injuries have an estimated incidence of 0-2.2% at 3 months with a decreasing incidence of 0-0.2% at one year. Precise incidence data for permanent peripheral nerve injury is more difficult to ascertain, but studies put the incidence in a range of 0.014-0.04%.
Hemidiaphragmatic paresis is a rare, but serious, complication that can occur with regional anesthesia near the phrenic nerve. This is typically seen secondary to an interscalene or supraclavicular brachial plexus block. This complication can present as significant dyspnea in the patient. However, in many cases hemidiaphragmatic paresis is transient, asymptomatic and requires no treatment. In cases where significant dyspnea is present, surgical plication or transient ventilatory support should be considered.  The clinical situation in which nerve injury is most likely to occur is through anatomically confined regions such as near the ulnar nerve at the relatively noncompliant Cubital Tunnel.
Prolonged or excessive use of tourniquet can result in diminished blood flow, ischemia and subsequent nerve injury. Similarly, the use of epinephrine in the Emergency Department alongside regional anesthesia for nerve blocks can result in increased risk of nerve injury due to reduced blood flow to site. 
Common signs and symptoms of nerve injury include numbness, tingling and potential excessive sensitivity to touch. It will likely not be possible to differentiate iatrogenic nerve injury from successful anesthesia in the Emergency Department as the sensory manifestations of nerve injury are also consistent with a successful nerve blockade. Other symptoms such as pain may not present until the effects of the anesthetic have receded.
Understanding the duration of action of the anesthetic used is important to assess for nerve injury. Paresthesias that persist longer than the standard duration of action should raise suspicion. Pure sensory deficits may take days to weeks to resolve, whereas motor deficits are typically a more ominous sign. Nerve conduction studies and Electromyography (EMG) can be used to confirm the diagnosis in consultation with neurology, but are typically delayed three- to five-weeks to allow for signs of Wallerian degeneration to appear.  It is also important to consider compressive causes of nerve injury (i.e. expanding hematoma) as these may require surgical consultation.
Management of peripheral nerve injury is guided by clinical severity. If only mild sensory deficit is present, then reassurance and four-week follow up is sufficient. If symptoms persist after four weeks, there is motor involvement present, or complete nerve function loss then early neurology consult, and radiological testing is recommended. There is currently no evidence that has demonstrated effective pharmacologic enhancement of neurodegeneration.
This limits management to physical therapy and analgesia with the goal of preventing muscle atrophy and flexion contractures. Needle type used during the procedure is also important in preventing injury. It has been demonstrated that blunt needles (short bevel) are less likely to enter vital structures than sharp needles (long bevel) and may be preferable for performing interventional pain procedures. With the use of a short beveled blunt needle “b” instead of a long sharp (12-15 degree) needle there is decreased risk of entering the perineurium region of the nerve and increased resistance which enhances the feel of the needle traversing different tissues. 
Vascular injury is possible when performing regional anesthesia and it can result in ischemia of local tissue and/or the nerves. This can occur via direct vascular puncture or hemorrhage within the nerve sheath due to damage of the epineural vessels. Ischemia can also occur secondary to compressive insults like a tourniquet, forceful injection, or mechanical compression of a hematoma.  Epinephrine’s role in contributing to nerve ischemia secondary to vasoconstriction is controversial. This complication is best prevented by using the ultrasound-guided technique for direct visualization of vascular structures.
Some nerve blocks occur in “noncompressible” sites due to the relative constricting nature of the involved anatomy (i.e. supraclavicular and infraclavicular brachial plexus blocks). In patients on anticoagulation therapy or with coagulopathy, regional nerve blocks in noncompressible sites should be avoided and a more superficial approach should be considered. .
This is due to the increased risk of bleeding and decreased ability to externally compress the site of vascular insult. The lowest effective dose of local anesthetic should be used at these noncompressible sites as internal compressive ischemia can occur due to the consolidated and noncompliant anatomy “trapping” a large volume of anesthetic.
Pneumothorax is a known complication of some regional nerve blocks. This is more commonly seen following interscalene or supraclavicular nerve blocks, which may be used in patients for shoulder or upper extremity surgery. This will present as repeated coughing during the procedure and/or dyspnea, so it is important to also consider hemidiaphragmatic paresis on your differential with this presentation.
This complication is rare, with a reported incidence of 0.06% following infraclavicular and supraclavicular blocks in one study (11). In this same study, it was reported that the incidence was higher in cases where the procedure was performed by an inexperienced provider (i.e. a resident or <20 total blocks performed). The use of ultrasound reduces the risk of pneumothorax (11).
A patient suspected of an iatrogenic pneumothorax with stable vital signs should undergo confirmatory imaging to evaluate the size. This is traditionally done with a chest X-ray, but can also be done at the bedside with ultrasound. This may be more convenient as the provider will likely have the US nearby as part of the procedure. All of these patients should be placed on 100% high-flow oxygen via a non-rebreather mask.
A hemodynamically stable patient with a small pneumothorax may be observed in the ED for three- to six-hours and discharged home if a repeat radiograph shows a non-progressing pneumothorax.  If hemodynamically unstable, the patient should undergo prompt needle decompression followed by chest tube insertion and admission to the hospital. 
Post Dural Puncture Headache
One of the most common side effects that patients experience upon receiving neuraxial blocks is a post dural puncture headache (PDPH). As high as 7% of individuals may report symptoms pertaining to this complication after completion of receiving an anesthetic block. In the setting of the Emergency Department, however, this complication will most commonly be seen acutely following a lumbar puncture procedure. The pathophysiology, risk factors and management remain the same.
This complication is thought to be due to prolonged leaking of CSF through the dura and the most common presentation is a positional headache that worsens when the patient stands or sits and is mildly alleviated when supine. This typically presents clinically as a bilateral fronto-occipital throbbing headache that extends through the neck and shoulders in the first 48- to 72-hours following the procedure. It is important to inquire whether a patient presenting with an acute headache to the ED has had any recent spinal instrumentation. PDPH has been reported alongside symptoms of hypoacusis, tinnitus and neck stiffness, vomiting, photophobia and often subsides in the supine position.
This clinical syndrome typically occurs within five days after receiving anesthesia and can resolve spontaneously within one week. Risk factors include female and young age, causing pregnant women to be at a heightened risk, due to a decrease in dural elasticity. Conservative management for this involves hydration, bed rest, analgesics, caffeine and abdominal binders. Goal of management here is to increase CSF production, decrease downward traction, constrict intracranial vessels and symptomatic relief. Use of an epidural blood patch is a more invasive form of management, but is considered to be the most effective.
Infection is a potential, but rare, complication of peripheral nerve blocks. This typically manifests as superficial soft tissue infection or abscess. Cases of osteomyelitis and necrotizing fasciitis have been reported in the literature following peripheral nerve blockade.  One study reported the incidence of infectious complications of peripheral nerve blocks was 1.3%, and 2.7% for neuraxial techniques.  However, the incidence may be even more remote. One retrospective study looked at over 7,000 patients at a Toronto hospital who received a single injection peripheral nerve block from 2003 to 2013 and did not find a single case of block-related infection.
Current recommendations for infection control during peripheral nerve blocks include 2% chlorhexidine in 70% alcohol skin prep, sterile drape and sterile gloves.  With the increasing use of real-time ultrasound guided techniques in the ED, it is important that the US probe and cable are covered with a sterile sheath with sterile gel used within the sheath.  Nerve blocks should be avoided if there is evidence of overlying skin infection at the injection site. 
The patient was initially treated with IV pain medication in the ED and Orthopedic Surgery was consulted. An ultrasound-guided fascia iliaca block was performed as the patient continued to endure significant pain.
After calculating the appropriate dose for her weight, a mix of 15ml of 1% lidocaine and 20ml sterile 0.9% normal saline was injected into the fascial compartment without complication. Twenty five minutes following the procedure, the patient reported resolution of pain. The patient was scheduled for operative fixation of the fracture the following day and did not require any additional pain medication between the fascia iliaca block and her operation.
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