Regional Anesthesia and Pain Management Flashcards

A patient receives a large-volume peripheral nerve block for shoulder surgery. Shortly after the injection, the patient becomes agitated, reports tinnitus and a metallic taste, and then has a generalized tonic-clonic seizure. Of the following local anesthetics, which one is associated with the highest risk of severe cardiovascular collapse in this setting?

Answer: Bupivacaine

Bupivacaine is the most cardiotoxic of the commonly used long-acting amide local anesthetics. It has a high affinity for and slow dissociation from cardiac sodium channels, which can lead to severe, refractory arrhythmias and myocardial depression in the event of Local Anesthetic Systemic Toxicity (LAST). Ropivacaine, the S-enantiomer of bupivacaine, was developed to have a lower propensity for cardiotoxicity. [7, 10, 11, 21]

When performing an ultrasound-guided transversus abdominis plane (TAP) block via the lateral approach, the local anesthetic should be deposited in the fascial plane located between which two muscles?

Answer: Internal oblique and transversus abdominis

The correct plane for a TAP block is between the internal oblique and the transversus abdominis muscles. [20, 27, 29] This plane contains the thoracolumbar nerves (T6-L1) that provide sensory innervation to the anterolateral abdominal wall. Injecting into this specific interfascial plane allows the local anesthetic to spread and block these nerves.

Which of the following is considered the most significant modifiable risk factor for developing a post-dural puncture headache (PDPH) following a neuraxial procedure?

Answer: Use of a large-gauge, cutting-tip needle

While age, gender, and headache history are all risk factors, the type and size of the needle used are the most significant *modifiable* factors. [4, 9] Using a larger gauge (e.g., 22G vs 27G) and a cutting-tip (e.g., Quincke) needle creates a larger tear in the dura, leading to a higher rate of CSF leakage and a greater incidence of PDPH compared to smaller, pencil-point needles (e.g., Sprotte or Whitacre). [4, 9]

A 45-year-old patient with Complex Regional Pain Syndrome (CRPS) Type I of the left upper extremity reports burning pain, allodynia, and temperature changes. Which of the following interventional procedures is specifically targeted at modulating the sympathetic nervous system's contribution to these symptoms?

Answer: Stellate ganglion block

A stellate ganglion block involves injecting local anesthetic near the collection of sympathetic nerves (the stellate ganglion) in the neck. This procedure is used to diagnose and treat sympathetically mediated pain in the head, neck, and upper extremities, which is a key component of CRPS. [1, 2, 5, 6] The other options target different pain pathways or structures.

An anesthesiologist is performing an ultrasound-guided nerve block. They notice that the nerve, which initially appeared bright and distinct, becomes dark and difficult to see when the ultrasound probe is tilted slightly. What is the name of this ultrasound artifact?

Answer: Anisotropy

Anisotropy is the property of a tissue to exhibit different ultrasonic characteristics depending on the angle of insonation. [16, 19, 26, 28] Nerves and tendons are highly anisotropic, appearing brightest (hyperechoic) when the ultrasound beam is perpendicular to them and becoming dark (hypoechoic) as the angle deviates. Recognizing and correcting for anisotropy by tilting the probe is a fundamental skill in ultrasound-guided regional anesthesia.

A 72-year-old male on apixaban 5 mg twice daily for atrial fibrillation is scheduled for a total knee replacement. According to the 2018 ASRA guidelines, what is the minimum recommended interval between the last dose of apixaban and the performance of a deep peripheral nerve block, such as a lumbar plexus or popliteal sciatic block?

Answer: 72 hours

The 2018 ASRA guidelines recommend a conservative approach for direct oral anticoagulants (DOACs) before neuraxial or deep peripheral nerve blocks due to the risk of hematoma. For standard dose apixaban (5 mg BID), a waiting period of 72 hours is suggested to allow for sufficient clearance of the drug and normalization of coagulation. [22, 24] Shorter intervals may be considered for superficial blocks or if anti-Xa activity can be measured.