Ultrasound-Guided Pain management: Interscalene Blocks

Nerve blocks have gained widespread acceptance as tools for maximizing perioperative and chronic pain control while minimizing opioid consumption. Ultrasound-guided interscalene blocks present numerous benefits and opportunities for optimizing care in patients undergoing shoulder, upper arm, or elbow surgery. Read on to gain an overview of nerve blocks and learn how ultrasound guidance can greatly increase the benefits of interscalene blocks and other perioperative procedures.

Nerve blocks: A fundamental pillar in opioid-free anesthesia protocols

Setting the stage– The worst drug crisis in American history

Natural opiates have been an integral part of pain treatment strategies for millennia.¹ Although originally introduced in surgical anesthesiology as an adjunct, synergistic agent of volatile anesthetics in the nineteenth century,^{2, 3}  the use of synthetic opioids at high doses during surgery was not fully adopted until the 1960s.⁴  The late 1990s brought about a sharp increase in opioid prescriptions for perioperative pain control, followed by their widespread acceptance and use for the treatment of chronic pain.⁵

This flood of prescribed opioids, which continues to increase substantially every year,⁶  has led to a surge of addiction⁷ and a parallel, steady rise in overdose fatalities.⁸  Despite long-standing controversy regarding risk and long-term effectiveness,⁹  studies have definitely shown that opioids medications can lead to dependency within a matter of days,¹⁰ and ~25% of patients who receive long-term opioid therapy become addicted.^{11 12 13} Since 1999, more than half a million people have died from a drug overdose involving prescription and illicit opioids.⁸ With opioid-related overdose deaths reaching historic highs,¹⁴  the nationwide opioid addiction epidemic was declared a national emergency in 2017.¹⁵

For many patients with opioid use disorder, the perioperative period represents the initial exposure and an important source of unused prescription opioids.¹⁶  Modern approaches therefore seek to reduce opioid use in favor of multimodal pain management protocols.¹⁷  Nerve blocks have emerged as an attractive option in opioid-sparing analgesia strategies. As technological advancements improve on their accuracy, efficacy, and safety, the use of nerve blocks continues to expand, offering superior pain control in various surgical and pain management procedures.^{18 19}

What is a nerve block? 

Nerve blocks, or neural blockades, deliberately interrupt the transmission of signals traveling along a specific nerve or group of nerves to temporarily reduce or eliminate pain in specific parts of the body during and after surgery (e.g., procedural anesthesia and perioperative analgesia), as well as for the treatment of chronic, long-term pain.²⁰  These procedures offer immediate pain relief that can be temporary (hours) or long-lasting (months), depending on the medication and the technique used.

What types of nerve blocks are there?

Nerve blocks can consist of sympathetic blockades,²¹  where anesthetic agents are injected onto or near a nerve to block pain; or neuroablation,²²  involving the targeted destruction of a nerve or nerve plexus via chemical, thermal, or surgical methods.

Depending on their purpose, nerve blocks are grouped into 3 main categories:²³

• Therapeutic: used to treat chronic pain and various conditions or injuries involving damaged, inflamed, or irritated nerves. 
• Diagnostic: used to identify the source of pain.
• Prognostic: used to determine if a permanent solution like surgery would be a successful pain management strategy.

Interscalene blocks: Challenges and opportunities

Peripheral nerve blocks are now a common component of multimodal analgesia for upper²⁴ and lower²⁵ extremity surgical procedures. Interscalene blocks²⁶ target the brachial plexus, a network of nerves that innervate the shoulder and upper limb, to provide dense surgical anesthesia and/or perioperative analgesia for distal clavicle, shoulder, and proximal humerus procedures.

Ultrasound guidance of interscalene blocks lead to improved patient outcomes

Ultrasound imaging is increasingly used to guide peripheral nerve blocks, and presents numerous advantages compared to other traditional approaches. Ultrasound is a safe, portable, and easily accessible imaging modality that carries no risk of ionizing radiation. It enables real-time visualization of neural and surrounding structures, needle advancement, and local anesthetic spread to maximize success, reduce performance time, and minimize complications²⁷

Interscalene blocks are commonly performed under sterile conditions in the preoperative suite or postanesthesia care unit with the patient mildly sedated. Ultrasound guidance is used to correctly identify the brachial plexus roots within the interscalene groove, helping guide needle placement and avoid intravascular spaces. A nerve stimulator may also be used as an adjunct to confirm placement, causing muscle contractions in the appropriate muscle when the corresponding nerve is stimulated. Once the needle position is confirmed, a volume of local anesthetic is administered, and the needle is removed. The patient can expect pain relief and limb heaviness for the duration of local anesthetic action, typically 4–24 hours.

Benefits of ultrasound guidance in interscalene blocks:

• Faster onset time and longer duration, produces surgical anesthesia more reliably for the same volume of local anesthesia compared to nerve-stimulation²⁸ 
• Can decrease incidence of hemidiaphragmetic paresis²⁹
• Lower volumes of local anesthetic are needed for an effective block³⁰
• May reduce the risk of nerve injury³¹
• Inhibition of the nociceptive impulse may decrease the occurrence of muscle spasm following mobilization postoperatively, which may contribute to improved functional recovery³²

What are its limitations and risks?

Regardless of the technique or block location, nerve block risks include vascular puncture and bleeding, nerve damage, and local anesthetic systemic toxicity.

Interscalene blocks are generally safe. Common complications include:

• Bleeding or infection at the site
• Recurrent larungeal nerve blockage
• Allergic reaction
• Horner syndrome - a rare condition that causes disruption of nerve pathways from the brain to face and eyes
• Hematoma

Other rare but severe complications include:

• Permanent brain damage
• Bradycardia (slow heartbeat)
• Pneumothorax (collapsed lung)
• Severe hypotension (low blood pressure)
• Cartoid artery puncture

The ability to track the needle tip, assess local anesthetic spread, and maintain cautious approach to nerve roots and vascular structures that is afforded by ultrasound guidance are fundamental to reducing the risk of complications outlined such as nerve injury or local anesthetic toxicity outlined above.

Additional Resources

Learn more about ultrasound guidance and how it can greatly increase the benefits of interscalene blocks and other perioperative procedures at the Sonosite Institute for Point-of-Care Ultrasound, an in-depth educational resource provided exclusively to Sonosite customers where you can enhance your skill set, monitor your progress through each course, and earn certificates of completion.