Interscalene Block - An Overview

What Is Interscalene Block?

An interscalene nerve block is performed when a local anesthetic is injected around the roots and trunks of the brachial plexus, which lies at the level above the C6 vertebral body and is located in the space between both the anterior and middle scalene muscles. During shoulder and upper arm surgery, an interscalene nerve block is frequently done to offer either anesthesia or analgesia to the patient.

What Is the Clinical Importance of the Nerve Block?

The proximal humerus, shoulder, and lateral two-thirds of each clavicle can all be covered by the interscalene block. It is vital to bear in mind that while trying to block locations in the arm and forearm, the lower trunk is frequently insufficiently blocked, and additional ulnar distribution blockades may be necessary. It has historically been unreliable for hand surgery. An interscalene nerve block is frequently employed either solely or in combination with other types of anesthesia to reduce pain during surgery or in the immediate aftermath of the procedure.

What Are the Indications?

The following are some indications regarding an interscalene nerve block:

• Shoulder treatment includes acromioplasty, rotator cuff restoration, labral repair, and complete shoulder replacement.

• Broken humerus.

• Clavicle damage.

• Other arm procedures that do not touch the hand or forearm's medial side.

What Are the Contraindications?

The following conditions are not appropriate candidates for an interscalene nerve block:

• Patient refusal.

• Infection at the intended site of injection.

• Existence of pre-existing neurologic deficits.

• An allergy to the local anesthetic.

• Coagulopathy (a condition characterized by impaired blood clotting.).

• Insufficiency of the contralateral phrenic nerve.

• A serious form of lung condition known as chronic obstructive pulmonary disease.

What Are the Methods of Anesthesia Administration?

• Ultrasonic Block Method: After placing the patient, the outermost layer of skin is cleansed, and the transducer is put over the neck to detect landmarks and structures. Two techniques are used to select images.

1. The transducer finds the carotid artery at the cartilage cricoid, which is medial to the sternocleidomastoid muscle.

2. The transducer finds the brachial plexus laterally within the anterior and middle scalene muscles.

The second method detects the subclavian artery with the brachial plexus by positioning the instrument slightly above the clavicle. The transducer is then placed downward towards the patient's neck until the "stop-light" image appears.

1. The needle in-plane inserts the transducer laterally to the medial.

2. Medial-to-lateral needle insertion works; after careful interscalene groove aspiration, the local anesthetic is administered.

3. Nerve stimulators move the shoulders and arms.

• Non-Ultrasound Block: The block uses the external jugular vein, clavicle, and sternocleidomastoid head. Cricoid cartilage aids. After locating these landmarks, the outer layer of skin is prepared, and the anterior and middle scalene muscles can be felt with gloves. Beneath the sternocleidomastoid's clavicular tip, near the cricoid cartilage. The external jugular vein usually crosses an interscalene groove. After subcutaneous anesthesia, the needle is put posteriorly from the external jugular vein, which is 3 to 4 cm above the bone of the collarbone, and advanced horizontally to the skin plane. The nerve stimulator detects brachial plexus activity as the needle advances. Most have one to two centimeters. Intermittent local anesthetic injections prevent intravascular injections.

What Are the Complications?

Interscalene blocks are very secure. Local anesthetic injections could result in problems. Other negative effects or issues, however, are more peculiar to the interscalene placement of the injection. Local anesthesia may cause other neighboring nerves to become anesthetized, leading to paresis in innervated structures. Similar in duration to the brachial plexus block, this impact is momentary and lasts just briefly. It is possible that low-volume ultrasound techniques could lessen the likelihood of these negative effects.

• Paresthesia or Nerve Loss Following Surgery: Patients may experience paresthesia for a brief period, but in the majority of cases, the symptoms disappear within weeks or months, which may lead to motor deficits. These are caused by nerve trauma during the insertion of the catheter or by injection of local anesthetic.

During the injection of local anesthetic, mild discomfort or aching at the injection site is common. Postoperative deficits may also result from surgical trauma, compression, or stretching of the plexus throughout the procedure, pre-existing deficits, or poor positioning.

• Toxicity of Systemic Local Anesthetics: When a local anesthetic is injected directly into a blood vessel, systemic toxicity might result.

1. When a local anesthetic is absorbed slowly, it can also result.

2. Poor technique can result in injections into the vertebral artery or external jugular vein, which can cause involuntary contraction and unconsciousness.

3. Local anesthetic absorption causes blood levels to rise after injection, on average. To avoid hazardous effects on a particular patient, the total amount of local anesthetic administered must be watched carefully and kept to a minimum.

• Hoarseness: Patients experience hoarseness (an abnormal change in the voice quality). It might happen as a result of local anesthetic spreading to the laryngeal nerves or dilatation of the blood flow to the larynx.

• Horner’s Disease: Horner syndrome is a rare condition characterized by a partial drooping or collapsing of the upper eyelid, constricted pupils, and a loss of facial sweating caused by a disruption in the sympathetic nerve supply.

• Pneumothorax: Pneumothorax is the medical term for the collection of air that occurs outside of the lungs but within the pleural cavity.

• Trauma in Various Forms: Under general anesthesia, the nerve stimulation method was used to place an interscalene block, resulting in spinal cord damage. To preserve the patient's capacity to experience and react to paresthesia, it may be appropriate to administer these blocks to conscious, sedated patients.

• Using an Intrathecal or Epidural Injection: The epidural space may occasionally experience local anesthetic tracking back via the plexus roots. To administer an intrathecal injection, a needle must be inserted into an intervertebral foramen or into a dural cuff, which is occasionally present when nerve roots emerge from the foramen.

Depending on the amount of local anesthetic in the area, an epidural or intrathecal infusion will have a certain impact.

• Diaphragmatic Paralysis: A condition in which the right or left side of the diaphragm loses the ability to contract to allow for adequate inspiration. This can be caused by muscular issues in the diaphragm or loss of innervation of the hemidiaphragm by the phrenic nerve.

• Ultrasound: Phrenic nerve impairment is diagnosed through diaphragm ultrasound. Inspiration lowers patients' diaphragm due to paralysis. The diaphragm might expand with the rib cage.

• Clinical Relevance: Unilateral diaphragmatic weakness cannot be clinically evident in most people with adequate pulmonary reserve at rest. Clinically substantial palsy from interscalene blockages causes dyspnea and the inability to breathe fully. Severe COPD or other conditions with reduced respiratory reserve induce this. The phrenic nerve block lacks local anesthesia.

• Mechanical Ventilation: Bed elevation makes breathing easier when treating dyspnea. Supplemental oxygen is adjusted to a safe saturation level. Most people need time to get through the barrier. Patients may need invasive or noninvasive mechanical ventilation.

Attenuated local anesthetics, smaller injectate volumes, and lower injection locations are used to treat phrenic nerve dysfunction. Blocking the primary shoulder sensory nerves distally eliminates the phrenic nerve's participation. The suprascapular and axillary nerves are being studied for blockage. The suprascapular/axillary group had better 24-hour pain control, while interscalene block recipients were more comfortable in the recovery room. They found that endoscopic shoulder surgery with combined suprascapular and axillary blocks is clinically successful and has a different analgesic profile than the interscalene block.

Conclusion

Interscalene nerve block involves placing local anesthetic over the brachial plexus roots or trunks that connect the anterior and middle scalene muscles at the vertebral body. Anesthesia or analgesia for shoulder and upper arm surgery is usually provided through interscalene nerve block. Shoulder surgery can be done with an interscalene block with sedation, although surgeons typically choose general anesthesia. Patients who receive either low-modified or standard interscalene brachial plexus blockade seem to be safe and receive appropriate analgesia as a result of the procedure. Ease of performance and overall patient comfort are two factors that can go into the decision of which block to utilize.