Nerve Block: An Overview

Introduction:

Nerve blocks and neurostimulation are viable treatment options for patients suffering from headaches and neck neuralgia patients. Furthermore, these peripheral nerve procedures can help with primary headaches like migraine and cluster headaches. Nerve blocks for headaches are typically performed with small subcutaneous injections of amine group local anesthetics like Lidocaine and Bupivacaine. Recent advancements in numerous surgical techniques and less invasive procedures have increased outpatient procedures. With these advances made, analgesic techniques must maintain with surgical advancements. Peripheral nerve blocks are generally safe and provide better regional analgesia than other methods like oral pain medications or general anesthesia.

The presently available pharmacological agents intended to treat acute headaches or prevent headaches may fall short in some patients. In addition, pharmacological approaches may be dangerous for some people due to various factors, including concurrent cardiovascular, cerebrovascular, or peripheral vascular disease, hepatic or renal disease, pregnancy, or psychiatric conditions. However, peripheral nerve procedures, such as nerve blocks and nerve stimulation, can benefit many patients and should be considered.

What Is the Rationale for the Nerve Blocks?

• The rationale for using peripheral nerve blockade for relieving pain is based on local anesthetics' ability to block the sensory nerve fibers selectively (while preserving motor function) in mixed nerves at relatively low doses.

• The dose and the pharmacological activity of the specific local anesthetics determine the intensity of the block. Still, all or some benefits have been observed to last longer than anticipated.

• Furthermore, blocking several nerves in the head and neck can favor pain syndromes affecting areas other than the territory areas supplied by the anesthetized nerve.

What Are the Indications for Nerve Blocks?

There are no specific standards for using peripheral nerve blocks. However, the general rationale is to use regional blocks when the conservative approach fails or to prevent unnecessary side effects and complications associated with general anesthesia and oral medications. The following are some situations in which peripheral nerve blocks are indicated:

• Patients who are at high risk of developing respiratory depression as a result of general anesthesia.

• Patients who wish to refrain from taking routine medicines.

• Patients who are unable or unwilling to take oral medications.

What Are the Contraindications for the Nerve Blocks?

1. Absolute Contraindications: Allergy to local anesthetic drugs used, unwillingness to cooperate, or patient refusal.

2. Relative Contraindications: Ongoing active infection in the treated area, pre-existing neural deficiencies along the course of distribution of the block, and patients with coagulation disorders or on antithrombotic drugs, it is strongly suggested to postpone or re-evaluate a nerve injection.

How Is the Patient Prepared for the Nerve Blocks?

• A comprehensive and detailed medical history is required to rule out conditions such as coagulation or respiratory disorders that may influence the choice to perform a block.

• A complete physical exam is also recommended to rule out any pre-existing sensory or motor dysfunction in the block area.

• Following the medical history and physical examination, the patient should know the risks, benefits, and care required during recovery.

• Patients undergoing a nerve block for a surgical procedure should adhere to the exact fasting instructions during the surgery, as they may require deep sedation in cases of an incomplete block.

• In addition, they should obtain intravenous access due to the possibility of complications such as vasovagal events.

What Is the Technique of the Nerve Blocks?

The type of block determines the procedure for peripheral nerve blocks:

Interscalene Block:

• Cervical plexus nerve roots (third cervical and fourth cervical vertebrae, supraclavicular nerve) and brachial plexus, both the upper and the middle trunks are anesthetized (fifth cervical vertebrae to the seventh cervical vertebrae).

• The patient is supine, with the head shifted to the opposite side of the block. The sternocleidomastoid muscle's sternal and clavicular heads, sternal notch, and the clavicle, are recognized and marked.

• If ultrasound is used, a probe is placed transversely across the neck, just above the clavicle, with its long axis. The internal jugular vein and carotid artery are accessible.

• The subclavian artery is recognized by directing the ultrasound beam toward the first rib. The nerves are then tracked down to the cephalad.

• The C6 brachial plexus nerves are seen vertically within the inter-scalene groove.

• The needle is then oriented toward the nerves, either in-plane or out-of-plane. A needle tip is inserted near the nerve roots. Local anesthetic is injected in amounts ranging from 12 to 30 cc.

Supraclavicular Block:

• The patient is positioned supine, with both hands by the sides and head tilted away from the side of the block.

• Using ultrasound, the probe is placed in a transverse position just above the clavicle. The internal jugular vein and carotid artery are visible.

• A local anesthetic is injected into the needle as it is inserted in-plane (parallel to the probe) to hydro dissect between the nerves till the tip approaches an area surrounded by the first rib, subclavian artery, and brachial plexus.

• A volume of 20 to 30 cc of local anesthetic is administered. Should accomplish negative aspiration before injection to ensure that there is no blood.

Infraclavicular Block:

• The patient is supine, with the head tilted to the opposite side of the block.

• To identify the coracoid process, the arm is moved away from the body with the elbow flexed.

• The axillary artery is recognized, and the brachial plexus cords are visualized by ultrasound.

• The needle is inserted into the cranio-posterior quadrant, next to the axillary artery, and 30 to 40 cc of local anesthetic is injected.

Axillary Block:

• This block anesthetizes brachial plexus nerves at the level of each nerve. The patient is supine, with the arm moved away from the body, and establishes 90 degrees angle with the elbow flexed.

• Using ultrasound, the transducer is positioned transversely in the axilla.

• The needle is inserted perpendicular to the skin and advanced till the tip of the needle is adjacent to each nerve.

Intercostobrachial Block:

• The patient is lying on his back with his arm moved away from the body to expose the axillary fossa. The intercostobrachial nerve runs through the medial upper arm's subcutaneous tissue.

• While injecting five to ten cubic centimeters of local anesthetic, the needle progresses subcutaneously across the arm's medial aspect.

Radial Nerve Block:

• The radial nerve arises immediately adjacent to the styloid process, between the brachioradialis tendon and the radius.

• The needle is placed subcutaneously, adjacent to the radius's styloid process, attempting medially, and three to five cubic centimeters of local anesthetic is administered.

The Median Nerve Block:

• The median nerve block is positioned between the flexor palmaris longus and flexor carpi radialis tendons.

• The needle is advanced between the two tendons until it pierces the fascia and comes into contact with bone. Should relocate the needle, and local anesthetic should be deposited lateral and medially.

Ulnar Nerve Block:

• The ulnar nerve goes between the ulnar artery and the tendon of flexor carpi ulnaris. The tendon is just above the ulnar nerve.

• A needle is progressed 5 mm to 10 mm under the tendon adjacent to its attachment just above the styloid process of the ulna, and three to five cubic centimeters of local anesthetic is delivered at this site.

Lumbar Plexus Block:

• The patient is positioned in lateral decubitus, operative side up, with the leg bent at the hip and knee.

• The ultrasound probe is placed longitudinally adjoining the spine at the second to third lumbar level.

• Then, the needle is introduced at the cephalad border utilizing the in-plane technique. As the needle enters the target structure, the posterior third of the psoas major muscle, its length should be visible.

Femoral Nerve Block:

• The patient is positioned supine. The nerve, which lies lateral to the artery, is visualized using ultrasound.

• In-plane or out-of-plane techniques can be employed when the needle is introduced, the tip positioned adjacent to the nerve, and 20 to 50 cc of local anesthetic is administered in five cc (cubic centimeters) increments. Should accomplish negative aspiration before injection to ensure that there is no blood.

Fascia Iliaca Block:

• The patient is positioned supine, and the probe is installed transversely to the leg at the intersection of the middle and lateral thirds to locate the fascia lata, iliacus muscle, and fascia iliaca utilizing ultrasound.

• The needle is inserted inferior to the inguinal ligament and directed just below the fascia iliaca before administering 30 cc of local anesthetic in five cc (cubic centimeters) increments.

• Should accomplish negative aspiration before injection to ensure that there is no blood.

Obturator Nerve Block:

• The patient is positioned supine with one leg rotated externally. The femoral vein is located using an ultrasound probe in the inguinal crease.

• The probe is moved medially to visualize the pectineus and adductor longus muscles.

• The needle is introduced either in-plane or out-of-plane and guided to the fascial plane between the adductor brevis and magnus, where five to ten cubic centimeters of local anesthetic is administered.

Sciatic Nerve Block:

• Can be reached from either the front or the back. For the posterior approach, the patient is positioned in lateral decubitus with the hip flexed (bringing the knee closer to the chest) at 45 degrees and the knee bent at 90 degrees.

• The patient is positioned similarly in the anterior approach. The probe is kept transverse to the nerve distribution using an ultrasound probe.

• The nerve is located deep in the gluteus maximus muscle and lateral to the ischial tuberosity.

• The needle is inserted in-plane from the transducer's lateral side and positioned with the needle tip adjoining the nerve. About 20 cc of local anesthetic is administered in five cc (cubic centimeters) increments, with gentle aspirations.

PENG Block:

• The pericapsular nerve group (PENG) block is an inter-fascial plane block that aims to prevent articular branches delivered by the femoral, obturator, and accessory obturator nerve.

• It is recommended for anterior and lateral hip arthroplasties and hip fractures. Under direct ultrasound guidance, 15 to 20 ml (milliliters) of local anesthetic is deposited in the plane between the psoas tendon and the pubic ramus in the supine position.

• Post-operative pain relief in hip surgeries is managed using femoral nerve blocks, fascia iliaca compartment blocks, or lumbar plexus blocks. However, these blocks cause quadriceps muscle weakness and thus increase susceptibility to falling. These blocks also cause insufficient hip analgesia due to sparing a few articular branches to the hip.

• The main benefit of PENG block is that it gives excellent hip analgesia without causing muscle weakness. As a result, the patient can start physical therapy as soon as possible.

The Infiltration Between the Popliteal Artery and Capsule of the Knee(iPACK) Block:

• The infiltration between the popliteal artery and capsule of the knee (iPACK) block relieves pain after total knee arthroplasty and cruciate ligament repair.

• Posterior knee pain is caused by articular branches originating primarily from the tibial and obturator nerves.

• Under ultrasound visualization, 15 to 20 ml of local anesthetic is deposited in the femoral artery tissue plane and the posterior aspect of the knee capsule during an iPACK block.

What Are the Complications of the Nerve Block?

The type of block employed determines the potential complications and side effects. However, complications include peripheral nerve damage (which is uncommon and can occur at a rate of up to ten percent), hematoma, systemic toxicity of the local anesthetic drug, anaphylactic reaction, infection, and a secondary injury, which involves decreased sensation after nerve block.

Conclusion:

Anesthetists, surgeons, and emergency care specialists frequently conduct peripheral nerve blocks. A designated nurse must assess the patient's vital signs during the procedure. A peripheral nerve block protocol should be developed to ensure patient safety and enhance patient outcomes