Introduction
Daycare/ambulatory anesthesia, aiming at early discharge and resumption of daily activities, has prompted the anesthesiologists to mold the anesthetic techniques for the provision of the same. Therefore, the focus has been diverted to the use of regional anesthesia techniques that are minimally invasive and are utilized in the entire perioperative period. Peripheral nerve blocks (PNBs) have revolutionized the practice of anesthesia by the provision of adequate analgesia and muscle relaxation in the intraoperative period and extension of postoperative analgesia that aids in good quality of life with early functionality. The blocks are usually well-tolerated, minimally invasive, and safe when administered with all precautions. In PNBs, the local anesthetic (LA) is deposited near the nerve bundle/plexus or the individual nerve to achieve motor and sensory blockade from that part of the body. Traditionally performed through anatomical landmark techniques, the safety and efficacy have further been improved with the introduction of peripheral nerve stimulators and ultrasound (US) that helps in localizing the nerves and administration of drugs near the vicinity of desired structures while avoiding damage to other nearby structures.
Historical Perspective
Historical milestones in the field of peripheral nerve blocks are:
1564: Ambroise Pare administered LA by nerve compression.
1600: Val Verde performed regional anesthesia (RA) by compression of nerves and blood vessels supplying the operating area.
1646: Marco Aurelio Severino administered refrigeration anesthesia by use of freezing mixtures of snow and ice.
1784: James Moore administered LA of extremity by compression of nerve trunks.
1839: Taylor and Washington introduced hypodermic injection.
1843: Alexander Wood invented the first true hypodermic needle to administer morphine injection.
1855: Friedrich Georg Carl Gaedcke isolated the alkaloid from leaves of the coca plant.
1860: Albert Friedrich Emil Niemann was involved in the purification and naming of cocaine.
1873: Hughes Bennett discovered the anesthetic properties of cocaine.
1884: Carl Koller’s first topical use of cocaine in eye surgery.
William Halsted and Richard John Hall (introduced brachial plexus blockade with cocaine).
William C. Burke (removed a bullet from finger under nerve block with cocaine).
1885: James Leonard Corning attempted spinal anesthesia.
1892: Karl Ludwig Schleich introduced infiltration anesthesia.
Francois-Frank coined the term nerve blocking.
1901: Cathelin and Sicard independently discovered caudal epidural block using cocaine.
1902: Heinrich F.W. Braun used epinephrine for nerve blockade and coined the term conduction anesthesia.
1908: George Washington Crile coined the term Anoci-association: regional block plus light general anesthesia (GA).
1922: Gaston Labat described the RA technique and clinical application.
1923: Gaston Labat founded the American Society of Regional Anesthesia (ASRA).
Indication and Applications (AS5.3)
PNBs may be used as a sole anesthetic technique for peripheral limb surgery or with GA for intraoperative and postoperative analgesia as well as reduction of the analgesic and anesthetic agents.
PNBs share advantages with the neuraxial anesthetic and analgesic techniques, the foremost being the lack of need for the airway instrumentation, especially in patients with underlying respiratory disorders or where the airway is deemed to be difficult and thus may be considered as the primary anesthetic choice in patients with underlying respiratory diseases or other comorbidities. However, the preoperative preparation for emergency airway management or for failed blocks is mandatory before the start of the procedure. The indications of PNBs are:
For emergency surgeries where the patient presents with a full stomach.
PNBs allow shorter time to discharge and are associated with lesser incidence of nausea and vomiting and thus is a choice of anesthetic technique in ambulatory surgeries, wherever feasible.
A certain subset of patients may themselves opt for PNBs to be awake during the surgical procedure.
PNBs may also be used for diagnostic, therapeutic, and prognostic purposes in the management of chronic pain syndromes.
PNBs may diminish or prevent the development of chronic pain syndromes by a lack of central nervous system (CNS) sensitization that occurs after acute injury.
Rarely, PNBs maybe opted as an anesthetic technique of the first choice in patients having allergies to multiple drugs, or patients wanting to avoid systemic drugs.
PNBs are also associated with decreased consumption of opioids, thus leading to reduced incidence of side effects of these drugs and therefore form the cornerstone of the multimodal analgesia and opioid-reducing approaches.
The contraindications to PNBs include:
Active infection at the site of injection.
Pre-existing neural deficits along the distribution of nerve of interest.
Patients with coagulopathy or receiving antithrombotic drugs.
PNBs are practiced by the anesthesiologists, surgeons, orthopedics, and emergency physicians. Irrespective of the specialty, PNBs require exemplary skill, mandatory monitoring, and preparation for all the resuscitative equipment before the conduct of the block.
Anatomy and Techniques (AS5.3)
The anatomy and landmarks relevant to the block to be performed depend upon the nerves required to be blocked for analgesia or anesthesia.
Techniques: The success of PNBs depends upon the accurate localization of nerve or plexus, and various techniques have been described and utilized for the same.
PNBs may be performed using the landmark technique with or without the peripheral nerve stimulator and the US-guided technology.
Landmark Technique
Paresthesia technique: Traditionally, the technique of eliciting paresthesia by using the well-defined surface landmarks has been utilized to perform the PNBs. A short beveled needle is usually advanced toward the target nerve and plexus to elicit paresthesia in the sensory distribution of the nerve and thus recognize the proximity of the nerve before administering the LA solution. Although most frequently employed, it carries a significant potential for direct intraneuronal damage, thus causing permanent neurological sequelae.
Nerve stimulation technique: The reports of neural damage with the paresthesia technique prompted the development of peripheral nerve stimulators. The target nerve or plexus is recognized by the help of electric current passed through an insulated plexus needle. The needle hub is attached to a wire that is further connected to a nerve stimulator that emits small pulses of electric current (0–0.5 mA, at a set frequency of usually 1–2 Hz), leading to depolarization and muscle contraction in the area of distribution of nerve supply. LA is deposited while the needle is in close proximity to the nerve, and the surety of the block can be determined by the rapid dissipation of the current density and elimination of the motor responses after the injection.
Ultrasound-Guided Technique
The capability to appreciate the neural and the associated delineation of the anatomy has popularized the use of US for performing the PNBs. The use of US also helps in reducing the complications related to drug, neural, and related structures and helps to deposit the LA at the intended place under direct visualization. The frequency of 1 to 20 MHz is employed for clinical imaging by ultrasonography with high-frequency probes for superficial structures and low frequency for the deeper structures.
Monitoring
All patients must receive premedication to alleviate anxiety. The procedure must be explained to the patient in his vernacular language, and informed consent sought before the block is administered. PNBs are conducted under aseptic conditions in the preoperative or the operative room with standard monitoring that includes ECG, noninvasive blood pressure, saturation, and respiratory pattern. An intravenous (IV) line must be secured before the block is performed, and the patient must receive oxygen supplementation if drapes are expected to cover the head and neck of the patient.
LAs that are utilized for anesthesia and analgesia have been discussed in Chapter 11 on LA, and the drugs may be administered with or without the adjuvants, depending upon the duration, nature, and extent of surgery.
The major peripheral blocks utilized for perioperative and postoperative pain have been discussed in the text.
Upper Limb Blocks
Brachial Plexus Anatomy (AS5.2, AS5.6)
The brachial plexus comprises the anterior primary divisions (ventral rami) of the fifth through the eighth cervical nerves and the first thoracic nerve. The nerve roots leave the intervertebral foramina and converge successively to form trunks, divisions, cords, branches, and finally, terminal nerves. The trunks are formed between the anterior and middle scalene muscles and are termed as superior, middle, and inferior trunk, based on their vertical orientation. As the trunks pass over the lateral border of the first rib and under the clavicle, each trunk divides into anterior and posterior divisions. As the brachial plexus emerges below the clavicle, the fibers combine again to form three cords that are named according to their relationship with the second part of the axillary artery, that is, lateral, medial, and posterior cord. The anterior division from the superior and middle trunks form the lateral cord, posterior divisions from all the trunks form the posterior cord, and the anterior division of the inferior trunk continues as medial cord. At the lateral border of the pectoralis minor muscle, each cord gives off a large branch before ending as a major terminal nerve. The lateral cord gives off the lateral branch of the median nerve and terminates as the musculocutaneous nerve. The medial cord gives off the medial branch of the median nerve and terminates as ulnar nerve. The posterior cord gives off the axillary nerve and terminates as a radial nerve (Fig. 13.1).
Brachial plexus blocks above the clavicle mainly target anesthetic placement near the ventral rami, trunks, and divisions. Blocks below the clavicle primarily target the cords and terminal nerves. Brachial plexus can be approached at many levels, as given in Table 13.1 and described below.
Related posts:
Full access? Get Clinical Tree
