Diego Benítez and Luis M. Torres

*Department of Anesthesia, University Hospital Puerta del Mar, Cátedra del Dolor Fundación Grunenthal-Universidad de Cádiz Spain* 

#### **1. Introduction**

48 Modern Arthroscopy

Tauber, M., H. Resch, et al. (2004). Reasons for failure after surgical repair of anterior

Wolf, E. M. (1993). Arthroscopic capsulolabral repair using suture anchors. *Orthop Clin North* 

shoulder instability. *J Shoulder Elbow Surg* 13(3): 279-285.

*Am* 24(1): 59-69.

Arthroscopic shoulder surgery is a minimally invasive technique that effectively treats certain diseases and injuries of the shoulder joint. Indeed, new lesions and surgical techniques for their treatment have also been discovered by using this approach.

Controlling post-operative pain in shoulder surgery facilitates early mobilization and fast functional recovery, allowing pain-free muscle contraction. Tissue injury due to the surgical intervention results in the release of many chemical mediators that activate and increase the excitability of nociceptors, producing intra- and post-operative hyperalgesia. Local anesthesia can be used more frequently for less aggressive surgical techniques, particularly in limb surgery, both for intra-operative and post-operative pain.

It is essential to be familiar with the anatomy of the region to be anesthetized in order to minimize the potential risks and recognize them when they occur. The upper limb is innervated by the arms of the cervical spinal nerves (C5-C8) and part of the ventral branch of T1, although anatomical variations may exist. All these sensory, motor and vegetative nerve fibers form an "anastomotic complex of fibers", known as the brachial plexus.

The block of the brachial plexus was first developed in 1884, when Halstead injected cocaine into the exposed roots of the brachial plexus (1). However, it was not until 1911 that Hirschel and Kulenkampff described the percutaneous brachial plexus block first developing the axillary technique and then, the supraclavicular route (2,3). In 1919, Mulley developed a technique aimed at preventing pneumothorax by employing interscalenic approach to the brachial plexus (4). The modern interscalenic approach was perfected by Winnie, using the transverse processes of the 6th cervical vertebra (5) as a reference for needle insertion.

Anesthetic options for shoulder arthroscopic surgery include: general anesthesia, regional anesthesia with or without sedation, and a combination of both general and regional anaesthesia. Regional anesthesia offers many advantages over general anesthesia for arthroscopic shoulder surgery. The most notable advantage is the ability to control perioperative pain by proximally blocking the brachial plexus (supraclavicular approaches). The "Preemptive" analgesia afforded by the blockade and the excellent analgesic conditions can overt the need for intraoperative opioid administration. The patients' perception of pain-free surgery represents a further advantage of this approach. Together, this facilitates earlier hospital discharge with the attendant reduction in the economic cost of the procedure (6,7).

Anesthesia for Arthroscopic Shoulder Surgery 51

Fig. 1. Schematic representation of the structures of the left brachial plexus.

**3. Preoperative study** 

Situated at the upper surface of the spinous process of the cervical vertebra. From here they run out and down between the anterior and middle scalene muscles to reach the lateral base of the neck, close to the subclavian artery hat is above the pleural dome. They then appear

In the interscalene space, the middle and upper primary trunks are more superficial than the lower trunk. The supraclavicular part of the plexus undergoes its first division in the costoclavicular space, forming a group of clustered secondary trunks lateral and superficial to the subclavian artery, and above the first rib and pleural dome. At the infraclavicular level, the plexus forms a series of bundles or cords (lateral, medial and posterior) around the axillary artery. Distally the terminal branches are individualized, forming the median, ulnar and brachial cutaneous nerves, the medial forearm and the intercostobrachial nerve in the humeral canal. The musculocutaneous nerve and the radial nerve run outside the humeral canal.

Anesthesia visit should be used to carry out both a global study of the surgical-anesthetic risk, and to reduce the patient's anxiety before surgery. Indeed, the treatment of postoperative pain begins in this pre-operative period, with apprehension and anxiety increasing when patients are poorly informed as to the upcoming procedures. In examining the personal background of the patient, it is important to note any previous surgical

upper airway should be explored in detail, from the mouth to the base of the neck, noting and missing teeth or dentures that might make ventilation and endotracheal intubation more difficult. Observe whether the patient has a short neck or an increased cervical diameter, which determines the location of skin reference points for locking and positioning if an

interventions, particularly those in the cervical and thoracic region.

within the costoclavicular axillary canal, closely associated with the vascular bundle.

Relaxing the shoulder muscles is essential for successful surgery. We have observed that the muscle relaxation obtained following the interscalene blockage are superior to those observed with general anesthesia, without the need for tracheal intubation and mechanical ventilation due to neuromuscular blockade. Also, there is a decrease in perioperative bleeding associated with regional blockade in shoulder surgery (8). Mechanical ventilation increases intrathoracic pressure and as a consequence, the venous pressure in the upper limbs. This increase in pressure augments venous blood loss, which can be avoided if the patient is breathing spontaneously. In addition, the sympathetic blockade produced by regional blocking, combined with the semi-recumbent position of the patient, decreases venous pressure and bleeding. Hemodynamic stability itself favors regional anesthesia, decreasing mean arterial pressure and bleeding. Moreover, supraclavicular nerve blockage techniques without the need for general anesthesia decrease the possibility of aspiration of stomach contents, making them particularly attractive for emergency surgery.

The total time required does not differ greatly between the different anesthetic techniques, despite the obvious advantages associated with particular approaches. In fact, proximal brachial plexus block, performed by an expert, requires less time than the induction of general anesthesia, especially considering the shorter recovery time associated with regional anesthesia. In addition, the associated latency period can be used to position the patient and prepare the surgical area. The availability of a room for to perform specific preparation before the patient enters the operating theatre also optimizes resources and anesthesia times. Other notable advantages of regional versus general anesthesia include decreased postoperative complications, earlier discharge from the post-operative recovery room, the need for less apparatus, fewer nursing requirements and reduced hospital readmissions (9,10). Together, these advantages make such techniques the better choice for the majority of surgical procedures of the shoulder. The development of modern neurolocalization techniques, such as the use of ultrasound with peripheral nerve blockade, has improved the efficacy and safety of blind techniques, avoiding paresthesia and nerve stimulation, enabling real-time imaging of neural structures.

### **2. Anatomy of the proximal nerve structures in the upper extremity**

As indicated, the brachial plexus is formed by the anterior branches of spinal nerves C5-T1. The union of these fibers is highly variable among individuals and can even be asymmetrical in certain individuals, often also involving fibers C4 and T2. Nevertheless, the organization observed in up to 70% of cadavers involves 3 main trunks: the anterior branch of C5 fusing with that of C6 to form the upper primary trunk; the anterior branch of C7 forms the average primary trunk; and the anterior branch of C8 and T1 join to form the lower primary trunk.

Each of these primary trunks divides into an anterior and posterior branch. The three posterior branches unite to give rise to the posterior cord (the origin of the axillary nerve), circumflex and radial, which is the terminal portion. The anterior branches of the middle and upper primary trunks merge to form the lateral cord, which later gives rise to the musculocutaneous nerve and the lateral portion of the median nerve. The anterior branch of the inferior primary trunk gives rise to the medial cord, which will ultimately separate into the ulnar nerve, medial antebrachial cutaneous nerve and medial cutaneous nerve. The latter two, along with the intercostobrachial nerve, collect sensitivity from the medial arm. The median nerve also receives a portion of the medial cord (Figure 1)

Relaxing the shoulder muscles is essential for successful surgery. We have observed that the muscle relaxation obtained following the interscalene blockage are superior to those observed with general anesthesia, without the need for tracheal intubation and mechanical ventilation due to neuromuscular blockade. Also, there is a decrease in perioperative bleeding associated with regional blockade in shoulder surgery (8). Mechanical ventilation increases intrathoracic pressure and as a consequence, the venous pressure in the upper limbs. This increase in pressure augments venous blood loss, which can be avoided if the patient is breathing spontaneously. In addition, the sympathetic blockade produced by regional blocking, combined with the semi-recumbent position of the patient, decreases venous pressure and bleeding. Hemodynamic stability itself favors regional anesthesia, decreasing mean arterial pressure and bleeding. Moreover, supraclavicular nerve blockage techniques without the need for general anesthesia decrease the possibility of aspiration of

The total time required does not differ greatly between the different anesthetic techniques, despite the obvious advantages associated with particular approaches. In fact, proximal brachial plexus block, performed by an expert, requires less time than the induction of general anesthesia, especially considering the shorter recovery time associated with regional anesthesia. In addition, the associated latency period can be used to position the patient and prepare the surgical area. The availability of a room for to perform specific preparation before the patient enters the operating theatre also optimizes resources and anesthesia times. Other notable advantages of regional versus general anesthesia include decreased postoperative complications, earlier discharge from the post-operative recovery room, the need for less apparatus, fewer nursing requirements and reduced hospital readmissions (9,10). Together, these advantages make such techniques the better choice for the majority of surgical procedures of the shoulder. The development of modern neurolocalization techniques, such as the use of ultrasound with peripheral nerve blockade, has improved the efficacy and safety of blind techniques, avoiding paresthesia and nerve stimulation,

stomach contents, making them particularly attractive for emergency surgery.

**2. Anatomy of the proximal nerve structures in the upper extremity** 

The median nerve also receives a portion of the medial cord (Figure 1)

As indicated, the brachial plexus is formed by the anterior branches of spinal nerves C5-T1. The union of these fibers is highly variable among individuals and can even be asymmetrical in certain individuals, often also involving fibers C4 and T2. Nevertheless, the organization observed in up to 70% of cadavers involves 3 main trunks: the anterior branch of C5 fusing with that of C6 to form the upper primary trunk; the anterior branch of C7 forms the average primary trunk; and the anterior branch of C8 and T1 join to form the

Each of these primary trunks divides into an anterior and posterior branch. The three posterior branches unite to give rise to the posterior cord (the origin of the axillary nerve), circumflex and radial, which is the terminal portion. The anterior branches of the middle and upper primary trunks merge to form the lateral cord, which later gives rise to the musculocutaneous nerve and the lateral portion of the median nerve. The anterior branch of the inferior primary trunk gives rise to the medial cord, which will ultimately separate into the ulnar nerve, medial antebrachial cutaneous nerve and medial cutaneous nerve. The latter two, along with the intercostobrachial nerve, collect sensitivity from the medial arm.

enabling real-time imaging of neural structures.

lower primary trunk.

Fig. 1. Schematic representation of the structures of the left brachial plexus.

Situated at the upper surface of the spinous process of the cervical vertebra. From here they run out and down between the anterior and middle scalene muscles to reach the lateral base of the neck, close to the subclavian artery hat is above the pleural dome. They then appear within the costoclavicular axillary canal, closely associated with the vascular bundle.

In the interscalene space, the middle and upper primary trunks are more superficial than the lower trunk. The supraclavicular part of the plexus undergoes its first division in the costoclavicular space, forming a group of clustered secondary trunks lateral and superficial to the subclavian artery, and above the first rib and pleural dome. At the infraclavicular level, the plexus forms a series of bundles or cords (lateral, medial and posterior) around the axillary artery. Distally the terminal branches are individualized, forming the median, ulnar and brachial cutaneous nerves, the medial forearm and the intercostobrachial nerve in the humeral canal. The musculocutaneous nerve and the radial nerve run outside the humeral canal.
