Introduction
Four main pathologies affect the shoulder, and may require operative intervention. These are: arthritis of the glenohumeral and acromioclavicular joints, the stiff shoulder (including frozen shoulder/ adhesive capsulitis), rotator cuff pathology (representing a spectrum of pathology from subacromial impingement syndrome to cuff tear), and instability. Developments in minimally invasive techniques in recent years mean the anaesthetist is likely to encounter these conditions in the context of both arthroscopic and open procedures. Additionally, economic pressures have led to more surgery being undertaken in an ambulatory, day case setting, with high turnover lists and same day discharge. This trend requires anaesthetists to provide rapid, reversible anaesthesia with high quality peri-operative analgesia and minimal side effects. Recent technological advances in regional anaesthesia may help to meet these challenges1. This article aims to familiarize the reader with the general principles of anaesthesia for shoulder surgery, to review the evidence for current practice, and to consider the latest regional techniques, along with their feasibility in the UK setting.
Shoulder Surgery often generates high pain scores2-4 and thus effective pre-operative assessment and counselling is imperative.
Rotator cuff pathology is most commonly the cause of surgical intervention. Injuries to these muscles occur rarely in younger patients following trauma, and most commonly in older people (>45yrs) as a result of degeneration. Subacromial decompression and rotator cuff repair may be performed by an open or arthroscopic technique, with the latter being particularly painful, especially in the early rehabilitative phase. Frozen shoulder/adhesive capsulitits is perhaps the most painful shoulder condition and presents in the 40-65 year age group. It can be weakly associated with diabetes. Manipulation under anaesthetic or capsular release is undertaken for severe stiffness, with early physiotherapy and mobilisation required as an inpatient. Early postoperative analgesia is key to recovery in this scenario.
Degenerative disease of the glenohumeral joint is less common, and usually presents in those over 65 years. Shoulder arthroplasty is undertaken when arthritis is severe and may involve extensive bony surgery. Patients with advanced rheumatoid disease may present for this procedure, providing practical difficulties for the anaesthetist. A thorough airway assessment is required, and careful consideration should be given to intraoperative positioning. Regional anaesthesia is particularly indicated, often as an adjunct to general anaesthesia.
Shoulder instability is often related to sporting injuries, and accidents. This group of patients are young, fit and muscular. Recurrent instability may be associated with structural abnormalities needing repair, for example – Bankart's procedure or capsular shift. Analgesic requirements will generally be greater in younger patients.
In summary, a wide range of patients present for anaesthesia from the athlete to the systemically unwell rheumatoid patient with advanced joint disease. Due care and time should be allocated to giving a full and adequate explanation of any planned regional procedure, along with benefits and risks.
Perioperative Care
Regional anaesthesia forms the cornerstone of a multimodal strategy to minimize perioperative discomfort. Advantages may include: attenuation of surgical stimuli with stable anaesthesia, use of minimal anaesthetic agents to achieve relative hypotension and reduced intraoperative bleeding (particularly useful in arthroscopic surgery). Relaxation of joint musculature may enhance visualisation of the joint. In addition, reduced postoperative pain leads to less need for opiate analgesics, and lower rates of unexpected admission2-4. Disadvantages include: side effects and complications from the regional technique, including failure, and nerve injury. Some centres offer awake regional techniques as the sole anaesthetic in selected patients5-8.
Surgery may be performed in the lateral position or deck chair (beach chair) position (figure 1). A good fitting laryngeal mask airway is acceptable, but the airway may not be easily accessed. It is necessary to have a low threshold for inserting an endotracheal tube. Peripheral pooling of blood can lead to excessive hypotension and should be avoided. A pressure cuff sited on the forearm or calf is an alternative to the upper arm in the lateral position. Secure intravenous access of the non-operative hand will need to be accessed via an extension port. Over 8 litres of irrigation may be used for prolonged arthroscopy. As such, water resistant drapes should be used, alongside forced air warming devices to avoid hypothermia. Systemic absorption of irrigation fluid can lead to disturbances in fluid balance, and subcutaneous spread of fluid may be extensive, leading to further postoperative patient discomfort.
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| Figure 1: Patient in beach chair position. Note the distance of the airway and intravenous lines from the anaesthetic machine. |
Anatomy
There are up to five portal sites used for arthroscopic procedures. Occasionally a Nevaiser port is inserted between the posterior aspect of the clavicle and anterior to the scapula of spine (figure 2). The brachial plexus (C4-T1 nerve roots) supplies most of the superficial sensation to the shoulder, except for a “cape” like cephalad portion of skin above the clavicle, which is innervated by the supraclavicular nerves, originating from the lower part of the superficial cervical plexus (C3-C4). For open procedures, there are three major incisions: anterior (deltopectoral), antero-lateral (McKenzie or deltoid split, and posterior.
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| Figure 2: Sites of portals for arthroscopic surgery. |
The cutaneous supply to the shoulder is derived from the upper lateral brachial cutaneous nerve (C5-C6), which is a branch of the axillary nerve, and the lower lateral cutaneous nerve, which is a branch of the radial nerve. Together, these supply the skin over the deltoid and lateral side of shoulder. The intercostobrachial nerve (which is the lateral cutaneous branch of T2 intercostal nerve) supplies the skin over the medial portion of the shoulder and upper arm9 (figure 3). The intercostobrachial nerve is not part of the brachial plexus and may have to be blocked separately5.
