Anaesthesia for Orthopaedic Surgery

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Anaesthesia for Orthopaedic Surgery

One in five operations in the United Kingdom is for orthopaedic, spinal or trauma surgery. Anaesthesia for trauma surgery is discussed in Chapter 37. This chapter provides a framework for the conduct of anaesthesia for orthopaedic surgery.

THE PATIENT POPULATION

A large proportion of patients presenting for orthopaedic surgery are young and healthy. Sporting injuries and disease processes without systemic impact are common and these patients are at low risk of complications relating to anaesthesia or surgery. However, several disease processes are more common in patients presenting for orthopaedic surgery than in the general surgical population, and these are discussed below.

Comorbidities

Rheumatoid Arthritis

Rheumatoid arthritis is a chronic inflammatory disease of unknown aetiology, affecting women more often than men. Rheumatoid factor is found in 90% of affected patients and there exists a genetic predisposition with associated human leucocyte antigen HLA-DR4. It is a multisystem disease which may present the anaesthetist with problems of a difficult airway, cervical spine instability (and cervical cord vulnerability) and widespread vasculitis-induced organ dysfunction. Additionally, drug therapy for rheumatoid disease frequently produces severe and widespread side-effects. These are detailed below. The airway of the rheumatoid patient may present problems because of stiffness of the temporomandibular joint, stiffness or instability of the neck and cricoarytenoid arthritis. Radiological examination shows involvement of the cervical spine in 80% of patients, and 30% have neurological symptoms suggesting instability of the neck. Atlantoaxial subluxation, subaxial subluxation and cervical spine ankylosis are common, and should be investigated through history-taking, clinical examination and cervical X-ray. Flexion-extension views may be necessary to observe instability. Magnetic resonance imaging provides good assessment of the rheumatoid neck. Systemic disease is very common, and includes pericardial effusion, constrictive pericarditis, heart block, aortic and mitral valve disease, pleural effusion, interstitial fibrosis, anaemia, thrombocytopaenia and renal and hepatic dysfunction.

A thorough history and examination are important for patients with rheumatoid disease. Careful assessment of the airway and cervical spine should be performed. The range of neck movement should be assessed, and any associated neurological symptoms should be noted. A full blood count and serum urea and electrolyte concentrations should be measured, and an ECG and chest X-ray should be considered. Additionally, a lateral cervical X-ray, preferably with flexion-extension views, should be considered, particularly if tracheal intubation is planned. Systemic disease may indicate the need for arterial blood gas analysis, lung function tests, echocardiogram or liver function tests to be undertaken. Suspicion of cricoarytenoid involvement should prompt preoperative indirect laryngoscopic examination.

Regional anaesthesia should be used if possible. It has the advantage of avoiding airway and neck manipulation, and may be safer than general anaesthesia in patients with severe systemic disease. However, epidural and spinal anaesthesia may be very difficult because of spinal ankylosis and osteophyte formation. If general anaesthesia is used, patients with an unstable neck should be managed by an experienced anaesthetist, especially if tracheal intubation is planned. Tracheal intubation is made more difficult if movement of the temporomandibular joint is restricted. The need for tracheal intubation should be considered carefully in patients with severe disease because of the associated risks and difficulty. For many procedures, the use of a laryngeal mask airway is a suitable and a potentially less traumatic alternative. If tracheal intubation is required, intubation aids such as the intubating laryngeal mask airway or fibreoptic-guided intubation may be safer alternatives to tracheal intubation using direct laryngoscopy.

Osteoarthritis

A reduced range of joint movement may present problems in positioning, airway management, regional blockade and vascular access. Concurrent analgesic therapy may cause increased bleeding and renal dysfunction (non-steroidal anti-inflammatory drugs; NSAIDs) or tolerance to opioid analgesia (opioids).

Ankylosing Spondylitis

Ankylosing spondylitis causes rigidity of the entire spinal column, and may present problems with tracheal intubation. Unlike rheumatoid arthritis, cervical spine instability does not occur, but the fixed flexion deformity may render direct laryngoscopy utterly impossible. The use of a laryngeal mask airway is a suitable option for many procedures, and fibreoptic laryngoscopy is usually fairly straightforward unless the disease process is advanced. The normal routes of escape of local anaesthetic solution from the epidural space may be obstructed in patients with ankylosing spondylitis, and spinal cord ischaemia with permanent nerve damage has been reported after rapid injection of local anaesthetic into the epidural space in patients suffering from this condition.

Concurrent Drug Therapy

Many young healthy patients presenting for orthopaedic surgery do not take concurrent medication. However, use of analgesics is very common in the orthopaedic population because of the painful nature of their disease process. Concurrent therapy with antihypertensive, antianginal, antidepressant or cholesterol-lowering medication is common in older patients presenting for orthopaedic surgery. These patients often present for arthroplasty and this major procedure may place significant demands upon their physiological reserves. Preparation of the patient taking these drugs is discussed in detail in Chapter 18. Patients may also be using orthopaedic disease-modifying drugs such as methotrexate, steroids and gold.

Non-Steroidal Anti-Inflammatory Drugs

Thromboxane A₂ and prostaglandin endoperoxide, which are needed for the haemostatic function of platelets, are synthesized from arachidonic acid by the cyclo-oxygenase (COX) enzyme system. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit this enzyme system, impairing the formation of clots and, consequently, haemostasis. There are two COX isoforms: COX-1 synthesizes prostaglandins, which protect the gastric mucosa; COX-2 is involved with inflammatory responses. Inhibition of these systems ceases rapidly when administration of NSAIDs is stopped. However, the effects of aspirin persist for up to 10 days after treatment because of its covalent bonding with cyclo-oxygenase. Although NSAIDs taken up to the time of surgery may increase surgical blood loss, this does not imply that preoperative administration should be avoided. NSAIDs are valuable in providing analgesia pre- and postoperatively, and increased surgical blood loss is usually modest. Of more concern is gastroduodenal ulceration, of which the first symptom may be life-threatening upper gastrointestinal haemorrhage. The risk of ulceration is dose-related, commoner as age advances and even commoner if corticosteroids are also used to control inflammation. This complication stimulated the production of specific COX-2 inhibitors, but their use has been curtailed following reports of increased cardiovascular and cerebrovascular complications. NSAIDs should be avoided in patients who have a history suggestive of gastrointestinal ulceration or bleeding.

Opioid Analgesics

Chronic opioid use results in tolerance to the analgesic effects of the drugs and to their undesirable side-effects. When patients have used opioids for more than a few days before surgery, postoperative administration of an opioid becomes less effective than normal, and a larger dose is required than would be expected in the opioid-naïve patient. A useful guide is to provide the regular intake of opioid in addition to that prescribed for acute, postoperative pain relief. It is mandatory that frequent observations are made of these patients, and the involvement of an acute pain team is advisable.

Corticosteroids

Regular medication with glucocorticoid drugs (e.g. prednisolone, hydrocortisone, dexamethasone) produces suppression of endogenous glucocorticoid production. There is an increase in glucocorticoid concentration as part of the stress response after surgery, and these patients are at risk of an Addisonian crisis, including a precipitous fall in blood pressure because they may not be able to synthesize sufficient endogenous glucocorticoid. Patients who have taken doses of steroids greater than the equivalent of prednisolone 10 mg daily during the past 3 months require replacement corticosteroid therapy. Corticosteroid therapy may cause poor wound healing and gastrointestinal ulceration; consequently, low-dose replacement therapy is currently favoured. For patients undergoing minor surgery under general anaesthesia, the usual oral dose of corticosteroid should be given on the morning of surgery or a single dose of hydrocortisone 25–50 mg intravenously at induction. For patients undergoing moderate or major surgery, the usual morning dose of corticosteroid should be given and 25–50 mg of intravenous hydrocortisone at induction followed by further doses of 25–50 mg intravenously three times daily for 24 h after moderate surgery or for 48–72 h after major surgery. The patient’s usual corticosteroid regimen is then re-established.

Immunosuppressant Drugs

Drugs such as methotrexate inhibit the immune system, damping the inflammatory response that causes distressing symptoms from some joint diseases. The induced immunosuppression may also render the patient at increased risk of hospital-acquired infection, and strict aseptic techniques should be used during any invasive procedures.

Other Drugs

A large variety of potentially toxic drugs is used to reduce the symptoms and retard the disease process in rheumatoid arthritis. Antimalarials, such as chloroquine, may cause retinopathy and cardiomyopathy. Gold and penicillamine cause undesirable side-effects in up to 40% of patients; these include nephrotic syndrome, thrombocytopaenia, agranulocytosis, marrow aplasia, hepatitis and pneumonitis. Sulfasalazine may cause haematological toxicity and fibrosing alveolitis. Administration of azathioprine may result in gastrointestinal side-effects, cholestatic hepatitis, leucopaenia, thrombocytopaenia and anaemia.

It should be apparent that the provision of anaesthesia for any patient with rheumatoid arthritis must be associated with a thorough search for the potentially dangerous side-effects of concurrent drug therapy.

TECHNIQUES OF ANAESTHESIA

General Anaesthesia

This is appropriate for all types of orthopaedic surgery, but regional anaesthesia may be the preferred technique for many procedures, for reasons discussed below. Patients undergoing procedures of long duration (e.g. hip revision) often require general anaesthesia because of the discomfort incurred by remaining in the same position for a prolonged period of time. In many countries, including the United Kingdom, patients often expect to receive general anaesthesia, and may not have been aware in advance of their surgery that regional anaesthesia represents a viable option. Thus, the use of general anaesthesia offers the benefit to patients of familiarity. General anaesthesia causes the greatest loss of control for the patient and many patients are pleasantly surprised to find that regional anaesthesia is an option for their operation.

Regional Anaesthesia

Central neuraxial block (spinal or epidural anaesthesia) reduces the stress response to surgery and has been shown to reduce some serious complications following many types of surgery. Benefits may include a reduction in the incidences of deep vein thrombosis, blood loss, myocardial infarction, respiratory and renal complications, and possibly pulmonary embolism. There is a high incidence of thromboembolic events in patients undergoing major lower limb arthroplasty, which makes this type of anaesthesia an attractive option.

Lower limb arthroplasty and minor lower limb procedures are frequently carried out using central neuraxial block. For longer procedures, such as hip arthroplasty, sedation or light general anaesthesia may be added. The combination of general anaesthesia with a central neuraxial block has not been shown to reduce the benefits attributable to this form of regional anaesthesia.

Following central neuraxial block, the patient is usually pain-free in the immediate postoperative period. Careful thought should be given to administration of analgesia after the nerve block has worn off (see below). There is a higher incidence of urinary retention in patients who have undergone joint arthroplasty under central neuraxial block and this leads to an increased risk of urinary tract infection. Patients may be managed by prophylactic urethral catheterization or monitoring of bladder volume postoperatively using ultrasound.

Peripheral nerve block is commonly used as a sole technique for many procedures, with the advantages of excellent pain relief, reduction of surgical stress, avoidance of complications of general anaesthesia and earlier discharge in the day-case setting. Peripheral surgery in ‘high-risk’ patients may also be carried out under peripheral nerve block to avoid the potential complications of general anaesthesia or central neuraxial block. Patients report a high degree of satisfaction following surgery carried out using this form of anaesthesia. Table 28.1 shows the sites at which surgery may be performed in association with specific nerve blocks. This form of anaesthesia requires a high level of expertise and an understanding of the issues of managing a conscious patient during surgery.

TABLE 28.1

Peripheral Regional Anaesthesia and Analgesia

Intravenous regional anaesthesia (IVRA) is suitable for manipulation of fractures and brief operations (less than 30 min) on the forearm and lower leg. It is technically easy to perform but fatalities have occurred as a result of a large dose of local anaesthetic reaching the systemic circulation. Before performing IVRA, it is essential to understand how the risk of complications may be minimized and how they may be treated if they occur. Details of the technique and safety precautions are described in Chapter 24.

POSTOPERATIVE ANALGESIA

Oral and Intravenous Agents

Many patients are already taking regular analgesics for pre-existing bone and joint pain. Paracetamol is very useful in reducing the dose requirements of other analgesics, and may occasionally be sufficient analgesia alone. It is virtually free from side-effects in standard doses, and is contraindicated only in patients with liver dysfunction. If gastric motility is impaired, it may be administered rectally. The addition of NSAIDs, in the absence of contraindications, is usually useful and reduces the requirement for opioid analgesia.

NSAIDs inhibit the formation of prostaglandins and are widely used as analgesics in the treatment of acute bone-related pain. The newer COX-2 inhibitors potentially widened the number of patients who could benefit from these agents by reducing the potential for gastroduodenal ulceration, although as mentioned above, their use has been curtailed due to reports of increased incidences of myocardial infarction and stroke in patients taking long-term COX-2 inhibitors, leading to the withdrawal of rofecoxib in September 2004.

Prostaglandins are known to have an important role in bone repair and homeostasis. Animal studies have demonstrated that both non-specific and specific inhibitors of COX impair fracture healing. Some studies have suggested that this impairment results from COX-2 inhibition. This has raised concerns regarding the use of NSAIDs as anti-inflammatory or analgesic drugs in patients undergoing orthopaedic procedures; however, the clinical implications of this are probably minimal and NSAIDs remain extremely important analgesic agents for orthopaedic patients.

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