OrthOpaedics

Anaesthesia for joint replacement surgeryMike Byrne

Barrie Fischer

AbstractJoint arthroplasty is now a routine, elective, surgical procedure. the age

group and associated co-morbid conditions of the patients who most

commonly undergo these major surgical procedures provide a number

of anaesthetic challenges to manage. hip, knee, shoulder and elbow

replacements each have specific requirements, but there is considerable

scope for developing a common patient care pathway, from preopera-

tive assessment clinic through to postoperative pain management for all

patients undergoing joint replacement surgery.

Keywords arthroplasty; elbow; general anaesthesia; hip; knee; regional

anaesthesia; shoulder

Joint replacement surgery has become routine with over 131,000 lower limb (hip and knee) joint replacement procedures being per-formed in England and Wales last year.1 This major surgery poses challenges for the anaesthetist owing to both the patient demo-graphics and specific considerations of the surgery. The patients are usually elderly (mean age 70 years) and commonly have coex-isting organ dysfunction. Of the patients undergoing primary lower limb joint replacement last year, 14% were American Society of Anesthesiologists (ASA) grade 3 or worse, and this figure rose to 25% for revision procedures (Table 1). The indications for surgery are pain and reduced joint mobility due to osteoarthritis (94%), avascular necrosis (4%) and rheumatoid arthritis (2%).1

Preoperative considerations

Patient assessment and optimizationPreoperative assessment and planning should minimize poten-tial anaesthetic problems, optimize co-morbidity and provide the most appropriate anaesthetic for the patient. The main anaes-thetic considerations are highlighted in Table 2.

Mike Byrne, BMBS, BmedSci, FRCA, is a Specialist Registrar in Anaesthesia

at the Alexandra Hospital, Redditch, UK. He qualified from Nottingham

University and trained in anaesthesia in Derby and the West Midlands,

UK. His main interests are regional anaesthesia, teaching and

management of the difficult airway. Conflicts of interests: none declared.

Barrie Fischer, FRCA, is Consultant Anaesthetist at the Worcestershire Acute

Hospitals Trust (Alexandra Hospital, Redditch, UK). He qualified from

Bristol University and trained in Cornwall, Cambridge and Cardiff, UK. His

research and teaching interests are the role of regional anaesthesia in

surgery and acute pain medicine. Conflicts of interests: none declared.

aNaesthesia aNd iNteNsiVe care MediciNe 10:1 1

Deep vein thrombosis prophylaxisIt is common practice in lower limb joint surgery to administer low-molecular-weight heparin (LMWH; e.g. 20–40 mg enoxapa-rin, subcutaneously, once a day) to prevent postoperative throm-boembolic disease. This must be administered at an appropriate interval before surgery, especially when neuraxial or peripheral regional techniques are used. A 10–12 hour interval should be maintained between the insertion of neuraxial block or the removal of an epidural catheter and the administration of LMWH (Table 3).2 Clear prescription guidelines should be available, on the ward and at the preoperative assessment clinic, to ensure that these timing intervals are observed.

For other anticoagulant treatment regimens (therapeutic doses of LMWH, or warfarin), the patient’s coagulation status must be monitored preoperatively, in collaboration with the haematol-ogy department, and treatment adjusted to ensure that the risk of excessive bleeding is minimized. Regional anaesthesia may be contraindicated in patients taking therapeutic anticoagulation, unless the balance of risk and benefit is strongly in favour of a regional technique and suitable modifications are made to the anti-coagulant regimen to ensure the safety of the regional technique.

Anaesthetic technique

Regional anaesthesiaRegional anaesthesia, either alone or in combination with a general anaesthetic, has become increasingly used for joint replacement surgery owing to the benefits it offers over an opioid-based general anaesthesia technique. Regional anaes-thesia in orthopaedics is covered more fully elsewhere (see pages 22–25, in this issue). Some of its benefits include the following.• Reduced incidence of postoperative deep vein thrombosis and pulmonary embolus in lower limb arthroplasty (owing to a sym-pathectomy-induced increase in blood flow and antagonism of the hypercoagulable state).• Reduced intraoperative blood loss (reducing the requirement for blood transfusion).• Improved postoperative analgesia compared with general anaesthesia.• Enhanced early postoperative rehabilitation and improved out-come from surgery (especially shoulder and knee arthroplasty).

American Society of Anesthesiologists (ASA) status for patients undergoing hip replacement procedures in England and Wales in 2006

ASA grade Primary hip (%) Revision hip (%)

1 23 15

2 63 59

3 13 25

4 1 1

5 0 0

National Joint registry data, 2007.

Table 1

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OrthOpaedics

Preoperative considerations for joint replacement surgery: possible investigations

Cardiovascular systemcoexisting pathology is common in this elderly population and typically includes ischaemic heart disease,

hypertension, congestive cardiac failure and the presence of arrhythmias

ecG

echocardiogram

Respiratory systempulmonary fibrosis may be present as a consequence of rheumatoid arthritis or as a side effect of drugs

used to treat this condition (e.g. methotrexate)

arterial blood gas

Lung function test

Renal dysfunctionrenal function (especially glomerular filtration rate) decreases with age and may be further affected by

hypertension and drugs (e.g. Nsaids)

Urea and electrolytes

haemoglobin

Musculoskeletal and airwayreduced joint movement and peripheral nerve impingement may be present

rheumatoid arthritis may affect the cervical spine resulting in atlantoaxial subluxation airway assessment

careful consideration should be given to the cervical spine during airway manipulation and head positioning.

a potentially difficult airway may be anticipated owing to reduced neck extension and poor mouth opening

cervical spine radiographs

Multi-pharmacyMulti-pharmacy is common in the elderly; biochemical abnormalities may be present (diuretics) and possible

interactions with anaesthetic agents should be considered. Warfarin, Nsaids, β-blockers and angiotensin-

converting enzyme inhibitors are commonly prescribed in this age group for arrhythmias, pain, ischaemic

heart disease and hypertension, respectively. these are important when considering regional anaesthetic

techniques and perioperative cardiovascular performance. preoperatively, anticoagulant agents should be

stopped in good time and clotting studies performed when planning neuraxial and regional techniques

take a detailed drug history

Nsaid, non-steroidal anti-inflammatory drug.

Table 2

• Reduction in the effects of general anaesthesia and system-ic opioid analgesia on pulmonary function (basal atelectasis, hypoxaemia and pulmonary infection) and reduced incidence of postoperative nausea and vomiting.• It may avoid the need for endotracheal intubation and the consequent vasopressor response.

Of all lower limb joint replacements, 87% utilize either a neuraxial block or a regional anaesthetic technique.3 Spinal anaesthesia is the most commonly used technique, usually in

Neuraxial anaesthesia in patients receiving anticoagulation2

Timing of neuraxial anaesthesia

Warfarin ensure iNr <1.5 before

neuraxial anaesthesia or

catheter removal

Unfractionated heparin Wait 2–4 hours after dose, can

heparinize 1 hour after

Low-molecular-weight heparin

(prophylactic once-daily dosing)

Wait 10–12 hours after dose,

can heparinize 4 hours after

Nsaids No contraindication

clopidogrel discontinue for 7 days

Glycoprotein iib/iiia inhibitors discontinue 8–48 hours

iNr, international normalized ratio; Nsaid, non-steroidal anti-inflammatory drug.

Table 3

aNaesthesia aNd iNteNsiVe care MediciNe 10:1 11

combination with intravenous sedation although epidural block-ade and lumbar plexus blocks are also widely used. These are usually combined with a light general anaesthetic.

Sedation may be necessary for prolonged operations or uncomfortable patient positioning. This can be achieved by inter-mittent boluses of midazolam, 0.5–1 mg increments, or by target- controlled infusion of propofol, aiming for a plasma concentration of 0.5–3 μg/ml. Supplemental oxygen should be administered.

General anaesthesiaGeneral anaesthesia is primarily indicated for patients with demen-tia (or other causes of lack of cooperation), for those who are unable to lie flat as a result of cardiovascular or respiratory dis-ease and for those in whom neuraxial anaesthesia is specifically contraindicated. General anaesthesia is commonly combined with a regional technique, for example lumbar plexus block. Both laryn-geal mask airways and endotracheal tubes can be used to secure airway maintenance. An endotracheal tube is preferred if there is limited access to the airway, if the patient has a history of gastro-oesophageal regurgitation or if a difficult airway is anticipated.

MonitoringEstablish intravenous access with a large-bore (14 or 16 G) can-nula and apply standard non-invasive monitoring (ECG, pulse oximetry and non-invasive blood pressure monitoring). For patients who have significant co-morbidity, or who are under-going a joint revision procedure (in which blood loss is greater), an arterial line and central pressure venous catheter may be used for continuous intravascular monitoring, haemodynamic support and fluid management.

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OrthOpaedics

Antibiotic prophylaxisPreoperative antibiotic prophylaxis is usually administered intra-venously immediately before induction of anaesthesia. Consult the local antibiotic prescribing guidelines to minimize the risk of superinfection with Clostridium difficile (e.g. flucloxacillin 1 g + gentamicin 160 mg).

Intraoperative considerations

Cement reactionsImplanted prostheses are commonly cemented using methyl-methacrylate cement. Under pressure from the cement implanta-tion, a microembolic shower of blood, fat and platelet aggregates can enter the venous circulation. This can cause potentially fatal complications when the circulation debris enters the pulmonary circulation because of an increased pulmonary shunt (venous admixture), pulmonary hypertension and reduced ventricular performance with reduced ventricular ejection. The subsequent hypotension may be insufficient for coronary perfusion, lead-ing to further reductions in myocardial performance. The main clinical signs are:• hypoxaemia• hypotension• dysrhythmias• cardiovascular collapse.

A degree of intravenous fluid loading prior to cementing can help to minimize these effects and further fluids, boluses of vaso-pressors (ephedrine) and supplemental oxygen may be required to restore haemodynamic stability and oxygenation.

HypothermiaHaemostatic mechanisms are reduced with old age; therefore, temperature haemostasis is important. Heat loss can be signifi-cant because of anaesthesia-induced peripheral vasodilatation, large wound surface area, high-flow laminar theatre circula-tion systems, major fluid shifts or prolonged surgery. Warmed intravenous fluids and a hot air warming device are desirable.

HypovolaemiaBlood loss can be significant, particularly with revision joint replacement procedures. When using a tourniquet, blood loss may become apparent only in the recovery unit or on the ward. In the elderly, the physiological compensatory mechanisms for hypovolaemia are poor. The elderly commonly have coexisting ischaemic heart disease and, as a consequence, arterial oxy-gen-carrying capacity and coronary perfusing pressure should both be maintained. Cell savers are increasingly used as a safer and financially viable alternative to homologous blood trans-fusion (they are contraindicated in patients with infection or metastatic malignancy); the collected blood can be spun down and transfused back to the patient in the immediate postopera-tive period.

Patient positioningPatients are likely to have musculoskeletal problems and can be frail. Care must be taken to support patients and to cushion them from any potential pressure effects and avoid overextension or flexion of joints (especially the neck in patients with rheumatoid arthritis).

aNaesthesia aNd iNteNsiVe care MediciNe 10:1 12

ThromboembolismFollowing joint replacement venous thromboembolism is a ma-jor cause of death because of endothelial wall damage, venous stasis and surgically induced procoagulant conditions (Virchow’s triad). Strategies to reduce the risk include a combination of the following:• regional anaesthesia (increased venous blood flow)• anticoagulation: LMWH, low-dose warfarin, aspirin• thromboembolic disease stockings or pneumatic leg compres-

sion devices• gelatine-based colloids• early mobilization.

TourniquetsA tourniquet may be used to create a dry surgical field for knee replacement. However, deflation of the tourniquet can release anaerobic metabolic by-products (e.g. potassium, lactate) into the venous circulation, which can reduce myocardial contractility and decrease systemic vascular resistance, leading to systemic hypoten-sion. Vigilance, warning by the surgeon before tourniquet deflation and the administration of vasopressors help in these circumstances (see also pages 14–17, in this issue).

Postoperative considerations

AnalgesiaNerve blocks and neuraxial techniques provide better postop-erative pain relief than systemic opioids alone.4,5 A multimodal approach in which two or more drugs acting on different receptors in the pain pathway are used in combination is beneficial com-pared with large doses of a single analgesic. In combination with a regional technique, systemic agents, such as regular paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs), provide effective analgesia. Opioids may be given as rescue analgesia for high-intensity pain (before mobilization and physiotherapy).

If regional analgesia is not used, strong opioids given as intravenous boluses (1–2 mg morphine, to a total of 10–20 mg) are necessary to control pain in the early postoperative period. The dose depends on the patient’s weight and age. Intravenous patient-controlled analgesia (PCA) or on-demand opioids, com-bined with paracetamol and NSAIDs, provide effective analgesia after the initial period of early recovery. The benefits of using NSAIDs in the elderly must be balanced against the increased risk of impaired renal function, which may be worsened by haemodynamic instability and fluid losses during surgery.

OxygenSupplemental oxygen should be used for the first three days post-operatively to minimize the risk of perioperative ischaemic episodes.

Fluid and blood replacementIf a tourniquet has been used the actual blood loss may only become apparent in the recovery room or on the ward. Prompt recognition of this is important and appropriate fluid administra-tion, including blood replacement, must be commenced quickly.

High-dependency unitPatients with significant pre-existing morbidity and those hav-ing revision procedures with a prolonged duration and high

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anticipated fluid losses should be managed postoperatively on the high-dependency unit (HDU).

Specific procedures

Revision proceduresApproximately 10% of all joint replacement procedures are revi-sion procedures.1 Revision surgery may be necessary because of loosening of the original prosthesis, infection, a peripros-thetic fracture or ongoing pain. Additional problems that need to be considered when performing a revision joint replacement procedure include:• patient’s age; the lifespan of a primary joint replacement is

10–15 years and these patients may be more elderly and frail than primary joint recipients (25% ASA grade 3 or above)

• increased blood loss• longer operative time (risk of hypothermia)• greater postoperative stress response and pain intensity• postoperative HDU requirement.

A urinary catheter may be required for accurate fluid balance, especially if an epidural infusion is used for postoperative analge-sia. A general anaesthetic combined with a regional anaesthetic technique, invasive monitoring, good fluid balance, temperature haemostasis and postoperative HDU care represent an appropri-ate standard of care.

Upper limb joint replacementsShoulder surgery generally requires the sitting or beach chair position and consideration should be given to maintaining the cerebral perfusion pressure because the head is elevated above the heart. For the same reason, venous air embolism may occur from the surgical field. Access to the patient’s airway is limited and therefore intubation and ventilation with an endotracheal tube is usual. This procedure is painful postoperatively, and a brachial plexus block via the interscalene approach provides effective postoperative analgesia. Elbow replacement involves difficult patient positioning, with the patient in the lateral posi-tion with the arm flexed over a supporting bar (Figure 1). This

Figure 1   position of patient for elbow replacement surgery.

aNaesthesia aNd iNteNsiVe care MediciNe 10:1 1

operation is also very painful postoperatively and an axillary bra-chial plexus block provides good postoperative analgesia.

Lower limb joint replacementCurrent data for anaesthetic techniques used in England and Wales for lower limb joint replacements are summarized in Table 4 (these data include combinations of techniques). The PROSPECT (Procedure Specific Postoperative Pain Management) group has made recommendations for the provision of postop-erative analgesia for primary hip and knee arthroplasty following systematic reviews of 55 and 100 randomized controlled trials respectively. For primary hip arthroplasty this group recommends that ‘based on postoperative pain outcomes the continuation of some form of regional analgesia following general anaesthesia is recommended over the use of general anaesthesia alone’. Based on the relative adverse events profiles of regional techniques, the group suggests that lumbar plexus blockade should be used in preference to epidural or spinal anaesthesia.4 For primary knee arthroplasty, the group recommends a femoral nerve block in combination with either a general or spinal anaesthetic.5 ◆

REFERENCES

1 National Joint registry for england and Wales. 4th annual report,

september 2007. available from: www.njrcentre.org.uk

2 american society of regional anesthesia and pain Medicine.

consensus document on regional anesthesia and anticoagulation.

available from: www.asra.com, 2003.

3 National Joint registry for england and Wales. 3rd annual report,

september 2006. available from: www.njrcentre.org.uk

4 prOspect. a systematic review of post operative analgesia for

primary hip arthroplasty. available from: www.postoppain.org

5 prOspect. a systematic review of post operative analgesia for

primary knee arthroplasty. available from: www.postoppain.org

FURTHER READING

chelly J, casati a, Fanelli G. Orthopaedic anaesthesia. London:

Greenwich Medical Media, 2008.

edge G, Fennelly M. trauma and orthopaedic anaesthesia in a nutshell.

Oxford: Butterworth-heinemann, 2004.

Loach a. Orthopaedic anaesthesia, 2nd edn. London: hodder arnold, 1994.

Anaesthetic techniques used for joint surgery in England in 2005

Primary hip (%) Primary knee (%)

spinal anaesthesia 52 49

epidural anaesthesia 18 16

General anaesthesia 54 51

regional nerve blockade 11 22

National Joint registry data, 2006.

Table 4

3 © 2008 elsevier Ltd. all rights reserved.