Anaesthesia in Orthopaedic Surgery

Anaesthesia in

Orthopaedic Surgery

 

 

 

Introduction 1‌

Preoperative assessment 1‌

Intraoperative techniques 5

Postoperative care 6

Viva questions 9

 

Introduction‌

The orthopaedic patient population presents many challenges. It includes the extremes of age, comes with a range of embedded medical co-morbidities and presents with diverse surgical pathology requiring varied intervention. Procedures range from day-case minimally invasive arthroscopic procedures to extensive operations that test the physiological reserve of an individual patient. Due to these concerns, an individual anaesthetic is customised to the medical demands of the patient, the requirements for the surgical technique and the limitations of the institution in which the surgery occurs.

 

Preoperative assessment‌

This is the process of assessing the relevance, severity and treatment of medical pathologies. This allows referral for better treatment (‘optimisation’) and quantification of the risk of adverse perioperative events, including death, to be discussed and documented. Factors specific to anaesthesia, such as a possible difficult airway, may also be considered. Guidelines exist to inform the ordering of preoperative laboratory tests. In addition, the optimisation of patients prior to admission for surgery is aimed to reduce cancellations on the day of surgery and to increase the productivity of the theatre suite.

 

Fasting

In elective surgery, standard local fasting times must be adhered to. A typical regimen is given in Table 1.1. Food includes milk and fresh fruit juices. It is safe for patients (including diabetics) to drink specialised carbohydrate-rich (maltodextrins) drinks up to 2 hours before elective surgery as this improves subjective well-being, reduces thirst and hunger and reduces postoperative insulin resistance.

 

Table 1.1 Fasting times

 

	Typical foods
	Solid food	Water	Breast milk	Formula milk
Fasting time	6 hours	2 hours	4 hours	6 hours

 

In trauma situations, gastric emptying is affected from the time of injury and is further complicated by the use of opiate analgesics that prolong gastric emptying. Fasting times are difficult to interpret in this situation but can be calculated as the time of intake to time of trauma. In certain situations, the clinical priority for surgical intervention may override fasting policy, and clear discussion between clinicians caring for the patient needs to occur.

 

Airway

Airway assessment involves both bedside tests and if needed, radiological tests. A range of bedside tests exist that aim to predict difficulties in maintaining an airway or intubating an anaesthetized patient. Used individually, each airway assessment has poor sensitivity and specificity, however when combined can be a useful marker.

Of particular importance in orthopaedic surgery is pathology or trauma to the cervical column. Rigidity of the cervical column (e.g. in ankylosing spondylosis) may cause a problem with maintaining an airway and with difficult laryngoscopy. An unstable cervical column (e.g. trauma or rheumatoid arthritis) can lead to cord injury. Initial radiological assessment is with a plain film in anteroposterior (AP), lateral, flexion and extension views. If there are any concerns, then specialised investigations to delineate pathology include computed tomography (CT) and magnetic resonance imaging (MRI).

 

Cardiovascular assessment

Cardiovascular assessment is aimed at quantifying the ability of the cardiovascular pump to increase work to match perioperative metabolic demands. This is during both the operative period and rehabilitation. It is an assessment of reserve and a prediction of adverse events such as an acute coronary syndrome. Key clinical markers are described in the following sections.

 

Exercise tolerance/functional status

For patients having major, non-cardiac surgery, the inability to climb two flights of stairs confers an increased risk of major postoperative complications but is not predictive of mortality. Difficulties in this assessment are common for orthopaedic patients due to their pathology affecting mobility.

 

Previous myocardial infarction

There is a risk of recurrent perioperative myocardial infarction (MI), which has a 60% mortality rate. The longer surgery can be postponed after an MI, the lower is the rate of recurrent MI (Table 1.2).

 

Table 1.2 Percentage risk of recurrent myocardial infarction (MI) at different times after MI

 

Time since MI	Risk of recurrent MI (%)
<3 months	5.7
4–6 months	2.3
>6 months	1.5

 

Investigations

Typical investigations used to quantify cardiac reserve are as follows:

 

• Exercise electrocardiogram (ECG): This helps to determine any coronary flow limitation when cardiac work increases.

• 24-hour ECG recording (Holter monitor): This involves continuous ECG recording for 24–48 hours to investigate possible arrhythmia.

• Thallium scintigraphy and dobutamine stress echocardiography: These dynamic ‘stress tests’ are especially useful for patients who are unable to perform exercise ECG due to musculoskeletal disease or severe cardiopulmonary disease. Perfusion defects of the myocardium under physiological stress indicate coronary insufficiency.

• Cardiovascular MRI: This is a non-invasive assessment of the function and structure of the cardiovascular system. It provides information on cardiac structure, cardiomyopathy and perfusion defects.

• Cardiopulmonary exercise testing: This is a dynamic test that predicts the patient’s anaerobic threshold. It can indicate the respiratory and cardiac reserve but can be affected by other factors such as motivation, mobility and nutrition. It can be used to predict the risk of surgery and obviate the need for other tests such as angiography or echocardiography.

• Coronary angiography: This is used to visualize coronary arterial flow and disease. This is often the end point of coronary investigation and may allow treatment by stenting and angioplasty at the same time.

 

Hypertension

Hypertensive patients are at a higher risk of labile blood pressures intraoperatively compared to the non-hypertensive population. Blood pressure management is aimed to reduce cardiovascular morbidity over years and decades, but there is no evidence that perioperative blood pressure reduction affects cardiovascular risk.

For elective surgery, if mean blood pressures in primary care in the past 12 months are less than 160 mm Hg systolic and less than 100 mm Hg diastolic (160/100 mm Hg), surgery can proceed.

If there is no evidence of normotension in primary care, then elective surgery should proceed for patients if their blood pressure is less than 180 mm Hg systolic and 110 mm Hg diastolic (180/110 mm Hg) when measured in the hospital setting.

 

Heart murmurs

The valve pathology underlying murmurs may have significant implications for anaesthetic technique. Lesions that limit the cardiac output (particularly aortic stenosis) can cause profound hypotension as the heart cannot increase cardiac output to maintain blood pressure as peripheral vascular resistance drops. This is most marked with neuraxial anaesthesia and can cause morbidity due to organ hypo-perfusion. For example, coronary perfusion may become critically low resulting in an acute coronary syndrome. Echocardiography is useful to determine the nature and the severity of the valve lesion.

 

Respiratory assessment

Preoperative assessment determines the severity and potential reversibility of respiratory pathology. Disease states limit gas flow, gas exchange or both. The end point of respiratory disease is hypoxaemia and tissue hypoxia. This can precipitate organ failure with serious adverse outcomes. Common pathologies are described in the following sections.

 

Asthma

Stable asthma is usually benign, but some anaesthetic agents can trigger bronchospasm and are avoided. Conversely, some anaesthetic agents can result in bronchodilation and are favoured. Assessment should include spirometry and peak flow measurements. Preparation may include bronchodilator premedication, e.g. salbutamol, and some anaesthetists prefer a regional technique to avoid airway instrumentation and opiate use. Elective surgery should not proceed with concurrent upper respiratory tract infection.

 

Chronic obstructive airways disease

Gas flow and exchange are limited in this disease. These patients are at risk of postoperative respiratory failure due to atelectasis and segmental lung collapse causing hypoxaemia. Assessment includes spirometry (a forced expiratory volume in 1 second greater than 1 L indicates an ability to clear secretions), oximetry (and perhaps arterial blood gas sampling) and an assessment of exercise ability. A baseline chest radiograph may be useful but is by no means mandatory. An ECG may show signs of right heart strain and is also indicated as this group is likely to have co-existent cardiovascular disease. Preoperative and postoperative chest physiotherapy are essential. Anaesthetists will tend towards regional anaesthesia in patients with significant disease burden to minimise the chances of postoperative respiratory failure. Opiates are a potent source of respiratory depression and, coupled to sedation and pain, can be a powerful trigger for respiratory decompensation.

 

Respiratory tract infection

Respiratory tract infections are often viral, and the most common are located in the upper respiratory tract. Patients with a productive cough or objective symptoms of pyrexia, fatigue, myalgia and/or anorexia should only proceed if emergency surgery is indicated. The risk of laryngospasm and bronchospasm is increased. Viral myocarditis may also occur, leading to cardiac failure or even death in the perioperative period. Guidelines advise a 4- to 6-week delay for elective surgery.

 

Groups at special risk

Patients with cerebral palsy may have poor bulbar function and weak cough, which puts them at risk of aspiration, and they have a higher incidence of postoperative respiratory tract infection. This is exacerbated by any cognitive impairment that reduces their ability to cooperate with physiotherapy and interventions such as non-invasive ventilation. Patients with low-tone neuromuscular syndrome are at risk of postoperative respiratory failure, and plans will include intensive care, possible postoperative ventilation and tracheostomy requirement. Of note, volatile anaesthesia is usually avoided in this group due to the risk of rhabdomyolysis, renal failure and hyperkalaemic cardiac arrest.

 

Recommended references

Fischer HBJ, Simanski CJP. A procedure specific and systematic review and consensus recommendations for analgesia after total hip replacement. Anaesthesia. 2005;60:1189–1202.

Fischer HBJ, Simanski CJP, Sharp C et al. A procedure specific systematic review and consensus recommendations for postoperative analgesia following total knee arthroplasty. Anaesthesia. 2008;63:1105–1123.

Fowler SJ, Symons J, Sabato S et al. Epidural analgesia compared with peripheral nerve blockade after major knee surgery: A systematic review and meta-analysis of randomized trials. Br J Anaesth. 2008;100:154–164.

Goodnough LT, Shander A. Patient blood management. Anesthesiology. 2012;116(6):1367–1376.

Muñoz M, Acheson AG, Auerbach M et al. International consensus statement on the peri-operative management of anaemia and iron deficiency. Anaesthesia. 2017;72:233–247.

Simpson JC, Moonesinghe SR, Grocott MP et al. Enhanced recovery from surgery in the UK: An audit of the enhanced recovery partnership programme 2009–2012. Br J Anaesth. 2015;115(4):560–568.

Intraoperative techniques‌

Discussion of the selection and conduct of individual techniques is beyond the scope of this chapter. The technique chosen is multifactorial and is dependent upon the patient, hospital, procedure, surgeon and anaesthetist. There is little conformity of opinion.

 

General anaesthesia

This is the most common option and is entirely appropriate for most procedures, environments and patients. It is a balanced technique of analgesia, muscle relaxation and sedation. This is confirmed by data review as exemplified by recent publications concerning primary joint replacement.

 

Peripheral regional anaesthesia

This is the placement of local anaesthetic adjacent to individual nerves or plexus of nerves to produce a zone of sensory and motor block. This may be the only mode of anaesthesia. More commonly, it is a pain-relieving adjunct to general anaesthesia or sedation. The main benefit is to reduce opiate requirement to aid earlier mobilisation but neurological injury may be masked. A prolonged motor block may occur which is to the detriment of the patient. Increasingly this modality is preferred for primary arthroplasty but is increasing into other areas.

 

Neuroaxial local anaesthesia

For lower limb procedures, spinal, epidural or a combined spinal-epidural block can provide complete analgesia and motor block. As with previous techniques, they may be used alone or in combination with sedation or general anaesthesia. They are often the technique of choice in those with severe respiratory disease burden to reduce the respiratory complications associated with opiate use. Outcome evidence is poor but there is some literature base to support this practice. In addition historical data suggest a lower incidence of deep vein thrombosis and perioperative blood loss. This may no longer be valid in light of new advances in perioperative care and enhanced recovery programmes. These techniques remain an important part of a multimodal approach to fast-track surgery.

 

Contraindications

Patient refusal.

Local or systemic infection. Allergy to agents used.

Coagulopathy.

Anticoagulants (relative contraindication) increase the risk of haematoma at the site of infiltration, around nerves or in the epidural space.

Aspirin is not a contraindication.

Chronic neurological diseases (relative contraindication).

Local Anaesthesia

Some body surface procedures are amenable to surgery using local infiltration alone. Maximal dosages and drug information are given in Table 1.3.

 

Postoperative care‌

Analgesia

The “analgesic ladder” was originally published in 1986 by the World Health Organization (WHO) as a guideline for the use of drugs in the management of pain. Initially intended for the management of cancer pain, it has evolved to be more widely used for the management of all types of pain. The general principle is to start with simple analgesics and to escalate to strong opioids as required. It is advised that medications should be given at regular

 

Table 1.3 Local anaesthetic drug information

 

Drug	Maximum dose (mg/kg)	Relative Potency	Onset (minutes)	Duration (hours)
Lidocaine	3	2	5–10	1–2
Lidocaine with adrenaline (1:200 000)	7	2	5–10	2–4
Bupivicaine	2	8	10–15	3–12
Ropivicaine	3	6	10–15	3–12
Prilocaine	6	2	5–10	1–4

 

intervals so that continuous pain relief occurs, and dosing be directed by relief of pain rather than by fixed dosing guidelines.

 

Simple analgesics

These can be very effective for mild and moderate pain. Common drugs are paracetamol and non-steroidal anti-inflammatory drugs. Best effect is gained when they are given regularly, ideally after a loading dose in theatre. In more severe pain, they are still useful adjuncts with well-documented opiate-sparing properties. Increasing evidence points to using NSAIDs with care in patients with cardiovascular disease.

 

Oral opiates

Oral opiates include codeine derivatives, complex agonists such as tramadol and morphine derivatives. These are well recognised for more severe pain and can be used regularly, with stronger alternatives available for breakthrough pain. Newer formulations provide excellent pharmacokinetics with twice daily dosing of modified-release compounds, each providing 12-hour analgesia. These modified-release tablets are supplemented by short-acting versions to treat breakthrough pain.

 

Intravenous opiates

For severe pain, intravenous opiates may be given as patient-controlled analgesia (PCA). This allows the patient to titrate their own dosing. It is effective, safe and popular. Better pain scores and fewer side effects (nausea, vomiting and sedation) are regularly achieved using this modality of opiate delivery compared with intermittent intramuscular dosing. Once the acute postoperative period has passed, the patient may be stepped down to oral alternatives.

 

Alternatives

Other routes such as transdermal delivery are available. These take a long time to reach a steady plasma concentration and are similarly slow to decline when discontinued. They are more suited to long- term use in chronic pain syndromes. This inflexibility makes them difficult to use in the perioperative period but consideration should be made preoperatively to existing analgesic requirements.

 

Local anaesthesia

Local anaesthetic techniques may be continued into the postoperative period. These provide excellent analgesia with minimal side effects. However, immobility may be a problem. In units where utilising local anaesthetic blocks is embedded in practice, they are very successful and do not need to delay mobilisation.

 

Oxygen

Oxygen therapy should be given to patients with an epidural infusion which contains opiates, or those using a PCA. This supplemental oxygen maintains alveolar oxygen tension longer if respiratory depression and hypoventilation occur. Supplemental oxygen used for the first three days postoperatively can also minimise the risk of perioperative ischaemic events.

 

Any patient with pre-existing respiratory pathology or acquired (respiratory tract infection, atelectasis, thromboembolism) will be relatively hypoxic, and oxygen therapy is essential.

 

Fluid management

The goal of intravenous fluid therapy is to maintain normovolaemia. This allows adequate cardiac output and, assuming an appropriate haemoglobin concentration, tissue oxygen delivery. Maintenance water and electrolytes need to be supplied and ongoing blood loss compensated for in the form of blood substitute, or blood itself. Patient blood management has recently been advocated for the perisurgical period to enable treating physicians to have the time and tools to provide patient-centered evidenced-based care to minimise allogeneic blood transfusions. It aims to optimise erythropoiesis, minimise blood loss and manage anaemia.

Triggers for transfusion vary. Blood is expensive, immunosuppressant, associated with worse outcome and a vehicle for disease transmission. However, red cells are vital to oxygen delivery and haemostasis. The trigger will depend on the predicted continuing blood loss, the patient’s co-morbidities and symptoms. This haemoglobin concentration trigger can be as low as 7 g/dL.

 

Disposal

High-dependencycaremaybenefitmanyorthopaedic patients. Deliveryofthiswilldependon local protocol and infrastructure. Clearly, those at increased risk of organ failure or requiring a higher level of nursing supervision should be placed in an appropriate environment.

 

Enhanced recovery

Enhanced recovery is the delivery of a consistent, protocolised pathway of care with the aim to minimise perioperative stress and to expedite recovery. The amount of evidence for each individual element of the enhanced recovery bundle is variable. However, good compliance with enhanced recovery protocols (≥80% compliance) is associated with a shorter median length of stay by one day in orthopaedic surgery. In particular, individualised fluid therapy and early mobilisation were the strongest indicators. This reduction in length of stay represents a clinically important reduction in morbidity and significant cost savings.

 

Recommended references

Association of Anaesthetists of Great Britain and Ireland. The measurement of adult blood pressure and management of hypertension before elective surgery 2016. Anaesthesia. 2016;71:326–337.

Biccard BM. Relationship between the inability to climb two flights of stairs and outcome after major non-cardiac surgery: Implications for the pre-operative assessment of functional capacity. Anaesthesia. 2005;6:588–593.

Howell S, Sear J, Foex P. Hypertension, hypertensive heart disease and perioperative cardiac risk.

Br J Anaesth. 2004;92:570–583.

National Institute for Health and Care Excellence. April 2016. Routine preoperative tests for elective surgery. NICE guideline [NG45]. Accessed April 2017. https://www.nice.org.uk/guidance/ng45

 

Viva questions‌

1. In patients with hypertension, how would you determine whether elective surgery can proceed?

2. What are the contraindications to neuraxial blockade?

3. Why is a respiratory tract infection a problem?

4. Who should receive oxygen therapy in the postoperative period?

5. What are the postoperative options for analgesia for a primary arthroplasty?