Introduction
Recent advances in anaesthetic and surgical techniques, as well as continued improvements in perioperative care, have resulted in improved outcomes among patients undergoing cardiothoracic surgery. Decreased perioperative morbidity and mortality have been achieved despite the increasingly complex nature of patient cohorts. Timely and effective preoperative assessment of these patients has undoubtedly played a major part in recent progress (Weisberg et al. 2009).
Patients presenting for cardiothoracic surgery pose several challenges for healthcare staff and require a nuanced approach to perioperative care. They are usually referred to the clinic by their surgeon or via their general practitioner. The preoperative assessment clinic acts as a crucial stop (in most cases the last one prior to surgery) where anaesthetists can assess, risk stratify, and highlight complex patients who are at a high risk of experiencing perioperative complications. This process includes identification and optimisation of patient comorbidities that may increase the risk of perioperative complications, a more thorough discussion with the patient regarding the expected perioperative journey, and better resource allocation and planning of strategies aimed at reducing perioperative risk. These developments have improved the quality of care, have minimised expenses and unnecessary tests, and improved healthcare delivery (Weisberg et al. 2009).
History and evolution of the preoperative assessment clinic
The concept of preoperative assessment clinics dates back to 1949, when Dr Alfred Lee, a British anaesthetist, first realised that ‘the anaesthetist is frequently confronted with a patient, admitted from the waiting list, who is not in the best possible state for operation’ (Lee 1949, p. 169). Lee saw the need to medically optimise patients and address major health issues preoperatively, and thus recognised that it was ‘inadequate for the anaesthetist to see the patient the evening before operation, or even two or three days before…’. He proposed the very earliest version of the preoperative assessment clinic and went on to implement it in his local hospital in Southend-on-Sea.
Lee’s idea did not spread and was not re-established until the early 1990s, when Fischer and his colleagues created a comprehensive preoperative assessment clinic at Stanford University (Fischer 1996), bringing to fruition the concepts initially proposed by Lee. The preoperative assessment clinic’s goals were to increase efficiency by coordinating the contributions of various specialty consultants, integrating laboratory services and diagnostic testing, and streamlining medical record retrieval. The clinic was successful in reducing unnecessary preoperative consultations, reducing diagnostic studies by 55%, and reducing day-of-surgery cancellations by 88%.
The preoperative assessment clinic centralised all aspects of preoperative patient care and clearly improved the efficiency of patient preparation and raised patient satisfaction. However, Badner et al. (1998) recognised that many surgical candidates were relatively healthy and did not require the full preoperative assessment clinic assessment. Badner et al. (1998) described a hybrid system utilising a preoperative questionnaire to determine and screen a patient’s health status. The objective was to alleviate the strain on preoperative assessment clinic resources created by relatively healthy patients. Patients with positive questionnaires were referred to consultant anaesthetists, who then coordinated any additional assessments or tests that might be required.
This led on to the use of preoperative screening questionnaires to stratify patients as ‘fit’ or ‘unfit for surgery’. Vaghadia & Fowler (1999) used a model that utilised a questionnaire to identify patients who might require further medical assessment. Their nurse-based model for screening patients had an accuracy of 81%, a specificity of 86%, and a negative predictive value of 93% when compared with anaesthesiologists’ recommendations. Van Klei et al. (2004) further quantified the effectiveness of utilising nurses to screen patients and found that, although nurses required 80% more time than physicians to complete an assessment, the nurses and anaesthesiologists disagreed on their subsequent assessments only 1.3% of the time.
Successive modifications to the preoperative assessment clinic involved contacting patients by telephone to review their medical history, enabling them to avoid making a separate trip to the hospital for a preoperative assessment. Digner found that this system liberated resources, allowing preoperative assessment clinics ‘…to assess a greater number of patients with more complex medical and social care needs’ (Digner 2007, p. 298).
Benefits of the preoperative assessment clinic
The Australian Incident Monitoring Study found that 3.1% of adverse events resulted from inadequate or incorrect preoperative assessment (Kluger et al. 2000). By optimising patients’ health preoperatively, patient morbidity and mortality are diminished, as is the rate of operating room cancellations or delays in a variety of countries. Ferschl et al. (2005, p. 859) reported that a preoperative assessment clinic reduced operating room cancellations and delays, with resultant savings of ‘$1430–1700 per operating room’. Any estimate of the savings generated by a preoperative assessment clinic should also of course include the emotional and social costs (in terms of missed work and productivity) of cancellations to patients and their families.
The obvious question is whether eliminating or reducing preoperative testing negatively affects patient outcomes. Ferrando et al. (2005) found that the application of preoperative guidelines decreased the number of preoperative tests ordered without affecting quality of care. In fact, ‘the evidence suggests that 60–70% of preoperative testing is unnecessary when a proper history and physical are done’. Chung et al. (2009, p. 467) found that routine preoperative testing for patients scheduled for ambulatory surgery, excluding those patients with significant medical illnesses (as defined by the study’s exclusion criteria), demonstrated ‘no significant differences in the rates of perioperative adverse events’.
Prospects for the preoperative assessment clinic
The nature and set-up of pre-assessment clinics may vary between different institutions, e.g. the criteria or method used to identify which patients should be referred to the clinic, the type of provider (medical or nursing) that evaluates patients, and the design and physical location of the preoperative assessment clinic (on site at hospital, off site, or telephone- or Internet-based preoperative assessment systems). Future investigations into standardisation of preoperative testing may lead to a reduction in variation in preoperative testing practices.
There is scope for greater expansion in telephone- and internet-based preoperative assessment systems – by creating specialty centres that cover entire geographic regions, allowing savings through integration of services and economies of scale. These savings, currently unattainable due to disjointed, non-standardised preoperative assessment schemes, could then be reinvested in the healthcare system. Additionally, the prospect of integrating the preoperative assessment system with the electronic medical record may help to streamline the preoperative assessment process.
Preoperative assessment and same day admissions in cardiothoracic surgery
Historically, patients presenting for cardiothoracic surgery were usually admitted several days before the operation to allow time for the necessary preoperative assessments and investigations. In most cases, this led to unnecessary acute bed occupancy, long waiting times, time limits for evaluation, and ultimately decreased patient satisfaction. The development of, and continued improvement in, preoperative assessment programmes have naturally led some institutions to establish same day admissions in cardiothoracic surgery, with great success. This approach may not have been possible without robust outpatient preoperative evaluation (Silvay et al. 2016).
Preoperative assessment in cardiac surgery
Introduction
Patients presenting for cardiac surgery pose several challenges for healthcare staff and require a nuanced approach to perioperative care. As well as their primary cardiac disease, these patients commonly have several other comorbidities. A thorough preoperative evaluation remains an essential part of the perioperative care of this group. It allows identification of those at high risk of perioperative complications and promotes development of individualised care plans to mitigate these risks.
Pre-admission clinics
Pre-admission clinics have now become a well-established feature of most units around the country, where elective patients are assessed several weeks prior to surgery. The exact timing varies between different institutions and according to local guidelines. There are well-established benefits to this approach. Relevant investigations and imaging can be requested and reviewed with ample time before surgery; problems can be highlighted, support services alerted (e.g. transfusion), and action plans put in place to facilitate a smooth perioperative pathway and minimise delays or cancellations. It also allows an opportunity for adequate patient counselling to take place.
History and examination
In elective cases, the diagnosis is generally established by the time the patients present for their preoperative assessment. An assessment of current disease symptoms (such as angina, dyspnoea, orthopnoea, exercise tolerance and syncope) will assist in the process of perioperative risk stratification. The severity of these symptoms can also be measured against validated scores, such as the Canadian Cardiovascular Society Angina Score (Canadian Cardiovascular Society 2018) (see Table 5.1) and the New York Heart Association Classification for Functional Capacity (New York Heart Association 2017) (see Table 5.2).
This can be followed by a brief systems enquiry to exclude gastrointestinal, renal, hepatic, neurological, metabolic or haematological disease. A history of gastroesophageal reflux, hiatus hernia or swallowing problems will be especially important in airway management and risks around transoesophageal echo probe insertion. Comorbidities (such as respiratory disease, peripheral vascular disease, hypertension, diabetes mellitus, renal impairment and neurological disease) are associated with increased perioperative mortality and morbidity. Therefore, it is important to elicit details about the severity and management of these conditions.
Records of previous surgery should be scrutinised, including any adverse events or anaesthetic difficulties. Permanent pacemakers or implanted defibrillator devices should be evaluated, and a perioperative plan put in place, in cooperation with cardiac technologists. Furthermore, the patient’s religious beliefs or cultural views should be explored, as these may have major implications for perioperative care (as in the case of Jehovah’s witnesses).
Table 5.1: This table summarises the grading of angina pectoris.
(adapted from the Canadian Cardiovascular Society 2018)
| Canadian Cardiovascular Society (CCS) Grading of Angina Pectoris | |
| Class I | No limitation of usual physical activities. Angina only during strenuous or prolonged physical activity. |
| Class II | Slight limitation of ordinary physical activities. |
| Class III | Marked limitation of ordinary physical activities. |
| Class IV | Inability to perform any physical activities without angina, or, angina at rest. |
Table 5.2: This table summarises the functional classification of breathlessness.
(adapted from the New York Heart Association 2017)
| New York Heart Association Functional Classification (NYHA) | |
| Class I | Asymptomatic cardiac disease, with no limitation in ordinary physical activity. |
| Class II | Mild symptoms (mild shortness of breath and/or angina) and slight limitation during ordinary physical activities. |
| Class III | Marked limitation in physical activity due to symptoms. Comfortable only at rest. |
| Class IV | Severe limitation in physical activity. Symptomatic even at rest. |
Medications
A review of the drugs and medications list will yield information about the management of comorbidities. It is important to highlight any drugs that may interfere with coagulation (e.g. aspirin, clopidogrel, glycoprotein IIb/IIIa antagonists, thrombolytics, heparin and warfarin) and the interval since their cessation. For antiplatelet drugs, such as aspirin and clopidogrel, the usual advice is to stop taking them 7 days before surgery. This may be unwise in some circumstances, due to the pattern and severity of the coronary artery disease, in which case antiplatelets should be continued and platelet inhibition assays performed perioperatively to guide management and transfusion therapy. It is advisable to liaise directly with a specialist haematologist in such circumstances.
Current guidelines state that aspirin and clopidogrel should be continued up to the day of surgery in patients who require surgery within 6 months of insertion of a bare metal intracoronary stent, or within 12 months of drug-eluting stent. Anticoagulants such as warfarin should be stopped 3–5 days prior to surgery to allow the prothrombin time to normalise. In some circumstances, where it is critical that preoperative anticoagulation is maintained, e.g. in the presence of a mechanical valve, the patient should be admitted to hospital and therapeutic low molecular weight heparin or unfractionated intravenous heparin should be given instead. In patients with chronic atrial fibrillation, low molecular weight heparin can be provided for self-administration at home. In emergency situations, it may be helpful to liaise with a haematologist to ensure appropriate blood products and factor concentrates are available.
Newer anticoagulants such as Dabigatran (a direct thrombin inhibitor) are now being used more widely. However, these drugs can pose particular difficulties, as patients are at significant risk of perioperative bleeding and clinicians are less familiar with their use and their clinical effects. Furthermore, until recently, a reversal agent was not available. However, at the time of writing, UK authorities had approved the use of Idarucizumab as the first agent to be licensed for the reversal of the anticoagulant effect of a non-vitamin K antagonist oral anticoagulant (NICE 2016). Its action is specific against the NOAC Dabigatran. Idarucizumab is effective within minutes and can be used in an emergency. In elective surgery, NOACs are normally stopped 2–3 days before surgery (Sunkara et al. 2016).
Most other cardiac drugs, such as beta blockers, nitrates and statins, should be continued up to the day of surgery. In our institution, angiotensin converting enzyme inhibitors and angiotensin receptor blockers are stopped 1–2 days prior to surgery. However, the author recognises the controversy regarding their cessation.
Physical examination
Physical examination should focus on the cardiovascular and respiratory systems, including measurement of heart rate, arterial blood pressure and respiratory rate; characterisation of heart rhythm; palpation of carotid, femoral and peripheral pulses; and auscultation of the precordium, carotid arteries and lung fields. Assessment of dentition and oral hygiene, mouth opening, and neck movement is useful in anticipating difficulties with airway management. Furthermore, in patients with neurological disease, it is important to document the extent and severity of neurological deficits preoperatively, to act as a baseline for postoperative assessment.
Blood tests
A full blood count, coagulation studies, blood group determination, measurement of serum electrolytes, urea, creatinine and hepatic enzymes are regarded as routine in virtually all patients. The full blood count will exclude any anaemia, platelet or leucocyte quantitative abnormalities. The estimated glomerular filtration rate (eGFR) can provide more accurate assessment of renal function than creatinine levels alone. The normal eGFR in a healthy adult is 90–120ml/minute/1.73m2. Levels lower than 60 suggest at least moderate renal impairment. Chronic diuretic therapy may cause total-body sodium or potassium depletion and uraemia. Thromboelastography is quickly superseding basic laboratory coagulation tests as the investigation of choice in many institutions, as it represents a more holistic overview of the clotting cascade. Platelet assays are especially useful for assessing platelet function or indeed dysfunction in patients on antiplatelet drugs near the time of surgery.
Electrocardiogram
A preoperative baseline ECG may be abnormal in a significant proportion of patients. It may indicate previous myocardial infarction, conduction defects, cardiac arrhythmias, etc., and will be helpful in detecting any postoperative changes. Evidence of previous myocardial infarction may necessitate echocardiographic investigation to assess ventricular function prior to surgery. Some conduction defects may require temporary pacing, which can be converted into permanent pacing postoperatively. Some preoperative arrhythmias (such as atrial fibrillation) will benefit from medical optimisation in the run-up to surgery.
Chest X-ray
A plain chest X-ray provides information about the heart size, lung fields, pulmonary vasculature and bony anatomy of the chest. It is essential when assessing patients with chronic lung disease. It also provides a baseline against which to compare in the event of postoperative pulmonary complications. Furthermore, it can pick up incidental findings (such as lung masses), which may have significant implications for perioperative planning.
Exercise tolerance test
Exercise testing is occasionally used as a screening test before coronary angiography. Patients suspected of having ischaemic heart disease will undergo a standardised protocol (e.g. modified Bruce protocol) of increasing physical exercise (usually on a treadmill) with continuous ECG and blood pressure monitoring to detect signs of ischaemia and cardiac compromise. Each patient will be set a predetermined age-specific maximum heart rate. A positive test is defined by the onset of chest pain or diagnostic ECG changes, the development of hyper/hypotension, fatigue, dyspnoea, or any arrhythmias, which may indicate cardiac decompensation. The test is then terminated. Alternatively, if the patient achieves this predetermined heart rate without the onset of any of the above, the test is declared negative.
However, the test has its limitations: it cannot be performed on patients who are unable to exercise (for instance, due to musculoskeletal problems or disability); it is also difficult to interpret in patients taking beta blockers, with pacemakers, or with known left bundle branch block.
Cardiac catheterisation and coronary angiography
Cardiac catheterisation provides information regarding coronary disease, ventricular function, trans-valvular pressure gradients, pulmonary vascular resistance, and a range of intra-cardiac pressures from both right and left heart chambers. The injection of radio-opaque dye into the coronary arteries displays their anatomy and the presence and severity of disease. Direct measurement of left ventricular end-diastolic pressure provides an indirect assessment of left ventricular function. Right heart catheterisation allows measurement of pulmonary artery pressures, cardiac output, trans-pulmonary gradient and pulmonary vascular resistance.
Echocardiography
Echocardiography is helpful in assessing cardiac structure and function. It allows detailed measurement of chamber dimensions, systolic and diastolic function, valvular pathology and pressure gradients. Transthoracic echo provides a non-invasive modality useful in monitoring disease progression and assisting in determining the timing and type of surgical intervention. On the other hand, transoesophageal echo (TOE) generally provides better-quality images due to the relative proximity of the heart to the TOE probe within the oesophagus. Therefore, it is particularly useful in assessing mitral valve disease, for looking for vegetations in endocarditis, and for detecting intramural thrombi. Three-dimensional echo is now also available, potentially allowing for superior studies.
Pharmacological stress testing
In patients who are unable to exercise (e.g. due to mobility restrictions or disability), drugs such as dobutamine can be used to stress the heart while being imaged echocardiographically (stress echo). These drugs increase the metabolic demands of the heart (for example, by inducing a tachycardia), which in turn reveals regional wall motion abnormalities, indicating areas of compromised perfusion due to coronary artery disease.
An alternative approach is injecting a radionuclear substance (such as thallium or technetium) prior to stressing the heart (either conventionally through exercise or pharmacologically). The distribution of myocardial perfusion is then assessed using a gamma ray camera. Perfusion defects on images detected by the camera will correspond to territories with poor blood supply. The scan is repeated 3 hours later to check for delayed radionuclide accumulation in the ischaemic areas. This helps distinguish between reversible and non-reversible ischaemia, thus differentiating between viable myocardium and non-viable scar tissue.
Stress echocardiography is being increasingly utilised in the preoperative period in the process of risk stratification. It helps to emulate the physiological challenges to the heart brought about by surgery and can therefore reveal the true functional capacity of the heart in such conditions, as opposed to providing a snapshot assessment at rest.
Cardiac computed tomography
High-resolution cardiac CT and CT angiography can be used to provide detailed three-dimensional images of the heart, coronary arteries and the great vessels. CT angiography can also offer an alternative to coronary angiography in imaging coronary anatomy.
Cardiac magnetic resonance imaging
Cardiac anatomy, function, perfusion and tissue viability can all be examined with a high degree of accuracy using magnetic resonance imaging (MRI) without the use of ionising radiation. Intravenous dobutamine can be used to produce a stress cardiac MRI study to detect ischaemic areas, while a gadolinium contrast cardiac MRI can distinguish between viable and non-viable tissue. Furthermore, MRI angiography provides a detailed three-dimensional assessment of vessel architecture and blood flow in the cardiovascular system.
Pulmonary function tests
A considerable number of patients presenting for cardiac surgery suffer from chronic lung disease. These patients are at increased risk of developing postoperative pulmonary complications. Preoperative pulmonary function testing should therefore be carried out in all patients to assess the severity of lung disease and to anticipate difficulties in the postoperative period (Najafi, Sheikhvatan & Mortazavi 2015).
In addition, the diffusing capacity of the lungs for carbon monoxide provides information on the ability to transport gases from the alveoli to the capillaries. A DLCO of less than 70% of predicted capacity is associated with an increased risk of clinically important postoperative pulmonary complications.
Carotid doppler scans
Cerebrovascular injury is a recognised and devastating complication of cardiac surgery. Elderly patients are at particular risk and therefore carotid doppler studies are routinely performed, prior to cardiac surgery, on all patients over 65 years to rule out significant carotid atheromatous disease. In addition, carotid dopplers are performed on all patients with a history of previous stroke, transient ischaemic attacks or carotid bruits noted on physical examination. Greater than 50% stenosis is considered as significant carotid disease (da Rosa et al. 2013). Decision-making regarding the timing of cardiac vs carotid surgery then follows a multidisciplinary approach based on risk stratification, clinical context and symptomatology.
Cardiopulmonary exercise testing
Cardiopulmonary exercise testing represents an objective measurement of functional capacity. It measures the integrated response of cardiac, pulmonary and muscular systems to a progressively increasing workload. The patient exercises on a bicycle ergometer or treadmill. They are connected to an ECG and have their inspired and expired gases (oxygen uptake and carbon dioxide production) continuously measured. As exercise progresses, the patient’s energy requirements will eventually outstrip that provided by aerobic respiration and thus anaerobic respiration ensues. This results in an increase in VCO2. This point is described as the ‘anaerobic threshold’. Further increase in exercise will yield a point of maximal oxygen uptake and utilisation, the VO2 max. These parameters (anaerobic threshold and VO2 max) have been shown to have prognostic value in non-cardiac surgery (Smith et al. 2009).
Risk assessment
The production of large databases has facilitated the development of risk stratification models. Models range from very simple additive models that can be used at the bedside, to sophisticated systems involving the application of complex algorithms. The Parsonnet score and the European System for Cardiac Operative Risk Evaluation are the most widely used and have both been well validated. The latter has been further refined, and in 2011 EuroSCORE II was published (EuroSCORE Study Group 2011). However, some determinants of surgical outcomes were not incorporated in these scores, such as the surgeon’s competence, institutional expertise in handling emergencies, and financial affordability. Caution must therefore be exercised in applying these scores, especially in the context of developing countries, where the above factors vary widely between different institutions (Malik et al. 2010).
Regardless of which risk stratification model is used, higher scores tend to be associated with increased postoperative complications, increased length of stay and increased perioperative mortality.
Emergency cardiac patient preoperative assessment
Emergency cardiac surgery presents a series of unique challenges. Important information and documentation may not be available regarding the patient’s current illness and past medical history, especially if the patient is unable to provide such information. The patient may be on, or recently exposed to, anticoagulant, antiplatelet or thrombolytic drugs. They may have been transferred from a separate hospital and colonised with a resistant strain of bacteria. All the above may be in the context of cardiovascular instability or compromise, necessitating urgent surgical intervention.
In this situation, a prioritised but nonetheless structured approach to history taking, physical examination and investigations cannot be emphasised enough, so as not to miss anything of significance. Good effective communication is necessary between members of the multidisciplinary team, including cardiac surgeons, cardiologists, anaesthetists, perfusionists, theatre staff and ward staff. Adhering to published guidelines, local protocols, and perioperative checklists mitigates risk and enhances safety and the quality of care (Treadwell, Lucas & Tsou 2014).
Preoperative assessment in lung surgery
Introduction
Preoperative assessment in lung surgery is a cornerstone of the perioperative management of patients presenting for lung surgery. Preoperative assessment and optimisation of respiratory function can help minimise the incidence of postoperative pulmonary complications, a leading cause of perioperative morbidity and mortality in lung surgery (Nagarajan et al. 2011).
Major respiratory complications include atelectasis, pneumonia and particularly respiratory failure requiring prolonged mechanical ventilation. The extent of lung resection is also strongly associated with mortality, with pneumonectomy demonstrating 2–3 times higher mortality, compared to lobectomy (Ferguson et al. 2014).
The Thoracic Surgery Scoring System (Thoracoscore) (Falcoz et al. 2007) (see Table 5.3) is a well-validated tool that has proven its utility in the preoperative risk prediction for perioperative mortality. Sadly, no single test can accurately predict outcomes following lung resection surgery.
Age
There is no cut-off age at which patients are no longer eligible for lung resection. However, it is recognised that the incidence of respiratory and cardiac complications rises with age (Liu et al. 2013). The mortality rate following pneumonectomies, especially right-sided surgery, remains high (22% in patients >70 years). This is presumably due to the increased right-heart strain caused by resection of the proportionally larger vascular bed of the right lung (Spaggiari & Scanagatta 2007).
Table 5.3: This table lists the Thoracoscore factors which predict the in-hospital mortality of thoracic surgery patients
| Thoracoscore factors for predicting in-hospital mortality for patients requiring thoracic surgery |
| Age (<55, 55–65, >65 years) |
| Sex |
| ASA classification (≤2, ≥3) |
| Performance status according to Zubrod scale (≤2, ≥3) |
| Severity of dyspnoea according to Medical Research Council Scale (≤2, ≥3) |
| Priority of surgery (elective, urgent/emergency) |
| Extent of resection (pneumonectomy, other) |
| Diagnosis (malignant, benign) |
| Comorbidity score |
| ASA, American Society of Anaesthesiologists |
Chronic obstructive pulmonary disease
The most common concurrent illness in the thoracic surgical population is chronic obstructive pulmonary disease (COPD). Severity is usually classified on the basis of the FEV1 percentage, based on predicted values. The American Thoracic Society currently categorises Stage I >50% predicted, Stage II as 35–50%, and Stage III <35% (Qaseem et al. 2011).
Preoperative optimisation for patients with COPD includes pharmacological and non-pharmacological treatments. Pharmacological treatments include optimisation of bronchodilator and corticosteroid therapy to achieve adequate symptom control. Non-pharmacological treatments include smoking cessation, chest physiotherapy and pulmonary rehabilitation.
Smoking leads to impaired wound healing and an increased risk of infection, due to reduced oxygen delivery to the tissues. Pulmonary complications following lung surgery are lower in patients who did not smoke in the run-up to surgery. The length of time needed to benefit is not exactly clear. A period of 12–24 hours can reduce carboxyhaemoglobin levels, and 1–2 weeks can reduce sputum volume. A systematic review of 25 studies on the optimal timing of smoking cessation concluded that at least 4 weeks of smoking cessation are needed to reduce postoperative pulmonary wound healing complications. Less than four weeks did not appear to have any effect. Some observational studies have shown that short-term smoking cessation before surgery may paradoxically increase pulmonary complications. However, other studies have failed to replicate these findings (Lee 2015).
Comprehensive pulmonary rehabilitation programmes, involving chest physiotherapy, exercise, nutrition and education, have been shown to improve functional outcomes for COPD patients (Nici 2008). However, this is more difficult to reproduce in accelerated lung cancer pathways for surgery, due to the time limitations. There is no conclusive data on the utility of providing short intensive programmes in the lead-up to lung cancer surgery.
Right ventricular dysfunction and COPD
The state of chronic hypoxaemia among COPD patients causes right ventricular dysfunction and the subsequent progression into cor-pulmonale. Cor-pulmonale occurs in 40% of adult COPD patients with a FEV1 <1litre and in 70% with FEV1 <0.6l (Shujaat, Minkin & Eden 2007). It is now clear that mortality in COPD patients is primarily related to this condition, brought on by chronic hypoxaemia. The only therapy which has been shown to improve long-term survival and reduce right-heart strain in COPD is supplemental home oxygen therapy (Stoller et al. 2010).
Patients presenting for lung resection with a predicted postoperative (ppo) FEV1 <40% should have trans-thoracic echocardiography to assess right-heart function. Pulmonary hypertension was traditionally considered a poor prognostic factor for, or even a contraindication for, major lung resection, but evidence for this claim has been lacking. In fact, recent studies have shown that lobectomies may be performed safely in selected patients with pulmonary hypertension, with complication rates that are comparable to those experienced by patients without pulmonary hypertension (Wei et al. 2014).
Lung cancer
It is important to note that in patients presenting with a ‘resectable’ lung cancer, in which the disease is still localised, surgical resection is likely to be curative. Therefore, any anticipated benefits of further preoperative work-up must always be weighed against the risk of delaying surgery and further spread of disease.
Cardiac disease
Cardiac complications are the second most common cause of perioperative morbidity and mortality in the thoracic surgical population (Sengupta 2015). Most patients presenting for lung resection surgery have several risk factors that predispose them to coronary artery disease, such as smoking. There is a not insignificant risk of cardiac ischaemia post thoracotomy (Vretzakis et al. 2013).
In such patients, appropriate preoperative cardiac assessment should be performed, as described above. In some circumstances, these patients may benefit from further optimisation of their cardiac disease, using enhanced pharmacological treatment, coronary angioplasty and/or coronary artery bypass, prior to or at the time of lung resection.
Timing of lung resection surgery following a myocardial infarction remains controversial. Patients are at high risk of cardiac decompensation and death if subjected to the extreme physiological stresses of lung resection surgery in the immediate post-infarction period. There is some evidence to indicate that lung surgery should be delayed by 4–6 weeks after a myocardial infarction following cardiac stabilisation and optimisation (Kiran & Makhija 2009). The decision is clearly a difficult one, as the practitioner needs to find a balance between ensuring urgent cancer resection and avoiding further cardiac ischaemia and cardiovascular instability.
Prior medication (such as beta blockers, nitrates and antiplatelet agents) should be continued throughout the perioperative period. The benefits of continuing antiplatelet agents, including clopidogrel, far outweigh the risks of stopping them at the time of lung surgery. This is especially pertinent in those who have undergone coronary artery stenting following a recent myocardial infarction, in which the possibility of acute stent thrombosis will be remarkably high.
Renal dysfunction
Chronic renal failure was previously thought to be associated with higher mortality following pulmonary resection surgery, but more recent studies have refuted this (Park et al. 2015). There is evidence, however, that patients undergoing thoracic surgery may develop postoperative renal impairment. There is an independent association between postoperative renal impairment and hypertension, peripheral vascular disease, a poor preoperative estimated glomerular filtration rate, preoperative use of angiotensin II receptor blockers, intraoperative hydroxyethyl starch administration, and thoracoscopic (versus open) procedures. Development of acute kidney injury was associated with increased rates of tracheal reintubation, postoperative mechanical ventilation, and prolonged hospital length of stay. There was no increase in mortality (Ishikawa, Griesdale & Lohser 2012).
The ‘3-legged stool’
Preoperative assessment of respiratory function primarily revolves around three areas: spirometry, gas exchange and cardiopulmonary interaction. Prior to surgery, an estimate of respiratory function in all three areas should be checked in each patient. This data can then be used to plan intra- and postoperative management (Slinger 2011).
Spirometry
The most valid single test of respiratory mechanics and volumes for post-thoracotomy respiratory complications is the predicted postoperative FEV1 (ppoFEV1 %), expressed as a percentage of predicted volumes, corrected for age, sex and height. It is calculated based on the number of functioning segments of the lung to be removed:
ppoFEV1% = preoperative FEV 1% × (1 – %functional lung tissue removed/100).
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